| From: Daryl Hutchins | 4/02/99
17:04:16 |
| Subject: Expanding Universe | post id:
360 |
| Why must the "universe" have
somewhere to expand to? Is not the concept of "somewhere" and "somewhen"
and earthbound one? Can not the universe be infinite? It seems to me the boundaries of the universe are the limited by our knowledge of it. | |
| From: Halogen Fisk | 5/02/99
9:40:43 |
| Subject: re: Expanding Universe | post id:
423 |
| Maybe I'm just repeating your
statement, but.... The universe can be infinite in dimension & still expand. If all the objects in the universe are moving apart it is expanding, the "boundaries" of an infinite universe simply expand from infinity to infinity. | |
| From: Chris (Avatar) | 5/02/99
10:53:14 |
| Subject: re: Expanding Universe | post id:
439 |
| Halogen has it right. We aren't
afforded the luxury of an external view of the universe - we can't step
outside and view it globally. However that doesn't have to stop us
making global observations. Just as wecan tell things about the curvature
of space whilst within it, (see the postings on whether the universe is a
sphere) so we can tell about expansion whilst within the
universe. Basically if the universe was not expanding on a large scale then gravitation would have crunched the universe long ago (interesting to read up on Einstein's "fudge" in his original GR equations to try to account for a non-collapsing universe - we didnt know it was expanding then!) The clincher however was Hubble's discovery that light from distant galaxies is red shifted proportionally to the distance of the galaxy. In other words galaxies are receding from us at a rate somewhat proportional to their distance. I say somewhat because the rate is reducing. As for what it is expanding into - the answer is "nothing". Space and time are denizens of this universe - they're not continuous across any boundary that might exist, hence there is no meaningful "outside". The current favourite description of the universe is that it is "infinite but bounded" in the same way that the surface of a sphere is. If you blow up that balloon, its expanding surface is a fair visualisation of how the universe is expanding. Hope this helps! Chris | |
| From: Ronnie | 5/02/99
13:18:20 |
| Subject: re: Expanding Universe | post id:
454 |
| I reckon the boundaries of the
universe are our way of thinking - we just can't imagine something that
has no boundaries, no matter how hard we
try! | |