STEVEN WEINBERG ON GRAVITY WAVES

On Friday night, July 12, Nobel laureate Steven Weinberg was the guest speaker at the monthly Austin Astronomy Club meeting. His topic was gravitational waves. 

(The grammar can be important. A “gravity wave” is actually a weather event here on Earth. Waves on the ocean are gravity waves. But we call gravitation waves “gravity waves” just as we sometimes are careless with “speed” and “velocity”.)

Dr. Steven Weinberg
(UT Austin)

Dr. Weinberg said that the LIGO (Laser Interferometer Gravitational-Wave Observatory) apparatus was an advance in the technology of perception as significant as Galileo’s use of the telescope. According to the LIGO website, gravitation waves are as different from electro-magnetic radiation (“light waves “) as light is from sound. 

Dr. Weinberg credited A. A. Michelson with the development of the kind of interferometer used for these investigations. (The Michelson-Morely Experiment of 1887 failed to find the "ether" in which light travels.) Reading websites before the lecture, it was apparent to me that these arrangements are extensions of the Michelson-Morley experiment. Long paths of light set at right angles and placed far apart (Hanford, Washington; Livingston, Louisiana; and Pisa, Tuscany), are superimposed so that the smallest variation is revealed by an interference pattern. 

Entropy is real. The Moon will collide with the Earth – eventually. When neutron stars and black holes orbit each other, the losses of energy are (what else?) astronomically immense, and collisions and collapses are recorded as “chirps” of about a half a second. 

 

https://www.ligo.caltech.edu/page/ligo-gw-interferometer

It is also true that as they rotate on their individual axes, massive bodies produce gravitation waves.* Any acceleration does, even when you turn the corner on your bike or in your car. But gravity is extremely weak. At shoulder height, place a golf ball next to a bowling ball and let go of the golf ball. They don’t stick. Now, try it with magnets. I was once told that machine shop gauge blocks are finished so fine that if they touch they cannot be separated because the molecular forces are insuperable: the two blocks become one. Gravity is not like that. 

So, even though gravitation waves were argued by Newton, Leibniz, Kant, and Berkeley, it was 300 years before they were first detected on 14 September 2015. Dr. Weinberg also praised the intellectual honesty of the previous attempts by Joseph Weber and others which meticulously ruled out false positives until nothing was left.

*The gravitation waves produced by a massive superdense rotating body are caused by minor variations within or on the surface of the body. A vibrating perfect sphere produces no gravitation waves.

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