Pandorra wrote:
Sin waves appear ALL over in nature - earth itself does it in many diffrent ways, one example being climate changes over millenia. So, why not the universe. We may not have been around long enough to experience it but instead of all this "we're accelerating" "we're slowing down" "we're going to implode" or "we're all going to fall apart" - How about we're just going to expand until a certain point then collapse again until we expand again, constantly moving along the wave? I suppose acceleration doesn't support this theory, rather slowing down would so I guess it actually doesn't hold up at all but I liked it two minutes ago.
This depends on the "rules" of the universe, which we're still working on figuring out. Our current "traditional" view of physics really doesn't support that kind of process. At least traditional forces could not account for it. We see wave patterns in nature because they are part of a whole. A top wobbles while it spins, but that's because it's one element which has other factors being applied to it (in this case, some pretty simple ones). Things like the environment on earth are similarly affected in sine wave like patterns over time. Oscillation is a common thing in nature, but in all cases it requires external forces to work. We move through seasons because of the earth's tilt and route around the sun. We move through longer patterns of weather due to other longer term factors (changes of chemical compositions in the air and water for example). But those things are all "winding down" over time. Just like that top. But it takes a *really* long time.
You can't really apply that to the universe's expansion and/or contraction itself though. Since there's nothing external to affect it, it shouldn't (theoretically) oscillate in that manner. It'll either continue expanding, or it'll stop, reverse, and collapse. There's no logical force we know of within the universe itself to make it shift from collapsing back to expanding. At least not that we know of...
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Edit: take 2: Ok, so I was thinking about that article and a line began to stick out
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To everyone's surprise, they found that the material isn't just coasting away from us in space, as expected in the aftermath of an explosion. It's actually picking up speed as it goes.
Why so quickly assume we're in the "aftermath" we have no idea the exact extent of "The Big Bang" even with all the theories in the string theory community so why would it be so hard to believe that we're still feeling the effects of the initial blast pushing us away from it? Maybe we're still accelerating and eventually will begin to slow and finally just stop?
Which begs the question: what happens when the universe "stops"? Do we just stop and that's it or...? Again. That's not in keeping with our current understanding of astro-physics. Normal explosive forces and gravity both work in predictable and well understood ways. An explosion imparts a velocity on something, but not an acceleration. Certainly, there's nothing in "normal" physics to explain objects that continue to accelerate apart billions of years after the event that set them in motion. They should simply have a velocity that is spreading them appart, and this is either high enough to "escape" from the gravitational pull of all other objects around them, or it wont be. So far, we're having a really hard time figuring out which case is true, so realize that everything else is pretty theoretical as well.
What this article is talking about is that there is evidence that things are indeed accelerating apart. Which, of course, blows the "traditional" understanding of astro-physics out of the water. There has always been a sub theory that there is some other process of expansion in the universe not related simply to large objects moving apart in classical ways. One explanation I heard was to think of the universe as a sponge. Pretend it's squished into a tight ball to start with, but then is released and gradually expands (or maybe it absorbs water and expands or something). Point being that it's not that objects are moving apart, so much as the space between them is stretching. Additionally, there are "gaps" in space, just like those in a sponge. We can't see or interact with them. They seem to not exist (because they *don't*). However, they are taking up extra "space" in between the rest of the universe as it stretches (which would be needed to preserve some of our conservation of matter/energy laws in physics).
A side aspect to this theory is that apparent expansion/contraction of the universe can simply be expressed as the ratio between the rate at which those "gaps" are growing in proportion to the overall stretching of the rest of space (that which we can percieve and interact with). If the gaps are growing faster, then the universe will appear to be contracting. If the rest of the sponge is stretching faster, then it'll appear to be expanding.
Dunno. I always kinda liked that theory. But it's one of many that could explain things. Problem is that we're just scratching the surface of even being able to detect the basic indicators of these things, so trying to explain them beyond purely theoretical models is hard. It's an interesting topic though...