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# cant travel faster than light... watch

1. (Original post by Biffy Clyro)
My friend came up with a good one.

Your driving along in your car and you turn on the headlights so therefore the light from them is travelling at light speed + 30mph.
No it's not, it's still travelling at the speed of light.
2. (Original post by Stikatoo)
No it's not, it's still travelling at the speed of light.
Speed of the light is the fixed constant of the univers, all other speeds are measured relative to it.
3. (Original post by Morgoth)
ok, so if einstein says you cant travel faster than light as you'd see youself leaving when you arrive...then howcome i can see planets millions of miles away that are images of things that happen say 100+years ago?? surely if i traveld faster than light the saw myself leaving all id be seeing is a past image, not an actual new event...

any one explain this a bit... i dunno, but thats gotta be a little bit wrong

I totally disagree with einstein here,

You can't seriously tell me that hypothetically, in the future we create a spaceship capable of reaching the speed of life theres going to be an auto-restrict on the accelerator? Theres nothing to stop you accelerating... !
also once you'd arrived, you would of stopped and watching light arive is incapable to the human eye anyway so you wouldnt see anything freaky,

unless it was like a glowstick type thing where you saw a trail....

But in the future i think the speed of light will be breakable.
4. Light is a constant in all frames of reference. That is what Einstein said and then all the other stuff followed so no, light coming from a car isn't going faster.
5. (Original post by President_Ben)

As you approach the speed of light, you'd need infinite energy because your mass approaches infinity.

the speed of light is fixed though, it isnt infinite.
6. Stikatoo- My friend wasn't being serious when he said that

Im not about to argue that you can create speeds faster than the speed of light by driving in your car with the headlights on.
7. (Original post by Biffy Clyro)
Stikatoo- My friend wasn't being serious when he said that

Im not about to argue that you can create speeds faster than the speed of light by driving in your car with the headlights on.

Fair enough...

erm...I have a sense of humour really!!
8. (Original post by Daban)
travelling at the speed of light obviously requires huge amounts of energy, if some genius did one day find out how to do so, there would be no material in this universe to withstand such energy
(Original post by Stikatoo)
Whilst a lot of the above physics is very true, I thought that the problem wasn't travelling faster than the speed of light but it being near impossible for a mass to accelerate to the speed of light.

Any mass already travelling at c can continue to do so.
(Original post by Daban)
very true
Not very true.

"travelling at the speed of light obviously requires huge amounts of energy"

In relativity, if something is obvious, it's usually wrong. This applies here. It doesn't require huge amounts, it is simply not possible. That's why I avoided using the word "infinite" earlier, because people equate that to "huge amounts". I said "no finite amount can accelerate a mass to the speed of light".

It's not "near impossible", it IS impossible.
9. (Original post by El Scotto)

the speed of light is fixed though, it isnt infinite.
I know that, nothing I said contradicts that either!!
10. (Original post by El Scotto)

I totally disagree with einstein here,

You can't seriously tell me that hypothetically, in the future we create a spaceship capable of reaching the speed of life theres going to be an auto-restrict on the accelerator? Theres nothing to stop you accelerating... !
also once you'd arrived, you would of stopped and watching light arive is incapable to the human eye anyway so you wouldnt see anything freaky,

unless it was like a glowstick type thing where you saw a trail....

But in the future i think the speed of light will be breakable.
"I totally disagree with einstein here"

This is probably where you're going wrong. There is an auto restrict on the accelerator, and there is plenty of evidence. Read what you just wrote, its just denial with no justification.

Momentum is NOT linearly dependant on velocity, so there's nothing stopping you from exerting a constant force on a mass, the momentum will still increase steadily, but the resulting acceleration will tend to zero as the velocity tends to c.
11. (Original post by john!!)
It's not "near impossible", it IS impossible.
nothing's impossible because there is an infinite amount of time for it to happen in. I went back and added the word 'near' because we don't know what can be achieved in the future.
12. Everything in the universe is travelling at the speed of light. However that speed is split across several dimensions - time and the physical dimensions (spacetime).

Imagine a car travelling from one end of the 100m section of an olympic race track to another in a straight line at 25 metres per second - it would reach the other end of the track in 4 seconds.

Now imagine it's travelling from the left handside of the start line, to the right hand side of the finish line at the same speed - it would take longer to get to the finish line because the car is travelling a longer (diagonal) route. The car is still doing 25m per second but the speed of 25m per second is split accross 2 dimensions, forwards and sideways.

An object in the universe is travelling through time and the 3 physical dimensions. Most of the speed is taken up by the movement through time, therefore the speed through the 3 other dimensions seems so much slower.

Light on the other hand, as I understand it, only travels through one dimension - time. Therefore it is travelling at.... the speed of light. Correction to this - see post further down the thread.
13. (Original post by Stikatoo)
nothing's impossible because there is an infinite amount of time for it to happen in. I went back and added the word 'near' because we don't know what can be achieved in the future.
Firstly, time isn't necessarily infinite. If the Big Crunch models are correct, then 'tisn't. And even if they're not, the human race [probably] won't last forever. We have a few billion years until the sun goes red giant and the Earth boils away. But survival isn't necessarily impossible, and I'm sure that even generation ships could establish extra-solar colonies given that sort of timescale...But then again, just around that time the Andromeda galaxy'll hit us, and we'd need some kickass technology (or biology...who knows what we'd evolve into by then, assuming we [or rather, our descendants] will still be around even then) to survive that. But I digress...

There are plenty of impossible things. Man cannot fly by the power of thought alone (and anyone who retorts that someone had to think of an aeroplane/helicopter/whatever, then they should also notice that the ideas didn't make the person 'fly', but rather the machines had to be built and it was the machines that flew and the people merely sat/stood/lay down/dancedtheCharlston inside the flying machine...and anyone who retorts that in the future there might be neural interfaces for anti-gravity underpants then...well, there might. But not now. And even then, it'd be the anti-gravity underpants doing most of the work, not the actual thoughts (unless they work by harnessing the power of thought, but again I digress.)

Anyway, back to the point at hand. In our observed four-dimensional universe, it is impossible to accelerate anything with the property of mass to the speed of light, nevermind beyond it. That is a fact.
However, I do not believe that this means that "Faster Than Light" travel cannot be achieved. There are many possibilities for it; wormholes, spacefolding for 'realistic' options, and perhaps more exotic possibilities such as Heim Theory (a GUT involving extra dimensions, which allows a form of FTL, can't remember how right now, google it if you're interested). Just because we can't do it now, doesn't mean we won't be able to.
But the fact remains; physics as we currently understand it does not allow for massive bodies to be accelerated to the speed of light or beyond.
14. I look forward to thought powered anti-grav underpants

*places reserve order*
15. (Original post by GemmaLS)
<snip>
...No.

You might be getting confused by the fact the photons travel in a straight line, but they definitely do move through the spatial dimensions. If they didn't, you wouldn't be able to see anything at all! They'd be fixed at one point in space if they only moved through time...

(Original post by President_Ben)
I look forward to thought powered anti-grav underpants

*places reserve order*
*quickly starts patenting*
16. (Original post by Stikatoo)
nothing's impossible because there is an infinite amount of time for it to happen in. I went back and added the word 'near' because we don't know what can be achieved in the future.
Weak argument. In terms of physics, theories, and experiments, it is impossible. It's not like saying "if I play enough, I'll win the lottery" or "one day we'll send a man to jupiter".
17. (Original post by Duke Flipside)
...No.

You might be getting confused by the fact the photons travel in a straight line, but they definitely do move through the spatial dimensions. If they didn't, you wouldn't be able to see anything at all! They'd be fixed at one point in space if they only moved through time...
Ah, thanks - got it the wrong way round - light only moves through space and not through time - that's why it doesn't degrade/fade - it doesn't get 'older'. It moves in a straight line through one space dimension at 'light speed'. Everything else moves through 'spacetime'.

Now my brain hurts!
18. Just to add a little something to a debate that seems to be getting very tired indeed, there's a growing body of research and mathematics to suggest that gravitons travel considerably faster than light. Unfortunately, the theory is somewhat beyond me at the moment so you would have to Google it if you want any clarification.
19. Woah this is getting seriously hardcore for GD.. it should come with a warning for all those poor artists that faint at the very mention of an equation
20. Pineapolis, I can't say that I've heard anything like what you're suggesting, and I think the generally-accepted theory is that they travel at c...still, just because I haven't seen it doesn't mean you haven't. D'you have any links? *is an astrophysics geek, as you may've guessed...*

Also, light does move through time...hence the reason we see the sun as it was eight minutes ago; if it didn't move through time it would have an infinite velocity, rather than a high-but-finite velocity.

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