Laymen's Terms, please

[Warped9]

Something I worked up for myself some time ago. What the chart shows is the actual realtime travel time (as it would be perceived from Earth) and the relative transit time (as it would be perceived by anyone aboard the ship).

10% light = about .5% time dilation.
20% light = about 2% time dilation.
30% light = about 5% time dilation.
40% light = about 9% time dilation.
50% light = about 14% time dilation.
60% light = about 20% time dilation.
70% light = about 29% time dilation.
80% light = about 40% time dilation.
90% light = about 57% time dilation.
99% light = about 86% time dilation.
99.9% light = about 96% time dilation.
99.99% light = about 98.5% time dilation.

 

[Corwwyn]

The rules don't say that nothing is faster. There are hypothetical particles which move faster than light. The rules just say that nothing moving slower than light can be accelerated up to or beyond light speed.

Actually not quite. Nothing that has mass can be accelerated up to light speed.

I personally can't wrap my head around Relativity, especially the part where time slows down and our mass changes as we approach light speed. I just don't get it

Here's a super-simplified explanation which some of the physicists here probably won't like. If you're moving and look at an object, it will appear to be moving at a certain speed relative to you-- "a" miles per hour. If you move at a different speed and look at the same object, it will now appear to be moving at "b" miles per hour. Your relative speeds will change.

Light isn't like that. With respect to you, it will always appear to be moving at the same speed-- "c" miles per hour, no matter how fast you move. So it isn't relative-- it's fixed. And the only way that can be is if the elements that define speed ("miles" and "hours") become relative instead. "Hours", at least, get stretched or compressed accordingly.

Maybe a simpler (if imperfect) analogy might be: Imagine you're driving along a freeway at 100kmh...and your car is a brick (no streamlined supercar, just raw motor hotrod). Think how much fuel you use. Now imagine you're running at 200kmh, then at 300kmh. How many gallons to the mile would that be? What about 400kmh or 500kmh? Now you're getting to the stage of having a jet engine or rocket attached to your car to give you enough oomph to get to those speeds. How much fuel are you burning now? How hard is getting to push that brick even faster?

What would say are the odds of getting a car up to a million kmh on the freeway?

 

[Silvercrest]

Actually not quite. Nothing that has mass can be accelerated up to light speed.

Those are implied to be the same thing. As far as I know, anything that doesn't have mass must already be moving at light speed. (Although perhaps I should have spelled that out more clearly instead of implying it.)

As for the rest of your post, I don't know if you realize it, but we're trying to explain two different things. I was talking about time dilation as opposed to the original subject of why it's so impossible to get up to light speed.

 

[Trekker4747]

Since everything has mass then it's pretty fair to say that "nothing" can travel faster than light. Even electrons have mass so even electrons cannot travel at the speed of light. I do believe, however, certain high-frequency forms of radiation have no mass and they can travel FTL.

But FTL is sort-of the "halfway point." Nothing with mass can travel at C or faster. Light has no mass and cannot travel slower than C. Hyper-luminal particles (theoretical) travel at a speed faster than light and cannot travel slower than light.

 

[Robert Maxwell]

Since everything has mass then it's pretty fair to say that "nothing" can travel faster than light. Even electrons have mass so even electrons cannot travel at the speed of light. I do believe, however, certain high-frequency forms of radiation have no mass and they can travel FTL.

But FTL is sort-of the "halfway point." Nothing with mass can travel at C or faster. Light has no mass and cannot travel slower than C. Hyper-luminal particles (theoretical) travel at a speed faster than light and cannot travel slower than light.

Light can travel slower than c if it's passing through a medium (such as water or glass.) The speed of light is only constant in a vacuum. Other than that, you are basically correct.

The only way FTL "works" is if we can get around the limitations of physics. If we can find a way to counteract the increase in mass, for instance, that goes along with acceleration--this would basically be anti-gravity. Or, if we could fold space, in which case there's no acceleration involved at all, no increase in mass, and thus no violation of physics. But we have no idea how to do that, obviously. I would assume it's so energy intensive as to be extremely prohibitive, though, even if we could make it work.

 

[Trekker4747]

Light can travel slower than c if it's passing through a medium (such as water or glass.) The speed of light is only constant in a vacuum. Other than that, you are basically correct.

But it's not traveling slower than c is it? C is a constant through the same medium. If it changes mediums its speed will change but that change will still go be a constant speed.

 

[T'Girl]

But it's not traveling slower than c is it?

That exactly what it's doing.

The letter C (for Celeritas) specifically refers to the speed of light in vacuum. In a medium light does not propagate at a speed equal to C, so you would not use the symbol "C."

In transparent materials, the refractive index generally is greater than 1, meaning that the phase velocity of light is less than C. Air's refractive index is 1.0003, and water's is 1.33.

The speed through a medium is C divide by the refractive index of the material, so 299,792,458 (C) divide by 1.33 (water) is 225,308,152.79 meters per second through water.

In fact, there was recently a confirmation that your head is older than your feet thanks to time dilation.

That would depend on how much of your life you spend on your back with your feet up in the air.

.

 

[Corwwyn]

Of course light also slows down as it passes very near a very great mass.

 

[T'Girl]

^^ I wonder if gravity could be considered a medium?

 

[Robert Maxwell]

Gravity does not slow down light, though it does curve its path. Gravity is also not a medium, it's a force.

 

[Silvercrest]

^^ I wonder if gravity could be considered a medium?

Nope, nor is it particularly rare. I think the only category for it is "well-done."

 

[CuttingEdge100]

Because matter is a form of energy, and the maximum velocity energy can move at is the speed of light. You'd either turn into energy, which would kill you; or you'd turn into a black-hole.

As you get closer to light-speed your mass increases, which also tends to distort the fabric of space, and this distortion actually causes a time-dilation. The speed of light always appears to be moving the same to the observer moving at the speed of light. So as I get closer to the speed of light, it appears to be moving just as fast. For that to happen, time has to slow down to the observer.

 

[kkozoriz1]

But it's not traveling slower than c is it?

That exactly what it's doing.

The letter C (for Celeritas) specifically refers to the speed of light in vacuum. In a medium light does not propagate at a speed equal to C, so you would not use the symbol "C."

In transparent materials, the refractive index generally is greater than 1, meaning that the phase velocity of light is less than C. Air's refractive index is 1.0003, and water's is 1.33.

The speed through a medium is C divide by the refractive index of the material, so 299,792,458 (C) divide by 1.33 (water) is 225,308,152.79 meters per second through water.


.

Which brings us to Cherenkov Radiation which is when a particle travels faster than light through a medium, for example water. This is the blue glow from the core of a nuclear reactor.

http://en.wikipedia.org/wiki/Cherenkov_radiation

Think of it as a Photic Boom. Perhaps this is wwhat causes the flash when a ship enters or leaves warp.

 

[T'Girl]

Perhaps this is wwhat causes the flash when a ship enters or leaves warp

I think that's the universe screaming rape.