B Revealing Secrets of Distant Supernova DES16C2nm: 10.5 Billion Years Ago

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Astronomers have identified that the supernova DES16C2nm exploded 10.5 billion years ago, but due to the expansion of the universe, it was only 5.5 billion light-years away from Earth at the time of the explosion. The light from the supernova took 10.5 billion years to reach Earth because the universe continued to expand during that time. The discussion highlights the complexities of measuring distances in an expanding universe, emphasizing that recession velocities can exceed the speed of light under certain conditions. The proper distance to the supernova at the time of emission was 5.5 billion light-years, while the distance at reception is now 17.3 billion light-years. Understanding these concepts is crucial for interpreting astronomical observations and the nature of cosmic expansion.
  • #61
Viopia said:
It is no wonder I needed time to digest what Bandersnatch said. I thought we were talking about real velocities. Ibix's comment about the Sun can be described in the following way:- As a you ''turn around'' the Sun does not circle you, you merely turn around so that the light hitting your retina (after passing the crystalline lens in your eye) scribes an ark on your retina. The light hitting your retina only tavells around an inch per second which is far less than the speed of light.
This is not the point he was making.

The point is that the coordinate speeds of a stationary object in a rotating coordinate system are directly proportional to the distance and if the distance is far enough then the coordinate speeds easily exceed the speed of light.

How fast the spot of light moves on the retina is also not bounded by the speed of light. The light at subsequent moments is not the same light pulse. There is no light moving along the retina.
 
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  • #62
Viopia said:
As a you ''turn around'' the Sun does not circle you,
Sure it does. That motion is no more or less real than any other.
 
  • #63
Orodruin said:
Ibix said:
Sure it does. That motion is no more or less real than any other.
If what you say is correct, the Earth traveling around the Sun could be thought of as the Sun rotating while the Earth is stationary. If the the Earth had no orbital velocity it would crash into the Sun. This means there is a difference.
 
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  • #64
Orodruin said:
There is no light moving along the retina.
No there isn't any light moving on the retina, just lke the Sun is not moving faster than the speed of light.
 
  • #65
Viopia said:
the Earth traveling around the Sun could be thought of as the Sun rotating while the Earth is stationary.

Well, yes. What's the problem with that? Motion is relative. That is the very basic thing.
 
  • #66
Actually, working in a rotating frame where the Earth is stationary is one of the easiest ways to work out orbital dynamics. You get a centrifugal potential that makes it different from the non-rotating case, but it is not any more or less real.
 
  • #67
Viopia said:
No there isn't any light moving on the retina, just lke the Sun is not moving faster than the speed of light.
Why do you ask questions and then, when we answer or explain, just say "no"?
 
  • #68
Viopia said:
No there isn't any light moving on the retina, just lke the Sun is not moving faster than the speed of light.
That’s the point. However, it is not ”just like”. In the former case it is a question of taking a speed of something that is not an actual object and in the latter a coordinate speed that is the coordinate speed of the Sun - an actual object.

Also, please be more careful with your quotes. You just attributed one of your answers to me making it seem I said something I did not.
 
  • #69
Orodruin said:
That’s the point.

Also, please be more careful with your quotes. You just attributed your answer to me making it seem I said something I did not.
I am sorry the quote was not from you. I don't know how this couild have happened. I was trying to answer two questions close together and used the prompt after highlighting the part I wanted to answer.
 
  • #70
Ibix said:
Why do you ask questions and then, when we answer or explain, just say "no"?
I sometimes don't understand the answers. When this happens I try to say what does not make sense to me.
 

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