The time limit of 1000 years is the worst part of this paper. If the energy consumption literally grows 2% every year, in 3013, the humanity will be consuming 3.98x10^8 times more energy than now. If it's really the case, the dissipation heat from the use of such a large amount of energy alone will kill us all, long before the tidal lock b/w the earth and the moon.
Tidal energy is not renewable
271–280 of 350 posts
Re: Tidal energy is not renewable
#272The single most important assumption in this paper is that energy consumption will increase by 2% per year. This kind of exponential growth leads to outlandish estimates for the amount of tidal energy that society will demand. Energy consumption has decoupled from population growth rates and economic growth. How much energy will we consume in 1,000 years? Most projections of the population have it stabilizing at arou…
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. […] How much energy will we consume in 1,000 years I keep posting this link here on HN but, once again, it seems very appropriate: > The upshot is that at a 2.3% growth rate (conveniently chosen to represent a 10× increase every century), we would reach boiling temperature in about 400 years. https://dothemat…
That's not a great argument by the physicist, the economist definitely won that debate. The physics guy only seems to realize that though when he wakes up the next day and has calmed down a bit.
Although the link is useful for the thermodynamic calculations, there are two major problems with the argument as presented:
1. Right up front the physicist arbitrarily bans space travel. The economist, being an agreeable man who'd probably rather be making smalltalk with a pleasant member of the opposite sex rather than defending his whole profession to a bolshie physicist, accepts this limitation, but he shouldn't have done. Nothing in economics is predicated on a space travel ban. We are already obtaining economic growth from space via satellites and that era has barely got started. None of the physics arguments work if you make the relatively small leap to putting factories, power plants etc on moons, asteroids, space stations or other planets. This doesn't require colonization assuming progress in robotics.
2. Much more seriously, the physicist doesn't understand what growth or wealth mean in an economic context. The economist tries patiently to explain this to him many times, and he just doesn't get it. This is a very common problem when talking about economics because people aren't used to the expansive definition of wealth economists use, so often conflate it with other things like money or (in this case) energy.
You can increase wealth indefinitely even with a stable population and stable energy/resource usage. This isn't controversial or weird, it's just part of how wealth is defined. The VR example is one attempt, dessert another attempt to explain this to him, but he just doesn't get it until the next day when he suddenly has an epiphany but decides it wasn't his fault because he personally distinguishes between "growth" and "development". No such distinction is recognized by actual economists for valid reasons. But you don't get to claim there's a problem with economics just because you failed to understand the lingo of the field.
Re: Tidal energy is not renewable
#273Earlier quoted context omitted.
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. […] How much energy will we consume in 1,000 years I keep posting this link here on HN but, once again, it seems very appropriate: > The upshot is that at a 2.3% growth rate (conveniently chosen to represent a 10× increase every century), we would reach boiling temperature in about 400 years. https://dothemat…
A global cooling system is easily conceivable. The ISS uses radiators to dissipate heat into outer space. We could do the same. We could concentrate heat with heat pumps and pump hot steam, molten salt, or plasma up a space elevator and radiate the heat away. Edit: The link points out that in 1,400 years we'd be using energy at the rate produced by the sun and in 2,500 years at the rate of the entire Milky Way. Even…
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Re: Tidal energy is not renewable
#274Earlier quoted context omitted.
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. […] How much energy will we consume in 1,000 years I keep posting this link here on HN but, once again, it seems very appropriate: > The upshot is that at a 2.3% growth rate (conveniently chosen to represent a 10× increase every century), we would reach boiling temperature in about 400 years. https://dothemat…
A global cooling system is easily conceivable. The ISS uses radiators to dissipate heat into outer space. We could do the same. We could concentrate heat with heat pumps and pump hot steam, molten salt, or plasma up a space elevator and radiate the heat away. Edit: The link points out that in 1,400 years we'd be using energy at the rate produced by the sun and in 2,500 years at the rate of the entire Milky Way. Even…
> A global cooling system is easily conceivable.
That sounds like a line from Dr. Strangelove by the titular character with ol' Bucky following up with "Mr. President, we should not allow a heat pump gap!".
Re: Tidal energy is not renewable
#275The single most important assumption in this paper is that energy consumption will increase by 2% per year. This kind of exponential growth leads to outlandish estimates for the amount of tidal energy that society will demand. Energy consumption has decoupled from population growth rates and economic growth. How much energy will we consume in 1,000 years? Most projections of the population have it stabilizing at arou…
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Re: Tidal energy is not renewable
#276Is this satire? It seems like there's too much math in this to be satire.
It seems like https://what-if.xkcd.com/, absurd hypothesis and correct maths
Re: Tidal energy is not renewable
#277Earlier quoted context omitted.
A global cooling system is easily conceivable. The ISS uses radiators to dissipate heat into outer space. We could do the same. We could concentrate heat with heat pumps and pump hot steam, molten salt, or plasma up a space elevator and radiate the heat away. Edit: The link points out that in 1,400 years we'd be using energy at the rate produced by the sun and in 2,500 years at the rate of the entire Milky Way. Even…
we can (and do) radiate heat into space already. there's a specific infrared wavelength that passes out of our atmosphere unimpeded. building things which receive sunlight but which emit IR at this wavelength would have a cooling effect, though I don't know to what scale. no need to pump anything up to space, lol. just put hot stuff inside vessels which are painted with a material which radiates heat at this specific…
Uh, paint doesn't radiate heat not does it convert IR frequencies. (except for very unusual, usually fluorescent materials)
It reflects incident IR.
Re: Tidal energy is not renewable
#278Earlier quoted context omitted.
Where does the energy go then? EM radiation leaving the planet?
Chemical energy. Like the plants, they take sun energy and store it as chemical energy. We could do the same, take CO2 and water and make CH4 and oxygen (electrolysis + Sabatier reaction) and make plastic. Or take ore, aluminum oxide and iron oxide, and "unburn" them releasing again oxygen (we already do that) etc... We mostly use energy to manufacture things. Life takes energy and lowers the entropy of the planet. W…
There are limits to doing this, which is why we find it really hard to, say, remove CO2 from the atmosphere.
The technical reason is called entropy. Diffuse heat is hard to concentrate and use, much like gas outside of a container.
Re: Tidal energy is not renewable
#279Earlier quoted context omitted.
It's a bit absurd the idea that humans living on earth are going to produce more energy than the Sun. Maybe I'm naive and simple minded. But that just seems insane. If I'm doing the math right, at 2.3% growth = we produce more energy than the Sun in 4500 years. It doesn't matter how many years it is. It's never happening. Just look at how damn hot and inhospitable the sun is. We're not producing more energy here! It'…
And it’s been said that the mass requires to build a Dyson sphere around our sun would necessitate destroying all of the planets: not gonna happen.
The estimates I've seen suggest maybe just Mercury.
Which is good, because Mercury is mostly metal, whereas e.g. Mars is mostly rock and thus not useful for this kind of work
Re: Tidal energy is not renewable
#280Earlier quoted context omitted.
I think the next step is to figure how many exajoules goes to waste heat.
Minus the tiny fraction embodied in global temperature increases, all of it. It's the same reason that the Earth radiates exactly as much energy as it receives from the sun, just a larger number of lower energy, higher entropy photons. What the sun really provides is a source of low entropy.
Wouldn't the earth actually release more energy than it absorbs?
My thinking is that the energy that got absorb in other processes such a photosynthesis is a delayed release.
The energy released must have some time delay. Maybe it all averages out overtime.
Difficult problem I wonder if it is worth answering.