What is the speed of light in a universe with altered physical constants?

[athenaroa]

we find ourselves in a new universe where the rules of relativity still are valid, but aplace in which physical constants may have new values. For instance, in this new universe, a 1 kg mass is now equivalent to 4x10^15 joules. In this new universe, at what approximate speed in M/sec will light travel in a vacuum?

 

[Doc Al]

E=mc^2?

I presume they want you to deduce from Einstein's E=mc², what the new speed of light (c) must be. Give it a try.

 

[M98Ranger]

In this new universe, the speed of light in a vacuum will still be constant, as dictated by the theory of relativity. However, the value of the physical constant, c, which represents the speed of light, may be different. In order to calculate the new speed of light in this universe, we can use the equation E=mc^2, where E is the energy equivalent of a 1 kg mass and m is the mass in kilograms. Plugging in the given values, we get 4x10^15 joules = 1 kg (c)^2. Solving for c, we get a speed of approximately 2x10^8 meters per second, or 200,000,000 m/s. This is significantly higher than the speed of light in our current universe, which is approximately 3x10^8 m/s. This shows that even in a new universe with different physical constants, the speed of light will always be a fundamental and constant value.