Theoretical question about a new Energy and implications of using it

[Mshenko]

Toady we use energy sources like fossil fuels which in turn cause global warming, which is a slow process in which our planet changes its habitat to a hostile one for humans.

For a science fiction book idea I would like to know if there is a theoretical source of energy that using it would create a slow process that would change the habitat of a civilization living in the solar system / several solar systems (meaning using this source would slowly destroy or change somehow the solar system or the universe).

 

[DaveC426913]

You'll have to make something up.
It might be possible to find a source of energy that pollutes a solar system but stellar systems are just too far apart to have anything but a fantastical effect on each other.

If your story idea is meant to be a cautionary analogy, it may have the opposite effect.

 

[Mshenko]

You'll have to make something up.
It might be possible to find a source of energy that pollutes a solar system but stellar systems are just too far apart to have anything but a fantastical effect on each other.

If your story idea is meant to be a cautionary analogy, it may have the opposite effect.

Why would it have the opposite effect?

Maybe the emphasis should be on the solar system level, I just figured maybe such a theoretical energy source could have effects on the universe even if the civilization is only on the solar system

 

[anorlunda]

Maybe the planet is cold, and it needs the fossil fuel energy to warm it up enough for humans. Maybe it needs some greenhouse gasses to help it retain heat from its star.

 

[Mshenko]

Maybe the planet is cold, and it needs the fossil fuel energy to warm it up enough for humans. Maybe it needs some greenhouse gasses to help it retain heat from its star.

Please only relevant comments

 

[Hornbein]

Toady we use energy sources like fossil fuels which in turn cause global warming, which is a slow process in which our planet changes its habitat to a hostile one for humans.

For a science fiction book idea I would like to know if there is a theoretical source of energy that using it would create a slow process that would change the habitat of a civilization living in the solar system / several solar systems (meaning using this source would slowly destroy or change somehow the solar system or the universe).

Isaac Asimov published a book based on this idea in 1971. Star Trek NG had an episode same.

It is believed by some that there is a vacuum more stable than the one we see. That would result in the destruction of the Universe. Or dark matter is a mystery, you could have the interactions with that change in some way.

 

[mc Kravitz]

There is already massive amounts of energy transfers occurring. In fact if we could somehow extract energy from the moons orbital energy we could power the entire Earth for 10's of millions of years. This is already occurring by tidally driven energy experiments. The tides are already adding energy to the moons obit by a transfer of energy from the Earth's rotational energy to the moons orbital.
I know that speculation is not allowed in this forum and I expect to be penalized by my comments but; Perhaps a super conducting ring placed around the moon and driven by solar power could transfer energy to earth.

 

[anorlunda]

In fact if we could somehow extract energy from the moons orbital energy we could power the entire Earth for 10's of millions of years.

That sounds like Trantor, from Asimov's Foundation series.

 

[DaveC426913]

Why would it have the opposite effect?

The lesson were learning in the 20/21st centuries is that our planet is not limitless in its capacity as a resource, and that we are all living on the same tiny, fragile island.

Expanding this to a multiple star venue will destroy the importence of interconnectedness and interdependence because there's just too much distance between stars. It would be akin to 19th century mentality of dumping our raw sewage into the oceans because they seem to be limitless.

You would have a tough time convincing the reader that the 20 trillion miles between us and A.centauri is small enough that were choking them with our pollution.

Maybe the emphasis should be on the solar system level,

Yes.

 

[Melbourne Guy]

For a science fiction book idea

I'm with @DaveC426913, there is nothing in our current science that causes the effect you are seeking, @Mshenko, though there are many stories where we've tapped the sun and caused a cataclysmic event (for the Solar System at least).

I note that @Hornbein has already flagged dark matter and vacuum energy, the latter of which has also been used in stories for universe-spanning cataclysmic events. Those or dark energy would be the mechanisms that I would use.

I know that speculation is not allowed in this forum

There is latitude for this in the science fiction forum, @mc Kravitz

Please only relevant comments

And please be polite, @Mshenko. If you don't think the comment is relevant, just ignore it, there is no need to slap the contributor. Or you can redirect, particularly when you can see that @anorlunda has over 10,000 posts to their name (and a very high reaction score), so is likely to respond in more detail if asked nicely.

 

[DaveC426913]

vacuum energy

Yeah. This one has the virtue of being considered by scientists, and is not mere fanciful fiction.

The downside is that it is an all or nothing thing. Either it has not happened - or it wipes out the entire universe at the speed of light.

 

[Melbourne Guy]

The downside is that it is an all or nothing thing. Either it has not happened - or it wipes out the entire universe at the speed of light.

I reckon you could hand wave your way out of the light speed aspect, @DaveC426913. Make the transmission dependent on mass density or something along those lines, so there's a chance for the cast to out run it, then include a hard-to-engineer solution, such that protagonist can fix it. There has to be a sacrifice involved, obviously, but you've the making of a Greek science fiction tragedy in that mix!

 

[mfb]

The Gods Themselves
By Asimov (of course)

A civilization swaps matter with a civilization in a different universe with somewhat different fundamental constants. What's stable for them is a highly unstable isotope for us and vice versa, so the radioactive decays release energy. After a while of using this seemingly infinite energy source they discover that the exchange also alters the fundamental constants in both universes slowly (making them approach each other), and using it for too long would cause problems for the Sun.

Spoiler

They later solve this by exchanging energy with two universes with opposite directions of the deviations, gaining energy from both exchanges while cancelling the effect on the physical constants.

 

[some bloke]

For something which would be an issue for the planet, that is spiralling out of control and needs to be something of an analogue for global warming, then perhaps scientists find a way to harness gravity to generate energy. They used the nearest influential mass first (the moon), and in doing so disrupt the interaction between it and earth, and the moon floats away. Now people are using the Sun, and the Earth is drifting off - but the more it does, the more energy is needed t okeep warm, so the problem exacerbates.

Earth drifts into the asteroid field and they start using asteroids for fuel - pulling them into orbit only to use that energy to power the world, and releasing them again. Earth is on a trip out to the lonely outer edge of the solar system., hoping to be snagged by Jupiter as they pass for another kick of energy.

This could even be a projected energy use thing - so the Earth is actively disrupting or "focussing" the suns gravity, causing all the planets to shift their orbits. Perhaps we started by drifting away, and then realized that this will lead to destruction, but instead of better energy generation, they find a way to boost the suns gravity to hold them in place (perhaps by focussing it somehow).

It's very far into the "Fiction" side of sci-fi, but it could well destroy a solar system.Another option is a Dyson sphere, so that the other planets are cut off from the suns light. Other planets cool down and any life there becomes extinct. Then one day, a planet-sized meteor hits the sphere and shifts it around, leaving Earth in the dark, the lasers transmitting the energy missing, and us coming to terms with our own destruction. Or the lasers shoot off into space and start a war - depending on the tone of your book!

 

[Algr]

You'd need to ADD energy to the moon in order to have it float away.

If you are going to advocate real scientific issues, even through metaphor, you'll need to get your science right. If your story was a metaphor for something else, like personal loss, then this kind of fantasy planet moving would be okay.

 

[some bloke]

You'd need to ADD energy to the moon in order to have it float away.

If you are going to advocate real scientific issues, even through metaphor, you'll need to get your science right. If your story was a metaphor for something else, like personal loss, then this kind of fantasy planet moving would be okay.

That's a fair point. Though if two objects are orbiting one another (EG the Earth and the moon) and the force holding them together is suddenly reduced (IE the force accelerating the moon towards Earth is harnessed using unobtanium and used to drive a turbine instead of accelerating the moon toward the earth) then the moon would leave Earth's orbit. In the same way as if you switched off gravity, it would not cause the moon to fall to earth, it would cause it to fly off.

So if you make up a device which can turn down gravity between two objects and then use the energy which would have attracted them together to generate electricity, then that would have that effect.

From the scientific standpoint, the moon would only need to gain energy if it were in a fixed gravitational field. if gravity reduces, the moon goes further away - not because it is gainign energy, but because it has more than it needs to be in this orbit - so it moves outwards.

 

[Frabjous]

Toady we use energy sources like fossil fuels which in turn cause global warming, which is a slow process in which our planet changes its habitat to a hostile one for humans.

I remember a story that posits that humans were placed on Earth explicitly to transform it into a globally-warmed planet.

 

[anorlunda]

Toady we use energy sources like fossil fuels which in turn cause global warming, which is a slow process in which our planet changes its habitat to a hostile one for humans.

Is hostile necessarily bad? In an overpopulated world, nature needs a way to bring things back into balance. A mass die out of some of the overpopulated species could be viewed as a necessary, and healthy,
correction.

 

[Algr]

Is hostile necessarily bad? In an overpopulated world...

Is killing off most of humanity necessarily bad? Gee, let me think about that...

Words like "hostile" are necessarily pov. Rocks don't really have an opinion on such things.

 

[mc Kravitz]

That's a fair point. Though if two objects are orbiting one another (EG the Earth and the moon) and the force holding them together is suddenly reduced (IE the force accelerating the moon towards Earth is harnessed using unobtanium and used to drive a turbine instead of accelerating the moon toward the earth) then the moon would leave Earth's orbit. In the same way as if you switched off gravity, it would not cause the moon to fall to earth, it would cause it to fly off.

So if you make up a device which can turn down gravity between two objects and then use the energy which would have attracted them together to generate electricity, then that would have that effect.

From the scientific standpoint, the moon would only need to gain energy if it were in a fixed gravitational field. if gravity reduces, the moon goes further away - not because it is gainign energy, but because it has more than it needs to be in this orbit - so it moves outwards.

I did some rough calculations;

The magnitude of moons orbital energy is 36 x 10^27 Joules .

The present global energy consumption of Earth's civilizations is about 600 x 10^18 Joules per year.

Therefore the moons orbital energy could supply the Earth for about 60 million years.

After 60 million years the moon would crash into the Earth so it's more reasonable to consider a shorter time line. Like maybe a thousand years.
It's most likely that we would not be able to find a method to extract all our energy needs but even a sizable fraction could make a big difference.

If we did get 100% here's what we could expect:
In that time the moon would move about 6.5 meters per year closer to the earth. That would only amount to .0017 percent of it's present distance per year.

Right now the moon is moving away from the Earth at a rate of 3.78 cm per year. This added orbital energy is coming from the Earth's rotational energy which is actually an order of magnitude larger than the moons orbital energy. This is causing the length of a day on Earth to increase by about 75,000th of a second per year.

The bottom line is that there are two massive sources of energy that are available to us. Tapping into a miniscule fraction of this energy would power civilization for a long, long time with almost imperceptible changes to dynamics of the earth/moon system.

But is it possible with our present technology?

Consider magnetizing the moon. Every point on the Earth surface would be moving in the moons magnetic field. A coil of wire properly oriented anywhere on the Earth's surface would have a current induced in it.
The temperature on the moon is cold enough( in the shade) to support a 0 resistance superconducting wire. We can add solar to the mix by using solar energy to provide the power to the ring around the moon.

 

[Melbourne Guy]

A coil of wire properly oriented anywhere on the Earth's surface would have a current induced in it.

It seems like an indiscriminate energy source, @mc Kravitz, the sparks would literally fly! Every day a Carrington Event, oh the fun we'd have

But your calcs are suggestive, is there a practical way to harness orbital energy?

 

[mc Kravitz]

It seems like an indiscriminate energy source, @mc Kravitz, the sparks would literally fly! Every day a Carrington Event, oh the fun we'd have

But your calcs are suggestive, is there a practical way to harness orbital energy?

Your point is well taken and unquestionably shocking. But think of the light show it would provide every night.
I considered the possibility of ferrying some of the moons orbital energy directly to Earth or to a satellite in a lower Earth orbit from which transport the surface could occurs with less of an electrifying performance.

We are now using gravity assists, to increase the energy of space probes. The technology is well developed and based on conservation of momentum. A massive satellite flown by the moon at a properly orientated trajectory would gain kinetic energy at the moons expense.
Since fly-bys are also used to slow down satellites it may be possible to capture this increased energy.
Off the cuff, if the excess (or a large percentage of it) momentum could be in the form of angular momentum and if the satellite had a magnetic moment, we would have the ability to capture the energy as it passed by Earth or a low Earth orbit satellite.
Consider a chain of satellites with magnets placed around the perimeter are put into a figure eight orbit traveling between the Earth and moon.
Large permanent magnets are placed on the moons surface with alternating poles pointing up. As the satellites pass close to the moon they'd gain angular momentum, like the stators and rotors in a motor.
Much of the energy would be stored in the magnetic field and extractable when the satellite is near Earth orbit.

 

[DaveC426913]

After 60 million years the moon would crash into the Earth so it's more reasonable to consider a shorter time line. Like maybe a thousand years.

Yeah, I think your erring on the side of caution by a factor of 3+ orders of magnitude is warranted.

We know historically that any resource perceived as unlimited is never husbanded wisely. Fish, carrier pigeons, whales, coal, RAM, hard drive memory, automatic powered doors, etc. The demand rises according to availability.

And at an outrageously geometric rate. No one predicting consumption rate of anything a quarter of a century hence seems to get within an order of magnitude.

We would find reasons to leave devices running 24/7. It might be as simple as devices needing to be powered up and down are now more expensive the just leaving them on. (This has been the case since the first VCRs were built, and later with the replacement of the POWER button with the STANDBY button).

What would a society look like if energy were dirt cheap AND corporations still needed a way to separate citizens from their money? (I submit that Pixar's Wall-E made a pretty good attempt at rendering that vision.)

 

[mc Kravitz]

Yeah, I think your erring on the side of caution by a factor of 3+ orders of magnitude is warranted.

I'm new to this forum, but have been soundly admonished by the moderators for posting that aren't physics related. I also get admonished for questioning why I get admonished, So in anticipation of more bad points, I'll ask you "DaveC426913" to explain how the bad, wasteful habits of humans has anything to do with physics?

 

[DaveC426913]

I'll ask you "DaveC426913" to explain how the bad, wasteful habits of humans has anything to do with physics

This is in the sci-fi and world-building forum. Different rules. By definition, it is speculative and involves how human nature will direct the physics of the future.

There is nothing wrong with reporting this post for your clarification - and mine. It wouldn't hurt to have a mod confirm or correct my interpretation of this subforum's protocols.

 

[mc Kravitz]

Maybe they just like to pick on me. I swear it was a post I made in this very forum that got me a slap on the hand.
Back to the topic. I can't argue that humans would find a way to mess up with unlimited energy, just as they are with too little. Perhaps we need to look for sources of energy that can't be converted into weapons.

 

[Melbourne Guy]

Maybe they just like to pick on me. I swear it was a post I made in this very forum that got me a slap on the hand.

Looks like it was a post in the formal forums, @mc Kravitz, regarding the "fudge factor" question that you were admonished for, I'd be surprised if you were Chris Rocked for anything in this section. Which isn't to say you can't be, but as @DaveC426913 notes (and I noted in post #10 above) this part of PF is intended for speculative ideas related to the art of science-fiction and your posts on gravitational energy aren't likely to trigger any ire.

And back on topic...

Perhaps we need to look for sources of energy that can't be converted into weapons.

Is that even possible, do you think? It could make for an interesting 'us vs. them' story, where aliens cannot conceive of such weaponry, though I can't immediately imagine the thematic benefit. But I'd expect that were there is energy, there is likely to be a weapon in the making!

 

[mc Kravitz]

I thin

Looks like it was a post in the formal forums, @mc Kravitz, regarding the "fudge factor" question that you were admonished for, I'd be surprised if you were Chris Rocked for anything in this section.

There was one other admonishment I received but for reasons as yet unknow my wrist was un-slapped.
I take it, you're a moderator on this forum.
Would it be safe for me to present all my other radial ideas in the forum? I have many.

 

[DaveC426913]

Y'all should prolly take this to PM.

 

[Melbourne Guy]

I take it, you're a moderator on this forum.

Not a Moderator, @mc Kravitz, just a diligent observer

Would it be safe for me to present all my other radial ideas in the forum? I have many.

This part of PF is for the discussion of sci-fi as it pertains to creative endeavours - mostly stories but also occasionally games - so it is generally okay to posit 'radical ideas' in context, but lobbing them in, just because you want to? That's likely to raise eyebrows and probably another slap.

Honestly, if you're after such discussions, Reddit is possibly a better site. I find, as an author, that this part of PF provides access to thoughtful consideration of physics - real and imagined - and helps develop my narrative.

 

[mfb]

But your calcs are suggestive, is there a practical way to harness orbital energy?

To change the orbit you need to change the energy (that's fine) but also the angular momentum. A closer orbit of the Moon has a lower angular momentum. Total angular momentum is conserved. Where did the difference go?

Lowering the Moon's orbit to geostationary orbit would release 3.1*10²⁹ J by the way, a factor 10 more than calculated above. The factor 1/2 comes from the ratio of total energy to gravitational energy. Tides would be a massive problem until the orbit is locked to Earth's rotation.

@mc Kravitz: Please keep posts on topic here. Not sure what you mean by "radial ideas" (radical ideas?), but they might not be a good fit anywhere. Moderators/Mentors have a green "Mentor" badge, like the one you can see at the top of this post.

 

[mc Kravitz]

Lowering the Moon's orbit to geostationary orbit would release 3.1*10²⁹ J by the way, a factor 10 more than calculated above. The factor 1/2 comes from the ratio of total energy to gravitational energy. Tides would be a massive problem until the orbit is locked to Earth's rotation.

@mc Kravitz: Please keep posts on topic here. Not sure what you mean by "radial ideas" (radical ideas?), but they might not be a good fit anywhere. Moderators/Mentors have a green "Mentor" badge, like the one you can see at the top of this post.

Have you ever seen the vis viva equation? It calculates the total energy of an orbiting body. It is derived from the sum of potential (gravitational) energy and kinetic energy and yes it takes into account angular momentum. That is the formula I used in my calculations. Remember, the kinetic energy is always positive but the potential (gravitational as you call it) is negative except at infinity where it approaches zero. The total orbital energy is always negative. It is the difference in orbital energy that matters. And that is what I used in my calculation.
I now realize that I did make one mistake. I should have used the semi-major axis of the orbit rather than the phrase "distance from the earth". The semi-major axis is equal to the radius when the orbit is a perfect circle.

I once had a math teacher who was not the brightest bulb in the chandelier. Whenever questioned, she would respond with the statement "I'm the teacher, you're the student" . I managed to ace the course by doing what the teacher wanted and not what the books and common sense dictated. [Insult deleted from post by the Mentors]

 

[Melbourne Guy]

Lowering the Moon's orbit to geostationary orbit would release 3.1*1029 J by the way, a factor 10 more than calculated above.

Is this similar to using anti-matter for power, @mfb? You need to expend the same amount (probs more in practice) to create the anti-matter in the first place, before you can then annihilate it to use the energy. I'm thinking that from your "lowering the Moon". Seems like it's not going to happen by itself!

 

[berkeman]

I'm thinking that from your "lowering the Moon". Seems like it's not going to happen by itself!

If you tied a long rope around the Earth and ran it up to the Moon and tied it around the Moon, it would only take a little while to reel in the Moon, no?

 

[Melbourne Guy]

If you tied a long rope around the Earth and ran it up to the Moon and tied it around the Moon...

Since we're in the sci-fi forum, I'm gunna say, "Yes!"

 

[mfb]

Is this similar to using anti-matter for power, @mfb? You need to expend the same amount (probs more in practice) to create the anti-matter in the first place, before you can then annihilate it to use the energy. I'm thinking that from your "lowering the Moon". Seems like it's not going to happen by itself!

No. There is nothing to spend, it's energy gained from the gravitational attraction between Moon and Earth. You do have to get rid of angular momentum, however.

 

[DaveC426913]

No. There is nothing to spend, it's energy gained from the gravitational attraction between Moon and Earth. You do have to get rid of angular momentum, however.

I think what MG is asking is HOW you go about lowering the Moon so that the energy becomes available. Retro rockets or some such?

Oh! i got it. A huge magnet on the Moon and a motor on Earth. The moving magnet induces current in the motor, which provides power. The moon in turn experiences magnetic drag, causing it to fall closer.

Booyah!

 

[berkeman]

Dont you need to slow it down, maybe using rockets or some such?

Rope...

 

[DaveC426913]

Rope...

I am not sure of the details of the Moon lasso motor, but now that i worked out the electromagnetic generator, i can see the principle is sound. Any mechanism that constricts the moon's movement in its orbit can be hooked up to a generator.

 

[mc Kravitz]

I am not sure of the details of the Moon lasso motor, but now that i worked out the electromagnetic generator, i can see the principle is sound. Any mechanism that constricts the moon's movement in its orbit can be hooked up to a generator.

My thinking exactly. The amount of constriction can be miniscule in terms of the Earth moon system but provide a substantial amount of energy to the earth.
Anyone got any ideas on just how to safely get the energy to earth?

<Off-topic comment deleted: please place feedback in the dedicated feedback forum, not in the technical forums>

 

[DaveC426913]

<Response to off topic comments deleted>

Anyone got any ideas on just how to safely get the energy to earth?

I do. Post 37.

 

[mc Kravitz]

I do. Post 37.

That was my assumption in my initial post 20. Melbourne Guy clearly pointed out the danger of using that method in his response; post 21.
Anyway, thank you for agreeing with the original idea.
If we want "established physics" to join us in this quest, we'll need a safe and effective method to extract energy from the moon's orbit.

As a result of Melbourne guy's post, I started to consider a strong concentrated magnetic field that could be ferried closer to Earth where it could energize a generator without putting on a light show in every electrical distribution network on the planet.

I think this is a worthy topic even though PF will only allow it in a "fictional sense" and it deserves some debate.

I know the moderators here are honestly trying to protect the fragile minds of student and beginners but let's remember the words of Albert Einstein

"Creativity is intelligence having fun" Albert Einstein
"The measure of intelligence is the ability to change" Albert Einstein

I believe that future discoveries in physics will come from the young/young at heart physicists.

 

[berkeman]

I believe that future discoveries in physics will come from the young/young at heart physicists.

If this helps to motivate you to keep studying more science and working on contributions, that is a very good thing. Please do keep working your way up through the levels of school -- that's where you gain the understandings of mainstream science that help you to extend that knowledge.

 

[mc Kravitz]

I want to apologize to DaveC426913. If I offended him, it was not intentional. I received 4 warning points for "insulting a member". I assume it was my attempt to correct his understanding of orbital energy. I had just finished a college level class on orbital mechanics and I just assume that everyone on here would know the mechanics of it. It is clear to me now that that was an unfair assumption.
I did finish at the top of the class and I honestly believe that I understand the topic very well. I'm sure I could get a letter from the professor verifying that.
I would be more than willing to help anyone on this forum with orbital mechanics problems.
It was the material I learned in the class that made me think of the possibility of extracting energy from the moons orbit.
DaveC426913 did get the larger picture, as evidenced by his post (#37).
Melbourne Guy, to his credit pointed out the potential dangers of my original proposal and I quickly and apologetically agreed with his assessment. I did not intend to insult him either.
The fact that many people only think of the kinetic energy component of orbital energy is completely understandable, although incorrect.
If you extract kinetic energy from an orbiting body, it does "slow" it down at that point in the orbit, but what really happens is that the orbit is altered and becomes more elliptical. In this new elliptical orbit the body will actually have more kinetic energy as it approaches it's periapsis. At periapsis, the potential energy is lower ( a bigger negative number). Extracting kinetic energy at this point will lower the eccentricity again altering the orbit. The point is; if we are going to try to develop the mechanics of actually extracting orbital energy for the good of all mankind (which I feel confident can be done), we must fully understand orbital mechanics.
As I pointed out in an early post and DaveC426913 agreed in his post 37, magnetic field energy transfer seem the best option. But not disturbing our electrical grid must be a prime objective.
Since I am a no-body to mainstream physics at this point in my life, I choose to seek out help from imaginative young or young at heart people on forums. I apologize to the moderators of this forum if that offends you. But I must try! If I m incorrect I'll be the first to admit it, as evidenced by my reaction to Melbourne Guys insightful post.

 

[Melbourne Guy]

No. There is nothing to spend, it's energy gained from the gravitational attraction between Moon and Earth. You do have to get rid of angular momentum, however.

I'm struggling with "you do have to get rid of the angular momentum" aspect, @mfb. Possibly, @berkeman's lasso idea was tongue in cheek, but doesn't it take energy to 'reel the Moon in'? Given, angular momentum is is a conserved quantity, where do you 'get of it' to?

Melbourne Guy, to his credit pointed out the potential dangers of my original proposal and I quickly and apologetically agreed with his assessment. I did not intend to insult him either.

No fear, @mc Kravitz, I did not take anything you wrote as insulting, to me at least. I obviously can't talk for others. PF is generally a very respectful site, which is a credit to the efforts of the moderators and their clear rules, and I find it helpful, if reading a post gets my dander up, to walk away for a while before responding. Usually, that takes any heat out of my planned reply.

 

[mfb]

I'm struggling with "you do have to get rid of the angular momentum" aspect, @mfb. Possibly, @berkeman's lasso idea was tongue in cheek, but doesn't it take energy to 'reel the Moon in'? Given, angular momentum is is a conserved quantity, where do you 'get of it' to?

Well, as implied in post 31 I don't think it's practical, but leaving that aside:

Option A: Let's assume the universe only has Earth, Moon, and some space station far from Earth. You can launch something from Earth to pass behind the Moon in its orbital path. The object gains some kinetic energy and angular momentum, the Moon loses both. Catch that object at the space station, converting the kinetic energy into whatever you want. The space station gets some momentum away from Earth, that can be balanced by the gravitational attraction of Earth over time. The space station also gains some angular momentum, but it's far away so this doesn't correspond to a large angular velocity. Then drop the object so it falls back to Earth. Catching it there recovers the energy needed to launch the object.

Option B to use the Moon's energy: Install a mass driver on the Moon that shoots mass out at the "back", making them stationary relative to Earth. They fall down to Earth where you can extract their kinetic energy, gaining far more than you needed at the Moon. Over time a part of the mass of the Moon ends up on Earth while the Moon goes to a higher orbit. In a universe with only Earth and Moon you could end up with an arbitrarily small moon at an arbitrary distance (having a large angular momentum from being very far away), with the Sun raising the orbit will destabilize the Moon's orbit until it stops orbiting Earth.

 

[Melbourne Guy]

Install a mass driver on the Moon that shoots mass out at the "back", making them stationary relative to Earth. They fall down to Earth where you can extract their kinetic energy,

Shades of Heinlein's The Moon is a Harsh Mistress! But thanks, @mfb, Option A was clear enough for me to muddle through the concept.

 

[some bloke]

Two of the biggest issues I can see with the magnetic generation of energy are that a magnetic field from the moon could well cause electrical currents in everything, and that getting the huge magnets to the moon would be incredibly impractical.

I don't know the physics behind this so it's just supposition, but with the Earth already being a magnet, can we not flip it so that we build the coils on the unpopulated lunar surface (using the silicon which makes up 20% of the surface to make superconductors). Thus the movement of the moon through the Earth's magnetic field will generate power which can then be transferred to Earth via a laser or something. Bonus points for building solar panels on top of the coils!

All of this has gotten a little sideways on the OP's question, and on my suggestion (which was to somehow siphon off the gravity holding the Earth in orbit with the sun, not to slow an orbital body down!). Obviously we don't know enough about gravity to hypothesise a way to do this, but if it were modeled as magnets (and we assume a civilisation who can do this can manipulate gravitational fields like magnetic ones), then can you use the magnetic field to generate power and leave other things orbiting because of it drifting away?

 

[Lren Zvsm]

Toady we use energy sources like fossil fuels which in turn cause global warming, which is a slow process in which our planet changes its habitat to a hostile one for humans.

For a science fiction book idea I would like to know if there is a theoretical source of energy that using it would create a slow process that would change the habitat of a civilization living in the solar system / several solar systems (meaning using this source would slowly destroy or change somehow the solar system or the universe).

I don't know about energy sources, but one possible pollutant that could span the solar system might be self-replicating machines that were designed to build themselves into livable habitats for humans. These habitats might take the form of super tough "blisters," bubbles on the surfaces of moons or asteroids that contain oxygen, water, and enough organic material to form the basis of a hydroponic system of agriculture. (Yes, these latter features might require human help for assembly.)

But what if the self-replicating mechanisms become defective, and reproduce wherever the right combination of minerals exist--water, oxygen, and hydroponic media be damned? What if they start reproducing like cosmic cancer cells? We could destroy them, but could we ever destroy enough of them to stop their spread? What if their initial forms were small enough to "stow away" on manned or unmanned spacecraft ? Might they not displace existing colonies?

 

[Melbourne Guy]

What if they start reproducing like cosmic cancer cells?

It's the grey goo scenario, which Drexler first described in Engines of Destruction, and which has been used in many sci-fi stories, including, peripherally, in Reynolds' Revelation Space series and more recently, The Expanse series.

Fun idea, there are many ways you can go with grey goo, from a limited incursion that is heroically conquered, to an outright blight that can only be outrun and so fractures your civilization.