The Big Bang Was an Explosion of Space, Not in Space

[mojuba]

Except the Big Bang theory doesn't say there was a moment of time zero, the "moment of creation" before which there was nothing. This is a popular misconception about the BBT which is driven by our religious beliefs: there was nothing and then something caused something. BBT in its modern form approaches very dense and very hot moments of the Universe, but doesn't say anything about "creation".

[thmz]

"since space and time are interconnected"

Last week I saw a Ted Talk by Prof. dr. Wubbo J. Ockels telling me that space and time are not connected. http://www.tedxamsterdam.com/2009/video-wubbo-ockels-on-time...

The more I read and hear about space the more I get the feeling we don't know nothing about it...

[zppx]

General relativity remember? In which the spacetime is a simple manifold (okay, not so simple), if Einstein's theory is right or wrong in such a large scale (the entire universe) we must confirm or reject this with experiments, but I see Ockels's theory as some form of solipsism that does not mix comfortably with my worldview.

But I agree with you, we do not understand the nature of space.

[Detrus]

The flying spaghetti monster said "let there be light," and there was light. Then light instantly reached all the corners of the singularity. And he said "whoopsiee, gonna have to edit that out." So he moved a slider on his touch screen to change the properties of dark energy and there was the big bang, and obviously light intensity was another slider.

[petercooper]

Dr. Pamela Gay and Fraser Cain (of Universe Today) covered this topic really well on their awesome Astronomy Cast: http://www.astronomycast.com/astronomy/the-big-bang-and-cosm...

Their "What is the universe expanding into" episode went further: http://www.astronomycast.com/astronomy/episode-28-what-is-th...

I've been listening to an episode of Astronomy Cast every night for the past two years now - can't get enough of it :-)

[tfh]

From what I understood it's like this:

  class Universe:
    def __init__(self)
        self.time  = []
        self.space = []

  our_universe = Universe() # <== Big Bang

[jgg]

Wrong, God wrote in Lisp: http://www.gnu.org/fun/jokes/eternal-flame.html

[rvanrooy]

without a compiler

[goodside]

I'm not convinced this explanation-by-analogy style is really all that helpful, particularly with regards to "the big bang is an expanding balloon". What makes it such a confusing analogy is that most people were already picturing something like an expanding sphere anyway, just one filled uniformly with matter moving away from a central point as it expands. And it doesn't reinforce that the Universe has no center, since most people can easily imagine what the center of a balloon is.

So, screw the analogy. Here's what we know.

Right now, everything is moving away from us in proportion to its distance from us. Read that again, because that's the fundamental observation. The usual intuitive view that lay people have is that we're drifting away from the Big Bang on inertia left over from the explosion. This would not result in what we see. For everything to move away from us in direct proportion to its distance, everything would have to be speeding up all of the time. When we're distance d from the Big Bang, we're drifting away from it at half the speed that we are when we're distance 2d away. Inertia doesn't do that. So much for inertia.

Maybe it's not inertia, but some kind of Magic Inertia that we don't understand? A kind that pushes things faster and faster as time goes on, like little angels perpetually flapping their wings to add momentum to every atom. That's great for a while, but you hit another problem: the speed of light. If you're already moving away at (nearly) light-speed, you can't double your speed. Doubling your momentum will just give bring you infinitesimally closer to light-speed. D'oh.

So what is the answer? The closest you can get without worrying about math is probably this: Space is being created, and distance is somehow being inserted in the gaps between everything, and this happens continuously and everywhere. The other, more accurate, way to see it is that the meaning of "distance" and "duration" (that is, the metric we use to determine the distance between points, both in space and time) is itself changing as the Universe expands.

This results in some observables that cannot be explained otherwise, and which we do actually observe. In this model, everything (at intergalactic distances) does indeed increase its distance from everything else, and in direct proportion to the original distance. Since this is a change in the spacetime metric, rather than actual movement within spacetime, it does not result in relativistic effects that you would see if it were literal movement. There are galaxies in the sky right now whose distance from us is literally increasing at a rate that would be impossible if it were due to movement, since it would require movement faster than the speed of light. That's the clincher--the reason no other model can possibly work.

This "metric expansion of spacetime" maybe sounds like a cop-out, like something's been invented just to explain the Big Bang, but it hasn't. This is exactly what matter does in the normal scales of planets and stars. The changing of the spacetime metric is what gravity fundamentally is, as Einstein explained with General Relativity. It's the reason clocks run slower on Earth than they do in space, and it's the reason the planets stay in their orbits. It's all really just quite ordinary.

[jerf]

"I'm not convinced this explanation-by-analogy style is really all that helpful, particularly with regards to "the big bang is an expanding balloon". What makes it such a confusing analogy is that most people were already picturing something like an expanding sphere anyway, just one filled uniformly with matter moving away from a central point as it expands. And it doesn't reinforce that the Universe has no center, since most people can easily imagine what the center of a balloon is."

The key to the balloon analogy is that it only applies to the surface. The interior of the balloon is to be ignored. You say you can easily find the center of the balloon, so I think you don't get this, because I suspect your "center" is the 3D center of the balloon. But that doesn't exist. Only the surface does. What's the central surface point of a sphere? There isn't one. That's the universe, only the surface is 3D, not 2D.

I'm fairly sure that even a large number of people using the "expanding ballon" metaphor don't get that, let alone the poor readers. I tend to be surprised when I see it explained correctly.

Also, in the classic picture of the wormhole, like you might find here: http://casa.colorado.edu/~ajsh/schwm.html , the wormhole is not the tunnel itself. If you see someone drawing an arrow that goes down the middle of the tunnel as the path of travel, they don't know what they are talking about. (That's the best picture I could find quickly, they're actually showing something else with that arrow, so I do not accuse them.) The wormhole is the sides; the image is two 2D chunks of space being connected through a 3rd dimension. (Incidentally you can tell Hollywood doesn't know either, because they always actually "draw" the wormhole.) The curvature of the 2D planes corresponds to gravity in these displays.

This is also true of the classic "rubber sheet" gravity analogy; the rubber sheet applies only to 2D, and the 3D "things" usually drawn should be understood to be merely labels explaining where the curvature comes from. You really shouldn't see a "rolling ball" on the surface, you should see it in the surface. Again, this is done incorrectly far more often than it is done correctly.

[boredguy8]

With my limited cosmological understanding, it seems like much of what you're saying is also key to, in part, understanding that the expansion or shift isn't a movement THROUGH spacetime, but the expansion OF spacetime.

I have a question. Our current cosmological understanding indicates that no matter where you are in the universe, you'd see this recession, correct? If so, bizarre thought experiment: If I could somehow magically teleport from here to the very edge of observable spacetime, wouldn't I see, broadly, the same stuff as I see from earth? A whole bunch of receding galaxies?

[mojuba]

Plus, we still aren't 100% sure if the red shift is due to the Doppler effect, or something else and then the Universe is not expanding at all. I always found it strange that there is such a simple and straightforward correlation between distance and speed. It should have been more complicated than that, shoudln't it?

[gnosis]

"Right now, everything is moving away from us in proportion to its distance from us."

From us? So does that mean that we are at the center of this expansion?

[erikstarck]

The Big bang was a highly unlikely event made possible by the fact that time didn't exist before it happened - thus the whole concept of probability over time falls apart. Or maybe of all unlikely events it was the most likely one to occur.

In any case I think it's fascinating that tiny creatures such as ourselves can think thoughts like this. The universe is clearly using us to understand itself.

[mojuba]

> time didn't exist before it happened

Do you see what's wrong here? If there was no time, there could be no "before". Besides, if you are talking about probabilities of something to occur, that means there was some cause of that event, and that in turn implies there was time before time started (?) because causes and effects occur in time.

These things have nothing to do with the Big Bang theory anyway, let alone all this kind of speculations make little or no sense.

[nfnaaron]

"The universe is clearly using us to understand itself."

We are [part of] the universe. The universe is trying to understand itself.

[Jeema3000]

It may be easier to just conceptualize it as a singularity that was always existing and always exploding in a single, simultaneous moment of time.

Then again maybe not... :)

[sigzero]

That doesn't really change any arguments on either side at all does it? "OF" space? Where did that space come from? etc. etc. etc.

[zppx]

Well, no model of big bang cosmology says something about how energy came to exist in this space as well, and based on the principle of mass-energy equivalence we do not know how stuff came to exist. It is important to keep in mind that the Big Bang cosmology was a theory originally described by a catholic priest (Georges Lemaître), this theory is closer to theism than its direct (academic) competitor in the past, the steady state cosmology, that predicted an eternal universe, basically it says that time and space existed since forever, in which new matter is created every moment.

[bartl]

Oh, man, good article, but the page that the word "win" links to, in the last paragraph, is just ridiculous.