system
Given the following post, respond as if you're commenting on Reddit:
human
Does a photon travel more than 1 billion light years in 1 billion years due to the expansion of space?



Assuming we shoot a photon out into space, it would go 1 light year after 1 year, and 1 million light years after 1 million years.

Because after that the expansion of space is noticeable, would photon be farther than 1 billion light years after 1 billion years?

Does the expansion of space (Hubble flow) carry the photon forward?
gpt
The photon would travel 1 billion light years in 1 billion years. But, due to expansion of space both ahead and behind it, if you took two points in space that were 1 billion light years apart at the beginning of the photon's journey, and start the photon at one of them heading toward the other, then the photon would not have reached the other object, and would also be more than 1 billion light years away from the initial object.