I wouldn't count either then. Hydro is ultimately powered by precipitation, which is caused by the sun evaporating water. Geothermal is ultimately caused by the gravity of the sun affecting the earth.
I agree with hydro, but you’re wrong about geothermal. Tidal forces caused by the Sun are minuscule compared to that of the Moon. Also, Earth still has a decent amount of latent heat caused by its formation.
It’d be interesting to think of novel ways of getting power from sources other than the Sun.
Theoretically, one could, say, build a space-elevator-like device and use the centrifugal force pushing it away from Earth to run a generator. Of course, for that to work, the weight would have to continually receed from Earth, and may require continually replacing the weight. Ultimately that would rob the Earth of angular momentum.
What I posted would take energy from the angular momentum of the Earth rotating on its own axis, not the (angular?) momentum of the Earth revolving around the Sun.
Honestly, I’m not 100% sure the right way to talk about where the Earth’s angular momentum about its own axis came from. I want to say gravity while the Earth coalesced from dust/gas, but I’m not sure that’s quite true because I think the gravity would only kindof “concentrate” the angular momentum that was already present in the gas/dust that was already present in the cloud. (Like, when an ice skater pulls their arms toward their body and speed up, that doesn’t add energy or momentum to the system that is the ice skater.)
So, maybe it’s more accurate to say it’s kinetic energy from the Big Bang and/or supernova(s?) that produced the gas/dust that eventually formed the Earth?
But I’m pretty sure this scheme would get energy from a source that wasn’t ultimately from the Sun.
That feels like a perpetual motion machine, because the Earth coming together in the first place released energy. I’m guessing it would take more energy to get the weight to geostationary orbit than you could get back.
Maybe it would work if you lowered an asteroid down, instead. And then you could mine it on arrival.
Edit: Nope, it maths. I think it’s down to angular momentum being kind of separate from the gravity well.
So, first off, I’m definitely not arguing this would be a feasible way to get energy in a practical sense in the real world.
But, it wouldn’t be a perpetual motion machine. It’d produce less and less energy as the Earth ran out of angular momentum, ultimately approaching zero.
I don’t think I’ll do the monster math on this, but my gut tells me one could technically and theoretically (not so much in practice) get more energy out of that than it took to get the weight up there. (It might be that the Moon would limit how much energy could be got out of this scheme as well, but I think even with the Moon involved, I think it could still be a net energy gain.) That said, without running the numbers, you might well be right!
Ah shoot, it looks like you posted a minute after my edit, and probably didn’t see it.
Orbital mechanics is big-boy stuff, and gets really subtle the moment you’re doing anything non-trivial. This is just two-body, so in theory it should be doable, but the tether pulling out energy as it goes along makes it more complicated. It’s a bit much tonight, but maybe I’ll give it a shot later. One thing that’s clear just from the equation for orbit energies is that there’s no limit to how much energy can end up inside the weight itself, as it gets faster in proportion with increased height.
For the calculations, I was thinking maybe one could cheese it a bit and get a relatively decent vague idea of the answer if not a more rigorous idea.
My vague idea was that gravity follows an inverse square law while the centrifigul force equasion is linear relative to the length of the tether. We know that gravity pulls toward Earth and the centrifigul force pulls away. So the net force on the weight at any one time is the centrifigul force equasion (a linear equasion) minus the gravity equasion (an inverse square equasion). We also know that the point at which that sum reaches zero is exactly the altitude of a geostationary orbit.
Work equals force times distance. So suppose we just took the area under the curve of that net force equasion from r equals the radius of the Earth to r equals roughly the furthest we vaguely guess we could send the weight before it starts to get sucked into the Moon’s gravity well. And then we divide that by the area under the curve from r equals the Earth’s radius to r equals the altitude of a geostationary orbit. That should at least give us a figure like “the amount of energy we could get back in theory would be roughly x times what it takes to get the weight past the geostationary orbit altitude threshold.”
The mass of the weight would be a term in that net force equasion, but if we just decided the mass was “one unit”, that’d make things a bit simpler. If we only care about the ratio of the energy we get back to the energy we put in, the weight should cancel out anyway.
This approach would certainly ignore a lot of things, but if the answer was “A Large Number™”, I think it would still be reasonable to handwave the details. (If the result was like 1.1 or something, probably “no, that doesn’t even work in theory” is the much safer bet. Let alone if it was less than 1.)
I guess if we wanted to get even more sophisticated, we could take into account things like the weight and tensile strength of carbon nanotubes and see if it would be infeasible to build a tether sufficiently strong without adding a huge amount of weight during the ascent. But I’d be willing to pretend in this thought experiment that we have some material with infinite tensile strength and zero weight at our disposal.
Anyway! Still not trivial math, quite, and definitely not terribly precise or rigorous, but not quite so “big-boy stuff” as modeling the rotational frames and such.
Yeah, that’s probably a better approach than using the energy of the orbits.
Okay, so if we set the weight to 1kg, force is rRe^2^ - GMe/r^2^, where Me is the mass of the Earth and Re is it’s rate of rotation, which is a low number in radians per second. The antiderivative along r is then -1/2r^2^Re^2^ - GMe/r, but you actually don’t need that because you just take the derivative again to find extreme points. rRe^2^ - GMe/r^2^ can be restated as (r^3^Re^2^ - GMe)/r^2^, and that numerator is a diverging, increasing function as you move away from 0, which means yes, the energy is unlimited.
Welp, I was wrong. I think the trick here must be that the rotation of the Earth didn’t actually come from the gravitational collapse itself, but from the pre-existing inhomogeneities of velocity distributions in the early solar system. Even if you could slingshot the mass around the sun, back into the Earth, and collect it again, you would somehow transfer enough of Earth’s angular momentum back to the sun to offset the energy gained.
Gravitational interaction between the Moon and Earth orbiting each other and the Sun …
Moon/Earth were formed within the influence of the Sun and the solar system.
Unless a giant comet ( attracted by Sun’s larger gravity well?? ) introduced something extra-solar , almost everything is under the influence of the Sun.
The gravitational collapse of a cloud of mostly hydrogen in the vacuum of space.
And anything falling together under gravity was given that kinetic energy from somewhere* and ultimately it can all be traced back to the Big Bang.
As for where that energy came from, it's possible we'll never know. Most organised religions (and no doubt a few disorganised ones) have their theories, of course. You may subscribe to one of these.
This is the principle most commonly simplified as "what goes up, must come down"
What’s really interesting is that “what goes up, must come down” doesn’t hold at the scale of the universe. A naive thinker might imagine big bangs happen in cycles, but in fact this doesn’t appear to be the case, because space itself is expanding faster than galaxies are falling back together. And it’s not just faster now, but it’s accelerating! At some point, space will be expanding faster than the speed of light, and because of that, the entire universe will disappear from our view.
Despite that, the Milky Way galaxy is still close enough to the Andromeda galaxy that they’ll collide in about 5 billion years, so don’t worry, there’s still interesting things to come! If you want to see it, though, you’ll need to be somewhere other than Earth, because by that time the Sun will have advanced in its life cycle enough to render Earth completely uninhabitable by all known forms of life.
Just to add onto this comment, it’s thought that the Sun is slowly getting hotter and more energetic as it gets older and in approximately 1 billion years, the Sun will be hot enough to render the Earth uninhabitable for life as we know it.
In approximately 5 billion years, the Sun will reach the end of its life and expand into a red giant, swallowing up Mercury, Venus and potentially Earth in the process. Interestingly, once the Sun reaches this phase of its life, it could potentially warm up some of the outer moons enough for them to have liquid water, if they can hold onto an atmosphere of course.
Someone please correct me if I said anything wrong, I’m just a casual space nerd and not a professional astronomer.
What does "lift" mean in this context? A web search turns up a Doris Day musical from 1951 which is kind of funny to think about but I'm guessing is not what you mean.
As for the general case of modifying the Sun - or any star - in some way, it's all but certain to need a huge number of resources (or amount of energy, or both), and considering the Sun is on the order of a million times larger than Earth, far more than can be obtained from Earth alone.
I mean, I'd like to be proven wrong and there's some exotic-physics way of causing the helium in the Sun to spontaneously turn back into hydrogen, but if that was easy, you'd expect that we'd see stars do that by themselves occasionally. We don't, which implies there would still need to be some kind of energy input required to get it started.
Without exotic physics, we'd pretty much need on the order of the energy that the star had output from birth up to that point, and if we had that, we'd be better off using that energy in other ways.
We could get all Earth life off Earth and into a self-sustaining, space-faring habitat with a minuscule fraction of the resources. We might be better off aiming for something like that.
any of several hypothetical processes by which a sufficiently advanced civilization could remove a substantial portion of a star’s matter which can then be re-purposed, while possibly optimizing the star’s energy output and lifespan at the same time
Geothermal, which at this point in geological history mostly comes from decaying radioactive elements. It’s of minor industrial importance, but it fuels undersea vent ecosystems, and does see some use in traditional cultures.
Speaking of radioactive elements, our nuclear generators all run on energy trapped from ancient cosmic catastrophes. Probably colliding neutron stars, for the most part. Hydrogen fusion has been made to happen for research and in atomic bombs - although interestingly we can’t use the same kind as the sun does.
Tidal energy is used for some power generation, and it comes from the kinetic energy left in the Moon, and to a lesser degree the Earth itself, from the formation of the solar system.
Do you have any source for the radioactive decay part? I always thought the Earth was hot inside simply because it hasn’t finished cooking down from when it formed as a ball of molten stuff. Like a hot potato.
Uh, I’ll find one, and edit. It confused the shit out of Victorian scientists, because they had a good guess how old the Earth is from biology, and had thermodynamics, but it was telling them volcanism shouldn’t still be happening.
These give slightly different numbers from each other, but the gist is that radioisotopes (Uranium, Thorium and Potassium being the primordial ones) account for at least half.
Oh interesting. It turns out it’s more like a demonically possesed hot potato, that is still cooling down but also gets warmer from demonic activity under the earth.
Does that mean that one day the moon will stop revolving and we will be tidal locked? If so, does that theoretically happen before the sun consumes us?
It gets both slower and further away (to stay in orbit) every year, by like 2 cm IIRC.
If you could go back a couple billion years it would be huge in the sky. There was even a period, called the Jatulian, where you might not have asphyxiated in the early atmosphere. There wouldn’t be much else to look at, though, and just your skin germs would be futuristic enough to completely change the course of life on Earth, once they get into the environment.
Uhh, I actually don’t know the answer to that. Orbital mechanics is hard; see me being bamboozled elsewhere in the thread. At some point I’m guessing tidal forces from the sun would start having a major impact, since in reality they’re both in it’s gravitational well at the same time as they orbit each other. Usually that doesn’t make orbits more stable.
Also, the sun will go red giant in 4 or 5 billion years, and will eat Venus for sure. The Earth and Moon may well suffer the same fate, we’re kind of right on the projected edge.
Everyone is giving you some great answers, but there are since more subtle ones worth mentioning too.
When you take a picture of space, the light from those other stars hits the camera sensor and induces a tiny electrical charge, which is captured, amplified, and analyzed to create the image. Your eyes actually work that way too.
It’s not an energy source as you typically think of it; it never powers anything, but technically it is* energy that exists on Earth that didn’t come from our sun.
If it doesn’t have to be energy that’s used as such, there’s more answers.
Neutrinos stream through us each moment at a flux pretty similar to sunlight. Day and night; they sail right through the Earth for the most part. Most of it is from the sun’s core (directly), but some of it is from distant cosmic monsters like supernovae and jets whipping around black holes, and some of it escapes from nuclear reactions on Earth, in particle accelerators and nuclear generators or from decays in nature.
Gravitational waves from distant black hole mergers have been detected on Earth, and they do carry energy.
Meteors hit the Earth, and sometimes they carry enough energy with them to cause damage, like in Chelyabinsk.
You mentioned cosmic rays. The most energetic ones far exceed the energy of anything our accelerators produce, and it’s still a mystery where those unusually powerful ones come from.
Stars give out a lot of electromagnetic energy in the form of radio, microwave, infrared, ultraviolet and x-rays as well as visible light, and probably gamma rays too, although I haven’t heard anything about that one. Many frequencies of light are heavily or even fully absorbed by the upper atmosphere of Earth, which is part of what makes space telescopes necessary.
Lighting strikes on Jupiter are very noticeable as noise on some radio bands. I’m not actually sure how much of the wind that powers that is the Jupiter equivalent of geothermal, and how much is ultimately from sunlight. I’m guessing it skews to the latter, though.
Just to spur this question on a bit, I know from my limited knowledge that cells can kill themselves when a mutation has occurred. But that’s also a sort of biochemical reaction. To be honest, what is truly self-determining? Is it simply a property of the nervous system? My thoughts are leading in that direction to be honest.
Immune cells form from stem cells. From start to finish in the stem cell differentiation process, four major changes occur. Some of these changes can have up to four potential outcomes each. Here’s a map:
While all cells react to their environment based on environmental stimuli and feedback loops, even bacteria and archaea, this is a great example of cell differentiation. All our cells started as stem cells, but the immune system’s continuous and consistent use of the process is very unique. It’s also the most elaborate and the image is surface level. Most the end cells pictured here will become more specific. Like there’s many different T-cells, even T-cells which change so much they don’t meet the classification of being a T-cell. The CD16 T-cell is a great example of this happening.
I feel like this is what you were looking for, but I’m not totally sure.
Thanks! Is there a point during which any of these cells makes a decision that is not 100% mere chemical or mechanical reaction to their immediate environment? Perhaps when they need to differentiate into a new cell?
I mean, cellular/molecular biology is applied organic chemistry. It’s all chemical based in some way or another. I guess with T and B cell receptor formations, each receptor binding domain is made totally at random. So much so, they go through training to ensure they won’t attack self and are able to detect pathogen associated molecular patterns. Wildly, most T and B cells don’t pass training and get recycled, more or less.
So maybe, but you’re talking about the world on the cellular level, it’s all based on chemical reactions with environmental stimuli. To be alive requires responding to your environment, and chemistry is how that works at the microscopic level.
“self-Determination” and “decision-making” are conscious, complex processes. A single cell is incapable of that.
On the other hand, how do we as humans form decisions? We use sensory input from various organs, process those by combining with existing knowledge/memories and form decisions based on that. But in the end, it’s still all based on “chemical and mechanical reactions”.
You quickly get into philosophical territory there: is our conscious self more than the sum of all the processes in our brain? Is there some extra “spark” that allows true self-determination, or are all our decisions a given result of the exact state of our brain and body?
I think that the illusion of free will is based on the fact that we’re conscious and thus have preferences and since decisions naturally tend to align with said preferences it then feels like we’re in control. However, nobody chose their likes and not-likes.
I think Brian Greene put it nicely; we don’t have free will but we have the experience of freedom
I think you’re projecting consciousness onto those terms more than you need to. An algorithm is a decision-making process devoid of consciousness (as far as we know). AI is capable of self-determination in as far as it’s capable of acting without reacting, or without total dependence on input. We just need our self-determination and decision-making to be special, so we present them as functions of our consciousness.
And a curse on any philosopher that tries to define consciousness as some variation of “that thing that makes human special”, any work they build on that is doomed.
Well, you can define the structure of a L-system pretty simply. There’s probably a shared interest between ferns in having a simple set of instructions at a genetic level and mathematicians in working with mathematical structures that have descriptions simple enough for us to reason about.
The function is in the interconnection and collaboration of the parts of the system. A screw or a round rubber also doesn't drive you to work. It's the whole car consisting of several parts that work together that does it. Also a single cell is a tiny part. There isn't much in a single cell if we look at a complex process like making a decision.
The Barnsley Fern was constructed specifically to resemble the species of fern that it does. There are versions of it that have been modified to resemble other ferns. The fractal isn’t some secret mathematical code for why ferns look like they do, it’s more like a drawing of a fern. If someone made a fractal to look like another leaf, it would be just that, not an advancement into the secrets of botany.
The short answer: no. The two do not connect beyond the fact that ferns have a design reminiscent of a fractal, which is likely what inspired the fractal’s creation.
How “real” is it? It is a real set of functions, but if I design a set of functions to look like William Dafoe, it doesn’t mean I’ve cracked the matrix code into his genetics.
There are good answers about differentiation from stem cells, process governed by the evolutionary determined genetic information stored within the cell itself. This genetic information was/is influenced by environment but that influence tends to be slow and subtle.
I have another answer to contribute. Metastatic cancer cells. These are cells which detach from primary tumors in any part of the body, then have to break into the lymph or blood and then they in a sense “decide” where they want to settle. We now know they’ll have preferences: some cancers will metastase to liver, some to lung, some to brain; but before they do so, these cells will literally circle around the body, searching for a “perfect spot”. Once they find it, they settle, often entirely changing their O.G. tumorous behaviour in the process which in return makes them super unpredictable and hard to kill. And all it takes is one wandering cell.
Put an empty bowl in and it comes out cool to the touch.
A bowl of soup and the bowl is crazy hot, because the soup warmed the bowl.
Heating a person with a microwave would make us pop as the water inside heats up faster than everything else. And blood is pretty fucking similar to water…
You could try it with an incredibly low dose, but you’d have to do it in carefully measured bursts. Even for hypothermia, warm baths are dangerous because the increase in body temp is too sudden and can fuck up the heart.
So there’s a whole bunch of risks and you’re still limited to what won’t freak out your heart. Warming just one part warms up the blood that’s there and send it through the cold parts. Like how you’re not supposed to immediately add water to a radiator after a car overheats. The thermic shock can cause massive problems.
Microwaves don’t just heat water molecules, although due to density they absorb a large amount relative to many other substances. Also since humans are mostly water, the heating should be even enough to not be quite as problematic as you describe. Some sensitive areas like eyes are an issue, but otherwise it’s possible a low enough dose could warm someone a couple of degrees without causing any harm.
But wouldn’t the microwaves also warm the heart? There’s no reason a microwave at the right power couldn’t slowly heat someone up. I don’t think the OP is asking about someone who is dangerously cold either, so the extreme care that needs to be taken when someone is in serious danger due to how cold they are might not be relevant in this case.
But you know what heats a cold heart faster than blood from another body part?
Direct exposure to microwave radiation…
That’s what I mean, there’s a safe temperature differential to warm the body, and even stuff as conventional as a warm bath or hut tub can be too much.
If we shoot microwaves at a heart, the heat increase is waaaaaaaay above the safe limits.
So if someone was in a situation where the only method was microwave radiation, it wouldn’t result in an increase in heating without running serious risks.
There’s just no benefit and it introduces insane risks if you tried to do it slow enough.
My point is that the heat increase of the heart doesn’t have to be so insane. If someone was designing a microwave human heater they would have to make the power level such that it would always result in a safe rate of temperature increase. Obviously using an off the shelf food microwave wouldn’t work.
Is heating someone too quickly a concern if they don’t have hypothermia? Like if I’m sitting round in my house and start to feel cold, and I get in a hot bath, it’s not going to heat me up too fast, right?
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