Question Regarding Faster-than-light (also superluminal or FTL)

According to Einstein's theory of special relativity, published in 1905, nothing can exceed the speed of light. That speed, explained Einstein, is a fundamental constant of nature: It appears the same to all observers anywhere in space.

I have been trying to understand why traveling the speed of light is not possible and for the life of me, I can't wrap my head around why it is not possible. Could someone with knowledge regarding this "dumb it down" for me?

I have read tons of stuff on this topic but unfortunately it is WAY over my head and frustrating in that I cannot understand it.

Its because we are living in a game.......like all computers it has its limits....the limits of this game is lightspeed

Who knows?? Its all speculation at the moment

reply to post by BLKMJK


Nothing with physical mass can exceed the speed of light.

EDIT: The reason is because the faster you go, the more energy you need to accelerate the mass of the craft. It eventually reaches a critical point where the energy required becomes infinite. Which is the speed of light. If you were to hit that speed in a craft, it's theorized you would start going back in time, but it's also theoretically impossible to reach that speed (due to energy requirements). That's what I remember anyway.

reply to post by BLKMJK


Einstein explained it well in his works ... and the quote you used. It's all relative ... to the OBSERVER

from what i understand, an object, according to einstein, increases to infinite mass the closer to the speed of light it gets, and the energy needed to move it also increases to infinite.

so basically it counteracts each other like to infinite opposing forces.

but what i don't understand that on object is weightless in space, so infinite mass doesn't make a difference. but then he stated that you require a infinite amount of energy to move something to speed of light.

no fossil fuel can move an object at that speed.

einstein was human. in the future i'm sure his theories will be laughed at like we laugh at scientists who thought the earth was flat and sun revolved around it.

reply to post by randomname

but what i don't understand that on object is weightless in space, so infinite mass doesn't make a difference.

That's a really interesting point. I think once you have it at a certain speed, it will stay there, but to accelerate requires energy. Ehh...it's all so confusing. Who cares.

inertia is a big factor, and the speed of light 299 792 458 +1 i don't see a drama with it once we have inertia and gravity down while in space,

You're confusing weight and mass.

Mass is constant everywhere, in space or not.

Originally posted by BLKMJK
According to Einstein's theory of special relativity, published in 1905, nothing can exceed the speed of light. That speed, explained Einstein, is a fundamental constant of nature: It appears the same to all observers anywhere in space.

I have been trying to understand why traveling the speed of light is not possible and for the life of me, I can't wrap my head around why it is not possible. Could someone with knowledge regarding this "dumb it down" for me?

I have read tons of stuff on this topic but unfortunately it is WAY over my head and frustrating in that I cannot understand it.

Wheeler wrote a good book on it called "Spacetime Physics" which, while it is a textbook, is quite readable.

Special Relativity states that for objects with non-zero mass, that the relativistic mass will increase with acceleration, becoming infinite at the speed of light.

As the mass goes up, so does the momentum that needs to be overcome, to change its rate of motion.

So even the lightest subatomic particle will take infinite energy to accelerate to the speed of light.

The specific formula that shows this is a bit mathematical and I don't know if it will actually be of help to you if you aren't up to speed with that type of math.

If you had a spaceship that could travel at the speed of light and you turned on the headlamp to see where you are going, would the headlamp do anything? I believe that it would leave the spaceship at the speed of light since relatively speaking, the spaceship is standing still compared to the light beam leaving it. To an observer that was stationary to both events, the light beam leaving the spaceship would probably seem to travel twice as fast. What think you?

Originally posted by chr0naut

Originally posted by BLKMJK
According to Einstein's theory of special relativity, published in 1905, nothing can exceed the speed of light. That speed, explained Einstein, is a fundamental constant of nature: It appears the same to all observers anywhere in space.

I have been trying to understand why traveling the speed of light is not possible and for the life of me, I can't wrap my head around why it is not possible. Could someone with knowledge regarding this "dumb it down" for me?

I have read tons of stuff on this topic but unfortunately it is WAY over my head and frustrating in that I cannot understand it.

Wheeler wrote a good book on it called "Spacetime Physics" which, while it is a textbook, is quite readable.

Special Relativity states that for objects with non-zero mass, that the relativistic mass will increase with acceleration, becoming infinite at the speed of light.

As the mass goes up, so does the momentum that needs to be overcome, to change its rate of motion.

So even the lightest subatomic particle will take infinite energy to accelerate to the speed of light.

The specific formula that shows this is a bit mathematical and I don't know if it will actually be of help to you if you aren't up to speed with that type of math.

edit on 17/5/2011 by chr0naut because: (no reason given)

Don't photons have mass? If they became infinite at light speed, I sure wouldn't want a flashlight shone at me. All joking aside, how do photons travel so fast and emit light as they travel on their merry way?

Another thought: In the weightlessness of space (OK, microgravity) if a common two cell flashlight were swithched on, would the escape of photons propel the flashlight? Any? Maybe?

reply to post by BLKMJK


The best way to explain it is this: 'gravity' has an influence that expands at the speed of light. As you accelerate, you begin to 'ride' your own 'gravity wave' - which has the net effect of increasing your mass. To accelerate further - you must accelerate an object that behaves as though it gets more massive as it increases velocity. Since, at the speed of light, an object would simply be sitting atop a 'wave' of gravity with an ever-increasing amplitude, it would mean that achieving the speed of light through known methods of acceleration would require an infinite amount of energy.

Whether that's exactly how it works, or not - it does help to explain both the increase in mass and the time dilation experienced by high-velocity objects, and illustrate it in a more intuitive way.

Now - if you had an object that was already moving faster than the speed of light, somehow, things may function considerably differently. Or - it may be possible to accelerate faster than the speed of light if enough energy can be delivered to the object to allow it to overcome the 'bow-wave' of gravity (the problem, here, is that the 'wave' is sourced at the mass of the object - meaning every particle within the object, not just its surface) - this would likely produce an effect similar to Cerenkov Radiation.

Although it should also be noted that radiated electromagnetic fields from the object would also be compressed to the point of reaching Planck energy density limits - at such extremes, the IR-radiation of standard objects would easily be able to achieve wavelengths that challenge the Planck constants - which would lead to the formation of quantum singularities that rapidly decay into particle radiation - or some other craziness.

That being the case - such a reaction may 'sink' any excess energy that would be used to overcome the 'bow-wave' - effectively making all attempts to exceed the speed of light via known methods impossible.

Bear in mind - that is all speculation on my part.

reply to post by NightFlight


Yes Photons have mass, but only at the speed of light. Their rest mass is zero.

Same goes with some other speed of light particles.

Originally posted by randomname

but what i don't understand that on object is weightless in space, so infinite mass doesn't make a difference. but then he stated that you require a infinite amount of energy to move something to speed of light.

You're right, things are weightless in space, but they're not massless. Objects have the same mass regardless of where they are. It's this (mass) that increases with increasing velocity, not weight.

Originally posted by chr0naut
reply to post by NightFlight

 

Yes Photons have mass, but only at the speed of light. Their rest mass is zero.

Same goes with some other speed of light particles.

Specifically, there are two "speed of light" particles: photons and gluons. Both transmit a force, both have zero rest mass, and both travel at c.
The only other particle that comes close to having zero rest mass is the electron neutrino, which has an experimental upper limit on its mass of 2.2 eV (to compare, the electron has a mass of about 500 thousand eV).

Also, I want to point out that the mass a photon has is a direct result of it travelling at the speed of light. If you could bring a photon to a complete stop, it would be massless, but, due to the relativistic increase in energy/momentum with velocity, the photon gains a finite mass when it travels at c (which is always).

reply to post by BLKMJK


It is impossible for massive objects to travel faster than the speed of light because, as velocity increases, the mass of the object increases, and, as its mass increases, the force needed to accelerate it increases. By the time the speed of light is reached, the object's mass is infinite, therefore the amount of force needed to accelerate it to the speed of light is infinite. Infinite force is impossible, to the speed of light is impossible for a massive object to reach.

By the way, you're not the only one wondering this: Physics, anyone?

Since everyone already explained it with the textbook answer, I will dumb it down even more...

Light is really really small and supposedly weightless... so it can travel really fast.

Everything that is larger and heavier than light will never travel as fast as it, so that includes just about everything.

I also like to say that nothing can travel faster than light because everything is made of light. But that saying wont fully be understood for a few years.

Originally posted by CLPrime
reply to post by BLKMJK

 

It is impossible for massive objects to travel faster than the speed of light because, as velocity increases, the mass of the object increases, and, as its mass increases, the force needed to accelerate it increases. By the time the speed of light is reached, the object's mass is infinite, therefore the amount of force needed to accelerate it to the speed of light is infinite. Infinite force is impossible, to the speed of light is impossible for a massive object to reach.

By the way, you're not the only one wondering this: Physics, anyone?

edit on 17-5-2011 by CLPrime because: (no reason given)

This makes sense but I still do not understand WHY or HOW mass increases as the velocity increases. The more I think about it the more tangled up in my head I get.

Originally posted by gift0fpr0phecy
Since everyone already explained it with the textbook answer, I will dumb it down even more...

Light is really really small and supposedly weightless... so it can travel really fast.

Everything that is larger and heavier than light will never travel as fast as it, so that includes just about everything.

I also like to say that nothing can travel faster than light because everything is made of light. But that saying wont fully be understood for a few years.

edit on 17-5-2011 by gift0fpr0phecy because: (no reason given)

Thank you that makes sense. I do not understand what you mean by "everything is made of light". If that be the case than how can lighter be lighter than itself?

Originally posted by chr0naut
reply to post by NightFlight

 

Yes Photons have mass, but only at the speed of light. Their rest mass is zero.

Same goes with some other speed of light particles.

But why is this the case? Photons only have mass at the speed of light but their rest mass is zero? Great, my head will explode when I try to sleep thinking about this.