1

Physics, Astronomy & Cosmology / Re: Do Certain Astronomical Phenomenons Affect US?

« on: 26/03/2021 12:32:18 »

The moon doesn't just pull on water, it pulls on everything! If you were to weigh yourself on a very precise scale, you might notice that you weigh ever so slightly less when the moon (and/or sun) is directly overhead (or directly under your feet!). I can't put any numbers on this since it depends on so many things (like your latitude and altitude, the relative positions of both the moon and sun), but thee effect is small.

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Geology, Palaeontology & Archaeology / Re: Sparkling rock with silver colored flakes

« on: 22/03/2021 16:12:25 »

Hard to tell from just the pics, but I'm pretty sure that the silver flakes are mica. The dark crystals could also potentially be garnet (again, it's hard to tell but based on the color, shape, and the other minerals present.)

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

« on: 03/03/2021 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.

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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!)

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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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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.

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Physics, Astronomy & Cosmology / Re: The most advanced space craft of the recent time that impressed you the most

« on: 06/01/2021 15:40:25 »

https://solarsystem.nasa.gov/missions/dawn/overview/

I would say the Dawn Probe. It uses an advanced ion thruster, allowing it to be the first (man-made) spacecraft to orbit multiple non-terrestrial bodies (Vesta and Ceres). This feat would not be possible (practical) using conventional chemical thrusters, which have too low of a specific impulse.

This mission also gathered reams of data regarding the composition and history of the asteroid belt. I don't think we're ready to be a space-faring civilization yet, but I think the first step along that way is likely to involve the asteroid belt (or one of the Martian moons), rather than colonization of our own moon or planetary bodies like Mars or Venus (ick!).

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

« on: 04/01/2021 16:13:33 »

From an electronic structure perspective, carbohydrates are essentially made only of sigma bonding and sigma antibonding orbitals (and some nonbonding orbitals, as lone pairs on oxygen). These are highly localized orbitals, and have very large energy gaps between occupied and unoccupied orbitals, so they will absorb very far into the UV, and are therefore colorless in the visible part of the spectrum.

As the carbohydrates decompose, many of the reactions involve eliminations to form water and pi bonds. The difference in energy between occupied and empty pi bonding and pi antibonding orbitals is much smaller (still well in the UV for single isolated pi bonds). As more water is eliminated, forming additional pi bonds, the molecules can start forming conjugated systems, where pi bonds extend over several atoms. This allows the energy levels to come still closer. At this point the color might start turning yellowish or brownish (think honey, syrup, molasses etc.) As the mixture continues to change, the light absorbed will also change, with growing conjugated systems absorbing longer and longer wavelengths, and more and more pi systems coming into being (so the a greater range and greater proportion of photons can be absorbed). Eventually, the mixture looks black because it absorbs essentially all visible light that lands on it!

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That CAN'T be true! / Re: I don’t understand physics: does anyone understand physics these days?

« on: 02/01/2021 16:26:21 »

@charles1948

I think the aspect of science that appears to be eluding you is that scientists, above all else, want to be right. Yes, I want the answer that I found to be the right one, because it is important to my ego and career to be the one who found it. But I would much rather use someone else's better answer than my own worse one!

Because of this, often scientists are their own most dogged critics. We test, and double test, and triple test. Concerned about false wiring? I'm sure the guy who did the wiring spent more time checking it than actually setting it up. And then come the control experiments!

The nifty thing about control experiments is that they very unambiguously allay "what if it's just ___" questions. Because you can set up thee experiment exactly the same way many times, and then verify that the results are X. Over and over and over: always X. Then you change something about the experiment, and the result is Y. Try it the first way again, X. New method? Y. Back and forth a few times, two experiments simultaneously in neighboring setups. Multiple experiments done on different parts of the planet! etc. If what you change about the experiment doesn't change the result, then you have "controlled for" that variable.

So a control experiment is not a guarantee that the experiment is valid, but it can guarantee that whatever factor is being "controlled for" is not causing the results (or it can identify that it is). We only say A causes B when we have ruled out C causes B, D causes B, C and D cause B... etc.

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Question of the Week / Re: QotW 20.12.21 - Can you get DNA from ashes?

« on: 21/12/2020 19:02:09 »

DNA should not survive cremation at all.

You might be able to get some information about mineral content, isotope ratios of non-volatile elements etc. but this is probably not going to be particularly useful for anything. One could imagine detecting the presence of metallic poisons (like arsenic, or thallium, etc.) even after cremation, but the dosage would need to be pretty high, and one would need to know what they're looking for...

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General Science / Re: Is Mathematics Falsified?

« on: 20/12/2020 21:05:30 »

There is no number that can be expressed in base 2, which also cannot be expressed in base 10. There are some inherent mathematical advantages to using base e, but really the only special thing about base 2 is that it is easiest to compute using base two and two-state 0/1 switches.

But there is no difference between any base when discussing infinity.

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General Science / Re: Is Mathematics Falsified?

« on: 11/12/2020 19:56:08 »

There is no shortage of apparent contradictions and paradoxes when dealing with infinity. Many times these can be resolved by making sure that the question and context are properly defined.

For instance, with no context, ∞ – ∞/2 is undefinable. But if we give some context, the answer can be defined in a way that is both meaningful and unambiguously provable to be true.

Imagine a farmer planting a row of seeds, and never stopping. There is a crow that follows behind him and eats the seeds at precisely half the rate that the farmer is planting them.

At any given finite value of time, there will be a non-zero number of seeds in the ground. But if we want to know what the "final" result is, we run into problems without knowing more.

If the crow eats every other seed (let's say it eats the odd ones: 1, 3, 5, 7, 9....), then there will be infinitely many seeds in the ground after infinite time passes, and we can say exactly where they will all be (holes 2, 4, 6, 8, 10....). For any hole, if you know whether it is even or odd, you will know whether there is a seed in it or not.

On the other hand, if the crow eats each seed in sequence (at half the rate that the farmer plants them), then there will be no seeds that can be found in the ground. How can I prove this? Pick a hole, any hole. Did the farmer put a seed in it? yes, at time = t. Did the crow eat the seed? yes, at time = 2t. So there are no holes that you can find a seed in.

Is this useful? It can be if you ask the right questions.

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Physiology & Medicine / Re: Novel treatment

« on: 08/12/2020 18:48:03 »

If said family member has a doctor already monitoring their condition, then this doctor would be the place to start. They would know how to verify improvement, and possibly what sort of side effects to look out for.

You. can also try a google scholar search for the condition, and. limit to articles published in the last 5 years. Contact info for the "corresponding author" is typically available, even if the content is behind as pay wall. Email them and ask.

Be aware that your results are likely to be falsified, or found to have other problems by serious study (most treatments are ultimately not FDA approvable, even those generated by teams of professionals).

Good luck!

15

Chemistry / Re: Can Sulphites be removed from wine other than by adding hydrogen peroxide?

« on: 02/10/2020 15:17:27 »

sulfites (sulphites) are unlikely to volatilize--you can get rid of them by oxidation, but why do you want to? They are protecting the wine by essentially serving as sacrificial reducing agents (oxygen in the air will react with sulfite before it oxidizes components of the wine)

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Physiology & Medicine / Re: Where are the major 5 senses inside a human brain?

« on: 10/09/2020 16:40:30 »

Clearly there are some ways of messing with how time is perceived (adrenaline and hallucinogens such as LSD being obvious examples of chemicals that can influence time perception), but I don't know if a person can be made to experience a day in an hour...

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Physiology & Medicine / Re: Where are the major 5 senses inside a human brain?

« on: 10/09/2020 16:37:56 »

It's hard to say precisely *where* a sense is located. But there are specific regions of the brain that are associated with processing the various senses at different levels.

Vision is processed first in the eye itself, and then signals are sent via the optic nerve to the visual cortex in the occipital lobe:
https://en.wikipedia.org/wiki/Optic_nerve
https://en.wikipedia.org/wiki/Visual_cortex
https://en.wikipedia.org/wiki/Occipital_lobe#Function
(one could imagine hacking in at any point in this process)

For touch, you might be interested in the cortical homunculus:
https://en.wikipedia.org/wiki/Cortical_homunculus

There are also structures known for processing sound, smell, and other senses.

As far as putting our own signals in, I think there is some work that has been done using implanted electrodes (fairly crude), as well as use of microwaves, which can apparently cause people to perceive sounds.
https://onlinelibrary.wiley.com/doi/pdf/10.1002/bem.10163

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Physics, Astronomy & Cosmology / Re: Does spacetime bend only locally around objects?

« on: 20/08/2020 15:30:17 »

Great answer from Colin2B!

I will also add: we can detect gravitational waves from stellar (black hole and neutron star) collisions from billions of light years away!! It takes the most sensitive instruments on the planet to detect the motions of the most massive bodies in the universe—but it clearly demonstrates that massive bodies can distort space (space-time) across cosmic distances.

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COVID-19 / Re: Could asymptomatic people have invisible organ damage?

« on: 04/08/2020 19:37:57 »

My understanding is that this may be possible. "asymptomatic" unfortunately doesn't strictly mean "no symptoms of the disease occurred," it means "no symptoms of the disease were recognized."

It took many weeks before people realized that "asymptomatic" individuals could be diagnosed by looking for loss of smell/taste, or "covid toes." (new symptoms were discovered)

There are anecdotes of individuals who are (otherwise) "asymptomatic," but developed blot clots, which then caused stroke. So I would imagine that there could be cases of individuals who are infected, don't present the "standard" fever/cough/malaise but could still sustain significant damage to liver or kidneys or what have you...

There is still so much we don't understand about this disease...

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Physics, Astronomy & Cosmology / Re: How Do We Know Absolute Zero Is The Temperature It Is If It's Unattainable ?

« on: 02/08/2020 13:17:33 »

Extrapolation!

If you put a gas in a sealed piston (which will keep the internal pressure constant by allowing the volume to change), and start cooling it down (and/or heating it up) you will notice that the volume varies with temperature. After collection of much data it will become apparent that the volume is proportional to temperature, but only if you use a really odd temperature scale, that has a zero point at –273.15 °C.

There are other ways to get there, but I believe that historically, this is how it came about.