Travelling at Light Speed

Sorry, I don't mean to sound like a complete ideot, but people all say that if you were to reach the speed of light, time would stop. But then the argument is always that you could never travel the speed of light, since E=mc^2. However, I do have a query about this argument. When you accelerate, you undergo a change in relativistic mass. So therefore, in your frame of reference, would your mass still be the same, regardless of what others see? And in that case would light speed simply be impossible to reach thanks to the great amoutns of energy needed to overcome resistance etc.

I sidetracked a little actually, but anyway I'll take it as given that the speed of light cannot actually be reached. But take this hypothetical situation. If the surface of the Earth (about the equator) was travelling at say 1x10^-8m/s (a third of the speed of light I hope), then would it be theoretically possible to create a really fast space craft to fly against the spin of the Earth at 2x10^-8m/s? The two velocities would add up and the space ship would be moving at light speed, relative to the Earth and vice versa. Using this method is it also not possible to then exceed the relative speed of light? I'm sure that someone must have thought this up already. And if they have, is it a plausable way to one day test the theories of time stopping (relative to the Earth's surface) at the speed of light and also to move back in time (again relative to the Earth)?

Relativistic speeds are used all the time. It is possible to approach the speed of light, or to even pass it by having two things going at close to the speed of light in opposite directions.

In fact, it is that very principle that is applied to particle accelerators.

One particle is sent in one direction at nearly the speed of light, and the other in the other direction at nearly the speed of light. When they collide, they collide at a speed of nearly twice that of the speed of light!

If I remember correctly, the last time I saw, the "fastest" collision was:

1.999999999999994 times the speed of light.

So..what does that mean? Have they worked out what effects are acheived by surpassing this so-called barrier of speed? Or are there none of the predicted outcomes, such as the relative stand-still of time or even reverse of it?

Well, it doesn't really matter - because, it's the energy of two particles, each moving at 0.99999999999997 times the speed of light, that allows such a collision to exist.

An object travelling at or above "c" (the speed of light) can't happen, as you've said.


I guess I'll revert back to the original topic...

As you approach the speed of light, time around you would speed up, although other people would see your time slow down. Thus, if you went at the speed of light, then congradulations, you've reached the end of time (time moves infinitely fast).

Since the particles, however, are not travelling at the speed of light, just very close to it, then no laws are broken. When they collide with each other, they release a lot of energy (kinetic), and are smashed apart into some of the most fundamental forms of matter. This is where the theory of Quarks comes from. Electrons and protons are made of different kinds of Quarks. As you may have guessed, a neutron is simply a particle with the Quarks from both the proton and the electron. There are many hypothosized quarks, and many have been found - but some have not (like the elusive "strange quark").

I don't know - maybe I'm just missing your question - but there are ways to by-pass the light-speed barrier, even though you're not going faster than light-speed. It all has to do with relativistic speeds and positions and such.

For example, warping space. If you put two black holes close together, they'd warp space in really wierd ways There'd also be a point inbetween them where if you travelled through it at high speeds, you'd get to the other side faster than light. However, you've really just shrunk the distance to the other side is what you've done.

The real arguement for not being able to travel light speed if time stopped or slowed, is that speed is distance over time. IF there is no time, how in the hell can you be traveling? And if time slows down, then the distance cannot be the same because if it were to remain the same you would be traveling faster than the speed of light.

we are travelling faster than the speed of light right now relative to light going in the opposite direction as our earth is travelling presently.

One thing peculiar about light (this was taught to me in a USC physics class, so if it is incorrect, please let me know). If you are travelling at 1/2 the speed of light and light travels past you, it would still be measured at the speed of light....go figure.

[edit on 12/15/2005 by sexymon]

The one thing that I have never been able to grasp about this whole relativity thing is relative to WHAT? C is considered to be a constant, but since everything in the universe is moving at different velocities what is C constant to? You figure that the Earth is rotating about it's axis, orbiting the Sun and the whole Solar System is moving within the Galaxy and the whole Galaxy is moving........see where this is going?

Originally posted by Yarium


As you approach the speed of light, time around you would speed up, although other people would see your time slow down.

The faster you go the slower time gets, Time for everyone back on earth remains the same. The Time dialation effect can be vary drastic at near light speed. If you were going very near the speed of light say 99. light speed you could cover amazing distances in a short amount of time for you. You could in thoery travel to the other side of the Milkway in a few months (your time) but for everyone on earth some 100,000 years would have went by.

Carl Sagan once said with time Dialation you could travel the entire universe in a matter of years your time but on earth billions of years would have pasted for everyone eles. You might have to go 99.99999997 light speed to do it though, but theres no law preventing you from doing that.

[edit on 16-12-2005 by ShadowXIX]

[edit on 16-12-2005 by ShadowXIX]

Originally posted by JIMC5499
The one thing that I have never been able to grasp about this whole relativity thing is relative to WHAT? C is considered to be a constant, but since everything in the universe is moving at different velocities what is C constant to? You figure that the Earth is rotating about it's axis, orbiting the Sun and the whole Solar System is moving within the Galaxy and the whole Galaxy is moving........see where this is going?

Relative to anything. Just as sexymon siad, even moving bodies according to Albert will always measure the speed of light at a constant...in a vacuum.

Everything is subject to this constant. Which is why people have a hard time understanding it and why so many questions are asked and why so many people have their own theories contradicting Albert's. Most people think in terms of Newtonian mechanics. When I used to ask my dad about Relativity, he would always tell me my biggest problem was that I thought in terms of Newtonian mechanics and needed to think differently.

There are books that can help cope with this. Even then, books may not be the answer and/or may never be the answer. I think I myself am never going to understand it fully.

The fact that the speed of light travles at a constant speed in a vacum is a direct consequence of Maxwell's field equations that describe electromagnetics. c = 1/sqrt(e0 u0), where e0 and u0 are the permittivity and permeability of free space, respectivley. This is independed of the speed of the emitting source, so even though you'd see a doppler shift, light would still be moving at a constant speed.

You'll never be able to see anything move faster than the speed of light. Special relativity shows that the speed of an object viewed from another moving object is u' = v - u / (1 - uv/c^2), where v is the velocity of the moving object, and u is the second moving object.

So if two spaceships were moving towards each other at a speed of 0.8c, observers on one spaceship would see the other as moving at u = ((0.8 c) - (- 0.8c)) / (1 - (-0.8c)(0.8c)/c^2) = 0.976 c, not 1.6 c as you'd expect from classical mechanics.

As to time freezing... imagine you're in a spaceship moving away from a fixed clock. If you were to travel at the speed of light, you'd catch up to the light emmited from the clock at a certain time, and it would forever appear to show the same time. But time measured from clocks stationary in your reference frame would appear to be ticking along as usual to you. For people at the stationary clock, though, they'd be stopped.

Special relativity is facsinating... as many others have suggested, if you want to know more go to your library and check out a book or two

Imagine microscopic bacteria. In their world the average sized house would seem like the entire universe. Travelling at 1 metre per second would probably seem like an impossibility for them. Now suppose we are those bacteria sized beings, and our universe is the size of an average sized house to some giant millions of light years in height. This giant would be able to travel at the speed of light just be scratching his head. Just something to ponder.

Aye, but those bacteria don't have advanced theories in physics now do they? What I'm saying is that we have rules that we have found so far in most cases to be true to a high degree of probability - and that they apply everywhere. So while we cannot conceptualize the universe, it being so huge and 4 dimensional and all, we still have the ability to try to understand its workings.

The giant would still unable to be able to move at light-speed, since it's not just a matter of pounding the power in and you'll get there. It's a law that applies to everything, big and small.

However, you are right in that when we approach new ideas and theories, we must keep a sense of humility in our beliefs which we must constantly challenge.

I've got a good one for ya: Does Light have mass using E=MC^2

You have voted Yarium for the Way Above Top Secret award. You have two more votes this month.

Thanks Yarium, learnin alot so I hope you keep posting.

My question regarding FTL travel, is the theory than you can achieve it by expanding space in front of you and contracting it behind you. Although we dont have this tech yet, I'm curious if you've heard of this and can explain it.

Originally posted by Charlie Murphy
is the theory than you can achieve it by expanding space in front of you and contracting it behind you. Although we dont have this tech yet, I'm curious if you've heard of this and can explain it.

Theres a bunch of ways in theory you can travel faster then light without actually going faster then light if that makes sense. Its sort of bending the law rather then breaking it. Most of these theories deal with bending or warping space one way or another. The most simple is bending two points in space closer together, Its really a created wormhole.

Think of a piece of paper and punch two holes on opposite sides of the paper, That paper is going to be space. You can think of the distance between holes as many light years. Now you bend the paper till those two hole meet and you have turned that massive distance into a very very short distance. Your craft would step through the hole then expand space back to normal.

Using this method you could in theory cover distances much farther then you could even at lightspeed without ever going faster then light.

You could cheat out lightspeed using this same theory by bending space infront of a ship. Your really making the distance you have to cover shorter so when space returns to normal you could have traveled a distance only lightspeed plus could have taken you if space was not bent.

The first method I suggest would be the better way IMHO since you can shrink that distance down to near zero or zero. You could say travel 4 light years in fractions of a second when your ships is really only going say 60mph to enter the wormhole. Though its likely harder as it would require you to bend space more which would require more energy.


Top Physicists say this stuff could work in theory its no longer pure Sci-Fi. Space can indeed me bent by things like gravity. Blackholes for example take this to the extreme. They are not only bending space they are punching a hole right though it. Infact I have seen one theory were you can go faster then light by going near lightspeed while circling a blackhole and letting the blackhole bend the space for you. You wouldnt really be going anywhere in terms of space just in circles but you might be going back in time.

Let's see - first question, does light have mass according to E=mc^2?

Answer: No. Light has energy without mass - and so as light hits the speed of light, its mass does not increase or decrease (anything times zero is still zero). Thus, E=mc^2 is -void- for objects with no mass. In other words, m = 0, and thus the Energy required to achieve the speed of light = 0.

Next question, "warp speed ahead!". Thanks Shadow for doing a pretty good idea of it. That's the classic view of it. I'm starting to think that there might be a better way of doing it. You mention punching holes and stuff, and that got me confused for awhile.

Anyways, Charlie Murphy, take a sheet of paper. Draw two dots on it. Measure the distance between those two dots. Let's say it's 300000 kilometres (I know that sounds large, but since you're drawing the dots, perhaps 300000 isn't that big a distance for you :cool. If you drove a car between the two points, it'll take you a long time (say you're doing 100km/h, you'll get to the other point in 3000 hours). However, let's say you were to bend the paper, with the paper curling up on the underside, and you keep bending it until the two dots are just 1 metre apart from each other. Driving your car across this at 100km/h will only take you about 0.035 seconds to get to the other point. However, when you snap out the paper so it's flat again, you'll have crossed 300000 kilometres in 0.035 seconds - faster than the speed of light (which does it in 1 second).

Congradulations, by warping the 2-dimensional paper, you have travelled farther in 3-dimensions than the speed of light!

Now, apply this to us 3-dimensional beings warping a 4-th dimension (a dimension above us that we can't see, as opposed to a dimension below us that we can see).

As stated, the likely way of doing this is by using Black Holes, though the specifics of it are not quite solidified yet.

And thank you for voting me for an Above Top Secret Award... but I think those are for the conspiracy nuts that prove something . Thank you though .

Hey, I was wondering again. You know that the speed of light is constant in all frames of reference? Does that mean that even if you could travel at the speed of light, you'd still never keep up with the light emitted from a bulb turned on precisely when you passed it?

Another thing: is it possible that we're multi-dimensional beings with only an understanding of four? Could this explain space warping (like when you travel at high speeds and your mass relatively increases and you "shrink" in the direction of travel)? Imagine you're looking through a slit in a piece of paper. This slit represents ONE dimension (I know it has height, but bear with me). Looking at an object through the slit, some odd stuff happens from the perspective of a one-dimensional being. If you move it away from the paper, it appears to shrink and towards it apperas to grow. If you move it up and down it seems to appear and disappear. Obviously, looking at it from a 3D perspective, it makes perfect sense, but now imagine that we are the 1D being and we are perceiving more the 3D objects. Could this be a likeness to the warping of our own space and time? A bend through dimensions we can't even comprehend.

Thanks you both Shadow and Yarium for your explanations on some FTL travel ideas. I am still having trouble wraping my mind around the concept of the fabric of space-time and how it can be warped. Is this becausse we can't see time, the fourth dimension?

I checked out the Nasa website for info on Warp drives and wormholes and I guess although they are possible we won't be doing them any-time soon.

In regards to Black Holes I thought they suck in everything, including light and compress it very very small.. Even though it's not possible to go to one now, theoretically if we could, would we die instantly and be as small as a quark, or come out on the other side of the hole it "punched out" in a parallel universe?

Originally posted by Charlie Murphy
Thanks you both Shadow and Yarium for your explanations on some FTL travel ideas. I am still having trouble wraping my mind around the concept of the fabric of space-time and how it can be warped. Is this becausse we can't see time, the fourth dimension?

Its some pretty weird stuff if you ask me. Another way to think about it that might be easier to understand. Think of the fabric of space and time as a trampoline its nice and flat. Now imagine putting a bowling ball onto the trampoline. The way the bowling ball distorts the flat surface of the trampoline is the way a massive object like a star or planet would bend space.

A black hole on the other hand would be more like putting something so heavy on the trampoline that it punched a hole through it.

Originally posted by Charlie Murphy

In regards to Black Holes I thought they suck in everything, including light and compress it very very small.. Even though it's not possible to go to one now, theoretically if we could, would we die instantly and be as small as a quark, or come out on the other side of the hole it "punched out" in a parallel universe?

I dont think anyone can answer that question for certian. The thinking goes you would get squeezed down to pretty much atomic spaghetti sort of like tooth paste going through a tube. The weird thing according to people like Stephen Hawking atleast is that Blackholes distort time to such a extent that you might take billions of years to go through it or even never actually make it into the singularity. What might take only hours your time in the black hole would really take place over billions of years to everyone eles. The closer you got to the singularity the slower time would get.


For the sake of argument that you could make it through a black hole unharmed theres a couple of theories on what would happen. Some people think there are white holes somewhere in the universe and if you went into one you would be transported somewhere far away in our own universe. No one has ever found a White hole yet to prove this theory.

Other people think Blackholes really punch a hole right through our own dimension in a whole new one. This theory seems to have more support now with all the newer theories like M-theory dealing with a Multiverse rather then just our own universe.

A blackhole singularity is something people dont even really understand that well that, Since it has infinite mass crammed into zero space its confusing to say the least. Thats pretty much beyond what modern science can explain.

You're starting to get into some very difficult concepts to explain easily... but I'll try. And you're right, space-time is very difficult to understand. Space-time is 4 dimensional, and since we cannot "see" 4 dimensions, we have no concept in mind to help us there. If you were 2-dimensional, totally flat, and I tried to explain to you what up and down was, what heigh was, you would have no clue. It'd be impossible for you to imagine it.

Anyways, now that you understand at least partially the idea of space-time, you can come to see a black hole more for what it is. It's not "sucking" - it's an area where space-time has collapsed into paradox. Take the paper sheet and make it rubber. Now, poke your finger into it. That's the gravitational "dent" in space-time. A black hole goes as far as to make a hole. In truth, it's just infinitely stretched.

The star has become a singularity - a point. It is 0-D (zero dimensions). It has no height. no width, no length. It still has great mass though, and this mass creates the 4-dimensional curvature of space-time. If you were to go into a black hole, you would become part of the singularity as the very essence of your existance is compounded into the point where physics breaks.

Once there, there's no getting out. Game Over - User Wins.

However, this does not mean that the Black Holes do not affect other dimensions. They likely do, but we have no idea how - and travelling through it would not be a way to find out. One of the constants of a black hole is that "no information can escape a black hole". This is important to note, as there are things which could be said to "escape" the black hole - but which don't carry any information about what's inside it.

I can already tell there's that question in your head "I thought nothing could escape!?!". Stephen Hawking came up with a very interesting theory. Near the event horizon of black holes (spinning ones at least - which is turning out to be all), energies become so intense that matter is created (like at the beginning of the universe). However, it creates a particle and an anti-particle (so that energy and mass constants remain the same). These would normally annihilate each other - but the anti-particle is sucked into the black hole before they annihilate each other, while the standard particle is flung away from the black hole at near the speed of light. The anti-particle then zaps away some of the black hole's mass, and the black-hole begins to disitigrate.

However, the particle that flies away tells you nothing about what was inside the black hole - and so no information has "escaped" the black hole.

Now, I'm likely horribly wrong on how those particles are created (sorry, not that much of an expert ), but I do know this holds true. It's why they've been able to create micro-singularities at the world's most powerful particle accelerator, and not have the earth get destroyed - because the black holes disintigrate extremely fast (apparently, the smaller the black hole, the quicker the disinitigration) into 0 mass.

I'd be happy to entertain any other questions you might have!