Thought Experiments

17
Aug

Can You Really Go Back in Time by Breaking the Speed of Light?

Nothing can travel faster than the speed of light. But if it could, the conventional wisdom goes, it would travel back in time. Is the conventional wisdom right? Earlier this year, I was part of a team of researchers that decided to find out whether “superluminal” travel—that is, going faster than the speed of light—really does take you back in time.

tachometer_620
Image by Flickr user Rami, adapted under a Creative Commons license.

To find out, we imagined a souped-up spacecraft that could somehow go faster than the speed of light and sent it on an (imaginary) journey out to a distant planet and back again. We started the ship up at the speed of light—denoted in physics equations as c—then gradually hit the gas pedal, accelerating past the universal “speed limit” to see how long the trip took at various different velocities. We used only the velocity addition formula from special relativity, as the other ones (time dilation, length contraction, etc.) all gave us goofy, imaginary answers. (Also, those formulas apply to what’s going on inside of the spaceship, which is a whole other space-ball game.) We pictured what the trip would look like to an observer waiting back on Earth and watching the ship’s progress through a powerful super-telescope.

When the spaceship goes exactly at the speed of light, from the point of view of the observer back on Earth, everything appears normal as the ship speeds away. But just when the spaceship appears to reach the planet, it instantly materializes back on its landing pad on Earth, and the observer sees a huge flash of light containing an “instantaneous movie” of the spaceship’s trip back! Here’s why: imagine that it takes the ship ten years to get to the planet and ten years to get home. The light that the spaceship emits, say, five years into the journey will be seen by the Earthbound observer ten years after the ship took off, because it takes it five more years for it to get all the way back to Earth. Light the spaceship emits when it reaches the planet, ten years into its journey, makes it back to Earth twenty years after take-off. Now the ship turns around and heads home. As it gets closer to Earth, the light it emits has a shorter distance to backtrack. So, light from year 15 of the trip only has to travel for five years before it reaches the observer, 20 years after launch day. In fact, because the spaceship is “riding along” at the speed of light with the light it emits on the way back, the observer sees both the landed ship and the “movie” of its return journey, all at the same time, when it arrives back on Earth. Traveling at the speed of light, half of the journey appears to be instantaneous, but the ship hasn’t actually traveled back in time.

But what if the spaceship breaks the speed of light? Now, we are entering the purely theoretical realm of superluminal travel. The spaceship is outracing the light it emits, so when the spaceship takes off, it leaves its own light in the space-dust. At some point later, the spaceship arrives back on the landing pad, but since the light emitted closer to Earth is what the observer there will see first, the spacecraft’s journey will appear to her as a series of images retracing the ship’s journey in reverse, like a movie on rewind. Meanwhile, images from the spaceship’s outbound trip are still coming in, so the observer can see three versions of the spaceship: one image going forward towards the planet, one image heading in reverse towards the planet, and the real spaceship on the landing pad. We call this an “image pair creation event,” because the real ship is accompanied by two images.

You can think of it like mailing selfies home from long, round-trip vacation. Just as the spaceship was traveling faster than light, you are traveling faster than snail-mail, so you beat some (or all) of your mailed selfies home. The day after your homecoming, the mail carrier delivers two of your pictures: one from the trip out, and a second from your trip back. It’s a more mundane kind of image pair creation event: There are three versions of you there at the mailbox, but only one is real.

In the case of the faster-than-light spaceship, though, something very strange happens that our snail-mail analogy can’t account for: Eventually, as someone watches the two moving images, they will see them meet up and disappear at the planet at the same time in what is called an image pair annihilation event.

This is all very peculiar, but it doesn’t actually take you back in time. So, we imagined pushing the ship even faster. As the ship’s velocity increases, what the observer sees looks the same, but the reality is very different. The observer watches the spaceship leave the launch pad and head out to the planet, just as before; however, a real pair of spaceships appears on the landing pad, not simply one and an image! Then, one of the ships immediately takes off for the planet, again in reverse, and annihilates with the original ship in a real pair annihilation event at the planet.

Now, you may be wondering: Where did the extra spaceship come from? We wondered the same thing. Though our equations seem to be telling us that this second, physically-real ship should appear on the landing pad, the equations don’t give us many clues about where it came from or how it got there. Our guess is that one of the pair-created ships is made of exotic negative mass, if only to conserve the mass in the problem.

This is definitely weird and needs further research. But to achieve true backward time travel, we’ll have to go even faster!

So, we imagined nudging the ship’s velocity up once again. Finally, we pass the critical speed limit1 at which the total trip time is a negative number—we’ve gone back in time! In this scenario, a certain time before the spaceship takes off for the planet from the launch pad, a new pair of real spaceships is created on the landing pad, and one takes off toward the planet. Then, the original spaceship takes off at its normal time, and they annihilate as before at the planet. At this point, we could conjecture any time-travel related paradox imaginable, but since this post is about how we got to travel backwards in time and not time travel itself, we will leave those to the reader’s imagination.

So, simply going faster than light does not inherently lead to backwards time travel. Very specific conditions must be met—and, of course, the speed of light remains the maximum speed of anything with mass.

There is a lot more to this fascinating topic than this blog post can cover, so if you have any questions, comments, or concerns whatsoever, leave a comment, and I will do my best to address it!

1To travel backward in time, the spacecraft’s velocity must exceed:

equation1_long

where u is the velocity of the planet relative to Earth, and c is the speed of light.

Go Deeper
Picks for further reading

The Nature of Reality: Trap Doors in Time and Space: Teleportation, Time Travel, and Escape from Black Holes
Seth Lloyd, professor of quantum-mechanical engineering at MIT, investigates hypothetical methods of time travel, both forward and back.

The Open University: The Grandfather Paradox – 60-Second Adventures in Thought
A brief video introduction to the grandfather paradox and its troubling implications for backward time travel.

Relativity for the Questioning Mind
In this friendly introduction to Einstein’s special and general relativity, Oberlin College physicist Daniel Styer provides a rigorous but non-technical look at time dilation, the twin paradox, and more.

Wikipedia: The Tachyonic Antitelephone
A modest proposal for a way to send messages back in time.

Tell us what you think on Twitter, Facebook, or email.

David Russell

    David Russell is currently studying physics at Michigan Technological University, and was previously a student at Bay de Noc Community College. As a native of the Upper Peninsula of Michigan, he greatly appreciates nature from both the mathematical and human side of things. As a nerdy young adult of this generation, he enjoys video games, graphic novels, and occasionally reading.

    • Andrew Goetsch

      You left out the small fact that it would take more than infinite energy to get you superluminal, so anything derived from that would be equal nonsense. You don’t get to answer science questions by using magic.

      • Jekyl

        Sometimes that’s how you get to real answers though. Much of science (maybe all of it) started out as “magic” and “Gods” and “spirits” to our more primitive ancestors. It takes these kinds of imaginary and seemingly magical concepts to get people thinking harder about them, asking questions, experimenting and then coming to scientific conclusions that our generations now consider common sense.

      • Gary

        I am sure the writer knows that. He was just explaining what would happen if the spaceship do go faster than light.

        That said, would the same thing happen if the spaceship has the theoretical warp drive?

      • David Russell

        Andrew, you are very correct about the infinite energy. I would have included that, and a whole bunch more stuff in this post, however, having a word limit makes things get cut. If you’re interested in the slightest about our work, visit http://arxiv.org/abs/1505.07489
        This is our scientific paper about the subject. It’s under peer-review as of this moment.

    • Joe

      Time Travel and the speed of light have NOTHING WHATEVER to do with each other! The speed of light being the ultimate speed limit is nothing but an assumption. Time travel is impossible because of the very nature of what time is. All attempts to show time travel is possible are little more than figments of the imagination. About the same thing as driving your car forward and then reverse! And calling that time travel!
      But also think of this. IF you ARE traveling back in time, EVERYTHING was also so have to travel, and in a nutshell, that means your “Time Machine” will cease to exist! Plus you will get younger and younger until you NO LONGER EXIST!

      • David Russell

        Joe, I believe that you are wrong. The general knowledge in the physics community is that goofy things (like time travel) happen when objects with mass pass the speed of light. And, the speed of light in a vacuum being the universal speed limit for anything with mass is something anyone with Freshman Calculus and Freshman Physics (Mechanics) skills can prove. You might not even need Calculus.

        • Joe

          No, I don’t believe I am. Time is nothing but a measurement. NOTHING has been observed going faster than the speed of light, and doing so has nothing to do with going backward in time. Their “interpretation” of their equations, is a perfect example of how math DOES NOT represent reality. In math, for example, you can divide and divide the number one till infinity. In reality, when you reach one, that’s the end. Even when astronomers say they are looking back into time, which is the closest you will ever get to “time travel”, they really are not traveling in time, any more than you would be waiting for your wife to catch up with you on a walk! And here’s something to think about on that score. If the Universe was created by a Big Bang, the light from that event would be long gone, as “we” are traveling outward substantially slower than the light from that bang. So just what are they really seeing?

    • wayne

      I don’t much buy time travel. Says that you live you life over and over. You cant be truly dead if you can go back to a time where you existed. I don’t believe you can outrun an event. Maybe a to b faster but nothing changes say the time it took you to make the trip.

    • Time is relative, not an absolute, it can appear to slow down from an observer’s perspective and therefore probably can appear in the negative.

    • MFWIC

      Making time reverse? Not likely. That means reversing the flow of time and undoing all the actions in the universe. What kind of energy is required to make that happen? To undo all the reactions that occurred? What happens to the energy used to travel back in time? Makes a great sci-fi fairy tale. It is like bring things back to life.

      • mudmessiah1

        More energy than ever existed?

        • MFWIC

          Everything in the known universe is finite.

          • mudmessiah1

            Of course if time has only warped and not flowed then no time has passed since the Big Bang and shifting to an “earlier” time would only require accessing a point in warped time and perhaps to do that may not need energy at all.

            • Chris Stephens

              Even if time is a string traveling back in time would be possible in theory. Hell it could even be possible to change the past if you created loop backs in your thread.

            • Chris Stephens

              Tho unlikely you could change the past even if you could travel in time.

            • MFWIC

              Trying to understand how any action or reaction is possible without any energy input or transfer. Even the floating mineral dust in space carry kinetic energy with it.

      • Hexitor

        It would take 1.21 gigawatts, duh.

        • MFWIC

          Must be huge as gigawatts is nowhere to be found.

          • Rob H.

            Its about the same amount of energy in a lightning bolt.

      • rusty

        No extra energy required. If you go back in time, you just start another timeline. You cannot change the past or the future.

        • MFWIC

          If you start another timeline, than that means you are creating another whole known universe with memories of all past actions and events prior to the timeline. The more you think about it, the more absurd the notion of time travel becomes.

          • Denotsed

            Unless that universe, maybe all possible universes, already exists. In that case traveling back in time just shifts you from one to the other. No special creation for your time travel journey required.

            • MFWIC

              Well as we know it, time moves in one direction. Not sure if it is a valid theory if time was categorized as another whole dimension. Reason is, if that is true, there would be endless dimensions from the first second to the end of time.

      • Branson

        Its not a matter of traveling back in time. its a matter of speeding up to the speed at which time itself travels like running a long the side of a train that has passed in order to pace a box car and then running even faster to catch the box cars that have already passed.

    • A W

      einstein was working on electromagnetism of moving bodies and somehow it clicked on him that the speed of light was a constant, regardless of the speed of the light source. so if you are moving at speed s the speed of light you emit is still c, not s+c.

    • James Rushin

      Time is an abstract concept invented by man to allow him to reference past events. The idea of time travel is pathetic in its impossibility.

      • Watalka

        ^ This is exactly correct. There really is no such thing as time. There is only now! The perception of time comes from the relative movement of particles, the sway of the tress, the motion in the ocean, the spin of the earth, and the movement of the galaxies. If particles never moved, we would not experience time.

        • Earl Gates

          That would mean if you travel faster than light to Alpha Centauri and return, since you are no longer bound or influenced by the time on Earth, you will arrive in the fast event scenario. If you travel twice the speed of light in 2016 and back to Earth at the same speed, You will find yourself in the year 504 A.D.or pehaps 8064 A.D. in the future.

          • Watalka

            Alpha Centauri is appx 4 light years from Earth (measured in Earth years). If you traveled at twice the speed of light it would therefore take 2 Earth years to get there. If you immediately turned around and came back at the same speed, you would arrive at Earth 4 years after you originally left Earth, and everyone would’ve aged 4 years equally. You, for whom the trip took 4 years, and the people left on Earth, for whom your trip took 4 years. Simple math. 2+2=4

    • Javed Mohamed

      What would happen if the earth spins in reverse on its axis?

      • Watalka

        We’d need to redesign all our toilets, that’s for certain.

      • Earl Gates

        Superman will be able to save Lois Lane which he did. Joke!

    • Torsh Johansen

      From the observer, no time elapses when going the speed of light. Therefore, he can’t “wait 2 minutes, then turn the ship around”. It goes until it smacks into something, with no time elapsing for him. I guess if his “ship” went to the outer edge of a black hole where space was warped, and he swung around it, and came back, there would be no time elapsed if he went insta-speed-of-light from pressing the on-button. But everyone would be 20 years older.

      So it’s not just mass going the speed of light that is the problem, but be able to slow down, as time doesn’t exist when going the speed of light.

      • Watalka

        Yikes! The speed of light and the perception of so called “time” have nothing to do with one another.

    • Kenneth Elmore

      Sure there is something faster than light example: say you want to send a light signal to a planet 100 light years away or you have the ability to transfer thought to same planet the thought would travel instantly as in now, light would not, it would have to move through space through physical stuff that are in space.

      • Earl Gates

        Photons will collide with many particles present in the vacuum of space and will be affected also by the gravity and cosmic radiations but our thoughts seems have the capability to tunnel into something or be transmitted in a wormhole like path free of gravity, dark matter, cosmic radiation and elemental particles that scientist don’t know until now.

    • Dewed

      I guess PBS sometimes means Pure B S.

    • Guido Quando

      While something with mass can’t travel faster than light (FTL), information seems like it can.

      Via Entanglement, two particles, (A and B) become linked. Then using a pokey slow spaceship (at 10% the speed of light – okay, still silly fast, but potentially feasible), we take particle B far away (like Alpha Centari, 4 Light years out…taking 40 years to get there). Once our ship is safely arrived, we alter the state of “A” (on Earth), and our counterpart particle B is “immediately” updated with that information, by-passing that annoying speed limit (what Einstein called, “Spooky Action at a Distance”).

      From the observer on our spaceship looking via a telescope towards the Earth, any information they see via the telescope will be 4 years old compared to that of information provided by our entangled particle “B” receiving “instantaneous updates” from entangled particle “A”. However, this is the inverse, and making information appear into the Future versus the past. (if I’m thinking about this correctly).

      Is there any way to make information (something without mass) appear to be from the Past using Entanglement?

      • David Russell

        I’m far from an expert on quantum entanglement, but what I do know is that entangled information is nearly instantaneously transmitted (which is really cool), and that getting even a pair of particles to stay entangled over any sort of distance is extremely hard. It gets even harder when more than 2 particles are entangled. So, for a quantum walkie-talkie to work, we’d need to entangle astronomically large amounts of particles (10^23 or so), and keep them perfectly entangled for a long time.

        P.S: I love your profile picture. Praise be to the FSM.

    • 20pizzapies

      Particle pairs exchange information [ according to Quantum Entanglement and recent experiments ] several thousand times faster than the speed of light . But anything with Mass greater than the negligible mass of say a photon , can not . BUT then there is The Arrow of Time which is ONE-DIRECTIONAL . Allowing the hypothetical however , if one were to travel at super luminal speed , one could catch up to light emitted by one’s past ,overtake it , and possibly venture into “a future ” .However since all that is, including ourselves, are products of our past , we could not effect anything besides our future, which would still be a result of the One Directional Arrow of Time . So no one can return to the past although hypothetically overtaking the light of the past .
      Einstein didn’t call Quantum Entanglement ” Spooky ” for nothing .

    • Ted Stanwood

      “Time” as we think of it of course does not exist. There is only now. Even light coming from a distant star arrives now, not in the past. Are we looking at that light as if what is happening there is now?
      Of course not.
      All time is, is a perception of now, and once now has passed, it no longer exists.

      • BrianFraser

        Einstein believed that time was just a useful illusion, and that time does not “really exist”. Indeed, modern physicists are trying to get rid of the concept of time as a FUNDAMENTAL concept.

        In physics equations, time is usually parametric. In quantum mechanics, for instance, it is treated as a parameter, NOT as an observable. In other equations, time is paired up with space: E=mc^2 and E = cB are two fundamental examples (the latter referring to electric and magnetic fields). For these reasons, physicists are now thinking that MOTION is fundamental, NOT space or time separately.

        If that proves to be true, our view of the Universe is really screwed up!

    • Uhsen Li

      everyone who said you can’t travel speed of light because of einstein’s e=mc2.
      1) that is JUST a theory, it’s not proven yet
      2) a lot of scientist are proven wrong
      3) they used to think earth used to be flat, and all planets were revolving around earth for over 200 years.

      but some how everyone’s dead set on that E=MC^2 is the answer to all life in general.

      • David Russell

        First, I haven’t seen anyone post about E=mc^2. And, wrong formula from the wrong theory of Einstein. E=mc^2 is the mass-energy conservation equation. It simply states that there is an amount of energy within any sort of mass, and that energy can be turned into mass. Mass turning into energy is how nuclear weapons work and why they are so dangerous.

        And second, “JUST a theory” is literally the worst thing that any sort of scientist ever hears; worse than nails on a chalkboard. A scientific theory is calculated, peer-reviewed, and subject to multiple rounds of experimental verification. If a single hole is found in a hypothesis, it is stays a hypothesis. If it is verified within its respective community, then it is considered a theory. A theory is a highly polished idea of how the universe works, and is considered to be the currently closest approximation to the truth that the scientific community has found as of yet.

        • dave geiger

          Mr Russel,

          Would you please provide a response email address to admin@iwyfy.com. I have a few questions pertaining to both quantum randomness and entanglement. My name is David Geiger and i have done an exercise in Indiana that has come under scrutiny of both military and state officials.

          Thank you.

        • BrianFraser

          Re-arrange E = mc^2 so it is in the non-local form: E/(1/c)^1 = m/((1/c))^3. This form of the equation says A LOT (!) and you can even derive Newton’s law of gravitation from it (except that there will be no need of G).

          As for what can travel faster than light, consider this:

          “The most amazing thing I was taught as a graduate student of celestial mechanics at Yale in the 1960s was that all gravitational interactions between bodies in all dynamical systems had to be taken as instantaneous. . . . Indeed, as astronomers we were taught to calculate orbits using instantaneous forces; then extract the position of some body along its orbit at a time of interest, and calculate where that position would appear as seen from Earth by allowing for the finite propagation speed of light from there to here. . . . That was the required procedure to get the correct answers.” (“The Speed of Gravity – What the Experiments Say” , Tom Van Flandern, Physics Letters A, 250 (1-3) (1998) pp. 1-11)

          Another one is:

          “Measurement of the Speed of Gravity” by Yin Zhu . The Abstract from Appendix B, in part, says: “It indicates that the gravitational force of the Sun acting on the satellite is from the present position of the Sun [i.e., no aberration] and that the speed of the gravitational force is much larger than the speed of light in a vacuum.

          Einstein’s Special and General Relativity theories are LOCAL physics theories. They work fine for reference system effects, but fall apart when addressing NON-LOCAL physics.

          • David Russell

            That is absolutely fantastic! Thank you for the information.

        • David Eddy

          David,
          What bothers me is that E=mc2 does not include the non-physical intelligence that causes consistent results.

    • thousanth disquss ID

      The speed of light as compared to WHAT? The stationary warehouse walls at the edge of the universe? If you reach a velocity diferential from Earth of the speed of light, maybe Earth will go back in time. Or Vaporize. Yup. How do you prove who’s moving and who’s still? You see the joke of this? I don’t want to hear about relativity from the days of walking and horseback. Thank You. next.

    • grmpy

      I don’t think the observer would be able to see anything until the ship slowed back down to less than the speed of light. The only reason we are able to see anything is because light bounces off it which makes things viewable to us. If the ship is going faster than the speed of light, wouldn’t that suggest that it’s it’s going too fast for light to bounce off of it thereby rendering it invisible? Even more, perhaps black holes aren’t holes at all but particles in space spinning faster than the speed of light. spinning so it creates a vortex that sucks everything in and then that stuff also travels at the speed of light which means you still can’t see the center but would explain why the black holes grow and solve the “matter is destroyed in the black hole” argument. It’s not destroyed, it’s now just spinning faster than the speed of light and is therefore unviewable. Just my Pop/junk science ideas. 🙂

      • David Russell

        You may have a very good point about the fact that we wouldn’t be able to “see” the spaceship.

        However, for the black hole thing, I don’t think your vortex hypothesis is quite on the right track. And, it is physically impossible for something to go faster than light, according to every hypothesis and theory anyone has ever worked out. It would take infinite energy, and therefore, an infinite force to make anything even reach the speed of light.

        The black hole is simply a region of space of very high mass, such that the velocity needed to get out of that region is higher than the speed of light, that’s why it’s black.

        • grmpy

          Thank you for the acknowledgement on not seeing the spaceship. 🙂

          As far as nothing traveling faster than the speed of light.. I understand. but we are stumbling on new particles and matter/antimatter, it seems, almost everyday. Perhaps some exotic material as not yet “seen” (har har), ’cause they travel faster than the speed of light and haven’t been seen yet 😉 could have no problem moving faster than…

          In all seriousness, though, I understand there is some evidence for faster than light travel. I can’t remember what they’re called but if the rest of my memory serves there are two particles that rotate in opposites from each other and if you reverse the direction of one then the other one automatically reverses. it doesn’t matter how far apart they are from each other they will always stay in perfect sync. Apparently it’s been worked out in the math that even at distances light years apart still switch instantaneously. so the speculation is faster than light travel or proof of wormholes,

          • David Russell

            The particles that travel faster than light all the time (theoretically) are called Tachyons, and the “opposite rotation” phenomena is called quantum entanglement. And, yes, entanglement between two particles does allow nearly instantaneous information exchange, but it takes a considerable amount of energy and effort to get things entangled and keep them entangled. This problem greatly intensifies when more than 2 particles are involved.

            • grmpy

              Thank you for the knowledge, and also for not being rude to my “clearly uneducated in the field of physics and astronomy,” self.
              I wish everyone in this field was as polite and patient as you.
              Take care

          • David Eddy

            Gumpy,
            Speed is zero to infinity. The speed of light like the speed of sound is whatever speed it is going just like anything else. Speed is a manmade invention that is non-physical; it is an effect not a cause. Propellant is a cause.

            • grmpy

              By that definition any amount of speed should be possible given the right propellant. I don’t think that jibes with the speed of sound rules

    • Tiredofallthenonsense

      Given that time isn’t a constant, how can the speed of light be a constant?

      • David Russell

        The speed of light is a constant to any non-accelerating observer. So, if we’re heading in a straight line (even opposite directions), or standing still, the speed of light is the same for both you and I. However, if one of us is accelerating (turning, rotating, slowing down, or speeding up), then the speed of light may differ. By how much, I don’t know, as I’ve yet to study General Relativity.

      • Sheng Zha

        Check this video clip from Vsauce on youtube. https://youtu.be/ACUuFg9Y9dY?t=182

        • bernard Wozny

          Didn’t watch the video but yes headlights would work at the speed of light.
          According to relativity, time dilates according to the point of reference.
          At light speed, time is zero (or infinitely close to zero) so it will take an infinite amount of time for the light to move away from the headlights. It doesn’t matter because if you were there (driving the car at the speed of light) it would take an infinite amount of time for you to see it move away.
          This is why black holes do not emit light – because the escape velocity of the object – aka black hole – is equal to or greater than light speed. It would take an infinite amount of time to see the light.

          • Sheng Zha

            Bernard, I referenced that video because I think it has decent depiction on how speed of light could be a constant while time isn’t.

            Back to the comment, I think you’re right. One thing that’s probably worth clarifying is that if I were the driver of the car traveling at the speed of light, in my frame of reference the light would still leave me instantaneously and travel at the speed of light. However it will take an infinite amount of time to be observed by an observer that’s in ANOTHER frame of reference which isn’t traveling with me, if our frames of reference differ by the speed of light.

            And lastly, although indeed in the Newtonian view (inferred from the term “escape velocity”) black hole would be completely black, black hole would in (quantum) theory (and likely in reality) still emit some light due to quantum tunneling.

    • Bil Paul

      One photon is traveling east at the speed of light. Another photon passes it at the speed of light traveling west. That means that relative to each other, they are traveling at twice the speed of light ……..

    • Vic

      Ouch, that hurt my head reading it!

      Well, I believe it is not possible.

      Time is a temporal and a not physical dimension of space-time!

      Time is a measure of the progress of existence. It is forward-directional only. Existence is an event that starts and ends and cannot be reversed; neither the measure of its progress, that is time

      You can only reverse the effect of an event but not the event itself. Once an event occurs, time is the measure of its progress, and it can not be taken back.

      You can reverse the effect of an event by creating another event that negates it. Both events would have taken place and cannot be taken back, yet their effects canceled out each other like nothing happened.

      • Ale Mori

        It is possible but men won’t see it. ..the cibereptiles that our descendants would become.. ..maybe. ..nah. not according to last election .

    • Javed Mohamed

      What about time on other planets like Mars & Jupiter?

    • Rage Nln

      Awesome read! Get’s the gears turning.

    • Billy Antony

      Using a telescope to look at objects 50 million light years from ourselves . Is visual time travel. 🙂

    • T_Rat

      I think the author forgot to “carry the one” or move the decimal point. For the ship to return, no matter what its speed, it must first take off. So two real ships cannot exist on the launch pad at the same time. If the ship traveled to a planet 1 light year away at a speed that is, for example, 365 x C, the trip would take one day (on Earth) and the return trip would take another day, so the ship would return 2 days after having left. No matter how much faster the ships goes, the distance out and back together is 2x a one way trip. No matter how fast the ship goes the whole trip will always be 2 x some number, which itself must always be added to time zero. So it is never a negative number. Certainly the time when the image is seen relative to the real ship’s return is another matter since it is constrained by C.

      • Xerxes

        The point is that, at a certain point past light speed, you would go back in time at a rate greater than the time taken for the trip out and back again. So if it takes you 6 hours to go there & back, but you slide backwards in time by 7 hours, you would get home 1 hour before you left.

        Personally, I find it much more likely that either it’s just plain impossible to exceed light speed (which would be quite disappointing, because it’s still “just” a speed), or there’s an as-yet undiscovered error in the formulas.

      • David Russell

        As we found out in our equations, the return trip is where the goofy time traveling occurred. Here is the paper that Dr. Robert Nemiroff and I did, with the full mathematical details describing how the equations work and how we got our conclusions. Xerxes is correct, in both of his paragraphs.

        http://arxiv.org/abs/1505.07489

        • T_Rat

          In the link you posted, the author gives velocity relative to earth a negative number because it is “returning” to earth. That negative for velocity is an acceptable use for defining LOCATION in space (end vs start of the trip) but not TIME or DISTANCE. from T zero.
          Furthermore, to consider backward time travel possible, one would have to reverse all the entropy changes of the universe which would take nearly all the energy of the universe for that period of time and transmit that energy throughout the universe, or consider “time” a local event so that all the universe’s entropy changes did not have considered.
          Of course, mastering and transmitting all that energy universally can not be done. As far as the local time possibility, if you are moving at or beyond the speed of light, there is no “local” at all.
          So, the topic is just a something for a few intoxicated grad students to giggle about.

    • mudmessiah1

      At the quantum level gravity is at a minimum and spacetime becomes flexible..hmm?

    • disqus_lRhQeYrsS2

      It was so much easier in Star Trek . . .

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      WHY THE SPEED OF LIGHT IS “C”
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      There is a high tension string particle field in space (not the string theory type).
      A good 2-D model would be something like a spiders web.
      Now imagine an infinite 3-D spiders web. If a vibration was set off in it, it would travel forever and the speed the vibrations travel (through the net) is the speed of light (that’s actually what light is, a vibration traveling through a string particle field)
      The speed vibrations travel through the particle field is the speed of light “c”

      The particle field strings have a certain amount of tension, length and mass. That makes ‘c’ the speed it is. If the tension, length or mass changed so would ‘c’

      Here is a regular string tension formula…

      Tension = velocity squared x mass / Length.

      If we plug c in and rearrange we get…
      TL = mc^2

      Both sides of the equation are in joules or energy… equivalent to “E”.
      It means the Tension of the strings in space times their length is equal to their energy.

      This is why the speed of light is involved in Einsteins mass energy equivalence equation…

      E = mc^2

      and actually why light travels at the speed of light…
      I always wondered why… now I know.
      It had to be something mechanical… tension and string lengths!

      So, you can arrive at Einsteins famous formula from completely different directions.
      You can think energy is contained in mass and released.

      E = mc^2

      Or you can think there is a particle field of strings and mass is inert, the energy is only potential… released (actually pulled) by tension on the strings.

      TL = mc^2

      They are equivalent. Which is correct? You do not know.

      • Vic

        How do you explain the speed of light being constant in vacuum?

        • Is the tension, length or mass changing in a vacuum?

          If you read the comment you would know that already.

          • Vic

            Actually, what I meant is how do you explain that light still propagates in vacuum when you propose there is a high tension string particle field in space? Unless, of course, you consider vacuum to be just that.

            • What does the vacuum of space mean to you? Completely void of any material substance? No one believes that. Even mainstream incorrectly thinks there is a Higgs field, a gravitational field, electromagnetic field, etc.

              They think there are 5 or 6 “fields” all occupying the exact same space. Think about it. That can’t work with only 2 different fields.

            • Vic

              Good question. To me, it means no field, but nobody knows.

              The Higgs Field, which is hypothesized to manifest in the form of bosons—hence the infamous Higgs Boson Particle, aka the God Particle—when it interacts with other particles and thus giving them mass, is only Theoretical Physics but not proven science. And so goes the rest, especially “Ether,” which was ruled out long time ago.

            • Oh… so you actually agree with Michelson-Morley?

              Why did you say you pick “b”?
              b) Test if there is a medium.

              Please go here…

              http://www.pbs.org/wgbh/nova/blogs/physics/2015/08/can-you-really-go-back-in-time-by-breaking-the-speed-of-light/#comment-2200055945

              …and let everyone know you pick “a”
              a) Test if the Earth is rushing through the medium.

            • Vic

              I pick b as the test’s objective but not the result.

            • Coool… so even if someone does something completely and obviously incorrect you will still believe in it. You are not alone!

            • Vic

              Not exactly!

              I can’t control the outcome of any test with a certain objective, I just read into it. Science establishes that space is simply vacuum, if something else is proven, then that what I would adopt.

            • Stop being an imbecile. MM is how they established it.

              But we already went over this…
              No one believes space is a vacuum. Even mainstream incorrectly thinks there is a Higgs field, a gravitational field, electromagnetic field, etc.

              You are looping.

    • ben cruz

      As of now, one can travel faster than the speed of light only in the imagination.
      A couple of years ago, CERN thought that in one of their experiments with neutrinos, they exceeded the speed of light. But they were eventually proven wrong.

    • ray4ausa

      Anything and everything is possible WITH THE RIGHT INGREDIENTS AND PARAMETERS. The universe BEFORE LIGHT was faster at expanding than light has expanded SINCE it’s origination. The act of producing photons takes speed away from dark energy. We will never “see” dark energy because we cannot see OUTSIDE the electromagnetic spectrum. Our senses cannot phantom the idea of infinity or what infinity really means. As I sit here writing this there is a possibility of ME doing this same thing countless times in countless worlds with countless deviations. Either we live in a finite world where everything is definite and will have an end at sometime, OR WE WILL LIVE FOREVER IN SOME FORM SOMEWHERE. We will never see either.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      THE GENIUS OF MICHELSON-MORLEY
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      Do you pick a or b?

      If you were going to test if there is a medium for the conveyance of light, would you…

      a) Test if the Earth is rushing through the medium.
      b) Test if there is a medium.

      Michelson-Morley “confirmed” there is no medium with their experiment.
      Michelson-Morley picked “a” and everything you think you know is based on that. (it’s another pillar of modern science)
      Here is your chance to agree with those great men and pick “a”, everything you think you know is based on that.

      NOTE: The correct answer is of course “b” but modern physics is based on MM experiment and they picked “a”, Good luck everyone!

    • Chris Stephens

      I have never researched into the thoughts on accepted views regarding time travel. From reading this I take it that the commonly accepted theory is that if you could travel fast enough… you could return before you left? or even before they seen you leave?

      • David Russell

        The “common knowledge” in the physics community is that as soon as a massive object passes the speed of light, it will begin to go backwards in time. Dr. Robert Nemiroff and I tried to verify where that “common knowledge” came from, and this is what we came up with.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      THE SUN IS THE SAME IN A RELATIVE WAY

      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      This is interesting… if you could put everything back the way it was in the past, has time itself also reverted to that period? That would mean “time” is just the way things are arranged.

      If I had a time machine, I (just myself) could travel back to 1947 and drive out to Roswell in a 1947 Chevy and see what really crashed there.

      But what if I use the time machine and transferred the whole planet back to 1947? It would leave the planet exactly as it is now but in universal time it is 1947. I could still drive to Roswell in a modern car and the UFO crash would still happen because it originated from off-world.

      Taking this one step further… I transfer the whole Universe back to 1947.
      Everything is exactly the way it is now but Universal time is 1947. Now the crash does not happen. Even though it is actually 1947… the arrangement of stuff in the entire Universe is 2015

      • Budong

        If just you traveled back to 1947 wouldn’t the earth be somewhere else?

      • Vic

        Physical “change” is inherent in this existence and time is a virtual measure of it and not the cause of it. So, going back in time, so to speak, will not undo the physical changes during that period, it just undoes the virtual measurement.

        • This means different people have different definitions of what happens during time travel.
          Like the “Universe.” Some think it is an endless unbounded void, Others think it is a sphere of a certain size, etc.

    • Fallout

      Hum, a negative mass spaceship appearing at the spaceport seems problematic when it interacts with real mass. It would reason that the paring of negative mass with actual mass would cause an annihilation of mass thereby diminishing the total mass of the universe and then speeding up–ever so slightly–the contraction of the universe, if that will happen in the WAY off future of the universe.

    • Edward N Haas

      For thousands of years — and whether among philosophers or scientists or what-have-you — one of the most widely and staunchly defended convictions has been and still is this: Without a GEOMETRICAL model of the Universe — and particularly a geometrical model of SPACE & locomotion — it is IMPOSSIBLE to explain how objects can be separate from, and move around among, one another. Watch now how that age old, sacrosanct dogma is annihilated by an ALGEBRAIC model of the Universe and of space and locomotion in particular.

      As the logic of the mirror & key to an ALGEBRAIC model of the Universe, Esoptrics (from the Greek for mirror), is the only theory explaining what no GEOMETRTICAL model can, namely: how even space itself as well as its occupants and their every act of locomotion are ultimately (i.e.: at c. 10^-47 cm.) a collection of non-spatial points outside of one another in a septuplex (say “7 fold”, if you prefer,) framework (Say “grid” or “field”, if you prefer.) of real relations. That framework results because each point is a COMPOSITE state of excitation — actual as particles & potential as
      space’s & locomotion’s ultimate points — logically divisible into 6 COMPONENT states having a unique set of real relations to one another and, thereby, giving to their composite state a unique set of real relations to each and every one of all the other composite states in the Universe. How so?!

      The 6 component states (Their origin is not a topic for here.) are logically divisible into 3 sets each of 2 mirrored images of one another and labeled by Esoptrics as: (A vs. B), (A’ vs. C), and (B’ vs. C’). The Universe’s every ultimate OCCUPANT (vs. CONSTITUENT) is called a duo-combo, since each consists of a BALANCED composite state of excitation (labeled a piggyback form) forever logically concentric with an UNbalanced composite state (labeled a carrying generator). Every form is a balanced state because, every time it performs a particular composite state, each of its 6 component states has the same one level of intensity out of the currently available 2^256 (1.158×10^77) integral levels of intensity (x, 2x, 3x, 4x, etc. called levels of ontological distance & OD for short).

      For example, a form operating at OD4 may — at a maximum rate of once per 7.2×10^-96 sec. in the terms of sensation dependent minds (This indivisible chunk of time is called an alphakronon & K for short.) — switch back and forth from the 2 phases of a cycle in which: PHASE #1 = for some value of K, its composite state’s 6 component states are: (4A + 4B) + (4A’ + 4C) + (4B’ + 4C’); PHASE #2 = for that same value of K, its component states are: (8A + 8B) + (8A’ + 8C) + (8B’ + 8C’). While in Phase #1, it offers 512 (i.e.: the cube of 2×4) potential, unbalanced composite states of excitation (Say “indivisible chunks of space”, if you prefer.) to the carrying generator of any duo-combo whose piggyback form is currently operating at an OD below OD4.

      The way these 512 states are related to one another can, as a teaching aid, be METAPHORICALLY expressed as a large cube composed of 512 smaller cubes equal to one another in size and the 6 sides of the large cube labeled A opposite B, A’ opposite C, and B’ opposite C’. Among those 512, one can select, for example’s sake, 4 logically sequential unbalanced composite states describable so: START: (.25A – 0B) + (.25A’ – 0C) + (.25B’ – 0C’); NEXT: (.5A – .25B) + (.25A’ – 0C) + (.25B’
      – 0C’); NEXT: (.75A – .5B) + (.25A’ – 0C) + (.25B’ – 0C’); NEXT: (A – .75B) + (.25A’ – 0C) + (.25B’ – 0C’).

      Locomotion is thus a case of a generator, for some value of K, performing one unbalanced composite state of excitation and then switching instantaneously to performing, for some value of K, a logically sequential unbalanced composite state thereby carrying with its center the center of its own piggyback form and that form’s ultimate “chunks of space”. In other words, by means of its carrying generator, one duo-combo’s “space envelope” (i.e.: its piggyback form) is moving around in a second duo-combo’s “space envelope”, and a smaller “area of space” in moving around within the confines of a larger “area of space”.

      Note that, in the above logical sequence, the ontological quantum of change is 1/4. That’s the mirrored image of 4/1 — the current OD of the form providing the 512 indivisible chunks of so-called “space” but more accurately labeled “unbalanced composite states of excitation”. In phase 2 of the cycle, the form offers (2×8)^3 = 42,496 potential composite states of excitation. Here, of course, “potential” does not mean a mere abstraction. For, what underlies the potential unbalanced states is the actuality of the providing form’s balanced composite state of excitation. Each
      potential state is thus potential only from the standpoint of the 1 or more generators able to transform it.

      Esoptrics, then, is, as a group of words & numbers, OBSERVABLE, EMPIRICAL,
      INCONTROVERTIBLE PROOF of the erroneousness of the age old, sacrosanct dogma stated at the start of this. For, Esoptrics clearly and unequivocally presents
      to the world, in several words & numbers, an OBSERVABLE, EMPIRICAL, INCONTROVERTIBLE, MATHEMATICALLY PRECISE & GRAPHIC ILLUSTRATION of exactly how an ALGEBRAIC model of the Universe — and particularly an algebraic model of locomotion & so-called “SPACE” — explains the way a septuplex framework of real relations (i.e.: sextuplex at 2^256 OD levels) allows both objects, and the ultimate parts of their acts of locomotion and the medium thereof, to be separate from, and to move around among, one another. No matter how much Esoptrics fails to predict anything, it MOST MANIFESTLY DESTROYS FOREVER the monumentally beloved prejudice dogmatically decreeing ONLY a GEOMETICAL model of the cosmos, space, and locomotion can POSSIBLY explain separation and locomotion.
      EDWARD N. HAAS (79) – HAASWOOD, LA

      • Jeff

        Good lord – if you ran this by Lawrence Krauss he would die laughing!

        • Please stop being a nasty imbecile.

          p.s. It’s easy to tell from the things you write (like “Oh gawd”, ” quibble”, “cliche”, “airy-fairy-newey-agey”, etc.) that you are gay but you also write nasty stuff to others.
          It’s like you are trying to “come out” on this site but also need to fight it?
          Please find somewhere else to “come out.”

    • Jeff

      I have my usual quibble with the “nothing can travel faster than light” cliche. It is badly stated, first because it implies that something can travel *as fast as* light, and second it leaves out the essential fact that this statement only applies to objects with mass.
      A correct way to put this is to say “Nothing with mass can travel as fast as light!”

        • Jeff

          If you mean Michelson-Morley, just say so instead of relying on initials which could mean anything. Your question is nonsense.

          • “What the hell is MM? i have a degree in astrophysics, by the way, so I really hope you’re not trying to bs me with some airy-fairy-newey-agey crap here.”

            Just answer the question

            • Jeff

              You are not worth the time to answer.

            • Stop being an imbecile. You wrote nasty stuff on all my comments and that takes time so you contradicted yourself over and over… even now.

            • Jeff

              Stop being a brain-dead idiot!

      • Vic

        I totally agree. I shared the same exact line that nothing with mass can travel at the speed of light and that photons are massless on many other forums before.

          • Vic

            My answer is b, I would test if there is a medium.

            • Correct. But modern physics is based on “a.”

              That other guy is even throwing a tantrum to avoid answering. (if he gives the correct answer it means everything he knows is wrong)

            • dging

              I don’t t think it’s true that nothing can travel faster than light or that nothing with mass can travel faster than light. Einstein’s equation only say that nothing with mass can travel at the speed of light. If something with mass can get from traveling slower than the speed of light to faster than light, w/o ever, even for a plank moment, traveling at the speed of light, then as it accelerated even faster than light, it’s mass would fall. But the problem is, how can something get from going slower than light to faster than light, w/o ever traveling at the speed of light? And of course, something with mass can never travel at the speed of light, because then it’s mass would be infinite.

          • Jonnan

            Your question over there:
            Should you –
            a) Test if the Earth is rushing through the medium.
            b) Test if there is a medium.
            Assumes there is a meaningful distinction between A & B.

            Sorry, but since the earth *is* moving, unless you are positing that the medium is moving at the same rate and vector as the planet at all times, Michaelson Morley is going to have the exact same result.

            Since that would generate completely different results from relativity, fairly comfortable with the interpretation of Michaelson Morley that the speed of light is strangely independent of the reference frame and there is no aether.

            But thanks for playing, here’s your box of Rice-a-roni, the San Francisco treat.

            • Yes Mr pompous, you are smart. Just ignore any other possible reasons (movement, drag, 2 or 3 other things I thought of).
              Completely ridiculous and unfathomable

              Yes the Earth is moving. And the whole solar system is swirling around the Milky-Way. And the whole milky-way is galaxy is flying through the Universe at enormous speed. Everything they did was completely wrong and NOT thought out (same way you do things).

              I guess I need another answer.
              a) Test if the Earth is rushing through the medium.
              b) Test if there is a medium.
              c) Ignore everything and just agree with MM

            • Jonnan

              Gotta love how someone claiming one of the most brilliantly simple physics experiments of all time is completely wrong is accusing me of pomposity – {G}. Ah well, I’ll live with the pain.

              More seriously, what you need is a prediction that you think will differ from the Michaelson Morley prediction – making a grand statement about your brilliance and how stupid they were doesn’t cut it. Now, if you come up with that, you’ve got a case.

              But just whipping out an assertion that they did everything wrong and you’ve brilliantly deduced that the Universe simple produces the exact same results predicted by Relativity despite the fact that if Michaelson Morley is wrong so is Einstein . . . with no support other than you can come up with an esoteric way of asking two questions, both of which were addressed by the original experiment?

              Yeah. To me, that seems pretty pompous.

            • Jonnan

              Now, I should say, I found your comment about the relationship between the E=mc^2 and the tension equation very insightful – not a relationship I’ve ever seen noticed before, and it seems interesting. But I don’t think it’s possible to jump from that to an assumption of a medium – too much countervailing evidence et al.

              But it’s definitely something I want to look into.

            • Oink Oink

              Einstein believed there was an Ether.
              http://www.tuhh.de/rzt/rzt/it/Ether.html

              So did Newton and Tesla.

              I will go along with them instead of Michelson Morley and you!

              Newton also thought it was responsible for gravity.
              Is the Earth speeding through gravity? You are a nut.

            • Jonnan

              Yeah, that’s not really ‘Aether’ in the Michelson-Morley sense although I can see where Einstein might use the word there. As may be, the ‘Aether’ of a fixed space time that matter and light move through in a matrix, where moving in one direction would make light moving in that direction have a different relative velocity was conclusively killed by Michelson-Morley.

              That is by the way *definitely* the ‘Aether’ Newton believed in. He’s one of the giants but if he were omniscient there would be no need to stand on his shoulder would there?

            • Budong

              I like this idea. Can you forget about Michelson-Morley and the Ether for a moment and just answer the question?

              If you were going to test if there is a medium for the conveyance of light, would you…

              a) Test if the Earth is rushing through the medium.
              b) Test if there is a medium.

              Remember, just answer the question, thanks

            • Jonnan

              No I won’t ‘Just Answer the Question, thanks’. The question has enormous buried assumptions – How are you going to distinguish the answers, what are the predictions of a medium the Earth is somehow ‘not’ rushing through et al.

              Unless you can actually show
              A – how you are going to distinguish these and
              B – that the distinction is not one that would be noted by the Michelson-Morley experiment,
              it’s not actually a meaningful question – it’s just an attempt to look like a subtle genius by rearranging the wording.

      • Scott

        “Nothing with mass can travel as fast as light” In a vacuum.
        Cherenkov radiation occurs when a charged particle moves through a medium faster than light can move in that medium.

        • Jeff

          You are forgetting that it’s the wave front that slows down, not the photons themselves. In between getting absorbed and re-emitted (actually destroyed and re-created) they travel at c in the space between the atoms.

    • Rayu Johnson

      There is never any time travel involved, the only thing you are seeing is the delayed photons. From the observers on the second planet it is even more weird. You will see a spaceship appear out of thin air, split into two as they leave the ground, and recombine on their journey back to the first planet. (It is easy to visualize when you see it in 4 dimensions then you get a stretched out doughnut shaped object — the ship — and strings extending off of it in every direction (the photons) and know which ones will be seen first and when)

      As for the occupants, they would see something far more bazaar. As they leave the planet time would seem to be running backwards and shifted red, while the planet they head towards would be shifted blue and time would be moving much more quickly. After landing, they would see an identical ship take off in the direction they came from flying backwards. When the original ship finally leaves the second planet, this planet now shifts red and time moves backwards. The first planet then is shifted blue and time moves rapidly on its surface. The other ship would become very elongated and split in two as you approach the midpoint of your journey. After you land on the planet, the ghost ship that fallowed you disappears, and another one emerges out in the distance mirroring your flight backwards and recombines with the third ship in the distance as they land on the other planet.

    • Robert Murch

      So those imaginary numbers are important. Take a look on youtube there is a video that shows how time travel works and you don’t need to go faster than the speed of light to make it happen. A simple increase in velocity is sufficient. The video involves an airplane and a few atomic clocks.

    • Gary Richardson

      Unlikely. I lean towards increased speed affecting sub-atomic forces in ways we don’t yet understand. Seems more likely to approach closer to zero time without ever reaching it completely.

    • Coach Jones

      Time exists because there is motion. Absolute stagnation eliminates time. Space can exist without time but time cannot exist without space. The unifier is motion. There can be no motion without gravity. There can be no matter without gravity, there can be no gravity without matter, there can be no motion without matter.

    • Jus_Wonderin

      My head hurts.

    • Stanley OBrien

      I think that if an object or objects go faster than ‘C’ a dimensional shift will, 1st cause the observer in our 4 dimension to see the ship vanish, unless a tool is created to track and view objects existing in a new virtual dimension called C+1 . C is the speed limit, so when you break the rule observed/established in our 4 dimensions you force a new set of rules, I’m calling the door C+1 or C1 . The New rules that govern ‘C1’, numbers and symbols would need to established so you can translate C1 to C = < . Again, I think, the ship would vanish and re appear based on a door (this is imaginary) that opens when you pass our C . Passing C allows you to jump into a forced dimensional bubble I'm calling C1. In and out of that door you would travel as you speed up and slow down. As I understand advanced technologies, Passing C is possible but you would/must have a field to block and establish the bubble. This is critical. Technology needs to be built to keep the 4 dimensional ship intact when it travels as 'C1' this is so it can maintain it's essence and shapes. I think we think of this as force-fields… Without advanced force-fields all matter will be reconstructed (destroyed when it returned to C) when it reached C1. We wouldn't see it destroyed until the ship reduced to C from C1.

      Just think'n, Stan

      • What are ” force-fields” made from?

      • Vic

        According to Einstein’s Theory of General Relativity, nothing can travel faster than the speed of light. Science also shows that photons, which are the particles side of light—light has a Wave-Particle Duality behavior, are massless; therefore, nothing with mass can even travel at the speed of light either.

        Now, experiments have shown that “quantum entanglement” exists, and that observing/measuring an entangled-particle “instantly” determines the outcome of the other, no matter how far apart they are. That can only mean that that speed is a “non-local” effect.

        That said, nothing can “locally” travel faster than the speed of light (c) at all nor can anything with baryonic mass “locally” travel at up to the speed of light while remaining “local.”

        • Jonnan

          Strictly speaking I believe it says nothing can *accelerate* past the speed of light (or indeed decelerate past the speed of light were it already going above it), a technicality that feeds all science fiction FTL drives anywhere.

          Of course you get nicely i-involved answers when you deal with that, but one of the more interesting ramifications (If I remember my Asimov) is you get the same answers from the other side – If you are already going faster than light, to *you* you appear to be going below the speed of light and objects in our reference frame would appear to be going faster than light.

          • Vic

            Actually, it is about speed, since the speed of light is constant, hence, acceleration is zero.

            Meanwhile, funny you should ask, I intended to include above that all physical matter can only accelerate to a certain extent; otherwise, it would destruct.

            p.s. This textbox kept on hanging forever for some reason, good grief!

            • Jonnan

              Not really. The equations work mathematically in excess of light speed (Thus the blog post), you just get strange results like imaginary mass and negative time frames which have no intuitive real world interpretation.

              You can’t *accelerate* to (or thus past) light speed because your mass increases, and thus the energy required to accelerate increases, going to infinity as you approach c. But it has nothing to do with matter ‘destructing’ or anything.

            • Vic

              I totally understand that, things got entangled here.

              What I meant is that the speed of light “itself” is constant in terms of speed (besides in terms of refractive indices of materials,) I believe light emits at full speed “c” where |v0|=|vf|=c and acceleration a=0.

              On a separate note, concerning acceleration, I am referring to that baryonic mass can only tolerate acceleration so much, aka g-force tolerance; therefore, it would take forever to accelerate mass to anything close to the speed of light and would destruct beyond the g-force tolerance.

            • Jonnan

              I confess I suspected you were speaking from an engineering standpoint, but it wasn’t clear enough that I was going to speak for you. Even so you can get away with quite a lot with very low acceleration if need be.

              But in all honesty I was mostly just wanting to get the Asimov thing out there – that from the perspective of the Tachyonic universe the Tardyonic one is the one moving faster than light.

              I find that duality interesting, in the same way that the ‘rolled up’ dimensions in string theory aren’t rolled up from their internal perspective – from there, our universe exists in tightly wound dimensions.

    • bernard Wozny

      You haven’t explained completely the annihilation event – or at least not to my understanding. Do the space craft (or particles) annihilate each other (themselves) or what exactly happens??

    • Jonnan

      where u is the velocity of the planet relative to Earth, and c is the speed of light.
      I presume ‘planet’ was intended to be ‘spacecraft’ here?
      That said, I’m not getting the equation here or how you use that to determine the speed required to go back in time;
      Assuming the spacecraft is going warp 1, (c^2)/u +(c(c^2/u^2 -1)^(1/2))
      the left component simplified to c and the right to 0, so c, but I don’t know what I’ve calculated or how that determines the craft does/does not go back in time?

    • Vic

      I read many times that it is quite a challenge to define time in the simplest terms.

      I came up with this:

      “Time is the quantity of duration of existence.”

      In that sense, you can’t go back in existence.

      BTW, Isaac Newton believed that if everything in this existence stopped, time still passes.

      • David Eddy

        More than likely Vic,
        Time does not exist; it is a human thought that is non-physical and assigned numbers that are none physically existent in order to measure how long it took to get from point A to point B. These non-physical distances vary because of speed travelled and how direct the route. Reality is both non-physical like mathematics and physical like trees and us humans.
        Physical reality and non-physical reality is a binary system that makes reality possible. Binary systems are a very common event that is vital to a functional reality.

        • grmpy

          Time does exist. The numbers assigned to time are man made but time itself does exist. Without time movement is impossible

          • Do you have your own theory?
            How about a link to it?

            • grmpy

              Do you mean idea? Yeah, I have my own idea based on what little bit of physics I know. It’s not published but they are plenty of pages that will tell you time is real, backed by physicists.

            • David Eddy

              If you want to expand the meaning of the word real as all inclusive, then why not? The only problem is that fiction would also be real because it is real fiction which should be an oxymoron. Life does get complicated! Language is
              no simple matter.

          • David Eddy

            Time does not exist in the physical sense like a rock. Time is a concept term that is used as a place holder for a period of time that is not a physical entity. I am trying to get people to understand the difference between what is physical and what is an occurrence or belief. Definition of terms is essential to comprehension. Time is fleeting but you never see it fly. Time is just a measurement of change in a particular space.

          • David Eddy

            Time does not exist in the physical sense like a rock. Time is a concept term that is used as a place holder for a period of time that is not a physical entity. I am trying to get people to understand the difference between what is physical and what is an occurrence or belief. Definition of terms is essential to comprehension. Time is fleeting but you never see it fly. Time is just a measurement of change in a particular space.

            • grmpy

              Time is a concept term that is used as a place holder for a period of time….
              You just defined time as time. Way to go. It doesn’t have to held in your hand to be real. Occurrence and belief are not necessarily the same things. Often they are not. Time is real whether you can hold it or not.

            • David Eddy

              Gravity is real too but it cannot be held in your hand. Gravity is a function of repulsion and attraction. The more attractive you are the more gravity you get. The less attractive you are the more repulsion you get.
              The moon is attracted to the earth and it is also repulsed by
              thrust. The moon is in a position where these forces are
              equal. Any help with this thought is much appreciated.

            • David Eddy

              Gravity
              is real too but it cannot be held in your hand. Gravity is a function of
              repulsion and attraction. The more attractive you are the more gravity
              you get. The less attractive you are the more repulsion you get.
              The moon is attracted to the earth and it is also repulsed by
              thrust. The moon is in a position where these forces are
              equal. Any help with this thought is much appreciated.

            • David Eddy

              it all depends on the use of the word real. it can be considered real time or not real time. The use of words can get complicated! Language is no simple matter.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      TIRED OF LYING IN THE SUNSHINE

      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      There are actually two different types of time.

      1) Ultimate Time: If you removed all matter and energy (all particles) from the universe and were left with only an observer (for instance Einstein) and his pocket watch… would time still exist?
      Yes… that is ultimate time in a null universe. This would be unchangeable constant flow.

      2) Field Time: As soon as you step back into the what Einstein calls 4-D space-time (FPT field with tension on it) everything is completely regulated by the field tension. This is completely variable.

      The field tension is the universal cosmic speedometer.

      If the tension goes up… gravity goes up, and so does the speed of light and everything else with it.
      That includes any type of measuring device and the speed your brain is working.

      Increase or decrease tension and it changes everything along with it, that’s all electro-magnetic phenomena, vibrations… everything.

      It’s like being a character in a movie and you don’t know the speed the projector is running… fast, slow, stop, start… you don’t know.

      Net effect: you might not notice anything.

      But if you could remove yourself from the projector, take a step away from everything and take a look back, you would see the speed everything is happening.
      If the tension has been changing over billions and billions of years… this would be readily visible as red-shifted light.

      I’m talking about something completely independent from everything.

      Like H. George Wells sitting in the time machine.
      Anything Einstein said or proved is completely irrelevant to George.
      George can see things happening at all kinds of different speeds… and everyone else is completely unaware of it.
      The same thing can be happening without a time machine.

      There is no way to know the speed things are really happening.
      If everything is happening very slowly so is the way the brain sees it.

      You have to think a level or two deeper to understand and most people can’t.

      There was an episode of STV with a planet with fast time. The inhabitants of the planet were completely unaware they were moving so fast. Same thing is true for anyone / everything… there is no way to know your true speed (unless someone / something comes along with different speed… but you still won’t know the true speed… you will only know your speed is different than someone else’s.
      For true speed you have to remove yourself from everything (the field), take a look back and hope there is a noticeable change in speed in the field time (or figure out how to negate the field time your body might still be using).

      3) Planck Time? (this might take a while)
      “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” — Max Planck

      • David Eddy

        There is only space which is non-physical
        where everything happens in three dimensions. Particles in space provide
        physical reality. Particles continuously
        form and reform providing change within space in a forward
        continuum. Time is a non-physical measurement of this change which can be
        entropy or construction. Energy is
        what fuels physical reality.

    • rusty

      Suppose the ship leaves and has no intention of returning? Then suspect we just have another timeline.

    • james

      if the speed of light is the constant and time is changed by the speed of travel… I disagree… if speed changed time then how do you measure speed…. to measure speed you need time… … you need time and distance to measure speed time never changes speed does

    • Bee

      David, please read my blogpost http://backreaction.blogspot.com/2015/06/does-faster-than-light-travel-lead-to.html

      I have explained there why the conclusion in the paper is wrong. You only arrive at this result if you neglect entropy increase. Faster than light motion, even if it was possible, would never lead you back in time – this would require an engine that violates the 2nd law of thermodynamics.

      • Robert Nemiroff

        David and I read your good article soon after you posted it. Our calculation says that a closed FTL loop could originate with a spaceship pair existing at an earlier time. You are correct that the calculation does not say how any spaceship perceives the arrow of time. It could be that all participants agree on the same entropic arrow. Whether one then considers this backward time travel is then a matter of definition. It still seems so to me.

        • Bee

          Robert – But this is the main point. How can you even say you’re ‘going back in time’ if you don’t know which way you keep memory or age? As I said earlier, the pair creation makes perfect sense – but on a level of particles, not on a macroscopic level.

          • Robert Nemiroff

            Bee – How objects in the calculation perceive time passing was not tracked. The object pair appears at an earlier time, and to me that means backward time travel. Rules such as entropic arrows of time and chronology protection conjectures may be entirely reasonable and may take the calculation (further) outside the realm of believability. But the raw calculation, as presented, says the object pair appears in the past.

            Although the paper used the term “spaceship”, it really only considered point particles. No physical extent was included. The spaceship theme was used as a visualization tool. You are the first to point out to us that this macroscopic / microscopic distinction might be significant. You may be right that this could only work, in practice, for microscopic particles.

            I find it interesting to consider the calculation as a straightforward extension of the twin paradox to superluminal speeds. Subluminal twins must return in the future. Superluminal twins may return in the future — but at some speed a transition occurs where the past becomes involved. But this transition is strange — objects don’t so much “return” in the past but rather “appear” in the past as part of a pair.

            Although outside the realm of the calculation, one fanciful interpretation with macroscopic objects is that instead of moving backward in time and perceiving entropy to decrease, one twin suddenly appears back in time, as part of a pair, and then moves forward through time normally, always perceiving entropy to increase.

            • Jonnan

              I confess I’ve always had an intuitive reaction that the ‘backward in time’ results meant that quantum interaction started again, but being random resulted in entropy increasing again – e.g. ‘time’ thinks it’s backwards, but the actual measurement of time being dependent on Entropy would continue forward.

              But laymen like myself applying intuition to quantum mechanics is a classic way to find out how ignorant you really are – . Ah – the classics!

              Although that *would* be one of the few ways I kind think of to debunk the Bohm interpretation, but my (again, laymans) understanding of things is that that is sufficiently debunked by the Bell Theorem.

            • Yes Mr pompous, you definitely are a laymen. You proved it in the other comment.
              Don’t trust your intuitions.
              p.s. Has anyone else ever called you pompous?

            • David Eddy

              Because the particle building blocks on the microscopic scale are constructing the macrostructure of the macroscopic scale it must be true that they are travelling in the same direction in the time continuum.
              There would be both entropy of macroscopic structure and building of macroscopic structure in separate space in the universe at various rates of time that would be travelling forward in the time/space continuum.

            • Vic

              Very thoughtful and keen of Bee to bring that up, indeed.

              Quantum Physics/Mechanics, though “theoretical,” suggests that “superposition” is only possible at the microscopic but not the macroscopic scale, and it does not know where the “transition” between the quantum and the classical scales happens. There might be a lot of hidden knowledge in that transition that could impact any theoretical time travel calculations.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      THE GENIUS OF MICHELSON-MORLEY
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      Do you pick a or b?

      If you were going to test if there is a medium for the conveyance of light, would you…

      a) Test if the Earth is rushing through the medium.
      b) Test if there is a medium.

      Michelson-Morley “confirmed” there is no medium with their experiment.
      Michelson-Morley picked “a” and everything you think you know is based on that. (it’s another pillar of modern science)
      Here is your chance to agree with those great men and pick “a”, everything you think you know is based on that.

      NOTE: The correct answer is of course “b” but modern physics is based on MM experiment and they picked “a”, Good luck everyone!

      • Someone else wrote this…
        “The Michelson Morley experiments were made to attempt to detect Aether Drag.” — Nope, they tested if the Earth is rushing through an ether (medium) NOT if there is one period. They have successfully derailed modern physics.

        If the medium is being dragged they are completely in the dark about it.

      • Some nut in the comments below thinks the Michelson–Morley experiment was involved with relativity, NOPE!.

        It was performed over the spring and summer of 1887
        https://en.wikipedia.org/?title=Michelson%E2%80%93Morley_experiment

        Einstein was 8 years old at that time…
        http://www.pbs.org/wgbh/nova/einstein/timeline/

        But, if it were done correctly (“b”) it could be used as a reference for any theory. There are 4 possibilities…

        1) Theory with medium >> MM confirms medium == Correct
        2) Theory without medium >> MM confirms medium == False
        3) Theory with medium >> MM disproves medium == False
        4) Theory without medium >> MM disproves medium == Correct

        NOTE FOR MENTALLY CHALLENGED: MM was NOT done correctly so none of this matters. Except that modern physics is based on MM experiment and they picked “a”, Good luck with that!

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      ENERGY CANNOT BE OUT ON ITS OWN
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      Everyone has the wrong idea of what energy, forces and fields are.
      Energy is a particle vibration or movement.
      You cannot have energy without a mass, energy is mass vibrating.
      Energy cannot be out on its own. (a supposed mass-less particle is a particle nonetheless, but there are no mass-less particles, so that’s irrelevant)

      Same thing goes for forces.
      A force is a group of particles arranged in a field pulling each other… and all of the particles absolutely have to be physically connected.

      A force (a group of connected particles) can only push very short distances and in rare circumstances like same pole magnets.

      But the point is… a force has to have particles involved.
      A force cannot be out on its own.

      Most of mainstream physics is a misconception.

      There is no such thing as pure energy.
      Again… Energy is a vibration on a particle (or particle movement).

      Can energy be converted into mass?
      Ummm… no, energy already has mass involved, it is a particle vibration or movement. There is no pure energy and you are not going to convert energy into mass.

      Think of a guitar string. If you pluck it… that is the energy. If you remove the guitar string from the scenario… can you still have the energy? No, of course not.

      Can you convert the guitar string vibration into mass? No… that is ridiculous.

      Look at what everything really is…

      Dimensions and units…
      mass = [M] = kilograms
      length = [L] = meters
      time = [T] = seconds
      frequency = [T^-1] = seconds ^-1
      speed = [L] / [T] …… = m/s
      acceleration = [L] / [T^2] …. = m / s^2
      momentum = [M] [L] / [T] … = kg_m / s
      force = [M] [L] / [T^2] . = kg_m / s^2
      energy = [M] [L^2] / [T^2] = kg_m^2 / s^2
      power = [M] [L^2] / [T^3] = kg_m^2 / s^3

      Notice mass [M] is not equal to energy [M] [L^2] / [T^2] …the vibration is missing

      Here is what Einsteins famous equation really looks like…

      [M] [L^2] / [T^2] = [M] [L^2] / [T^2]

      Energy already is a mass times speed^2.

      If you could just lop-off parts of an equation and claim whatever is left is equal… i.e. “energy equals mass” then you could also say that “power equals mass” and so does momentum and force. It is really stupid to think like that.
      Speed is NOT equal to length. Speed is equal to length divided by time.
      Energy is NOT equal to mass. Energy is equal to mass times speed squared.

    • JKellogg

      “They’ve gone to plaid, Sir!”

    • Bil Paul

      At one time it was thought to be impossible to fly faster than the speed of sound.

    • Bil Paul

      What is it that “sets” the speed of light? Why is it at the speed it is? Why couldn’t it have been a different speed? I have never understood why the speed of light plays a role in E=MC squared.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~
      WHY THE SPEED OF LIGHT IS “C”
      ~~~~~~~~~~~~~~~~~~~~~~~~~~

      There is a high tension string particle field in space (not the string theory type).
      A good 2-D model would be something like a spiders web (individual string lengths are approximately one Ångström).
      Now imagine an infinite 3-D spiders web. If a vibration was set off in it, it would travel forever and the speed the vibrations travel (through the net) is the speed of light (that’s actually what light is, a vibration traveling through a string particle field)
      The speed vibrations travel through the particle field is the speed of light “c”

      The particle field strings have a certain amount of tension, length and mass. That makes ‘c’ the speed it is. If the tension, length or mass changed so would ‘c’

      Here is a regular string tension formula…

      Tension = velocity squared x mass / Length.

      If we plug c in and rearrange we get…
      TL = mc^2

      Both sides of the equation are in joules or energy… equivalent to “E”.
      It means the Tension of the strings in space times their length is equal to their energy.

      This is why the speed of light is involved in Einsteins mass energy equivalence equation…

      E = mc^2

      and actually why light travels at the speed of light…
      I always wondered why… now I know.
      It had to be something mechanical… tension and string lengths!

      So, you can arrive at Einsteins famous formula from completely different directions.
      You can think energy is contained in mass and released.

      E = mc^2

      Or you can think there is a particle field of strings and mass is inert, the energy is only potential… released (actually pulled) by tension on the strings.

      TL = mc^2

      They are equivalent. Which is correct? You do not know.

      NOTE: if you think MM is correct go here and pick “a”
      http://www.pbs.org/wgbh/nova/blogs/physics/2015/08/can-you-really-go-back-in-time-by-breaking-the-speed-of-light/#comment-2203917027

    • DeAnn GroovinandJammin

      universal time is not the same as earth time… so it’s really all relative 🙂

      • I also think there are different types of time..
        http://www.pbs.org/wgbh/nova/blogs/physics/2015/08/can-you-really-go-back-in-time-by-breaking-the-speed-of-light/#comment-2202005933
        What is your idea of Universal time? This is really interesting to me.

      • Billy Antony

        Time is a man made instrument. Time is only useful as a way of organizing our puny lifespan,and the puny lifespan of humanity.

        • David Eddy

          There is daylight saving time and daylight losing time. You can save time and you can lose time. Tomorrow is today tomorrow.
          some times the faster you go the be hinder you get because everything is travelling faster than you are travelling.
          We are all going around in many circles as we walk straight ahead.
          While spending time everything is changing constantly for the better or worse.

    • utopian websurfer

      Greetings earthlings- this message is being sent to you from the past, which will be read by you the reader, residing somewhere in the future, including many others further down
      a linear timeline. at the time you read this message it will be your current present time & place in future earth. all done using a flux capacitor driven 3 giga watt cray super computer,
      Complete with an autonomous a.i. computer brain mother board using ultra fast opto electronics inside of a pure hydrogen gas environment that levitates in zero gravity, complete with a perpetual motion electrical generator that can generate vast amounts of unlimited perpetual electrical energy. some of you will receieve this message from an alternate universe existing in a concurrent alternate timeline in a sideways transmission via the ultranet.
      nuff said.- utopiian websurfer.
      p.s. you can always be an internet timetraveler. as the internet
      is purely electronic and perpetual in its existence for all eternity. all you have to do is just turn yourself into an electronic signal and email yourself either back or forward in time via gmail then turn yourself back out of an electronic signal back into a solid body human being. easy peasy jeezy lou-eazy.

      • Lavanite Johnson

        Ummm… so your saying there’s a fucking way to go back in time. B/c I watched a lot shows and movies. And ignored all my friends and made a lot of mistakes. As ik we all make a lot of mistakes as i wish i can just wake up from this terrible nightmare. B/c i am at the point where i am dying as my brothers/mother and friends are yelling at me like they have common sense.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~
      WHY THE SPEED OF LIGHT IS “C”
      ~~~~~~~~~~~~~~~~~~~~~~~~~~

      There is a high tension string particle field in space (not the string theory type).
      A good 2-D model would be something like a spiders web (individual string lengths are approximately one Ångström).
      Now imagine an infinite 3-D spiders web. If a vibration was set off in it, it would travel forever and the speed the vibrations travel (through the net) is the speed of light (that’s actually what light is, a vibration traveling through a string particle field)
      The speed vibrations travel through the particle field is the speed of light “c”

      The particle field strings have a certain amount of tension, length and mass. That makes ‘c’ the speed it is. If the tension, length or mass changed so would ‘c’

      Here is a regular string tension formula…

      Tension = velocity squared x mass / Length.

      If we plug c in and rearrange we get…
      TL = mc^2

      Both sides of the equation are in joules or energy… equivalent to “E”.
      It means the Tension of the strings in space times their length is equal to their energy.

      This is why the speed of light is involved in Einsteins mass energy equivalence equation…

      E = mc^2

      and actually why light travels at the speed of light…
      I always wondered why… now I know.
      It had to be something mechanical… tension and string lengths!

      So, you can arrive at Einsteins famous formula from completely different directions.
      You can think energy is contained in mass and released.

      E = mc^2

      Or you can think there is a particle field of strings and mass is inert, the energy is only potential… released (actually pulled) by tension on the strings.

      TL = mc^2

      They are equivalent. Which is correct? You do not know.

    • David Eddy

      Sorry folks,

      Physical reality does not work going backwards. Physical reality consists of particles
      that come together and come apart just like LEGOs to provide the change that
      makes the continuous change of physical reality possible. Absolute zero
      is when reality does not change. There is nothing to go back to because
      it is all something else. The process is that a tree is a tree until it
      is boards and no longer exists as a tree. New trees grow and provide us
      with more boards. You might want to get on board with this fact of
      reality.

    • srtdan

      I think the past can only be observed, not changed or physically traveled to. Everything we feel and see is the past. Just like the sunlight which starts out 8 minutes in the past.

    • C. M. Vijay

      Speed of Light was determined by
      measuring the speed of a Laser beam. Laser beam gets off from a two-dimensional
      flat surface of a narrow cylindrical tube, but light of celestial sources like
      the Sun – emanates from a three-dimensional spherical surface. Moreover, Laser
      light travels in the form of a beam – retaining the same intensity; whereas,
      light emanated from the spherical Sun expands – concurrently decreasing the
      intensity. The Amount of Expansion of Sunlight and its Intensity are perfectly
      synchronized with each other. There are much more dissimilarity between a Laser
      light and the Sunlight. Therefore, the speed of light cannot be decided by
      measuring the speed of a laser beam. In reality, Light of celestial sources
      contacts an object at an unimaginable speed. Please visit the article: “Reconciliation
      of the discrepancies in the speed of Light” in IJIRD Journal.

    • ~~~~~~~~~~~~~~~~~~~~~~~~~~
      WHY THE SPEED OF LIGHT IS “C”
      ~~~~~~~~~~~~~~~~~~~~~~~~~~

      There is a high tension string particle field in space (not the string theory type).
      A good 2-D model would be something like a spiders web (individual string lengths are approximately one Ångström).
      Now imagine an infinite 3-D spiders web. If a vibration was set off in it, it would travel forever and the speed the vibrations travel (through the net) is the speed of light (that’s actually what light is, a vibration traveling through a string particle field)
      The speed vibrations travel through the particle field is the speed of light “c”

      The particle field strings have a certain amount of tension, length and mass. That makes ‘c’ the speed it is. If the tension, length or mass changed so would ‘c’

      Here is a regular string tension formula…

      Tension = velocity squared x mass / Length.

      If we plug c in and rearrange we get…
      TL = mc^2

      Both sides of the equation are in joules or energy… equivalent to “E”.
      It means the Tension of the strings in space times their length is equal to their energy.

      This is why the speed of light is involved in Einsteins mass energy equivalence equation…

      E = mc^2

      and actually why light travels at the speed of light…
      I always wondered why… now I know.
      It had to be something mechanical… tension and string lengths!

      So, you can arrive at Einsteins famous formula from completely different directions.
      You can think energy is contained in mass and released.

      E = mc^2

      Or you can think there is a particle field of strings and mass is inert, the energy is only potential… released (actually pulled) by tension on the strings.

      TL = mc^2

      They are equivalent. Which is correct? You do not know.

    • sun

      according to the above equation we should travel at speed of 5999999985km/s