The case for building a SETI observatory on the moon | Hacker News Reader

The case for building a SETI observatory on the moon

supercluster.com

166 pointspseudolus76 comments

Y'all might be interested in a robotically assembled km-scale antenna on the farside.

https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

That's super cool, and I hope that they do this.

It's also astounding that it's legal for NASA to embed that much crazy 3p tracker javascript into that webpage, considering that they're publicly funded.

There's a NASA funded lunar colony simulation game for MS-DOS circa 1991. You begin with $10K ;)

Playable on archive via DOSBox:

https://archive.org/details/msdos_Moonbase_1990

It runs in the browser? Archive.org is awesome :)

Yes, and they not only take the time to tweak each game's emulation settings to make sure it works, but they have the attention of the emulator devs too. IA just rolled out an update today! https://mobile.twitter.com/textfiles/status/1312464355812753...

There's also 2010's Moonbase: Alpha[1], which became notorious due to how it applied text-to-speech on in-game chat messages [2][3]

1: https://store.steampowered.com/app/39000/Moonbase_Alpha/

2: https://youtu.be/Hv6RbEOlqRo

3: https://youtu.be/CNPKXfb3rws

I tried for about 45 minutes to play this game (and lunar command) and couldn't figure it out. Is there any guide somewhere online? Specifically my habitat capacity never seemed to increase despite building and wiring/connecting/piping up habitats.

A manual would be handy, I agree...

For the habitats, you need to hook up power and thermal pipes. As long as you connect the habitats together through the white tubes, they only need one hookup with electric/thermal for the entire site.

It seems to take ~ a month in game time for the increased habitat capacity to show up in the 'Population...' menu.

SETI is complete and utter non-sense.

If you don't know why, here's a riddle for you: you are the first space colonist who reaches our closest star, Proxima Centauri. How do you send a message back, such as "We arrived" , plus maybe a photo of a planet you intend to colonize? Piece of cake, you say. Point your parabolic antenna back towards Earth and beam the message. Voyager is doing just that, but from closer to home. Only 20 light-hours away from Earth. Voyager is using a transmitter of about 20 W and an antenna of about 2 meters in diameter. You are about 2000 times farther away. Since radio waves lose power with the square of the distance, you have a problem 4 million times harder to solve than Voyager. Actually, your problem is much, much harder than this: your friends on Earth pointing their antennas towards you are blinded by the star that practically touches your spaceship. You are separated from that star by an angle measured in seconds of arc. You need to shout very loud to be heard over the tremendous noise made by your fiery neighbor. But you can do that, you presumably have a portable nuclear reactor with you and can use gigawatts to solve this essential problem.

But now, imagine you are an alien chatting merrily over radio waves with a friend in the same planetary system around Proxima Centauri. If you don't take a humongous antenna, point it in the absolute exact direction of Earth, and use a few Gigawatts of power to beam a message, how are we, Terrans, supposed to hear you? How is SETI supposed to discover aliens who are not purposely beaming waves straight at us?

I bet you can build an antenna on / near Earth large enough to pick up the Voyager's signal at 4 light years. I don't think that a star emits much radio waves at the same frequently range you choose for your radio transmission, and especially has the same modulation side bands.

That said, MW-class radio transmittets are not heavy, their cooling systems are. You also don't need to transmit continuously, you can send bursts as long as your thermal budget allows. For energy, you have unlimited sunlight.

> 4 million times harder

I don't think you really understand the problem domain. There are 3 main independent parameters you can tweak to improve maximum transmission range: transmit power (100,000x more power has been done commercially), antenna size (we now have a dish antenna over 250x larger), and you can increase the transmission frequency to substantially improve collimation by many orders of magnitude (e.g. use a laser instead of sub-GHz).

> your friends on Earth pointing their antennas towards you are blinded by the star that practically touches your spaceship

A star puts out a lot of power, but it's spread pretty evenly across a blackbody spectrum. You can certainly overpower it within a very narrow frequency range. Your bandwidth/power ratio might be quite abysmal compared to wifi, but it's workable.

> How is SETI supposed to discover aliens who are not purposely beaming waves straight at us

I think the idea is that perhaps they would be beaming waves straight at various stars. This is something I can easily imagine humans doing in the near future.

Could the sun be used as a gravity lens for radio waves? I know people are thinking about doing it for building a telescope, so I assume longer wavelengths work, too.

The assumption of SETI has been that an advanced civilization is broadcasting a narrow-band (in the 'water hole' and possibly modulated) omni-directional signal using a large amount of energy. We can see stars across the galaxy (and, indeed, in other galaxies), so by using some large fraction of a star's energy this should be possible.

We're not far from having the telescope technology that enables us to spectrally sample the atmospheres of extrasolar planets to detect gases that are associated with life (as we know it) and even of technological civilizations (e.g. chlorofluorocarbons). This is a form of SETI too. Using such technology, an alien civilization could beam signals to selected planets that show such signs and save the energy of broadcasting omnidirectionally.

The purpose of SETI is not necessarily to confirm such possibilities (my opinion is that civilizations like us are really rare at this stage of the Universe's evolution - maybe less than one per galaxy). But at least to rule them out.

Easy, just communicate in basically Morse code, but with nuclear detonations.

There's probably a better way, but that sets a lower bound.

Any observatory for that matter. I keep dreaming of humongous mirrors, easily accessible, with no clouds or atmosphere to get in the way. Or, you know, moon. Imagine what we would discover.

I fell like we neglect the moon to a embarrassing degree. It’s right there (cosmologically speaking), it’s got water, plenty of sun light (24/7 even, on the pole), building materials… what are we waiting for?

it builds up static change and rains hyper abrasive Lunar dust into things I think I've read for one.

A ~100m telescope could be assembled in orbit from segmented mirrors and a few falcon heavy lifts. It could image exo continents.

https://science.nasa.gov/technology/technology-highlights/in...

Bias alert: I briefly worked on in space assembly and firmly believe it is the future of space travel, exploration, and exploitation.

I imagine it would be a lot easier to assemble on something you can stand on and mine from, right?

Only an amateur here, but I see James Webb many years and billions overdue and wonder if it wouldn’t be easier, cheaper, faster on ground.

How exactly do you intend to mine, manufacture, and construct things where zero infrastructure exists? Every piece of equipment you would need to do those things would need to be launched not just to low Earth orbit, but all the way to the moon, which is massively more difficult and expensive than building things on Earth and tossing them into orbit here. Building a James Webb equivalent on the moon would cost trillions instead of billions and take decades instead of years.

I think you misunderstand. Nobody wants to build from scratch (manufacture?) a whole telescope. But a segmented mission assembled from components that are separately packaged and perhaps separately launched, is much more affordable and less risky than an equivalent mission that somehow unfolds. And,at some point soon, we'll want spacecraft that are larger than can be lifted in one launch anyway. We do this with the iss, lunar gateway, why not large telescopes or interplanetary spacecraft?

It should be made in the form of a black monolith, I guess. Just for the kick.

Why does it need to be physically ON any planetary body? What are the advantages of having it on the moon rather than free floating in a moon-like orbit? ...or for that matter a more distant eccentric orbit?

I should have read the article... the answer is shielding. even in lunar orbit, it's better than orbiting the Earth for brief periods.

One advantage would be a foothold on a strategically valuable location

Democracies are far too short-sighted for this to be an actual reason. Also, this is just a paper published in a journal.

Size also. It's easy to spool dish wires out on the ground on the moon, hard to spool them out and keep them where you want in orbit.

> hard to spool them out and keep them where you want in orbit.

Well, it's easy if you rotate the whole thing and use centrifugal force, but that has other problems.

Thermal management is easier when you can physically touch other objects, easier to know where you are, easier to maintain pointing accuracy, etc

For large aperture radio-telescopes like Arecibo or VLBA one advantage would be that you can use gravity and the structural reinforcement of the surface to maintain precise formation and location of your reflectors.

One of these days we'll perfect fine stationkeeping and be able to fly large clusters of scopes/reflectors/etc and surface-based scopes will likely become less attractive.

A number of smaller dishes can be made that will robotically unfurl. With the ability to drop a number of them on a flat maria. They will be made with as large as possible self levelling/rotating ability. They can be each driven with their own solar array and will have optical data links so they can work as a large array. They will need an optically linked set of orbiters - which is doable, that can report sequentially. This is a fairly complex task, but once the design is settled and works well, it can be tested and then it can be replicated and an array gradually built with successor dishes. The dishes can be improved as flaws emerge. Being mainly made of aluminum, with vaccuum/dust proof bearings with solar shades it will need to tolerate the temperature range. I think this is a good idea as the other side of the moon is indeed a quiet zone. The lunar lagrange point is also a good place, however the lagrange point will be a hard place for a number of dishes to be sited apart while maintaining precision array positioning.

Makes more sense now than ever with the advent of starlink.

Yes, and in a positive way. Starlink plays a big part in funding Starship/Superheavy, and giving it an initial customer to get launch volume up. That's what will allow the much lower space transportation costs, cited by an astronomer in the article as making this observatory feasible.

I have seen lots of complaints from astronomers about Starlink interfering with optical observations but cannot remember hearing about radioastronomy being affected.

On the other hand - if it is up there, it sure can reflect radiosignals from Earth back again.

Has anyone heard about Starlink and the radioastronomy community?

The impact of these constellations on radio astronomy is arguably worse, not least because it’s harder for the average person to see the impact.

https://www.thespacereview.com/article/3702/1

(They don’t just reflect radio waves, they broadcast them!)

There's just no way that we as a society when deciding between "some shiny new satellite thing produced by an American corporation" versus "the quality of the VLAs operations" will pick the latter.

It pains me to say it, but the average person does not know what the VLA is, nor care at all.

I am not an average person, but have not heard of the VLA before either ..

Anyway, evem when you rephrase it:

Do you want fast internet everywhere?

Or better conditions for science to maybe find aliens?

Not many people would vote for science. Which is economically understandable, so I am all for a moon observatory.

It's not just science to find aliens, radio astronomy answers so many questions that we might not even think to ask - and it is not cost feasible to do all of those observations from space. It's as if in the 18th century, you were like "do we want to spend more money on roads? or do we want to keep funding these stupid experiments that Edison is doing for science?"

No. I love space science, but knowing the origin of the universe will not bring us indoor lighting, refrigeration, clean energy, or anything like that. It is valuable in so far as it's worth some investment, but not so much it prevents us from providing global Internet.

Starlink is not going to solve last mile access problems except for a small number of people. Even rural areas have towns, and it's a matter of spending the money to bring Internet to them the way we did electricity.

You have no idea of what basic physics could learn from cosmology a priori, and neither do I.

Thanks!

One of the problems that no one talks about: how do you protect against meteor strikes on moon? On Earth mountains form slowly over thousands of years but on moon they appear instantly when something strikes the surface. It’s like waiting for bullet coming from sky all the time.

A while ago I read an article about which properties signals might have that could indicate that they originated from intelligent life, something about having "acceleration", higher order derivatives, that are usually not generated by natural events. Does anyone know how this is called?

This is the millionth article on lunar far-side telescopes I've seen that conveniently fails to explain why you'd want to place a radio telescope on the surface rather than just at the Earth-Moon L2 Lagrange point (i.e., the point on the far side of the Moon that orbits with the Moon around the Earth and keeps the Moon between itself and the Earth). I'm sick of not having this obvious question answered, so I dug into it.

Like the lunar surface, a telescope at L2 keeps the Moon permanently between itself and the Earth to block incoming radio waves. For a fixed telescope size, going down into the Moon's gravity well increases costs tremendously. And, although doing construction in a vacuum is never easy, it's a lot easier when you're in zero-g and you don't need a crane! Unlike the far-side surface, L2 has exposure to sunlight for power for ~90% of the time. (You would still need a relay satellite in a different lunar orbit for communications, of course, just like the far-side surface.)

As far as I can tell from browsing the article

https://arxiv.org/abs/2009.12689

and the much more helpful analysis of the lunar radio environment that they cite

https://sci-hub.st/https://arc.aiaa.org/doi/pdf/10.2514/6.IA...

the only benefits to going to to the surface is (1) you get better shielding of the extremely low frequencies (≲ 1 kHz) which are long enough wavelength to diffract around the Earth, but don't think those are detectable unless you have a telescope that's many kilometers in size. (2) you avoid radio signals from satellites in geostationary orbits, but these should be very small since the transmitters are pointing toward the Earth.

Indeed, the faculty member who is advising the undergraduate intern lead author says

> “The first SETI observations that are done from the lunar farside will be done from orbit, there’s no question about that,” says Andrew Siemion, the director of the Berkeley SETI Research Center and the second author on the paper. “I think eventually we absolutely want to do something on the surface because we want to build a very large aperture telescope, but even when we’re at that point I don’t think that would negate the utility of doing things from orbit as well.”

and I think he's downplaying how tremendously costly going to the surface would be for very little benefit.

EDIT: Note that the FARSIDE array on the surface they mention is much better justified, but it's not SETI, it's an array, the surface benefits from solar storm shielding, and it probably only makes sense because it piggybacks on high bandwidth connection for the NASA Lunar Gateway. More details here:

https://www.lpi.usra.edu/leag/white-papers-astronomy/FARSIDE...

https://twitter.com/di_goldene_pave/status/13123915724079554...

The article literally says that a satellite in orbit is likely the first step.

Also, the further you are from the moon - the worse the shielding.

First, the orbital option described in the article is not L2 but rather a low lunar orbit which spends only a small fraction of it's time in the lunar shadow.

Second, in my comment I literally quote the "first step" claim and explain why it's an extreme understatement, in particular because the shielding is not worse except for undetectable wavelengths and sources not actually pointed at the telescope. It's like saying we should we should build transparent houses so we get more vitamin D but of course as a first step we should go outside or take a multivitamin.

From this study: https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

The sun is cited as a significant source of noise that can be shielded by the lunar body.

Yes, thanks! That's mentioned in my edit (although it should just be "solar wind" rather than "solar storm") and the twitter thread I link. Note that that's only a particular (though valuable) frequency range, and that it's still unclear to me whether it's cheaper to go down to the lunar surface rather than just build a 10 times larger telescope at L2.

> And, although doing construction in a vacuum is never easy, it's a lot easier when you're in zero-g and you don't need a crane!

That's not exactly true just yet!

All our construction knowhow is based on thousands of years of building things on Earth's surface, under a constant 1G force pulling everything in a single direction, as well as a landmass to brace against. Every technique we have has these conditions baked in as assumptions; we exploit them all the time, without even thinking about it. Like, e.g. if you put some mortar on a brick, and then a brick on top of that, you're relying on gravity to supply the pressure that makes the two bricks strongly bound.

Meanwhile - AFAIK - we have zero experience in constructing anything in 0G, beyond assembling some large prefabs. The closest we come to microgravity construction is whatever it is that underwater welders do, but that's still not the same.

With this in mind, it may be that for now, building installations on Moon's surface will be easier than constructing them in space.

I think your overall point is wrong, but it would be a large discusssion. So I'll just concentrate on this: a telescope on the moon or at L2 will, in fact, be large pre-fab. Indeed, we have zero experience building anything in a vacuum in gravity, but we have decades of experience assembling pre-fab structures in zero gravity vacuum. That's what will be easiest.

His overall point was that we have only experience constructing in g and allmost zero experience constructing in zero g.

And that seems very true to me.

I know that was his point. I acknowledged that although I think his overall point was very wrong I wasn't going to debate it because it would be a sprawling discussion.

> Meanwhile - AFAIK - we have zero experience in constructing anything in 0G, beyond assembling some large prefabs.

Weren't the ISS and Mir constructed in zero G? Well, in free fall but that's still zero gravity in effect.

That's just assembling large prefabs, though, which I explicitly excluded from my "zero experience" observation.

Wouldn't construction of an orbital observatory consist of putting together prefabs? Not to mention, modern construction often does consist of putting together prefabricated pieces so saying we have no experience with construction in zero G only putting together prefabricated components is somewhat contradictory.

That depends if that was what the original comment meant.

But still, I fail to see how attaching prefabs in 0G is going to be easier than doing it in 1G, or even 0.166G. It's nice to have a well-defined "down" direction and a landmass to brace against. You don't need station keeping and magic trickery to keep angular momentum in check.

The main difficulty I'd see with assembling prefabs on the Moon would be landing them.

I will change fields to use tha data and find life out there!! :-)

Good idea! 1972 was so long ago...

Space brothers did it first

Yes please.

I'm fed up with titles like this that suggest that an entire scientific community, or at least some body with a legitimate claim to representing the interests of that community, wants something when all that is really happening is that some particular group of scientists has submitted a proposal.

Here's the first line of the article:

> On Monday, a group of researchers sponsored by Breakthrough Listen, the world’s largest program, submitted a paper to National Academy of Sciences’ Planetary Science and Astrobiology Decadal Survey that makes the case for establishing a SETI radio observatory on the farside of the moon.

Note that this line is also incorrect due to a missing word. Breakthrough Listen may be the world's largest SETI program, but it is certainly not the world's largest program, whatever that would even mean.

So this is some particular group of SETI specialists, which I highly doubt represents the interests of the astronomical community at large (I would guess that only a small fraction of astronomers even work on SETI).

Don't get me wrong, I'm not criticizing the project itself, just the misleading title of the article and the general decline in journalistic standards.

I think these concerns would be addressed by adding a single word to the title. "Some", at the beginning.

I think a more accurate title would be something like:

SETI Project Proposes Building an Observatory on the Moon

Quite, yes.

NB: https://www.supercluster.com/editorial/the-case-for-building...

Title: The Case for Building a SETI Observatory on the Moon

Not worth the emotional investment. Of course "some" is assumed. And isn't it more correct to talk about who wrote the paper, than which organization published it?

> Of course "some" is assumed.

That's not how it initially parses for me, and I think for most people.

As for the emotional investment, for this one case certainly not, but this same pattern keeps coming up time and time again, not to mention the constant barrage of other nonsensical statements the media constantly exposes us to. I think this incessant stream of micro-aggressions against logic and common sense ends up having a significant impact on our well-being and at a larger scale may even be contributing to extremism, conspiracy theories and the growing absence of any semblance of truth from the ambient political discourse.

> And isn't it more correct to talk about who wrote the paper, than which organization published it?

I'm not sure what you mean by that.

Hacker News readers are fed up with inaccurate generalizations.

Fair point. It's a bait-and-switch, motte-and-bailey equivocation tactic: on casual reading, the bailey is that "all astronomers‘, or a majority, or some authoritative generally representational body speaking authoritatively, is making a claim. The motte is that those making the claim are astronomers.

https://rationalwiki.org/wiki/Motte_and_bailey

The harm is greater in that we're used to headlines referencing, say, public opinion (majority or at least plurality of a population), organisations (official spokesperson as opposed to some arbitrary worker or whistleblower), etc.

It's a cheap shot. All the more so because it seeks to borrow from the greater reputation and fame of the larger group, admitting by deed the obscurity of the actual group in question.

"SETI Group Wants to Build Radio Observatory on Moon" avoids all these problems here.

Addendum:

The article originally appeared with the title "The Case for Building a Seti Observatory on the Moon" here:

https://www.supercluster.com/editorial/the-case-for-building...

Link and title have just been changed from https://www.smithsonianmag.com/science-nature/why-astronomer...

The submitted title was "Astronomers Want to Build a SETI Observatory on the Moon" which came from the submitted URL (https://www.smithsonianmag.com/science-nature/why-astronomer...). I think you're reading it with the wrong quantifier: to me the claim is not "[all] astronomers want [etc.]" but "[some] astronomers want [etc.]", which is perfectly reasonable.

But it's fine to change a title when it's landing the wrong way with some readers, and it seemed like there was a better link in this case, so a mod changed both the URL and title.

Ah yes. The death star.

But it’s a moon, not a space station.

That's no moon

Trollish usernames aren't allowed on HN because they effectively troll every thread they post to. I've banned the account, and would be happy to rename and unban it if you want to pick a more neutral username. Best to email hn@ycombinator.com if that's the case.

https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme...

I think we need at least some 50yrs of physics to understand how to even begin tapping into the cosmic internet

As with fusion and processing power, some things are faster if you wait for the advancements instead of building it with today's technology.

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