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John Carlos Baez

If our civilization collapses, extraterrestrial archeologists can look at this and be impressed. Three satellites following the Earth in an equilateral triangle, each 2.5 million kilometers from the other two. Each contains two gold cubes in free-fall. The satellites accelerate just enough so they don't get blown off course by the solar wind. The gold cubes inside feel nothing but gravity.

Lasers bounce between each cube and its partner in another satellite, measuring the distance between them to an accuracy of 20 picometers: less than the diameter of a helium atom! This lets the satellites detect gravitational waves — ripples in the curvature of spacetime — with very long wavelengths, and correspondingly low frequencies.

It should see so many binary white dwarfs, neutron stars and black holes in the Milky Way that these will be nothing but foreground noise. More excitingly, it should see mergers of supermassive black holes at the centers of galaxies as far as... the dawn of time, or whenever such black holes were first formed. (The farther you look, the older things you see.)

It may even be able to see the "gravitational background radiation": the thrumming vibrations in the fabric of spacetime left over from the Big Bang. These gravitational waves were created before the hot gas in the Universe cooled down enough to become transparent to light. So they're older than the microwave background radiation, which is the oldest thing we see now.

It's called LISA - the Laser Interferometric Satellite Antenna. And we're in luck: ESA has just decided to launch it in 2035.

27 January at 18:22 | Open on mathstodon.xyz
130 comments
Marco Zocca
Tom Richardson Ph. D.

@johncarlosbaez let me be the second “Wow!”

27 January at 18:44 | Open on c.im
John Carlos Baez

@CascadeTommy - I've been amazed by this experiment ever since I heard about it. Back in 1999 I wrote this:

"The idea is to orbit 3 satellites in an equilateral triangle with sides 5 million kilometers long, and constantly measure the distance between them to an accuracy of a tenth of an angstrom - 10⁻¹¹ meters - using laser interferometry. The big distances would make it possible to detect gravitational waves with frequencies of .0001 to .1 hertz, much lower than the frequencies for which the ground-based detectors are optimized. The plan involves a really cool technical trick to keep the satellites from being pushed around by solar wind and the like: each satellite will have a free-falling metal cube floating inside it, and if the satellite gets pushed to one side relative to this mass, sensors will detect this and thrusters will push the satellite back on course.

I don't think LISA has been funded yet, but if all goes well, it may fly within 10 years or so. Eventually, a project called LISA 2 might be sensitive enough to detect gravitational waves left over from the early universe - the gravitational analogue of the cosmic microwave background radiation!

The microwave background radiation tells us about the universe when it was roughly 10⁵ years old, since that's when things cooled down enough for most of the hydrogen to stop being ionized, making it transparent to electromagnetic radiation. In physics jargon, that's when electromagnetic radiation "decoupled". But the gravitational background radiation would tell us about the universe when it was roughly 10⁻³⁸ seconds old, since that's when gravitational radiation decoupled."

math.ucr.edu/home/baez/week143

@CascadeTommy - I've been amazed by this experiment ever since I heard about it. Back in 1999 I wrote this:

"The idea is to orbit 3 satellites in an equilateral triangle with sides 5 million kilometers long, and constantly measure the distance between them to an accuracy of a tenth of an angstrom - 10⁻¹¹ meters - using laser interferometry. The big distances would make it possible to detect gravitational waves with frequencies of .0001 to .1 hertz, much lower than the frequencies for which the ground-based...

27 January at 18:50 | Open on mathstodon.xyz
Fred Campaigne :flag_NS:​
Archnemysis

@johncarlosbaez Numbers on this scale break my brain. Is that last sentence saying, basically, 38 seconds after the creation of the universe?

27 January at 21:34 | Open on mastodon.social
hnapel

@Archnemysis @johncarlosbaez

No it's a fraction of a second like 1/100000000000000000000000000000000000000

27 January at 21:42 | Open on mastodon.social
Space Catitude 🚀

@Archnemysis
Much smaller: 38 orders of magnitude shorter than one second. A mind-bendingly small amount of time -- not sure what to compare to.
@johncarlosbaez

27 January at 21:50 | Open on realsocial.life
Space Catitude 🚀

@Archnemysis
But maybe it helps to say 10^-38 could be expanded to "one hundredth of one billionth of one billionth of one billionth of one billionth".
@johncarlosbaez

27 January at 21:55 | Open on realsocial.life
Thanasis Kinias

@TerryHancock
yeah, there’s basically nothing that fast/short to compare with—even things like “light travels this far in that time” break down (10^-30 m is like a millionth of a billionth of the width of an atomic nucleus)
@Archnemysis @johncarlosbaez

28 January at 1:27 | Open on historians.social
Space Catitude 🚀

Looks like it's about 200,000X the Planck time -- which is "the smallest interval of time there can be", more or less.

en.wikipedia.org/wiki/Planck_u

28 January at 2:18 | Open on realsocial.life
John Carlos Baez

@TerryHancock - very much "more or less", since nobody knows what the hell is going on at such short time scales. But still, the Planck time is a good unit to measure times when you're talking about gravitational waves produced by the Big Bang!

28 January at 2:21 | Open on mathstodon.xyz
Poloniousmonk

@Archnemysis

I'm a little rusty on my scientific notation, but i think it's 0.000000000000000000000000000000000000001 seconds.

27 January at 22:43 | Open on autistics.life
John Carlos Baez

@Archnemysis - Not 38 seconds, 10⁻³⁸ seconds. As others have said in different ways, that means the gravitational background radiation was released about 0.0000000000000000000000000000000000000001 seconds after the Big Bang! Check out my timeline of the very early history of the Universe to put this in context:

math.ucr.edu/home/baez/timelin

27 January at 23:56 | Open on mathstodon.xyz
gnarf

@johncarlosbaez @CascadeTommy

"..may fly within 10 years"

Sigh, that hurts a bit. I recently spoke with some frustrated mission planners at ESA. It appears that juggling budgets, 22 member states and the scientific community seems to be quite the thankless job.

27 January at 22:48 | Open on hachyderm.io
John Carlos Baez

@gnarf - it's a very tough job. But the spacecraft do eventually fly... some of them, at least.

@CascadeTommy

28 January at 0:39 | Open on mathstodon.xyz
Thanasis Kinias

@johncarlosbaez
> if all goes well, it may fly within 10 years or so

well, the “or so” seems to have undergone some inflation, but glad to see we’re getting there!
@CascadeTommy

28 January at 1:17 | Open on historians.social
David Monniaux

@johncarlosbaez This gives me solace as I envision a future where much of the earth is too hot for safe (let alone comfortable) living.

27 January at 18:45 | Open on social.sciences.re
Adlangx
abby "AbFC₂H₄" fluoroethane 🏳️‍🌈🏳️‍⚧️

@johncarlosbaez let's hope lack of funding and bureaucracy don't kill it 🤞🏻🤞🏻🤞🏻

27 January at 19:02 | Open on tech.lgbt
DELETED

@johncarlosbaez

I thought I was prety technical by fixing my microwave door (ducttape) but hoo boy these guys nailed it!

Oh, and plus points that it's from ESA!!

27 January at 19:05 | Open on mastodon.social
Nico :pensive_party_blob:
Les capsules du prof Lutz

@johncarlosbaez «If our civilization collapses, extraterrestrial archaeologists can look at this and be impressed. »

No. They'll get confused: «How a specie with so much technical knowledge could go instinct by killing their own ecosystems? Didn't they know? If only we made contact earlier» - 👽 (Google translated)

27 January at 19:08 | Open on mamot.fr
DC Rat

@johncarlosbaez @lutzray You might be interested in reading A Half Built Garden.

27 January at 19:34 | Open on bsd.network
Les capsules du prof Lutz

@sng Thx. Funny: I'm reading Ursula K. Le Guin and this link us.macmillan.com/books/9781250 presents Ruthanna Emrys as a literary descendent of her.

27 January at 19:44 | Open on mamot.fr
DC Rat

@lutzray She very much is a spiritual descendant of Le Guin, yes.

27 January at 19:50 | Open on bsd.network
John Carlos Baez
DC Rat

@lutzray @johncarlosbaez Aliens show up to try to save us from ourselves and stuff happens. See also “Rejoice, A Knife To The Heart”.

28 January at 3:04 | Open on bsd.network
argv minus one

@lutzray

Sadly, we are not all as intelligent as the people who made these devices. If only we were.

@johncarlosbaez

27 January at 20:54 | Open on mstdn.party
Kevin Russell

@johncarlosbaez

Science is exponential, tech and human support is exponential. The growth in economic capacity since WW2 is exponential. 14 people make half a million tons of steel a year. A country smaller than Cuba is the 2nd largest exporter of food. Wealth is available to every human, denying it is an intentional crime. Paying living wages would supercharge the economy.

Humans are emerging.

Our only crisis is Billionaires are trying to take the new world from us.

#Climate #poverty
27 January at 19:11 | Open on mstdn.social
John Carlos Baez

@kevinrns - I agree with you. When I talk about the collapse of civilization I'm talking about climate change. But if we could break free from the grip of the super-rich we could tackle that. Already last year we added 50% more renewable energy last year than the year before. China added enough solar to power more than 50 million homes.

What's that country smaller than Cuba?

27 January at 19:22 | Open on mathstodon.xyz
Kevin Russell

@johncarlosbaez

Its also the largest exporter of flowers in the world, it has schools, theatres, railways, universities, ports, warehouses, manufacturing, daycares, shipping, literature, homes, shipbuilding and it uses less electricity than the crypto scam which produces nothing but crime.

It is 25% switched to wind and sun, so far.

27 January at 21:41 | Open on mstdn.social
Donald Ball

@kevinrns @johncarlosbaez The capacity of the Earth’s ecosystems to function despite our damage is not increasing exponentially. Quite the opposite, in fact.

27 January at 20:02 | Open on triangletoot.party
argv minus one

@donaldball

Our efforts to mitigate the damage seem to also be increasing exponentially, but the oligarchs are desperately struggling to stop those efforts and ensure our extinction.

@kevinrns @johncarlosbaez

27 January at 20:57 | Open on mstdn.party
Kevin Russell

@donaldball @johncarlosbaez

Using safe materials is an extra cost, the thieves care about that. I dont. Make safe things safely.

It will cost more! So what? We can afford it. 14 people make 1/2 a million tons of steel.

Economics was once the study of how to maximize the creation and distribution of scarce goods.

Economics now is the study of preventing the distribution of plentiful goods.

27 January at 21:44 | Open on mstdn.social
Bob Jonkman

Mind blown: Cuba is a huge country compared to the Netherlands:

Cuba: 110,860 km²
Netherlands: 41,865 km²

(via Wikipedia)

Where were all the practical geography lessons when I was in school?

@kevinrns @johncarlosbaez

28 January at 5:52 | Open on mastodon.sdf.org
The Lunatic Dreyfus
Aviva Gary
Jon W

@johncarlosbaez This kind of stuff used to really excite me before our recent leaders decided that human civilization should end in 7 generations or so. So what’s the point of acquiring more knowledge now? Let’s just spend our time and money mitigating the suffering that is coming.

27 January at 19:50 | Open on mstdn.social
Jon F :anarchist_flag: & ☮️

@jw4ke @johncarlosbaez For me the point is that the acquiring of knowledge is itself part of mitigating the suffering.

27 January at 20:23 | Open on aus.social
John Carlos Baez

@jw4ke - I used to work on quantum gravity and particle physics. Now I'm trying to work on epidemiology and carbon emissions, since I don't feel I have luxury to whatever I enjoy.

27 January at 21:25 | Open on mathstodon.xyz
Steve Dodge

@johncarlosbaez
I remember the laser physicist Bob Beyer talking about this project in the 90s, when LIGO was still under development (some of it in a lab that I shared with a mechanical engineer who was designing vibration isolation for the LIGO mirror supports). Even LIGO seemed a bit crazy to me at the time, and LISA seemed completely absurd. It’s exciting to see it gain traction! Fingers crossed our civilization doesn’t collapse before it launches…. 😬

27 January at 19:58 | Open on fediscience.org
John Carlos Baez

@jsdodge - in aome ways it's less absurd to do this in space. LIGO is so sensitive it detects logging in nearby forests.

27 January at 21:42 | Open on mathstodon.xyz
Steve Dodge

@johncarlosbaez
Absolutely — but I’m a tabletop experimentalist, so the thought of working out all of the details *before launch* is a bit terrifying!

(cf Hubble mirrors, same era)

27 January at 21:48 | Open on fediscience.org
j_bertolotti

@jsdodge
Yes, my usual approach of "let me put on the table a bunch of optics and fiddle with them until I figure how to change them to make the experiment work" is unlikely to work particularly well here 😉
@johncarlosbaez

28 January at 7:25 | Open on mathstodon.xyz
Paul Rebmann

@johncarlosbaez this is so beyond me, but it sounds really cool!

27 January at 20:00 | Open on universeodon.com
Dom

@johncarlosbaez Sorry but WE should be proud of our own technological and scientific development. An alien civilization arriving here after travelling light-years would laugh at our low understanding of the universe.

27 January at 20:15 | Open on mstdn.ca
argv minus one

@dom

Do we not marvel at ancient Roman buildings and aqueducts? They may be primitive by today's standards, but they are very impressive for the time when they were built, and demonstrate the potential of a promising young species.

And now, those great works lie in ruin, their potential squandered by the unchecked destructive impulses of cultists, emperors, and barbarians.

Will that dark history repeat once again, this time on a global scale? It seems likely…

@johncarlosbaez

27 January at 21:04 | Open on mstdn.party
Dom

@argv_minus_one @johncarlosbaez Actually, the romans aqueduct still stands.

Also, that is exactly what I meant: Marvelling at our own evolution. On the other hand, aliens being able to travel light-years would only be amazed by our propensity for self-destruction.

27 January at 21:25 | Open on mstdn.ca
John Carlos Baez

@dom - we don't laugh at Neolithic stone circles like Stonehenge. At least I don't. I find them impressive.

27 January at 21:29 | Open on mathstodon.xyz
Dom

@johncarlosbaez I don't think you guys are actually reading my comments.

HUMANS can marvel at our own past and how we developed over time (acknowledging both our past amd present endeavours) but ALIENS (if they were able to come here, hence able to overcome light-years of distance) would not find us special at all because we're a very self-destructive species.

27 January at 21:34 | Open on mstdn.ca
Joshua Foust 🎮
BashStKid

@johncarlosbaez This is very cool. And it would be interesting to have a sensitive low-energy experimental test of Mach's Principle.

27 January at 21:16 | Open on mastodon.online
rebel_without_a_pause

@johncarlosbaez ..."if" will happen the rest is just hoping...

27 January at 21:16 | Open on mastodon.social
rebel_without_a_pause

@johncarlosbaez 2034? Trying to look smart is the entire reason we are here at the destruction of our heaven on Earth. We do not even know a minuscule amount our own planet.

27 January at 21:26 | Open on mastodon.social
Johan | PD1JMB

@johncarlosbaez

So our civilisation collapses and -the- thing aliens find is a fragile satellite constellation? Meh 🤔

27 January at 21:18 | Open on mas.to
Ben Zanin

@johncarlosbaez yoooooo @rjay 👀↑↑ ∆🛰️

EQUILATERAL SPACE LASERS
FOR SCIENCE

27 January at 21:25 | Open on mastodon.social
hnapel

@johncarlosbaez

Great, by that time we can crowdsource the analysis with leftover hardware from the AI hype.

27 January at 21:38 | Open on mastodon.social
hnapel

@johncarlosbaez

Lots of FFT needed! Did they give that guy a medal, the FFT guy, they should have.

27 January at 21:45 | Open on mastodon.social
Klaus Vink Slott

@johncarlosbaez
A friend of mine told me about this project years ago, he was working as an engineer at a company giving a bid on some part of the setup. I was 🤯 about the proportions, the accuracy and what this project will try to achieve.
@liebach

27 January at 22:10 | Open on social.data.coop
DELETED
John Carlos Baez

@longcloud - the plan has been around since the 1990s, people have put a lot of work into it, but now the European Space Agency has decided to put in the millions of euros to actually build it. So I'd call it real, though it won't launch until about 2034.

27 January at 23:52 | Open on mathstodon.xyz
Daniel Fischer
DELETED
Greg Egan

@johncarlosbaez

Typo: it’s 2.5 million km separation, not 25 million km.

It’s kind of sad that the operational lifetime of LISA is only expected to be 4 to 6 years.

28 January at 0:02 | Open on mathstodon.xyz
Jim Flanagan

@gregeganSF @johncarlosbaez Don’t know when the alien archaeologists are meant to arrive, but that 4-6 years seems about right for the collapse of civilization.

28 January at 1:03 | Open on hachyderm.io
John Carlos Baez

@gregeganSF - I wonder what will spell the end of LISA. The satellites do need propellant to stay on course. The proof-of-concept mission LISA Pathfinder used "micronewton thrusters" that shot out cold gas.

scholar.archive.org/work/5r3qr

28 January at 2:25 | Open on mathstodon.xyz
Leo C. Stein

@johncarlosbaez @gregeganSF Spacecraft engineers have a tendency to do such a good job that their consumables often get stretched by factors of 2 or more!

28 January at 4:42 | Open on mastodon.social
DELETED

@johncarlosbaez

Can you answer detail questions? If not, is there a web site with details?

Q1. Does the noise of station-keeping overwhelm sensitivity? If so, how often and for how long are station-keeping operations?

Q2. Do the microscopic instantaneous differences in solar wind between detectors affect the resolution?

28 January at 0:29 | Open on mastodon.social
John Carlos Baez

@LiberalEd - my first answer to both questions is that, as I hinted at in the blog, the plan relies on the cubes being in perfect free-fall in vacuum, not affected by solar wind or vibrations in the satellites. The satellites containing the cubes get pushed slightly by the solar wind, etc., but they detect these deviations from their ideal course by comparing their position to the cubes inside, and correct for these deviations using thrusters. The cubes inside sail on untouched.

28 January at 0:34 | Open on mathstodon.xyz
DELETED

@johncarlosbaez

Thanks, I almost assumed that but thought: wouldn't they have to station-keep a LOT to avoid collision with the cube? I guess I way overestimated the force of the solar wind.

Any place I can go to read more?

28 January at 0:49 | Open on mastodon.social
John Carlos Baez

@LiberalEd - the pressure of the solar wind near Earth's orbit is usually about 6 ×10⁻⁹ newtons/square meter, where a newton is enough force to accelerate a gram at one meter/second². This is not much. The Lisa Pathfinder satellite was a test of concept satellite with micronewton thrusters and a mass floating inside it; it worked fine.

There's a lot of material on it in the references here:

en.wikipedia.org/wiki/LISA_Pat

28 January at 2:18 | Open on mathstodon.xyz
DELETED

@johncarlosbaez
I should have known/thought to check Wiki. Thanks again.

28 January at 2:47 | Open on mastodon.social
davidpmaurer

@johncarlosbaez yes, yes, very nice. we plan on turning all of you into happy meals in less than 2 years.

28 January at 3:51 | Open on mastodon.sdf.org
germanio

@johncarlosbaez wow!

ok ok, you won the first price as the best description someone could do of anything.

now I can't wait for LISA to be up and running!

28 January at 3:57 | Open on mastodon.social
Dorit

@johncarlosbaez For those understanding German, this podcast episode on the wider topic may be of interest: raumzeit-podcast.de/2016/02/18 (Tim Pritlove and Oliver Jennrich talking for close to 3 Hours, back in 2016, on astronomy using gravitational waves.)

28 January at 6:58 | Open on norden.social
aeva

@johncarlosbaez it looks like earth is flying a little kite :D

28 January at 9:33 | Open on mastodon.gamedev.place
Clive Thompson

@johncarlosbaez

This reminds me of Gravity Probe B, which was (for its time) a similarly awe-inspiring piece of engineering — they had to craft two spheres that were, back then, the smoothest objects humanity had ever produced, then start them spinning eternally to become precise gyroscopic measurements of “frame dragging”, or, the relativistic propensity of the earth to slightly drag and deform the shape of spacetime around it as it rotates

Love projects like this so much

28 January at 10:03 | Open on saturation.social
Frosch B

@johncarlosbaez oh ich freue mich schon so drauf!

Andererseits fürchte ich aber auch, dass in den 30ern die Klimakatastrophen-induzierten Konflikte in großer Zahl aufkommen und in die heiße Phase übergehen werden, also sehr unklar ist ob dann noch Zeit und Ressourcen für so etwas aufgebracht werden

28 January at 10:19 | Open on troet.cafe
Felix B. Ohmann

@johncarlosbaez

a: yeah, wow, can't wait to "see" this in action.

b: I imagine the extraterrestrial archeologists will have this technology in their "mobile computers"/"phones" and be like: ah yeah, THAT phase of development with all the carbon-based rockets and the deadly debris shield in orbit... ;)

28 January at 10:52 | Open on abraum.social
dojoe

@johncarlosbaez This is the stuff of SciFi stories where explorers discover technology of a lost civilization and are utterly befuddled, never finding out what it means and feeling lost, alone and insignificant as a result.

28 January at 10:52 | Open on chaos.social
Andrés Ortiz Massó 🐌🌍

@johncarlosbaez

I just hope our civilization is still standing by 2034

28 January at 10:56 | Open on xarxa.cloud
Tito

@johncarlosbaez the problem would came when they put feet on earth and get a conclusion of mankind collapse.

28 January at 11:19 | Open on masto.es
un_pogaz

@johncarlosbaez At what point are we able to have precise trajectories orbite?

^ this shit.

28 January at 11:59 | Open on meow.social
anlomedad

@johncarlosbaez
Awesome toot!
When you said, lasers were bouncing between the gold cubes, I thought: there, that's those flashes, those stellar thunderstorms that can sometimes be seen in deep space, eons away. Other civilisations were/are detecting gravitational waves!
🙋‍♀️

28 January at 13:17 | Open on climatejustice.social
Kernel Bob

@johncarlosbaez What does the blue dot in the graphic represent?

28 January at 13:27 | Open on chaos.social
Expertenkommision Cyberunfall

@johncarlosbaez

So it might be launched just in time, a few years before the breakdown speeds up.

28 January at 13:39 | Open on mastodon.social
Roger

@johncarlosbaez It is indeed as awesome as awesome gets. One suspects that those extraterrestrial, future archaeologists will be utterly baffled as to how such a civilisation was able to create such technology, but yet was incapable of maintaining the conditions required for life on their own planet.

28 January at 13:51 | Open on social.ralnode.net
Nonya Bidniss 🥥🌴
steev hise

@johncarlosbaez hopefully civilization won’t collapse before then. Or degrade to the point where such an achievement is impossible.

28 January at 14:25 | Open on todon.eu
KasTas

@johncarlosbaez another way to look at this project and get amazed is looking at the historical context. The scale and precision achieved since the times of Tom and Jerry (launched 20+ years ago). Or more broadly - GRACE:
en.m.wikipedia.org/wiki/GRACE_

And yeah, from 10 micrometers to 20 picometers :)

28 January at 14:48 | Open on river.group.lt
zheng3_jim

@johncarlosbaez You have to be a lunatic genius to even conceive of this idea, then have a master salesperson get the funding for it, and then have a team of DaVinci level engineers to get it to work.

Meanwhile, Florida.

28 January at 15:51 | Open on mastodon.social
AlisonW ♿🏳️‍🌈

@johncarlosbaez
Great news, so long as civilisation doesn't collapse before 2035!

(if it does I wouldn't be that surprised, sadly)

28 January at 17:56 | Open on fedimon.uk
Liz❤💃
The Modesto Kid

@johncarlosbaez anybody know if gravity waves transmit at same speed as light waves?

28 January at 20:30 | Open on zirk.us
CGdoppelpunkt
Simon Zerafa :donor: :verified:

@johncarlosbaez

May be each one should have a Voyager type ID card with details of where and when the were launched? 🙂

Or perhaps a copy of Wikipedia on suitable storage medium, just in case 🙂

28 January at 21:46 | Open on infosec.exchange
Bargearse

@johncarlosbaez
Perhaps the alien's will be more interested that many humans believing some dude called Jesus rode on a dinosaur ?

@publicvoit

29 January at 0:01 | Open on mastodon.au
bastian
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