Halo Jones and the planet Hispus

SimonD

Rouge Element
SimonD
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With Allan Moore becoming a major story teller for Hollywood of late, I've been re-reading some of his comics.

Halo Jones goes to a planet that is so huge that it's gravity slows down time. A day on the planet could be a week in Earth time.

The theory goes, light is effected by gravity and light effects time, therefore time is effected by the large pull of the planets gravity.

Is this possible? Or just a comic writer's bad math?
 
Until the bit about light affecting time it was sort of plausible. Gravity does slow down time, but light has nothing to do with it. Unfortunately, to get a significant amount of time dilation the gravity would have to be so high that you wouldn't have a planet any more, you'd have a neutron star. Also, a large planet would not necessarily have high gravity at its surface, what is important is the density. A neutron star could be about the size of the Earth, but has massive gravity at its surface, while something like Beteguese could be much heavier, but will have much lower gravity at its surface because it is so big.

Incidentally, there is a book about life on a neutron star that is discovered by a human spaceship. When humans arrive life is at a very primitive stage, fairly soon they invent ways to commincate and within a week the aliens have discovered interstellar travel and disappeared, leaving a thankyou message for the nice people who helped their distant ancestors. I'm not sure when it was written, but I suspect that those comics are not original. If anyone happens to know the name or author of that book can they let me know please? I'd quite like to find it again.
 
Cuddles said:
Until the bit about light affecting time it was sort of plausible. Gravity does slow down time, but light has nothing to do with it. Unfortunately, to get a significant amount of time dilation the gravity would have to be so high that you wouldn't have a planet any more, you'd have a neutron star. Also, a large planet would not necessarily have high gravity at its surface, what is important is the density. A neutron star could be about the size of the Earth, but has massive gravity at its surface, while something like Beteguese could be much heavier, but will have much lower gravity at its surface because it is so big.

Incidentally, there is a book about life on a neutron star that is discovered by a human spaceship. When humans arrive life is at a very primitive stage, fairly soon they invent ways to commincate and within a week the aliens have discovered interstellar travel and disappeared, leaving a thankyou message for the nice people who helped their distant ancestors. I'm not sure when it was written, but I suspect that those comics are not original. If anyone happens to know the name or author of that book can they let me know please? I'd quite like to find it again.
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Ta-Da :)

Dragon Egg by Robert Foward
 
General Relativity shows that gravity does slow clocks. A great explanation of that effect does use light.

Leaving out many relevant details, here is the gist of it:
1) A light source of known frequency is placed at the bottom of a gravity well (say the surface of a planet)
2) The light is observed from high above (high enough the gravity is greatly diminished) and the frequency is noted.
3) The light, in its climb out of the gravity well to the observer necessarily loses energy and thus its frequency is reduced (a measure of light's energy is its frequency).
4) To see a light source of known frequency continuously put off light of apparently lower frequency indicates that time must be running more slowly for the light source than the observer.

This is 100% percent confirmed by observation, by the way. Nothing theoretical about it. Clocks at the top of skyscrapers run faster than those at the ground floors. This has been demonstrated by shining a laser up the elevator shaft and comparing the frequency to an identical laser at the top.
 
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Cuddles: I'm pretty sure the author of that novel was Robert Forward. Can't remember the title though.
 
Cuddles said:
Incidentally, there is a book about life on a neutron star that is discovered by a human spaceship. When humans arrive life is at a very primitive stage, fairly soon they invent ways to commincate and within a week the aliens have discovered interstellar travel and disappeared, leaving a thankyou message for the nice people who helped their distant ancestors. I'm not sure when it was written, but I suspect that those comics are not original. If anyone happens to know the name or author of that book can they let me know please? I'd quite like to find it again.
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Didn't they make a ST:Voyager episode like that?
 
Can a rocky planet be massive enough that it would have an appreciable affect on time? (Particularly slowing time by 700%?)

If a planet were that massive, what would it mean to "go to" that planet? Surely a human wouldn't be able to walk on its surface.
 
JoeTheJuggler said:
Can a rocky planet be massive enough that it would have an appreciable affect on time? (Particularly slowing time by 700%?)

If a planet were that massive, what would it mean to "go to" that planet? Surely a human wouldn't be able to walk on its surface.
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No.

Time is slowed by 100% (completely stopped) at the event horizon of a black hole. Slowing something 700% doesn't even make logical sense.

However, like most relativistic effects, time does not get significantly altered until things are very extreme. The gravity at an event horizon would be in excess of 10^12 G's. Whatever the true value is (my google fu failed me), we'll just call it 1 EHG (Event Horizon Gravity) for simplicity. It would take roughly 90% of 1 EHG to slow time by 50%.

A person would be turned into a puddle by 1 millionth of 1 EHG. We will never experience noticable gravitional time dilation.
 
I think that it's fairly likely that a planet dense and massive enough to get that kind of gravity would probably collapse into a black hole, but even if it wasn't, it certainly wouldn't be habitable.
 
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