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Me and one lucky follower

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awawa @catmask

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biographic data

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*60s Boeing voice* have you ever considered six AJ-260s as a first stage I insist there are no possible engineering problems that could come out of using six AJ-260s as a first stage

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Great Comet of 1861 (Edmund Weiss, 1888)

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NASA’s Viking 2 probe landed on Mars on this day in 1976.

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This is a fun paper on the arXiv: Towards the Minimum Inner Edge Distance of the Habitable Zone. In other words, given a Sunlike star, how close can we possibly get a habitable planet while gerrymandering all the other variables in our favor? The answer is about 0.4 AU, which corresponds to around 600% the insolation that the Earth receives. Toasty! You need a very dry planet, though, not only to prevent water vapor acting as a greenhouse gas, but to prevent a runaway moist greenhouse scenario. They even explore very hot atmospheres (with high pressure, to keep what water there is liquid), but note that DNA and amino acids become unstable above about 500 K.

I would have thought you would need a very thin atmosphere to reduce heat retention, but apparently if the atmosphere is too thin (<0.1 bar), the planet loses all its water in about a billion years. If pressure is too high, on the other hand, you don't get a proper water cycle (heat is too evenly distributed for precipitation to occur). But the dominant variable affecting where the inner edge of the CHZ is is really the amount of water in the atmosphere. Humidity would have to be around 1% (Earth averages 70% at sea level), and the albedo would still have to be decently high so that a good portion of solar energy was reflected back out into space. Clouds would help with that--but by the time you got enough moisture in the atmosphere to form clouds, you'd be getting enough to significantly heat the planet from water vapor acting as a greenhouse gas.

They only look at the inner edge of the CHZ because, as they point out in the introduction, in principle the outer edge can extend to infinity--a planet with sufficient internal heating from, say, the decay of radioactive elements, or tidal heating from a gas giant primary, could remain habitable even in deep space, if it had a sufficiently thick hydrogen envelope. You don't get hydrogen atmospheres around Sunlike stars because near a star solar radiation is enough to cause hydrogen to escape the upper atmosphere--which is obviously not an issue for a rogue planet.

I think in practice the hard limit for smaller stars would be further out than this, because of the tidal locking issue--slow rotators seem to be a bad fit for this kind of extremal climate. Maybe if it was a really small star, so the inner edge of the CHZ had one of those single-digit-day orbits? I kind of like that mental image: an enormous blood red sun that occupies like six and a half degrees of sky, thirteen times the size of the Sun in our own. A totally cloudless atmosphere, water confined to small patches here and there, and mostly near the poles. Because there's not enough water to properly hydrate the upper mantle, you have drip-and-plume tectonics with enormous mountainous uplands surrounded by flat sandy plains. Or even massive Mars-like uplands and huge shield volcanoes, heavily weathered by the thicker atmosphere, but still towering over the landscape. Eventually the interior of the planet may get so cold the carbon-silicate cycle stops and the atmosphere slowly leaks away, driven by the stellar wind of the close parent star.

But there are other issues with the habitability of red dwarf systems, so maybe not.

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Great Comet of 1861 (Edmund Weiss, 1888)

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Walkway in Calais, France, 1988.

Scan

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North American Sound Dogs

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This is a fun paper on the arXiv: Towards the Minimum Inner Edge Distance of the Habitable Zone. In other words, given a Sunlike star, how close can we possibly get a habitable planet while gerrymandering all the other variables in our favor? The answer is about 0.4 AU, which corresponds to around 600% the insolation that the Earth receives. Toasty! You need a very dry planet, though, not only to prevent water vapor acting as a greenhouse gas, but to prevent a runaway moist greenhouse scenario. They even explore very hot atmospheres (with high pressure, to keep what water there is liquid), but note that DNA and amino acids become unstable above about 500 K.

I would have thought you would need a very thin atmosphere to reduce heat retention, but apparently if the atmosphere is too thin (<0.1 bar), the planet loses all its water in about a billion years. If pressure is too high, on the other hand, you don't get a proper water cycle (heat is too evenly distributed for precipitation to occur). But the dominant variable affecting where the inner edge of the CHZ is is really the amount of water in the atmosphere. Humidity would have to be around 1% (Earth averages 70% at sea level), and the albedo would still have to be decently high so that a good portion of solar energy was reflected back out into space. Clouds would help with that--but by the time you got enough moisture in the atmosphere to form clouds, you'd be getting enough to significantly heat the planet from water vapor acting as a greenhouse gas.

They only look at the inner edge of the CHZ because, as they point out in the introduction, in principle the outer edge can extend to infinity--a planet with sufficient internal heating from, say, the decay of radioactive elements, or tidal heating from a gas giant primary, could remain habitable even in deep space, if it had a sufficiently thick hydrogen envelope. You don't get hydrogen atmospheres around Sunlike stars because near a star solar radiation is enough to cause hydrogen to escape the upper atmosphere--which is obviously not an issue for a rogue planet.

I think in practice the hard limit for smaller stars would be further out than this, because of the tidal locking issue--slow rotators seem to be a bad fit for this kind of extremal climate. Maybe if it was a really small star, so the inner edge of the CHZ had one of those single-digit-day orbits? I kind of like that mental image: an enormous blood red sun that occupies like six and a half degrees of sky, thirteen times the size of the Sun in our own. A totally cloudless atmosphere, water confined to small patches here and there, and mostly near the poles. Because there's not enough water to properly hydrate the upper mantle, you have drip-and-plume tectonics with enormous mountainous uplands surrounded by flat sandy plains. Or even massive Mars-like uplands and huge shield volcanoes, heavily weathered by the thicker atmosphere, but still towering over the landscape. Eventually the interior of the planet may get so cold the carbon-silicate cycle stops and the atmosphere slowly leaks away, driven by the stellar wind of the close parent star.

But there are other issues with the habitability of red dwarf systems, so maybe not.

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I can't be autistic bc I'm actually great at understanding social cues!

[Cut to my POV, a Terminator-style overlay analyzing word choice and body language while over everyone's head a bar labeled Are They Mad At Me shows varying levels]

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unfinished

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There is a *reason* it took me starting adderall to actually start getting good grades in my QM courses in college. I’m still with the angels here.

And God said, "Behold! I have created the fourth primordial force: the weak interaction!"

And the angels all clapped and nodded politely, and there was a long silence; and finally Verchiel, the Angel of Grace, spoke up and asked, "Er, what exactly does it do, O Fashioner?"

And God said, "What do you mean, 'what does it do?' It's the fourth fundamental force of the universe."

And Verchiel said, "You mentioned that. Um. But it's just that the other three sort of have a brand, you know? Gravity helps build large-scale structures, acts over vast cosmic distances, shapes time and space. The strong force is secret, hidden, binding together quarks and all that. Electromagnetism, very cool stuff, somewhere in between. We're all big fans of the whole magnetic monopole double bluff, very clever. But, er. What does this 'weak interaction' do?"

And God said, "It mediates radioactive decay. Sort of."

And Verchiel said, "Radioactive decay? All radioactive decay?"

And God said, "No. Just some kinds."

And Zephaniel, the Chief of the Ishim spoke, and he said, "A whole independent force just to mediate some kinds of radioactive decay?"

And God said, "Well. Not totally independent. Technically it's related to electromagnetism."

And Zephaniel said, "Wait, it's not even a real force?"

And God said, "It's totally a real force. It's just that it's one aspect of a combined electromagnetic and weak force. An electro-weak force, if you will."

And Metatron, the Celestial Scribe, scratched his head at this, but said nothing.

And Cambiel, the Angel of Transformation, said, "Maybe you can walk us through it from the top."

And God Sighed an immense Sigh, and said, "All right, fine.

"So the way it works is that all of space and time is permeated by a field that has imaginary mass."

And Cambiel said, "Imaginary mass, O Generous Provider?"

And God said, "Yes, imaginary mass. It's tachyonic, d'you see?"

And Sarathiel, the Angel of Discipline, said, "Wait a minute, I thought we agreed nothing was going to travel faster than light? All that 'c' business and the whole Lorentz transformation thing. What's happening with that?"

And God said, "Let me finish. The field is tachyonic. The particles in the field all move slower than light."

And Sarathiel had to think about this for a second.

And God said, "The point is, a field with imaginary mass has a non-zero vacuum expectation value."

And this really gave Sarathiel trouble, since he had never been very good at math.

And God, seeing this, went back to explain. "Most fields, like the electromagnetic field, have no effect when they are at their lowest energy state. It's like they're not there at all. If you give a field imaginary mass, then it vanishes only when it's at a very high energy state, and at a low energy state, it has a nonzero value everywhere."

And Sarathiel nodded, but he was confused, because he didn't understand why God would create such a thing.

But Verchiel thought he saw where God was going with this, and he was amazed.

"Truly, you are cunning beyond measure, O Only One Certainly Sound and Genuine in Truth! Only now do I understand your design! For in order to make the universe homogenous and isotropic, it is necessary that all large-scale fluctuations in temperature and mass must be evened out early in the history of the cosmos; and therefore, you have designed a field which will rapidly expand space after the Big Bang, many orders of magnitude in brief moments, and then swiftly and spontaneously decay as it gives up the energy it began with, giving rise to radiation and particles of all kinds as it does, which will condense into the material universe! It is a wonder to behold."

And God said, "What? No. I mean I did, but this isn't the inflaton field I'm talking about. This is something else."

And Verchiel said, "Wait, it's not?"

And God said, "No, I'm going to use a different field to drive cosmic inflation. The properties of this field are totally different."

And now Verchiel was also confused, and lapsed into silence.

And God said, "Like I was saying, this field is a scalar field with imaginary mass, and it does spontaneously decay to a ground state with a non-zero value. But it's not the inflaton field. Instead it combines with the W1, W2, W3, and B bosons."

And Metatron began to flip back through the pages of the Heavenly Record trying to figure out where he'd lost the thread.

And Zephaniel said, "The what bosons?"

And God said, "The W1, W2, W3, and B bosons. I'm sure I mentioned them. You know, the massless bosons?"

And Zephaniel said, "I'm pretty sure we only talked about the W+, W-, and Z0 bosons. All of which you said were going to have mass, O Owner of All Sovereignty."

And God said, "Yes, but this is how they get them, you see. Once this field acquires a nonzero value everywhere, the massless bosons interact with it and get mass. Well, some of them do. They turn into the W+, W-, and Z0 boson. And the photon."

And Zephaniel said, "…and the photon, O Accepter of Invocation?"

And God said, "Well, I did say I was going to unify the electromagnetic force and the weak interaction, didn't I? This is how. Above the critical temperature--right now I'm thinking 10^15 K, but I'm open to feedback on that one--electromagnetism and the weak force act as a single unifying force. Below that temperature, the field gets a nonzero value, you get three massive bosons to mediate the weak interaction, and the photon pops out seperately."

And Zephaniel said, "That seems… a bit overly complicated, doesn't it, O Reinstater Who Brings Back All?"

And God said, "No, it's exactly what we need. Look, that way the W and Z bosons have something to do, but the weak interaction still only travels short distances. Gravity is still the star of the show on cosmic scales, as it were. But now quarks and leptons can swap their flavor!"

And Zephaniel said, rather weakly, "Their… flavor, O Source of Good?"

And God said, "It's this new quantum number I'm trying out, to give the three generations of matter more unique identities."

And Cambiel said, "Three generations of matter? Now I'm really confused."

And God said, "I'm sure I mentioned this. You've got the lightest quarks and leptons, and then two heavier versions of each that can decay into the lighter versions."

And Cambiel said, "What do they do? New kinds of chemistry, is it?"

And God said, "Well, no. Mostly they just decay in a couple microseconds. Or even faster."

And Zephaniel began to rub his temples, and Cambiel sniffed.

And Cambiel said, "This all seems a bit ad hoc to me. Not really the stuff of an elegant and obviously ordered Creation. Why not have four generations of matter? Why not a trillion?"

And God began to grow irritable, and said, "Well, that's not really up to you, now is it? We're going to have three generations of matter, and the electroweak force, and that's that!"

And Zephaniel said, "As long as we are unifying fundamental forces, perhaps we could somehow also unify the electroweak interaction with the strong interaction, or even gravity."

And God hesitated saying, "Well, I haven't decided about that yet. I'm not sure I want gravity to be quantized, you know? Seems to take some of the geometric elegance out of general relativity."

And now it was Zephaniel's turn to sigh, and he bowed his head. "As you wish, O Possessor of Authority of Decisions and Judgement."

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NASA’s Viking 2 probe landed on Mars on this day in 1976.

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it's STILL summer so i have carte blanche to draw my fursona in beach clothes one more time