Expert: James Gort - 4/21/2007

Question
QUESTION: In the book "Death by Black Hole, Dr. Tyson states that at the Big Bank plus 1 second, the universe had grown to several light years across.  He also states the speed of light is the speed limit in the universe.  If the latter is true, wouldn't the universe, after 1 second, be 1 light second across?
ANSWER: Hi Kent,

Very observant!  

I'll have to qualify my remarks with the fact that I haven't read Tyson's book.  Actually, I have many reservations about books such as this and others, including "The First Three Minutes".  Time in the early universe was not only impossible to measure (there were no periodic events such as electron orbits), but there was no one or no instrument there capable of measuring it.  It is not measurable and no predictions can be made from any theory of time passage in the early universe.  It therefore is not in the realm of physics, but rather philosophy.

That said, I'll accept the notion of "one second" - for the sake of this discussion only.  IF we assume the laws of physics were the same then as now (a very questionable assumption!), then we know that the speed of light is a constant.  According to Einstein, it doesn't matter how curved space-time is (i.e., how strong a gravitational field), the speed of light in vacuum is a constant.  If we also accept Einstein, it requires an infinite amount of energy for matter to surpass that speed.  It then follows that in the first "one second" of the early universe, matter could not have expanded past one light-second.  In fact, past one light-second (if we can even speak of it), there was NOTHING - space-time itself did not exist.  After all, the Big Bang was not a "Bang" in the sense of an explosion into something - it was the beginning of space-time, expanding into NOTHING.

To explore one possibility, we might assume that the Big Bang originated with an infinite amount of energy.  This could have caused the early universe to expand at a speed greater than c.  Then, Tyson could be correct.  But this is conjecture only and serves no useful purpose.  

So, without making unfounded assumptions, my opinion is that you are absolutely correct.  Tyson is wrong.  But I'm always open to a correction or a better argument.  If I can be convinced that Tyson has a valid point, I'll change my mind.  But not before then.

Good work!  Keep up the critical thinking.  There is much in cosmology that is accepted on blind faith, rather than sound physical arguments.

Prof. James Gort

---------- FOLLOW-UP ----------

QUESTION: I appreciate your response.  I did not realize A. Einstein left C open to extraordinary forces.  By the way, if we are correct about the extent of the universe after 1 second, it could span 2 light seconds as a diameter.  As a follow up question, if the Big Bang was indeed an explosion as Dr. Tyson and, it seems, others suggest, how do galaxies collide?  He states the Milky Way will collide with Andromeda in a few billion years.  Wouldn't everything fly away from the center in straight lines, not to collide with anything or has gravity altered the courses of galaxies as to make their travels random?
ANSWER: Hi Kent,

To answer the main point of your question, yes, gravity overwhelms the apparent recession of galaxies from one another.  We see many cases of galaxies approaching each other, and some in collision.  It's been postulated that at about 2 million light years, gravity takes over and galaxies start approaching each other.  Coincidentally, the center of Andromeda is about 2 million light years from the center of the Milky Way.  There are other forces in effect, too, such as rotational forces for galaxies orbiting about each other, but the bottom line is that the Milky Way could certainly collide with Andromeda in the future.  Mainly, the interstellar gases would interact, with very few (if any) stellar collisions.

This whole idea about the size of the early universe disturbs me a little.  Size usually implies we're measuring things in 3-dimensional (Cartesian) coordinates.  But the universe was (and is) highly curved in 4 (and possibly more) dimensions.

I also think some confusion stems from the familiar terms of "age" and "expanding".  With the universe, you have to think about those terms differently.

People often speak of a "Big Bang" that occurred sometime in the past.  "The past" implies that we can actually measure time all the way to the event.  And a "bang" implies an explosion of something into something.  Like a stick of dynamite exploding into the air around it.  In that case, the explosion is "somewhere" and we can point and look at it.  Even after it occurs, there's smoke in the direction of the explosion.

Well, the Big Bang (if it actually occurred - there is NOT consensus that it did!) was NOT an explosion or even an "event in time".  It was, in fact, the CREATION of all space and time, expanding "out" into nothingness.  NOT just a vacuum, but NOTHING - no space or time.

So we can't point to a "place" and say that's where it occurred, because there was no space defined.  In fact, it didn't occur "somewhere", it occurred "everywhere" - because all energy which eventually became the matter of our universe was confined within the "bang" itself.  This is a very difficult concept to understand, because it violates our everyday experience.  But there's no such thing as pointing our telescopes in the "direction" of the Big Bang because it was everywhere in the universe.  

If it didn't occur "somewhere", did the Big Bang occur "sometime"?  After all, there was no time defined until the Big Bang.  If we believe the speed of light is a constant since the Big Bang (as Einstein predicts), then energy (light) takes a finite time to reach our telescopes.  The energy has been spreading out into nothing (as space-time itself expands) since the Bang.  So we can look at any direction and see "old energy" or "old light".  If we look at a nearby Galaxy, that "old light" is only two million years old.  But if we look to the furthest places we can, that "old light" is more than ten billion years old.  Theory predicts that the Big Bang (if it occurred) happened between 13 and 15 billion years ago (but we'll never "see" that long ago, because there was no "space" defined yet!). In fact, as we try to see "the beginning" - at 15 billion light years - the galaxies are "receding" at the speed of light.  But that doesn't mean they're actually "speeding away" - in spite of what the popular press would have us believe. It just means that space-time is so curved at that distance that it can be interpreted as a "velocity".  

I know this is all very confusing (it's perplexed the best minds in history!).  But I hope now you can understand why I can't talk about "how fast" we got here from the beginning.  Speed implies movement in space and time, and there wasn't any such thing to measure speed against.  The only thing we can say with some certainty is that space-time itself probably propagated out from the initial "disturbance" at the speed of light (since we now think gravity propagates at that speed).

Since you're so interested and you ask a very profound question, I'm going to recommend a book to you.  There are many books on the popular market, but this one was written by three of the most respected astronomers/cosmologists in the world.  And they have major problems in accepting the Big Bang.  According to these authors, the background microwave radiation at about 2.7 degrees Kelvin (which some people say is evidence of the Big Bang radiation) could easily be accounted for as the remnants of energy created in stellar nuclear fusion.  They argue very convincingly for "continuous creation", whereby matter is being continually created from the universe's energy (and some of that matter decays back to energy).  And the redshift of galaxies (which seems to indicate galaxies are receding from the Big Bang) could have other explanations.  In fact, there are too many problems with the Hubble Redshift that there MUST be other explanations.  That book is "A Different Approach to Cosmology: From a Static Universe through the Big Bang towards Reality" by Hoyle, Burbidge, and Narlikar.

That book gives the entire history of cosmology from 1914 to the present, and they insist that today, many former physicists became cosmologists for the funding, and behave like sheep, blindly following the Big Bang theory.  It requires only first year calculus (in some chapters only).

If you're still interested, I recommend "Seeing Red" by Halton Arp, another very respected astronomer, who insists that galaxies' red shifts do have other explanations - and he describes them in detail.  In particular, he describes how the "accepted" velocity-distance relationship can't be correct.

As a final thought experiment, suppose you built a powerful rocket that could travel near the speed of light.  For the sake of argument, you'll stay close to home (in our own solar system).  As you approach the speed of light, one theory says that you're ACTUALLY approaching the "space-time edge" of our universe!  So the "edge" is not really a PLACE (in this example, the PLACE is in our own solar system), but it is a condition of space-time (at the speed of light, space-time is warped to its maximum, and so this is really the "edge").  That's difficult to put your mind around, because we usually think in three dimensions rather than four.  But taking it one step further, if our rocket ship could somehow surpass the speed of light (with today's physics, impossible, but who knows?), then we would have crossed the "edge" and reached outside of our universe.

I hope I've given you some food for thought.  It's a difficult subject to understand, and many scientists do not agree on an answer.  But always keep an open mind on the subject.

Prof. James Gort

---------- FOLLOW-UP ----------

QUESTION: You have given me much to ponder.  I am a retired mechanical engineer so it is difficult to imagine space being curved and having more than 4 dimensions.  Thank you so much for the thorough and thoughtful responses to my questions.  For years I have wondered if our universe could possibly be but a speck of dust on someone’s desk in another universe.  I suppose that is not so far fetched as I once thought.  My mind is open thanks to you.  Kent

Answer
Hi Kent,

Thanks very much for your kind words.  

In cosmology, I really want to get across there's no consensus by scientists.  There are popular theories, of course, but there's a wide diversity of opinions.

Thanks for giving me a bit of your background.  In answering questions, one usually doesn't know if a grade school student (with limited math skills) or a professional engineer / scientist is doing the asking.  With your background, though, and obvious interest in the subject, I'd like to reiterate the one best book I've found on the subject.  I mentioned it before, but I think the name was cut off.  Written by three eminent cosmologists, it's also very readable.  That book (available from amzon.com or elsewhere) is:      
  
A Different Approach to Cosmology: From a Static Universe through the Big Bang towards Reality by F. Hoyle, G. Burbidge, and J. V. Narlikar.

That book, I'm sure, will do more to open your mind to possibilities.

Cheers,

Prof. James Gort