How can the universe be expanding?

Originally posted by Kayzar
eh, who knows? When looking for facts it is best not to start off with if [insert theory here] is true.

Excuse me sir.
I do not think you understand science or facts.

If we have a hypnosis or theory it must be testable. It is a pretty good way to do this is by asking "if [insert theory here] is true" we can predict the answers.

A few examples ..

- If [evolution] is true we should never find a rabbit in the Cambrian period.
- If [evolution] is true we should find a reason why humans have 23 pairs of chromosomes but all other hominids have 24 pair.
etc etc

David Scott should be able to fly to the moon and drop a feather and hammer at the same time and ...
If [gravity] is true they they would hit the ground at the same time.

reply to post by yaphun

If we have a hypnosis or theory it must be testable. It is a pretty good way to do this is by asking "if [insert theory here] is true" we can predict the answers.

Yes but not in this case.A hypothesis is a proposed explanation for an observable phenomenon, for example:
If i eat my poop then i will vomit
A theory is an explanation of reality that has been thoroughly tested so that most scientists agree on it.
Big difference, which is why you will never hear about Kayzar's theory of poop vomit.

A few examples ..

- If [evolution] is true we should never find a rabbit in the Cambrian period.
- If [evolution] is true we should find a reason why humans have 23 pairs of chromosomes but all other hominids have 24 pair.
etc etc

Horrible examples...

David Scott should be able to fly to the moon and drop a feather and hammer at the same time and ...
If [gravity] is true they they would hit the ground at the same time.

Another horrible example, he just prooved law (not theory) of universal gravitation to be correct, big whoop.

No.
Also no I will not waste my time if you cannot even get this much right.

Good day, sir.

The apparent universality of red and blue shift, as seen from Earth, can be quite a troubling little logic problem. I mean, simply put, just finding the "center" of what could be called infinite (or reasonably enough so, from our perspective) is enough to make ones brain twitch. But then to assume that we would happen to be directly in the middle of this unfathomable point in space? It's all a bit much.

My personal gut feeling is that what this data actually suggests is that we don't truly understand the nature of time/space and it's only our limited grasp of the concept which makes it appear to us that we occupy this rarefied position in the cosmos.

Maybe any and all positions one could occupy in time space would give the same perspective... that the "shape" (structure, nature, composition - whatever applies) of the universe is actually the cause. Or something along those lines.

Just my thoughts anyway.

~Heff

reply to post by Hefficide


I'd just like to comment on the 'centre of the universe' issue. Just because 'everything' is moving away from us, it does not mean that we are stationary in the context of all other movement.

As an example. Imagine a set of traffic lights where three cars are lined up. The lights turn green and the all the cars starting driving along a straight 3-lane road. Each car travels at a different speed, we'll call them slow, medium and fast. After a period of time, the relative positions would be something like this:

START
---------------------------->S (slow)
----------------------------------------------------> M (medium)
-------------------------------------------------------------------------------> F (fast)

The point is, M is quicker than S and F is quicker than M. It is obvious that F is moving away from M, leaving it in the dust trail, however, from the relative context of M, S also appears to be moving away in the opposite direction to F.

Relative speeds

S (slow) F (fast)

If you ignore the fact that S, M and F are all moving, then it could be assumed that M is stationery and S is simply moving away slower from M that F, both in opposite directions.

Perhaps somebody would like to comment on whether celestial objects are heading away at a lower speed from the Earth than objects on the opposite side?

It doesn't seem like anyone has considered an expanding universe that's spatially infinite.

Originally posted by Nostradumbass
Okay one more question. If I were to inflate a balloon, wouldn't the points grow in size with the perspective balloon. So the observer would also grow at a rate where the distance points are still within the same proportional distance?
The expansion would be nothing more than an illusion?

That would be the case if there was not any attraction between the particles that made up the observers. But there is EM force, weak interaction, strong force and gravity. Since the force of expansion depends linearly on distance between particles, and the other forces are inversely proportional to the distance, there is a cutoff distance when attraction overcomes repulsion. This objects are then bound, and expansion has no effect on them. Thats why expansion becomes relevant only in intergalactic distances, when all fundamental forces (EM-weak force, gravity, strong force) become smaller than the force of expansion.

Metric expansion is a key feature of Big Bang cosmology and is modeled mathematically with the FLRW metric. This model is valid in the present era only at relatively large scales (roughly the scale of galactic superclusters and above). At smaller scales matter has clumped together under the influence of gravitational attraction and these clumps do not individually expand, though they continue to recede from one another.

High redshift quasars have been observed in front of low redshift galaxies, as well as having high redshift quasars connected by fillaments to low reshift galaxies. Hundreds of these have been catalogued by Halton Arp.

The mainstream have said these are chance algnments, and even to the point of saying the bridges/fillaments didn't exist. However the evidence for an intrinsic quality to redshift is solid.

This doesn't mean there is no distance velocity relationship, this seems to be just one component of redshift. Along with an intrinsic quality there is also the possiblity of the light interacting with the plasma medium at various densities along it's jouney and losing energy in a tired light scenario. Also chuck in some plasma redshift experiments and it begins to bring into doubt the question of an expanding universe concept and in turn the big bang.

Other methods have also shown some dicrepencies with redshift, the problem it seems is that all of these factors can't be extracted within an certainty to know how much of the redshift is due to velocity/reccession.
And the appearance of expansion is more than likely due to these other redshift phenomena at play.

reply to post by Firepac


Did you read anything that anyone posted? This thread has absolutely nothing to do with how far the universe can expand, its about whether or not it actually is expanding.

Maslo has answered the OP's question well enough... but there is one thing I want to reply to...

Originally posted by VariableConstant

I have a very intelligent friend who asked me a good question the other day, as we were debating the currently accepted theory as to the creation of the universe. He talked about black holes, which as far as we know are nothing more that incredibly dense matter that have such a pull that nothing can escape from them, not even light. So if you consider that, according to the bang theory, all matter in the universe, including all the stars, collapsed or otherwise, along with all the planets and everything else, were once concentrated into a "primordial egg."

This ball of matter would contain everything that currently makes up our universe, and would therefore have a mass and density beyond our ability to comprehend. Its gravitational pull would be inescapable. So how could anything ever escape from this central point, regardless of the violence of any explosion?

I'm not an astrophysicist, so maybe someone else would be able to answer this, but it seemed like a pretty good question to me.

Your friend should familiarize himself with cosmology theories that aren't 60 years old.
The current "Big Bang" theory is, in fact, not a Big Bang theory at all. It's called LCDM (Lambda - Cold Dark Matter) Cosmology. "Lambda" refers to the Cosmological Constant of Einstein's field equations, which is responsible for the expansion of the universe and is the mathematical description of what is now called Dark Energy. "Cold Dark Matter" refers to the addition of additional matter-density that is undetectable by traditional means, and is responsible for anomalous galaxy rotation curves.

LCDM says that, in the beginning (so-to-speak), it was very possible that the universe was infinite. In fact, my preferred view is that the universe was an infinite void, containing nothing at all. The difference between this empty universe and our current universe, though, is its level of zero-point energy. This energy is found in Quantum Mechanics, and is the energy contained within a vacuum. That is, in QM, a vacuum is not a region containing absolutely nothing, as we often consider it to be - a vacuum is, in fact, a region having the lowest possible energy level. I tend to liken this to walking on the ground. When you walk along the ground, you are effectively at your lowest possible energy level. But, what happens if you happen upon an abandoned mine shaft and fall through? Suddenly, your once-"lowest possible energy level" has collapsed to an even lower "lowest possible energy level." Essentially, this is what modern cosmology says occurred within that original universal void.

When the vacuum of that initial void spontaneously collapsed to a lower energy level, the potential (zero-point) energy it had been containing was released, and this massive release of energy is what drove that initial sudden period of rapid inflation (during what's called the Inflationary Epoch). Eventually, once the energy had dissipated enough for the inflation to slow significantly, the universe was allowed to cool, and the energy condensed to form particles and, ultimately, matter.

This is the current theory. Now you can bring your friend up-to-speed.

If the Universe is expanding what is the composition of the realm it is expanding into. The claim implies that not even space exists on the other side of the event horizon. Unfathomable. Lets find out what space is composed of first before we assume there is yet another structural realm outside of space. Let's do the same for time before we consider there exists a "never".

Originally posted by Firepac
It doesn't seem like anyone has considered an expanding universe that's spatially infinite.

edit on 3-7-2011 by Firepac because: (no reason given)

The Universe we can observe is but one of an infinite number of them, then? Why not? Who am I to tell God how to conduct Its business? I am but a bug.

The easiest questions are most of the time the most difficult onces to explain. This question is no different.

Certainly, I could talk about the big crunch or the infinate expansion. But let's ask ourselves a little different question;

We see the universe expanding, but what is behind that wall of dark matter that originates from the primordial blast?

If the universe is expanding we can assume that the outward force generated by the primordial 'big bang' is bigger than the resisting force on the other side of the wall. Maybe it is expanding into nothingness and thus creating something?

Ofcourse that is not true. Nothingness can't exists unless absolutely nothing exists including the not existing of our universe. So we must state that at least something exists, somthing that has less matter density per square inch than our universe has as an outside pushing force. That would be, very light maybe even negative towards our own universe.

Let's assume for humor sake that it is negative, this would create a sucktion effect, much like a drain seems to suck water. Essentially it would mean that expension was accelerating. if that were true than eventually we would end up with one molecule evere hundred lightyears and no more planets and stuff.

If it is lighter but not negative than it would ultimately form a barrier, this compressed barrier would be like a wall, potentially between many 'universes'. Possible, but there needs to be an end somewere.

I guess the real limitation here is not so much what is behind the wall, but more how far can we stretch our mind.

reply to post by Nostradumbass


It's factual because we can analyze the light coming from stars and galaxies. If the distance between the light source and the observer increases, a redshift takes place as the wavelength of the light increases. We can observe this redshift everywhere, so that's why scientists say the universe is expanding.

LINK

Originally posted by Nostradumbass

But for that to be true, you must assume that we are the center of the universe, which seems egocentric. For expansion to be noticed between 2 objects their must be a center focal point which remains static. If there is no center of the universe then expansion between two objects would be impossible. The only way for space to be expanding between galaxies would literally be if every planet/asteroid/point in the universe was the center of the universe.

This is actually correct. Every place in the universe will see itself as the center of the Universe.

Originally posted by Maslo
But that center point does not lie on the surface of the balloon. That means that there is no center or any point of significance in our three dimensional spacetime, because our universe IS the surface of that baloon.

I've always thought of the balloon anology to be rather useless in explaining the Big Bang to the laymen. A better analogy would be to think of our Universe as the surface of a hypersphere. For anyone who wants to know, look up hypercube and hypersphere and you'll know what I'm talking about. Our Universe can be thought of as an expanding hypersphere.

reply to post by Firepac


I'm not really sure how much better a hypersphere analogy is at visualizing the expansion of the universe.
Personally, I prefer the raisin bread illustration.

reply to post by Kayzar


I don't know where you are getting that definition of theory, but it's incorrect. There is no requirement that a theory must be supported by 'most' scientists., or even anyone at all. If that were the case, we wouldn't be able to have dozens of competing theories in fields such as string theory as we do now, as none of them would be able to gather the required support.

Basically, it's a hypothesis until you have any data to support. At that point, you can call it a theory if you want. A theory in science is simply a proposed explanation whose status is still conjectural. It doesn't have to be popular, it just has to be falsifiable (I.E fit inside the scientific model) and fit currently observed data. Once it is falsified, it's no longer an active theory. Theories rarely ever get verified, simply because it is difficult to prove something absolutely without infinite data.

But that said, simply because it's a theory does not discredit it. Gravity is a theory. It is very hard to verify something absolutely without an infinite set of data. The universe IS expanding, at least according to out current knowledge. It is a sound theory, and it would require a major change in our understanding of the universe if it was disproven away.

I don't understand why we would have to be the center of the universe to notice expansion, that's just absurd. Imagine if we are in a race, and there's a starting line. 3 cars start at the same time, one going 45mph, one going 60mph, and one going 75. We each are getting further from each other at varying speeds, and if we are the car going 60mph, we certainly know we aren't staying still, and we can tell the common vector is not our position, but the starting line.

From our position it would appear as if everything is radiating out from us, in the same way people on the platform appear to be moving when you are in a speeding train. To me, assuming either of these things is equally foolish.