Does "G-WHIZZES" mean "gravity experts"?

It's a wordplay. Just as a math whiz, in this case, the term stands for persons who are quite good and skilled in the field of physics. Since the article is about the gravitational constant, G, the author thought it would be clever to call these physicists "G-whizzes."

Thank you.

I've always heard it used for anyone who is exceptionally gifted, not just someone in physics or related to gravity. Here is a link for gee whiz.

Ya, I've heard it used as an adjective to show excitement, but never as a noun, as what the article title was going for.

My father uses it occasionally so it is probably pretty out of date.