RIP Frank Drake

[Loren Pechtel]

Then discussing chemical stability and reactivity, and how one need an intermediate state: not too stable and not too reactive.

Then mentioning alternatives to water for a solvent: "sulfuric acid, carbon dioxide, hydrogen cyanide, propane, ammonia, hydrogen sulfide, ethane and methane, nitrogen, and even neon and argon"

In general, protic solvents are chemically aggressive, and their aggressiveness limits the chemistry that can stably dissolve in them. In contrast to protic solvents, aprotic solvents are generally less reactive and stably dissolve a wider range of chemicals than protic solvents.

Solubility of solids in any solvent generally increases with temperature, so cosmically common aprotic solvents such as liquid methane and nitrogen are poor solvents because they are liquid only at very low temperatures. Thus, the nature and temperature of the solvent in which life operates affects both what scaffolds are viable and what heteroatom chemistry is stable in that solvent.

I would reject many of these due to abundance. You need to have pools of the stuff laying around for life to evolve. Lots of pools of it, or else big pools. I would consider anything beyond row 2 out of the question.

CO2 is only an option in a high pressure environment--it has no liquid phase at Earthly pressures, at best it has about 90 degrees, whereas at it's critical point H2O has almost 380 degrees.

I'm having no luck finding a phase diagram for HCN but what I do see looks very bad. It has only 38 degrees of liquid phase at standard pressure and it will self-polymerize (and then subsequently explode) if you're not careful about conditions. That doesn't seem like something you could have on a scale sufficient for life.

Methane is better behaved, 100 degrees at it's critical point. Once again, you'll need a lot of pressure. Given how cold it is that 100 degrees is plenty of range. We actually see methane lakes, it's a good prospect. Note, however, the reaction speed issue--while I would not be inclined to rule out methane-based life there's no methane-based civilizations. Ethane has about 150 degrees and is much more tolerant of lower pressures. Availability could be an issue given it's complexity but otherwise I would consider it a prospect. Propane has even more of the same pluses (300 degrees) and minuses. Butane likewise gives 300 degrees, but more availability issue and it's complicated by the existence of isobutane, for which I can't find a phase diagram.

Ammonia gives 200 degrees at it's critical point, but doesn't do too well at the low end of the pressure. I'll call it a good prospect.

Nitrogen only has 65 degrees at it's critical point, but it's low temperature. I would consider it a possibility, but not for intelligence.

Neon only has about 20 degrees at it's critical point, but it's so cold I wouldn't call that a showstopper in a high pressure environment. A possibility, but due to the cold not for intelligence and a big problem on abundance.

I'm not even going to try with the two sulfur-bearing molecules.

 

[lpetrich]

There are two types of measure of chemical diversity: structural and functional. Hydrocarbons show a staggering structural diversity but are chemically monotonous. As noted in Section 2.1, there are only three stable NmHn compounds, but they show more divergent chemical behavior than all the hydrocarbons. In this section, we address the structural diversity of organosilicons; in the following section (Section 3.2.2), we discuss the functional diversity of silicon.

...
We conclude with a few points. First, the vast potential theoretical space of silicon chemistry is almost entirely unstable in water, and hence not available to a biochemistry based on water as a solvent (see also Section 4.1). This major point has been implied from several examples (e.g., [1,3]) but never fully emphasized. Second, the presence of Si adds a greater diversity of molecules—perhaps enough to contribute as a heteroatom component of biochemistry—to the available chemistry of hypothetical life based in sulfuric acid (see also Section 4.3). Third, the majority of the chemical space of silicon chemistry is available in aprotic solvents such as dry liquid hydrocarbons or liquid nitrogen.

However,

We conclude that silicon chemistry can provide equivalent diversity of function to carbon chemistry, both from the point of view of theoretical as well as synthetic functional chemical space.

Then the thermodynamics of reactions.

Our thermodynamic calculations show that the energies of formation of Si-containing compounds are generally much higher, and therefore less favorable, than their carbon counterparts (Table 2). Such a high thermodynamic cost of the synthesis of silicon compounds could contribute to the scarcity of silicon in biochemistry; it is not, however, an absolute limitation.

 

[lpetrich]

Then they get into solvents. Water is not very good, though "Silicon can be used as a rare heteroatom element in water", thus doing what other trace elements do.

A number of protic solvents have some chemical similarity to water and could in principle be solvents for life. However, bearing chemical similarities to water, protic solvents pose challenges for silicon biochemistry.

Ammonia?

Ammonia on planetary bodies is unlikely to exist as a pure solvent, for two reasons. First, ammonia vapor is easily photolyzed to produce molecular nitrogen, a process that is effectively irreversible outside of the deep atmospheres of giant planets. A substantial planetary ammonia ocean could therefore only be maintained if the planet atmosphere and surface is protected from UV radiation. Secondly, oxygen is cosmically more abundant than nitrogen, such that any environment with condensed ammonia would also have condensed water. Because ammonia and water are fully miscible in each other, the result would be a mixed water–ammonia ocean.

So ammonia oceans are very unlikely. Also unlikely are oceans of other protic compounds, like hydrogen sulfide and hydrogen cyanide.

Then on how sulfuric acid is a good solvent, with silicon compounds having good stability in it.

Then on cold aprotic solvents like liquid nitrogen, methane, and ethane: "cryosolvents". Chemical reaction speeds? Too-fast ones at room temperature may have good speeds at these solvents' temperatures. Solubility? Very low. "Our results illustrate that even the simplest silicon compounds—SiH4 and Si2H6—are expected to only have parts-per-thousand solubility in liquid nitrogen, and more complex molecules of complexity equivalent to amino acid glycine will have sub-parts-per-million solubility. The exception is silicon tetrafluoride, which is estimated to be anomalously soluble."

Among the conclusions, while “carbon chemistry is the chemistry of life, silicon chemistry is the chemistry of rocks”.

The paper has appendices that discuss silicon as a trace element in Earth organisms, and also how feasible silicon biochemistry might be on a carbon planet, one with more carbon than oxygen.

 

[lpetrich]

Wikipedia has a big article on  Hypothetical types of biochemistry discussing a wide range of possibilities.

Alternative-chirality biomolecules - with mirror images relative to Earth biochemistry. That's not a very exotic possibility, but it does suggest a way of recognizing where some organism's biochemistry had a separate origination event from ours.

Non-carbon-based biochemistries - mentioning what I'd discussed earlier, like silicon, boron, and sulfur. Also complex metal oxides like  Heteropolymetalate - heteropoly acids.

Arsenic as an alternative to phosphorus - it would occur as arsenate, AsO4---, an analog of phosphate, PO4---. But arsenate-organic compounds are less stable than phosphate-organic ones.

Non-water solvents - ammonia, methane and other hydrocarbons, hydrogen fluoride, hydrogen sulfide, silicon dioxide and silicates, supercritical fluids like supercritical hydrogen and carbon dioxide, hydrogen chloride, sulfuric acid, formamide, methanol, liquid nitrogen, liquid hydrogen, liquid sodium chloride, ...

Non-green photosynthesizers - we already have some on our planet.

Chlorophyll photosynthesizers often have extra photosynthetic pigments. Carotenoids: red to yellow. Phycobilins: (phycoerythrins) red, (phycocyanins) blue-green.

There is another kind of photosynthesizer, one much less well-known. Halobacteria. They are purple from their photosynthetic pigment: retinal.

Variable environments - many Earth organisms go into suspended animation to survive environments where they would be unable to grow or metabolize or reproduce.

Alanine world - an early set of protein-forming amino acids: alanine, glycine, proline, and ornithine, later replaced by arginine.

The article also got into nonplanetary life, like:

Dusty-plasma-based

Cosmic necklaces: magnetic monopoles on cosmic strings

Inhabitants of neutron stars.

 

[Loren Pechtel]

Then they get into solvents. Water is not very good, though "Silicon can be used as a rare heteroatom element in water", thus doing what other trace elements do.

A number of protic solvents have some chemical similarity to water and could in principle be solvents for life. However, bearing chemical similarities to water, protic solvents pose challenges for silicon biochemistry.

Ammonia?

Ammonia on planetary bodies is unlikely to exist as a pure solvent, for two reasons. First, ammonia vapor is easily photolyzed to produce molecular nitrogen, a process that is effectively irreversible outside of the deep atmospheres of giant planets. A substantial planetary ammonia ocean could therefore only be maintained if the planet atmosphere and surface is protected from UV radiation. Secondly, oxygen is cosmically more abundant than nitrogen, such that any environment with condensed ammonia would also have condensed water. Because ammonia and water are fully miscible in each other, the result would be a mixed water–ammonia ocean.

So ammonia oceans are very unlikely. Also unlikely are oceans of other protic compounds, like hydrogen sulfide and hydrogen cyanide.

Then on how sulfuric acid is a good solvent, with silicon compounds having good stability in it.

Then on cold aprotic solvents like liquid nitrogen, methane, and ethane: "cryosolvents". Chemical reaction speeds? Too-fast ones at room temperature may have good speeds at these solvents' temperatures. Solubility? Very low. "Our results illustrate that even the simplest silicon compounds—SiH4 and Si2H6—are expected to only have parts-per-thousand solubility in liquid nitrogen, and more complex molecules of complexity equivalent to amino acid glycine will have sub-parts-per-million solubility. The exception is silicon tetrafluoride, which is estimated to be anomalously soluble."

Among the conclusions, while “carbon chemistry is the chemistry of life, silicon chemistry is the chemistry of rocks”.

The paper has appendices that discuss silicon as a trace element in Earth organisms, and also how feasible silicon biochemistry might be on a carbon planet, one with more carbon than oxygen.

The more I learn about it the more I see that there basically are no options other than Earthlike biochemistry.

I would accept an ammonia-water ocean as possible on a planet with enough atmosphere.

 

[lpetrich]

The Search for Intelligent Life Is About to Get a Lot More Interesting - The New York Times

Discussing "technosignatures", technology effects that may be observable over interstellar distances. Unfortunately, the article didn't discuss them in much detail. So I researched expected technosignatures, and also something related, expected biosignatures.

•  Biosignature
• Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life | Astrobiology
•  Technosignature
• [2203.10899] The Case for Technosignatures: Why They May Be Abundant, Long-lived, Highly Detectable, and Unambiguous

Biosignatures:

• Atmospheric gases - detectable with near-infrared spectroscopy
• Photosynthetic pigments - detectable with visible-light, near-infrared spectroscopy
• Time variations

"Exoplanet Biosignatures" is a good article.

Atmospheric gases, like O2, O3, H2, H2O, N2, NH3, NO, NO2, N2O, CO2, CO, CH4, C2H6, H2S, CS2, OCS, SO2, CH3SH, (DMS) CH3SCH3, (DMDS) CH3S2CH3, CH3Cl

Some of them don't show up very strongly, like H2, N2, and O2, because none of their vibration modes make an electric dipole moment. They have electric quadrupole moments, which are much weaker, and also collision effects.

Also organic haze.

About photosynthetic pigments, Earth organisms use several kinds, and exobiotas may use additional kinds, so there is unlikely to be some specific spectral features that enable their recognition, unlike for atmospheric gases.

Also discussed possible polarization signatures, like circular polarization for molecular chirality, though that is very weak.

Fluorescence and bioluminescence might also be detected, though those are very weak.

Turning to time variation, a notable kind is seasonal effects, of both atmospheric gases and photosynthetic pigments.

A big problem is false positives, like geochemical effects that might produce oxygenated atmospheres.

False negatives will also be a problem, form biospheres that produce effects that are too weak for detection, or that are entirely subsurface.

 

[lpetrich]

There are lots of kinds of possible technosignatures.

• Astroengineering
  • Dyson spheres
  • Moving planets and stars
  • Asteroid mining
  • Communications networks
  • Vanishing stars
• Planet effects
  • Reflection of light, emission of light (visible), emission of heat (mid IR)
  • Atmospheric gases
• Spacecraft and satellites
  • Panspermia

 

[Jarhyn]

The Search for Intelligent Life Is About to Get a Lot More Interesting - The New York Times

Discussing "technosignatures", technology effects that may be observable over interstellar distances. Unfortunately, the article didn't discuss them in much detail. So I researched expected technosignatures, and also something related, expected biosignatures.

•  Biosignature
• Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life | Astrobiology
•  Technosignature
• [2203.10899] The Case for Technosignatures: Why They May Be Abundant, Long-lived, Highly Detectable, and Unambiguous

Biosignatures:

• Atmospheric gases - detectable with near-infrared spectroscopy
• Photosynthetic pigments - detectable with visible-light, near-infrared spectroscopy
• Time variations

"Exoplanet Biosignatures" is a good article.

Atmospheric gases, like O2, O3, H2, H2O, N2, NH3, NO, NO2, N2O, CO2, CO, CH4, C2H6, H2S, CS2, OCS, SO2, CH3SH, (DMS) CH3SCH3, (DMDS) CH3S2CH3, CH3Cl

Some of them don't show up very strongly, like H2, N2, and O2, because none of their vibration modes make an electric dipole moment. They have electric quadrupole moments, which are much weaker, and also collision effects.

Also organic haze.

About photosynthetic pigments, Earth organisms use several kinds, and exobiotas may use additional kinds, so there is unlikely to be some specific spectral features that enable their recognition, unlike for atmospheric gases.

Also discussed possible polarization signatures, like circular polarization for molecular chirality, though that is very weak.

Fluorescence and bioluminescence might also be detected, though those are very weak.

Turning to time variation, a notable kind is seasonal effects, of both atmospheric gases and photosynthetic pigments.

A big problem is false positives, like geochemical effects that might produce oxygenated atmospheres.

False negatives will also be a problem, form biospheres that produce effects that are too weak for detection, or that are entirely subsurface.

Woot! Called it!

Turns out it's a lot easier to do spectroscopy using starlight than to pick up whispers.

 

[lpetrich]

Turns out it's a lot easier to do spectroscopy using starlight than to pick up whispers.

Why so?

Planets aren't very bright in comparison with their stars. The Earth's reflected light is only about 10^-9 the Sun's light, and to date, the only planets directly detected that are near their stars are very close Jovian planets.

Also, transit spectroscopy is difficult for two reasons. Atmospheres are usually very thin compared to their planets, and one needs to collect a *lot* of photons to get good wavelength resolution. For instance, the Earth's troposphere (height ~ 10 km) increases the Earth's cross section by 0.3%, and to get a good spectral resolution, about 5% or so, one needs the reciprocal of that amount of light in addition to what one needs for broadband observations, like a factor of 20 in this case.

 

[Jarhyn]

Turns out it's a lot easier to do spectroscopy using starlight than to pick up whispers.

Why so?

Planets aren't very bright in comparison with their stars. The Earth's reflected light is only about 10^-9 the Sun's light, and to date, the only planets directly detected that are near their stars are very close Jovian planets.

Also, transit spectroscopy is difficult for two reasons. Atmospheres are usually very thin compared to their planets, and one needs to collect a *lot* of photons to get good wavelength resolution. For instance, the Earth's troposphere (height ~ 10 km) increases the Earth's cross section by 0.3%, and to get a good spectral resolution, about 5% or so, one needs the reciprocal of that amount of light in addition to what one needs for broadband observations, like a factor of 20 in this case.

Well, the point is we are already doing spectral analysis of exoplants as they transit their stars.

 

[Loren Pechtel]

There are lots of kinds of possible technosignatures.

• Astroengineering
  • Dyson spheres
  • Moving planets and stars
  • Asteroid mining
  • Communications networks
  • Vanishing stars
• Planet effects
  • Reflection of light, emission of light (visible), emission of heat (mid IR)
  • Atmospheric gases
• Spacecraft and satellites
  • Panspermia

It's the astroengineering that I think would show up ETs. A Dyson sphere or the like (whatever means a K2 civilization gathers the energy) will be detectable at short intergalactic range. Something has to become of the waste heat--the result would not remotely match any known type of star--you simply can't have a star with that surface temperature and light output. Surface temperature pretty much gives surface gravity, light output gives cross section and thus size. The range of possible values is limited--the energy collectors of a K2 will not be resting on the star and thus won't be subject to the same limits.

 

[FreethoughtPariah]

What a foolish waste of hundreds of millions of dollars. Utter folly for many reasons, chief of which is WE ARE ALONE.

But IF we were not, the "benefits" of potentially communicating with ET are about zero.

Hieroglyphics written by fellow earthlings were unreadable until the Rosetta Stone was discovered. What possible hope do we have of reading from an imaginary ET?
Less than zero. What could they possibly teach us about a place and things they know nothing about? Zero.
How long is the turnaround time to go back and forth? Average, say 100,000 years.

Pretty funny that Drake silliness.

 

[Loren Pechtel]

What a foolish waste of hundreds of millions of dollars. Utter folly for many reasons, chief of which is WE ARE ALONE.

But IF we were not, the "benefits" of potentially communicating with ET are about zero.

Hieroglyphics written by fellow earthlings were unreadable until the Rosetta Stone was discovered. What possible hope do we have of reading from an imaginary ET?
Less than zero. What could they possibly teach us about a place and things they know nothing about? Zero.
How long is the turnaround time to go back and forth? Average, say 100,000 years.

Pretty funny that Drake silliness.

Casual writing is generally impossible to decode without a key. That doesn't mean communication is impossible with a scientific mind, though--there is a language in common. Math, physics, and chemistry are common to all species--while the names will obviously differ what they describe will not.

Spoiler: Pioneer plaque--cartoon nudity

Consider this image. There are multiple messages on here that any starfaring species can decode. Look across the bottom--is it not obvious that it's saying the craft came from the third planet? And note the marks by the planets--that's showing how the quantities 1 through 9 are expressed on the plaque. The starburst on the left will require a starfaring species to decode as pulsars are directional--someone in another star system might not see the same pulsars we do. However, any species that knows the location of all the pulsars around can use that diagram to figure out what star the probe came from. No Rosetta Stone needed because the authors are speaking physics.

 

[Jarhyn]

What a foolish waste of hundreds of millions of dollars. Utter folly for many reasons, chief of which is WE ARE ALONE.

But IF we were not, the "benefits" of potentially communicating with ET are about zero.

Hieroglyphics written by fellow earthlings were unreadable until the Rosetta Stone was discovered. What possible hope do we have of reading from an imaginary ET?
Less than zero. What could they possibly teach us about a place and things they know nothing about? Zero.
How long is the turnaround time to go back and forth? Average, say 100,000 years.

Pretty funny that Drake silliness.

Casual writing is generally impossible to decode without a key. That doesn't mean communication is impossible with a scientific mind, though--there is a language in common. Math, physics, and chemistry are common to all species--while the names will obviously differ what they describe will not.

Spoiler: Pioneer plaque--cartoon nudity

Consider this image. There are multiple messages on here that any starfaring species can decode. Look across the bottom--is it not obvious that it's saying the craft came from the third planet? And note the marks by the planets--that's showing how the quantities 1 through 9 are expressed on the plaque. The starburst on the left will require a starfaring species to decode as pulsars are directional--someone in another star system might not see the same pulsars we do. However, any species that knows the location of all the pulsars around can use that diagram to figure out what star the probe came from. No Rosetta Stone needed because the authors are speaking physics.

This is why I think we in the future should be embedding things like truth tables for processors, and programs they can run which have simulations in them with linguistic labels which allow semantic completion of the language: provide the context in terms of a semantic linkage.

If they can figure out how to launch a simulation which gives them context for the important elements of human language and existence, we could use this to send probes that not only aliens in our universe would be capable of understanding, but indeed we would be capable of explaining our entire existence and even language in terms of pure math to entities whose fields have entirely different dimensional properties.

Given that singularities can be fed matter in a pattern that will cause them to eject bits at a later time traveling at significant fractions of the speed of light, I even wonder if we could create a binary signal by using a singularity to transmit such without a probe.

 

[FreethoughtPariah]

What a foolish waste of hundreds of millions of dollars. Utter folly for many reasons, chief of which is WE ARE ALONE.

But IF we were not, the "benefits" of potentially communicating with ET are about zero.

Hieroglyphics written by fellow earthlings were unreadable until the Rosetta Stone was discovered. What possible hope do we have of reading from an imaginary ET?
Less than zero. What could they possibly teach us about a place and things they know nothing about? Zero.
How long is the turnaround time to go back and forth? Average, say 100,000 years.

Pretty funny that Drake silliness.

Casual writing is generally impossible to decode without a key. That doesn't mean communication is impossible with a scientific mind, though--there is a language in common. Math, physics, and chemistry are common to all species--while the names will obviously differ what they describe will not.
xt in terms of a semantic linkage.

Whales, gorillas, chimpanzees, orangutans and porpoises are species unfamiliar with physics, math and chemistry. What leads you to believe that IF something is out there, it can even see? Why would you make such a presumption? Why would it be more advanced than we are, and even if it is and can see and understand, you made no mention of turnaround time much less its unfamiliarity with us, our DNA and are particular habits, diseases and problems.
Hundreds of millions of dollars squandered and nobody in that realm has a problem with throwing good money after bad, after all, THIS is what they call *science* and it is super hallowed.

 

[Shadowy Man]

Hundreds of millions of dollars squandered and nobody in that realm has a problem with throwing good money after bad, after all, THIS is what they call *science* and it is super hallowed.

Which specific money are you referring to?

 

[steve_bank]

I'd like to get rid of capital equipment depreciation tax write offs for business.

I'd like to get rid of the corporate business welfare sate.

 

[Loren Pechtel]

Whales, gorillas, chimpanzees, orangutans and porpoises are species unfamiliar with physics, math and chemistry. What leads you to believe that IF something is out there, it can even see? Why would you make such a presumption? Why would it be more advanced than we are, and even if it is and can see and understand, you made no mention of turnaround time much less its unfamiliarity with us, our DNA and are particular habits, diseases and problems.
Hundreds of millions of dollars squandered and nobody in that realm has a problem with throwing good money after bad, after all, THIS is what they call *science* and it is super hallowed.

The Pioneer probes are in space. They wouldn't survive atmospheric entry, thus anything that sees that plaque must be capable of seeing them in the environment they exist in--outer space. Thus only species capable of space travel will even be trying to figure out that plaque, if they can find it they should be able to decode it.

And the cost of those plaques is quite small. You're looking at the cost of the mission--but the plaques only weigh a pound. The purpose of the mission was looking at the planets.

 

[Loren Pechtel]

I'd like to get rid of capital equipment depreciation tax write offs for business.

I'd like to get rid of the corporate business welfare sate.

Was that supposed to be in this thread?

 

[Jarhyn]

Whales, gorillas, chimpanzees, orangutans and porpoises are species unfamiliar with physics, math and chemistry. What leads you to believe that IF something is out there, it can even see? Why would you make such a presumption? Why would it be more advanced than we are, and even if it is and can see and understand, you made no mention of turnaround time much less its unfamiliarity with us, our DNA and are particular habits, diseases and problems.
Hundreds of millions of dollars squandered and nobody in that realm has a problem with throwing good money after bad, after all, THIS is what they call *science* and it is super hallowed.

The Pioneer probes are in space. They wouldn't survive atmospheric entry, thus anything that sees that plaque must be capable of seeing them in the environment they exist in--outer space. Thus only species capable of space travel will even be trying to figure out that plaque, if they can find it they should be able to decode it.

And the cost of those plaques is quite small. You're looking at the cost of the mission--but the plaques only weigh a pound. The purpose of the mission was looking at the planets.

To be fair, yeeting a pound of shit that hard costs a lot of money.