light crazy

[Harry]

there's also a PBS TV series made from that

The TV series can in fact be watched online (QT or Realvideo) here:
http://www.pbs.org/wgbh/nova/elegant/program.html

Harald

[maxim]

But once again, how do we know that there's no trace of it left?

That's simple. One often forgets to mention that not only SPACE and TIME is initially created by the big bang, but also the NATURAL LAWS themself. As everything we can experience , measure, detect or compute bases on the constraints the natural laws give to us, there is definitely no trace of anything before the big bang (whatever that means - as time also was created then, there is no 'before') as such a trace won't be part of the existing natural laws and therefore not part of our universe.

What you can do is, to ask: 'Why are the natural laws as they are? Could there be other natural laws?' and then, from that point, try to deduce what could there have been 'before' - but that's pure philosophy.

What else you can do, is try to find an embedding 'room' - a hyperspace - and from there try to get clues of a 'before' or 'outside'- but that's currently also pure metaphysics.

maxim

[Bob Hegwood]

That's simple. One often forgets to mention that not only SPACE and TIME is initially created by the big bang, but also the NATURAL LAWS themself. As everything we can experience , measure, detect or compute bases on the constraints the natural laws give to us, there is definitely no trace of anything before the big bang (whatever that means - as time also was created then, there is no 'before') as such a trace won't be part of the existing natural laws and therefore not part of our universe.

But how do you know that space, time, and the natural laws were
created by the Big Bang? How do you know that they didn't exist before
the Bang, and that what we're seeing in the observable universe today
is all part of an even bigger universe that we can't see yet?

I know I'm beating a dead horse here, but I don't understand how
your statements can be conclusive as facts, when we don't know enough
about the environment we live in to be sure. Certainly the measurements
and observations that we can currently perform give rise to these
theories, but how can we be certain until we do have the
capability to see the edge of the universe?

What you can do is, to ask: 'Why are the natural laws as they are? Could there be other natural laws?' and then, from that point, try to deduce what could there have been 'before' - but that's pure philosophy.

But, so are the current theories involving our "expanding" universe and
all of its contents. Are they not? They are accepted as fact until the next
phenomena occurs to either reinforce what we currently believe, or to
cause a whole new branch of physics to evolve.

At any rate, I appreciate the answer here, my friend. I'm just a guy who
absolutely loves this conjecture.

Take care, Bob

[t00fri]

Was a serious question, and I didn't mean to put anyone off of this topic. I mean, we're looking at such a HUGE event, that we have absolutely no idea what existed before the Big Bang, right?

...

But keep one thing in mind - there technically IS no "before the big bang", because time itself (along with space) was created by the event. Time simply didn't exist before the Big Bang occurred. Neither did space - which means that space is being created as the universe expands. It's not expanding INTO anything.

Precisely that traditional view is widely challenged, as I pointed out in my Cosmology 'summary' post in this thread. Most leading cosmologists (Hawking, Linde,...) & many String theorists are meanwhile advocating a different picture for good reasons.

The great success of String theory in this important context is that the theory appears to remain well-defined close to a space-time singularity like the BigBang! Hence a (mathematical) continuation through that singularity may be explicitly attempted! No reasons for why time has to end/begin there have appeared.

Another way of phrasing (perhaps more intuitively?) what seems to be going on is that close to the BigBang singularity, the dimensionality of space-time 'jumps' back to 10 via some kind of reverse 'compactification' process.

[Reminder: String theory 'natively' lives in 10 dimensions, with 6 'curling up', leaving 4=3+1 for us to live in. The 'curling up' process is called 'compactification'. As a highly oversimplified analogue, think of the three phases of water: gaseous,liquid, solid=ice. At well defined temperatures, a rapid 'phase transition' gas->liquid->ice is taking place. The respective degrees of freedom in each of these phases are very different. A transition of the dimensionality of space-time through 'compactification' also corresponds to a sudden 'freezing out' of (higher-dimensional) degrees of freedom ].

Seen from ten dimensions, the BigBang looks entirely different, however!. The increased number of degrees of freedom in 10 dimensions help to soften the BigBang singularity in a mathematically well-defined manner.

Altogether, a picture of sequential universes with one continuous time seems to prevail. 'Before' a new BigBang the previous Universe with all its energy would be 'crunched'.

[Evil Dr Ganymede]

Yes, but as I understand it right now we have three spatial dimensions and one temporal dimension that are 'unfurled', and six 'curled up' dimensions whose interactions and knots define our physical laws and the way the universe works (there's a name for these 'knots', I want to say Kaluza-Klein but I don't think that's right. IIRC it's a double-barrelled name though, possibly one name begins with L...)

If it really is the cases that the universe is cyclic - that you get a 'big bang' that defines which dimensions are unfurled and which aren't, and that cycles back into a 'big crunch' or whatever that resets it all again, what's the guarantee that the temporal dimension is constant during that transition?

That's why I was saying there was no time before the big bang of the [current incarnation of] the universe. If you want to define a 'meta-time' or 'hyper-time' that defines a sequence of universes folding and unfolding, then there is a 'before' and 'after' - but for THIS specific universe, time started when the big bang happened.

Or are you saying that all universes share the same temporal dimension, and that you really can define a uni-direction sequence of events through several sets of universes? Because that sounds like a bit of a convenient coincidence to me, unless there's something about that one dimension that means it always has to stay unfurled?

To use an analogy, it's like being handed a clock that starts from 00:00:00 at the big bang, which is when our 'local universal time' was unfurled - at which point you start the clock. While one might be able to say that time existed before that point, according to that clock (that represents our timestream) you still can't go back before 00:00:00.

[Bob Hegwood]

Precisely that traditional view is widely challenged, as I pointed out in my Cosmology 'summary' post in this thread. Most leading cosmologists (Hawking, Linde,...) & many String theorists are meanwhile advocating a different picture for good reasons.

Ah, thank you Dr. Schrempp...

Nice to know that there are still some scientists in the world who
don't take everything we think we know about the universe as the gospel.

Aren't FRESH ideas one of the reasons that cosmology has come as
far as it has? Seems to me that - until we know all of the facts
conclusively - then even the wildest speculations may (or may not) be given
some credence.

Thanks very much, Bob

[Evil Dr Ganymede]

Nice to know that there are still some scientists in the world who don't take everything we think we know about the universe as the gospel.

If there's any 'scientist' who thinks that, they don't have any right to call themselves scientists. There is no way that we know everything there is to know about the universe at this stage.

Aren't FRESH ideas one of the reasons that cosmology has come as far as it has?

The advancement of all scientific knowledge is dependent on fresh ideas being proposed and tested. Unfortunately nowadays there's a lot of unecessary politics in science, and "pure science" (without industrial application) is pitifully funded too. It's no way to do science when you're faced with effectively saying "my science is better than their science so please fund mine". There are a lot of people being pushed out of research today and a lot of ideas that could well be very beneficial to science that just aren't making it because of that. But that's a whole different argument.

Seems to me that - until we know all of the facts
conclusively - then even the wildest speculations may (or may not) be given some credence.

So long as they have basis in fact and observation and evidence, that's probably true. But the wildest speculations are the ones that DON'T have that support, and until they do they shouldn't be given credence.

[Bob Hegwood]

If there's any 'scientist' who thinks that, they don't have any right to call themselves scientists. There is no way that we know everything there is to know about the universe at this stage.

I understand that, but even Einstein was considered a radical non-standard
scientist when his proposals were first announced. Was he not?

The advancement of all scientific knowledge is dependent on fresh ideas being proposed and tested.

Isn't that what I just said?

So long as they have basis in fact and observation and evidence, that's probably true. But the wildest speculations are the ones that DON'T have that support, and until they do they shouldn't be given credence.

Did not mean to imply that they should be given credence... All I meant
was that any new idea should not be thrown away simply because
it doesn't conform to the generally-accepted postulates of the time.

If they were, we would not know about the expanding universe
and such things as dark matter and dark energy.

Thanks, Bob

[Evil Dr Ganymede]

I understand that, but even Einstein was considered a radical non-standard scientist when his proposals were first announced. Was he not?

I'm not even sure if there was any warning at all of his ideas... from what I understand (which may be wrong) he basically came out of nowhere with four or five utterly revolutionary papers. I'm not sure he was even IN the scientific community before that (he was working as a patent clerk, don't forget).

Isn't that what I just said?

Actually, no. You said explicitly that cosmology advanced like that. I was just making the general point that all science is supposed to advance this way.

Did not mean to imply that they should be given credence... All I meant was that any new idea should not be thrown away simply because it doesn't conform to the generally-accepted postulates of the time.

Oh, absolutely. All ideas should be considered at least.

If they were, we would not know about the expanding universe and such things as dark matter and dark energy.

Well, the thing with that is that we still don't know what either of the "Dark Stuff" is, but the only way to explain what we observe is to say that SOMETHING is there. And that's OK - we don't have to understand what something is to examine the effects it has on everything. But as it turns out, they were necessary concepts to add to science in order to explain what is observed.

[andersa]

But we know what's happening when we get to the North Pole, and we know why we start going South if we continue on our journey... This probably was NOT the case at some point in the past, because we hadn't learned enough about our environment. That's really all I'm saying here. I don't understand how someone can say that nothing exists outside of our universe if we haven't learned enough about it to make an informed decision.

Whether we know anything about the North Pole or not is besides the point of my analogy. I'm comparing your question "what existed before the Big Bang" with the hypothetical question "what is it like north of the North Pole" (or "beneath the center of the Earth" if somebody prefers that version). People understood the Earth was round long before anybody visited the North Pole, and they realized there could be no such place as "north of the North Pole" since our familiar cardinal directions become meaningless at 90?° of latitude. At that point, "further north" is neither "south" nor "up", but rather "nowhere". It is likewise argued that the familiar directions of space-time (forward-backward, left-right, up-down, and before-after) become meaningless at the Big Bang. Whether this assertion is true is another matter, namely one of finding a cosmological theory that matches scientific observations (or at least doesn't contradict them).

I'm perhaps looking at this from a mathematical rather than astrophysical standpoint, as mathematics knows fewer limits than physics does. We understand three dimensions of space and one of time (the latter being one we can only experience the effects of, not move freely around in). It helps to compare our point of view with that of the Flatlanders, those who live in and understand only two dimensions of "space" (actually a surface to us) in addition to time. The Flatlanders can make observations within their surface only, but not in the (our) third dimension, and still they can tell whether their surface is an infinite plane, a sphere, or some other geometrical shape which we consider three-dimensional.

Now, if we take a sphere and push it through Flatland, the Flatlanders will see a circular object suddenly appearing out of nowhere, expanding fast at first, then slowing down until it reaches its maximum diameter, after which it will gradually contract and eventually disappear completely (with or without an associated puff of smoke). If they can just imagine three dimensions, their scientists can probably explain what happened and even calculate the "volume" (how's that for a weird cosmological concept to a Flatlander) of the sphere.

Then imagine someone living in four-dimensional space (with time as the fifth dimension) doing the same to us. We would watch as a sphere suddenly appears out of nowhere (preferrably far away from Earth, so that we can observe it without being hit by it), grows to a maximum size and then contracts back to nothing. That was a four-dimensional hypersphere crossing our three-dimensional space!

Now some factless speculation: What if the Big Bang is actually the point where a five-dimensional hypersphere first touches a four-dimensional space (the fourth dimension being time) when crossing it, the fourth-dimensional intersection of the two bodies involved becoming the space-time of our universe (rather than appearing in it)? If so, the universe should eventually contract much the same way it is currently expanding, and there will be neither "before" nor "after" the universe, only "inside" and "outside" it (the "inside" part being the one we can observe). If we could build a time machine and travel back to the Big Bang, we may well find ourselves suddenly going forward in time as we pass that point, later ending up in a completely different part of the universe, just as an airplane crossing the North Pole may go from 70?°W to 110?°E in a few seconds. Does my imagination make any sense?

Eventually, we may turn out to consist of pure mathematics, and human intelligence is simply the unintended effect of a mathematical formula trying to describe its greater Self.

[Bob Hegwood]

Now some factless speculation: What if the Big Bang is actually the point where a five-dimensional hypersphere first touches a four-dimensional space (the fourth dimension being time) when crossing it, the fourth-dimensional intersection of the two bodies involved becoming the space-time of our universe (rather than appearing in it)? If so, the universe should eventually contract much the same way it is currently expanding, and there will be neither "before" nor "after" the universe, only "inside" and "outside" it (the "inside" part being the one we can observe). If we could build a time machine and travel back to the Big Bang, we may well find ourselves suddenly going forward in time as we pass that point, later ending up in a completely different part of the universe, just as an airplane crossing the North Pole may go from 70?°W to 110?°E in a few seconds. Does my imagination make any sense?

Yes, I think I see what you mean... Just took me a while to understand
what you were saying here.

Thanks very much for the attempt though.

Take care, Non-mathematical, Bob

[Matt McIrvin]

Some cosmologists have proposed the weird idea that even if space is flat or negatively curved, we could live in a "small" finite universe (that is, small compared to the speed of light times the age of the universe). It wouldn't be hyperspherical, however. Such a universe could be connected to itself like the surface of a torus (a topological torus can be intrinsically flat, if it doesn't have to be embedded in a higher-dimensional flat space); or with some more complicated topology, such as a dodecahedron with opposite faces identified with one another with a twist.

If that were true, then we could in principle look out and see our own neighborhood as it was billions of years ago.

However, I remember Ned Wright saying on his cosmology site that recent observations seem to rule this out... too bad, perhaps, as it was a good, freaky idea.