Eugene Salamin <gene_salamin@yahoo.com> wrote:

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You quoted every word of my post, turning all my sentences into questions, and adding no text of your own. Why? Warren D Smith <warren.wds@gmail.com> wrote:

"Keith F. Lynch" <kfl@KeithLynch.net> wrote:

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Note that the partial pressure of CO2 on Mars is much higher than on Earth, since its atmosphere is 95% CO2.

--the atmospheric pressure on Mars allegedly is about 8.7% of Earth's so again I agree with Lynch.

Unfortunately, your decimal point is off. At that pressure, no spacesuit would be needed, just warm clothing and an oxygen tank. Also, liquid water could exist. But the pressure is actually at most 1/10th of that, and often far less. But the partial pressure of CO2 on Mars is still much higher than on Earth.

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I mean, is there really a gas cloud from some supernova that is microkelvin? Or is this just a speculation?

No such clouds have ever been detected, for obvious reasons, but I don't think anyone doubts they exist. (They emit far too little to be detectable. And since they're transparent to microwaves, they don't cast a shadow in the cosmic microwave background.) After all, clouds from supernovas definitely rapidly expand without limit. And they lose a *lot* of heat when they're still hot, so the first part of the cooling is much faster than adiabatic. Randall Munroe recently pointed out that when a star goes supernova, it's brighter 1 AU away than a detonating H-bomb held against your eyeball -- brighter by nine orders of magnitude. Most of that light comes from the expanding blown-off cloud.

For example, is that Finnish lab that got 100 picoKelvin, really the coldest place in the universe?

As David Makin points out, we have no idea what aliens may have done. If it is the coldest anything has ever been, at least on our planet, is there any risk of dangerous unforeseen consequences? Bose-Einstein condensate requires very low temperatures, but if I understand boson statistics correctly, the larger the condensate, the less critical the temperature is. Could a nanokelvin condensate "infect" its microkelvin surroundings, which would then spread to gradually larger and warmer surroundings until the whole planet underwent such a phase change? I have no idea what that would be like, but I very much doubt it would be survivable. Perhaps that's the solution to the Fermi paradox: Advanced civilization invariably doom themselves, not with high-energy physics as Fermi may have suspected, but with low-energy physics. Remember, you heard it here first. When I experienced the earthquake here in Virginia two years ago, I wondered if that was what was happening, since we had never had earthquakes here before.

To make a completely crazy scenario, let's say we have a neutron star that has planets orbiting it. (It is known from pulsar timings that such exist.) After a long time, the planet gets cold, approaching 2.7K.

That would take a very long time, since neutron stars are very hot, have a very high heat capacity, and gain a lot of heat energy whenever anything collides with them. I suspect that by the time any neutron star has reached room temperature, the cosmic background temperature will have cooled to way below 2.7 K. I don't think there are even any black dwarf stars yet. The universe just isn't old enough.

Now further suppose that the planet is totally magnetized by the enormous magnetic field of the neutron star, which far exceeds any magnetic field we can make on Earth.

My understanding is that the total flux is no greater than the parent star's. The flux *density* is much higher, but only because the neutron star is much smaller. So a planet at an earthlike distance probably wouldn't experience any more magnetic effects than Earth gets from the sun. And it seems unlikely that the planet could be even that close to the neutron star without having been vaporized when the neutron star formed in a supernova explosion. I suppose a planet could have been captured later, but it's difficult to see how. A planet approaching a neutron star would normally either be flung away at the same speed or would be reduced to gravel by the tidal effects.

Now a rogue planet swoops in from outer space and gravitationally interacts with our planet, causing it to escape from neutron star. As a result, it experiences demagnetization cooling.

Maybe in this way temperatures way below 2.7K could be reached naturally. I'm dubious, but it might be possible.

I won't say it's completely impossible, but I think supernova explosions are far more common. An astronomer acquaintance of mine once said there was no mystery about why the sun's photosphere isn't as hot as its chromosphere. He said that the photosphere is where most of the cooling in the solar system is taking place! It's all in your perspective. Seen from outside the sun, the photosphere is a source of heat. But seen from outside a refrigerator, the refrigerator is a source of heat too. (How to use your freezer as an impromptu heat pump: Make lots of ice. Throw the ice outdoors. You'll be heating your house with greater than 100% efficiency!) Seen from the inside, a supernova is just a really powerful refrigerator. So it's not surprising that some of its remains could reach very low temperatures. The same could be said for the whole universe. It didn't start at 2.7 K, you know.