- #1
Igottaknow
- 14
- 0
One thing that has always puzzled me is that the farther we look out into the universe we see that galaxies are moving away from us faster than galaxies that are closer to us, but also the farther we look out into space the farther back in time we are observing.
I have trouble understanding this since we know that what we are observing when we view a galaxy 4 billion light years away is what was happening 4 billion years ago. What is it about that light that we can say for certain that that galaxy is moving away from us at any specific rate as it is in relation to us now?
I do understand that it is is because of the red shift of this 4 billion year old light and the idea of the Doppler effect of that light that we have determined that galaxy's rate of movement but...how do we know for certain anything about what is happening with that galaxy right now in that region of space?
I guess i am trying to understand how we can determine for certain any thing about what we observe in the universe not being anything other than what was happening at the time the light left that object.
I have trouble understanding this since we know that what we are observing when we view a galaxy 4 billion light years away is what was happening 4 billion years ago. What is it about that light that we can say for certain that that galaxy is moving away from us at any specific rate as it is in relation to us now?
I do understand that it is is because of the red shift of this 4 billion year old light and the idea of the Doppler effect of that light that we have determined that galaxy's rate of movement but...how do we know for certain anything about what is happening with that galaxy right now in that region of space?
I guess i am trying to understand how we can determine for certain any thing about what we observe in the universe not being anything other than what was happening at the time the light left that object.