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All of the talk about finding a new distance record for farthest galaxy from us has fed my interest in the concept of universe expansion. I had three questions that hopefully someone here can help me understand.
First, because of the fact that all galaxies are moving away from each other, does that mean that some (those on the leading edge) galaxies are travelling faster than other galaxies? Two, regarding the new farthest galaxy, is it further out than the center (at least the percieved center, but I'll get to that in my next question) from us or are astronomers looking back to the farther edge? Finally, addressing the center of the universe - looking for information on this subject, I found this on the Bad Astronomy website Quote:
Sorry, if my questions seem silly, sometimes I have a hard time conceptualizing that which I cannot see.
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Some Scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that THAT is the basic building block of the universe- Frank Zappa |
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[stupid question alert] I think I understand now how galaxies are not moving apart. The space is expanding in all directions making it appear from ANY given point that every other point is moving away from you. I've heard it said that this is over "large scale" distances as in those between galaxies. Does this expansion of space have a limit in terms of smaller distances? Is our galaxy itself expanding? Are the atoms in my desk slowly getting further apart?
If the amount of matter in the universe remains constant and the volume or space of the universe continues to expand, the average density of the universe is decreasing, right? Is the density of my desk also decreasing? If not, what is the limit where space ceases to be expanding?[/stupid question alert] |
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Maybe 30 billion years from now. Do a Google search for "big rip" for info on a possible "end of the universe" scenario.
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Any day you wake up on "the right side of the dirt" is a good day. T. Anderson |
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Some try to tell me, thoughts they cannot defend,... - Moody Blues. |
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The universe is expanding in all directions, right? If so, isn't there a center, either with something or as a void?
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Some Scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that THAT is the basic building block of the universe- Frank Zappa |
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Well, technically there is a center, but it would be outside of our universe. Think of our universe as being spherical. In fact, think of it as a large, expanding balloon. Our universe has an extra dimension, so our 3 dimensional space is contained on the surface of the 4 dimensional sphere. It's basically like an ant on the baloon observing it's 2 dimensional movement capability (foreward, back, left, right) and seeing that the distance to the next ant on the baloon was increasing and concluding that this expansion had to have a center. It does, but it's no longer accessable. The center is not part of the baloon, it's inside it. Just as in this analogy, the center of the universe is not accessable to anybody in the universe, but technically there is a center. I cannot point to where the universe is, but I can tell you that if you go in one of two different directions perpendicular (spelling?) to all of our three, you will eventually hit the center of our universe. However, this would be impossible to do without some technology we haven't discovered yet.
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Thanks for the explanation, it makes a little more sense now. Kind of freaks me out to think about it though...
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Some Scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that THAT is the basic building block of the universe- Frank Zappa |
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Does that mean that when I’m running away from a lamp post, I’m “moving”, but if someone puts me in a car, then the car “drags” me away from the post, but I’m not really “moving” relative to the post? The car is just “dragging” me along with it, but I’m “stationary”? What branch of physics is this? Explain to us exactly how space “expands”. Do space particles get bigger, or what? Does “new space” fill in the gaps in the “old space”? Does the old space “stretch” or what? You keep saying that “space expands”, but I want to know how space expands. What is the physical function of “space” that allows it to “expand”? If we’ve got two rocks in front of us, and we move them apart, we see that the space between the rocks has “expanded”, but that’s because we moved the rocks. So how can the galaxies be moving away from us, thereby causing their light to redshift, yet you say they are “not moving”? Please explain in detail how that physically works. |
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here's a neato page i found on yahoo:
http://www.estfound.org/ |
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Thanks for the good explanations. I pretty much have lost the ability to learn new things (or perform new tricks) so thanks for being patient. I think I learned more in the last two days about the universe from reading this and the other thread. I hope to be able to peruse some of the links as well.
As for your questions Sam5, I'm not your man, I have no idea how it works. Don't even know if I could comprehend it if explained. I'm with you hickboy, kind of freaks me out too and hurts my head if I try to think about it too hard. :-s |
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Pi Man, that's only for a closed universe only, isn't it? Since our universe is flat, it's center would be somwhere inside of it, if it has one. Would it even have a center if it's infinite in extent? If it did, it wouldn't be impossible to tell if you were there.
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I wish BA would send all these guys who say that space is expanding and that the galaxies are not moving to the "against the mainstream" board. That is such a stupid, ridiculous idea and misconception. If space is expanding to explain the red shift, then why does it expand so much more for radio waves than for x rays? A radio wave at z = 1 expands to twice its wavelength which is several meters, but an x-ray at z = 1 only expands a few nanometers. If the red shift is doppler, of course more distant galaxies are moving away faster than more nearby ones.
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Any day you wake up on "the right side of the dirt" is a good day. T. Anderson |
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A one meter radio wave emitted at z=1 expands to two meters. A billion 1 nanometer waves of X-rays (1 meter) expands to two meters (one billion 2 nanometer waves). What's the problem? :roll:
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Any day you wake up on "the right side of the dirt" is a good day. T. Anderson |
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Lighten up! This is a stellar board! Author: duh. "The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly. |