# Thought experiments about $c$ [closed]

Poincare had a brilliant thought experiment about what if everything in the universe doubled in size, would anybody notice any difference or even be able to measure anything that can be compared with previous measurements.

Similarly what if one morning one the great constants in physics; that is the speed of light suddenly increased to 150% of what it was; would there be observable differences?

## closed as off-topic by Carl Witthoft, CuriousOne, Daniel Griscom, ACuriousMind♦, John RennieJan 26 '16 at 6:42

• This question does not appear to be about physics within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

• If the speed of light was faster would this distort one's perception of time making detecting changes in speed suspect? Since the speed of light is so pervasive as concepts go it affects all other constants and their measurements. And why would Maxwell's equations fail? – 201044 Jan 25 '16 at 14:58
• I'm voting to close this question as off-topic because it's a dupe of a standard question in Halliday&Resnick ; sorry I can't find the duped entry on SE – Carl Witthoft Jan 25 '16 at 20:03
• Poincare died, unfortunately, before modern physics came into its own. We can't know what he would think today, knowing what we know. It's a pretty straight bet that he would stop putting up simplistic suggestions like that. – CuriousOne Jan 25 '16 at 20:45
• Possible duplicate of If everything in the universe doubled in size overnight, would it be noticeable? – ACuriousMind Jan 26 '16 at 4:34
• @CarlWitthoft: Found it $\uparrow$ – ACuriousMind Jan 26 '16 at 4:34

2) Any change in the speed of light would have to be accompanied by either a change in $\mu_0$, a change in $\epsilon_0$, or (far more drastically) a failure of Maxwell's equations, any of which would be easy to detect directly.