# On GR and Interstellar exploration

1. Jun 29, 2008

### owenhbrown

Hello folks,

I was wondering about a possible probe sent to alpha centauri which would be able to do a deep scan of the system, maybe for a month, and then send back results.

I then wondered, that if the probe was exposed to different gravitational conditions, lets say favourbly, would information come back sooner than we expected because of a difference in time perception?

2. Jun 29, 2008

### mathman

Alpha centauri is 4.3 light years away. A signal sent back to earth from a probe near that star would take 4.3 years to get here.

3. Jun 29, 2008

### owenhbrown

My question is regarding time spent scanning the system, not time travelling there or back.

I am asking that if the probe is given a month to scan the system, is it possible that, because of relative time, it may require less or more than an Earth month to complete the scan, because the same length of time time near Alpha Centauri moves faster or slower relative to us.

So you see, the issues of interstellar travel were not brought up.

4. Jun 29, 2008

### JesseM

Time runs slower for clocks deeper in a gravity well, so the only situation in which an observer measures a distant clock to run faster due to gravitational time dilation is if the observer is closer to a source of gravity than the clock. I'm pretty sure the gravitational time dilation from the Earth and Sun is too small to make any significant difference in the rate of local clocks vs. distant clocks, but if you imagine an observer on a ship very close to a black hole who is receiving signals from a probe far from the black hole, she could see the signals appreciably sped up.

5. Jun 29, 2008

### Crosson

To give an idea of how small the effect would be, if the probe were to land on the surface of a very small and dense neutron star we might find that it takes 2 months to complete its scan.