One for the PH Astrophysicists......
Discussion
During the quieter moments on night shifts at work I tend to trawl the net, reading about things I'd like to know more about. Recently the mind expanding topic has been The Universe. Quite a broad subject.
Anyway, what I can't figure out is how it can be as big as experts reckon. It is estimated to be about 93 billion light years in diameter and 14 billion years old. If nothing can travel faster than the speed of light surely it couldn't have expanded to be bigger than 28 billion light years wide since the big bang.
Can anyone explain this to me?
Anyway, what I can't figure out is how it can be as big as experts reckon. It is estimated to be about 93 billion light years in diameter and 14 billion years old. If nothing can travel faster than the speed of light surely it couldn't have expanded to be bigger than 28 billion light years wide since the big bang.
Can anyone explain this to me?
Eric Mc said:
blueST said:
Eric Mc said:
That's allways puzzled me too.
Please tell me you're not being sarcastic. I want to feel normal.Edited by blueST on Wednesday 31st December 17:55
It's all to do with the universe expanding and what used to be a light year being different to what a light year is today.
What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
ETA: Pretty decent explanation here: http://www.space.com/scienceastronomy/mystery_mond...
What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
ETA: Pretty decent explanation here: http://www.space.com/scienceastronomy/mystery_mond...
Edited by uriel on Wednesday 31st December 17:57
uriel said:
It's all to do with the universe expanding and what used to be a light year being different to what a light year is today.
What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
Can you point me to something that explains how this works?What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
blueST said:
uriel said:
It's all to do with the universe expanding and what used to be a light year being different to what a light year is today.
What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
Can you point me to something that explains how this works?What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
blueST said:
Anyway, what I can't figure out is how it can be as big as experts reckon. It is estimated to be about 93 billion light years in diameter and 14 billion years old. If nothing can travel faster than the speed of light surely it couldn't have expanded to be bigger than 28 billion light years wide since the big bang.
Can anyone explain this to me?
Perhaps it was 65 billion light years in diameter, at the point of the big bang?Can anyone explain this to me?
How accurate is the 93 billion figure?
I think it's quite simple, unless I've missed something.
The earliest photons of light to be detected by people on Earth originated 13.7 billion light years away. The problem is, in those intervening 13.7 billion years the origin-points themselves have moved away from us.
Imagine shining a torch from a planet at the periphery of the universe 13.7 billion years ago, towards us on earth. That light will only now hit us, but the planet from where the torch was shone has moved away. It is now some 78 billion light years away.
The earliest photons of light to be detected by people on Earth originated 13.7 billion light years away. The problem is, in those intervening 13.7 billion years the origin-points themselves have moved away from us.
Imagine shining a torch from a planet at the periphery of the universe 13.7 billion years ago, towards us on earth. That light will only now hit us, but the planet from where the torch was shone has moved away. It is now some 78 billion light years away.
deeps said:
blueST said:
Anyway, what I can't figure out is how it can be as big as experts reckon. It is estimated to be about 93 billion light years in diameter and 14 billion years old. If nothing can travel faster than the speed of light surely it couldn't have expanded to be bigger than 28 billion light years wide since the big bang.
Can anyone explain this to me?
Perhaps it was 65 billion light years in diameter, at the point of the big bang?Can anyone explain this to me?
How accurate is the 93 billion figure?
No idea how accurate 93 billion is.
Edited by blueST on Wednesday 31st December 18:26
), called A Brief History of Time.Mars said:
I think it's quite simple, unless I've missed something.
The earliest photons of light to be detected by people on Earth originated 13.7 billion light years away. The problem is, in those intervening 13.7 billion years the origin-points themselves have moved away from us.
Imagine shining a torch from a planet at the periphery of the universe 13.7 billion years ago, towards us on earth. That light will only now hit us, but the planet from where the torch was shone has moved away. It is now some 78 billion light years away.
The figures i've given are supposed to have taken all that in to account. the 13.7 billion years is supposed to be the actual age of the universe, not just the oldest object we can see.The earliest photons of light to be detected by people on Earth originated 13.7 billion light years away. The problem is, in those intervening 13.7 billion years the origin-points themselves have moved away from us.
Imagine shining a torch from a planet at the periphery of the universe 13.7 billion years ago, towards us on earth. That light will only now hit us, but the planet from where the torch was shone has moved away. It is now some 78 billion light years away.
The link in Uriel's post is the answer I think, although I can't really get my head round it yet.
blueST said:
uriel said:
It's all to do with the universe expanding and what used to be a light year being different to what a light year is today.
What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
Can you point me to something that explains how this works?What you say is true if you think of the universe as an empty space filled with discrete objects in it that are moving away from each other, but this isn't how the universe works. The usual analogy given is of points on the surface of a balloon being inflated.
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