Perimeter of Black Holes and Time Warping

[mvisvitae]

Is it true that if you park a spaceship in the perimeter or orbit of a black hole that time will change and for every day that goes by on the spaceship about 100 years will go by on Earth and you could watch the earth spin around like a top......

 

[doubletruncation]

I don't know if someone has posted a reply yet, but to answer your question: yes. This is an effect known as the gravitational redshift. It has been observed in our own solar system as a very slight effect (search for the shapiro time delay or "pound-rebka" gravitational redshift experiment). The exact extent of the effect depends on how close you are to the event horizon of the black hole. For the rate to be 1 day/100 year you would have to be almost exactly at the event horizon (you'd be 7*10^-10 times the event horizon radius beyond it, which would be a few meters outside the event horizon of a supermassive black hole like the one at the center of our Galaxy). The time-delay asymptotically approaches infinity as you approach the event horizon. However, note that that assumes that you are somehow staying at a fixed distance from the black hole. If you were freely falling into the black hole, the people on Earth would see you slow down and come to a complete stop as you approach the event horizon, but if you looked back at Earth you wouldn't see an infinite speed up. And also note that once you cross the event horizon it would be impossible to stay at fixed position (you're doomed to fall into the singularity... assuming this is an extremely simple black-hole) - so you don't have to worry about somehow seeing beyond the end of time or some such paradox. If you're interested, and are comfortable with physics/calculus have a look at D'Inverno's book "Introducing Einstein's Relativity", there are plenty of other's as well (for example I really like David Mermin's "Space and Time in Special Relativity" book to first understand special relativity, which you need to know before you can tackle the general theory). <div class="Discussion_UserSignature"> </div>

 

[mvisvitae]

Thanks I am going to look for those books. Do you know what happens when you leave the perimeter and return to normal space - would you be back in real time (the time on earth as it was before you entered the orbit of the black hole) or would you end up in the future?

 

[doubletruncation]

<i>Do you know what happens when you leave the perimeter and return to normal space - would you be back in real time (the time on earth as it was before you entered the orbit of the black hole) or would you end up in the future?</i><br /><br />You would be in the future, so to speak. Same thing happens, by the way, when you undergo any sort of acceleration (acceleration being equivalent to staying stationary in a gravitational field). So for example, this gives rise to the often referred to twins paradox (which isn't really a paradox), where one twin goes off at near light speed, the other stays at Earth. The space-faring twin turns around and comes home and finds that she is younger than the one that stayed here. While the space-faring twin was coasting along at near light speed, it would appear to each twin that time is running very slowly for the other, but when the space-faring twin accelerates to turn around and come home she suddenly sees her twin on Earth age rapidly. When she gets home they will both agree on how old each one is, the twin that stayed at home will be older than the one that went to space. <div class="Discussion_UserSignature"> </div>

 

[mvisvitae]

Very interesting - I have skirted the topic of Age Progression and Age Regression and this answers some questions I had there --- thanks