As matter and energy expand with the big bang, they create spacetime (or so I've been told). Is there any evidence that this creation of spacetime has a retarding force on the expansion? If not, does this mean that matter moves through (existing) space with the same ease and when it is expanding space? That seems unusual. Gravity is a retarding force, but that force exists in normal (already created) space as well. I'm wondering if there is any force due to the creation of spacetime.
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$\begingroup$ Side note, existing space is expanding space. It's the same space. Expansion is more like stretching than it is like adding new space $\endgroup$– JimCommented Mar 31, 2015 at 20:48
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$\begingroup$ So space already exists everywhere out to infinity? And always has? That seems remarkably convenient.... $\endgroup$– JiminionCommented Mar 31, 2015 at 20:59
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$\begingroup$ It's just as convenient as it starting out of nothing and new space being constantly created $\endgroup$– JimCommented Mar 31, 2015 at 21:03
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$\begingroup$ But that would mean infinite space was here before the big bang. I find that remarkable. $\endgroup$– JiminionCommented Mar 31, 2015 at 21:05
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$\begingroup$ No, that's not at all what it means. It only means infinite space was created at the big bang $\endgroup$– JimCommented Mar 31, 2015 at 21:06
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2 Answers
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Gravity is the retarding force. I don't think that non-conservative forces are customarily considered.
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3$\begingroup$ Gravity is not considered a force at those scales so much as it is simply the curvature of spacetime due to the various forms of energy. And while it does allow the deceleration of the expansion when in concert with matter or radiation, it also allows the acceleration of the expansion when sourced by dark energy. So the only thing I can say is this answer is not even wrong $\endgroup$– JimCommented Mar 31, 2015 at 20:40
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$\begingroup$ Added to the question to clarify the matter. Not really thinking about gravity, but thanks for pointing that out to help me clarify the question. $\endgroup$– JiminionCommented Mar 31, 2015 at 20:45
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Regular matter and energy, through, gravity tends to slow the expansion. I do not know of any theory that treats it or any other "retarding" force as friction. However there is evidence that another stuff in the universe, different from regular matter and energy (called dark energy) is actually accelerating the expansion, rather than slowing it (also, through gravity) .
And in current theories yes, matter moves through (existing) space with the same ease than through expanding space
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$\begingroup$ Gravity is the curvature of spacetime. Dark energy accelerates the expansion as a negative pressure term that curves spacetime such that expansion accelerates. This means dark energy, like all other forms of energy, affects expansion through gravity $\endgroup$– JimCommented Mar 31, 2015 at 20:47
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$\begingroup$ @Jimnosperm thanks for the clarification, I corrected my answer. $\endgroup$– user66432Commented Mar 31, 2015 at 20:54