The theory of relativity as postulated by Albert Einstein says that velocity slows the passage of time. If one was travelling in a space ship at a speed of ninety nine per cent of the speed of light (which is 186000 mls. per second) tim would pass more slowly inside the space ship than it does here on earth.

For example, if the crew travelled for thirty years, Three thousand one hundred years would have passed on earth. If it was fifty years, four hundred and twenty thousand years would have gone by, when the crew returned to earth whole generations would have been born and died. Is this counted as time travel?

Time dilation is a proven fact, because it has been measured when the space ships travelled to the moon and planets, it was only fractional as the speed only got to 25000mls. per hour. Now they are talking about building spaceships so huge and powerfull they would have to be assembled in space, because when the engines were started they would generate so much heat it would vapourise the oceans. Any budding astronauts??? :shock: :shock: :shock:

i think when the moon astronauts got back, their watches were slightly out of synch. with when they left :)

Building in space is the next leap me thinks as you said hal

Solar sails.

Originally posted by "Sidla"

Solar sails.

wouldnt they blow away :lol:

:roll:

I like the theory that light is infinite and that the light that bounced off the dinosaurs millions of years ago is still travelling through space. If there is life on other planets, its a possibility that they still think the Earth is inhabited by these beasts.
On the reverse of time dilation, if these other life forms travelled toward the earth it would appear that time in the spaceship was travelling incredibly slowly in relation to earth time. If they travelled fast enough, they would see the dinosuars become extinct, the evolution of man and everything in between up until they landed on earth in the present day.
Time dilation is only relative as it is perceived by the viewer in any relative inertial frame. If the guys in the spaceship looked at the earth it would appear to slow down and if they travelled the EXACT speed of light, time on earth would appear to stop. When they returned to earth, the time would 'speed up' in relation to that in the spaceship until they landed. at this point, there may be fractions of difference between their two timepieces.
or something like that....

Talk about bringing up an old thread!

You can't travel at the speed of light though, it's impossible by theoretical phhysics, it would take an infinite amount of energry IIRC to accellerate somethign with ANY mass to that speed.

Wilf

Spaceships that would vapourise the oceans? Where's the story on that? Not heard it.

I'm wondering what happened to the ion drive... a few years ago it was the way forwards and would propel us to nearby galaxies in months, but now they seem to have made it and it doesn't actually do that (though I seem to remember a few japanese spacey things being equipped with it I think)

Originally posted by halevan
The theory of relativity as postulated by Albert Einstein says that velocity slows the passage of time. If one was travelling in a space ship at a speed of ninety nine per cent of the speed of light (which is 186000 mls. per second) tim would pass more slowly inside the space ship than it does here on earth.

For example, if the crew travelled for thirty years, Three thousand one hundred years would have passed on earth. If it was fifty years, four hundred and twenty thousand years would have gone by, when the crew returned to earth whole generations would have been born and died. Is this counted as time travel?

Time dilation is a proven fact, because it has been measured when the space ships travelled to the moon and planets, it was only fractional as the speed only got to 25000mls. per hour. Now they are talking about building spaceships so huge and powerfull they would have to be assembled in space, because when the engines were started they would generate so much heat it would vapourise the oceans. Any budding astronauts??? :shock: :shock: :shock: that is a brilliant post, when i think that in my life time i can recall my grandparents talking about the first motor car as opposed to horse drawn carriages,it makes me think how lucky i am to be born in an age when i was there when the first rocket left earth, television, computers,we have moved at such a fast pace in so little time that i do believe that we will one day conquer space,find cures for cancer and aids,and maybe one day in the distant future realise that killing each other off in wars serves no purpose other than to benefit the politicians and industrialist barons, who is to know where we could be in five hundred years time ?:thumbsup:

Originally posted by BrainThrust

You can't travel at the speed of light though

What about the speed of dark? I believe it's faster than the speed of light.

If I go out on a clearish night and look up to the sky, the first thing I see is darkness, then the starlight starts to seep through. Hence the speed of dark is faster....

Originally posted by SHarper
What about the speed of dark? I believe it's faster than the speed of light.

If I go out on a clearish night and look up to the sky, the first thing I see is darkness, then the starlight starts to seep through. Hence the speed of dark is faster.... yes and where does it go when you turn the lights on ? amazing

Originally posted by BrainThrust
You can't travel at the speed of light though
How does light manage it then? :confused:

Originally posted by Sidla
How does light manage it then? :confused:

Smart arse :P

Let me rephrase.

Nothing with any mass can travel at the speed of light.

Wilf

I thought light had mass though? Otherwise how do black holes work?

Originally posted by Sidla
How does light manage it then? :confused:

Because of its lack of mass.
Think it boils down to :- light, particle or wave?

You can measure the speed of light with a microwave oven and some marshmallows....

The reason for building ships in space is down to physics and the gravitational pull of our planet.

If we had sufficient polymers that where light enough and strong enough we could build ships of immense size on the surface but with current building materials these ships would collapse under there own weight and never make it off the ground.

Build the ship in space where everything is weightless and you get round this problem. Well until some smart arse tries to land it on a planet.

Originally posted by Sidla
I thought light had mass though? Otherwise how do black holes work?

Black holes don;t just work on mass, they are effectively a hole that is infinitly deep on the curvature of spacetime, thats why they affect light, because once on that curve, the laws of physics don't apply.

Once past an event horizon, you can't escape, nor even see the other side, the only thing you can see is the centre regardless from where you look.

Wilf

Is anyone familiar with the idea that light may be slowing down? If this is proven, it could cause some problems for our favourite theory of relativity as well as pretty much everything else we think we know about the universe. :confused:

A couple of random links:

http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=39733

http://www.newscientist.com/article.ns?id=dn1158

Originally posted by BrainThrust
Black holes don;t just work on mass, they are effectively a hole that is infinitly deep on the curvature of spacetime, thats why they affect light, because once on that curve, the laws of physics don't apply.

Once past an event horizon, you can't escape, nor even see the other side, the only thing you can see is the centre regardless from where you look.

Wilf

isnt it just that the light follows the curve of spacetime into the black hole?

This is well described in General Relativity. I think this applies right up to the singularity - and then you need something along the lines of a quantum gravity theory to describe what happens. WHich of course we dont have :(

Originally posted by BrainThrust
Talk about bringing up an old thread!

You can't travel at the speed of light though, it's impossible by theoretical phhysics, it would take an infinite amount of energry IIRC to accellerate somethign with ANY mass to that speed.

Wilf

How could it take an infinite ammount of energy to accelearte something with a finite mass to a finite speed.

I haven't done physics, but that just doesn't sound logical jim.

Originally posted by donkey
How could it take an infinite ammount of energy to accelearte something with a finite mass to a finite speed.

I haven't done physics, but that just doesn't sound logical jim.

As an object that has a non-zero mass approaches the speed of light its mass approaches infinity.

Hence to actually get something to the speed of light would require an infinite amount of energy.

Originally posted by nightrider
isnt it just that the light follows the curve of spacetime into the black hole?

This is well described in General Relativity. I think this applies right up to the singularity - and then you need something along the lines of a quantum gravity theory to describe what happens. WHich of course we dont have :(

Yes, you're exactly right, thanks for explaining that better than I could. :blush:

Donkey: Thats the point, but when has deep theoretical physics obeyed common sense? Logic rarely enters mathematics.

Wilf

What it boils down to is that no one actually knows.

You get these people saying that it is impossible to travel at the speed of light etc, but this is only what you have been told, no one actually knows. Theorys can be wrong.

Just remember, it was once thought that the earth was flat.

Originally posted by spyro2000
Just remember, it was once thought that the earth was flat.

Actually, thats not true. That little bit of history was invented by the Victorians to prove how advanced they were compared to the past.

WIlf

Originally posted by BrainThrust
Actually, thats not true. That little bit of history was invented by the Victorians to prove how advanced they were compared to the past.

WIlf

Fair enough, my point is still valid though. :)

Originally posted by starmag
I like the theory that light is infinite and that the light that bounced off the dinosaurs millions of years ago is still travelling through space. If there is life on other planets, its a possibility that they still think the Earth is inhabited by these beasts.
On the reverse of time dilation, if these other life forms travelled toward the earth it would appear that time in the spaceship was travelling incredibly slowly in relation to earth time. If they travelled fast enough, they would see the dinosuars become extinct, the evolution of man and everything in between up until they landed on earth in the present day.
Time dilation is only relative as it is perceived by the viewer in any relative inertial frame. If the guys in the spaceship looked at the earth it would appear to slow down and if they travelled the EXACT speed of light, time on earth would appear to stop. When they returned to earth, the time would 'speed up' in relation to that in the spaceship until they landed. at this point, there may be fractions of difference between their two timepieces.
or something like that....

this is kinda like half understood bits mixed up with some imagined stuff.
Time dilation is relative that is correct. But the vector is irrelevant, time dilation would occur in the same way if someone were travelling towards the earth at a relative .99 proportion of c.
Although they would appear to see an accelerated slideshow of earths history (if they could resolve images from far enough away).

Surely someone finds the speed of light slowing idea interesting apart from me. I'm starting to think that I'm a bit sad. I got really excited about this and discussed it with a close friend. After I'd finished speaking he calmly said "that's really boring, I'm going to the bar"

Poor me! :(

Originally posted by Yodameister
As an object that has a non-zero mass approaches the speed of light its mass approaches infinity.

Hence to actually get something to the speed of light would require an infinite amount of energy.

You mean it actually gets bigger or denser?

Originally posted by Andy78
Surely someone finds the speed of light slowing idea interesting apart from me. I'm starting to think that I'm a bit sad. I got really excited about this and discussed it with a close friend. After I'd finished speaking he calmly said "that's really boring, I'm going to the bar"

Poor me! :(

Try making a Hollywood movie about it. Or a reality TV show.
Then you'll have my undivided attention Andy.

You guys. You guys.... you're all making this up as you go along aren't you :suspect:
Keep it coming. I like to be reminded how ignorant I am.

:help:

Originally posted by Sidla
I thought light had mass though? Otherwise how do black holes work?

And solar sails come to think of it.

Originally posted by BrainThrust
Actually, thats not true. That little bit of history was invented by the Victorians to prove how advanced they were compared to the past.

WIlf

Nah, surely not...? You're not telling me that humankind has always known that Earth was round?

Of course we did!

You only have to look at the ocean to see that the landscape curves.

We're not stupid, the only reason we believed the earth was the centre of the universe was because of the illusion that the sun revolves around us.

Wilf

I'm pretty sure that Pythagoras proved that the world was round back in acient times.

photons have no resting mass, they do have momentum though when moving (don't ask me to explain why).
Solar sails don't really work on photon pressure though, they work on the solar wind, which is a stream of charged particles being pushed away from the sun.