Thought Experiments


There Is No Now

Excerpted with permission from The Island of Knowledge: The Limits of Science and the Search for Meaning by Marcelo Gleiser. Available from Basic Books, a member of The Perseus Books Group. Copyright © 2014.

What goes on when you see something, say, this book you are reading? Leaving aside the whole business of how the brain processes visual information, let’s just focus on the information travel time. To make life simple, let’s also just consider the classical propagation of light, ignoring for now how atoms absorb and reemit light. Light is bouncing around the room because either the window is open or the lamp is on, or both. This bouncing light hits the surface of the book, and some of it is absorbed, while some is reflected outwards in different directions. The page and the ink used for printing absorb and emit light in different ways, and these differences are encoded in the reflected light. A fraction of this reflected light then travels from the book to your eyes, and thanks to the brain’s wondrous ability to decode sensorial information, you see the words on the book’s page.

Credit: Flickr/Alex Harries, adapted under a Creative Commons license.

It all looks instantaneous to you. You say, “I’m reading this word now.” In reality, you aren’t. Since light travels at a finite speed, it takes time for it to bounce from the book to your eye. When you see a word, you are seeing it as it looked some time in the past. To be precise, if you are holding the book at one foot from your eye, the light travel time from the book to your eye is about one nanosecond, or one billionth of a second. The same with every object you see or person you talk to. Take a look around. You may think that you are seeing all these objects at once, or “now,” even if they are at different distances from you. But you really aren’t, as light bouncing from each one of them will take a different time to catch your eye. The brain integrates the different sources of visual information, and since the differences in arrival time are much smaller than what your eyes can discern and your brain process, you don’t see a difference. The “present”—the sum total of the sensorial input we say is happening “now”—is nothing but a convincing illusion.

Even if nerve impulses propagate fast along nerve fibers, their traveling times are still much slower than the speed of light. Although there are variations for different types of nerves and for different people, the speed is around 60 feet per second. That is, nerve impulses travel about 1 foot in sixteen milliseconds. (A millisecond is one thousandth of a second.) For comparison, light travels 2,980 miles in the same amount of time, a little more than the driving distance from New York to San Diego.

Here is an imaginary experiment that illustrates the implication of these time differences. Imagine two lights programmed to flash simultaneously every second. One of the lights is fixed at 10 yards from an observer, and the other can be moved away on a straight rail. Imagine separating them by increasing distances as they flash together every second. An observer will start perceiving a difference in the flashing times when the distance between the two lights is larger than about 2,980 miles. Since we can’t see this far, our perception of the simultaneous now seems very credible for huge separations. An alternative, and more realistic, experiment could be set up to test this theory: have two lights flashing at slightly different times, and check when observers notice a difference. If my conjecture is correct, observers will start to notice differences when the timing interval is larger than about twenty milliseconds or so. This timescale sets the limit of visual simultaneity in humans.

The arguments above lead to a startling conclusion: the present exists because our brain blurs reality. To put it another way, a hypothetical brain endowed with ultrafast visual perception would catch the difference between the two flashing lights much earlier. For this brain, “now” would be a much narrower experience, distinctive from the human “now.” So in addition to Einstein’s relativity of simultaneity involving two or more moving observers, there is also a relativity of simultaneity at the cognitive level resulting from the subjective perception of simultaneity or “now” for the individual or, more generally, for every kind of brain or apparatus capable of detecting light.

Each one of us is an island of perception. Just as when we look out into the ocean and call the line where water and sky meet the horizon—a limit to how far we see—our perceptual horizons comprise all the phenomena that our brains compute as happening simultaneously even if they are not: the perceptual horizon delineates the boundary of our “sphere of now.” Since light is the fastest speed in Nature, that’s the one I’m using to define our sphere of now. (Had we used the speed of sound, of only 1,126 feet per second in dry air and at 68 degrees Fahrenheit, the sphere of now would have a much smaller radius. Two lightning strikes miles apart look simultaneous but wouldn’t sound simultaneous.)

To summarize: given that the speed of light is fast but finite, information from any object takes time to hit us, even if the time is tiny. We never see something as it is “now.” However, the brain takes time to process information and can’t distinguish (or time-order) two events that happen sufficiently close to one another. The fact that we see many things happening now is an illusion, a blurring of time perception. Since no brain is the same, every person will have their own limits of time perception and their own sphere of now. In fact, every brain, be it biological or mechanical (light-sensitive detecting device), has a different processing time and will have its own sphere of now; each one will have a distinctive perception of reality. From current neurocognitive experiments, it seems reasonable to suppose that on average a human’s time perception is on the order of tens of milliseconds. The distance light travels in this time interval is the approximate radius of an individual’s sphere of now—a few thousand miles.

“Now” is not only a cognitive illusion but also a mathematical trick, related to how we define space and time quantitatively. One way of seeing this is to recognize that the notion of “present,” as sandwiched between past and future, is simply a useful hoax. After all, if the present is a moment in time without duration, it can’t exist. What does exist is the recent memory of the immediate past and the expectation of the near future. We link past and future through the conceptual notion of a present, of “now.” But all that we have is the accumulated memory of the past—stored in biological or various recording devices—and the expectation of the future.

The notion of time is related to change, and the passage of time is simply a tool to track change. When we see something moving in space, we can follow how its position changes in time. Say it’s a ball; as the ball moves, it will describe a curve in space, an imagined sequence of points from initial position A to final position B. We can tell where the ball is between A and B by ordering its location sequentially in time: at zero it is leaving the soccer player’s foot—point A; at one second it is hitting the upper-left-hand corner of the goal—point B. The curve in between A and B links the position of the ball at the intermediate times between zero and one second. A ball, however, never occupies a single point in space, and time can never be measured with infinite precision. (The most accurate locks use electronic transitions in atoms to achieve a precision of about one billionth of a second per day.) Mathematically, though, we brush all this aside and compute how the position of the ball changes in time instantaneously: for every moment of time we claim to know its position. Clearly, this is only an approximation, albeit a very good one.

We represent the flow of time continuously so that each instant of time has a (real) number attached to it. In our example of the soccer ball, time will cover the number line from zero to one. How many instants of time are there between zero and one second? Mathematically, there is an infinite number of them, since there are infinite numbers between zero and one. (You can keep subdividing intervals into smaller and smaller bits: a tenth of a second, a hundredth of a second, a thousandth of a second, and so on.) But even the most accurate clocks have limited precision. We may represent time continuously, but we measure it in discrete chunks. As a consequence, the notion of “now,” a time interval of zero duration, is only a mathematical convenience having nothing to do with the reality of how we measure time, let alone perceive it. I will have more to say about this and what it means about our notion of reality when we get to quantum physics, where nothing is ever continuous.

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Marcelo Gleiser

    Marcelo Gleiser is the Appleton Professor of Natural Philosophy and Professor Physics and Astronomy at Dartmouth College. Gleiser received a Presidential Faculty Fellows Award, given by the White House and the National Science Foundation, for his research in cosmology and dedication to teaching. A Fellow and General Councilor of the American Physical Society, his research focuses mainly on the physics of the early universe and the emergence of complex structures in Nature, including life. In addition to The Island of Knowledge, he is the author of three previous books, The Dancing Universe, The Prophet and the Astronomer, and A Tear at the Edge of Creation, Gleiser lives in Hanover, New Hampshire. Twitter: @MGleiser

    • Matt Kreinheder

      Great article Dr. Gleiser. I especially like the concept of a “sphere of Now”, a very cool way to language an abstract concept. I agree that “now” is much more a felt experience than a definable and finite number. But then, why try to use pure objective measures to define a subjective experience? If now is a purely experiential event then no calculation will be able to locate it. It seems that when we can’t specifically pin point something in time and space its value (in this predominately left brained, logical society) is diminished. Thanks again for writing this!

      • Marcelo Gleiser

        Thanks for your comment; a calculation can always “locate” something, given that it is an abstraction. So, it’s a location but not in real, physical space or time. What I intended in this part of the book was to show how such an intuitive notion such as “now”, that we use all the time, is actually a fabrication!

        • Hominid

          That depends on your frame of reference. Stand on the RR tracks before a speeding locomotive & you’ll soon discover that there is a now.

          • Marcelo Gleiser

            To how many decimal points you want to specify the exact moment of impact?

            • Hominid

              You’re delusional – there will be an impact.

            • Marcelo Gleiser

              I hope I’m not delusional…Of course there is an impact! that’s not the point. The point is that it is impossible to specify with absolute precision when the impact occurs. “Now” is an approximation, that’s all. It’s not that we can’t conceive of it cognitively. But we can only measure time with a finite amount of precision. That’s just how science is done. Not need for insults, just an effort to comprehend the meaning of concepts used in the physical sciences.

            • Hominid

              That’s not physical science – it’s philosophy. THAT’s the point. Of course we can’t define time – or a whole lot of other things. That’s the inadequacy of theoretical physics – which is most likely a consequence of the limits of cognitive acumen. Rigorous science attempts to approximate the universe that exists outside the mind. In that universe, there is definitely a ‘now’ even though we might perceive it a bit late.

            • mdburke

              Hominid, you are an idiot, you are spouting your opinions as if they are fact, about an unknowable universe of which you are barely a spec. There is no way to truly know any of this, yet you insinuate that everyone is wrong and belittle other opinions, even when they support your unsupportable rantings. If there is anything in this universe that does not, it is the logic in your arguments.

            • Hominid

              You’re full of baloney.

            • diana

              yeah, but, when?

            • dattajack

              An impact is a process over a period of time. An impact is not instantaneous as you claim. Only in physics class when making mathematical simplifications.

            • Hominid

              Irrelevant to the issue in question.

            • mdburke

              only one, but several places would be good, but I get your….. point

          • dattajack

            No, you consider an impact as an instantaneous occurrence. It’s not. It’s a process over time. I’m not even talking about the crumpling part. Before that! Zoom into the very first two atoms that collide. There’s always a first two. Always! The very first encounter between the first two atoms involves the two getting close enough for them to create a bond. The bonding process, the trading of electrons, occurs over a period of time far shorter in reference to the time of collision but much longer than the spin of the quarks than make up the nuclei of the atoms. So as long as the electrons are being traded there is a non-instantaneous process occurring inside the event you’re claiming to be instantaneous. It’s just wrong to claim that. Any process requires time, no matter how brief, and regardless of whether or not a human brain can naturally observe those brief processes with our senses.

            • Hominid

              It doesn’t matter – your argument fails.

          • Alone: bad. Friend: good!

            How can you discover there is a ‘NOW’, ‘SOON’?
            You discover ‘now’ at a later date?

        • mdburke

          don’t confuse language with physics, every student of physics will tell you that language is too simple a tool o explain the intricacies of physics. the term “now” is the best term to use to describe an event simultaneous to the observance, as apposed to then. This isn’t a Schrodinger’s cat experiment, time moves along in spite of the perception of it. The alternative to time is that everything happens at once, which, based on your perspective, is relative. It is the measurement of time that is arbitrary, not the fact of it.

          • Hominid

            You can NOT assert that if you cannot define time. What is time?

            I say it’s the minds interpretation of motion – i.e., time doesn’t exist, motion does. All objects are moving at all times, faster or slower, and our psyches interpret that as what we call time.

      • Hominid

        Predominantly, not predominately.

        Wherever did you get the notion that society is left brained and logical? It’s exactly the opposite.

        • Doppleganger11

          Technically, both words-though distinct-can be used in this context.

          Society doesn’t have a mind of it’s own, people do.

        • God

          There is no now! what are you talking Mr. Philosophy… Tell me about your experience of impermanence and will see what your right brain has to say. (piss me off those talking monkey!!!)

    • Peter Martin

      “Up is down !” – George Costanza

    • Peter Kershaw

      Well said. My thoughts were along the same lines as Mr. Kreinheder’s comment. Nothing spoils the experience of the flow of time (living) quite like math. There’s a fabrication for ya.

    • Hancock

      A neurologist friend told me of an experiment where the subjects were told to hold a mirror in their lap and look at a monitor displaying numbers in a sequential order, like 1, 2, 3, etc., they were told to hold the mirror so that they could see in their peripheral vision the reflected numbers, all the subjects could see the numbers on the screen in sequence, but the numbers in their peripheral vision skipped in the sequence, like 1, 3, 5, 6, 9, 10, 12. Some of the subjects reported that there was a noticeable delay in the number sequence reflected in the mirror. Which is a great example of how the brain prioritises information.


      Brain mapping and this area of study is quite mature. Most humans are easily controlled.

    • Jesse G Herrera

      Sometimes when I am driving late at night on the highway, I will notice that I am now at Point B. I remember Point A, but I don’t remember the space or history between Point A & B. Where did that time go? Maybe my brain went out to lunch for few minutes? I’ve wondered about everything I see, that I am seeing right now. Is it real? For it to be real, there must be a “now”, but by time I’ve thought about it, I’m at another “now” like when I was driving.

    • Rick Chesler

      We know there’s no such thing as “now” because by the time you say the word “now,” the point int time you were referencing has already past. Everything is either in the future, or the past. “Now” is just a colloquial term that means “in the present,” it’s not a technical term.

      • Hominid

        One can equally well argue there there is ONLY a now, the past & future being illusions.

        • God

          So how come I can see your stupid comment 12 days after King kong?

    • Rev. Jasper P. Schwingster

      May Jesus forgive you of this blaspheme.

      • eric.wallter

        Err… and what exactly are you referring to, Reverend? I mean, what ‘blasphemy’ are you talking about?

      • isnamthere

        And may santa claus leave no coal in your stockings, or the easter bunny leave no pellets in place of your jelly beans.

      • shunga munga

        If there were a Jesus, and he were the Jesus you presumably are referring to, he is dead, and there is no evidence other than a moved stone to support the risen from the dead theory. But in the spirit of some accounts of this Jesus’ teachings, I forgive you for missing the point of the mythologies.

    • Hobartcat

      Wow. So, our perception is illusory. I’ll alert the media.

      • Arcanek

        The ‘perception’ of the media is far more illusory.

    • Thoughtful_Rationalist

      After reading this stimulating article, the Buddhists, who prize living in the NOW, will be so disappointed.

    • David Wright

      Like quantum mechanics, these short time lags are not important to us biologically. Only some of our techo devices have to account for these lags.

      To say it is false that “I am reading this” is an exaggeration. During the moment it takes to process information, I am reading. No actions are instantaneous because any action requires the passage of time. Time is the fourth dimension.

      • Bruce

        Good perspective and understanding David. If I may add this little bit. Using your statement “I am reading this” there are several constructs to the statement. The sense of a someone (I am) the action (reading) are both a feeling of “beingness” and a “doinginess” but the common denominator is the detached “Isness” that is a dispassionate witness and gives reflection to any movement, activity that sense of beingness.

        • dattajack

          No, it’s a horrible understanding to say time is an illusion. Any form of matter outside biology doesn’t have a brain and those things obey time. The notion of time requiring a brain is arrogant and flat out wrong.

          • Hominid

            How do they “obey” time? Those are just words. What is time? How does an object “obey” it? You’re talking nonsense.

      • Hominid

        Time may be a illusion. Is there time without a brain? It’s like color – it doesn’t exist outside the mind.

        • dattajack

          No, matter has demonstrated the use and obedience to time before human brains and there’s no reason to think matter won’t keep obeying time long after humans.

          • Hominid

            Nonsense. Time does not exist outside a brain. Motion does – but time is just the human mind’s interpretation of motion. Just as the mind interprets wavelength & contrast as ‘color’ or pressure waves & frequency as ‘sound.’ Color, sound, pain, emotions, time, etc. do not exist outside the mind – they’re illusions.

            • dattajack

              No actually the laws of physics obey time and all of the phenomena you just listed are physical phenomena that exist in nature before life even existed on earth. Motion is matter traversing a distance per unit of time. You can’t have motion without time. Sure, a unit of time can be arbitrary but you could easily change up the unit system based off an actual physical repeatable process that occurs independent of whatever drugs you’re smoking and whatever supernatural shit the flyers at your health food store are claiming.

              You listed a couple basic phenomena of nature and then a couple that are specific to the brain like emotions. Color is texture and light frequency and effects natural things without a brain predictably and repeatedly. Sound is a frequency of pressure and can effect natural things without a brain predictably and repeatably. The brain’s perception of time might vary depending on what drugs you take, how much you know about physics, or your psychiatric health, but time is constant with respect to speed of mass and gravitational strength. Does that make sense yet?

            • Hominid

              You don’t know what you’re talking about.

            • Rodrigo

              No, YOU don’t know what you are talking about.

              you are confusing perception with reality, just because we perceive it subjectively doesn’t meant that it doesn’t exist objectively

              Color is the perception of frequency of light waves the brain takes in and interprets.
              This is like saying there is no hot or cold because those are feelings the body interprets for relative temperature.

              The thing is, temperature still melts or freezes things and changing how light reflects off an asteroid can determine whether or not it comes in collision with Earth.

              Color certainly exists, it’s just our brains interpret it a specific way via optical imagery. If our eyes saw temperature in a color spectrum (like the Predator) and felt the lightwave reflection as hot or cold (red being coolest and Violet being the hottest), it wouldn’t change whether or not these things exist or not. They do. We are just sensing them differently.

            • Alone: bad. Friend: good!

              Temperature is real. Something can be zero degrees frozen — OR — boiling hot and steaming.

              Color is just a vibration and vibrations can occur up to yottahertz and beyond. But the thing is — they are all exactly the same — just vibrations. Your brain zoned in on a small chunk of frequencies and you are fooled into thinking they are color.

            • Hominid

              Temperture is real – your perception of temperature is not.

            • Alone: bad. Friend: good!

              What do you think… stuff is only frozen because your brain thinks that? I was not talking about perception of temp, it does not matter if you perceive it — stuff can boil. You can’t lump it in with color.

            • Hominid

              “Stuff” freezes at different temperatures. There is a physical property of temperature (the presence of heat energy) just as there is wavelength to electromagnetism. But, it is very different from the property of ‘temperature’ our nervous system perceives which is always relative and spectrally constrained. Like most people, you are deceived by words – you are a slave to language.

            • Alone: bad. Friend: good!

              The different freezing temps are irrelevant — it was just to make a point.

              Did you see this…
              Lubos Motl was talking about you here…

            • mdburke

              you also are a slave to language, otherwise you wouldn’t use it so much.

            • Hominid

              I use very little, moron.

            • Alone: bad. Friend: good!

              Wait a minute… I never mentioned perception of temp. Your comment agrees with me

            • Hominid

              Perhaps so – we may be talking past one another.

            • Alone: bad. Friend: good!

              I had to reload the page and I see you added a lot more to your comment but it still agrees with me.

            • mdburke

              now you are arguing semantics, we differentiate the wavelengths into the observable patterns and call them color, color exists, your definition of it is what is flawed, the color blue is the perceptible section of light between two measurable wavelength perimeters, that is blue, blue exists.

            • Hominid

              You couldn’t be more wrong. You’re an ignoramus.

            • Hominid

              Study psychophysics – you don’t know what you’re talking about.

            • Rodrigo

              you have no evidence that time is not real outside of your “mind”.
              And yes, color exist outside of your brain. (Yes, I’m a physicist). the brain perceives.

            • Rodrigo

              sorry, the comment was for hominid

            • Hominid

              You’re no physicist or you would realize there is no color outside a nervous system – or tone, or odor, or taste. And, color does NOT equate to wavelength, just as the perception of temperature does not equate to object temperature. These phenomena have been easily and repeatedly demonstrated in psychophysical experiments. You’re scientifically illiterate.

            • NILESH SHINDE

              I agree with datajack. as time is everywhere time only has created our earth and made eras the ice age was all over with time and all the eras came and went isn’t this mean that time has made everything and can destroy everything. time is the greatest power and no one can defeat time.
              In fact in the poem ‘OZYMANDIAS’ and ‘NOT THE MARBLE NOR GLIDED MONUMENTS’ both the poets P SHELLY and SHAKESPEARE state time as the creator and destroyer of everything
              time is forth dimension
              according to me there is no life and matter without time

            • Rodrigo

              There is no “mind”
              There is “EYES” which converts light into signals for us to perceive, and yes, light has color.

            • Hominid

              Nope! LIGHT HAS NO COLOR – it has wavelength and amplitude. All electromagnetic energy has an associated wavelength and amplitude, but only a tiny part of the electromagnetic spectrum is perceive BY OUR NERVOUS SYSTEM as colors.

              I can show you two squares of exactly the same wavelength & amplitude in two differing contexts and you will swear they are two very different colors.

            • mdburke

              Light does have color, light has all color, our physical being has developed the ability to perceive light in it particular spectrum. We assign it the name blue or red, but that is irrelevant, Color exists because we perceive that it does, and there is no evidence that anything exists outside of our perception of it, so that frame of reference is the only thing that matters. Color exists because we can measure the wave length that defines it.

            • Hominid

              Blue and red DO NOT EXIST outside the brain, dummy.

              When you die, the universe continues to exist – that’s proof positive it exist OUTSIDE your perceptions of it. Moreover, we have enormous amounts of compelling evidence that the universe existed for billions of years BEFORE there was any nervous system to perceive it.

              It has been repeatedly demonstrated that wavelength does NOT define color. You’re an ignoramus as well as an idiot.

            • mdburke

              the mind can travel back in time to relive memories, or project what might happen in the future, therefore, time does not exist in the mind. but the universe continues to roll on along the linear path into the future, and can not go back. that is the essence of the passing of time, whether or not we measure it is irrelevant, you can’t stop it, or go back in it, at least not yet, time passes.

            • Hominid

              You contradict yourself to the point of absurdity. “The mind travels back & forth in time, but time does not exist in the mind.” You’re goofy.

            • mdburke

              you are confusing the perception of time with the measurement of time, vs the passage of time. Time passes at a constant rate, your perception of time in your mind is relative to things, like the clock on a wall in your office or classroom seems to run more slowly toward the end of the day, or the 5 minute snooze seems to only be 30 seconds, in that way I say that time does not exist in your mind because it is inconstant. while the period of a pulsar is exact, we can measure the passing of time, but our mind does not perceive it in the same way.

            • Hominid

              That’s what I’ve been saying throughput this whole thread, you moron – what the brain perceives as ‘time’ is not real. What the brain perceives is NEVER reality and that can be easily demonstrated.

          • NILESH SHINDE

            I agree with you read my post below >——–>

      • Charan Langton

        Indeed it is an exaggeration to say there is no now. Human signal processing has finite cognitive window based on the abilities of its visual and nervous systems limits.Our time-resolution is very large, and hence we define a great many events happening in our time-resolution or time-window as happening “NOW’. Nothing surprising about that. Electronic devices and digital receivers too have finite windows, a signal received is averaged across the window or just sampled at one point to make a “decision”: We work the same way and are forever not only error correcting but also limiting the processing to a finite window.

    • Heather

      How do you apply this theory to blind people? Time and the perception are not perceived only by vision. Also…
      ““Now” is not only a cognitive illusion but also a mathematical trick, related to how we define space and time quantitatively. One way of seeing this is to recognize that the notion of “present,” as sandwiched between past and future, is simply a useful hoax. After all, if the present is a moment in time without duration, it can’t exist. What does exist is the recent memory of the immediate past and the expectation of the near future. We link past and future through the conceptual notion of a present, of “now.” But all that we have is the accumulated memory of the past—stored in biological or various recording devices—and the expectation of the future.”

      Time was created by our lack of ability to remain present with all of ourselves at once…Now. When we experience pain or discomfort we attempt to separate ourselves from it by leaving it in the past as baggage that is to be left behind. While avoiding an experience we also project into a fantasy of something better to take us away from being present now, creating a perception of a future, hence sayings like, “Tomorrow’s a new day” or “Look to a brighter future”. When we react with denial or repression to pain we project our perceptions of ourselves into the past and future which seemingly gets us out of having to be responsible now, for everything we have avoided. P.T.S.D.(Post Traumatic Stress Disorder).
      The way to experience Now is to be fully present with everything we are in denial of which is all the things about ourselves that were ever and still are in pain that we wanted to leave in some place called, ‘the past’ where we could appear helpless to go back to while reaching into a future of expectations to get out of the Now.
      To experience Now, is in y/our ability to remain present with all of yourself all of the ‘time’. Now, is real when we allow it.

      • Hominid

        You are speaking of the PERCEPTION of time – a delusion of the nervous system.

        • Alone: bad. Friend: good!

          NO! You are perceiving time but it is also happening / real.

          • Hominid

            Something is happening – I agree – but to call it ‘time’ tells us nothing meaningful about it.

            I can define color as the mind’s interpretation of the external properties of wavelength, amplitude, and context, (I may have to throw in a few other variables internal to the brain as well).

            Can you do the same for time? What are the aspects of time that are independent of an observer? I say it doesn’t exist externally – it’s just another WORD for motion that we’ve invented to account for our conception of it.

    • Blueprinter

      I don’t like feeling pain, whether it’s real or not. I don’t care if it’s real or not, I want it to go away NOW! Or as ‘fast’ as possible. (Whatever fast means, because if there is no NOW, and there is no past, and there is no future, then what is there?) So, as far as I’m concerned, pain and pleasure, and how long it lasts is what I want to influence.

    • Amrit Sorli

      what a nonsense that there is no now

    • Amrit Sorli
    • David Tomasello

      Wow! Interesting stuff.I feel more intelligent now

    • Larry Swain

      The most accurate “clocks,” not “locks.”

      • Hominid

        Really, Larry – that’s your catch – a typo?

    • Gustavo Gomes

      Great ideas Dr. Gleiser. I am specially interested in bringing the same rationale to space. How many numbers are between 0 and 1 centimeter? Infinite, right. But I can not divide one centimeter of cloth forever, I will have to stop at some particle. So materially finite and mathematically infinite. Wouldn’t be mathematics playing us a trick?

      • mdburke

        it depends on the sharpness of your tool, and the acuity of your vision, science is constantly finding smaller and smaller building blocks to mater. the logic you use is broken, humans invented math to explain the natural world, just because a number is inanimately dividable is irrelevant, just like the clock on the wall doesn’t measure time, only the passing of it.

        • Hominid

          Nope! A particle cannot be reduced. Math is the ultimate delusion.

          • Alone: bad. Friend: good!

            Correct, they have the model slightly wrong but there are things you could call proton, neutron and electron but it stops there… NO QUARKS.

            • Hominid

              See the latest version of the Standard Model. It’s based at least in part on collision experiments that HAVE busted protons and neutrons into smaller component particles.

            • Alone: bad. Friend: good!

              No! Something like a proton is made from a cluster of individual string particles (not the string theory type). So if you smash up a proton you are only getting individual strings or pieces of strings (like shrapnel)

            • Hominid

              Such a radical departure from the now widely accepted Standard Model requires citations of strong findings to support it.

            • Alone: bad. Friend: good!

              There is NOT any standard model.
              They smash up stuff, get different weights / mass and call the different weights different particles.

              It is all just guess work and most of the guesses are horrible.

              “On 4 July 2012, the discovery of a new particle with a mass between 125 and 127 GeV/c2 was announced; physicists suspected that it was the Higgs boson.”

            • Hominid

              You have a lot of studying to do.

    • abc123

      My apologies to Dr. Gleiser but the concepts this article presents are really not new or groundbreaking. It is not a great leap from learning the speed of light to the realization that “now” is stitched together by our minds. If it wasn’t, it certainly could have been deduced in the early twentieth century or earlier by someone observing a loud event in the distance and hearing it a second or two later.

      What also continues to surprise me is how Eastern philosophy’s long standing realization of these concepts and exploration of their philosophical implications is rarely mentioned. Individuals in the Vedic culture of northern India were turning their awareness inward to explore the various complexities of the mind – including analyses of how sensory input is stitched together to form experiences – at least 5000 years ago if not earlier. The mind’s construction of experience, the sense of now and, to a large extent, the sense of individuality is sort of the central tenet eastern philosophy and psychology.

      Admittedly the metaphysical tone and terminology used to describe this inner research might make it difficult for the modern western mind to accept the fact that this research was in fact scientific in approach and rigor and not conducted for religious purpusoses, at least not exclusively, but done to expand our knowledge of our bodies and brains.

      The experience of many experienced meditators is that of having transcended the interruptions of sensory perception and inner thoughts & emotions to reach a state of mind where all you expetience is a state of pure awareness. Awareness of what you might ask? Its a mystery. Does awareness need an object? The folks that have reached this state will tell you not to take their word for it but test it yourself.

      I apologize if these ideas are addressed elsewhere in the author’s work.

      • Hominid


        • shunga munga

          What one is ignorant of usually sounds like it. The paradox of one reaching a state of pure awareness is that the analog I ceases to exist. Perceptions of time change. An hour passes instantaneously while seconds resonate like a gong, but as abc123 has written and any practitioner will tell you it is difficult if not impossible to intellectually describe experience, not unlike explaining the taste of an orange to one who never has.

        • Martian Spaceship

          you seem like the type that yells at a bird to shut it’s beak for singing a beautiful harmonious song because you know not the meaning when in fact it’s articulating its message quite clearly.

          • Hominid

            Poetry – while pleasing – is wishful thinking, not reality.

            • Alone: bad. Friend: good!

              Now I know how you have managed 25,000 comments, they are mostly one-liners.

            • Hominid

              Conciseness is a virtue.

              That, and I’m retired and a proficient multitasker.

    • Daren

      Of course there is a now. Our perception of it is stitched together as best as we can. But the reality of the now exists outside of our ability to perceive it.

      • God

        So space doesn’t exist now!?

        • Hominid

          What is space?

    • The Master

      I disagree with the premise that ‘now’ is a time interval with zero duration. ‘Now’ is of infinite duration; it is always ‘now’ in our perception. Of course what we perceive is the past, but the past is the frame within which we experience the present.

    • Richard McCargar

      Man, this is old. On top of that, it ignores the fact that our minds work in such a fashion as to be useful to us in our everyday lives.

      Is this guy a late-teen pot-smoker?

      • God

        I don’t think so but I believed it’s time to put you in a recycle bin. You are no use here!

        • Richard McCargar

          Says the kind of person so assured they are right, that they post anonymously.

          No doubt you do that because you are a coward, and know that if you made your comments with your true name, your friends/family/employer, wouldn’t approve.

    • donqpublic

      Since I can never cognitively experience “now” or the “future” ( the Kantian thing in itself?) because of a cognitive processing lag, then I gather now and the future are not objects of empirical science but mere illusion (a Humean psychological cultural construct or fabrication?). Indeed, when peeling back the cognitive processing layers of consciousness I can never see the “I” that’s doing the processing in the here and now: cowabunga dude, I’m an illusion of constant conjunctions of things in time, just like you and the universe. I’m just a bad habit. But I can still have fun exploiting and oppressing illusions like you for fun and profit; funny how unreality (values) can seem so real and satisfying when at some other illusion’s expense. Damn, being on the progressive right side of history and celebrating the end of history and the last man is an illusion and a fraud after all; the girls are going to be pissed.

    • EscondidoSurfer

      All of this makes the sublime truth from God when he revealed his name as “I am” (Yahweh) all the more profound. The biblical claim of a God who defines himself in this way is striking, let alone the claim that he is able to fully inhabit all of creation within his “now,” freely taking whatever time is needed to accomplish his purposes. Such truths should be a matter of deep reflection by all those who regard his revelation as trustworthy in light of the inability of science to grasp what “Now” really means.

    • James Hedman

      Your reliance upon Zeno’s Paradox as an analogy is lame.

    • ttrr

      Dear Marcello, the reality is the opposite – there is ONLY now.

    • ttrr

      … and time as we perceive it is an illusion, needless to say.

    • Iarwain Benadar

      to summarize the article: we are all bound by perception in a relativistic universe. “Now” can only be apprehended though a larger domain that surrounds, yet is unbound from, perception. I define this larger domain as “knowledge” — “now” with a “k”.

    • TomKinney

      This comports, somewhat, with something I’ve been thinking about;
      the fact that humans are constantly “learning their (personal) lessons” about
      life only in hindsight. We continue to repeat our mistakes, which like karma,
      seem to be sown into our system from our beginnings. As if we were
      entirely predisposed to having a given condition; that of having to learn the same lessons over and over again. As if life were some sort of test. But who’s the tester and what’s the point of the test?

      And those most vital questions we don’t seem to be able to grasp—as if they’re always just beyond our comprehension—in our current physical form, the point being that we must relive our built-in mistakes over and over again. And, saddest of all, we die not having been successful–beyond a limited point–without having corrected our mistakes.

      Here the author is talking about the slightest amount of time that elapses
      between reading something and when what we have read reaches our
      brain. But we’re always just a shade behind ourselves in everything we do, as if
      time is a sort of cosmic trickster never letting us catch up. Always late to
      the party.

      Anthony Peake, new age quasi-scientist, has supposed that when we
      are in the act of dying, time slows down exponentially from a second to a half
      second to a quarter second, etc., ad infinitum, so that the actual moment of
      death never actually occurs. What then happens? Perhaps we leave the sphere of
      time altogether to enter yet another dimension, or world, or whatever, a
      timeless place in which we dwell eternally beyond all these physically
      constraining paradigms.

      Or not.

      Who knows?

    • mikie

      So, if I’m reading this on a LCD monitor, does the info get to me sooner, since the light in the room doesn’t have to first bounce off the page before getting to my eyes?

    • Gordon Shumway

      I’m far more concerned with why we park in driveways and drive on parkways.

    • Gabriel

      An instance has no time duration, like a point is dimensionless in space. Both define a “singularity”; an imaginary construct of our intellect. What precisely is zero and infinite? On the other hand, a moment is defined as roughly 90 seconds. It seems that for our practical sensorial experience “now”, in the present tense, means something more appropriate like a moment. Logic, reason, and mathematics sometimes let us experience its own limits to understand the reality of the cosmos we live in. Does Achilles ever pass the turtle and wins the race?

    • Morgan Buenger

      Very interesting thought provoking article Marcelo, thank you.
      There is no mathematical now, just like there is no mathematical time that is independent of location. You mentioned the sphere of now, well time is also a sphere defined by an orbit, not a rectangle. Mathematical time that is an arrow shooting into eternity in a straight line without relation to locality does not exist in reality. Hence the non-existence of the linear now. The universe is not square, so there is no square mathematical now either. Time is always related to a local orbit. The now we commonly refer to is a round now that is related to our orbit around our sun Sol. The arch degrees of this path we share. If we perceive the visual stimuli individually at different times due to processing speed limitations/differences of our brains that does not mean that we don’t have a common now.
      Mathematics is a tool, not to be confused with reality. For example: the soccer ball leaving the foot of the player mathematically never reaches the net because we can always divide the distance of impact by 2. However far you say the ball is from the net there are infinite divisions of space and time. While you are calculating that the Germans shot 7 goals into the net against Brasil during the World Cup semifinals. And that is reality now. Sure the tv and radio broadcast signals and transmission lines across the world and our individual bio-electro-chemical perceptions created lag times but the times the balls touched the net were very/vary specific Nows in terms of a location on the sphere of time that is our orbit around Sol in arch degrees.
      I hope this makes sense.

      • Martian Spaceship

        i think Janis Joplin sums it up what you’re meaning pretty nicely by stating “Tomorrow never happens. It’s all the same fucking day, man.” if it weren’t for the circular nature of how we perceive it.

    • skipper

      What about conscious awareness of thoughts? The thought appears in our conscious mind awareness (in spoken words or picture). We consciously experience the thought (as spoken word or picture).
      Therefore all consciousness awareness even of thoughts lags
      reality by at least the speed of light.
      True enough?

    • carlos

      I think I understand what you are trying to describe.
      But it doesn’t seem right to try to force the ‘now’ to two separate instances or references, when the light beam originates from the book, and when the eye, or brain, perceive it.

      The way I understand it, is that it doesn’t really matter when the light bounced off the book, the ‘now’ for us would be when the brain processes the information (even if it is a delay image, and I’m also not accounting for conscience or anything like that).
      You could also see it from the book’s point of view if it had conscience, and then that ‘now’ would happen when the light beam bounced off, but i don’t think you should mix the two points of view.
      like one of the comments, now from the human perspective is around 90 seconds, I think it has to do with the amount of time it takes to store information in memory.
      From a maths or physics point of view, it might be something different because time is something different.

      In regards to the hypothetical brain experiment, I don’t believe you need a brain with ‘ultra fast perception’, I believe you would need a brain that is not constrain by distance; something like a a brain that can be everywhere at once,

      Thank you for writing this article, and giving people the chance to participate and explore new ideas and ways of seeing reality.

      *Sorry for my grammar, English is not my first language.

    • Mike

      so there is only the past and the future…

    • seescaper

      Suppose that we agree that there is only a past and a
      future. What we call the “now” is a construct that our brain uses to orient us as we move from past to future. So, past becomes future instantaneously—there is no time interval that is large enough to be measured that separates the transition.

      I seem to smell an aspect of the uncertainty principle here. As you try to nail down the exact time interval transitioning from past to future, the energy of the system would become increasingly uncertain. So one cannot define a time interval constituting the “now” with precision. When something is just
      in the process of “occurring,” there is an inherent uncertainty of whether it is part of the past or future. Here, in this fuzzy zone, the arrow of time can go either direction. This uncertainty phase is so brief that our brain and sensorium cannot appreciate it. Rather, our brains construct for us a “sense” of the present. Events occurring sufficiently “ago” in time we sense as occurring in the past, and for events that have not yet “occurred,” our conscious brains can attempt to predict by running a simulation of what might happen in the future.
      As we move in a transition to the future, there is again a fuzzy transition zone that is too small to perceive, so our brains smooth it out.

    • sand

      no distinction between past present and future. a. einstein

    • jess

      Werner!!!! Where are you hiding. EST 101, 1972

    • Peter

      I maintain that now is possible, indeed exists, even if the perception of it varies. Which is to say, we can indeed define now. And we do indeed define it, we do measure it and we do calculate very accurately every day. Which is why we have GPS. We have the technology to quantify, measure and calculate this. To say this is a mathematical trick which depends on how we define space and time is to take a strange position on the issue. Is this the same sort of mathematical trick we know as the Pythagorean Theorem, which depends on how we define a geometric plane, etc? Is all of mathematics a trick, dependent on how we define mathematical axioms? I suppose you could make that case. But to go down that road just muddles and mystifies the subject – perhaps intentionally, in an attempt to appear profound? At any rate I would prefer clarity over mystification. GPS knows where I am because of Pythagoras and Einstein – because we can calculate triangles and measure distance. Time is like distance, mathematically. It is one thing to say there exists optical illusions of simultaneity due to lag times in neural processes and photon exchanges, it is quite another to say simultaneity does not exist. All measurements are approximate. Any measurement we make that does not include the level of precision (or error) inherent in the measurement is meaningless. Defining such a level of precision is not a mathematical trick – it is simply necessary. Again, it is one thing to talk of illusions and to say what appears as the now is not the now – but it is another thing to say that we cannot calculate the now. We can. We do. Stop trying to mystify. Clarify, clarify.

    • The contradict

      To experience now, you must to have a self. But are “you” the one who processed the received information. Those information are received by those receptors, and further processed by your brain, then come a questions are these brain or organs are a part of your “self”? So we have to shut out those receptors, and use the help of brain to think the true state of truth (the thing it is). Once you understand the thing it is, including the light travelling at the light of speed, it just the way it is. And the good point you mentioned is that, for what we have seen through our eyes is just as an illusion; once we understand them the thing as it is, then you may experience now, the the things happening at every moments of now, it never stop. My 2 cents opinion.


      As time is everywhere time only has created our earth and made eras
      the ice age was all over with time and all the eras came and went isn’t
      this mean that time has made everything and can destroy everything. time
      is the greatest power and no one can defeat time.
      In fact in the poem ‘OZYMANDIAS’ and ‘NOT THE MARBLE NOR GLIDED MONUMENTS’ both the poets P SHELLY and SHAKESPEARE state time as the creator and destroyer of everything

      according to me there is no life and matter without time


      some scientist also believe that time is forth dimension

    • Alone: bad. Friend: good!

      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

    • mdburke

      Might as well pack it in everyone, our collective intellects are no match for the immovable assumptions of Hominid, apparently, he is the smart one. But I am guessing that is only a perception of his mind.