Gravity waves. Should we wave back?
July 9, 2023 10:54 AM Subscribe
Top science explainer Katie Mack (she's eclipsed Neil deGrasse Tyson in ability if not in reach, IMO) covers why gravitational waves make her feel all fluttery inside. (ungated link)
Despite other previouslies, her incredibly readable book, The End of Everything (Astrophysically Speaking) has never been featured in an FPP.
Despite other previouslies, her incredibly readable book, The End of Everything (Astrophysically Speaking) has never been featured in an FPP.
See also: 24 minute YT video on the subject by Dr. Becky Smerhurst.
https://youtu.be/BUmJxZ7PQzw
(Directly posted link because for some reason the linking function isn’t working on my mobile Firefox)
posted by The Pluto Gangsta at 11:41 AM on July 9, 2023 [6 favorites]
https://youtu.be/BUmJxZ7PQzw
(Directly posted link because for some reason the linking function isn’t working on my mobile Firefox)
posted by The Pluto Gangsta at 11:41 AM on July 9, 2023 [6 favorites]
Much better but then NdT is an ass so low hurdle
posted by falsedmitri at 12:17 PM on July 9, 2023 [8 favorites]
posted by falsedmitri at 12:17 PM on July 9, 2023 [8 favorites]
The universe is profoundly strange and we know so little about it.
posted by tommasz at 12:22 PM on July 9, 2023 [2 favorites]
posted by tommasz at 12:22 PM on July 9, 2023 [2 favorites]
Katie's a real scientist, too! I was sad when she left NCSU, but she's great for Perimeter Institute.
posted by MengerSponge at 12:42 PM on July 9, 2023
posted by MengerSponge at 12:42 PM on July 9, 2023
Katie Mack is awesome.
posted by jscalzi at 12:45 PM on July 9, 2023 [2 favorites]
posted by jscalzi at 12:45 PM on July 9, 2023 [2 favorites]
First, A++ post title. Second, what a great column, her enthusiasm is wonderful and that’s a pretty clear explanation of some obscure stuff.
posted by LooseFilter at 12:45 PM on July 9, 2023 [1 favorite]
posted by LooseFilter at 12:45 PM on July 9, 2023 [1 favorite]
Three cheers for Katie!
posted by grumpybear69 at 1:03 PM on July 9, 2023
posted by grumpybear69 at 1:03 PM on July 9, 2023
Gravity waves. Should we wave back?
Do we really want to throw our weight around like that?
posted by jamjam at 1:20 PM on July 9, 2023 [7 favorites]
Do we really want to throw our weight around like that?
posted by jamjam at 1:20 PM on July 9, 2023 [7 favorites]
Do we really want to throw our weight around like that?
just don't be a masshole
posted by lalochezia at 1:28 PM on July 9, 2023 [11 favorites]
just don't be a masshole
posted by lalochezia at 1:28 PM on July 9, 2023 [11 favorites]
You'll never even be noticed otherwise though.
posted by jeffburdges at 2:23 PM on July 9, 2023 [1 favorite]
posted by jeffburdges at 2:23 PM on July 9, 2023 [1 favorite]
Mack is indeed an excellent scientist and communicator, i grew up with a colleague of hers and her insight to even dark matter is quite interesting.
I like Paul Davies, 'The Last Three Minutes', though much older then Mack's 'the end of everything', it profers and interesting perspective from the discipline of physics.
posted by clavdivs at 2:44 PM on July 9, 2023
I like Paul Davies, 'The Last Three Minutes', though much older then Mack's 'the end of everything', it profers and interesting perspective from the discipline of physics.
posted by clavdivs at 2:44 PM on July 9, 2023
I adore Katie Mack and THE END OF EVERYTHING was perversely cheering.
posted by Peach at 3:48 PM on July 9, 2023
posted by Peach at 3:48 PM on July 9, 2023
Just downloaded The End of Everything
posted by supermedusa at 3:51 PM on July 9, 2023
posted by supermedusa at 3:51 PM on July 9, 2023
just don’t be a masshole
After I stopped laughing at this and at jeffburdges' comment, it made me think about the weird positive feedback loop built into gravitation.
Which is that, as a spherical shell of matter falls in toward a massive object such as a black hole it accelerates and speeds up, and that causes its mass to increase, and the increase in mass causes a greater gravitational field to be felt everywhere outside the spherical shell.
And there isn’t really any limit to this process from a naive point of view. As the matter got closer and closer to the central point (aka a singularity), its mass, energy, and the gravitational field it generated would increase without bound.
So all singularities would have to be infinitely massive and generate infinite gravitational fields. I’ve often heard it said that event horizons around black holes are a form of 'cosmic censorship' which prevents impossible things from happening in our universe, but I’m not clear about whether we think the matter crossing the event horizon (assuming any of it does, I guess) does continue to gain mass and generate more gravitation but the field doesn’t cross the event horizon, or whether all such issues are obviated by some other effect peculiar to the interiors of black holes.
posted by jamjam at 4:46 PM on July 9, 2023 [2 favorites]
After I stopped laughing at this and at jeffburdges' comment, it made me think about the weird positive feedback loop built into gravitation.
Which is that, as a spherical shell of matter falls in toward a massive object such as a black hole it accelerates and speeds up, and that causes its mass to increase, and the increase in mass causes a greater gravitational field to be felt everywhere outside the spherical shell.
And there isn’t really any limit to this process from a naive point of view. As the matter got closer and closer to the central point (aka a singularity), its mass, energy, and the gravitational field it generated would increase without bound.
So all singularities would have to be infinitely massive and generate infinite gravitational fields. I’ve often heard it said that event horizons around black holes are a form of 'cosmic censorship' which prevents impossible things from happening in our universe, but I’m not clear about whether we think the matter crossing the event horizon (assuming any of it does, I guess) does continue to gain mass and generate more gravitation but the field doesn’t cross the event horizon, or whether all such issues are obviated by some other effect peculiar to the interiors of black holes.
posted by jamjam at 4:46 PM on July 9, 2023 [2 favorites]
Which is that, as a spherical shell of matter falls in toward a massive object such as a black hole it accelerates and speeds up, and that causes its mass to increase, and the increase in mass causes a greater gravitational field to be felt everywhere outside the spherical shell.
General relativity is way beyond me, but I'm pretty sure that the conservation of matter and energy still holds.
posted by paper chromatographologist at 5:12 PM on July 9, 2023 [4 favorites]
General relativity is way beyond me, but I'm pretty sure that the conservation of matter and energy still holds.
posted by paper chromatographologist at 5:12 PM on July 9, 2023 [4 favorites]
It's facile to say now, but in hindsight it mightn't it be more surprising if there weren't a background of gravitational waves?
posted by hypnogogue at 7:51 PM on July 9, 2023 [2 favorites]
posted by hypnogogue at 7:51 PM on July 9, 2023 [2 favorites]
Yea it would be more surprising.
posted by Dr. Curare at 8:31 PM on July 9, 2023
posted by Dr. Curare at 8:31 PM on July 9, 2023
Yes and yes, but I don't think we imagined we'd be able to sense at this level of detail.
Our best, Earth-based tool can barely sense the biggest things in the cosmos colliding. This uses reference millisecomd pulsars spread across the galaxy to do what LIGO abd other interferometers do, with a massive increase in sensitivity.
The effort LIGO went to to build its interferometer -- a pair of mirrors isolated in the rural forest, in vacuum tunnels half a mile long, with the flattest mirrors we could make, cooled so that bouncing the laser off it doesn't affect the flatness, then run for a long time to be sure we could filter the background noise from meaningful signal. It's highly impressive, but highly limited.
This effort is a stunning use of the data.
posted by k3ninho at 9:46 PM on July 9, 2023 [3 favorites]
Our best, Earth-based tool can barely sense the biggest things in the cosmos colliding. This uses reference millisecomd pulsars spread across the galaxy to do what LIGO abd other interferometers do, with a massive increase in sensitivity.
The effort LIGO went to to build its interferometer -- a pair of mirrors isolated in the rural forest, in vacuum tunnels half a mile long, with the flattest mirrors we could make, cooled so that bouncing the laser off it doesn't affect the flatness, then run for a long time to be sure we could filter the background noise from meaningful signal. It's highly impressive, but highly limited.
This effort is a stunning use of the data.
posted by k3ninho at 9:46 PM on July 9, 2023 [3 favorites]
More to the point, it's like 20 years worth of data. It takes that long to observe enough to make a tentative conclusion.
posted by zengargoyle at 2:47 AM on July 10, 2023
posted by zengargoyle at 2:47 AM on July 10, 2023
2nd the Dr Becky link: Astrophysicist explains big GRAVITATIONAL WAVE discovery! Are they NEW PHYSICS or merging SMBHs? - YouTube
posted by zengargoyle at 2:51 AM on July 10, 2023 [1 favorite]
posted by zengargoyle at 2:51 AM on July 10, 2023 [1 favorite]
It's a pet peeve of mine, but gravitational waves are distinct from gravity waves (something much more everyday).
posted by edd at 4:35 AM on July 10, 2023 [1 favorite]
posted by edd at 4:35 AM on July 10, 2023 [1 favorite]
It’s not really that it’s more sensitive than LIGO, it’s that it’s sensitive to a different frequency. LIGO sees gravitational waves with a wavelength on the size of c 100km to 10000km.
This pulsar timing array instead basically uses the whole galaxy as a detector— so it sees wavelengths much bigger (something like 10^14 km, if I can multiply today; it’s nanohertz scale).
(LISA, a space mission proposed for the next decade or so, will be in between).
posted by nat at 9:54 AM on July 10, 2023
This pulsar timing array instead basically uses the whole galaxy as a detector— so it sees wavelengths much bigger (something like 10^14 km, if I can multiply today; it’s nanohertz scale).
(LISA, a space mission proposed for the next decade or so, will be in between).
posted by nat at 9:54 AM on July 10, 2023
General relativity is way beyond me, but I'm pretty sure that the conservation of matter and energy still holds.
It actually doesn't. But it still doesn't lead to the kind of feedback you were responding to, I think.
(Conservation of energy is tied to symmetry across time, but general relativity has solutions that don't have that property. In our universe in on small scales it's good, but on large scales it's complicated)
posted by edd at 3:38 PM on July 10, 2023
It actually doesn't. But it still doesn't lead to the kind of feedback you were responding to, I think.
(Conservation of energy is tied to symmetry across time, but general relativity has solutions that don't have that property. In our universe in on small scales it's good, but on large scales it's complicated)
posted by edd at 3:38 PM on July 10, 2023
To me, the most straightforward example of the non-conservation of energy is the red shift:
Of course the change in wavelength also leads to a loss of momentum for that photon, so there goes conservation of momentum too, I guess, although since momentum is a vector quantity the accounting might be more complicated — yet as Feynman pointed out in The Character of Physical Law all conservation laws have to be local because if you measure a quantity at two points separated in space, whether or not those measurements are simultaneous or not depends on your frame of reference, so you can’t say that a change in a conserved quantity at one place is balanced by a simultaneous equal and opposite change somewhere else.
I find it hard to believe that conservation of angular momentum can withstand the cosmological red shift either, because circularly polarized light has non zero angular momentum.
posted by jamjam at 10:16 PM on July 10, 2023
The redshifts of galaxies include both a component related to recessional velocity from expansion of the universe, and a component related to peculiar motion (Doppler shift).[35] The redshift due to expansion of the universe depends upon the recessional velocity in a fashion determined by the cosmological model chosen to describe the expansion of the universe, which is very different from how Doppler redshift depends upon local velocity.[36] Describing the cosmological expansion origin of redshift, cosmologist Edward Robert Harrison said, "Light leaves a galaxy, which is stationary in its local region of space, and is eventually received by observers who are stationary in their own local region of space. Between the galaxy and the observer, light travels through vast regions of expanding space. As a result, all wavelengths of the light are stretched by the expansion of space. It is as simple as that..."[37] Steven Weinberg clarified, "The increase of wavelength from emission to absorption of light does not depend on the rate of change of a(t) [here a(t) is the Robertson–Walker scale factor] at the times of emission or absorption, but on the increase of a(t) in the whole period from emission to absorption."[38]As a photon propagates through the expanding universe, it’s wavelength shifts toward the red end of the spectrum, and therefore it loses energy. No one seems to think that energy somehow shows up somewhere else, and any such claim would be vacuous anyway because of the relativity of simultaneity.
Of course the change in wavelength also leads to a loss of momentum for that photon, so there goes conservation of momentum too, I guess, although since momentum is a vector quantity the accounting might be more complicated — yet as Feynman pointed out in The Character of Physical Law all conservation laws have to be local because if you measure a quantity at two points separated in space, whether or not those measurements are simultaneous or not depends on your frame of reference, so you can’t say that a change in a conserved quantity at one place is balanced by a simultaneous equal and opposite change somewhere else.
I find it hard to believe that conservation of angular momentum can withstand the cosmological red shift either, because circularly polarized light has non zero angular momentum.
posted by jamjam at 10:16 PM on July 10, 2023
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posted by rikschell at 10:55 AM on July 9, 2023 [2 favorites]