1

Technology / Re: Is there a device to freeze my drink asap?

« on: Today at 01:44:30 »

Yes, it is almost always easier to heat something up than cool it down (and it's because of thermodynamics, and what we can do to accomplish each).

Essentially the only way to cool something down is to move its thermal heat elsewhere. The efficiency at which this can be done depends on the temperature of the thing that's getting cooled down, and the temperature of whatever is accepting the thermal energy. (It is spontaneous and really efficient if the object losing heat is much hotter than the heat sink, and the efficiency drops off as they get closer in temperature. Once the source of the thermal energy is colder than the sink, the process is non-spontaneous and requires input of energy (refrigeration). And in this regime, the larger the difference in temperature, the more applied energy is required to move the same amount of thermal energy "the wrong way".

When heating an object up, we can do it by heat transfer (and the same rules apply: it is easy to move heat from hot to cold, not the other way). Or we can transform non-thermal energy into thermal energy (it is much harder to go the other way). One can easily and rapidly generate arbitrarily large amounts of heat in arbitrarily small spaces by delivering electrical energy (think of a light bulb filament that goes from 300 K to 3000 K in the blink of an eye), or chemical energy (like a blowtorch or a combustion engine), or even light energy (concentrated laser light or sunlight can deliver millions of watts per square meter, and instantaneously turn any matter in the focus into a superheated plasma).

Unfortunately there really isn't any good way to have an object at any reasonable temperature cool down significantly by emitting intense light.

2

Chemistry / Re: Is there hydrogen in space?

« on: 01/03/2021 15:15:04 »

Yes, lot's of it. Hydrogen is by far the most abundant element in the universe, accounting for about 90% of the atoms in the observable universe (if I remember correctly). That said, most of the hydrogen is clumped up into stars and gas giants, and is otherwise *very* diffuse. I think something on the order of 1 or 2 atoms per cubic meter in deep space. So there is lots of hydrogen, but so much more space.

(and if your plan is to use the hydrogen as fuel, you'll need to find some oxygen too, and that's gonna be tough!)

3

Physiology & Medicine / Re: Does chocolate usually make people sick after a few bites?

« on: 23/02/2021 00:46:03 »

Somehow I doubt that milk chocolate bars made by amateur children are the pinnacle of quality, but I am assuming it did not make you physically ill?

I have been known to finish an entire bar of chocolate (about 100g) by myself in one sitting, but am usually satisfied by smaller amounts of especially rich or especially sweet chocolate (my preference is dark chocolate in the 65–75% cacao solids range). I would have to consume quite a bit to feel sickened by it, but it can be quite filling!

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Physics, Astronomy & Cosmology / Re: The explanation of the darkness of the sky to the space between Earth and Moon

« on: 09/02/2021 15:23:39 »

You perceive something as bright when it reflects or transmits visible light towards your eyes. In space there is nothing to reflect light towards your eyes (unlike the atmosphere where there is air, dust, etc) so sunlight passes through without interacting.

exactly

5

The Environment / Re: How come the ice core temperature curve always leads the CO2 curve?

« on: 30/01/2021 15:56:57 »

Alan, let's say that your interpretation of the ice core data is absolutely correct. What does your model predict would happen if the concentration of CO₂ were to suddenly (geologically speaking) increase more than 40% higher than it was at any other local maximum on the ice core data? (as it has)

Is it reasonable to assume that the mechanism responsible for the slow return to baseline after the smaller CO₂ spikes will be able to reverse the current level and trend? I don't think that previous returns to normal are necessarily good predictors of future behavior given how significantly we have deviated from the previous data.

Also, if I understand correctly, you accept that increased CO₂ in the atmosphere will lead to buildup of thermal energy, just not an increase in temperature? (how I interpreted your multiple references to heat capacity and latent heat of water). Ok, let's say the temp doesn't increase at all. Where does the energy go? What does that mean for the climate?

6

General Science / Re: Can you derive x = -1 from x^2 = 1?

« on: 29/01/2021 19:21:50 »

x² = 1
x² – 1 = 0
(x+1)(x–1) = 0
x = 1 and x = –1 both satisfy the last equation

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Plant Sciences, Zoology & Evolution / Re: Could you create artificial bee pheromones?

« on: 28/01/2021 22:05:15 »

Yes.

Pheromones are composed of small (often simple) molecules (they need to be small to be adequately distributed in the air), so they can be made in a lab. The molecules made in a lab are identical to the ones made by insects (though if the insect is creating a mixture of different molecules, it could be hard to replicate the precise mixture).

There was a chemistry group at the university I attended for undergraduate that had supposedly used a caged moth as a detector for the gas chromatograph they used for isolating and identifying moth pheromones. (they would inject an extract of the female moth onto the column, which would then separate the compounds as they passed through, letting them out one at a time. When the male moth went berserk, they knew that the compound coming off at that instant was a compound of interest.) I imagine similar techniques could be used for bees.

Yes, instead of relying on bees to fertilise plants, couldn't we just spray the plants with pheromones extracted from bees.  The pheromones would have been analysed. Then chemically reproduced on a massive industrial scale.

The bees wouldn't be needed any more.

No. I think we may need to have a talk about the birds and the bees...

Bee pheromones have no direct role in plant fertilization (allowing bees to communicate with each other could be considered an indirect role). Bees and other pollinators (flies, butterflies, birds, bats, etc.) get covered in pollen while they extract nectar from the flower. The pollen contains plant gametes, which can then be transferred to another flower by the pollen-laden bee, and from there the gametes can fertilize the flower. (roughly) you should look that up!

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Physics, Astronomy & Cosmology / Re: Which weighs more, a litre of ice or a litre of water?

« on: 28/01/2021 02:35:37 »

Isn't 1kg of iron=1 kg of wool?

yes, but liters (volume) ≠ kg (mass)

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Plant Sciences, Zoology & Evolution / Re: Could you create artificial bee pheromones?

« on: 27/01/2021 17:07:04 »

Yes.

Pheromones are composed of small (often simple) molecules (they need to be small to be adequately distributed in the air), so they can be made in a lab. The molecules made in a lab are identical to the ones made by insects (though if the insect is creating a mixture of different molecules, it could be hard to replicate the precise mixture).

There was a chemistry group at the university I attended for undergraduate that had supposedly used a caged moth as a detector for the gas chromatograph they used for isolating and identifying moth pheromones. (they would inject an extract of the female moth onto the column, which would then separate the compounds as they passed through, letting them out one at a time. When the male moth went berserk, they knew that the compound coming off at that instant was a compound of interest.) I imagine similar techniques could be used for bees.

10

The Environment / Re: How come the ice core temperature curve always leads the CO2 curve?

« on: 27/01/2021 03:21:12 »

Here's an interesting spectrum

https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg

The difference between the "space" spectrum and the "sea level" spectrum is massively dominated by the absorption of water, with CO2 very much an afterthought in the tail.

But don't let the facts spoil a profitable hypothesis.

Exactly! The water part of the spectrum is saturated. That's why changes in water concentration don't have as significant an effect. On the other hand, where CO₂ absorbs, the spectrum is NOT yet saturated, and therefore will be related to concentration. Also, I see these spectra are overlaid with the blackbody radiation of incoming solar radiation. I would highly recommend comparing to the blackbody spectrum of the earth too. You will find that the frequencies of IR that interact strongly with CO₂ make up a very small portion of the incoming energy, and a significant portion of the outgoing.

outgoing.png (162.06 kB . 700x348 - viewed 510 times)

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Physics, Astronomy & Cosmology / Re: What is the actual explanation of the gyroscopic effect?

« on: 26/01/2021 16:01:04 »

And I have patented dozens of chemical compounds that have never been made (some of which I know cannot be stable, but they're still mine, all mine!) The fact that they are patented doesn't mean that these compounds are "real."

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Physics, Astronomy & Cosmology / Re: What is the actual explanation of the gyroscopic effect?

« on: 26/01/2021 15:05:18 »

Have you spun up any flywheels while sitting in a chair that is free to rotate? You may find that "equal and opposite" (conservation of angular momentum) still applies here.

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The Environment / Re: How come the ice core temperature curve always leads the CO2 curve?

« on: 26/01/2021 08:58:46 »

Of course any gas increases warming

Can you explain the mechanisms for argon, oxygen and nitrogen please.

I saw that as well.

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The Environment / Re: How come the ice core temperature curve always leads the CO2 curve?

« on: 26/01/2021 08:58:11 »

Ok Alan, let's say that you are correct that temperatures have increased before atmospheric CO₂ levels over the course of history before the 1800s. This would make some sense, because we know of several mechanisms by which warmer climates would lead to more CO₂ in the atmosphere (greater temperatures lead to decreased solubility in water, increased rate of wildfires, etc.).

The problem is that this historical data might not be a valid model for the last 250 years or so. If I understand correctly, for most of the history of our ice cores, nobody was excavating or extracting fossil fuels from deep below the surface, and burning them, at a rate of tens of billions of tons (10¹³ kg) of CO₂ per year. It seems quite possible to me that this is unprecedented, and could be a significant departure from historical data.

15

Plant Sciences, Zoology & Evolution / Re: Why is compost black?

« on: 25/01/2021 02:00:26 »

According to compostjunkie, "It is stated that due to anaerobic conditions, ammonia and hydrogen sulfide are produced which leaves a black residue in the compost." And compost is not always black.

Then it appears that compostjunkie is wrong (or the quote is missing something important). Neither ammonia nor hydrogen sulfide absorbs visible light significantly (so are colorless themselves). Additionally, they are both gasses which are unlikely to be found in the compost. The chemical reactions that release these two may also produce some dark residue, but I doubt that this is the dominant pathway, because the compounds that could decompose to produce ammonia and hydrogen sulfide (mostly amino acids and nucleic acids) are in much, much, smaller quantities than the compounds that produce humins (cellulose, starch, and other sugars).

16

That CAN'T be true! / Re: Appeals to a scientific majority....

« on: 21/01/2021 17:01:51 »

Still the public should maybe become slightly more literate with regards to science.

Absolutely! It might not be possible for a "citizen scientist" to figure out which group of experts is correct, if there is a disagreement among experts. But even just a mite of scientific literacy can allow one to identify scammers and quacks.

17

That CAN'T be true! / Re: Appeals to a scientific majority....

« on: 21/01/2021 16:54:30 »

Evidence and proof are often only useful *among* experts. I can tell my colleague, "no this sample isn't the right compound: notice that the coupling constants for these peaks are too small, and the chemical shifts for all the peaks are a little too far downfield."

This argument may satisfy my colleague, or they may be able to point out, "no, it's still the right stuff, I just have the sample in a different solvent, so the peaks are a little different from what you're expecting."

If we were to debate further, we would be able to go into great detail and possibly even do a quick experimental check (ie compare to an authentic standard in both solvents). But if my colleague and I were each trying to convince an audience of non-experts of our own conclusions, one might have to resort to saying, "one of my colleagues believe this is the wrong substance, but these 29 other experts all agree that the first expert is mistaken because they are not accounting for subtle solvent effects."

Both sides of experts can provide reams of data and detailed analyses, but ultimately how can the non-expert decide what is legit and what isn't? (it's not trivial). Relying on consensus of experts may be their bast choice. If 29 experts say one thing, and 1 says another, the 1 is usually (but not always) wrong.

18

Physiology & Medicine / Re: Is angry sex dangerous?

« on: 21/01/2021 04:56:58 »

Probably safer than angry driving...

19

Physics, Astronomy & Cosmology / Re: Is this the answer to building a space elevator?

« on: 19/01/2021 20:56:36 »

Also, quick question:

Why don't charged clouds in thunderstorms ever launch anything into space?

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Physics, Astronomy & Cosmology / Re: Is this the answer to building a space elevator?

« on: 19/01/2021 20:55:48 »

The equation is
E= Sigma/2e      Newtons/coulomb..Note that distance is NOT a factor

distance is not a factor when an infinite plane is used, and this equation is still a reasonable approximation when the distance from the plate is much smaller than the size of the plate. If you want 100 km to be much smaller than the plate, be prepared for an expensive project!