- #1
eclectic_echidna
- 3
- 0
I currently understand that quasars are billions of light years away from us. So the light from those distant quasars that reaches us now, started its journey a billion years ago.
When we examine quasars today we are really looking at something that existed a very long time ago and very far away (billions of units for both of those scales).
So how do we know that the quasars are still around after these billions of years? It seems that we really can't, unless I am missing something.
My other question. When Cosmologists calculate stuff, like the amount of matter in the universe, or the rate of expansion, how exactly are they accounting for the fact that we can't observe the universe as it is right now? Because the farther we look, the more in the past it really is.
Maybe I need a thought experiment. Say that a metallurgist is examining an straight iron rod that is 15 billion light years long by standing at one end. This rod has had a tough life and is continuously rusting from neglect. (uniformly across the entire rod). The end she is close appears rusty, but if she remains still and looks out toward the other end, the rod would get progressively less rusty. That is because the light that has traveled from that distant part of the rod is was transmitted at a time when the rod was less rusty. How does the cosmologist account for that?
This is keeping me up at night, and I would appreciate some websites or books to clear this up.
--
ee
When we examine quasars today we are really looking at something that existed a very long time ago and very far away (billions of units for both of those scales).
So how do we know that the quasars are still around after these billions of years? It seems that we really can't, unless I am missing something.
My other question. When Cosmologists calculate stuff, like the amount of matter in the universe, or the rate of expansion, how exactly are they accounting for the fact that we can't observe the universe as it is right now? Because the farther we look, the more in the past it really is.
Maybe I need a thought experiment. Say that a metallurgist is examining an straight iron rod that is 15 billion light years long by standing at one end. This rod has had a tough life and is continuously rusting from neglect. (uniformly across the entire rod). The end she is close appears rusty, but if she remains still and looks out toward the other end, the rod would get progressively less rusty. That is because the light that has traveled from that distant part of the rod is was transmitted at a time when the rod was less rusty. How does the cosmologist account for that?
This is keeping me up at night, and I would appreciate some websites or books to clear this up.
--
ee