How do physicists know that the speed of light is the fastest any object can go?

Question

Though I dont expect an educated answer I feel I must clarify. I am asking how they could know that the speed of light is the fastest velocity attainable without actually reaching the speed of light. is it noot probable that the fastest attainable speed may be slightly above the speed of light?

Answer 1

it is all theory...they don't know it for sure...and would anyone be able to detect something moving faster than the speed of light is doubtful, no body really knows much of anything for certain...

Answer 2

Simply stated and with a minimum of mathematics:

Newton's formula for energy is E=1/2MV^2.
We know this is not valid because if we substitute zero for the Velocity, the energy of the mass becomes zero.

Einstein found that the total energy contained in a moving body was actually E=MC^2/sqrt1-(V^2/C^2). Einstein's formulas have stood the test of time and advanced technology testing for over 100 years. There's no valid reason to believe that, even though we have not experienced any matter at the speed of light, that this formula will not hold true for all speeds.

As you can see from the formula, if V^2 equals C^2 (ie the object reaches the speed of light) the denominator becomes the sqrt of 1-1 or, you guessed it, zero. If the object exceeds the speed of light, the denominator becomes the square root of a negative number. Both of these functions are undefined - division by zero -perhaps infinite energy to achieve the speed of light, but God only knows what the square root of a negative number would indicate.

And that's it in a nutshell.

Answer 3

It is an outcome of Special Relativity (it has nothing to do with the field equations, which are from General Relativity).

SR is very well expermientally verified.

The thing with a theory like SR is that it is built on a couple of axioms (that movement of reference frames is relative and that everyone get the same result for the speed of light - and that it), then the rest is pure logic.

A logical outcome given these axioms from SR is that the mass of a particle as measured in a gven reference frame increases as the particles speed increases in that frame. This increase is asymptotic - and at the speed of light it is infinite.

So SR says that it would take an infinite amount of energy to accelerate any particle that has any mass to the speed of light.

What has also become clear is that all of the particles in the universe with zero rest mass travel at the speed of light and obey similar rules - so the speed of light should really be called the speed of zero rest mass particles. It is not possible to change the speed of such particles in vacuum.

The only possibility for a particle to exceed the speed of light is that it had always - since the beginning of the universe - been travlling faster than light. It would then not need to be accelerated. Such hypothetical particles are called tachyons, and have never been found. They would be curious if found because their energy would actuall decrease as you accelerated them.

Answer 4

First of all, physics say that the maximum speed for an object with a nonzero restmass is the speed of light. It does not saying about particles with restmass of zero. But as far as we know photons (particles of light) are the particles with zero restmass, and it makes sense for them to travel at the speed of light. There could be other particles not yet discovered that have a nonzero rest mass and travel faster than the speed of light.

Second in accelerators, like Fermi lab, constantly accelerate particles up to speeds ~.9999c but never has anyone detected a particle with a speed of 1.000000000000001c or greater. So We are pretty confident that c is the natural speed limit.

Answer 5

The speed of light is independent of the speed of the observer’s speed.

This has been established well by many experiments and from astronomical measurements of the motion of stars.

A deep analysis will reveal that by going with a speed more than the speed of light and measuring the speed of light as the same can happen only when the length, mass and time measurements become imaginary quantities.

Hence in an imaginary universe consisting of imaginary length, mass and time, an imaginary object can go with a speed more than the speed of light.

Answer 6

As you get faster, various things happen such as time slowing down and mass increasing. They know how much this happens by from theory, and experiments show that the theory is right for any speeds that they can achieve near the earth. The theory also predicts that at the speed of light, your mass becomes infinite and time stands still, so you won't be able to go any faster.

So it is a prediction based on a theory which produces measurable results, and experiments show that the theory appears to be correct,

Answer 7

Einstein developed the theory that no material object can move at the speed of light. Solutions to his field equations show that for such an object to move at the speed of light would require infinite energy and that the object would obtain infinite mass. Clearly both conditions are impossible.

It's true that no one has ever observed any object at the speed of light, however the phenomenon of mass increasing as the speed of light is approached has been directly observed countless times in high-energy particle accelerators.

Answer 8

Let's look at a typical equation involving the speed of light.

But let's look at it this way:

Let's say you have the kinetic energy of a baseball. Ldet's start with something we know.......the pitching speed. Let's say the speed of a pitch is 100 mph.........mmmkaaay?

EK = T = ½mv²

So v = 100 mph = 44.7 m/s

The mass of a typical baseball is about 145 grams.....0.145 kg

This gives 144.86 Joules of energy. Ok...so how much is this.

It's well documented that a ton of TNT gives an energy of about 4.2 x 10^9 Joules.

This is 28993511 times the energy in a that baseball.......even if it was hit by that vanity-fool-steroid-freak Barry Bonds.

What does this do for us? Well....by EXPERIMENT (for the TNT) it gives us a reference to guage by, not that we *need* it, but you are asking.......for verification.

Let's use this as a trial reference for energy and see how fast the baseball has to travel to give us this much energy of motion (kinetic energy).

v = √(2T/m)

==> v = √(2T/m)

m = 0.145 kg
T = 4.2 x 10^9 Joules

==> v = 170192.59 m/s

This is: 223.7 mph.

A typical speed for a ball hit by a bat is roughly 160 mph (http://webusers.npl.uiuc.edu/~a-nathan/pob/AJP-Nov2000.pdf)

Mind you...this if only for an energy of TNT. The energy of this ball moving at the speed of light is:

T = ½mv²

==> ½*0.145*c²
==> ½*0.145*3.8² [leaving off units for clarity]
==> 6525000000000000 Joules

-or-

6.525 x 10^15 Joules

This is
6.525 x 10^15 Joules/4.2 x 10^9 Joules = 1.6 x 10^6

In other words....the energy of this baseball moving at the velocity of light is 1.5 MILLION times greatwer than if the baseball had the energy of one ton of TNT.....which is also quite unlikely I think.

I realize that this is a very, very crude way to illustrate this, but we physicists don't tritely toss these things out without them being fully characterized and documented and tested. Benchmarks make a difference to us as it does to computer hounds trying to eek out 10 more frames/sec for HL2.

It's extremely unlikely that a baseball, or anything else for that matter will, or can ever reach the speed of light. It's been very well documented and studied thru the years. In both grandiose and cavalier ways....unless Barry Bonds (Markie M., etc) ups the doseage and demands color tv on the field too.

Answer 9

The first guy got it exactly right