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Special Collaborator
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Joined: May 13 2007
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Posted: November 24 2013 at 13:14
Equality 7-2521 wrote:
I don't think the balloon is a bad metaphor. You just look at the surface of the balloon and forget that surrounding or enclosed space exists. It's meant to explain the way something expands not why, or where.
Oh, I do actually agree it's just that for many people the mental image of an expanding Universe does not forget the surrounding and/or enclosed space. For example in Jim's backyard example where his expanding Universe expands to envelop his fence post cap. It's that age-old problem of trying to explain a n dimensional problem in n-1 dimensions (the 2D surface of the balloon represents a 3D Universe, the 3D balloon volume is not the 3D Universe).
Joined: February 03 2007
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Posted: November 24 2013 at 13:30
Equality 7-2521 wrote:
Who said space was infinite to begin with? And correct. Prior to the big bang space did not exist. We're not even necessarily sure that space can exist without matter.
Very interesting, thank you.....i will try to absorb this. I had assumed it existed forever and infinitely. And that our bang was just a relatively "recent" development.
...that moment you realize you like "Mob Rules" better than "Heaven and Hell"
Joined: July 04 2005
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Posted: November 24 2013 at 13:59
This may sound silly but is the Universe expanding in a virtual straight line (relative to where it originated and doesn't collide with anything)? Or does it bend? I know it doesn't suddenly turn 90 Degrees.
Edited by VanderGraafKommandöh - November 24 2013 at 14:00
Joined: August 11 2005
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Posted: November 24 2013 at 14:11
I'm not sure I understand the question. There is no center of the
universe. Every point is expanding away from every other point. There
can be no collisions are space itself is expanding and not the case that
matter is being pushed away along space.
"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
Joined: July 04 2005
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Posted: November 24 2013 at 14:21
I know there's no centre but there was one original point where
everything expanded from. I presume when the big bang happened and
everything was created that it all expanded from that original point in a
relative straight direction. What I mean is whatever is expanding
doesn't suddenly turn 90 degrees and continue on. Obviously galaxies
are created.
And of course there can be collisions... surely not
everything expands at the same speed so eventually some of the expansive
material (travelling faster) will catch up with other material ahead of
it (travelling slower) and thus get either pulled into the orbit of a
sun or collide with it and perhaps be pushed into a different direction
(yet still expanding)?
Joined: August 11 2005
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Posted: November 24 2013 at 14:24
No.
No such region of the universe is different than any other. There is no point in space where the universe started. It's better thought of as a point in time.
I'm not sure what you mean by expand in a straight line. The expansion is 3 dimensional for one thing and occurs in all directions.
Different regions of space are expanding quicker than others. But all objects are moving further apart from each other. No collision can occur. Nothing is moving closer to anything else. Nothing is actually moving. Space itself is expanding. Think of the balloon analogy. Points on the balloon can never collide. They're not actually moving. More empty junk is occuring between them.
"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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Posted: November 24 2013 at 14:44
Equality 7-2521 wrote:
No.
No such region of the universe is different than any other. There is no point in space where the universe started. It's better thought of as a point in time.
I'm not sure what you mean by expand in a straight line. The expansion is 3 dimensional for one thing and occurs in all directions.
Different regions of space are expanding quicker than others. But all objects are moving further apart from each other. No collision can occur. Nothing is moving closer to anything else. Nothing is actually moving. Space itself is expanding. Think of the balloon analogy. Points on the balloon can never collide. They're not actually moving. More empty junk is occuring between them.
I was using the balloon analogy. I know it's 3 dimensional. That's what I mean. When a balloon expands a point you mark on the rubber doesn't suddenly turn 90 degrees to the right. It will go in one direction and won't go off course. That's what I mean by straight. It may arc slightly though of course.
I'm referring to the junk colliding like asteroids and meteorites and planets. They do collide. I do understand that there are galaxies and stars and black holes that change things though.
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Posted: November 24 2013 at 15:25
^as Pat and I have already said, nothing is moving, the space between everything is expanding. Every object in the universe remains in their relative spacial configuration. Objects that are moving inspite of the expansion such as two galaxies that are on a collision course (for example Andomeda and The Milky Way) will continue to move towards collision because their relative speed is so much faster than the expansion of the Universe because they are local to each other.
Special Collaborator
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Posted: November 25 2013 at 01:54
VanderGraafKommandöh wrote:
And of course there can be collisions... surely not
everything expands at the same speed so eventually some of the expansive
material (travelling faster) will catch up with other material ahead of
it (travelling slower) and thus get either pulled into the orbit of a
sun or collide with it and perhaps be pushed into a different direction
(yet still expanding)?
The expansion is proportional to distance and so the speeds are also proportional to the distance. If you take an piece of elastic with a mark on the mid point and fix one end to the table, as you pull on the other end the elastic will stretch, if you stretch the end an extra 100mm the mid-point mark would have moved 50mm so if you stretched the end at a rate of 10mm/second the mid-point would be stretching at 5mm/second, after 10 seconds all three points will be further away from each other (the mid point will be 50mm further way from both ends). So a galaxy "A" that is expanding away from us at 0.1% light-speed is moving twice as fast as another galaxy "B" that is only half as far away - this means that not only are both of them moving away from us, they are also moving away from each other even though galaxy "B" is moving in the same direction as galaxy "A". Since it is the galaxy that is furthest away that is moving fastest, they can never catch up with each other.
Joined: August 11 2005
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Posted: November 25 2013 at 13:57
I mean. What does that have to do with what you said? And Gabriel's Horn
makes perfect sense. As I was saying earlier in this thread, it only
leads to a seemingly unintuitive thing when you try to apply some
physical metaphor to it. The issue is thought that the physical metaphor
is meaningless when you actually analyze the situation.
"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
Joined: April 05 2006
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Posted: November 25 2013 at 15:28
"It is known that there are an infinite number of worlds, simply
because there is an infinite amount of space for them to be in.
However, not every one of them is inhabited. Therefore, there must be
a finite number of inhabited worlds. Any finite number divided by
infinity is as near to nothing as makes no odds, so the average
population of all the planets in the Universe can be said to be zero.
From this it follows that the population of the whole Universe is also
zero, and that any people you may meet from time to time are merely
the products of a deranged imagination" (Douglas Adams).
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Equality 7-2521 wrote:
