# Relativity question

1. Feb 6, 2007

### Karma

Suppose someone from Planet X, In another part of our galaxy, is trying to communicate with the earth. He sends out a message. This is, of course an electromagnetic wave that travels through space with the sepeed of light. Assume that it takes ten years for the message to travel to earth. Twelve years before a radio astronomer on earth recieves the message, the astronomer has received a nobel Prize.

Does this permit us to say that he recieved the prize before the message was sent from planet X?

Last edited: Feb 6, 2007
2. Feb 6, 2007

### ranger

Where does Planet X come into the picture? btw, an effect cannot precede its cause.

3. Feb 6, 2007

### Karma

Sorry about that... they are the same planet...

4. Feb 6, 2007

### ZapperZ

Staff Emeritus
How is this a "relativity" question? In fact, how is this even a physics question?

Zz.

5. Feb 6, 2007

### Karma

there is no absolute time throughout the universe by which absolute simultaneity can be measured

Last edited: Feb 6, 2007
6. Feb 6, 2007

### arunma

Well, there sort of is. For example, we often talk about how the CMB was emitted 300,000 years after the Big Bang, and we say that the universe is 13.7 billion years old. While simultaneity is relative, special relativity does not void the concept of time altogether.

By the way I'm fairly certain that the answer is yes, the astronomer received the prize before the message was sent. As someone else said, I'm not sure that this is actually a physics question.

7. Feb 6, 2007

### ranger

My initial response still holds true.

Edit: OK, I just reread your question and see that you've changed it. So you might not see how the entire cause-effect thing applies to your situation.

8. Feb 7, 2007

### ZapperZ

Staff Emeritus
I still don't see what is "relative" here, or anything to do with relativity. Either you have severely misunderstood "time dilation" in SR, or this has nothing to do with it at all.

Zz.

9. Feb 7, 2007

### jdog

I disagree with everyone. First, this is a perfectly valid question, and I think, a profound one. Second, the simple answer is no, there will exist a reference frame where these events happen in reverse order. This is because the two events, the sending of the signal and the awarding of the nobel prize, are related by a "space-like" interval in "Minkowski space". They happen outside each other's "light cone". i.e. they happen at a proper distance of 10 light years apart, and only two years apart in proper time. If they were "time like" then one could say with certainty that one happened before the other. i.e. If they happened one light year apart (proper length) and 10 years apart (proper time), then no "lorenz transformation" would reverse the order.