Space and Time

[Resha Caner]

Based upon the warm-hearted advice of those whose wisdom exceeds mine, I've moved this question into a new thread.

As succinctly as I can state it, here is the question - or series of questions. As I understand it, after the Big Bang, the universe was expanding faster than the speed of light. That doesn't mean material was moving faster than the speed of light, but that "space" (whatever that is supposed to mean) was expanding faster than light. So, suppose a "thing" (I don't know what the bits of energy, matter, or whatever are technically called for the early universe model of the Big Bang) emits some light at time t1. By time t2 the space between the emitted light and the thing has expanded at a rate faster than light can travel. So is there anything in the expanded space? Is it filled with light, is it empty, or is there something else?

FYI, not trying to lay any trap as if I think I've uncovered a flaw or something. It's an honest question of curiosity. I enjoy the mind games of space and time. So, after dispensing with this question, if someone would like to play in my sandbox and discuss other aspects of space and time, I'd enjoy the company. I might even loan you a shovel.

 

[Rilke's Granddaughter]

Based upon the warm-hearted advice of those whose wisdom exceeds mine, I've moved this question into a new thread.

As succinctly as I can state it, here is the question - or series of questions. As I understand it, after the Big Bang, the universe was expanding faster than the speed of light. That doesn't mean material was moving faster than the speed of light, but that "space" (whatever that is supposed to mean) was expanding faster than light. So, suppose a "thing" (I don't know what the bits of energy, matter, or whatever are technically called for the early universe model of the Big Bang) emits some light at time t1. By time t2 the space between the emitted light and the thing has expanded at a rate faster than light can travel. So is there anything in the expanded space? Is it filled with light, is it empty, or is there something else?

FYI, not trying to lay any trap as if I think I've uncovered a flaw or something. It's an honest question of curiosity. I enjoy the mind games of space and time. So, after dispensing with this question, if someone would like to play in my sandbox and discuss other aspects of space and time, I'd enjoy the company. I might even loan you a shovel.

During the initial inflationary period, space was filled with quarks, anti-quarks, and gluons. It's only after the inflationary period that other stuff, like photons started appearing.

Caveat: IANAP. Brains are my bag.

 

[Resha Caner]

During the initial inflationary period, space was filled with quarks, anti-quarks, and gluons. It's only after the inflationary period that other stuff, like photons started appearing.

Are you saying that it is only after the expansion rate has dropped to less than the speed of light that light appears?

 

[Rilke's Granddaughter]

Are you saying that it is only after the expansion rate has dropped to less than the speed of light that light appears?

Sort of. Let me think of a clearer way to phrase it.

 

[GrowingSmaller]

So is there anything in the expanded space? Is it filled with light, is it empty, or is there something else?

AFAIK, but I am not really qualified to teach, no space is empty. Vaccuum energy / Zero point energy.

 

[Resha Caner]

AFAIK, but I am not really qualified to teach, no space is empty. Vaccuum energy / Zero point energy.

Interesting, because that question would have come up sooner or later. If space is the absence of everything physical, how can we measure whether it is expanding or not? There has always been this sense that space-time was a return to ether theories.

But maybe we should save that for later. At present I'm willing to accept my simplistic statement as a crude approximation: light doesn't exist until expansion drops below the speed of light. Given that, what is the first thing to appear after the Big Bang that remains in our current universe?

 

[Rilke's Granddaughter]

Interesting, because that question would have come up sooner or later. If space is the absence of everything physical, how can we measure whether it is expanding or not? There has always been this sense that space-time was a return to ether theories.

Not at all. space-time is the antithesis of ether theories. We measure not the space itself, but the objects embedded in that space. Hubble is the man to look up; and the Hubble constant. Galactic red-shift is the critical clue to the expansion.

But maybe we should save that for later.

Why? It's a fascinating topic.

At present I'm willing to accept my simplistic statement as a crude approximation: light doesn't exist until expansion drops below the speed of light. Given that, what is the first thing to appear after the Big Bang that remains in our current universe?

That's not quite correct. You're presuming that the electroweak epoch and the expansion epoch don't overlap; there is some debate about that point.

And the answer to your question is... everything. Bosons, primarily, of course.

 

[Resha Caner]

It's only after the inflationary period that other stuff, like photons started appearing.

And the answer to your question is... everything.

Hmm. Maybe I need "Big Bang for Dummies", because these two answers sound contradictory to me.

 

[Rilke's Granddaughter]

Hmm. Maybe I need "Big Bang for Dummies", because these two answers sound contradictory to me.

The gluon/quark cloud formed into matter & energy - all that exists. It's like saying at that time X we had ingredients and at time Y soup.

 

[Resha Caner]

The gluon/quark cloud formed into matter & energy - all that exists. It's like saying at that time X we had ingredients and at time Y soup.

OK. It seems to me you're stating a conservation principle here. If someone gives me a lump of clay, I consider it a lump of clay, not a vase. The amount of material may not change, but its form does. I assumed conservation was postulated here. But what I hear you saying is that nothing took the form of light until the rate of expansion dropped below the speed of light.

Maybe I should try to drive on. I'm leading up to asking if "space" is anything more than the distance between one bit of stuff and another bit of stuff. If so, the extent of space would be nothing more than the largest distance between the farthest separated bits of stuff. Or, when we get into talking about curved space, is there something (other than the material in the space) that is actually curved?

I never thought Einstein was claiming some actual ether that curved, but merely that curved space-time was a convenient model. However, maybe the view is different now.

 

[KCfromNC]

OK. It seems to me you're stating a conservation principle here. If someone gives me a lump of clay, I consider it a lump of clay, not a vase. The amount of material may not change, but its form does. I assumed conservation was postulated here. But what I hear you saying is that nothing took the form of light until the rate of expansion dropped below the speed of light.

Sort of, but they have nothing to do with each other. Inflation lasted a small fraction of a second, but the universe was opaque for several hundred thousand years. There were photons but they were quickly scattered by free particles so the light didn't travel far - so the universe wasn't mostly transparent like it is now. Once the universe cooled enough for atoms to form the scattering stopped and the universe looked a bit more like we're used to today.

The cosmic microwave background radiation is made up of those first photons not to be scattered into nothingness (red-shifted by a significant amount). That might be what you're looking for here - those photons have been in flight since about 400K years after the big bang.

Maybe I should try to drive on. I'm leading up to asking if "space" is anything more than the distance between one bit of stuff and another bit of stuff. If so, the extent of space would be nothing more than the largest distance between the farthest separated bits of stuff.

I think you're confusing space (the final frontier...) with space-time as a GR concept. Space (the stuff astronauts fly around in) has stuff in it. Space-time, in a GR sense, is a way to describe the specifics of how everything isn't in the same place or at the same time. Two different concepts with (sort of) the same name.

I never thought Einstein was claiming some actual ether that curved, but merely that curved space-time was a convenient model.

Everything in science is a convenient model, so I'm not sure what you mean by the distinction you be looking for.

 

[Resha Caner]

I think you're confusing space (the final frontier...) with space-time as a GR concept ... Everything in science is a convenient model, so I'm not sure what you mean by the distinction you be looking for.

Thanks for the explanation, that helps. But no, I'm not thinking of "outer space" in terms of a weekend SF festival. I'm thinking of it in terms of Cartesian Space or Hilbert Space or the other mathematical constructs.

I am then asking: is space-time just a model or does it correlate to something physical? If I could take all the stuff out of space-time (or at least clear a small section of it), is there something I could measure within that empty space-time?

 

[Rilke's Granddaughter]

Thanks for the explanation, that helps. But no, I'm not thinking of "outer space" in terms of a weekend SF festival. I'm thinking of it in terms of Cartesian Space or Hilbert Space or the other mathematical constructs.

I am then asking: is space-time just a model or does it correlate to something physical? If I could take all the stuff out of space-time (or at least clear a small section of it), is there something I could measure within that empty space-time?

I think the point is that there's no such thing as "empty" space. Try looking up "vacuum energy".

 

[Rilke's Granddaughter]

OK. It seems to me you're stating a conservation principle here. If someone gives me a lump of clay, I consider it a lump of clay, not a vase. The amount of material may not change, but its form does. I assumed conservation was postulated here. But what I hear you saying is that nothing took the form of light until the rate of expansion dropped below the speed of light.

Maybe I should try to drive on. I'm leading up to asking if "space" is anything more than the distance between one bit of stuff and another bit of stuff. If so, the extent of space would be nothing more than the largest distance between the farthest separated bits of stuff. Or, when we get into talking about curved space, is there something (other than the material in the space) that is actually curved?

I never thought Einstein was claiming some actual ether that curved, but merely that curved space-time was a convenient model. However, maybe the view is different now.

There is no "ether". And the curvature is due to the matter in that space; no matter, no curvature. But space isn't exactly empty - because of quantum effects, you can make the argument that an electron (f'r example) is everywhere in space - it's just more likely in certain spots. In fact, vacuum energy is exciting because it's the basis of Hawking Radiation and the potential evaporation of Black Holes. Fun stuff.

 

[Resha Caner]

I think the point is that there's no such thing as "empty" space. Try looking up "vacuum energy".

There is no "ether". And the curvature is due to the matter in that space; no matter, no curvature.

OK, if you insist. FYI, I pondered a fun little game, but decided not to do it. Ether was postulated as the medium through which light travels. Given that my glance at vacuum energy stated that one effect connected to it is spontaneous emission ...

Have you ever played the "grue" game?

As for curvature, my understanding matches with what you said, but I wanted to confirm that. In that regard, I worked for a time on a theory for mechanics related to material behavior at the macro level. But, it got to the point where I couldn't push it forward from my ivory tower nor could I convince anyone to help me pursue it. So, it sits on my shelf as a lovely idea.

But space isn't exactly empty - because of quantum effects, you can make the argument that an electron (f'r example) is everywhere in space - it's just more likely in certain spots.

Sure. I was aware of that, and wondered if the "there is no empty space" position would lead to this. The one electron theory is always a fun one.

If there isn't more to say about that (I'm sure I could spend my life extracting details, but I refer specifically to issues of empty space and the emergence of light after the bang needed for this thread), I had a question about time.

 

[Rilke's Granddaughter]

OK, if you insist.

I insist because that's what the scientific research indicates. The ether was whacked by Michelson and Morley; vacuum fluctuation is old news.

FYI, I pondered a fun little game, but decided not to do it. Ether was postulated as the medium through which light travels. Given that my glance at vacuum energy stated that one effect connected to it is spontaneous emission ...

Your point?

Have you ever played the "grue" game?

Nope.

As for curvature, my understanding matches with what you said, but I wanted to confirm that. In that regard, I worked for a time on a theory for mechanics related to material behavior at the macro level. But, it got to the point where I couldn't push it forward from my ivory tower nor could I convince anyone to help me pursue it. So, it sits on my shelf as a lovely idea.

Um, OK.

Sure. I was aware of that, and wondered if the "there is no empty space" position would lead to this. The one electron theory is always a fun one.

Um, OK.

If there isn't more to say about that (I'm sure I could spend my life extracting details, but I refer specifically to issues of empty space and the emergence of light after the bang needed for this thread), I had a question about time.

Tick, tock.

 

[Resha Caner]

Your point? ... Nope. [haven't played the grue game]

It comes in many forms. The idea is to disconnect the logic from the meaning we associate with the words. Nelson Goodman is who introduced the "grue" version. It's a good way to test oneself and see whether your understanding is based more on the logic or more on the meaning of the words and the associated intuitions.

With respect to ether vs. vacuum energy, I understand that you see a difference in the details. And I'm not trying to say the vacuum energy model doesn't work. It just reminded me of Gertrude Stein, "Rose is a rose ..." So I imagined something where we would play with the conceptual levels of these two to check their similarities.

Um, OK.

With respect to my own scientific machinations, I was hoping you would jump in and offer me a multi-million dollar grant to pursue my idea. No? Hmm. I'd be happy to sit in the corner of some office near the collider and pretend like I was looking for bosons.

Tick, tock.

The official BIPM definition of a second is based on the caesium atom. How does the bang define time, given that caesium didn't exist at that moment? Is there a steady motion to use as a reference?

 

[JonF]

As succinctly as I can state it, here is the question - or series of questions. As I understand it, after the Big Bang, the universe was expanding faster than the speed of light. That doesn't mean material was moving faster than the speed of light, but that "space" (whatever that is supposed to mean) was expanding faster than light. So, suppose a "thing" (I don't know what the bits of energy, matter, or whatever are technically called for the early universe model of the Big Bang) emits some light at time t1. By time t2 the space between the emitted light and the thing has expanded at a rate faster than light can travel. So is there anything in the expanded space? Is it filled with light, is it empty, or is there something else?

Physics is by no means my area of study. But “space” the way you use it, is a concept, not a physical object. Also you are equivocating the blue words with the red word, and they have different meanings.

 

[Resha Caner]

Physics is by no means my area of study. But “space” the way you use it, is a concept, not a physical object. Also you are equivocating the blue words with the red word, and they have different meanings.

I got the answer I needed for space. I was waiting to see if anyone knew the answer to the question about time.

 

[Rilke's Granddaughter]

It comes in many forms. The idea is to disconnect the logic from the meaning we associate with the words. Nelson Goodman is who introduced the "grue" version. It's a good way to test oneself and see whether your understanding is based more on the logic or more on the meaning of the words and the associated intuitions.

With respect to ether vs. vacuum energy, I understand that you see a difference in the details. And I'm not trying to say the vacuum energy model doesn't work. It just reminded me of Gertrude Stein, "Rose is a rose ..." So I imagined something where we would play with the conceptual levels of these two to check their similarities.



With respect to my own scientific machinations, I was hoping you would jump in and offer me a multi-million dollar grant to pursue my idea. No? Hmm. I'd be happy to sit in the corner of some office near the collider and pretend like I was looking for bosons.



The official BIPM definition of a second is based on the caesium atom. How does the bang define time, given that caesium didn't exist at that moment? Is there a steady motion to use as a reference?

The definition of a second is merely a specific measure of time. Time remains, mathematically, a fourth dimension in the General and Special Relativity equations. The bang doesn't define time.