Does an Expanding Universe Alter How Quickly Light Travels Through Space?

AI Thread Summary
The discussion explores how the expansion of the universe affects the travel of light through space. It highlights that as space stretches, distances increase, raising the question of whether light takes longer to traverse these expanded distances. Participants consider the relationship between time and space, noting that time can be affected by mass, such as near black holes. There is curiosity about whether the absence of mass in voids influences the consistency of time and, subsequently, the speed of light in those regions. The conversation emphasizes the complexity of these concepts in understanding cosmic dynamics.
Gal
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As the universe expands, space itself gets "stretched" and objects drift apart, like dots on elastic surfaces when force is applied. So one meter billions of years ago is two meters today, but does it necessarily mean light takes twice as long to travel this "new meter"?
 
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Gal said:
As the universe expands, space itself gets "stretched" and objects drift apart, like dots on elastic surfaces when force is applied. So one meter billions of years ago is two meters today, but does it necessarily mean light takes twice as long to travel this "new meter"?
Yes.
 
Gal said:
As the universe expands, space itself gets "stretched" and objects drift apart, like dots on elastic surfaces when force is applied. So one meter billions of years ago is two meters today, but does it necessarily mean light takes twice as long to travel this "new meter"?

This is kind of similar to a question I have.
My question is: do we know that time stays consistant throughout all the universe. We know that time and space are intertwined, and that time is relative depending on mass, such as near an event horizon. Does the absence of any mass, out in the voids of space, between galaxies, also affect time's consistancy? If not, would light pass though these areas at a different rate comparatively?
 
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https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Title: Can something exist without a cause? If the universe has a cause, what caused that cause? Post Content: Many theories suggest that everything must have a cause, but if that's true, then what caused the first cause? Does something need a cause to exist, or is it possible for existence to be uncaused? I’m exploring this from both a scientific and philosophical perspective and would love to hear insights from physics, cosmology, and philosophy. Are there any theories that explain this?
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