Discussion in 'General Discussion' started by eyeballkid, Mar 13, 2007.
What are they? No religion...snitch, snitch...
I'm not entirely sure I understand the question.
The lastest thing I have a hard time understanding is this...
...a friend explained to me that, according to what he's learned in his astronomy class, the universe cannot be infinite, because an infinite universe would have stars in every concievable position that we can see. As a result, in an infinite universe, the night sky would be as brightly-lit as the daytime one.
Though it's not an easy thing to wrap one's mind around the idea of infinity, I'm having a harder time dealing with the idea of an finite universe instead of an infinite one. What would the borders be?
The thought limit that irritates me most is that we can't visually conceive a spatial fourth dimension.
There is such a thing, and we can draw a three-dimensional visualization of a hyperdimensional solid, but we can't actually imagine an object extending through the fourth dimension, no matter how perfectly we can study and understand the concept.
it could still be infinite. asteroids, dark matter, clouds of gas, comets, planets....all these could block light from stars. and don't forget those black holes!
And yeah, it is completely insane trying to come up with an idea of what might be beyond the boundary of a finite universe.
Imagine the instant of the Big Bang... all possible matter compressed into a single point for a planck second. You have to think that this matter was a point in some kind of space larger than it. I mean... when the matter compressed, you'd think that it was compressing from some space which is now empty.
The human mind of course can't even imagine the idea that outside of this single planck unit of space that all space is compressed into, there was no space... no emptiness, nothing. How can you have a single point that's not located at some point in space, but is, in fact, all space itself. We can't even picture the nature of the universe in such a state. God is amazing to have come up with something so completely amazing and unimaginably complex. (yes, I do believe in both Baptist Christianity and the Big Bang. No reason why those two ideas cannot coincide)
This reminds me of a wonderful quote from Sam & Max: "Kids, try imagining how far the universe extends! Keep thinking about it until you go insane."
Which is what I tried to tell my friend at first, but then the idea stuck in my head. Like a virus.
That, and the fact that some of those points that stars would occupy would have likely burnt out by now...or not been formed as yet...
...I think. Do new stars still form, or was that strictly beginning of the universe stuff?
agravilin...just when I start thinking that the universe makes sense again, you go and re-illustrate another concept I'd had trouble with. Yeah, space and time would be wrapped up in that zero point, wouldn't it? That's hard to picture.
Also, the spatial fourth dimension...the fourth dimension's time, isn't it? Or am I remembering wrong? Because if the fourth dimension's time, then isn't everything we perceive extending through the fourth dimension?
The best explaination I've heard is the one Carl Sagan gave in Cosmos, that the universe is finite but unbounded.
This seems like a contradiction at first, but if you think about it, the 2D area or "space" of a sphere like the Earth is also finite but unbounded in that, if you travel in one direction in a straight line, you will eventually end up back where you started from.
That way even though the Earth's surface is a finite quantity you can keep going around and around forever without ever running into a barrier.
The universe could be just like this except it has an additional dimension curved on itself.
Of course, my way of putting it still doesn't adequately explain why we don't see an infinite regression in every direction but I'm kind of rusty, so please don't discount Sagan's model on my account.
That's a most definite yes. In the beginning the only elements were hydrogen and helium, so getting all of the heavier elements up to iron required at least one generation of stars, and all of the elements heavier than that required several generations of supernovas.
Consequently, our sun is at least a second generation star since it already contains heavy elements and there was already enough left over to form planets.
Furthermore, we can see star formation in progress, as the Orion Nebula, for example, has many globs of gas which are accreting to form stars as we speak (or were 1000 years ago due to the finite speed of light, but that's peanuts compared to stellar time).
A much closer example of a recently formed star would be Vega, which is 20 light years away and still has a disk of gas and dust which is getting lumpy in places, suggesting that Vega's planets are still forming.
I always thought that "limit of human thought" thing was that speed of 250mph someone worked out the human brain operates at.
Still trying to figure how they worked that one out.
Generally fourth dimension refers to time but that's only a specific case. Mathematically you can study spaces with N dimensions (N being any integer value that you want). If you're interested, read up on dimension and manifolds.
limits are the ones based on preconceived notions. from day one we are told, "no you can't do that." I feel a human is capable of anything... if we only knew how. Each person being a universe unto himself.
I keep trying to think of a burrito so big, even god couldn't microwave it.
Ah yes, Olber's paradox (it took me a few hours before I finally remembered what it was called). This is one of the reasons as to why the universe is theorized to be expanding.
Is it said that power corrupts, but why? Is it due to past hurtful actions of others and self, or is it simply ingrained in people to abuse ones power?
Wait, are limits to these threads you keep throwing out?
I would guess there is not real limit to human thought.
I can't remember who said it, but back in 1900 some guy said that everything that was going to be invented was already invented.
This was before things like the tv and the plane.
It also depends on the particular person. Some people have a gift of creativity, some don't.
Also, putting a finite age on the universe helps. Light does not travel instantaneously; it has a top speed. The very most distant light we can see would by definition also be the oldest light. If the universe has a beginning, and the majority of indications are that it has, then we should not be able to see light coming from farther away than that beginning, since there would mean the light was emitted before the beginning of the universe. Past an observation radius corresponding to the age of the observable universe, we would not see anything. Black.
In a true infinite universe, with continuous star generation, we might indeed see a sky of blinding light. But we don't.
That's interesting, I've never thought of it like that before. Hmmm.
A funny correlation to that is that, because the concept of "observable universe" requires an observer, every single person is at the center of their own little universe.
I assumed that the reason for this is because there is so much space that the stars are pretty far apart from each other, making it to where some stars are so far away you'd never be able to see them from here. To say you can see the entire universe of stars from here seems ridiculous. Of course, I could always be wrong.
I second the Livejournal suggestion made elsewhere.
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