Friar Bellows

I'm not sure I understand your bubble idea (I only understand things in pictures ) but the effect of this postulated "exotic form of energy" is nothing more than "an acceleration due simply to gravity". In other words, the presence of this so-called dark energy may require some exotic physical theory, but its effect on the expansion of the universe can be easily described by the good old Einstein field equations. As I'm sure you're aware, gravity may be "repulsive" as well as "attractive".

Answerer

Joe, I got the feeling that the universe may contract rather than accelerate in the future. Anyway, who knows?

joedad

That was always my opinion as well. I even had heard that the expansion was slowing down, though I can't recall the sources just now. But to hear that the expansion is accelerating was a surprise to say the least.

I cannot recall the program, but could probably find a link. But anyway, the speaker tossed something into the air and of course it fell back down. 'Imagine," he said, "that it continues to travel upwards, and not only that but accelerates away from us.' That's a paraphrase btw. So, that really struck me and I was simply thinking about why that would be so, without violating what we know about gravity, or inventing new exotic forces, not that these are not distinct possibilities.

And so I thought of a bubble, where material density is greatest at the edges, like a 'hollow' sphere. Anyone or anything located inside would see the 'inside' rushing away towards the periphery, and accelerating the closer it came to this 'edge.' And of course, who's to say that the cosmos isn't filled with these universal 'bubbles?'

It seems strange that enough energy could be contained in a closed system that this acceleration would occur, so I was simply trying to construct a mass either outside or nearly outside the system itself to account for the accelerating expansion despite gravitaty.

But I have a hard time trying to understand spacetime itself. I think of the universe as an expanding solid, so I sit back and look at objects around me and wonder about their place within this 'spacetime' and think of them similarly. Are they expanding with the rest of the unvierse? Seems a strange thought.

Also, the whole idea of motion is intriguing. All energy comes down to being motion and nothing more. That doesn't explain much, because we still have not explained the nature of motion. It's just damn interesting.

joe

Answerer

Thats why I think some scientists called those energy that are responsible for the acceleration of the universe 'dark energy'. Anyway, one of the reasons that I don't think the universe will accelerate or stretches to infinite is because it will take an infinite amount of energy just to do that(which seem impossible for universe to do that). Unless, of course, just as you had said there are others universes outside our own universe that is truly the one responsible for causing those 'dark energy' to be there in the first place. But then again, if there are really universes outside our own, it must be very far away from us, otherwise, our universe would have accelerated increasely from the very beginning of the big bang.
Unlike some of my peers and some people here, I tend to view spacetime as some non-ideal fluid with a very high degree of viscosity. Fluid is a good analogy than rubber because it has both particle and wave like properties in it.
The problem is I don't know if spacetime is really behaving like solid and have an elastic limit of its own. Perhaps, you guys, had already know the answer to my problem.

Sidian

i'm fairly ignorant of big bang theory compared to many on this board.

am i right to assume that when we measured other galaxies moving away from us we took into account that our position is also moving at high speed? depending on what time of day it is, where in the year we are, where our solar system, and even where in our galaxy our solar system is, we are moving at very different speeds.

it would seem very difficult to judge the difference between our galaxy moving away from another galaxy and our planet moving away from another galaxy.

if we are taking measurements of motion from a moving platform and still all indications show everything moving away from us, certainly the universe is expanding. but how much faster are things expanding in the direction we are heading?

if we were in a car, and ahead of us there was a car pulling away and behind us is a car from which we are pulling away, traffic is then expanding...right? but at what speed are they traveling? is this even determinable in our universe?

but for everything to be moving away from us in all directions and for us to have no celestial systems traveling "alongside" us seems very unlikely...is this the case?

i'm always skeptical of discoveries. especially the big bang theory as alot of other thoery bending has been accomplished to comply with this origin.

Starboy

I am by no means an expert or even all that knowledgeable but for what it is worth what little I know is as follows:

The amount of energy/mass in the universe is considered to be a constant. All of the energy that exists now was present at the big bang. Supposedly that energy existed in a space smaller than a dime. Initially all the energy was supposed to be in the form of photons. In such an energetic and dense collection of photons it would be impossible for any mass to exist. As soon as it came into existence it would be obliterated. The initial spot of photons expanded, as it expanded it cooled. As some point quarks could form and persist, then protons and neutrons and electrons, soon simple ionized atoms formed. All the while the universe continues expanding. As things cooled further the atoms collected as clouds of gas. These clouds condensed further forming stars which in turn forming small galaxies. These small galaxies collided forming larger and yet large galaxies. The foam structure you refer to in the large scale structure maps is the imprint of something. The conventional view is it represents the structure of the universe at the time the universe cooled to the point where most of the matter was not ionized. My suspicion is that what we are seeing is space at its smallest dimensions. You can think of the universe as this grotesquely huge enlargement of the smallest structures of space. This structure was imprinted on the universe from it very inception.

If the large scale structure is an enlargement of small scale structure it would imply that at the smallest dimensions space is quantized.

Starboy

joedad

That's interesting. We've all heard the expression "quantum foam," and now I have a new appreciation of that concept.

joe

Demosthenes

Actually, joedad, that's a different type of foam. They're talking about how the large-scale foam structure is "foamy-like", it has little to do with the concept of quantum foam.

QM itself says almost nothing about the nature of spacetime, in fact it assumes a constant background where the quantum processes take place against. The theory is that the space is actually discrete but QM is silent on that subject, hence the current search for a theory of quantum gravity.

Answerer

So, how many of you hope that spacetime is quantized?

Christopher Lord

It is quantized, otherwise quantum mechanics would be wrong. One result of this is that LED lights wouldn't work.

So you can test if the universe is quantized by finding the nearest LED (there should be one on your monitor) and checking if there is light coming out of it. If there is, you have proven that the universe is quantized!