3 ms·

Why are these being called “gravity waves”? They’re nothing of the sort.

nusq 5y ago
They are not gravitational waves but are gravity waves https://en.m.wikipedia.org/wiki/Gravity_wave https://en.m.wikipedia.org/wiki/Gravity_wave
Taniwha 5y ago
They are waves in a density gradient caused by gravity - it's unfortunate, but essentially there are two things with the same name - English is like that some times
dredmorbius 5y ago
There are numerous forms of wave phenomena. In water, surface waves operate principally under the effects of surface tension (small waves such as you'd find in a ripple tank, to about 0.1s period), or gravity, where the mass and inertia of the water moving up and down dominante. There are also pressure waves, which are the result of compression and expansion of a medium. Water compresses poorly, whilst air compresses quite well and elastically. Sound is largely a phenomenon of pressure waves. With the development of very sensitive instruments, gravitational waves in which the geometryof space-time itself is altered can now be detected. Despite the similarity in terms, "gravity waves" and "gravitational waves" are very different phenomena, and we'd need events at the scale of neutron star collisions to be ablet to create readily-detectable gravitational waves. Tonga Hunga was somewhat below this threshold. There are also electromagnetic waves, experienced as EMR (including visible light), AC electric power transmission, and magnetic waves. Again, different phenomena, though the same underlying wave equations describe this behaviour.
- mjevans 5y ago
  Material Wave might be a less confusing term than 'Gravity Wave' which at least outside of this field sounds like what someone in the field might call a 'gravitational wave'. Though that too should be subject to re-definition if a better and more easily communicated understanding of the density of space / time / gravity (as we know it today) makes the term outdated.
  - dredmorbius 5y ago
    "Gravity" and "surface tension" refer to the restorative force in the wave. The terms are well established, at least a century old: https://books.google.com/ngrams/graph?content=gravity+wave&year_start=1800&year_end=2000&corpus=15&smoothing=3&direct_url=t1%3B%2Cgravity%20wave%3B%2Cc0 https://books.google.com/ngrams/graph?content=gravity+wave&y... Compression (sound) waves are also material waves, so that term would generate its own ambiguity. We could instead call the more recently detected gravitational waves "spacetime waves". Though I suspect someone might step in and make some observations about EMR in that context.

nusq 5y ago

They are not gravitational waves but are gravity waves https://en.m.wikipedia.org/wiki/Gravity_wave https://en.m.wikipedia.org/wiki/Gravity_wave

Taniwha 5y ago

They are waves in a density gradient caused by gravity - it's unfortunate, but essentially there are two things with the same name - English is like that some times

dredmorbius 5y ago

There are numerous forms of wave phenomena. In water, surface waves operate principally under the effects of surface tension (small waves such as you'd find in a ripple tank, to about 0.1s period), or gravity, where the mass and inertia of the water moving up and down dominante. There are also pressure waves, which are the result of compression and expansion of a medium. Water compresses poorly, whilst air compresses quite well and elastically. Sound is largely a phenomenon of pressure waves. With the development of very sensitive instruments, gravitational waves in which the geometryof space-time itself is altered can now be detected. Despite the similarity in terms, "gravity waves" and "gravitational waves" are very different phenomena, and we'd need events at the scale of neutron star collisions to be ablet to create readily-detectable gravitational waves. Tonga Hunga was somewhat below this threshold. There are also electromagnetic waves, experienced as EMR (including visible light), AC electric power transmission, and magnetic waves. Again, different phenomena, though the same underlying wave equations describe this behaviour.

mjevans 5y ago
Material Wave might be a less confusing term than 'Gravity Wave' which at least outside of this field sounds like what someone in the field might call a 'gravitational wave'. Though that too should be subject to re-definition if a better and more easily communicated understanding of the density of space / time / gravity (as we know it today) makes the term outdated.
- dredmorbius 5y ago
  "Gravity" and "surface tension" refer to the restorative force in the wave. The terms are well established, at least a century old: https://books.google.com/ngrams/graph?content=gravity+wave&year_start=1800&year_end=2000&corpus=15&smoothing=3&direct_url=t1%3B%2Cgravity%20wave%3B%2Cc0 https://books.google.com/ngrams/graph?content=gravity+wave&y... Compression (sound) waves are also material waves, so that term would generate its own ambiguity. We could instead call the more recently detected gravitational waves "spacetime waves". Though I suspect someone might step in and make some observations about EMR in that context.