Stupid Question about the Universe

[Plynck]

In self defense, I am not a real math or science guy, so my knowledge is from books or Nova-like programs aimed at lay-people.

I seem to recall (either from a lecture or from a TV science program) a photograph of some faroff star formations, and the lecturer/announcer stating that we were looking at the remnants of the light of the Big Bang.

Now, I thought that everything, including us (our planet, solar system, galaxy) originated in that Big Bang.

And, I thought that it was fairly well accepted that no matter could travel at greater than the speed of light.

So, my question is this:

How did we get here before the light from the Big Bang?

My guess is that I either heard this incorrectly (although I don't think so), or that this person was misspeaking.

But, if not: My first thought was if two objects travel along a line in opposite directions, each travelling at greater than half the speed of light, their relative speed to one another is greater than the speed of light. However, the Big Bang certainly implies that everything started at a focal point, so aren't we still travelling less than the speed of light relative to that point?

As a side note here, I'm only part-way through Brian Greene's The Elegant Universe, so if this comes up later in the book, unboxed spoilers are okay

best to all,

plynck

[ultrafilter]

There's a theory that at the beginning of time, space was expanding faster than the speed of light. I can't speak to anything more specific than that.

[ftg]

When you look at something x-light years away, you are seeing it as it was x-years ago. So the Andromeda Galaxy (visible with the naked eye) is 2+million light years away and therefore what you are currently seeing is the galaxy as it was 2+million years ago.

If you look at something 10 billion light years away, you are seeing it as it was 10 billion years ago.

If the Universe is 14 billion years old and you look at something at 13+ billion light years away, you are seeing the early cruft of the Universe.

You can't see such cruft near us since the we are only looking back a short time when looking at nearby stuff. E.g., the Sun is only 8 minutes older from our point of view. Hardly a far look back.

[Detonation]

Originally Posted by ultrafilter

There's a theory that at the beginning of time, space was expanding faster than the speed of light. I can't speak to anything more specific than that.

inflationary expansion theory, yes? Suggests that for something like a few millithousandths of a second, just a few millithousandths after the BB, things expanded at a tremendous rate. I don't quite recall if it suggests that things actually moved faster than c though.

[squeegee]

Originally Posted by Detonation

inflationary expansion theory, yes? Suggests that for something like a few millithousandths of a second, just a few millithousandths after the BB, things expanded at a tremendous rate. I don't quite recall if it suggests that things actually moved faster than c though.

IANACosmologist, but my understanding is yes and no: space itself expanded much faster than c, so nothing in space went faster than c. Clear? Yeah, me niether.

[Squink]

Originally Posted by Detonation

I don't quite recall if it suggests that things actually moved faster than c though.

Nope. The things in space are limited to the speed of light. Space itself suffers no such restriction. All those galaxies and quasars and stuff that we see 12+ billion light years of were precipitated out there by the expanding front of space time.

[Mathochist]

Originally Posted by Squink

Nope. The things in space are limited to the speed of light. Space itself suffers no such restriction. All those galaxies and quasars and stuff that we see 12+ billion light years of were precipitated out there by the expanding front of space time.

Also, to say that space "moves at a given speed" is a bit of a misnomer. No point in space moves at all, but the shape of the whole thing changes. The straight-line distance between two points can grow faster than the speed of light, but since no information is being exchanged it's all good.

[David Simmons]

Originally Posted by Plynck

In self defense, I am not a real math or science guy, so my knowledge is from books or Nova-like programs aimed at lay-people.

I seem to recall (either from a lecture or from a TV science program) a photograph of some faroff star formations, and the lecturer/announcer stating that we were looking at the remnants of the light of the Big Bang.

Now, I thought that everything, including us (our planet, solar system, galaxy) originated in that Big Bang.

And, I thought that it was fairly well accepted that no matter could travel at greater than the speed of light.

So, my question is this:

How did we get here before the light from the Big Bang?

My guess is that I either heard this incorrectly (although I don't think so), or that this person was misspeaking.

But, if not: My first thought was if two objects travel along a line in opposite directions, each travelling at greater than half the speed of light, their relative speed to one another is greater than the speed of light. However, the Big Bang certainly implies that everything started at a focal point, so aren't we still travelling less than the speed of light relative to that point?

As a side note here, I'm only part-way through Brian Greene's The Elegant Universe, so if this comes up later in the book, unboxed spoilers are okay

best to all,

plynck

I think what you are talking about is the background microwave radiation which is the red-shifted residual radiant energy from the BB. At the instant of initiation of the BB everything in the universe was at the same place, if you can call a point in space-time a place. This point of radiant energy began to expanded . As things expanded the wavelength of the energy lengthened and it cooled. Eventually some of the energy condensed out as matter surrounded by radiant energy. Expansion continued and continues today and we are still surrounded by the residual radiant energy left after matter condensed out and it now shows up as an electro-magnetic microwave radiation.

[MikeS]

David Simmons has it — dollars to donuts, the "light from the Big Bang" that was being discussed was the Cosmic Microwave Background, which was emitted 300,000 years after the Big Bang. Before that time the Universe was essentially a plasma — electrons and nuclei hadn't joined up to form atoms — and, among other things, this meant that the Universe was essentially opaque to radiation. So the Universe actually had some non-zero size when that light was emitted, and the light we see now as the CMB is that which was emitted at just the right distance from us 300,000 years ago to be reaching us now.

Beyond that, there's the more subtle question of whether it's actually proper to say that everything "sprang from some focal point" in the Big Bang. (Feel free to ignore the following, as I fear I've made it rather unclear.) What General Relativity tells us is that if you could somehow turn time around and watch the history of the Universe thus far in reverse, you would see the Universe getting hotter and denser. At some point the electrons would get stripped from their nuclei by the increasing heat (i.e. the time-reverse of the process described above); as you kept watching, the nuclei themselves would get torn apart into protons and neutrons, and then the protons and neutrons would get torn apart into quarks, again by the increasing temperature. But (here's the important part) GR tells us nothing about the moment of the Big Bang itself, since at that point the Universe was supposed to be "infinitely hot and infinitely dense", and physical theories can't deal with infinities (or at least not without some serious mathematical pyrotechnics, as in QFT, but that's neither here nor there.) All GR can tell us is that if we pick some arbitrarily high density, we can find some time after the Big Bang when the Universe had that density.

It's a subtle distinction, but it means that within the framework of GR we can make a virtue of necessity and view the Big Bang as taking place "everywhere at once", since GR can't tell us anything about the time (if said last time actually existed) when everything was "in one place." Most physicists think that if we ever get a quantum theory of gravity it'll help us understand & hopfully get rid of the aforementioned infinities; but all we have these days in that direction are a couple of theoretically interesting but so far experimentally unverifiable theories.

[cosmosdan]

We found a shortcut that light didn't know about.

Whew! what a lucky break.

[Plynck]

Originally Posted by squeegee

IANACosmologist, but my understanding is yes and no: space itself expanded much faster than c, so nothing in space went faster than c. Clear? Yeah, me neither.

If this is true (if space itself expands faster than c), then that would go a long way to answering my question. My limited understanding about space itself is that it is analogous to a balloon, with everything having a position relative to one another and to the origin. As the balloon inflates, we are increasing our distance from objects in space even while "standing still", simply through the expansion of space itself. Yes? No? Does this then imply that the limitation of c is only with respect to objects relative to one another?

Originally Posted by MikeS

Beyond that, there's the more subtle question of whether it's actually proper to say that everything "sprang from some focal point" in the Big Bang.

Fair enough, using the word "point" was a misnomer. I suggest that we all agree that the size of space/time immediately prior to the Big Bang was 42

My head hurts,

plynck

[Chronos]

The key is that the Big Bang was everywhere. We didn't go from the location of the Big Bang to where we are now, we just stayed put. So we're in the location of the Big Bang. Meanwhile, that light came from somewhere very distant, and that very distant location was also the location of the Big Bang, since the Bang was everywhere.

[aquafight]

maybe it is a reflex from something further from that focal point than Earth. The ligh expanded faster but it might be reflecting and coming back again... can this be?

[aquafight]

nevermind my last post.. im so stupid...

[KlondikeGeoff]

Originally Posted by aquafight

nevermind my last post.. im so stupid...

No, no, don't feel that way. Everything about the BB and most of cosmology is impossible for us (except for a few geniuses) to get our minds around. The singularity of what was there before the BB does not make any sense, as there was NO space, NO time, actually nothing. How can our brains grasp that concept of nothing? Everything we know started with the BB, and will end if, as is one possiblity, the universe will eventually contract back to that one point.

As a humourous aside, the name Big Bang was coined by an astronomer who did not believe in it, and used it as a term of derision. As it was not really a bang at all or an exposion as we know the term, some years ago the astronomy magazine Sky and Telscope decided to have a contest to come up with a better, or more descriptive term.

After thousands of entries, they reluctantly decided that there was no term any better, so gave up. They printed some samples of entries. My favorite was; Bertha D. Universe.

[fortytwo]

Originally Posted by KlondikeGeoff

...
My favorite was; Bertha D. Universe.

A pretty good username?

[David Simmons]

Originally Posted by KlondikeGeoff

As a humourous aside, the name Big Bang was coined by an astronomer who did not believe in it, and used it as a term of derision.

Sir Fred Hoyle, and he should have been more cautious. One of the originators of the BB was George Gamow who was a noted wag. He seldom missed a chance at humor and if the theory turned out to be successful, and so far it is, how better to turn the tables than to adopt the derisive term as the name?

[Plynck]

Originally Posted by Chronos

The key is that the Big Bang was everywhere. We didn't go from the location of the Big Bang to where we are now, we just stayed put. So we're in the location of the Big Bang. Meanwhile, that light came from somewhere very distant, and that very distant location was also the location of the Big Bang, since the Bang was everywhere.

Okay, either this is absolutely true or it is the best whoosh ever

So, continuing along the same line of thought: Given that space and time are inter-related, (and especially given your user name), can we also state that no time has elapsed since the Big Bang?

Originally Posted by KlondikeGeoff

Everything we know started with the BB, and will end if, as is one possiblity, the universe will eventually contract back to that one point.

I had thought that this was now discounted and the Universe was continually expanding? I was a little disappointed to hear this; Asimov had once postulated two symmetrical Universes (he was big on symmetry and balance). He suggested that as one Universe contracted to a point it created another Universe through a Big Bang. Then when that eventually contracted, it would create another Big Bang. Ad infinitum, I guess...

[David Simmons]

Originally Posted by Plynck

So, continuing along the same line of thought: Given that space and time are inter-related, (and especially given your user name), can we also state that no time has elapsed since the Big Bang?

I don't think so. Although the time and space coordinates are interrelated they are not interchangeable. That is, it makes no difference what you call up or, sideways or to and fro. The space coordinates are all equivalent. However none of them is interchangeable with the time coordinate.

Maybe this works. Time increase with increase in entropy. Entropy increases. Therefore time increases.

[DRBOB]

Originally Posted by Plynck

In self defense, I am not a real math or science guy, so my knowledge is from books or Nova-like programs aimed at lay-people.

I seem to recall (either from a lecture or from a TV science program) a photograph of some faroff star formations, and the lecturer/announcer stating that we were looking at the remnants of the light of the Big Bang.

Now, I thought that everything, including us (our planet, solar system, galaxy) originated in that Big Bang.

And, I thought that it was fairly well accepted that no matter could travel at greater than the speed of light.

So, my question is this:

How did we get here before the light from the Big Bang?

My guess is that I either heard this incorrectly (although I don't think so), or that this person was misspeaking.

But, if not: My first thought was if two objects travel along a line in opposite directions, each travelling at greater than half the speed of light, their relative speed to one another is greater than the speed of light. However, the Big Bang certainly implies that everything started at a focal point, so aren't we still travelling less than the speed of light relative to that point?

As a side note here, I'm only part-way through Brian Greene's The Elegant Universe, so if this comes up later in the book, unboxed spoilers are okay

best to all,

plynck

The answer to your question (and many more) is indeed in the second half of Brian Greene's excellent book.

[kniz]

Originally Posted by David Simmons

Maybe this works. Time increase with increase in entropy. Entropy increases. Therefore time increases.

Not that I understood everything I read, but I believe this disproves your relationship between Time and entropy.
Chaos, entropy and the arrow of time

The remarkable conclusion is that equilibrium thermodynamics cannot, therefore, describe change, which is the very means by which we are aware of time. The reason why physicists and chemists rely on equilibrium thermodynamics so much is that it is mathematically easy to use: it produces the quantities, such as entropy, describing the final equilibrium state of an evolving system- Entropy is a so-called thermodynamic "potential"...

To apply thermodynamic principles to far- from- equilibrium problems, Glansdorff and Prigogine assumed that such systems behave like a good-natured patchwork of equilibrium systems. In this way, entropy and other thermodynamic quantities depend as before, on variables such as temperature and pressure.

[Imasquare]

Originally Posted by ftg

If the Universe is 14 billion years old and you look at something at 13+ billion light years away, you are seeing the early cruft of the Universe.

Something bothers me about this, it doesn't seem to add up properly.

At the beginning of the universe, 14 billion years ago, wasn't everything very close together? Nothing was 14 billion light years away from us back then. So how come we are just now receiving light from something 14 billion light years away?

This is something that has bothered me for a while now, but I couldn't find a way to put it into words before I found this thread. I guess I misunderstand something...

[ultrafilter]

Originally Posted by Imasquare

At the beginning of the universe, 14 billion years ago, wasn't everything very close together? Nothing was 14 billion light years away from us back then. So how come we are just now receiving light from something 14 billion light years away?

Because space is expanding.

[KlondikeGeoff]

Originally Posted by Imasquare

At the beginning of the universe, 14 billion years ago, wasn't everything very close together? Nothing was 14 billion light years away from us back then. So how come we are just now receiving light from something 14 billion light years away?

When cosmologists try to explain what happened at the BB, it is astonishing how rapidly everything happened. They construct a timeline showing what's happening every second or so from the start. In a very short time the universe had expanded by a huge amount. By half a billion years, give or take a few , it was immense.

Second, you ask how we "just now receiving the light." We are not receiving it now, but because of Hubble and other powerful telescopes, we are seeing further and further into space. The pictures of these proto-galazies are taken with hugely long exposures through vast clouds of dust and other space debris, and we'll actually never see the light of these on Earth without such techincal help.

Lemme see...to illustrate, you can, with dark skies, just see the Andromeda Galexy and other "faint fuzzies" that are millions of light-years away (a light year being close to 3 billion years). Other galaxies can't be seen with the naked eye a'tall, so actually the light hasn't reached your eyes. With a good telescope, you can begin to see these deep-space objects, because you are penetrating space (which is the same as going back in time).

As one poster noted, it takes light from the sun 8 minutes to reach us. Therefore, the sun you see now left 8 minutes ago. You are looking back in time 8 minutes. OK, the further you penetrate spece with more powerful telscopes, the further back you are going in time, until you get to these places on the other side of the universe, going back, so far, some 13.5 billion years. Hello "space-time."

That clear it up? Well, this stuff is supposed to make your brain hurt.

[David Simmons]

Originally Posted by kniz

Not that I understood everything I read, but I believe this disproves your relationship between Time and entropy.
Chaos, entropy and the arrow of time

It might very well do so but the subject matter is a couple of yards beyond my level. And I guess it depends upon whether or not the universe is a far-from-equilibrium system and that question is maybe 5 yards by me.

[Imasquare]

Originally Posted by KlondikeGeoff

That clear it up? Well, this stuff is supposed to make your brain hurt.

No not really. I understand that the light we see from the sun is 8 minutes old because we are 8 light minutes away from the sun. That part is fine.

But the part that puzzles me is the light we see from objects that are 14 billion light years away. So the light we are seeing left that object 14 billion light years ago, and has travelled 14 billion light years to reach us. But the problem is that surely that object would not have been 14 billion light years away from us 14 billion years ago. So why has it taken 14 billion years for its light to reach us?

Also how did it happen that there is a distance of 14 billion light years between us and these objects? Since at the time of the big bang everything was close together that means that these objects have opened a gap from us of at least 14 billion light years in 14 billion years. In other words they have moved at least at the speed of light.

It is so difficult to put these thoughts into words.

[Kozmik]

I've heard a physicist explain that there was no focal point. The Big Bang did not happen somewhere, it happened everywhere.

[David Simmons]

Originally Posted by Imasquare

But the part that puzzles me is the light we see from objects that are 14 billion light years away. So the light we are seeing left that object 14 billion light years ago, and has travelled 14 billion light years to reach us. But the problem is that surely that object would not have been 14 billion light years away from us 14 billion years ago. So why has it taken 14 billion years for its light to reach us?

Also how did it happen that there is a distance of 14 billion light years between us and these objects? Since at the time of the big bang everything was close together that means that these objects have opened a gap from us of at least 14 billion light years in 14 billion years. In other words they have moved at least at the speed of light.

It is so difficult to put these thoughts into words.

As a matter of fact objects near the edge of the observable universe are moving away at virtually the speed of light. I think the edge of the observable universe has always been moving at near the speed of light. In fact, as I understand it that is what defines the edge. There might very well be galxies, etc. beyond our observable edge but they are outside of our light cone and we can never see them.

[Imasquare]

Originally Posted by Kozmik

I've heard a physicist explain that there was no focal point. The Big Bang did not happen somewhere, it happened everywhere.

That helps makes sense of it.

[Mathochist]

Originally Posted by David Simmons

Maybe this works. Time increase with increase in entropy. Entropy increases. Therefore time increases.

This is.. well, I'm pretty sure that this is ultimately circular. There are definitely huge gaps in our understanding of the various "arrows of time".

[snailboy]

Originally Posted by Imasquare

But the part that puzzles me is the light we see from objects that are 14 billion light years away. So the light we are seeing left that object 14 billion light years ago, and has travelled 14 billion light years to reach us. But the problem is that surely that object would not have been 14 billion light years away from us 14 billion years ago. So why has it taken 14 billion years for its light to reach us?

Actually it was stated that we could see galaxies 13 billion light years away, not 14 billion. If the age of the universe was 14 billion years old, and we could see matter 14 billion light years away, we would be looking at the big bang. That's kind of an interesting concept really because assuming space is at least as wide as the time it has existed (meaning it has expanded at an average speed above that of light thus far), we should be able to see the big bang in a way. The light would be infinitely red-shifted so we couldn't actually see it, but the light would be reaching us. And if space wraps like many scientists believe, meaning if you travelled the diameter of the universe in one direction, you'd end up at your original point, then we can see back to the big bang whether the universe is larger than it is old or not. Isn't that wild? So theoretically we are limited in how far we can look back in time only by how much we can magnify light and how low of frequency we can detect. That's according to my understanding of it anyway.

[Duke of Rat]

The part that gets me is, I hear the age of the Universe given as 14 billion years (or anywhere from 12 to 15 billion). Then the Earth as 4 or so billion, with our Sun at about halfway through it's predicted 8 to 10 billion year life span.

Yet the Earth is at least 2nd generation matter, as the heavy elements have to come from a super nova. So there had to be enough time for matter to coalesce into stars, which had to go through their life cycle and go super nova, then the matter to once again coalesce into a star with planets and age to 4 billion years.

So adding all that up, looks like that first stars had to form pretty quickly after the big bang, not live very long, or both, to have time to fit all of this into a 12 to 15 billion year window. If the Earth and our Sun are 4 billion, that leaves 8 to 11 billion for the Universe to cool enough for a stars to form (I'm not sure how long it takes a star to form) and those stars to age to super nova (not sure what the average age of first generation stars was/is), and then still have time to form our Solar system plus 4 billion years.

Seems to be cutting it pretty close.

[Squink]

Originally Posted by Duke of Rat

Seems to be cutting it pretty close.

This looks like a pretty decent discussion of the timing of star formation:
First Stars
-I'll read it once I get some more coffee in me.

Also
Early Stars Show Universe Grew Up Quickly

The First Stars: Stellar Ashes Reveal Timing of Initial Light

Sooner or later we'll have to come up with a theory where the timing works out exactly right. You can't cut it any closer than that.

[ftg]

Note that since the BB happened Right Here (as elsewhere) we can look Right Here and see some remnants of it. This is the Cosmic Microwave Background Radiation. However, it's only 2.7K so not all that noticable. If you look 10 billion light years away, you'll see the CMBR from 10 billion years ago, and since the Universe was denser and warmer, the CMBR will be a few degrees higher. Still no big whoop. But if you look even farther away, where the distance corresponds to the near beginning of the Universe, then the CMBR starts getting truly hot and the Physics gets interesting (and even bizarre).

Yes, you can look in the immediate vicinity and see evidence of the BB. In fact, the discovery of the CMBR helped move the BB theory up in stature. A couple Nobels were awarded for it. (I've personally heard one of the winners give a lecture, but on computer stuff. He should stick to what he knows.)

[Chronos]

We now know that the Universe is 13.7 billion years old, to within plus or minus a percent or so. But this was a very recent measurement; up until a couple of years ago, the best estimate ranged from 10 to 20 billion years, so it's not surprising if anyone remembers a fuzzier figure.

And the key to stellar generations is that big, hot, bright stars burn out far more quickly than do small, cool, dim ones. The Sun will have a total lifespan of about 10 billion years, but a very massive star might only live for a few million, plenty of time for several generations of massive stars before the Sun. Meanwhile, a very small red dwarf might live for hundreds of billions or even trillions of years.

[David Simmons]

Originally Posted by Mathochist

This is.. well, I'm pretty sure that this is ultimately circular. There are definitely huge gaps in our understanding of the various "arrows of time".

Right. I think maybe entropy wasn't a good choice for the job. I've always looked at entropy as a bookkeeping device that allows the use of the 1st Law in working out thermodynamic problems. I fail entirely to see any practical difference between energy becoming unavailable and its being destroyed. By using the idea of entropy we can say that the total system energy is constant, which is useful, but that some of it is just "unavailable."

As to circularity. Sure. I think everything we think we know is ultimately based on a few assumptions that can only be proved in terms of each other. Euclid called them "common notions." The thing to do is just put your head down and keep going. As a homely similie, it's like a pig caught under a gate. He just squeals like hell and keeps plowing ahead. It ain't elegant but it gets him where he wants to go. Just call me a cockeyed pragmatist. We need more Oliver Heavisides.

[Mathochist]

Originally Posted by David Simmons

Right. I think maybe entropy wasn't a good choice for the job. I've always looked at entropy as a bookkeeping device that allows the use of the 1st Law in working out thermodynamic problems. I fail entirely to see any practical difference between energy becoming unavailable and its being destroyed. By using the idea of entropy we can say that the total system energy is constant, which is useful, but that some of it is just "unavailable."

Actually, entropy is quite a useful idea, and very well-founded once you stop thinking about thermodynamics and start thinking about statistical mechanics. Basically, it measures how "big" a region in the phase space of the system is.

For instance, consider two rooms connected by a hall with N gas molecules between them. Also, throw out all the information but which molecule is in which room. That is, the state of a given molecule is in the set {A,B}, and so the space of states is {A,B}^N. Now, since the molecules are all the same, the system is symmetric under the action of S_N which permutes the molecules.

The entropy is essentially the logarithm (we'll use base 2) of the size of each S_N-orbit. Say N=4. The state (L,L,L,L) is the only state in its orbit, so the entropy is log(1) = 0. On the other hand, (L,R,L,R) "looks like" five other states, so its entropy is log(6).

[Mathochist]

um, switch "A,B" for "L,R".

[rowrrbazzle]

Originally Posted by David Simmons

Sir Fred Hoyle, and he should have been more cautious. One of the originators of the BB was George Gamow who was a noted wag. He seldom missed a chance at humor and if the theory turned out to be successful, and so far it is, how better to turn the tables than to adopt the derisive term as the name?

As an informational aside, Hoyle used the phrase on radio and said it was a visual analogy, not derision. See my post here: http://boards.straightdope.com/sdmb/...77#post6187777

[rwjefferson]

Originally Posted by Mathochist

This is.. well, I'm pretty sure that this is ultimately circular. There are definitely huge gaps in our understanding of the various "arrows of time".

How about "Time is Entropy"
rwj

[Squink]

Originally Posted by rwjefferson

How about "Time is Entropy"

How about "the change in entropy = the change in heat content, divided by the temperature"?
Wiki on Entropy

Time = k (Ln Omega) also sounds very silly.