Why Matter Can't Travel Faster than Light

(First development : November 19^th, 1999 (in Spanish)
Last Update: September 7^th, 2003)

The thesis I will defend in this section is the following: "Any physical phenomenon in which changes take place, can suffer its changes with a maximum speed that depends on the conditions of the system". Starting from this thesis I will try to rationalize the meaning of " c " as maximum speed for material systems.

The normal situation is the existence of limits for speed in any motion. And these limits take sense when we understand the nature of the studied phenomenon. The “demonstration” will be by induction, based on well-known examples.

Let us begin with a simple example: Why the sound moves at around 300 m/s in the air? Leaving away the explanation and detailed equations, the simple explanation is that air molecules have a speed average, and the sound (which is not more than a coordinated movement of air molecules) cannot move quicker than the molecules that give him support.

Simultaneously, when the fundamentals are understood, right predictions can be done. In this way, if I want to transmit information by means of gas molecules motion and, I want to increase the transmission speed, I should use some mechanisms that increase the molecules velocity. To do so, I could change the gas (the lightest molecules move quicker at same temperature), I could change the system temperature, etc., etc. But, happen what happen, there will always be a limit for the information transmission speed through coordinated molecules motions. Imagine the opposite is an idealization without practical sustenance.

The automobiles also have limit speeds, fixed by the combustion speed, materials resistance, friction, etc., etc. And, if we do abstraction and, we eliminate any obstacle, then, we are supposing that real physical systems behave as an ideal one (instantaneous gasoline combustion, indestructible materials, null friction, etc.) And the experience shows that all real systems could only be compared with ideal systems in a range of appropriate values. The more we move away from ideal conditions, less ideal a real system is.

The same situation happens with any real system whose intrinsic nature we know. There is a limit (varying with conditions) for the maximum reachable speed. Doesn't matter that speed could be increased through different mechanisms. It is clear that there is a moment, when the reached speed cannot be overcome. It is necessary to clarify, although it is trivial, that the difference among a very big and infinite value, is the same one that exists between zero and infinite. No real number is nearest than infinite than the number zero. In a graphic way, if we try to fill a bottomless barrel, we will be so near achieving it overturning a pail or a million pails of water.

Then, 

why get our attention that a maximum speed exists for the motion of material objects? 

According with Special Relativity, this maximum speed (non reachable) for the displacement of material particles is the speed of light in vacuum. Special relativity does not demonstrate that no object can surpass speed " c ". Special relativity only postulates this limit once accepted that experimental data seem to point in such direction.

Many times I have listened opposition to the limit speed existence, as something going against logic. Why nobody considers the illogical of a limit speed for sounds transmission?

In fact, I believe that the appropriated question is the following: 

If physical world seems to indicate that maximum speed reached by material objects is 300.000 Km/s, which is the reason of the limit?

Considering this last question I believe that we will be advancing in the right direction to the phenomenon understanding . We will take a fact from reality and, instead of deny it (or simply accept it), wonder why it happens. Following this kind of outline, it was developed the Kinetic Theory of the Gases that not only explain the sound transmission but all gas transport phenomenon. Returning to the core of this development, if we accept " c " as limit for material systems motion speed, it is necessary wonder:

• Why is there a limit? 
• Is there an underlying structure, like molecules of gas impeding coordinated motions at bigger speeds than " c "?
• Could we alter that limit, in the same way as with the temperature in the case of sound?
• The speed of light in vacuum is a real or an apparent limit? This is a non-simple question, but I allow myself to introduce it, because it has importance in my own analysis of Special relativity.

The data of reality (experimental measuring) seem to indicate conclusively that " c " is a limit for material objects speeds. The most eloquent case is presented in the particles accelerators.  It is necessary to take into account relativistic mass changes in order to have these instruments working properly. Additionally, particles already accelerated behave like possessing greater mass than when being at rest.

In consequence, it seems a fully demonstrated fact that the mass of material systems (elementary particles in this case) grows indefinitely as the system speed comes closer to the value of " c ". And it fixes a limit for the system maximum speed. With mass growing to infinite it is impossible to continue the acceleration of the system. 

We can now summarize the exposed ideas. 

• It is the rule that maximum speeds exists for any physical phenomenon. 
• The maximum attainable velocity of material particles is "c".

And the question is straightforward: 

Why "c"?. 

Is it, or not,  an incredibly hard indication that the same phenomena that originate the speed of the electromagnetic waves also participates on the constitution of which we call "matter"?

Could a wave travel faster than their own molecules?

Of course not! But in this case we know that sea waves are the result of coordinated movement of countless water molecules. Then, the result is not surprising. 

We accept as "normal" that a projectile (or an airplane) could travel faster than the sound. The projectile can move in absence of air molecule. But, would be surprising a tornado (formed only by coordinated molecules of air motion) moving to supersonic speeds (it would be something like molecules of air traveling faster than molecules of air!!)

Main conclusions of this page:

• It is normal that all real physical systems have a limit for maximum speed motion. 

• The physical meaning of a limiting speed can only be understood when the system is known completely. 

• It is very suggestive that material systems have as limit speed, the speed of electromagnetic waves. Is there some deeper property that unifies both phenomenons?

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