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Author Topic: Science Thread (and !!SCIENCE!! Thread!)  (Read 79569 times)

McTraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #510 on: December 12, 2019, 12:55:27 pm »

I don't understand why that article says that the heating from radiation was negligible because the membranes were "far enough" apart.  I feel this is something that got missed in the media version of the article; heat transfer by radiation has no distance limit.

Maybe they meant to say that the heat transfer they observed didn't match the difference-of-temperatures-to-the-fourth-power that would be expected from radiation?
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Il Palazzo

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #511 on: December 12, 2019, 02:35:44 pm »

I don't understand why that article says that the heating from radiation was negligible because the membranes were "far enough" apart.  I feel this is something that got missed in the media version of the article; heat transfer by radiation has no distance limit.

Maybe they meant to say that the heat transfer they observed didn't match the difference-of-temperatures-to-the-fourth-power that would be expected from radiation?
I think it just means that they're far enough for the near-field heat transfer to be negligible or otherwise controllable.
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feelotraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #512 on: December 12, 2019, 07:32:45 pm »

This bit caught my attention:

"Because molecular vibrations are also the basis of the sounds that we hear, this discovery hints that sounds can also travel through a vacuum ... Now, you can shout through a vacuum."

Shit, I'll have to break the habit of going into space to scream.  >:(
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McTraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #513 on: December 12, 2019, 07:52:23 pm »

My mind has just been blown: If Reynolds number is low enough, time drops out of fluid mechanics equations.

There are experiments you can do by putting drops of food coloring in a viscous fluid like corn syrup, mixing them up, and then unmix them.  :o
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Max™

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #514 on: December 12, 2019, 09:04:18 pm »

I don't understand why that article says that the heating from radiation was negligible because the membranes were "far enough" apart.  I feel this is something that got missed in the media version of the article; heat transfer by radiation has no distance limit.

Maybe they meant to say that the heat transfer they observed didn't match the difference-of-temperatures-to-the-fourth-power that would be expected from radiation?
Think they meant "not far enough" because they mentioned hundreds of nanometers, which is shorter than the infrared wavelengths for black body emissions at temperatures this experiment was being conducted under.

I mean, I assume they weren't conducting this experiment hot enough for visible emission since the vacuum would be ruined by the membranes vaporizing.
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Il Palazzo

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #515 on: December 13, 2019, 01:23:52 am »

No, Max. I think they do mean far enough. Look up near-field radiative heat transfer. It can increase radiative heat transfer orders of magnitude above what one can get from black body radiation, providing the two bodies are close enough (on the order of hundred of nanometers or less).

Besides, what you're talking about is resolution limit i.e one can't distinguish an object as separate if its size is smaller than the wavelength of probing light. It can be colloquially said that small enough objects are invisible to radiation of large enough wavelengths. But it does not mean invisibility in the sense that radiation passes through or stops exchanging energy between two surfaces if the separation is smaller than its wavelength. It just means that one couldn't use e.g. infrared radiation to detect a nanometer-scale gap.
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Max™

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #516 on: December 13, 2019, 02:47:29 am »

Nah, nothing so involved as that, I was just trying to picture what would happen to a photon emitted into a gap shorter than the wavelength, it seemed like a weird idea.
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Trekkin

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #517 on: December 13, 2019, 09:02:10 am »

No, Max. I think they do mean far enough. Look up near-field radiative heat transfer. It can increase radiative heat transfer orders of magnitude above what one can get from black body radiation, providing the two bodies are close enough (on the order of hundred of nanometers or less).

In a broad sense, it's similar to Förster resonance energy transfer in that regard. People try to think of photon wavelength as size, but magnitude is a closer equivalent, and the difference shows up when you start looking at how they move across very small scales.
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Max™

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #518 on: December 13, 2019, 01:43:06 pm »

Incidentally the error I made was due to not expecting the near field effects to jack the transfer up because fuck you quantum nonsense, but I've not been near that field in my various studies.

Brain pulled up the thermal wavelengths and those gaps and went "ha ha, the fuck you smoking?"
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McTraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #519 on: December 17, 2019, 08:17:35 pm »

I've decided that from now on whenever I hear "AI" I substitute the phrase "advanced pattern recognition and extrapolation."  I think if they'd have called it that from the beginning people would not think it is so magic. After all, that's basically what every type of "AI" we have today does.

It also avoids the annoying debates about "is it intelligent" or ethics or whatever.  A "machine that has advanced pattern recognition and extrapolation capabilities" sounds way less existentially threatening than "an artificial intelligence".
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feelotraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #520 on: December 18, 2019, 01:08:00 am »

I've decided that from now on whenever I hear "AI" I substitute the phrase "advanced pattern recognition and extrapolation."  I think if they'd have called it that from the beginning people would not think it is so magic. After all, that's basically what every type of "AI" we have today does.

It also avoids the annoying debates about "is it intelligent" or ethics or whatever.  A "machine that has advanced pattern recognition and extrapolation capabilities" sounds way less existentially threatening than "an artificial intelligence".
(my bolding)

But even that use is context sensitive.  Just about no game AI even aspires to such lofty heights...
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wierd

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #521 on: December 18, 2019, 01:12:24 am »

This is the kind of classification mixup that happens when language is technically correct, but misunderstood by the masses.

Take for instance, if I used the phrase "artificial life form", and was talking exclusively about creating synthetic single celled organisms using synthetic membranes, etc-- to try to tease out how life might have gotten started.

Some journalist hears the phrase, and thinks "EGADS! Dr Moreau!"

No, it's just a single celled replicator in its most simplistic of forms, and has features approximating those of a lifeform (eg, it undertakes the 5 life processes, and could be classified as a lifeform-- but is basically just a soap bubble with some special stuff inside it.)
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feelotraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #522 on: December 18, 2019, 03:04:47 am »

I think the problem is down to the hardcore turn to empiricism post WWII (... Turing has a lot to answer for).  :)

That is unless the term artificial has nothing to with the substrate but is functionally equivalent to simulated.  But then humans are also often AI!  (Mind the sarcasm.)

But the term 'AI' as used in science, and elsewhere, is an advertising catchphrase designed for publicity rather than clarity.  That much, I think, we all agree on.  :D
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Iduno

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #523 on: December 20, 2019, 09:46:32 am »

I can't think good today. Can someone explain this? https://twitter.com/JimBridenstine/status/1208020657583341569
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McTraveller

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Re: Science Thread (and !!SCIENCE!! Thread!)
« Reply #524 on: December 20, 2019, 10:09:11 am »

I can't think good today. Can someone explain this? https://twitter.com/JimBridenstine/status/1208020657583341569
Cynically: Boeing has lost its mojo.

Technically: Some kind of bug somewhere - more likely a sequence of errors starting with systematic process issues - caused an incorrect burn that meant the Starliner did not achieve its intended orbit.
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