Thank you for this cogent easy to understand answer for folks like myself.

Does Fe-54 conduct electricity in the same way as 56? Is it as magnetic? And do we find it commonly enough to build with it like we do with 56? (Last one I'm guessing is a big no and we may never know if we were using it in our materials.)

The issue here is that protons, neutrons, and their respective antiparticles are not elementary particles; they are made of quarks and antiquarks respectively bound together by gluons. A proton contains two up quarks and one down quark. An antineutron contains two down antiquarks and one up antiquark. A quark from the proton and an antiquark from the antineutron would annihilate and produce mesons from the remaining (anti)quarks, which would quickly decay.

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A neutron is made of up, down, down quarks, and a proton is made of up, up, down. An antineutron would be antiup, antidown, antidown, and the ups and antiups and the downs and antidowns would annihilate if it was in the same atom as a proton.

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Generally, neurons store neurotransmitters until it's time to fire. The neuron will then either wait for more supply, or in the case of dopamine neurons, synthesized inside the neuron itself. Without storing the oxytocin, there would be no way for the neuron to fire. It has to have one "in the chamber."

I think we don't have enough depth of data on even the best-known exoplanetary systems to really answer your question the way you mean it, but there are some things we do know, and some interesting comparisons and generalizations we can make because of that.

First off, a little cursory review of the data says it's actually 99.86% for our system, or only 14 parts out of 10,000 of the mass in the planets, not 2%. Of that 0.14%, around 70% is in Jupiter (and 20% in Saturn, and around 3-4% each in Neptune and Uranus).

That means ~98-99% of the mass outside the Sun is in the gas giants. THAT makes your question much more complicated, but also much more interesting!

The amount and composition of mass outside of the parent star, in a planetary system, is probably controlled mostly by what the protoplanetary nebula which the star and planets accreted/condensed from was like, very broadly. How dense the gas and dust was, what it was made of, how fast it was moving relative to other gas and dust and neighboring stars' stellar wind, the influence of shockwaves from supernovae, and so on. If you make cloud of matter dense enough, it makes new stellar systems, and what they come out like depends on what the cloud had in it and exactly how everything was arranged when it got nudged.

With that in mind, we can guess a lot about this from the star(s) that result by looking at the spectra of their light. Stars with more elements past Helium have a higher 'metallicity' (formal astrophysics term), which we can just measure from the gaps in the light wavelengths from the star. If there's more oxygen, nitrogen, carbon, silicon, iron, and heavier elements in a given stellar system, it's likely that it has more planets, period, but also more rocky planets.

Back to that 98% of the mass being in gas giants...well, if that's normal for a star the size, age, and metallicity of our Sun, there are a LOT of astronomical scenarios where metal-poor stars could have many gas planets, or a high-metallicity star could have had local orbital dynamics (in a binary/trinary stellar system) that meant no large planets could form at all, and ~100% of the mass in the system is in the star (or stars), or doing its own thing in some other object's gravitational influence after being flung away billions of years ago.

One important thing we don't know is how many planets are too small, too highly inclined in their orbits, too distant from their star, or otherwise undetectable by current methods in any given extraplanetary system. The thing is, if we're talking about 0.14% of the mass of the system, it could vary hugely and we wouldn't know from the effect on the parent stars. The wobble from Hot Jupiters face-hugging their parent red dwarf stars is teeny tiny. There might be planetary systems facing us flat-on with their ecliptic planes, too, among other things.

So, I guess that's a long way of saying 'it appears other planetary systems are similar to ours, but we have no way of knowing if that's because it's true, or because it just looks that way from the available data.'

All of that said, we're collecting an incredible quantity and quality of new data now, so a lot of this will be less...entirely based on physics simulations and extrapolating from what we can observe locally.

In addition to what u/ChromaticDragon already mentioned, if I recall correctly, it would in theory be possible to have an atomic nucleus comprised of protons and antineutrons. However, the protons consist of 3 quarks (uud) and the neutrons consist of 3 antiquarks (-udd).

=> The atom would not be very stable, as the quarks might interact and annihilate with the antiquarks.

"Sea levels been rising since the 60s, thats why the actual sea currents end on the same level and no island(looking at the one made for liberty statue) has maintain its sea level from its creation"

You can believe whatever you want at this point. Reality wont change because of it.

As far as i understand the question is
"Could you have a proton/anti-neutron/electron atom"

I thought antiparticles only annihilated with their respective particles? Could you not have a Hydrogen atom with one proton, one antineutron, and one electron?

You seem to be asking multiple questions. We may have to separate these to provide meaningful answers.

Since both neutrons and antineutrons both have neutral charge, can we distinguish between them?

Yes. The Wikipedia page has details and more in the referenced links. One difference is the magnetic moment.

Can antineutrons exist in the nuclei of regular atoms?

In the most general sense, no. A neutron and an antineutron would annihilate. So you cannot replace them one-by-one.

Could you have anti atoms with antineutrons, antiprotons and positrons?

Sure. Here's a good article on antimatter with some history of such. Trouble is that you have to keep it separated from regular matter which will annihilate it in short order.

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this is more likely the case, though more studies are needed to confirm it. i suspect this is essentially similar to the myth that eating lots of sugar/carbs can cause diabetes -- it is not generally correct, but it can apply to people who are genetically predisposed to diabetes.

You would be very hard pressed to tell the two isotopes apart.

The density of Fe-54 would be slightly lower; a mole of Fe-54 would have the same volume, but would weigh 4% less than a mole of Fe-56. The difference in density could have some secondary effects like relative diffusion rates, etc.

The chemistry of the two isotopes would be identical, except that some reactions of Fe-54 would be slightly faster (specifically where a covalent bond to the iron is being broken in the reaction's transition state).

Temperature is a statistical quantity that happens to be proportional to average energy in a system of particles following a Maxwell-Boltzmann distribution. However, it is not proportional to average energy by definition. If the gas has a non-zero average velocity in your frame it is not following an MB distribution, so it's temperature is not proportional to its average energy in your frame.

As a side note, you would observe blackbody radiation that was red- or blue-shifted depending on your motion that could make the gas appear warmer or cooler.

I’ll start by saying I’m not a physicist so I can’t say anything about relativistic effects, if that’s what you’re interesting.

In fluid mechanics we talk about “stagnation properties”. This can refer to a variety of fluid properties, commonly pressure and density, but most commonly temperature. Stagnation properties are defined as the value of a certain property when the fluid is brought to rest. For pressure and density this requires the fluid to be brought to rest isentropically (no entropy rise) and adiabatically (no heat addition or removal), but temperature only requires it to be adiabatic.

Using stagnation properties results in concepts of static and dynamic properties - the stagnation property is static + dynamic. A static property is the property that a fluid particle experiences when it is travelling at the same velocity as the fluid i.e. it is static relative to the fluids. For instance water in air will start to condense when the local static temperature and pressure fall to the dew point. A dynamic property is the component of the stagnation property due to the relative kinetic energy. This means that, yes, the temperature perceived by an object depends on the speed it is travelling at relative to the fluid. At high altitudes the temperature may be 230K, but an aircraft flying at high speeds experiences a stagnation temperature of maybe 260K (the exact value depends on the Mach number).

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There're some studies looking at the role of testosterone in anonymous social interactions (like one-shot trust games) but nothing I'm finding related to the winners effect in anonymous competitions, sadly.

I found those studies with a "testosterone+anonymous+competition" boolean search