# Special Relativity - apparent speed

1. Dec 17, 2008

1. The problem statement, all variables and given/known data

I'm at rest. Someone in a space ship is approaching me at a speed of 0.8c.

What speed do I see this person approaching me?

Last edited: Dec 17, 2008
2. Dec 17, 2008

### buffordboy23

What do you think the answer is? Do you have any formulas?

Also, consider the scenario where you are traveling toward the spaceship with a speed of 0.8c as well. Since you are traveling at constant velocity, you can claim that you are at rest. What speed is the spaceship approaching toward you now?

3. Dec 17, 2008

### Dick

You said "someone is approaching me at 0.8c". Then you asked "what speed do I see this person approaching me"? That doesn't even need relativity in any sense. They are the same question.

4. Dec 17, 2008

### buffordboy23

Let's make him think a little bit. =)

5. Dec 17, 2008

### Dick

If you think that's useful, ok. Geez. eprparadox? I think formulas are useless here.

6. Dec 18, 2008

I apologize to all who viewed this thread! There was more to this question and I phrased it incorrectly from the beginning anyways. I also had included formulas and an attempt to solve the problem, but for some reason it wasn't posted. I think I may have accidentally selected a portion of the text and deleted it before confirming the thread.

I'm an idiot, for sure. But not THAT big of an idiot!

But thanks anyways for the responses. That's awful kind of you guys.

7. Dec 18, 2008

### buffordboy23

Do you understand how an observer interprets velocity using special relativity? Based on your question (at least the part that is given), it seems you need help and I wanted to offer a few scenarios to make things clearer.

8. Dec 18, 2008