Well, look who still doesn't have any detections ? That's right, it's the gravy wavers !
(I'm gonna keep sniggering in a childish manner right up until the point they do get a detection, whence I shall run and hide in a deep hole somewhere)
Originally shared by Jonah Miller
Missing Gravitational Waves Tell us Something About Galaxy Formation
There's been a major result in gravitational wave astrophysics today. Pulsar timing arrays are a way of looking for the random wobbles in spacetime due to the merger of many supermassive black holes across the universe. These black holes are believed to be at the centre of every galaxy and thus merge whenever two galaxies merge.
And we should see perturbations of spacetime due to them. But... so far, we don't. A new paper in Science, using 11 years of data says that this means our current models of galaxy formation are 90% likely to be wrong.
I'm still thinking about and interpreting this result (and reading the supplementary material to understand the author's methods). But this might be big.
For some background, I wrote about pulsar timing arrays here:
http://www.thephysicsmill.com/2015/08/23/distance-ripples-how-gravitational-waves-work/
https://theconversation.com/where-are-the-missing-gravitational-waves-47940
It's nice to see that facetiousness is not a lost art. :)
ReplyDeleteRhys Taylor, do you think that detecting them is unlikely, or do you think their existence is unlikely?
ReplyDeleteEDIT: I found your post. All clarified (including 'gravy wavers'). :)
http://astrorhysy.blogspot.com/2014/05/ours-is-bigger-probably.html
"However, unless something is staggeringly, astonishingly wrong with the theory, given enough time it will be possible to directly detect gravitational waves. Fed up of other astronomers calling them "gravy waves", the GW community has hatched a foolproof plan to massively increase sensitivity and make absolutely sure if the pesky things are real or not. And that involves another giant space telescope - one that makes even Radio Astron look just a little bit pathetic. If it works."
Chris Greene Yes.
ReplyDeleteOh, I'd forgotten I wrote that, which saves me the trouble of having to explain anything. :)
ReplyDeleteVorlon. :)
ReplyDeleteVorlon ?
ReplyDeleteSorry, I refer to people who answer 'Yes' ambiguously to 'A or B' type questions as giving Vorlon responses. Sorry, obscure Babylon 5 reference. My pardon.
ReplyDeleteTo be serious for just a moment, this is actually an interesting story. Non-detections of gravitational waves are reported on a weekly basis, but this is the first time I've seen someone claiming that they should have actually made a detection and failed. My gravy-waver friends used to tell me (in Cardiff - there's no group in Prague) that their detectors weren't anywhere near the sensitivity at which any plausible models predicted anything they could detect. If that's changed then that's really interesting. Unfortunately the paper is in Science and not on astro-ph, and I don't have journal access to check exactly how significant this non-detection is.
ReplyDeleteAleksander Suchanowski
ReplyDelete"It seems to me that modern physics doesn't understand physics at the initial level. It operates on concepts that adopts for granted, and which may not necessarily exist - for example "space"."
You're right, but taking concepts for granted is just another way of saying "makes assumptions". This is necessary in order to make progress. GR predicts detectable gravitational waves; if they are not detected, that will (eventually) falsify the theory (assuming that the detector sensitivity is high enough to really rule out their existence and can't be attributed to technical problems with the instruments).
Making testable predictions and falsifying them is a fundamental part of the scientific method, e.g. this is why GR replaced Newton's theory of gravity. It's true we may not understand physics at the most basic level, but that's why we do the experiments. If we did understand things at that level, science would be basically done.
" If the gravity is a property of matter and space is empty (it is very likely), then a gravitational wave will not have a move in something, and thus does not exist."
Well, no, because if space expands and contracts as according to relativity, it will have testable consequences : in this case the slight loss of energy in a rotating pulsar. GR does not require there to be any substance in space to transmit the waves.
The shade of the late Dr. Forward wants to have a word with you. ;)
ReplyDeleteOK, first time I see someone claiming a significant non-detection not using a Weber bar...
ReplyDeleteRhys Taylor the impression I got from reading Dr. Forwards works is that he passionately believed in the reality of gravitational waves and gravity detectors. And in a lifetime of research failed to get even one partial non-detection.
ReplyDeleteOther researchers would have long ago questioned their initial hypothesis.
Winchell Chung Well, Kip Thorne has recently said that this time they really mean it. https://plus.google.com/+RhysTaylorRhysy/posts/Qu4aUp5GMsT
ReplyDeleteWe'll see what happens.
Winchell Chung Bob Forward gave a great presentation on 4 ways to achieve 0G at Earth's surface (MosCon X in '88(?)). I can only remember one way: hang another Earth mass 10' from the Earth (use really strong pillars to keep them apart) and you will have a 0G location. Very cool dude and sad he's gone.
ReplyDeleteGilmoure T. He later wrote up that presentation as a chapter in his science fact book Indistinguishable From Magic
ReplyDeleteOoh, cool! Will ahve to track down a copy.
ReplyDeleteRhys Taylor "Gravy-waver" speaking. :) :P
ReplyDeleteThe gravitational wave community did itself somewhat of a disservice by being consistently over-optimistic about when it will detect gravitational waves. A big part of this is an evolving understanding of stellar-mass black hole population models and progenitors.
But I think this time if we get a non-detection from ALIGO in the next 5 years, we've got another Michelson-Moorely type non-detection.
Jonah Miller Well, five years is a lot safer than, "next year !" that they claimed every year in Cardiff. :) It got a bit like fusion power : always another year away... they did at least state that they hadn't got a detection because the necessary sensitivity hadn't been reached.
ReplyDeleteThere was a standing agreement that astronomers were allowed to mock the gravy wave community until the point of detection, when we'll all look very foolish. Until then, however.... :P
It's probably worth mentioning here that the decay of binary pulsars being in near-perfect agreement with GR is pretty compelling evidence for gravitational waves. In truth things would be really darn strange if they're not discovered eventually. More exciting, perhaps, than a detection...
Rhys Taylor haha I think I agree with all of that. :)
ReplyDeleteLike I said, I think we fooled ourselves for a long time with overly optimistic population models. (Original LIGO would have been sensitive enough if a binary coalescence had happened in our galaxy, for example)
And of course, many modified theories of gravity may produce waveforms sufficiently far from the templates that we don't detect anything, despite those modified theories agreeing with the Hulse-Taylor measurements.