Chown. Marcus, New Scientist, 15.11.2008, considers the possibility that our observable Universe might consist of a cosmic bubble within which the density of matter is lower than in the surrounding cosmos. This would mean that gravity inside the bubble would be weaker than outside.
Chown explains how this situation could explain the apparent acceleration of the Universe’s expansion, without the need to invent some mysterious dark force. “In such a low density region, the breaking pull of gravity is weaker, and so the region would quite naturally be expanding faster than the more dense area enveloping it. A bubble surrounding us, covering the volume from which light emitted over the past few billion years is just reaching us, would be just the thing to explain the supernova observations. Observing from within the bubble, but using distant supernovae as yardsticks, we would see a universe whose expansion seems to be occurring faster than it used to – without the need to invoke dark energy.”
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