"Time Travel"

[warren211]

I hate science. So I won't be getting into these philosophical debates we got going on in this thread.

 

 

 

But I will ask (because curiousity and stupidity is a dangerous combo) if you're traveling faster than light and turn on a flashlight in front of you, what happens?

 

 

 

And sonerohi, I remember that thread. Had something to do with Neutrinos and 10 dementions or something.

[Intriguing]

But I will ask (because curiousity and stupidity is a dangerous combo) if you're traveling faster than light and turn on a flashlight in front of you, what happens?

 

You can't travel faster than the speed of light. However, if you want to know what happens if you're traveling very close to the speed of light and you turn on a torch, I attempted to explain that three posts above you.

[assassin_696]

But I will ask (because curiousity and stupidity is a dangerous combo) if you're traveling faster than light and turn on a flashlight in front of you, what happens?

 

 

 

I could be flippant, but i'll save it and just say that the bolded part is an impossibility so it's a redundant question. Like asking about angels dancing on pinheads...

[Intriguing]

Like asking about angels dancing on pinheads...

 

I can't really imagine angels dancing on pinheads. My view of angels tends to be that of impressively muscular, 10-foot-tall men with flowing locks of almond hair, draping white garments, and disproportionate swords. Those kinds of guys can never dance.

[Yomyth105]

interesting read. i remember watching a discover channel on that :geek: its kool how we see a star explode on earth when in reality that star exploded a while ago.

 

 

 

i have to agree with the other posters though. it would be hard to get something to travel faster than the speed of light. im not saying it is impossible but just incredibly difficult. and just because Einstein said it doesnt mean anything. theories r constantly being improved upon

[anonymous1234]

This got me thinking, if we DID manage to get an object up to 0.99c, and if it had a light on it, and we pointed that light forward, what would happen?

 

Imagine that there is a spaceship traveling at a constant velocity of 0.9999...c through a vacuum, and stationary observer watching the spaceship. At the tip of this spaceship is an astronaut holding a torch. When the astronaut turns on the torch, what happens to the light given off?

 

What happens to the light differs depending on which observer you are--let's start with the stationary observer. Given that the spaceship is practically traveling at the speed of light, and that light cannot exceed 3 x 10^8 m/s, the stationary observer sees the light given off from the torch traveling at the same speed as the spaceship. However, what the astronaut observes is different. The astronaut observes the light from the torch moving out from the spaceship at 1c, relative to the velocity of the spaceship.

 

One would think that this would mean that from the perspective of the astronaut, the light coming off from the torch is traveling at 1.9999...c, but it's not. For this to make sense, I'll use another analogy.

 

Imagine you are in a car traveling on a perfectly smooth road, with the windows covered up to the extent that no light is being let in, and you have earplugs on so that you can not hear sound coming from outside the car. In other words, your senses are completely limited to what is happening in the car. The car is traveling at a constant velocity. In other words, the car is not accelerating in any direction. If you were in this car, you would not know if you were traveling 5 m/s, 5000 m/s, or if you were not even moving. If you are traveling at a constant velocity, you need to have outside reference points (things moving at a different velocity to you) to know how fast you're going. This is the basis of Einstein's Theory of Special Relativity.

 

The spaceship, and therefore the astronaut, are traveling at a constant velocity, and so is the source of the light (the torch). From the perspective of the astronaut, who in relation to the stationary observer is traveling at 0.999...c, the light is traveling at 1c.

 

Our logic would tell us that this is incorrect as a ray of light can not be traveling at two different velocities at the same time. According to Einstein's Theory of Special Relativity, the astronaut flashing the torch from his frame of reference, and the astronaut flashing to torch from the stationary observer's frame of reference are not the same events--they are simultaneous events. The basis of Einstein's Theory of Special Relativity is that things are relative, in that they are not absolute, but dependent on the observer.

 

I apologize if I didn't so a good job of explaining it. It's sort of tricky to get your mind around, but it makes sense once you get it.

 

So if the light is traveling 1c relative to the astronaut, and the astronaut is traveling .999...c, couldn't the light not be moving relative to the stationary observer? :anxious:

[Intriguing]

So if the light is traveling 1c relative to the astronaut, and the astronaut is traveling .999...c, couldn't the light not be moving relative to the stationary observer? :anxious:

 

I'm not sure I quite understand what you mean. From the perspective of the stationary observer, the light is traveling at the same velocity as the spaceship (well, it's moving 0.0001c faster).

[anonymous1234]

So if the light is traveling 1c relative to the astronaut, and the astronaut is traveling .999...c, couldn't the light not be moving relative to the stationary observer? :anxious:

 

I'm not sure I quite understand what you mean. From the perspective of the stationary observer, the light is traveling at the same velocity as the spaceship (well, it's moving 0.0001c faster).

 

Well in this situation I imagined the spaceship going away from the observer, and the astronaut holding the torch shines it directly at the observer. Now I'm really confused #-o

[cadburys_egg]

Well in this situation I imagined the spaceship going away from the observer, and the astronaut holding the torch shines it directly at the observer. Now I'm really confused #-o

 

Any light moving away (or to, for that matter) from an observer would cause red shift. The light wouldnt move any faster or slower, the wavelength would change.

[Lateralus]

Well in this situation I imagined the spaceship going away from the observer, and the astronaut holding the torch shines it directly at the observer. Now I'm really confused #-o

 

Any light moving away (or to, for that matter) from an observer would cause red shift. The light wouldnt move any faster or slower, the wavelength would change.

 

 

 

More specifically, light moving towards an observer would cause blue shift, though the link probably says that.

[anonymous1234]

Well in this situation I imagined the spaceship going away from the observer, and the astronaut holding the torch shines it directly at the observer. Now I'm really confused #-o

 

Any light moving away (or to, for that matter) from an observer would cause red shift. The light wouldnt move any faster or slower, the wavelength would change.

 

 

 

More specifically, light moving towards an observer would cause blue shift, though the link probably says that.

 

I'm still confused, because if the astronaut is moving .999...c, and shines a light, wouldn't the light move 1c relative to the astronaut, which would be 1c + the .999...c of the spaceship, which is impossible.

[cadburys_egg]

More specifically, light moving towards an observer would cause blue shift, though the link probably says that.

 

Blue shift is often accepted as negative red shift (or vice versa), but yes.

 

 

 

I'm still confused, because if the astronaut is moving .999...c, and shines a light, wouldn't the light move 1c relative to the astronaut, which would be 1c + the .999...c of the spaceship, which is impossible.

 

No. Red shift. The wavelength would shift by 0.999c, meaning no matter what colour torch the astronaut was holding it would appear red if hes moving away (I think, I hated special relativity).

[mrpez]

i mentioned this exact same concept in a thread a few days ago...

 

 

 

anyway the telescope idea wont work. some people were talking about being able to see the face of jesus if they were able to capture the light that reflected off of him some thousand years ago.

 

 

 

unfortunately, light particles not only moves forward, but also spreads out. after thousands of years the light particles of jesus' face or anything, for that matter, will have been dispersed effectively enough throughout the universe that no matter how fast the telescope moves, you will never see them.

[Lateralus]

Well in this situation I imagined the spaceship going away from the observer, and the astronaut holding the torch shines it directly at the observer. Now I'm really confused #-o

 

Any light moving away (or to, for that matter) from an observer would cause red shift. The light wouldnt move any faster or slower, the wavelength would change.

 

 

 

More specifically, light moving towards an observer would cause blue shift, though the link probably says that.

 

I'm still confused, because if the astronaut is moving .999...c, and shines a light, wouldn't the light move 1c relative to the astronaut, which would be 1c + the .999...c of the spaceship, which is impossible.

 

 

 

It's difficult to explain without going into the equations and all that, but what it basically comes down to is that if the speed of light is fixed, then it has to be other variables in the equation that change (space/distance and time). As you approach light speed the length of whatever you're in will contract along your axis of movement, and time will slow (relative to a stationary observer). If you were traveling at light speed and turned on the headlights of the vehicle you were traveling in, you would see them as normal, but a stationary observer couldn't see them because the light would never get ahead of the ship. The difference is that space and time change with velocity.

[Lenticular_J]

First off: OMFG I HATE PHYSICS AND SPACE CRAP.

 

 

 

We have to explain all of space with our Terran physics and science, which just isn't enough at this point. Augh, I wish I could look into the future a thousand years and see what the hell they're up to. >_<

[SnWRifleman]

Lol good job everyone. This is a really popular debate :P. I've had 2 super admins on this thread (w00t).

 

All this is pretty confusing to me.

[Shiny]

*Slowly but surely, Mrshinyredplanet backs out of a physic related thread, which doesn't have humour to it. Good job*

 

 

 

Time travel. Uhh....I tried to red the first post, and got lost. All i know is that the have disapproved of some of Herr Einstein's theories. Apparently theres matter which travels faster than the speed of light, which makes up the stuff before the light comes. :?

[EdgedThesis]

Sorry if other people wrote this.

 

 

 

I'm pretty sure the only light you could catch even with ftl speeds would be bright ones. Otherwise there would be way too much interference. So, you could see a brilliant supernova, or a sun being born--- but not Caesar's march on Rome.

 

 

 

It would be cool to have archives on our history from THIS point on however. Installation of mirrors at precise points in the DEEP vacuum of space, far away from other points of light. If the light paths are clear enough, future generations can glimpse the earth as it was way back when.

 

 

 

With multiple mirrors placed farther and farther away, you can have a chronicle that is based upon bouncing photons and what not.

 

 

 

Anyway...

[SnWRifleman]

No, light's speed is a constant. It's all the same and not any different from another light's speed.

[Lateralus]

No, light's speed is a constant. It's all the same and not any different from another light's speed.

 

 

 

By 'catch' he meant to form an image from it.

[SnWRifleman]

Oh..

[Intriguing]

No, light's speed is a constant. It's all the same and not any different from another light's speed.

 

Not exactly. The speed of light can very depending on the medium through which it travels. The speed of light as used in equations, or c, is the speed of light in a vacuum. Not really relevant to the conversation, but I thought it was worthwhile making that clear.

[cadburys_egg]

No, light's speed is a constant. It's all the same and not any different from another light's speed.

 

Not exactly. The speed of light can very depending on the medium through which it travels. The speed of light as used in equations, or c, is the speed of light in a vacuum. Not really relevant to the conversation, but I thought it was worthwhile making that clear.

 

Plus light travels in wavelets so it wont all arrive at the same point at the same time (though the timing is so minute, it may as well be) and since these wavelets deviate a lot and dont always follow the shortest path available, this will also affect its overall speed.

[Will H]

But what about worm-holes? I've heard that you can 'skip' distances by folding space, and then you could view the light that got through the long way round, taking hundreds of years to do so. Then you could view the Earth with your insanely powerful telescope and see it as it was hundreds of years ago.

 

 

 

Why do people think that the 'light barrier' has to be broken?

 

Theoretically it is possible to use wormholes for time travel and what not. However, as of yet no wormholes have been observed, and I am under the impression that there are some additional problems that would ensue even if one were to stumble upon a wormhole. The point is that until we are actually able to observe wormholes, they have no practical application.

 

Well, no. But until we observe time travel, that doesn't have any practical application either.

[onuasdad]

I despise astrnomy becasue it makes methink of the acopolypso, but I know a lot about it.

 

 

 

The stars give off LIGHT, but the star was first created, we earth humans couldent see it because it was so far away and the light didnt reach earth yet. Once I went to a planetarium and the guy said that people invented a way to see the present, but it's classified, but they showed us a few stars that are non existnt and some places where there are stats but we can't yet see them.

 

 

 

This dosent have much to do with time travel, but time travel is possible with bening space time, as confirmed by Einstein. Things that are sucked into a black hole are pushed out at another end, called a white hole, and the white hole is in a different time than the black hole. Scientists have tried to send machines to try it, but Stephen Hawkins (o w/e he is) says that the black hole would collapse before the destination would be reached, leaving the machine stuck inside the tunnel stuck in the black hole, leaving nothing there to be done.

 

 

 

Also, The pressure of being inside the tunnel/black hole would be so great that even a MASSIVELY powerful thing designed to survie EXTREME conditions would be cut off from all forms of electricity, andby electricty I mean batteries also.