Spot ET's Waste Heat For Chance To Find Alien Life

mdsolar passes along this selection from New Scientist describing a (comparatively) low-tech means of scanning the skies for extraterrestrial civilizations: The best-known technique used to search for tech-savvy aliens is eavesdropping on their communications with each other. But this approach assumes ET is chatty in channels we can hear. The new approach, dubbed G-HAT for Glimpsing Heat from Alien Technologies, makes no assumptions about what alien civilisations may be like.

"This approach is very different," says Franck Marchis at the SETI Institute in California, who was not involved in the project. "I like it because it doesn't put any constraints on the origin of the civilisation or their willingness to communicate." Instead, it utilises the laws of thermodynamics. All machines and living things give off heat, and that heat is visible as infrared radiation. The G-HAT team combed through the catalogue of images generated by the Wide-field Infrared Survey Explorer, or WISE, which released an infrared map of the entire sky in 2012. A galaxy should emit about 10 per cent of its light in the mid-infrared range, says team leader Jason Wright at Pennsylvania State University. If it gives off much more, it could be being warmed by vast networks of alien technology – though it could also be a sign of more prosaic processes, such as rapid star formation or an actively feeding black hole at the galaxy's centre.

I'm not saying it's aliens...

[Chuckstar]

obligatory picture of that crazy aliens guy goes here.

Re:

[ShanghaiBill]

Have any of our far flung space craft look back to our planet (and all the surrounding and background stuffs) snap a photo in the infrared spectrum ?

Yes. Quite a few satellites measure the Earth's IR emissions. Much of the sunlight that falls on the Earth is absorbed and re-emitted as IR. That is sort of the whole point of this search. An uninhabited star system will have only a very small fraction (maybe a billionth) of its light absorbed by planets and re-emitted as IR. But an inhabited star system, surrounded by a Dyson Sphere [wikipedia.org], will emit far more, or perhaps all, of it energy as IR. From what we understand about thermodynamics, this is impossib

Re:

[sillybilly]

The complication is that even me, at 37C body temperature, I only radiate as much IR as is required to maintain this temperature. Similar arguments go for my car's body temperature and exhause temperature - where it is indeed huge. but life solved every process at low temperature that we have to use high temperatures for in industrial processes, so can an electric plus battery powered vehicle avoid thermal radiation issues that go much above the body temperature of the environment. Hotblooded living things

Re:

[ShanghaiBill]

You could not measure that there is life on Earth based on the excess infrared heat given off by the life present

That is NOT what they are trying to do. The goal is not to detect planetary life. The goal is to detect Dyson Spheres, or other solar scale civilizations. A Dyson Sphere located at one AU will generate TWO BILLION times as much IR as the Earth.

Re:

[Oligonicella]

Assuming that the civilization advanced enough to build a Dyson Sphere wasn't also advanced enough to recapture IR before it broadcast.

Re:

[mdsolar]

That is covered with their parameter nu. From their table 1: "Power of other waste disposal (e.g. neutrino radiation, non-thermal emission, kinetic energy, energy-to-mass conversion)" so yes, there may be ways to reduce the signature.

Re:

[captjc]

Since when is Slashdot a text mode version of Fark?

[Welcome To Slashdot]

\ I'm surfing on UltraSlashd+++CARRIER LOST+++

It'll be one of two things

[93 Escort Wagon]

Either we will have located the home world of the Quagaars, or it'll turn out to be a garbage pod.

Re:

[dreamchaser]

I somewhat agree, but it could help tell us where to focus other search efforts.

Low Tech?

[mdsolar]

These are infrared array cameras mounted of space telescopes. How high tech do you want? http://wise.ssl.berkeley.edu/ [berkeley.edu]

Thermodynamics

[Myria]

The new approach, dubbed G-HAT for Glimpsing Heat from Alien Technologies, makes no assumptions about what alien civilisations may be like

Such assumptions as, that alien life has not found a way around the Second Law of Thermodynamics?

Re:

[bloodhawk]

perhaps overcoming the law of thermodynamics is unlikely. BUT, utilising the waste heat efficiently and effectively so that any such signature would be all but undetectable from this range I think would be distinctly possible, if not likely.

Re:

[danlip]

That seems like a fairly safe assumption. On the other hand if they get all their power from solar (or wind, hydro, etc., which are just secondary affects of solar) then it seems to me they'd be in equilibrium and they'd have the exact same thermal signature as a no-civilization planet. That seems more likely.

That's no moon....

[mdsolar]

This is not a search for plants but rather Dyson Spheres. http://en.wikipedia.org/wiki/D... [wikipedia.org]

Re:

[danlip]

Dyson Spheres are a rather silly thing to search for, as the technology required is too advanced to fathom (perhaps impossible). It seems the TFA was just talking about looking for aliens with huge power sources. That is certainly possible. But my point was that an advanced alien civilization may just have figured out how to be so efficient as to not need huge power sources. I was also responding to the "makes no assumptions about what alien civilizations may be like" statement in the summary, because it se

Re:

[mdsolar]

They are usually putting gamma equal to alpha in the paper so Dyson spheres, cubes or pyramids is pretty much what they have in mind. http://arxiv.org/pdf/1408.1134... [arxiv.org]

Re:

[khallow]

Dyson Spheres are a rather silly thing to search for, as the technology required is too advanced to fathom (perhaps impossible).

Let us recall that the Dyson sphere idea started life as a swarm of satellites around a star, not as a solid shell. I think I can fathom solar panels, satellites, and orbiting the Sun. That's the basics of a Dyson sphere (well, that and a relativistic traffic control problem which can involve at least as many satellites as there are people currently on Earth).

We could even be there in 100 years.

Indeed. Though it would probably involve self-replicating machines tearing apart Mercury.

Re:

[khallow]

Dysons original paper calculated you would need the mass of Jupiter to make a sphere.

I think Mercury is more than sufficient. We're just capturing the energy output of a star, you don't need a lot of mass for that.

Re:

[TapeCutter]

How is the required ability to outshine said galaxy NOT a severe constraint?. The only thing this technique could possibly detect would be a Borg style alien civilization that has conquered and then overpopulated an entire galaxy, I'd say that puts a very tight constraint on the kind of aliens it can detect and a huge assumption that such galaxy wide civilizations are even possible in the first place. I think they should rename the project to A-HAT ( Aliens Harbouring Awesome Technology)

Re:

[tnk1]

It does put a constraint on the aliens we can find, although it probably wouldn't need to be a galaxy spanning civilization. Outshining an entire galaxy enough to be detected individually can be done by a single star going supernova. While a Dyson Sphere or Swarm or other megastructures would probably not get to that level, they may emit their heat in a range that is very unusual for natural processes. If so, you filter out all light but that in the expected range and it becomes quite clear where those h

Re:

[Ol Olsoc]

Such assumptions as, that alien life has not found a way around the Second Law of Thermodynamics?

Homer Simpson said it best:

https://www.youtube.com/watch?... [youtube.com]

False positives are far too easy

[Dr. Spork]

Basically, this method of searching for aliens returns a positive whenever there is something producing heat which we don't see/understand. I have a feeling that the universe is quite full of such things. But maybe explaining these will help us make scientific advances. When astronomers first discovered a pulsar, they labeled the signal LGM for "little green men". But since then, we learned a lot about astronomy. Explaining apparent anomalies is good for science, and if you want to make the process sexier by talking about possible alien civilizations, I don't see much harm.

Re:False positives are far too easy

[mdsolar]

It comes down to fig. 3 in their paper. http://arxiv.org/pdf/1408.1134... [arxiv.org] Natural source don't have the expected colors for waste heat from a solid surface. But that is the case when perhaps half the starlight in a galaxy is being used for power (their gamma=0.5). So, the civilization has to be pretty much like locusts for it the be easy to discern. There may be some civilization lifetime issues to worry about in that case.

Re:

[khallow]

So, the civilization has to be pretty much like locusts for it the be easy to discern. There may be some civilization lifetime issues to worry about in that case.

For them or for us?

Re:

[mdsolar]

I was thinking them. Other galaxies are pretty far away.

Re:

[khallow]

If they've got half their galaxy colonized and they're "close" say within a few tens of millions of light-years to us, then they might already be colonizing our galaxy. My view is a few tens of millions of light years is not that much bigger a jump than a few tens of thousands of light years. For example, even if they didn't have a clue how to break down and store whatever components they use for their AU-scale system, they could always send a small star cluster over at a significant fraction of the speed o

Re:

[mdsolar]

I suppose if you condensed the material in an AGN jet you get chunk of mass going that fast and reaching another galaxy. There are high velocity stars (not that high though) that might be three body interaction ejections from Andromeda http://www.technology.org/2013... [technology.org]

Is energy inefficiency a measure of progess?

[aNonnyMouseCowered]

What if the advanced civilization turned out to be masters of power efficiency? An analogy from the world of computing: the first electronic computers required the power of a house simply to boot up. The smartphone in your pocket is thousands of times more powerful while using no more power than a small light bulb. Does this mean all we'll find are vacuum tube using spacefarers who use nuclear bombs for rocket fuel?

Re:

[mdsolar]

Energy used efficiently is still energy used. There is always waste heat. The paper addresses what would be an o[optimal waste heat temperature. http://arxiv.org/pdf/1408.1134... [arxiv.org] If you want your waste heat half as warm, your Dyson Sphere has to have four time the radius so you material use becomes excessive.

Re:

[aNonnyMouseCowered]

"your Dyson Sphere"

I'd consider that inefficient. I mean there are far simpler ways of becoming a spacefaring species without hijacking an entire star. If an advanced civilization develops a method for "mind uploading" and downloading to an appropriate android or organic body, they'd only need to build a network of small space stations before they can "email" themselves from hub to hub at the speed of light, something that can well be powered by a small fusion reactor or some other energy source virtually u

Re:

[tnk1]

That is probably going to be the major problem, a Dyson sphere may just look like any other star. The waste heat will likely be some large percentage of the star's output, even with a Dyson sphere. What you'd probably get is an object radiating like a larger, dimmer version of the star inside it. If that is an unusual range of radiation for natural processes, you may be able to distinguish it. If it is close to the range for a natural red giant (for instance), we're out of luck.

Spot the loonie

[turkeydance]

with waste heat. never thought of that.

Far, far away

[Dorianny]

An alien civilization using this technique, would certainly not be able to spot us in our current level of development. In a few millennium perhaps.

Re:

[Dorianny]

You clearly have no idea how far apart galaxies are.

My comment says nothing about the time it takes our heat signature to reach beings in another galaxy observing ours, only that we currently we do not generate enough of it to be detectable.

Waste heat is inefficient

[Anonymous Coward]

So we're looking for dumb aliens?

Re:

[Tablizer]

Why not? The dumb ones may be easier to find. A crime analyst once told me he rarely finds smart crooks, but usually the dumb ones who leave obvious patterns. If they were smart, they'd probably be in a real profession instead of breaking into houses.

Similarly, aliens that don't want to be detected are probably not the ones we'd find first. It's the stupid ones that will stand out.

Kardashev scale

[arielCo]

So, they're looking for civili[zs]ations classified as Type 3 in the Kardashev scale [wikipedia.org]:

A civilization in possession of energy on the scale of its own galaxy.

OK, suppose we find their galaxy, conspicuous like a flamingo. How do we hail in order to confirm?

Re:

[mdsolar]

Would we want to? They sound like locusts.

Re:

[Culture20]

Locusts can taste pretty good if prepared correctly.

Re:

[mdsolar]

They can be assimilated?

Re:

[tnk1]

If they're Type III, they do the assimilating.

And yes, they think we are very tasty indeed. That's why their swarms are on their way and will be arriving in about 38,000 years.

Re:

[Shinobi]

Don't forget that the genestealers arrive a fair bit earlier!

Re:

[tnk1]

A bunch of Type IIs would be sufficient for this, but certainly a Type III would be easier to find.

Problem

[mdsolar]

This method has a difficulty. Most of the starlight from a galaxy comes from stars that will soon be gone. These are the luminous giant stars. But a big investment in a Dyson sphere would probably be made around a star more like our Sun which will stick around for a while. But even if most of the mass in stars is involved in this, it still won't get most of the light so long as it is the low luminosity stars that get the tech investment.

Re:

[Velox_SwiftFox]

And of course, the more efficient the Dyson sphere, the less heat it radiates. At what temperature point would the law of diminishing returns have alien engineers say, "Ah, just radiate the rest of the energy to space, too much trouble to use it for anything more"?

Re:

[mdsolar]

Not really. The luminosity of a Dyson Sphere will be the same as the luminosity of the star it surrounds. The color temperature of the radiation will be lower by a factor of the square root of the ratio of the radius of the star to the radius of the sphere.

The author

[mdsolar]

suggests that the aliens might not abandon these stars just as the energy get is getting good. He may have a point there.

Close enough

[Tablizer]

Matthew 7:16: "By their farts shall ye know them"

The Burrito Galaxy

[statemachine]

Where life's emissions are easily detectable.

I'm not so sure I'd want to make contact.

If UFO's are real

[Nyder]

And they are using such tech that we really can't see them, or know how they work, don't leave heat signatures, etc, I'm not sure this would be good for finding those Alien planets because chances are they got their shit together.

So it might be good to find other aliens who are as stupid as we are and don't mind polluting their planet and we love to pollute ours. I don't want to meet those people, chances are they are as fucked up as we are.

Of course, not saying we'd meet them as we are stupid and instea

Not the kind of ETs we should be looking for

[goodmanj]

This sounds like a great way to discover alien civilizations too huge to give a shit about us, too far away to ever talk to.

Not that we should be picky, but this is punching above our weight.

What about looking for industrial gas

[Eravnrekaree]

i thought they would be looking for industrial gases in the spectrum from planets. It doesnt seem like streetlights and city lights would be significant compared to the amount emitted by suns.

Meh. James Lovelock's idea is better.

[jd]

It's a very simple, even lower-tech approach. Unstable molecules are unstable, stable ones aren't. Life isn't capable of producing stable molecules from stable molecules. Something, somewhere down the line, therefore must produce unstable molecules.

If you use spectrometry and find a planet that has two or more highly reactive molecules (especially if they cannot coexist naturally), that planet has complex life. If you have one reactive molecule that breaks down in sunlight but is being refreshed, that planet must have at least simple life. If the planet has highly reactive molecules that don't readily form naturally, you have life that is nominally intelligent.

No requirement for any technology capable of generating a specific signature. No requirement for the absence of metamaterials. No requirement for a telescope big enough to detect the signature against natural variation.

SKA would be capable of detecting an alien civilization using Lovelock's method anywhere inside of 1,000 light years, given the size and sensitivity currently being proposed. How big would the James Webb telescope need to be to get an IR signature on the industrialized part of the US at that range?

Re:

[mdsolar]

That is covered with their parameter nu. From their table 1: "Power of other waste disposal (e.g. neutrino radiation, non-thermal emission, kinetic energy, energy-to-mass conversion)" so yes, there may be ways to reduce the signature.

Re:

[mdsolar]

We do improve our energy efficiency. For example, combined cycle gas generators are 60% efficient, about twice a good as nuclear reactors. So, in the absence of cogen, 40% of the heat is discarded. But, so it the other 60%. Turning on a light heat the wall the light shines on..... So, it is 100% waste heat eventually. It is the 100% stuff (after use) that must be emitted to space and that is what the paper proposes to search for.