Not 2500 years, until the rate of satellite re-entry becomes 2500 times higher. That is a per year figure, not one that adds up.

The salt itself doesn’t make the water any colder. It just lets the water get colder before freezing, and increases the rate of heat transfer. For sweat, if it’s not much below freezing it’s really no different than being wet. With that said, sweating when it’s really cold out actually is dangerous.

That is not how time dilation works. It is not a 1 to 1 rate or people who are twice as heavy would experience them moving at super speed. At the surface of the Sun, time dilation is at a rate of ~67 seconds per year. Or, for every year on Earth only 364 days, 23 hours, 58 minutes, and 53 seconds will have passed.

As for how the star runs out, the end result of fusion is that two hydrogen atoms turn into 1 helium atom. Eventually, all the hydrogen atoms in the star have been fused. Of course there will be some hydrogen left in the star, but it is too diffuse to continue fusing at a rate to sustain the star. Remember that stars are a delicate balance between the pressure exerted by all the heat and fusion, and the gravity trying to contract it.

Last, the sun is 1.3 million times the size of Earth by volume and 333,000 times the mass of Earth.

Can you better explain what the question is? If you mean a fusion reactor, the fusion reaction continues until you either run out of fuel or can no longer maintain the containment and allow the materials to spread/cool too much to continue fusing. I don’t see how time dilation comes into play, or what a 10 billion year time scale has to do with anything.

In general, canned goods stay good until the can itself is damaged (I.e dented, rusted, or otherwise leaking can). The “best or use by” date on the can is just an estimate by the manufacturer for how long it’ll be at peak freshness. If you have a use by 2028 on canned tomatoes that’s probably an estimate of when those tomatoes will have lost their texture and started developing “off” flavors.

How do you get the energy out? My understanding is that fission plants are essentially fancy steam boats, heating water to turn a turbine that powers a generator. How does this work in theory for a system like this?

I’m going to actually assume you’re an out of context beginner. The earlier responses are right but they aren’t actually helping you understand the concept.

The perfect nozzle has the ambient pressure exactly match the exhaust pressure. This because any excess pressure in the exhaust gases is wasted energy that could have been done. And if the pressure drops below ambient, that means the atmosphere will be pushing in on your exhaust gases, reducing velocity and thus performance.

But ambient pressure changes with altitude. So the perfect exit size changes as you ascend with it. In theory, an infinitely adaptable nozzle would be ideal, but to accomplish that objective requires weight. And the rocket equation tells us that the pounds of mass we have to take to orbit isn’t worth what you would have to spend to get it there .

I think this is a little naive. Anabolics may have fallen out of favor for athletes but that’s because better stuff was created. PEDs, which is what people colloquially mean by steroids, are caught in the systems of athletes every year. For example in 2022 alone DeAndre Hopkins and Fernando Tatis both served long suspensions for PEDs. Yes, they both used the old fall back of a banned substance was contained in a legal workout supplement but that’s a really thin excuse. They aren’t using them to get huge anymore, they are using them for improved energy, endurance, and the key for football: recovery.