# SR and Time dilation problem

1. Mar 31, 2005

### The Rev

I don't know how to reset the time on my clock, but I do have a spaceship that can go as fast as 0.9C. How fast and how far will I need to go this weekend to properly reset my clock.

:rofl:

The Rev

2. Apr 1, 2005

### JesseM

Is this a homework problem? If so you should ask in the homework forum...if not, what's it from?

3. Apr 1, 2005

### Janus

Staff Emeritus
Is your clock of the 12 hr or 24 hr variety?

4. Apr 1, 2005

### Creator

At 2 a.m. on Sunday morning set your clock forward to 3 a. m. That ought to take care of things... :rofl: And don't be late for church.
Creator

Last edited: Apr 1, 2005
5. Apr 1, 2005

### The Rev

It's just for fun. I thought it would be amusing to post this, considering that a) it's daylight savings time this weekend, and b) since there are so many "what if?" questions about this or that SR scenario (usually in reference to a paradox). That's all.

The Rev

6. Apr 1, 2005

### JesseM

Ah, I had forgotten about daylight savings time, thanks for reminding me. OK, so if your clock is an hour ahead, why not just take trip away from earth and back at 0.866c for two hours, during which time your clock will be ticking at half the rate as clocks on earth?

7. Apr 1, 2005

### Janus

Staff Emeritus
Aah, but this weekend you need to set your clock ahead not back. Using this method will have your clock two hrs off the Clocks on Earth(1 hr due to time dilation, and 1hr due to the Earth Clocks being set forward an hr).

This is why I asked whether the clock was the 12 or 24 hr type.

For a 12 hr clock you want your clock to advance 13 hrs for 24 on the Earth clocks, (for instance, if both clocks read 12:00 when you leave, the Earth clock will read 12:00 again when you return having completed two cycles while your clock reads 1:00. When the Earth clocks are then set ahead for DST,the Clocks will match.

If your clock is the 24 hr type (either military or distinguishes between AM and PM), then you would wnat your clock to advance 25 hrs while 48 hrs pass on the Earth.

If it has a date function you'll have to travel for 2 years Earth time to reset the clock properly and if it also has the day of the week, you're screwed, because you'll have to travel for 54 years Earth time (28yr and 1 hr for you). If it keeps track of the last two digits of the year and leap year adjustments, just throw it away and buy a new one after the clocks change, otherwise you'll be gone for 400 yrs by your time, by which time our whole calendar may have changed.

For a 12 hr clock you'll need to travel at about .8406c
for a 24 hr clock you'll need to travel at about .8537c

8. Apr 2, 2005

### The Rev

You guys rule!

The Rev

9. Apr 3, 2005

### HallsofIvy

Staff Emeritus
This was originally posted on April 1, of course.