Laymen's Terms, please

[iguana_tonante]

Sure, I may be a dumb kid (I'm sure as hell not a scientist, like I'm sure some people here are), but can anyone explain exactly why we can't go faster than light in simple terms? Because I've always heard people say "Oh, it's impossible", "It will never happen in a trillion billion million years" so on and so forth, and I've never really understood why it would be so impossible. Once again, I'm no scientist, so forgive me if I'm a bit ignorant, but it seems to me just a simple problem of:

A. Generating enough speed to get going faster than light, and
B. Finding a way to navigate safely at such a high speed.

So, can anyone explain why such a thing would be so impossible? Not generating any sort of field or going through wormholes, just plain accelerating until you reach faster-than-light speeds.

Lots of people came out with good explanations, so I hope it helped you with this difficult subject. As for me, I've been working in a relativistic frame of reference in my job for so long that I'm not sure I could conjure an explanation that would not involve a generous helping of maths.

Here's my two c: if you could travel faster than light in a vacuum, you would see your own buttocks while running. Think twice before trying to do it.

 

[Robert Maxwell]

Personally, I think the more difficult concept to understand is that gravity is an acceleration effect caused by the curvature of spacetime, which is caused by mass. As if the very act of having physical substance makes a "dent" in the fabric of reality that bends other objects around it. Weird.

 

[SPCTRE]

Here's my two c:

Oh. Oh! I c what you did there

 

[Silvercrest]

Here's my two c: if you could travel faster than light in a vacuum, you would see your own buttocks while running. Think twice before trying to do it.

No wonder there's a law against it!

 

[Rett Mikhal]

Here's my two c:

Oh. Oh! I c what you did there.

Groan worthy, guys. Groan worthy.

 

[Trekker4747]

I see it as pretty simple why we can't move faster than light. Because light itself can't travel faster than light (through the same medium, that is.)

As someone up thread pointed out no matter if light is moving from a stationary object or a moving object the light travels at the same speed (rather than adding its speed to the moving object.)

So a stationary person shoots a laser-pointer at a wall at the same time as someone shoots a laser pointer at the wall from a moving object (at the same time from the same position as the first peson.) Both beams of light hit the wall at the same time, the second light doesn't hit sooner because c is added to the speed of the moving object.

It's even for this reason that we won't be able to travel even at the speed of light. We can get very, very, verrrrrrrry close but we'll never get there all the way. Why?

Consider this. Say you've got a space ship moving at c through space. Someone gets up, run towards the front of the ship. That person is now moving faster than light! Which can't happen. Thus, traveling at c is impossible for any object that isn't light.

But to boil it down even far simpler than that on why nothing can travel faster than light:

Because if it could, then light would be the one doing it. Light is pure, raw, energy. It has no mass. Non whatsoever. It's all energy. Even an electron has some mass and travels slower than light. So if something with no mass and no restrictions to it when it moves other than the medium it is traveling through (density of the material. Light travels slower through air than it does a vacuum) then light would be the one to do it because it is almost completely unencumbered from moving.

 

[STR]

Light always moves at the same velocity in a vacuum. That's the important part. Passing through any kind of medium will slow light down. It's the speed of light in a vacuum that is the absolute speed limit of the universe.

Very true. In fact, in water, some particles are able to travel faster than the light going through the water. The result is a wave of light not dissimilar in nature to a sonic boom. It's called Cerenkov radiation and is a common sight in water cooled nuclear reactors, and retention pools that temporarily house nuclear waste when its most radioactive (right after it's pulled from the reactor core).

The EM emssion is mostly in the UV range, but there's enough in the visible range to see it as a blue glow.

 

[RoJoHen]

Here it is in Laymen's terms.

Light always moves at the same speed. Always.

When you are standing still, it is going the normal speed.

When you are going mach 20, it is going the normal speed.

When you are going 1/2 of its speed, it is going the normal speed.

When you are going .9999999999 of its speed, it is going the normal speed.

Since the space part doesn't change, time has to change. Two people moving at different speeds will see light going the same speed because time slows down as you approach the speed of light. It's scientific fact.

So to go .99999999 of the speed of light would dilate time to the point an hour's worth of travel would be millions of years to everyone going no where close to that speed. Plus, it would take you thousands of years to get to another star system at that speed, regardless, so trillions of years would have passed and then at that point, the entire universe has ended.

Beyond lightspeed... has yet to be seen in terms of time dilation.

Here's a nifty video that explains it!

http://www.youtube.com/watch?v=V7vpw4AH8QQ

I guess this is one of those things I'm just going to have to accept without really understanding. I know what the facts are, but I have a really hard time visualizing Time as anything but a constant. How fast do you have to be going before the effects of time dilation become measurable?

 

[SPCTRE]

Here's my two c:

Oh. Oh! I c what you did there.

Groan worthy, guys. Groan worthy.

Blame iguana, he started it!

 

[FordSVT]

Here it is in Laymen's terms.

Light always moves at the same speed. Always.

When you are standing still, it is going the normal speed.

When you are going mach 20, it is going the normal speed.

When you are going 1/2 of its speed, it is going the normal speed.

When you are going .9999999999 of its speed, it is going the normal speed.

Since the space part doesn't change, time has to change. Two people moving at different speeds will see light going the same speed because time slows down as you approach the speed of light. It's scientific fact.

So to go .99999999 of the speed of light would dilate time to the point an hour's worth of travel would be millions of years to everyone going no where close to that speed. Plus, it would take you thousands of years to get to another star system at that speed, regardless, so trillions of years would have passed and then at that point, the entire universe has ended.

Beyond lightspeed... has yet to be seen in terms of time dilation.

Here's a nifty video that explains it!

http://www.youtube.com/watch?v=V7vpw4AH8QQ

I guess this is one of those things I'm just going to have to accept without really understanding. I know what the facts are, but I have a really hard time visualizing Time as anything but a constant. How fast do you have to be going before the effects of time dilation become measurable?

Measurable? Someone correct me if I'm wrong, but we've measured the effects of time dilation due to relative velocities (on planes and satellites) and the influence of earth's own gravity well (on top of a mountain versus at sea level) using atomic clocks. We've got pretty sensitive clocks that measure extremely small fractions of time.

Now, to be appreciated by a human on his return to earth after space journey, you've got to reach a significant portion of the speed of light, I think far greater than 1/2 C. Even then he wouldn't be coming back with months or years difference, he'd be just a few days out of step after months or years of travel. You've got to really get up close to light speed before you start to notice really significant change. As with the amount of energy required to travel at light speed, the amount of time dilation you suffer increases dramatically as you move towards C.

 

[Robert Maxwell]

In fact, there was recently a confirmation that your head is older than your feet thanks to time dilation. It's only older by a few tiny fractions of a second by the end of your life, but it's still measurable.

 

[Deckerd]

Travelling at one half c would seriously mess up the traveller's relative time. If the time difference can be measured in people travelling in aeroplanes relative to people on the surface, then it stands to reason that even a fraction of c would cause a significant difference.

 

[Robert Maxwell]

And just to bend your mind a little more: gravity and acceleration are the same thing, from a physics point of view, so intense gravity dilates time just as much as high acceleration.

 

[sojourner]

Travelling at one half c would seriously mess up the traveller's relative time. If the time difference can be measured in people travelling in aeroplanes relative to people on the surface, then it stands to reason that even a fraction of c would cause a significant difference.

This is only true if the time change is linear, say 1/2c leads to 1/2 time, which it doesn't. As has been said, you have to get much closer to c before you start having big differences.

 

[RoJoHen]

Measurable? Someone correct me if I'm wrong, but we've measured the effects of time dilation due to relative velocities (on planes and satellites) and the influence of earth's own gravity well (on top of a mountain versus at sea level) using atomic clocks. We've got pretty sensitive clocks that measure extremely small fractions of time.

Now, to be appreciated by a human on his return to earth after space journey, you've got to reach a significant portion of the speed of light, I think far greater than 1/2 C. Even then he wouldn't be coming back with months or years difference, he'd be just a few days out of step after months or years of travel. You've got to really get up close to light speed before you start to notice really significant change. As with the amount of energy required to travel at light speed, the amount of time dilation you suffer increases dramatically as you move towards C.

Okay, measurable was the wrong word. I therefore appreciate your second paragraph.

 

[Deckerd]

Travelling at one half c would seriously mess up the traveller's relative time. If the time difference can be measured in people travelling in aeroplanes relative to people on the surface, then it stands to reason that even a fraction of c would cause a significant difference.

This is only true if the time change is linear, say 1/2c leads to 1/2 time, which it doesn't. As has been said, you have to get much closer to c before you start having big differences.

Depends how you quantify a big difference.

 

[YellowSubmarine]

Consider this. Say you've got a space ship moving at c through space. Someone gets up, run towards the front of the ship. That person is now moving faster than light! Which can't happen. Thus, traveling at c is impossible for any object that isn't light.

Actually, that's not a problem. The time in the space ship would have stopped, so no-one would be able to run anywhere, forward or backward. The bigger problem is that not only the space ship or anything in it can't accelerate, it also can't decelerate. It is essentially an unstoppable moving object with infinite mass, infinite momentum and thus infinite kinetic energy that can cut through anything.

 

[sojourner]

Depends how you quantify a big difference.

A few days?

 

[Warped9]

I'd have to check, but at .5c the dilation effect would be something like 15% I think.

You'd have to get around .9c to really see big changes.

 

[Trekker4747]

Lorentz Factor Forumla

1/sqrt(1- (velocity (in km/s)squared/c-squared.))

So for .5c (abt 150,000 km/s) It'd be 1/sqrt(1 - 150,000^2/300,000^2)

The answer would be how many seconds passes for the observer on Earth for every second that passes for the person the space craft.

.5c would, indeed, be somewhere around 15%.

IIRC