Should Congress repeal the law of gravity?

Absolutely not!

Not being a physicist, I cannot say what kinds of "cascading" effects might affect other laws of nature if gravity were removed, but I suspect that the Earth would lose its atmosphere and probably drift farther and farther away from the Sun.

The constitutionality of repealing this kind of law are not clear to me. Generally, I would imagine that Congress could repeal whatever laws it passed, but I am not sure that Congress actually ever passed the law of gravity. The U.S. Constitution says something to the effect that those aspects of the British common law that were in existence at the time of the passage of the Constitution, to the extent that these are not in conflict with the Constitution, remain in force. I am not sure if a constitutional amendment would be required to remove such a common law component, but it is likely--in fact, almost certain--that the law of gravity preceded the British common law.

There might also be some implications of various treaties that the U.S. has signed. In any event, it hardly seems fair that a decision of this magnitude would be made entirely by the government of a country that represents some five percent of the world's population.

Walking up the Great Wall of China, gravity is a burden, but the solution of doing away with it is worse than the problem.