Most recent answer: 01/19/2010

In a credible text I read that the edge of the universe is not only expanding, but accelerating. Does the van agree with this statement? Why or why not?
- Scooter (age 19)
Morgantown, WV, USA
Not exactly. The pictures we have of the universe don't include any edges. However, the distances between all the objects on a large scale are indeed not only expanding but also at an accelerating rate.

This change is measured in several ways. Perhaps the most direct looks at the red-shifts of light from distant galaxies, which indicate the rate at which they were moving away from us when the light was emitted. This can be compared with the brightness, which depends on how far away they were when they emitted the light. A fixed expansion rate would give a fixed distance/velocity ratio. The ratio isn't quite fixed, so we can see that the expansion has been accelerating.

Mike W.

(published on 01/19/2010)

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