Yeah there would have to be a range of tests with different container shapes and materials, ice cube size and shape, ice composition and density, ambient temperature and humidity, air flow, water flow, a bunch of stuff would have impacts

Geez you should be an astrophysicist ;) this is an excellent breakdown, do you have any articles or papers you recommend (or published) on the early universe that focus on expansion history and the emergence of cosmic structures?

Ahhh, okay. I remembered the 1.5 inches per year but in the wrong direction-- I think i mixed up decaying orbits / Lagrange points for closer satellites that are impacted by atmospheric friction. I had forgotten that the weird phenomena of rotation and tidal gravitational forces combine to speed up the moon's orbit, functionally the same thing as escaping. And yes, explode was a convenient fill in word for "expand into a red giant, assimilating most of the inner bodies in the solar system, then shed the outer layers in a not-quite-explosion, leaving a white dwarf core", but you're right, that's incomplete

I've seen some other stuff recently that suggests the other inner planets like Mars and Mercury have slightly unexpected composition, like Earth and the moon. This has led to speculation that there was potentially a "billiard ball era" where chunks of protoplanets were smashing into each other, distributing heavier elements more evenly across the inner planets, and explaining the traces here and there that don't line up with Theia. A rogue body like a pluto- sized comet passing through and impacting one protoplanetary mass could lead to a whole series of impacts. There's still a ton of theories about the asteroid belt, and a bunch of new studies on the composition of the larger bodies in it. Exciting stuff!

The moon is actually really, really close in cosmic terms for a moon of its size relative to earth. Saturn and Jupiter's moons are much smaller AND much farther away. and it is in fact slowing down veeeeeeeeery marginally over time, so if the sun didn't explode eventually it might make it back to earth

Aha! I knew there was some trick. It's that it should be relatively easy to just take raw lithium or even possibly recycle lithium batteries and cheaply achieve the isotope ratios you want for tritium breeding (but the byproduct of the breeding process isnt leftover lithium). Thanks!

Can't you also dope/enrich lithium back up to 7 relatively cheaply? Thought I read that somewhere too

A ton of tritium would also go a pretty long way for the cost of the exchange

I think the idea of the extreme accelerations is that you could use something like a nuclear bomb to clear the first few stages of accelerating and then your onboard fuel supply doesn't have to work as hard, but I think there are more reasons than the G forces why that wouldn't work either. We don't have the tech for much more than 1g of sustained thrust anyway, like you said. These kinds of thought experiments are the very definition of speculative lol

And we all know being hooked up to a specialized ventilator for extremely long periods is perfectly healthy and fine

To paraphrase something someone said elsewhere in here, it would allow humans to achieve ludicrous relative accelerations compared to normal human expectations, but that would still be extremely negligible acceleration compared with trying to achieve relativistic speeds

And as a third person said, the cost of transporting and manufacturing this fluid would probably significantly outweigh any gains

I did way too much thinking about this today lol

It would be a super small amount of heating unless the acceleration was relativistic, so negligible

The separation effect of the acceleration (centrifuge forces) would also be pretty small at all but very high accelerations

And the amount of damage caused by the acceleration would be a lot smaller without any gas at all-- BUT gas is a byproduct of a large number of our body processes like oxygen uptake, AND that acceleration would still have a meaningful effect on your body's different systems. You would still die of a stroke at pretty small accelerations

Edit: also good call! I totally forgot about the latent heat of vaporization thing being the primary factor

The fluids in a person's body have different densities at a given pressure

It would be like putting you in a centrifuge, some of your parts like your bones would have different buoyancy than others and would experience pressure to separate out

It would be significantly less pressure than other forces acting on you and it might be too small to overcome the forces your body exerts

Only if the persons density changed at the same rate as the water. Our body would be pushing outwards to maintain a lower internal pressure, making us more buoyant

Makes me think of another question, would the pressure change or the marginally increased g forces kill you first in this experiment

Edit: Another hilarious question... would the water heat up? Increasing pressure rapidly in an incompressible liquid produces heating, see: refrigeration

Would you scald to death, die of a stroke when your gas-free blood still pools in the back of your skull, or die of internal pressure gradient because your cells stop working and burst

I think this, they would actually float 'up' in the direction of acceleration if there was a difference in density between the person and the water, because as the water experiences differential pressure the body might be able to maintain internal pressures. However, when the lowest pressure at any point in the tank is above a lethal amount it would still kill you. So at mega high accelerations you aren't safe even in a very large but not infinite tank

Edit: I think this is right. The acceleration of hitting the ground only kills you because it causes forces to act across your body unevenly very rapidly, g forces from acceleration work the same way. So if you don't implode from the pressure, you're still experiencing an acceleration difference across different parts of your body inhomogeneously because the actual thing keeping you intact in the water is your skin. You would still die of g forces suspended in a liquid

Precisely- we have really good models for "natural" dynamics like predator introduction that should result in extinctions from predation pressure. And there are lots of examples of that happening due to direct human interference or climate change. But it's probably not broadly possible to produce an example like what OP might be looking for, since any extinctions observed by modern science are influenced by human activities at every level

Those three species alone are responsible for like half the extinctions in the last 400 years

You could make a good argument that aurochs went extinct due to "predatjon" before the modern era. Humans and other large predators like wolves heavily depended on them for food, and as the climate changed and predator populations boomed, macrofauna couldn't reproduce fast enough to survive. Humans got ahead of the crisis by domesticating oxen right as the last herds disappeared

It's really hard to categorize "why" and "how" a species went extinct if we don't have direct observation, so we really only have that kind of understanding of much more modern extinctions. Even for the dinosaurs, we know a) a space rock of some kind hit. B) the climate changed drastically overnight, and we can measure the effect on plants and the atmosphere. And c) the dinosaurs mostly died off. While we can theorize and use good techniques to analyze the evidence we have, we simply cannot know if the last brontosaurus was eaten to death or starved

And it's a principle because while it's handy and you can use it to make correct assumptions about the universe, it's also sort of fundamentally unprovable

Gödel is one of my all time faves lol

Well no. If we had no other ways of determining the mass of the sun, then maybe. But we can do gravitational lensing measurements and things, and the whole eclipse thing, and fusion doesn't happen at earth sized masses, etc etc etc. There are many ways to determine that the sun is millions of times the size of earth, and that the system is spinning, and put both together and we are orbiting the sun

We can actually use the doppler effect on nearby stars to determine how fast they are rotating! The light from one half of the star is bluer than the other because part of the surface of the star is rotating towards us, and part away! Add up the difference in frequency (and do math), that tells you the difference in their speeds, half of that is how fast it's rotating! This is also handy when determining things like a star's absolute color and luminosity, as its spectrum can appear shifted or blurry if the star is rotating very fast or at a funny angle

Can't all sublight paths through a relativistic spacetime be characterized as orbits? Even in intergalactic space objects' paths are curved by gravity. There would still be slight angular accelerations on basically any "straight" path even if they even out over time

Any hypothetical measurements of acceleration would be skewed by miniscule differences in things like local gravity and additional undetected rotations, so it would be hard to pinpoint why they don't match up

Both things put together

It's highly unlikely that normal people in a non-controlled setting will ever get fMRIs at the rate needed for this kind of thing, because insurance isn't covering it, research grants of the scale needed would be wildly expensive, and average people aren't paying tens of thousands for a brain scan for funsies

Unless the tech changes there would need to be another route

Also, plants and algae are mostly limited ecologically by direct proximal competition for light and other static resources, and half of them being gone randomly presumably just means literally twice as much room to grow in the next generation-- which could be a matter of months. Trees are harder to replace etc., but not impossible