I've done r&d with materials in a similar situation. One problem is surface leakage paths. You can't just think of the cap as a simple component anymore. The case, mounting, humidity, vibration, etc can cause a sudden short circuit. Literally breathing on the circuit could cause it to explode. So now you have to can it in transformer oil or similar. That's got its own set of headaches.

Hey that's a good point!

Isotopes are nuclides with the same number of protons. C-12,. C-13, C-14 are on the "6 proton isotope". Isotones are nuclides that have the same number of neutrons. H-3 and He-4 are on the n=2 isotone. Similar to how places at the same atmospheric pressure are on an isobaric line.

Weirdly, "isobar" is also a term in nuclear physics where it means same number of total neutron plus protons. I think it comes from from "baryon" whereas in meteorology it comes from "barometer"

That's mostly correct. You can't breed Pu-239 without also breeding a little Pu-240, and you basically can't get it out of the Pu-239. Pu-240 has a very high spontaneous fission rate (atoms occasionally just fall apart, often releasing a neutron or two). At the levels present in a few kilograms of Pu, there's a random neutron every microsecond or so.

For a gun-type design, it spends a fraction of a millisecond in a configuration where a chain reaction is possible but generates a dud. And the Pu-240 spontaneous fission makes it very likely that such a dud chain reaction will happen.

the explosive lens is a "lens" in the sense that it can focus shock waves. To compress a sphere into a tiny ball, you have to have continuous equal pressure over the whole surface or else it will deform and splash into a complicated shape.

You cover the plutonium sphere with an shell of explosives (or a shell of some dense metal that is then covered with a shell of explosives.) If you start to detonate the explosive shell using a detonator at one location, the shock wave will hit the plutonium directly under that location first, starting a dimple. The plutonium on the other side isn't being compressed because the explosive there hasn't started to explode because the shock wave hasn't arrived yet.

So you use a bunch of detonators all over the surface. That's better, but it still creates an uneven pattern of pressure -- now maybe you get 20 or 60 dimples forming symmetrically but it's still not going to result in a compressed ball. There will always be locations on the surface of the plutonium where the shock wave is pressing the material sideways instead of inward.

The explosive lens uses two materials with two different speeds at which the shock wave can travel. The shock wave directly under the detonator is going through the slow stuff but the shock wave spreading sideways from the detonator is going through the fast stuff. If you shape these in the right pattern, using curved interfaces, the effect is just like light passing through a curved lens. The shock waves are bent into a pattern that is almost equal pressure everywhere at the surface of the plutonium.

There is almost no difference between how a Pu vs U fission bomb works. There are several minor differences in their chemical and nuclear properties that affect the engineering details.

The explosion in both cases is not chemical but nuclear. A lot of regular chemical explosives are used to suddenly change the shape of the plutonium or uranium mass in such a way that it goes from being a shape that absolutely can't generate a nuclear explosion to a shape that easily can. And then a tiny particle accelerator (basically similar to a Tesla coil but about the size of your finger) turns on and sprays the new shape with a bunch of neutrons which kick-start the nuclear reaction. The timing is important because it's in the ideal shape for less than a thousandth of a second.

The particle accelerator acts just like a spark plug in a car's engine. A car engine that uses gasoline (petrol) has a mix of gasoline and air inside a cylinder. That mix changes shape (the cylinder compresses it) and when it's at just the right shape, the spark plug ignites the mix.

But think about a diesel engine. Those don't have spark plugs. The mix is compressed down so much that it ignites itself. That can also happen in a gasoline engine if the fuel is bad or the design is wrong -- the mix can ignite before the spark plug fires. Similarly, the only key difference between Pu and U bombs is that Pu has a high possibility of accidentally starting the nuclear explosion a bit early, before it's at the ideal shape (and without needing the particle accelerator).

As a result, you can't use the simplest engineering design with plutonium. You can make a uranium bomb where the starting shape is a rod and a hollow cylinder and use an explosive to shoot the rod into the cylinder. Then the particle accelerator is turned on right when the rod is perfectly lined up with the cylinder. But if you try this with plutonium, there's a really high chance that before the rod gets lined up, the nuclear reactions start in the plutonium. The nuclear reactions are so fast that basically the plutonium rod melts and expands into a blob and hits the cylinder instead of sliding right into the center. It's still a nuclear explosion, but it's a dud because instead of getting the equivalent of thousands of tons of TNT explosive power, it only generates maybe the same as a few tons of TNT before it shatters and stops the nuclear reaction. So for plutonium you have to use a much harder to engineer design where it starts as a large hollow sphere and the explosives compress it into a small solid ball.

Someone who believes in flat earth is denying dozens of obvious sources of proof. It's difficult to guess what is "best" for arguing with a person in that state of mind.

For a gas like air, temperature is related to the spread in molecular velocities, not the average molecular velocity.

Wind feels cool due to convective heat transfer. In still air, your skin loses heat to the air a millimeter away, but that air is now a bit hotter itself, and it can transfer heat back to you. In a breeze, the air next to your skin is constantly replaced with new air at the average temperature of your environment. This is also why clothing keeps you warm-- it creates a barrier between the air next to your body and the air in the environment so they don't mix.

If 3 freshman tried and then quit, that tells me there were another 3 sophs, 3 juniors, and 2 seniors that didn't even give it a shot. That's kind of telling.

Article says she was working in an office near the lab, not necessarily working on the smallpox research

One possibility is a blunder where two identical samples generate different results. Lab A didn't follow protocol, or a reagent was a bit old, or a power glitch or similar. This is independent of whether they are using the same method, same loci, etc.

This type of error is common enough that there are special checks routinely included. This might be a "standard" sample run in the same batch. They know what result the standard is supposed to have so if it's wrong then your sample may also be wrong.

Of course that doesn't fix a different kind of blunder where your sample got mislabelled or switched, or spoiled while in shipping. Those get checked by blind "traveller" standards. That's where occasionally the lab QA person mails a standard in labelled just like a normal sample. It's not a perfect check because it just detects sloppy handling of the traveller, not sloppy handling of your sample. But it does serve to weed out systematic problems

Another possibility is a random match or mismatch. If a given loci is expected to be present in, say, 50% of the population, and there's no correlation between loci, then the chance that two different sources match at 23 loci (but not the 24th). is around 1/2^24,. Which is one in about 16 million.

Before everybody gets too emotionally invested in this story, I suggest we hear from the 3 freshman who all mysteriously quit "for personal reasons". And maybe also all the sophomores, juniors, and senior girls who didn't even want to give cheerleading a try. Doesn't that sound a little odd to you?

If you're going to make negative assumptions about teenage girls, consider the possibility that this girl and/or the coach might be so nasty that the others weren't enjoying the experience.

A bit suspicious that not a single other senior, junior, or sophomore was willing to be a cheerleader. Only 3 freshman who maybe thought it would be fun and then noped out.

I am not a biologist, so take my answer with a grain of salt. I wouldn't respond except that your post is getting stale and I don't see anyone addressing the core question. Mods feel free to Dunning-Krueger my comment into oblivion if somebody else gives a more cogent answer to OP.

The question of "can" is easy to answer: Given funding, we can find some biological molecule that fluoresces at any wavelength you want between about 350nm and a few thousand nm. (human sight is about 400 - 700nm) Below about 350 is hard because it takes a lot of energy to generate.

The question of evolutionary fitness is more interesting. Evolutionary adaptation does not "seek new solutions". Rather, some random adaptation is evolved, and if it is advantageous it has a chance to become widespread. The advantage of bioluminescence is beyond my training, but I assume (perhaps wrongly) that it provides some competitive advantage in hunting/attracting mates/whatever.

Two factors are worth considering now:

1. How likely is it that an organism mutate to produce a bioluminescent protein at wavelength "X".

2. How advantageous / disadvantageous is that mutation?

To point (1) it is likely that some luminescent proteins are just one or two mutations away from some other protein that is common. These mutations are likely to occur more frequently than others, and are therefore more likely to catch hold if there is some competitive advantage to bioluminescence.

To point (2) if a luminescent protein is easy to achieve by mutation but is very energy intensive or poisonous or whatever, it is less likely to produce a net competitive advantage.

In some population, if two different mutations can occur, one being a low-cost protein at wavelength "X" and the other being a high-cost protein at wavelength "Y" I would expect the former to take hold in the population. And once the capability to luminesce at wavelength "X" is evolved, it becomes much less likely that a capability to luminesce at wavelength "Y" subsequently evolve. The organism already has a means of luring food/attracting mates/whatever. A mutation that produces another (more costly) method is a competitive disadvantage in most scenarios, unless there's a "Red Queen" situation where the organism is under a lot of pressure to evolve new capabilities due to competing evolution of a predator or similar.

Why blue-green for aquatic and red-yellow for terrestrial? The attenuation of light in sea water is wavelength dependent. Blue-Green propagates better than red or blue. That color is called "Aqua" for a reason. UV is rapidly attenuated. Presumably, then, a mutation for bioluminescence in the UV or IR provides little or no benefit. For terrestrial, red and infrared propagate just fine through air and are less energy-costly than blue or green. I have no idea if there's a lot of infrared bioluminescence, but I wouldn't be surprised.

Not an historian.

Lux, Belgium, Netherlands, Denmark basically never stood a chance against Germany. Small countries with small armies. No room to trade space for time.

In 1939, France arguably had a larger and better equipped army than Germany (for instance, the French armor was estimated to be superior to German armor at the time) , but the French army collapsed due in large part to poor generalship and and to a lesser extent poor morale.

By the way, this is exactly how submarines used to change depth (Modern subs tend to use a different method). They have sections that can be filled with water or air, and tanks of compressed air. If they need to come up quickly, they let some of the compressed air into those sections, pushing out the water. This is like your syringe example.

A modern sub is more likely to use that process to get almost exactly zero buoyancy, and then change depth by pointing a bit up or down while running the propeller.

Step 1 is to measure the mass of the planet. This is surprisingly easy. Just need to catch a view of some object in orbit around the planet (like a moon) or passing near the planet (like a comet). If you can a couple of good observations, preferable over several weeks, you can calculate the mass of the planet using newton's laws of motion.

Step 2 is to get a measurement of the diameter of the planet. This is surprisingly hard. I don't recall the methods used. One problem is "what's the definition of the diameter when you're looking at a gas giant? It basically goes from a solid core to a vet thick liquid transitioning to extreme pressure gas. Then the gas pressure, density drop off slowly to zero.

If you know the mass and diameter, it's a simple calculation.

But if you want the gravity of a gas giant at some point down inside the thick atmosphere, you do have to also figure out how much mass is inside your chosen depth.

Sonar is like flash photography in a dark room.

When it is activated, everyone knows where the flash is. But also everyone can briefly see everyone else in the reflections