Is the speed of light in a vacuum just considered to be a constant?

Question

(c) the speed of light in a vacuum is defined as ~186,000 miles per second. Has anyone try to question why? Why isn't it perhaps 100,000,000 miles per second( or some other number)? Nature just chose that speed? Does the Maxwell equation imply this or is it derived from this? Has anyone worked to think *outside of the box* and have a thoery of maybe an undiscovered force effecting it or something impeding it? Thank you if anyone knows!

Answer 1

The speed of light is that number simply by measurement. The number itself has no real natural meaning because we have arbitrarily defined both "miles" and "seconds". Besides, if it were any other number, such as 100,000,000mps as you suggested, then you would simply be asking why it was this and not 186,000mps.

If you mean to ask if there is a correlation between this speed and any other natural phenomenon or other measurement, then the answer is that none have yet been discovered. Unless, of course, you count the fact that any bit of matter accelerated to light speed approaches zero length and infinite mass. In that sense, everything in the universe is tied to it. ^.^ Several constants have been discovered that adhere to it, but their values would not answer your question, as it would be akin to asking, "Why is the ratio of a circle's circumference to its diameter exactly pi, and not some other number?" It is simply a physical constant.

If any other forces were able to affect or impede it, then it would not be constant. All known natural forces have no effect on light except for gravity, and all gravity can do is change its direction, never its magnitude. But then, this makes perfect sense when gravity is thought of as a curvature of spacetime instead of a force, in which case light still travels in a perfectly straight line but the topology of spacetime is changed to modify its apparent direction.

Answer 2

Maxwell theoretically predicted that the speed of E.M radiation in vacuum should be equal to the inverse of the square root of the product of the permittivity of free space and permeability of free space.

Permittivity of free space and permeability of free space are electric and magnetic properties of free space.

The theoretical value coincides with the experimental verification of the speed of light.

The two quantities being constants, the speed is constant in free space.

The Einstein’s special theory is the next step to this.

Even though it is a constant, for an observer moving toward a beam of light the speed of light should appear to increase and if we move away it should decrease.

But Einstein predicted that the speed will remain the same irrespective of the speed of the observer. And experimentally it is also verified.

That is the speed of light is absolute.

Answer 3

Take Maxwell's EM equations. Set del-dot E equal to 0 (no charge present). del-dot B always equals 0, as far as we know at the moment (see magnetic monopoles for opinions some people have).

Solve for the last two (del-cross E and del-cross B). You should get plane-wave equations that propagate at a constant velocity. That velocity happens to be c.

This velocity is dependent on the permitivity and permeability of free space, and as far as we know, those are also constant as well.

This solution was first done in the 19th century, and it bothered a lot of physicists at the time. All EM radiation propagates at a fixed velocity, no matter what frame of reference you're in.

This eventually triggered the Michelson-Morley experiments, which triggered Lorentz to come up with his equation, which then Einstein took and built some math infrastructure around and called in Relativity, later to be called Special Relativity.

Answer 4

Assuming there is nothing within the vacuum. But, perhaps the vacuum itself has an effect on it by slowing or accelerating, once travel through the vacuum is accomplished. Are Hawking's and Einstein's theories conflicting or are they curiously right on the money? Could be the illusive portal into time travel. Inquiring minds want to know!

Answer 5

It is constant because there is nothing in the vacuum to get in the way of the light. It's a vacuum.

Newton's First Law of Motion states:
An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Answer 6

there are theories that suggest that the speed of light (as well as other fundamental physical constants) may have been different in the past (i.e. billions of years ago typically) to what it is measured to be now, but at the moment the evidence for this is all a bit iffy.
for some further discussion of this check out wiki url below for example

Answer 7

Hello! Try to study Einstein Relativity Theory and you will understand how this speed was determined. It's a pretty complicated theory, but if you have the knowledge of Newtonian Physics and of course Maths I'm sure that you will be able to determine this speed too using the Impulse theory. If still you can't understand this, message me and I will write it for you.

Answer 8

There's no answer to "WHY" the speed of light is what it is. That it is 186,000 miles/second isn't a theory either -- the speed of light has been measured and re-measured countless times.

Answer 9

Yes, c can be derived from Maxwell's equations. Basically, it is what it is because it's a property of space.

c=1/sqrt(µ0*ε0), where µ0 is the permeability of free space and ε0 is the permittivity. These constants relate to the strength of magnetic and electric fields respectively.

Answer 10

the speed of light is actually not constant because of quantum unpredictability.