iiinova — where your digital self keeps evolving

It's a matter of which are the basic wave properties in each case. For GW it's naturally a local transverse quadrupole action. For sound in air it's a local longitudinal pressure wave. Once are far from the source, you get locally plane waves (by geometry), in both cases.

200

Near field is not locally plane because what is meant by "local" (that is, what is covered by the detector) is too large. It's just a matter of geometry. Whether for electromagnetism or gravitational waves or sound.

100

And yes, LIGO/Virgo detects locally plane transverse action on their detectors. (I linked to the paper on this in an earlier post.) That's what the detector characteristic, the three signals (one in each detector) and the timing information tell us, jointly. 2/2

100

Brian G. aka urbanbohemian 🪩🥂💖 @urbanbohemian.com · 1h

What happens in the near field is more complicated, and I would expect it to not be locally plane for typical detector sizes. It definitely is not in the examples where you place the detector components (pendulum) in a way to probe the quadrupole intensity structure of the wine glass sound wave. 1/

200

Reposted by Markus Pössel

We're on Bluesky, put the link in your post. Put the link in your post. Put. The. Link. In. Your. Post. Links in posts aren't buried or de-prioritized here. This is one of the last platforms you don't have to make interested users do detective work to find the link. Just put it in the post.

71004346

Reposted by Markus Pössel

taz @taz.de · 1h

Mit neuer Identität lehrte Hans Ernst Schneider nach dem Krieg an der RWTH Aachen. Kurz vor seinem Tod wird er enttarnt. Trotzdem schwärmen Studierende noch.

taz.de

Der Fall Schneider/Schwerte: Der Lieblingsprofessor, ein SS-Mann

Mit neuer Identität lehrte Hans Ernst Schneider nach dem Krieg an der RWTH Aachen. Kurz vor seinem Tod wird er enttarnt. Trotzdem schwärmen Studierende noch.

12511

holes. Either system is tiny, seen from far away. And if the only transmission you have are longitudinal sound waves (as for the wine glass, in your analogy) then the result are locally plane longitudinal waves. Which contradict what LIGO/Virgo are measuring. 2/2

200

It is simple, but not in the way you claim. The "it's locally plane longitudinal waves" for sound waves is not a matter of efficiency, it's a matter of geometry. It happens whenever the angular diameter of the source is small as seen from the detector. Whether for a wine glass or merging black 1/

100

Yes! But gravitational wave measurements by LIGO/Virgo require transversal quadrupole action over great distances (amplitude dropping as 1/distance). The wineglass cannot deliver that, not even as an analogy. Or put differently: the analogy doesn't work.

100

If you go into the far field, then in any local region it's going to be locally a plane wave, and longitudinal. What else?

100

support your analogy. It contradicts your analogy. The sensible thing would be to drop the analogy and move on. Why insist on something that is so blatantly contradicted by the data? That's not physics any more. It's some weird kind of secular religion. 3/3

100

good approximation, locally plane longitudinal sound waves. And those locally plane longitudinal sound waves cannot, even if we had some analogy for how they interact with a detector measures, explain what LIGO/Virgo see. You are, for some reason, unwilling to accept that the data doesn't 2/

100

Now we're going back to questions that I thought we had resolved. Which is rather discouraging. I'm not willing to go through the same arguments again and again - that's not a good use of anyone's time. In the far field, a real wine glass as a sound wave source produces waves that are, to really 1/

200

Except we've been there, looked at the sound waves, and after a long discussion you declared yourself convinced that the strict analogy with regular sound waves doesn't work. That analogy is just not compatible with the data. Let's please not fall back behind where our discussion already had gone!

100

more complicated than that. 4/4

100

are linking astrophysical models with observations.) So while it's certainly permissible to think about the analogy as a way of finding a path towards quantum gravity (which is what physicists did as soon as they had found QED), it's not required. And physics quickly learned quantum gravity is 3/

100

electromagnetism without thinking about quantum gravity at the same time. (Just as it is perfectly legitimate to think about all those areas of physics and astrophysics where a really accurate description without quantum gravity is possible - which is almost all of current research where we 2/

100