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Q & A: gravity at a distance

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Most recent answer: 09/03/2016
Q:
Is it true that every single atom in the universe has gravitational attraction to every other single atom, so even if 2 hydrogen atoms are on the most distant opposite ends of the universe then they are still attracting each other and could theoretically come together given billions of years? Perhaps we could use a "gravity" beam to communicate instantaneously ( like the cotton between two tin cans)in the distant future ?
- Wayne (age 24)
Australia
A:

The universe doesn't really have "ends", but to the best of our knowledge two atoms ot near opposite parts of our cosmic horizon do still attract each other via gravity. They won't ever come together, however, because the expansion of the universe is accelerating so they will be outside each other's horizon. The sort of change that would be required to make the acceleration stop (some phase change of the vacuum) would not leave those atoms existing in anything like their present form.

As far as communication goes, gravitational changes travel at the speed of light, the same as electromagnetic changes.

Mike W.


(published on 09/03/2016)

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