1

**New Theories / On the speed of light as invariant:**

« **on:**26/04/2017 20:58:47 »

Physicists have often been amazed at the invariance of the speed of light. This means that regardless of whether the source is moving or the destination is moving or even if both are moving, the speed of light remains constant at 3 x 10

Imagine then the surprise of scientists when they found that light does not obey these Galilean transformations. Take the following case. Suppose you have a light at a fixed source (A) shining towards a point (B) that is 100,000 Kms. away then we know that since the speed of light is 300,000 km/sec that it should take 0.33 secs for the light to travel from point A to Point B. And this is how long it does take. (note: Actually according to relativity this is by no means certain) Now suppose you fit the light onto a superfast train travelling at 150,000 km/s then surely it should take the light whose combined speed is 300,000 km/s + 150,000 km/s = 450,000 km/s and it should now take the light only 0.222 s to reach point B! Wrong! Say the scientists it would still take the light 0.33 secs to cover the distance from (A) to (B)!

How could this be true? More important how could it be proved to be either true or false? I was thinking about this problem when it occurred to me that the speed of sound (because it is a wave) is also invariant. Just like light the speed of sound is also independent of the speed of the source or of the destination or even if both were moving together. How could this be. I was thinking about something else when the answer came to me and it is ridiculously simple. Look at this problem. First you have a stationary sound at (A) travelling towards a point (b) which is 600 m distant. Consider that sound travels at 1257.12 kmh therefore it will take approximately 1.72 secs to cover the distance to (B). Now imagine that the sound (Siren or whatever) is fitted onto a car travelling at 150 kmh , then the sound should now take 600/ (150 kmh + 1257.12) = 1.53 sec to cover the distance to B, right ? Wrong say the physicists the sound will still take 1.72 sec to travel from point A to point B. How could this be ?

It becomes very simple to understand when we take into account that the speed of the car depends on its mass, the force with which it can press onto the tarmac, the speed with which the wheel revolves, the force of gravity etc., While the speed of sound is solely dependent on the properties of the medium it is travelling through. The two velocities have nothing to do with each other. It is like comparing apples and oranges you can't do it! So the sound will still take 1.72 secs to travel from point (A) to point (B) while the car would take 14.35 secs to cover the distance from (A) to (B).

That's all there is to the invariance of the speed of light or of the speed of sound. Apples and oranges.

^{5}km/s approx. What is so unusual about this? Unusual ! It goes absolutely against every practical experience known to mankind! In the normal world things obey what are known as Galilean transformations. Thus take two fast cars 150 Kms apart and travelling towards each other. Car (a) going at 150 kmh and car(b) at 100 kmh. If they both start off at exactly the same time when will they meet ? It might surprise you at first to learn that the time at which they will meet is governed by their combined speed or 100 kmh + 150 kmh = 250 kmh. They will therefore meet after 36 minutes during which time car (a) would have covered 90 Km and car (b) would have covered 60 km. The same would apply if the cars were moving away from each other here, the speed of the two cars is again combined but this time they are moving away from each other, thus they are departing from each other at a relative speed of 100 km + 150 kmh = 250 kmh. If both cars are moving in the same direction then the speed of car (a) relative to the speed of car (b) would be the difference in speed 150 kmh - 100 kmh = 50 kmh. These cars are moving according to Galilean transformations.Imagine then the surprise of scientists when they found that light does not obey these Galilean transformations. Take the following case. Suppose you have a light at a fixed source (A) shining towards a point (B) that is 100,000 Kms. away then we know that since the speed of light is 300,000 km/sec that it should take 0.33 secs for the light to travel from point A to Point B. And this is how long it does take. (note: Actually according to relativity this is by no means certain) Now suppose you fit the light onto a superfast train travelling at 150,000 km/s then surely it should take the light whose combined speed is 300,000 km/s + 150,000 km/s = 450,000 km/s and it should now take the light only 0.222 s to reach point B! Wrong! Say the scientists it would still take the light 0.33 secs to cover the distance from (A) to (B)!

How could this be true? More important how could it be proved to be either true or false? I was thinking about this problem when it occurred to me that the speed of sound (because it is a wave) is also invariant. Just like light the speed of sound is also independent of the speed of the source or of the destination or even if both were moving together. How could this be. I was thinking about something else when the answer came to me and it is ridiculously simple. Look at this problem. First you have a stationary sound at (A) travelling towards a point (b) which is 600 m distant. Consider that sound travels at 1257.12 kmh therefore it will take approximately 1.72 secs to cover the distance to (B). Now imagine that the sound (Siren or whatever) is fitted onto a car travelling at 150 kmh , then the sound should now take 600/ (150 kmh + 1257.12) = 1.53 sec to cover the distance to B, right ? Wrong say the physicists the sound will still take 1.72 sec to travel from point A to point B. How could this be ?

It becomes very simple to understand when we take into account that the speed of the car depends on its mass, the force with which it can press onto the tarmac, the speed with which the wheel revolves, the force of gravity etc., While the speed of sound is solely dependent on the properties of the medium it is travelling through. The two velocities have nothing to do with each other. It is like comparing apples and oranges you can't do it! So the sound will still take 1.72 secs to travel from point (A) to point (B) while the car would take 14.35 secs to cover the distance from (A) to (B).

That's all there is to the invariance of the speed of light or of the speed of sound. Apples and oranges.

The following users thanked this post: GoC