# Homework Help: Relativity of time

1. Oct 19, 2014

### alizeid

Hi!

I have difficulty with the English language but will try my best. I have recently begun to study the theory of special relativity. , I understand what the relativity of time is, relativity of length and Lorentz transformations. But I still have difficulty with solving data and do not know how I should think. I am grateful if anyone can help me. Let me give an example;

On New Year's Day 2500 gives the astronaut Tom off exploring in the expanse. He takes off with speed 0,6c. After four years of traveling away from the earth (according to him), she witnesses a live television broadcast of the New Year celebrations on earth. This did her to begin long for home. She turns the space ship and steer back toward Earth with the same speed as before, and is home for another four years.

a) How much time has elapsed on Earth during her absence?

b) What is the New Year celebration was Astrid watched on TV before she turned?

c) During the entire trip home sits Astrid front of the TV and giggle when she witnesses the continuous direct broadcast television programs from the earth. How many times quickly moves everything on Astrid's telescreen during her journey home?

I can solve A without any problem and get the right answer but then I want to solve b and c, it becomes total blockage in the brain, a complete misfit. I do not know how to think. Can anyone help me with how to do and think? what steps need to be understood and what is actually happens. I have no ide how to solve b and c. I'am very grateful if someone can help me. Thanking you in advance!!

2. Oct 19, 2014

### Staff: Mentor

Can you show the answer you got for (A)?

How far away was Tom/Astrid when he/she turned around, and which year was on earth then (as seen from earth)?
Did you draw a spacetime diagram?

3. Oct 19, 2014

### alizeid

The solution for a is 10 years. How I came up with this, You can take a look to the picture below.

"How far away was Tom/Astrid when he/she turned around, and which year was on earth then (as seen from earth)?"

the answer is as seen from earth, she is 3 lightyears away from the Earth and and it took five years.

#### Attached Files:

• ###### rel1.JPG
File size:
3.7 KB
Views:
74
4. Oct 19, 2014

### Staff: Mentor

If Astrid is 3 light years away in the year 2505, which new year celebration can she see?
Based on that, she saw X years of television in 4 years. This also allows to answer (c) for one direction, the other direction works in the same way.

5. Oct 19, 2014

### alizeid

sorry, can you explain more. i can't get it:-(

6. Oct 19, 2014

### Staff: Mentor

How long did the TV transmission travel to reach the point in a distance of 3 light years?