Speed of light - why is it a speed limit?

[r00tcause]

Originally posted by: f95toli
I think that what r00tcause meant was that science can never give an answer to WHY nature behaves in a certain way, it can just tell us HOW it behaves. The reason why we believe SR is correct is because it correctly predicts the outcome of every experiment we have tried so far, not because SR is "natural" or "makes sense" or anything like that.
Most of modern physics is so counter-intuitive that we can never truly understand it, thw world it describes is too different from our low-speed macroscopic world.

Well, never say never. I was merely stating that currently, we dont have an explanation as to WHY mass increases to infinity as we approach light speed. On earth, its simple to explain why an aircraft lengthens at high speeds, atmospheric resistance. However, light speed appears to caused by some kind of cosmic resistance, maybe all this 'dark matter" is exerting frictional forces.

 

[r00tcause]

Originally posted by: aplefka
I've got a question somewhat related to this. If you travelled, let's say, one lightyear, is there any way to measure how much time would have passed on earth? Because if time works differently at the speed of light, one year travelling at that speed would be different than just 365 days would it not?

1 year would pass on earth if I traveled 1 light year...

The key is that to YOU it would seem like no time passed at all.

So, if you travel at near light speed for say, 10,000 years, you might age (depending on speed) say 10 years. When you stop, it will seem like 10 years passed to you, but in reaility, you've been circling for 10,000 years.

Its a good way to travel into the future, but its a one way trip.

 

[gururu]

there is no 'speed limit'. velocity of light is simply a property of it, just as the wavelength and frequency is. There may be other forms of energy we haven't uncovered yet that exceed the velocity of light. As far as taking mass to the speed of light, it will never be done unless we can transform it to pure energy and then re-transform it to mass at a destination. The speed of light, if you will, is simply the maximum speed light can travel.

 

[Tweakin]

There are multiple speeds of light called Tacion...Hasn't anyone watched Star Trek or Kapax?

 

[f95toli]

AFAIK tachyons were just "anomalies" in some of the olded versions of string theory (15-20 years ago), from what I understand tachyons (as well as any other other FTL particle) are no longer possible in modern string theory (which probably should really be called "brane-theory).

 

[Anubis08]

This goes to special relativity. Here is a question to help you. If a satellite shoots past me at .99c and I shoot light after it what velocity id the light traveling in relation to the satellite (if you were on the satellite how fast would it appear to be going). It would appear to go approx. 300000000 m/s faster than you. That is how it was explained to me. There is no acceleration involved it is just that light travels only one speed in space. Although you are moving through space it would not be any different than if you were sitting still.

 

[Anubis08]

Here is another accepted postulate:
If two spaceships (A & B) are moving directly towards eachother and an observer on earth sees A going .75 c and B .85c, how fast does A see B approaching. .980 c. Although on earth you see both moving with speeds that would add up to more than c, that is not what they're actually doing. It also related to the pole-barn paradox: Read previous threads.

 

[JonB]

but, Anubis08, the light reaching your .99c satellite would red-shift dramatically

 

[kotss]

Originally posted by: r00tcause

Originally posted by: f95toli
I think that what r00tcause meant was that science can never give an answer to WHY nature behaves in a certain way, it can just tell us HOW it behaves. The reason why we believe SR is correct is because it correctly predicts the outcome of every experiment we have tried so far, not because SR is "natural" or "makes sense" or anything like that.
Most of modern physics is so counter-intuitive that we can never truly understand it, thw world it describes is too different from our low-speed macroscopic world.

Well, never say never. I was merely stating that currently, we dont have an explanation as to WHY mass increases to infinity as we approach light speed. On earth, its simple to explain why an aircraft lengthens at high speeds, atmospheric resistance. However, light speed appears to caused by some kind of cosmic resistance, maybe all this 'dark matter" is exerting frictional forces.

The reason that mass increases is because as you gain velocity your kinetic energy increases.
As most everybody should know by now E=MC^2. Mass and energy are interchangeable.
As you gain kinetic energy your overall mass/energy level is increasing. As you get closer to the
speed of light your kinetic energy has increased by great orders of magnitude. If you used simply
KE=(0.5)M(V^2) and substituted C for V you would have a finite energy if you only used the rest mass.
But as you have gained velocity you have gained energy which is mass. Therefore you would have to
calculate the effective mass at just before light speed to calculate you current kinetic energy.
The relativistic mass is calculated using the Lorentz transform for mass. (Has already been stated.)
At just before the speed of light for an object that has mass at rest, the mass has increased to a near
infinite level. Just enlightening on the mass issue, not answering why it is the utlimate speed limit.

 

[Anubis08]

Using that theory, wouldn't Electromagentic radiation with higher energy like x ray or gamma radiation be more succestible to gravity. Doors swing two ways. Higher velocity + hgiher energy, if speed cannot change for light higher energy should be equivalent to higher mass. Even though technically a photon has no mass, but then how is it bent by gravity. Goes back to general relativity.

 

[kotss]

Originally posted by: Anubis08
Using that theory, wouldn't Electromagentic radiation with higher energy like x ray or gamma radiation be more succestible to gravity. Doors swing two ways. Higher velocity + hgiher energy, if speed cannot change for light higher energy should be equivalent to higher mass. Even though technically a photon has no mass, but then how is it bent by gravity. Goes back to general relativity.

Well actually all EM Radiation is travelling at the speed of light (in the medium its travelling in). The only
thing that differs is the frequency and wavelength. Higher frequency denotes a more energetic wave.
And energy of the photons comprising the EM radiation is derived from Plancks Constant (h) times the
frequency of the wave. And yes Virginia a photon does not have mass, but you can give it a mass-energy
equivalent by using E=m*c*c . Which could be solved by deriving the following:
v=Wavelength
f=frequency
h=Plancks Constant
c=speed of light
m=mass
E=energy

c=fv
E=hf
E=mcc
mcc=hf
f=c/v
mcc=c/v
mc=1/v
so in finality
m=1/v*c
so the Mass equivalent for a photon is derived from dividing 1 by the product of the wavelength and
the speed of light.

Regardless of wether it is mass or energy, all light is affected by gravity, just how much is it affected
is another matter. I do not know the answer to that one, but I will endeavor to find out. Hope this physics
lesson helps someone.