Alternative Theories of Gravity In Deep Doo-Doo

This is a rather nice article on the troubled times facing many alternative theories to Einstein's General Relativity due to the recent results from the colliding neutron stars. It should be especially useful to laymen to read and understand the methodology and the scrutiny that every theory goes through in physics to be considered to be valid. The one "take-home-lesson" that you should see is that my often-repeated manta here is more true than ever:

"Physics just doesn't say what goes up, must come down. It must also say when and where it comes down" - Warren Siegel.

The quantitative aspect is what is able to separate theories from being wrong to being right. One can't just say "oh, gravity gets weaker as we go farther away". It must say how much weaker, how it behaves with distance, etc.. etc.. and make precise predictions (i.e. to what level of uncertainty). These are "numbers" that we can compare with experiments, if there are already results or if new ones are collected.

This was exactly what happened with the merging neutron stars result, where our verification of the speed of gravity matches that to such precision with the speed of light, that a number of alternative gravitational theories died instantly.

The moral of the story here is that you should not fall in such deep love with any theory yet to have substantial verification, and you should not jump too quickly when new theories appear. I still point out to the OPERA debacle a few years ago when the OPERA project thought they measured superluminal neutrinos. As soon as they published their results, a bunch of theoretical explanations appeared on the e-print arXiv website, proposing theories of superluminal neutrinos, without waiting for independent verification of the validity of the result.

Not surprisingly, they all died of a horrible death when the result was attributed to bad optical cable connection! The history of physics is littered with theories that died and disappeared into obscurity when they could not match the experimental results or observations. Any beliefs or ideology, no matter how beautiful, satisfying, or popular, will crumble at the hands of Mother Nature if she says so.

Zz.