- #1
TheSwamper
- 4
- 0
I have to preface my questions by saying that I have only a little better than a high school understanding of physics; as such I humbly ask that any answers be termed in a way that I'll be able to understand them.
I've read that the universe has a radius of ~ 46 billion light years. And we know that it's about 13.7 billion years old.
This hurts my head. How could we possibly see something that far away? Light simply wouldn't have had time to get to us from that far? How is it that we can see beyond the 13.7 billion year mark? Wouldn't the largest area we can view be roughly double that, 27.4 billion light years? And if we can't see it, how can we know?
Furthermore, how can the universe even have a measurable size? Are we even certain it's finite?
I have seen Hubble photographs of the earliest galaxies, which formed when the universe was about a billion years old. Wouldn't they be so far from us by now that there's no way the light could have reached us? Did we see them with some sort of gravitational lensing, allowing us to see beyond the 13.7 billion year mark?
I've also read that the universe, for a time, was pure energy - no matter. And after that it was still a while before there were even photons. Have we been able to see back to this time? Physicists seem fairly certain what happened right up to only a few Planck times after the Big Bang. How can they know? Do we have any evidence of what happened prior to the existence of photons, other than math?
Forgive me if these seem simplistic, but my desire to understand is strong enough to risk the embarrassment.
I've read that the universe has a radius of ~ 46 billion light years. And we know that it's about 13.7 billion years old.
This hurts my head. How could we possibly see something that far away? Light simply wouldn't have had time to get to us from that far? How is it that we can see beyond the 13.7 billion year mark? Wouldn't the largest area we can view be roughly double that, 27.4 billion light years? And if we can't see it, how can we know?
Furthermore, how can the universe even have a measurable size? Are we even certain it's finite?
I have seen Hubble photographs of the earliest galaxies, which formed when the universe was about a billion years old. Wouldn't they be so far from us by now that there's no way the light could have reached us? Did we see them with some sort of gravitational lensing, allowing us to see beyond the 13.7 billion year mark?
I've also read that the universe, for a time, was pure energy - no matter. And after that it was still a while before there were even photons. Have we been able to see back to this time? Physicists seem fairly certain what happened right up to only a few Planck times after the Big Bang. How can they know? Do we have any evidence of what happened prior to the existence of photons, other than math?
Forgive me if these seem simplistic, but my desire to understand is strong enough to risk the embarrassment.