Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS

Experts Banner

Q&A With Dr. Harry Ferguson
Astronomer, Space Telescope Science Institute


Lee Anderson
Blacksburg, VA

Why do some celetial bodies, i.e. planets and galaxies, spin? What keeps them spinning? Do they all rotate in one direction, ccw or cw, and if so, why? Thank you.

Spin probably came about as a result of tidal interactions between different gas clouds as solar systems or galaxies were forming. In our solar system, most but not all of the planets spin about their axes in the same direction. All of the planets go around the sun in the same direction. However there are some asteroids that orbit perpendicular to the plane that most of the planets lie in. Most, but not all of the stars in our galaxy orbit the center of the galaxy in the same direction. Stars in the Galactic halo, which surrounds the center of the galaxy in a more-or-less spherical distribution, orbit more randomly. Some of the stars go around the center in the other direction.

Galaxies rotate every which way. There are some fairly weak correlations seen in the orientations of the axes of galaxies relative to their surroundings.

Best Regards,
H.F.


Ramon A. Alonso
West Haven, CT

Dear Dr. Ferguson:
If I was able to "travel" to the edge of the universe, what would I see? -Does space go on forever and what is forever anyway? -What lies beyond the last galaxy in the Universe? -In view of what we know today about the universe, is there a place for a deity in the scheme of things? If the universe is the way it is because that is the way it has to be, then, perhaps physics is the deity.

Thank you, Dr. Ferguson!
Ray Alonso

The universe may be infinite, or it may be finite. We don't know. If it is finite, a light ray that left a spot in the universe soon after the big bang will return to that same spot right before the "big crunch." If it is infinite, light rays will never return to the place they left. In either case, the universe has no edge. It looks the same from every vantage point. That is an assumption that is at the core of cosmology. If that assumption were proved wrong then we would have to rethink the whole big bang thing. There is certainly room for a deity, as long has he/she is flexible enough to realize that he/she might not have done everything in exactly the same way and at the exact dates given in certain religious texts.

Best Regards,
H.F.


Name and City Withheld

Benjamin Franklin left a small amount of money to accumulate for 100 years. It became so large it provided Museums, water systems and many other things. Because I believe we must colonize other planets for the survival of the human race, it is my intention at the death of both my wife and myself, to leave the residue of my estate to a foundation for that exploration. So far, I have had negative results from NASA, National Geographic, Smithsonian and Carl Sagans Society. THEY ALL WANT THE MONEY NOW and are not interested in waiting for a hundred or more years to begin colonization of other solar systems. It is my belief that in less than a hundred years we will discover faster than light travel and be able to accomplish such colonization. If not in other systems or galaxies, then perhaps on Mars or a moon of Jupiter. DO YOU HAVE SUGGESTIONS OF HOW I MIGHT SET UP SUCH A TRUST SO THAT IT WOULD NOT BE RAIDED BY ??? The only place I have been able to find such a place is in Raccine, Wis.

Sounds like an interesting idea, but I'm afraid I have no advice.

Best Regards,
H.F.


Greg Alford
Edmonton Alberta Canada

I've heard two different answers for the amount of time that light takes to cross the milky way galaxy. I have heard in your show that it takes 70 000 years but i heard on another show called universe: the infinite frontier that it takes 100 000 years. now this is quite a difference and i am curious which one is accurate.

Greg Alford

Actually the two answers are consistent with each other. The problem is, there is no real well-defined edge to the Milky-Way. It just trails off into space. Also, our measurements of the distance from the sun to the center of the galaxy (which is fairly well defined), are not very precise. Good to maybe 10% accuracy.

Best Regards,
H.F.


Peter Driscoll

Is it at all posible to inject a radar, or space probe into a comet? like if we could connect a probe to take pictures and send them back to earth from where the comet has been it would save us(NASA) lots of time, energy, and money to have our probe's be carried by a natural force. Something like Hale Bopp is not realistic because it must travel so far because it only comes around every couple thousand years. But Haley's Comet show's up about every 75 years. And if we could attatch a telescope to Haley's comet then it could gather images and other info and the next time it came around the earth we could read the info off the probe.

I have predicted a few probably's with this already, such as: Wouldn't the heat of the comet be unsustainable for the probe? Is the comet too far away for our solar system to be successful intersepted? Do we not have the tech. to be able to read a comp. info at about .00001 light year's away?

I have wondered this question for a couple weeks now but have not brought it up untill now so it might sound unrealistic. thanx! ps: i loved the show, 'Mysteries of Deep Space'! there should be more shows like that.

It is technically possible to build a space ship to land on a comet. However, there is no real advantage to doing that from the point of view of remote sensing. It doesn't save any money, since you have to expend all the energy to get into the same orbit as the comet before you can land on it. However, it would be nice to scoop up a bit of a comet and bring it home.

Best Regards,
H.F.


Ken Sharp
Deux-Montagnes, Quebec

I have read in many books that the universe can be compared to a soap bubble that is expanding. That the universe is the skin of this expanding bubble. If this is so how do you explain the fact that as you look back in time to where the universe used to be, the angle of vision doesn't get smaller. In other words how can you see extremly old galaxies in every direction if the universe used to be smaller and expanded from a singularity. Would you not have to narrow your view to where the universe used to be to see these old galaxies?

Everything in the universe was part of the big bang. There is no center and no edge, and it looks the same from every vantage point.

The analogy that only partially works in helping to visualize this is to take a look at a globe. Imagine you are a two-dimensional being. You live only on the surface of the globe. You cannot move in toward the center of the globe, and you cannot leave its surface. In fact, the only dimensions you can sense at all are along the surface. So, now, where is the center of your world? Put another way, where is the center of the SURFACE of the earth?

Now imagine that the globe is actually a balloon and someone starts to blow it up. All the continents start to move apart. The ones that are further away from where you are standing move away faster. Your whole world is expanding. Yet it doesn't have a center in the two dimensions you are familiar with. The expansion would look the same from wherever you stand.

The universe works the same way, but in three dimensions.

Best Regards,
H.F.


Vini Falciano
Rochester, NY

Dr. Ferguson,
Is there a better model to understanding the images we receive from space (billions of light years in the past)?

By the time we get this "light" from distant galaxies, it is already millions of years old (which would imply from a "smaller" universe closer to the Big Bang), but yet these galaxies are already spread across the . . . universe, as it were.

Why don't we see the beginning? (Since I don't know the numbers, you can relay the Math. I can handle it!

I tried the time vs. 3D concept. I'm just not gettin' it!

The furthest back we can look is to a time when the universe was about 300,000 years old. Earlier than that, the universe was made up of subatomic particles, and light couldn't travel very far before being scattered off in another direction.

There are all sorts of analogies to the expanding universe (living on the surface of an inflating balloon is a good two-dimensional analogy). However, none of them are wonderfully satisfactory, I agree.

Best Regards,
H.F.


Howard Alter
Toronto, Ontario, Canada

Dear Dr. Ferguson,
During this fascinating program one of the scientists involved in the Hubble Deep Field observations described having discovered galaxies up to 14 billion light years away, the image therefore being of the universe at its infancy. How, I wonder, did these particular galaxies come to be so far from the Milky Way - from the explanation given of the Big Bang, 14 billion years ago galaxies must have been much closer together; indeed, only a billion years before they had been part of the same mass. It would appear, therefore, that our galaxy and those distant ones must have been travelling away from each other at practically the speed of light to be 14 billion light years apart after only 15 billion years. Please help me with my confusion about this.

Sincerely,
Howard Alter

Yes, the relative motion of our galaxy relative to the most distant seen in the Hubble Deep Field is nearly the speed of light.

Best Regards,
H.F.


1. Is a Galaxy a group of planets or early form of solar system?

2. We see movies in theaters about outerspace and the types of space craft is awesome; even though it is just a movie, these are cool ideas and the question that comes to mind is why can't someone build a much faster space shuttle so that it wouldn't take years to visit other planets??

3. All joking a side, is it possible for someone to buy$$$ a planet? The Moon for Example?

One of my future goals someday is to become an astronaut and the mysteries that it holds encourages me to keep this dream alive. One draw back however is the speed that the shuttle moves. Man, if only there would be a faster shuttle!!

Thanks for your time!

1) Galaxies are huge assemblages of stars and planets. Our galaxy has about 100 billion stars. It probably has even more planets (our own solar system has nine, and we only have one star).

2) Even if you could build a space shuttle that could travel close to the speed of light, it would still take quite a long time to speed up and slow down (otherwise you kill the astronauts), so a trip to even the nearest star is something that would take generations -- and lots of $$.

3) Can I interest you in some beachside property around Alpha-Centauri?

Best Regards,
H.F.


David W. Smith
Conshohocken, PA

How is the size and distance to various space objects determined?

There are lots of different ways. None are very precise. The most direct way is to measure "parallax," that is the change in the position of a star when the earth is on one side of the sun, compared to when the earth is on the other side of the sun. This can only be done for fairly nearby stars. For distant objects like galaxies, astronomers try to find "standard candles," such as certain types of variable stars which are known to have a fairly constant brightness from studies of our own galaxy. By comparing the brightness of the stars in the distant galaxy to the brightness of the same type of stars in our own galaxy, we can get the distance.

Best Regards,
H.F.


Jake Tapia
San Francisco, CA

Your program said that there are over 50 billion estimated galaxies in space...I was wondering...When you look up into the night sky with the naked eye, are most of the lights up there stars...or galaxies?? I am starting to think that a star is never alone...but always included in a galaxy...I hope I do not sound to un (space) educated....Thanks

Most of the objects you can see with your plain eye are stars in our own galaxy. If you go to the southern hemisphere and look up on a dark night, you will see our two nearest neighboring galaxies, the "Magellanic Clouds." These are actually "dwarf galaxies" orbiting around the Milky Way. Each contains only a few billion stars. In the northern hemisphere, you can make out our nearest big neighbor, the Andromeda galaxy, if you know where to look. It's hopeless to try this in the city; you need a really dark sky. The Andromeda galaxy is 2.5 million light years away.

There may be some stars out there that are not included in galaxies. In fact, we think we have found some with Hubble. However, they were most likely born in a galaxy and thrown off in an interaction with another galaxy. The densest concentration of such intergalactic stars is in the Virgo Cluster, 60 million light years away.

Best Regards,
H.F.

more questions and answers


Navigation Strip

PBS Online