True. My personal answer to this is that I consider a "person" to be the processes that occur in the brain from which consciousness arises via some mechanism that is not yet well-understood, with the body more or less just being a vessel for those processes to occur in and for the consciousness to interact with the world.

And so my personal opinion is that the only real use for keeping a braindead body alive would be to keep its organs viable until transplantation, but I do understand that that is probably an opinion that is quite far to the materialist side of things.

For a certain definition of "living", at any rate. His body was kept functioning, but there wasn't really a person living in it anymore.

We just don't know. There are no facilities that can produce extended hypogravity to study those longer-term effects. Honestly I think that would be as good a reason as any to construct a spin-gravity space station capable of up to 1 g: Conduct a study to see how much gravity is required for humans to stay healthy. Because if we are going to make permanent settlements on the Moon or on Mars, I think we should probably figure out beforehand if a third or a sixth of Earth's gravity is enough for humans.

If Venus were cooled to a sufficiently cold temperature (to achieve that, most of the sunlight that hits it would need to be blocked), most of its supercritical CO2 atmosphere would condense out into an ocean of liquid CO2, that would then freeze over into a crust of dry ice hundreds of meters thick.

There is also the problem of atmospheric seeing, which uncorrected limits the resolution to about 1 km at the distance of the Moon with excellent seeing conditions.

> When chlorine is present in a chemical being sampled for instance, since 76% of the time the chlorine atom will be 35Cl and 24% of the time it will be 37Cl, this will show up as very characteristic pairs of peaks in a 3:1 ratio, 2 mass units apart in all chlorine containing fragments in the Mass Spectrum.

Though that would only be for fragments containing a single chlorine atom each, right? Something with two or three chlorine atoms in one fragment should show a much more complex pattern, since each chlorine atom can either be 35Cl or 37Cl.

In a wood fire (and also similarly in a candle flame, or the flame of a simple lighter, or a bunsen burner with the air valve closed, number 1), because the air has to flow into the flame from the outside, there is not enough oxygen in the flame to burn all of the fuel.

Because the fuel in all of these cases is a carbon-based material, one of the products of this incomplete combustion is just... leftover solid carbon, which forms into tiny particles of soot. And because these tiny particles are in a hot flame, they are also hot, and so glow a bright yellow.

On the other hand, in a gas burner for heating, or a bunsen burner with the air valve open, the gas is mixed with air before it enters the flame. That way, there is enough oxygen available to quickly react all of the carbon and hydrogen in the fuel to carbon dioxide and water (this is what is meant by "complete combustion), so there is no soot that can glow, and you get both a hotter flame, and also more heat per each unit of fuel.

A recent simulation suggests one possible way is that the impact debris initially coalesced into two bodies. One of those did indeed fall back into Earth, but the other one, due to momentum exchange with the first one, got enough momentum to get a stable orbit. And from there, tidal interactions slowly transferred momentum from the Earth's rotation to the Moon's orbit, widening its orbit and slowing down the rotation.

Well, you would need a quite large inventory of lithium in the reactor to capture a large fraction of the neutrons, but it would only be consumed at a slow rate. Even assuming only 20% of the fusion power comes out as net electricity output (the rest being either lost as waste heat or needed to keep the fusion going), a 1 GW D-T fusion power plant would consume only about 275 kg of tritium per year, which would correspond to a lithium consumption of about 600 kg per year, depending on the specific mix of lithium isotopes.

Those processes are how a D-T fusion plant would capture energy. About 80% of the energy output of D-T fusion is in the neutron, and the other 20% are probably required to keep the plasma hot anyways. As the neutrons slow down and go through nuclear reactions in the breeding blanket, they will give up their kinetic energy as heat, which can then be used to boil water and drive a steam turbine.

The speed of sound in water is nearly five times as fast as in air, about 1500 m/s. An object moving that fast through water would experience a dynamic pressure of about 1.1 GPa, compared to about 70 kPa for something moving at the speed of sound through sea-level air - in other words, not really possible outside of extreme scenarios like meteorite impacts.

But yes, there would be a sonic boom. You can with a fast enough impact even have a sonic boom in solid materials.

The current best estimates suggest that the Chicxulub impactor was a stony asteroid (a carbonaceous chondrite) of about 10 km diameter, that impacted at around 20 km/s, at an angle of 45 to 60 degrees from the horizontal, coming from the northeast.

The sound rom the engines should I think not change from the time the vehicle goes supersonic up to engine cutoff, since from that point on, the only sound from the engines that can reach the crew is that which is transmitted through the vehicle structure.

Aerodynamic noise from the air flowing around the vehicle (though I don't know how audible that would be with the smooth aerodynamics around an ascending rocket) would of course steadily dimish during ascent.

As a rough estimate, the illumination should be of the same order of magnitude as a clear, moonless night on Earth, which at about 200 microlux of illumination is about 500 million times fainter than a clear summer noon at mid-latitudes, or about 1250 times fainter than a full moon.

With fully dark-adapted eyes, it won't be complete blackness, but it would be pretty damn close, certainly too dark to make out anything but rough shapes. If you want any fine details to be visible the way they are on ships in scifi, you will need artificial illumination.

Needing to match exit pressure to ambient pressure is also why increasing the chamber pressure gets you a higher efficiency in atmosphere, because it lets you use a greater expansion ratio for the same exit pressure. For example, the Rocketdyne F-1 and the SpaceX Merlin are both kerosene-oxygen rocket engines that use a gas generator cycle, and both have relatively similar specific impulse in a vacuum (F-1 304 s, Merlin 311 s). But where the F-1 has 7 MPa of chamber pressure, the Merlin has 9.7 MPa, which translates into a significantly higher specific impulse at sea level (F-1 263 s, Merlin 282 s).