What is the speed of a ray of laser (c) on a moving vehicle at the speed of 0.2c in the same direction? Will the vector sum of the speeds be 1.2c or still c?
The special relativity theory is not a proof of that c is the ultimate speed in a vacuum. It only indicates that any velocity is constrained by the basic postulate where c is the ultimate speed in the universe as revealed in the formula u = (u’ + v) / (1 + u’v /c^2). However, when c is replaced by w = nc where n >= 1, the formula may still fits mathematically. Therefore, the special relativity theory didn’t rule out that there is no speed in the universe where u’ = v = w, observed or not yet, that would exceed c according to u = (u’ + v) / (1 + u’v /w^2)..
The simple vector some will not work with these speed limits. One has to take the relativity in to account. For an observer on the same vehicle the speed of light will be c . For an observer on the ground the speed of the light will be calculated by
(u+v)/1+u*v/c^2
Where u is the velocity of the object observed in the moving frame (vehicle) and v is the velocity at which the vehicle is moving with respect to ground frame. Now for this case u=c and v=0.2c. so if we put these values in this equation you will get velocity of light c for each observer.
The rate of change in the distance between two objects in a frame of reference with respect to which both are moving (their closing speed) may have a value in excess of c. However, this does not represent the speed of any single object as measured in a single inertial frame.
Source : Wikipedia
So the answer is yes it's possible to have 1.2c but this does not represent the speed of the traveling waves.
My question is related but a bit different
https://www.researchgate.net/post/What_is_the_limit_c_or_the_speed_of_light_in_vacuum
The answer to your question is yes. In vacuum no meaningful disturbance (material object or information carrying wave) travels faster than light. A simple vector sum will not work. This is because the vehicle moves with a velocity 0.2c with respect to the road (which can be thought of as a medium), light does not need a medium to propagate. Since there is no common frame of reference (or medium), a simple vector sum will not be appropriate.
If you can perform this experiment, you will be surprised (or not ?) that the measurement of the speed of a light pulse emitted from a moving vehicle and measured using a fixed device (i.e. time of flight measurement) does not depend on the vehicule speed. It will give you c +/- the measurement uncertainty...
Christophe
My answer may be stupid but mind speed exceed C. ...Can travel to other universe and come back within a second....
The special relativity didn’t prove that c is the ultimate speed because c is a given assumption in the relative velocity formula u = (u’ + v) / (1 + u’v /c^2) . In other words, it only indicates that if there were an ultimate speed such as c, any movement is constrained by c according to the special relativity theory. However, assume that a super velocity w = u’ = v’= 2c exists, the formula of special relativity theory still fits, i.e.: u = (u’ + v) / (1 + u’v /w^2) = (w’ + w) / (1 + w^2 / w^2) = w = 2c.
@Nanda: Your idea is very interesting. I shared similar perception as yours (see http://www.researchgate.net/publication/266559175_On_Cognitive_Informatics?ev=prf_pub).
The natural world where we live is a dual that compasses both the physical and abstract facets. The latter is our cognitive models of the physical world in the brain. We are able to cross the internal universe in the abstract world within less a second between any pair of arbitrary points apart by almost infinite distance. This indicates that the perception speed in the brain may be much faster than that of light for several orders of magnitude.
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