Last night, I was reading A Brief Welcome to the Universe and in one of the final chapters it mentioned that gravitational waves “have proved elusive to detect”. I thought they had been detected, so I looked up when and it’s exactly 10 years ago today. I thought that was a weird enough coincidence to justify a thread.
Cool. I want to tour a LIGO site. The closest one to me (SFBA CA USA) is an 800 mile drive north to Washington state. I’ve plotted them on my map. Below I include their DD coordinates.
LIGO = Laser Interferometer Gravitational-Wave Observatory
△ LIGO Hanford WA ▲ 46.455, -119.407
➜ https://www.ligo.caltech.edu/WA ■
△ LIGO Livingston LA ▲ 30.563, -90.774
➜ https://www.ligo.caltech.edu/LA ■
△ LIGO KAGRA JPN ▲ 36.435, 137.277
△ LIGO Virgo ITA ▲ 43.631, 10.505
I too would love to tour a LIGO site.
My current not-light reading is the book, “Pushing Gravity: New Perspectives on Le Sage’s Theory of Gravitation”, edited by Matthew R. Edwards.
It’s quite readable, despite the subject matter – it’s far more about concepts expressed in clear English, than about unreadable math. Right now, I’m working on the chapter entitled, “Gravity”, contributed by Tom Van Flandern, and it’s both readable and quite challenging.
An excerpt:
Gravity has properties unlike most other forces of nature. For example, its effect on a body is apparently completely independent of the mass of the affected body. As a result, heavy and light bodies fall in a gravitational field with equal acceleration. This is contrary to our intuitions based on experience with other types of forces. We have come to expect that a heavy body will resist acceleration more than a light one. But gravity does not behave that way. It is as if gravity was oblivious to the law of inertia.
However, on closer inspection, this property is not so surprising after all. Our intuitions are based on experience with mechanical, electric, magnetic, radiation, and other forces, most of which act directly on only part of a body; for example, only on its surface, or only on its charged particles. That action then creates pressure waves that pass through the entire body, forcing other parts of the body not acted on by the force to respond also. Hence, we see the origin of the property of “inertia,” or resistance to motion – the effect of an active force is diluted as each affected part of a body contacts its unaffected neighbors and requires them to change their state of motion also.
– page 95
Nitpicking, but KAGRA and Virgo aren’t actually LIGO sites, though they do share their data with each other. They’re different designs, and built independently of LIGO. They’re also not quite as capable on their own, but still good enough that LIGO plus either or both of them is significantly more capable than LIGO by itself.
There have been plans to build another exact copy of the LIGO design elsewhere in the world (South America, India, and Australia have all been considered), but it’s always fallen through. A shame: All of the very hard design work has already been done anyway, and the quality of the data you get increases better than linearly with the number of sites. With five or six such instruments, you could start looking for some really interesting things.
Thanks! I might try that. The “Brief History” was very accessible until the final two chapters, by J. Richard Gott. The chapter about inflation and the multiverse, in particular, bent my brain into shapes it just didn’t go. I’m not blaming Gott. He did a good job of putting it all into layman’s terms and helpful analogies, but the material was too unfamiliar and way, way too abstruse for me grok.
Hm, I thought this thread was going to be about the recent paper about GW250114, but I see it’s not been mentioned here so I guess that is just yet another coincidence. This was a merger of two black holes, which produced a strong gravitational wave signal detected on January 14, but details were just reported in a paper on September 10. It’s said to be the clearest gravitational wave signal ever detected.
I think gravitational waves must be generating the coincidences. Does the paper touch on that at all? 