So apparently time stops at the speed of light?

[Macflash]

But why would the speed at which you are travelling affect the degeneration rates of your cells and other such things? Surely you still would age and change normally to yourself, but travelling at the speed of light makes those changes appear to others to be happening really really slowly?

Yes, you would age normally to yourself, but others would see you as aging slowly. Its all about perspective. To you they would appear to age really quickly, but they would see themselves as aging normally. (also, this only applies to moving near the speed of light, because you can't really get all the way there without something that we would consider magic currently.)

this time dilation happens because the speed of light is constant and always appears to move at the same speed no matter your speed, so for light to look like its moving at the speed of light, your relative time would have to slow down. so if you were going .99999 the speed of light, a mirror would work just as it normally did, there would be no noticeable time lag, to you. to an observer who was not moving the speed of light they would notice the slight lag that is happening to you, since time is still moving normally for them.

 

[MelasZepheos_v1legacy]

Ouch, I think you've just killed my brain. Thanks al-ASSUMING DIRECT CONTROL.

Second time I've seen you do that in a minute. Loving the ME reference though, so I won't complain.

Anyway, OT:

As I understand it, this is a lot of the justification between ahard sceience approach to Faster-Than-Light travel, since if you achieve a speed which is FTL, then you must also be moving in a direction at a pretty rapid velocity, but since travelling at the speed of light does not mean going back in time, you would instead arrive at your destination at almost exactly the same time you set off (depending on the point of origin and distance travelled.) If you were travelling across the galaxy, it could still take years, if you only travelled at exactly the speed of light

To clarify, if you travel at the speed of light across a distance of one year, you will not reverse time, you will instead arrive a year later than when you set off. If you travelled at twice the speed of sound, half a year, four times, quarter (I think, it's late and my maths is wonky). It's only when you travel at significantly faster than the speed of light, across a much shorter distance, that you may appear to travel back in time as well.

Let's tone the examples down to human sized. If you travel at the speed of light from one point to another one metre away, you will arrive as you leave (basically teleportation) because you have gone faster than the light can travel over the distance, but still have had to accomodate for the time it took to actually travel. In order to arrive before you leave and see yourself, even at such a small level, you have to go so significantly faster than the speed of light that the mind boggles at the speeds needed.

Basically, I also remember an Einsteinian thought experiment which posited exact reasons why one could not arrive at a place before you had set off, so if we ever did achieve this phenomenon, it would destroy all of space/time.

 

[cyro_349]

Ouch, I think you've just killed my brain. Thanks al-ASSUMING DIRECT CONTROL.

Second time I've seen you do that in a minute. Loving the ME reference though, so I won't complain.

Anyway, OT:

As I understand it, this is a lot of the justification between ahard sceience approach to Faster-Than-Light travel, since if you achieve a speed which is FTL, then you must also be moving in a direction at a pretty rapid velocity, but since travelling at the speed of light does not mean going back in time, you would instead arrive at your destination at almost exactly the same time you set off (depending on the point of origin and distance travelled.) If you were travelling across the galaxy, it could still take years, if you only travelled at exactly the speed of light

To clarify, if you travel at the speed of light across a distance of one year, you will not reverse time, you will instead arrive a year later than when you set off. If you travelled at twice the speed of sound, half a year, four times, quarter (I think, it's late and my maths is wonky). It's only when you travel at significantly faster than the speed of light, across a much shorter distance, that you may appear to travel back in time as well.

Let's tone the examples down to human sized. If you travel at the speed of light from one point to another one metre away, you will arrive as you leave (basically teleportation) because you have gone faster than the light can travel over the distance, but still have had to accomodate for the time it took to actually travel. In order to arrive before you leave and see yourself, even at such a small level, you have to go so significantly faster than the speed of light that the mind boggles at the speeds needed.

Basically, I also remember an Einsteinian thought experiment which posited exact reasons why one could not arrive at a place before you had set off, so if we ever did achieve this phenomenon, it would destroy all of space/time.

Thoretically you wouldn't be in two places at once, you would just appear to be in two places. Because you moved at a speed FTL you would see the the reflection of light off youself where you were before you moved (that is if you were able to see where you were standing before light catches up to you)

 

[Inverse Skies]

At lightspeed, relativistic effects become unignorable, and due to the way that the equation is written, the mass of an object at lightspeed is essentially infinite, which is impossible. Hence why lightspeed travel is ALSO impossible.

On this equation, v is velocity and c is the speed of light. As you can see, as the value of v approaches c, the Lorentz factor of the object represented by gamma becomes greater and greater. As it is clearly impossible to divide by zero in a way that does not introduce infinities, the mass of the object also becomes infinite. Let's put our resulting Lorentz factor value into the following equations:

,
Where E is energy, m is mass, and c is the speed of light.

Lightspeed is actually not obtainable because the closer you get to it, the more energy that is required to accelerate the object further, the energy required basically being in
finite as well.

That's a very concise explanation, thankyou! It's curious to find that it's actually impossible to reach the speed of light thanks to the energy input required to reach that state being impossible. I wonder what implications that has for travel in space? I suppose the long held science-fiction view of wormholes would be the only feasible way to travel long distances then, whether that is possible or not...

 

[aaronmcc]

Ok, well aside from the Big Crunch being dis-proven already it is clear there is a lot we don't understand but it's still fun to chat about.

I've got one that will bake your noodle...

Alledgedly, a positron is an electron travelling backwards in time. Therefore, there exists the possibility that every electron in the universe is the same electron having travelled back and forth in time sufficiently to populate the entire universe with itself.

faceplant

Since when was the big crunch disproven?!?!?!

well, they taught it to me at school but while i was at uni, about 6yrs ago, they figured the universe will expand continually.

 

[aaronmcc]

Alledgedly, a positron is an electron travelling backwards in time. Therefore, there exists the possibility that every electron in the universe is the same electron having travelled back and forth in time sufficiently to populate the entire universe with itself.

This sounds like something a physicist said while he was drunk, and a sci-fi writer overheard him and took it as fact. Even if it were true, your personal atoms are not 14 billion years old. Electrons randomly appear and disappear all the time. No single particle is going to survive the entirety of the universe.

doesn't the possibility exist that they disappear because they become positrons?

how do know how old an electron is? i'm genuinely interested.

 

[escapistrules]

well for starters, light is a form of energy that travels in waves, so the rules that apply to matter don't apply to it. they say time stops at the speed of light if you were going that fast because it appears to be stopped. your moving so fast and everything around you is moving so slow, it would seem that all around you has stopped.

part two is interesting, im not sure how to answer that.

 

[lacktheknack]

Yes. If you were somehow travelling at the speed of light time would appear to you to have stopped. Everyone else looking at you would be all like "How the fuck is he going at C?!"

Oh, I see. It's because light can travel in waves, and waves don't have mass. That's why waves are the only things that can travel at the speed of light. E=MC[sup]2[/sup] and all that means that it's impossible to reach it anyway. The faster you go the more energy you need to make you go faster. You can never get there. You can get damn close, but never there.

It's like walking half way from point A to B. Then half again. Then half again. Then half again. And each time it requires significantly more energy to halve the distance between you and B. You'll never get there. No matter how much energy you have.

Or something. I'd ask Harbinger here bef-

ASSUMING DIRECT CONTROL.

MY ATTACKS WILL TEAR YOU APART.

WE ARE YOUR GENETIC DESTINY

ALL YOUR BASE ARE BELONG TO US.

Sorry. It couldn't be resisted.

 

[Phatnpround]

Its all relative. If you were to travel at the speed of light (which would require an infinite amount of energy to get there so lets instead say 99.9999999% the speed of light) then to YOU everything else would have stopped. This is because to YOU everything else is moving at 99.999999999% the speed of light and time flows slower in reference frames that are moving fast relative to your own. It starts messing with your head when you think about the people ow are "not moving" ie, the people on Earth. When they observe you, you are the one that is moving fast so they see that in fact time has slowed down for you. So basically, people on Earth see you as aging slower than them, and you see them as aging slower than you. Which is very confusing. This paradox is solved by the fact that if you were to slow down and then turn around and go back you have had to accelerate (declelerate) and this acceleration has a complicated effect on the relativistic effects. It would mean that, say 5 years had passed for you but 500 years could have passed on Earth.

Also, as light is moving at the speed of light that means light has no concept of space or time. To a photon the length of the universe is 0 and it therefore takes no time to get anywhere: but of course, relative to you, it does xD

 

[Phatnpround]

Also, in answer to your second question: it's kind of irrelevant. It requires an infinate ammount of energy to get to the speed of light and you cannot go faster than it. Interestingly the theory does allow particles to exsist that travel faster than the speed of light except they can ONLY travel faster, nothing can cross the speed barrier of 3x10^8m/s it seems. Of course, this is purely theoretical and physists do not think these particles exsist but... they might I guess... also they would go through time in the opposite direction to us, so yes, they would travel back in time.

 

[escapistrules]

Alledgedly, a positron is an electron travelling backwards in time. Therefore, there exists the possibility that every electron in the universe is the same electron having travelled back and forth in time sufficiently to populate the entire universe with itself.

This sounds like something a physicist said while he was drunk, and a sci-fi writer overheard him and took it as fact. Even if it were true, your personal atoms are not 14 billion years old. Electrons randomly appear and disappear all the time. No single particle is going to survive the entirety of the universe.

doesn't the possibility exist that they disappear because they become positrons?

how do know how old an electron is? i'm genuinely interested.

there may be truth in both. one law of life is that nothing is created from nothing (except for the big bang somehow), and nothing can be destroyed till there is absolutely nothing left. it could be possible that electrons could become positrons, but the question is were do we get more electrons. in order to have an atom, it must have a nucleus with electrons orbiting it, the number of electrons must equal the number of protons to keep at a neutral charge. if all electrons become positrons, then all atoms would have a positive charge due to the lack of electrons orbiting it. so if electrons become positrons, and we still have the same number of electron floating around atoms, then isnt it just as possible that at the same time positrons are turning back into electrons so that the atoms stay with the same charge. this is just my point of view and the way i was taught, so feel free to correct me if im wrong.

 

[Goro]

Dearie me...
Time does not stop at the speed of light, I think you're confused with the singularity of a black hole. And that's dilation as it refers to relativity. There is nothing physically stopping travel in both directions of the time axis, but you'd never know because it would affect you too, unless of course the multiverse allows you to step into dimesions where different observations have been made of the state of the quantum vacuum. Simple, huh?
And a group of french physicists has made a 'photon trap' that slowed a photon to about 7 km per second, using mostly mirrors and magnets. I love fundamental particle physics, go out and buy The Universe by John Gribbin, it'll fry your mind.

 

[Rachet922]

This is worse than dividing by zero... My brain hurts.

 

[Outright Villainy]

Yes. If you were somehow travelling at the speed of light time would appear to you to have stopped. Everyone else looking at you would be all like "How the fuck is he going at C?!"

You have it backwards. If you were traveling at arbitrarily close to the speed of light (I refuse to say "exactly"), you would see a billion years of events occur in the blink of an eye. Outside observers would see you frozen like a statue, rocketing through space. You would be stuck watching the universe in fast-forward until you collide into something and lose enough momentum, or until you disintegrate from proton decay.

Apologies if somebody else already answered this.

Alledgedly, a positron is an electron travelling backwards in time. Therefore, there exists the possibility that every electron in the universe is the same electron having travelled back and forth in time sufficiently to populate the entire universe with itself.

This sounds like something a physicist said while he was drunk, and a sci-fi writer overheard him and took it as fact. Even if it were true, your personal atoms are not 14 billion years old. Electrons randomly appear and disappear all the time. No single particle is going to survive the entirety of the universe.

Believe me, you'll die of old age long, long before your protons decay, physical laws are constant in all reference frames, so your atoms will decay as normal in your frame. Measuring the increased time to decay of muons was one of the first experimental confirmations of time dilation actually: http://en.wikipedia.org/wiki/Time_dilation#Velocity_time_dilation_tests

The single electron universe was also Richard feynman's idea, though it held more credence at the time. According to wikipedia anyway, to be honest, I've heard of that theory before, but no little to nothing of it...

 

[Blimey]

Woah. You just turned my brain inside-out and fucked it hard...I'm still trying to comprehend the concept.

 

[blalien]

Alledgedly, a positron is an electron travelling backwards in time. Therefore, there exists the possibility that every electron in the universe is the same electron having travelled back and forth in time sufficiently to populate the entire universe with itself.

This sounds like something a physicist said while he was drunk, and a sci-fi writer overheard him and took it as fact. Even if it were true, your personal atoms are not 14 billion years old. Electrons randomly appear and disappear all the time. No single particle is going to survive the entirety of the universe.

doesn't the possibility exist that they disappear because they become positrons?

how do know how old an electron is? i'm genuinely interested.

there may be truth in both. one law of life is that nothing is created from nothing (except for the big bang somehow), and nothing can be destroyed till there is absolutely nothing left. it could be possible that electrons could become positrons, but the question is were do we get more electrons. in order to have an atom, it must have a nucleus with electrons orbiting it, the number of electrons must equal the number of protons to keep at a neutral charge. if all electrons become positrons, then all atoms would have a positive charge due to the lack of electrons orbiting it. so if electrons become positrons, and we still have the same number of electron floating around atoms, then isnt it just as possible that at the same time positrons are turning back into electrons so that the atoms stay with the same charge. this is just my point of view and the way i was taught, so feel free to correct me if im wrong.

Okay, I'll take this one point at a time:
1. There is no way to tell how old an electron is. You can't keep track of them either because they tend to teleport from place to place.
2. An electron can't become a positron. Electrons can turn into other particles, but a positron is not one of them.
3. Quantum physics would disagree with your "nothing can come from nothing" statement. Even an empty vacuum has some amount of energy. And this energy has a degree of uncertainty. So an empty spot in the universe might have a surge of energy and spawn an electron. It will also spawn a positron to balance it out. Sometimes photons transform into other particles. This happens most often in high-energy locations, such as the center of the sun. All matter in the universe was produced this way, because matter couldn't exist when the universe was too small.

A lot of people don't understand the Big Bang because they believe the universe could not come from nothing. (This statement is a bit misleading. If you ask about what happened "before the Big Bang", you might as well be speaking gibberish. You get the idea, though.) But the universe is nothing, or at least almost nothing. There is a lot of stuff in the universe. But there is also a lot of negative-stuff. For example, when a bunch of gas particles form together and become a star, massive amounts of energy is produced. In this sense, a star (or at least the gravity that holds it together), actually possesses a negative amount of energy. If you take all the negative energy of every star in the universe, it is possible (but we're not completely sure) that it cancels out everything else. So it is possible that the total energy of the universe is exactly zero.

 

[benoitowns]

I'm confused, if time stops at the speed of light, then how can it take any amount of time for light to reach point A to point B? For example the speed of light is exactly 299,792,458 meters per second, and it takes 8 minutes for the suns light to hit earth, and for some stars light to get to earth it takes millions, and sometimes billions of years. If time stops at the speed of light, then how come it takes time for light to reach us? It seems to make more sense that time goes very slow at the speed of light.

Second question, theoretically, if you went faster than the speed of light you would go back in time, if you were to go faster than the speed of light, and lets say that the time it takes you to get from point A to point B is five seconds backwards in time, would you see your self before you traveled if your ending point (point B) at point B, if it was close enough ahead of your self to see (two meters ahead of your starting position for example)? (Obviously end up two meters ahead of your self at the speed of light you would not go in a straight line, you would travel far out and then back, almost make a circle, accept you would end up two meters in front of your original position when you stopped)

You are confused, the light is experiencing the slowed time, while in actuality it is moving at its own speed, the speed of light. But it is very confusing, like how sub atomic particles and not just particles but waves, and by observing them causes them to change.

 

[Regiment]

I'm confused, if time stops at the speed of light, then how can it take any amount of time for light to reach point A to point B? For example the speed of light is exactly 299,792,458 meters per second, and it takes 8 minutes for the suns light to hit earth, and for some stars light to get to earth it takes millions, and sometimes billions of years. If time stops at the speed of light, then how come it takes time for light to reach us? It seems to make more sense that time goes very slow at the speed of light.

Time is relative. If you were travelling at the speed of light, you would appear frozen in time to anyone observing you. From your point of view, all time would pass instantaneously. However, you're still traveling at C. Time only stops from a certain point of view; the light still moves.

Mathematical explanation: Time dilation. Time passes at a speed determined by the acceleration of your reference frame. These effects work on any scale. Technically, a man who spends his entire life jogging will die before his identical twin who spends his entire life sitting on the couch. At non- relativistic speeds (speeds far below C), these effects are insignificant. As your speed approaches C, time passes faster for you. Now, it's impossible for anything of nonzero mass to travel at C, but if you traveled appreciably close to C time would effectively stop for you.

Second question, theoretically, if you went faster than the speed of light you would go back in time, if you were to go faster than the speed of light, and lets say that the time it takes you to get from point A to point B is five seconds backwards in time, would you see your self before you traveled if your ending point (point B) at point B, if it was close enough ahead of your self to see (two meters ahead of your starting position for example)? (Obviously end up two meters ahead of your self at the speed of light you would not go in a straight line, you would travel far out and then back, almost make a circle, accept you would end up two meters in front of your original position when you stopped)

You can't go faster than the speed of light. This isn't just naysaying; going faster than C has no meaning. It's like weighing -10 kilograms, or living for -37 years. Mathematically, you wouldn't go back in time anyway. The math breaks down when traveling at speeds greater than C.

 

[Uberjoe19]

At lightspeed, relativistic effects become unignorable, and due to the way that the equation is written, the mass of an object at lightspeed is essentially infinite, which is impossible. Hence why lightspeed travel is ALSO impossible.

On this equation, v is velocity and c is the speed of light. As you can see, as the value of v approaches c, the Lorentz factor of the object represented by gamma becomes greater and greater. As it is clearly impossible to divide by zero in a way that does not introduce infinities, the mass of the object also becomes infinite. Let's put our resulting Lorentz factor value into the following equations:

,
Where E is energy, m is mass, and c is the speed of light.

Lightspeed is actually not obtainable because the closer you get to it, the more energy that is required to accelerate the object further, the energy required basically being in
finite as well.

That's a very concise explanation, thankyou! It's curious to find that it's actually impossible to reach the speed of light thanks to the energy input required to reach that state being impossible. I wonder what implications that has for travel in space? I suppose the long held science-fiction view of wormholes would be the only feasible way to travel long distances then, whether that is possible or not...

'Twas my pleasure, mate. I like making people learn while on the Internet.