Whenever you read about looking far back into time to within fractions of a second after the Big Bang (or the latest version of it pertaining to superstring theory) I have to assume they mean from a relative vantage point of someone outside looking at the Big Bang as if it were on TV.
So the universe expands at an enormous rate initially, but does this make sense. If I were somehow a particpant in the big bang, since I apparently would be trzvelling at some close approixmation of the speed of light, would it not seem like fractions of a second, but millions of years?
I am just curious as to what they mean when they talk about fractions of a second after the Big Bang. Can someone dumbify this enough for my feeble mind?
some misc. points…(if I had time, I’d organize these thoughts into a coherent explanation…sorry)
First, when they talk about the early universe (right after the BB), they are talking about time within this universe, not from some outside vantage point. As far as mainstream cosmologists are concerned, there is no outside vantage point.
During the initial expansion, it was space itself that was expanding, it was not matter travelling through space at that speed.
When travelling at near-light speeds, you still perceive time moving at the same rate. The effects of time dilation are only relative to another reference frame. So for you, whether travalling or “stationary”, a second is a second. That participant you mentioned would not be travelling at relativistic speeds, but would instead see the rest of the universe expanding away from him/her at relativistic speeds (just as we see the rest of the universe expanding away from us).
Also note that there were no atoms until long after the initial expansion period of the universe (about 300,000 years IIRC). So there were no participants in this early rapid expansion.
One of the toughest things to realize is that, even when the universe was young & “small”, it was still boundless (infinite in extent).
…somewhere in these jumbled thoughts is the answer to your question. perhaps I can clarify this later.
yknow Tretiak, that is a damn good question. I think we’ll get an answer when Chronos comes around.
Phob, although space itself was (and is) expanding, the early universe was so energetic that any particles were traveling at significant fractions of c.
and if all the particles are moving so fast, the only way to picture that or model it effectively is from a third person point of view. are models of the early universe set in a hypothetical extra-universal reference frame?
I don’t see how current models can be set in extra-universal reference frames, but I’ll check around.
One thing to note, there were no atoms in the early universe, so the “travalling particles” were something like a quark-gluon plasma (or something more fundamental)…which is a state of matter that scientists are only beginning to explore (e.g., experiments at the CERN particle accelerator in Switzerland)
Through the use of telescopes, we can directly see/measure how the universe was back to when it was about 300,000 years old. Beyond that, the universe was opaque to light and (I think) explanations of the younger universe are based on the current understanding of physics & mathematics (i.e., the current laws of physics that we know about allow scientists to piece together what the early conditions were like even though those conditions cannot be directly seen/measured…that is, until we start using neutrino telescopes. Anyway…). The limitation on how far back scientists can accurately talk about is the point where/when our current laws of physics fail. Most notably, some new physics is needed to explain how gravity (spacetime) behaves on a small scale…perhaps this will be a Theory of Quantum Gravity that meshes Relativity and Quantum Mechanics. This same limitation is what keeps scientists from understanding the singularity of a black hole.
short answer…we can see directly far back in time and we can figure things out even farther back in time, but we hit a wall when we approach the first instants of time
Just another quick thought before I hit the books…I think the difficulty is partly in the image of an expanding sphere. Instead one needs to realize that the current expanding space is just as boundless as it was during the initial rapid expansion of energy-filled space. The Big Bang happened everywhere in the universe at once, not at one specific point in the universe. So you need to picture yourself inside the space of the universe & describe the conditions at a specific time.
To answer the question would require a meshing of General and Special Relativity together with Quantum Mechanics. something that is not going to happen any time soon. Stephen Hawking once wrote about an award/commendation/pat-on-the-back he received from the Vatican because his theories fit pretty well into their “Let There Be Light” cosmology. He did not have the heart to tell them of his more recent work in which the Big Bang/Moment of Creation instant itself takes almost an infinity of time to occur. (He didn’t volunteer any details, of which I would not be able to regurgitate anyway.) This removes the need for an act by the Deity, at least of the instantaneous “Let There Be Light” type. It also drags out the timeline you mention in a way that would be impossible to describe outside of singularity-early universe reference frame. It is probably best (ie comprehendible) to use Hawking and Gamow’s theories in a Newtonian time frame.
I’ll risk a near infinite amount of karmic hubris and attempt to clarify Hawking’s theory. The Big Bang process (instantaneous according to an outside observer with a stop watch, which extra universal reference frame, as mentioned above, is not valid) started an infinite time ago but it finished up about 12 billion years ago. At that birth of the Universe, the Big Bang was a semi-infinte event.
Okay then, forget my question (since you have), and let’s deal with what you said.
Not valid? Shouldn’t you qualify that at weast a widdle bit?
Also, please clear up why the amount of “time” taken for the Big Bang process matters at all. Did time begin 12 billion years ago? If so, then how was there time (much less a nearly infinite “amount” of it) before there was time. Or is it a different kind of time? If so, what kind, and what are its attributes?
An extra-universal reference frame would have to be reserved for a Deity. If a theory requires such a reference point, the theorist probably has a bit of an ego. If the use of the word “valid” is not right, how about “legitimate” or “elegant”?
“When quantum mechanics is taken into account, there is the possibility that the singularity may be smeared out and that space and time together may form a closed four-dimensional surface without a boundary or edge, like the surface of the Earth but with two extra dimensions. This would mean that the universe was completely self-contained and did not require boundary conditions … there would not be singularities at which the laws of physics would break down. One could say that the boundary condition of the universe is that it has no boundary.” Stephen Hawking “The Edge of Spacetime”
The implication is that there is no time prior to the creation event but that there is no beginning of time either. From my intra-universe reference point, and handicapped by living in one temporal and three spatial dimensions, the Creation Event takes a semi-infinite (it began an infinite time ago, but ended just before the inflationary phase) amount of time.
During this semi-infinite period, the arrow of time had to run forward in the direction that the Universe would eventually expand. I would PURELY speculate that time would run extremely slow due to the gravitational and energy environment, but that will come out the eventual quantum/relativity synthesis. Maybe if the Observer was outside of all existence, our Universe’s Creation Event might have appeared to be a “What the Hell Was That” instantaneous process.
Lib:
From an Eternal Reference Frame, there is probably no sense of time. But in this universe, we have entropy changes to at least provide a direction, if not an absolute scale to provide a duration, of time progression. (I guess an Eternal Reference Frame must not have entropy.)
I’m still checking around on this. It still seems to me that cosmologists make predictions about the state of the early universe, not by examining its beginning from an outside reference frame, but by examining it from within this universe by rolling back the timeline we can see.
surely a speculation
Just because time & entropy both have one-way, forward-proceeding arrows, I don’t think we can say entropy defines time. Or am I misunderstanding your statement?
I love two things about Hawking’s intellect, its creativity and its honesty. Toward the latter, he uses phrases like “there is the possibility”, “this would mean”, and “one could say”. He seems to understand that, just because all he can see is (part of) his cone, that does not mean that he cannot speculate rationally about other cones.
When physicists talk about the first moments of the Universe, we necessarily do so from the point of view of our Universe, because we don’t know anything about other points of view to say what they might be. If you look at the primordial quark-gluon plasma, or whatever it was, yes, all particles were moving insanely fast, relative to the other particles, but you can still put yourself in the reference frame of any particular particle, in which frame that particleis at rest, and it’s just all the other particles that are moving at Ludicrous Speed. All the theories we have, or at least, all of the well-developed theories, can only take us as far back as T=+10[sup]-43[/sup] seconds, or so… Prior to that time (known as the Planck time), we would need a theory of quantum gravity, which we don’t yet have (String theory and its decendents look like they might be promising, but not one prediction of String Theory has yet been tested, and we may not be able to test them for a very long time). I’d love to explain how we can even extrapolate back that far, but to be honest, I’m still a bit hazy on most of the details myself.
I’m fairly sure that when they talk about the early times of the Universe, that they are simply using time as a convenient paramater for discussion. The Universe right after the Bang itself was a very homogeneous place, so telling you where in the Universe you were wouldn’t really help at that point.
Here’s the idea: we extrapolate the current expansion of the Universe back in time, and based on the Hubble constant (the expansion rate of the Universe now) we can figure how ‘large’ the Universe was at any given previous time – as measured by a method appropriate to whatever geometry you theorize the Universe to have. So you can use the geometry of the Universe to tell time, and I’m pretty sure that this is the kind of time the cosmologists refer to in those timelines – time as determined by the size of the Universe.
As for how they know what the Universe was like at those times, they simply figure what all the mass-energy in the Universe would do if you compressed it into a space the size of the Universe at that time. That’s why the earliest particles we’re theorizing are the ones created in our most powerful accelerators: the early Universe was an EXTREMELY hot place, and the amount of energy floating around was enough to create even the most massive and elusive of particles in their free states (where applicable). Things get very difficult early on because of the quantum uncertainty – as the Universe recedes to a tiny point, we can determine the location of everything in it very precisely, and so our estimates of its energy become very uncertain, allowing for inflation and all sorts of bizarre things.
As for the ‘external observer’ issue – finding a place outside the Universe is impossible by definition, since the Universe is all that exists.
I’m pretty sure Hawking’s take on the entropy-time argument was this: we, as thinking beings, rely for our memories on storage devices that locally reduce entropy at the expense of the general entropy increasing. Since the phenomenon of memory itself is dependent upon entropy-increasing reactions, it follows that we can remember the direction in which entropy DECREASES (we call it the past) but not the one in which it INCREASES (future). So if entropy worked the other way around, always decreasing, we would still be able to remember the times when the entropy was less, and we would flip our time scale appropriately, calling that the past. Thus the second law of thermodynamics is a tautology: of course entropy increases with increasing time, because our concept of past is linked to ‘the time when entropy was less’.
(If that’s not Hawking’s take, please credit it to me, I’ll use it for my master’s thesis =)
Good point. But with things like COBE and BOOMERANG, astronomers/cosmologists are even trying to figure out the heterogeneity of the early universe in order to understand the formations of galaxies, etc.