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Name: Andrew
Status: other
Grade: 12+
Location: CO
Country: USA
Date: Winter 2012-2013


Question:
In an expanding universe, if space-time expands faster than the speed of light, and light-producing objects are not traveling at the speed of light, are there galaxies somewhere in the universe that, from there perspective, are traveling away from other galaxies towards total darkness, chasing a region absent of matter-energy that is growing faster than these galaxies can expand into it?


Replies:
So far as we know space-time cannot expand faster than the speed of light. That assumption is used to calculate the speed and distance of galaxies and stars. We can only ?see? parts of the Universe that are closer than the speed of light x the age of the Universe. What is further ?out there? we have to way of knowing.

Vince Calder


Hi Andrew,

Thanks for the question. When I reviewed the three postulates of special relativity, the speed of light is constant in all reference frames. Thus the speed of light cannot be exceeded.

Jeff Grell


Hi Andrew,

The question here is certainly understandable. I believe you are in reference to a Universe composed only of matter that we are currently able to see and quantify easily.

The fact is that what we have observed to be darkness, probably is not dark and void. Lensing effects noted in the Abell cluster began to cause scientists to speculate about something in the dark we could not see. The unseen object(s) had to be between Earth and Abell and acted as a lens-- giving the cluster an appearance of being viewed through "coke bottle glasses".

Later, using x-ray and other spectroscopic techniques, scientists recorded what was referred to as Dark Matter. Now, with a method to look for this matter, which accounts for about 85% of all matter-- scientists are re-investigating what "dark" means.

Answering this question should probably await the findings of a map that well be a "sea" of Dark Matter and Energy that the galaxies are expanding into.

Try Wilkipedia to get an overall scope of Dark Matter and Energy. An article relating matter as a filament between galaxies is:

http://www.space.com/16412-dark-matter-filament-galaxy-clusters.html

Interesting question! Peter E. Hughes, Ph.D. Milford, NH



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