
The Best Way to Find Aliens: Look for Their Solar Power Plants - cclark20
http://www.theatlantic.com/technology/archive/2012/10/the-best-way-to-find-aliens-look-for-their-solar-power-plants/263217/
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sxp
>A civilization that built a Dyson Sphere would have to go to great lengths to
avoid detection, either by getting rid of its waste heat in some novel way, or
by building massive radiators that give off heat so cool that it would be
undetectable against the cosmic microwave background, the faint afterglow of
the Big Bang.

So if a civilization were to completely mask itself in the EM spectrum, the
only way to detect them would be to look for gravitational distortions
assuming those can't be masked. A civilization might do this either to hide
from others or because the maximum efficiency of their energy extraction
system would occur when their waste heat matched the background ration. So a
really advanced (and paranoid or efficient) civilization would be
indistinguishable from dark matter.

This brings up another interesting hypothesis: dark matter is actually the
computronium of all of the alien civilizations in the universe that have
achieved a technological singularity. Unfortunately, this hypothesis can't be
tested until humanity gets to the same level.

~~~
kamaal
>>A civilization might do this either to hide from others

Why would they try to hide this from others? Are we trying to hide our
satellites, or our probes that we are sending out?

~~~
patd
One civilization could be at war with another and trying to hide their sources
of energy.

~~~
kamaal
It looks really naive that civilizations so advanced to blot out an entire
star for its energy can't even find a way to co exist in such a vast universe.

But looking at how fellow humans behave with each other. I would say that is
definitely a possibility.

~~~
batgaijin
Show me a future prediction that said we'd be using our advanced contraptions
primarily for viewing porn.

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sbierwagen
Larry Niven, "Bigger Than Worlds" (1974)

    
    
      ...assuming that the galaxy's most advanced civilizations are protoplasmic. But 
      beings whose chemistry is based on molten copper, say, would want a hotter 
      environment. They might have evolved faster, in temperatures where chemistry and 
      biochemistry would move far faster. There might be a lot more of them than of 
      us. And their red-hot Dyson spheres would look deceptively like red giant or 
      supergiant stars. One wonders.

~~~
mediocregopher
Speaking of Larry Niven, my impression after reading Ringworld (in addition to
"holy shit that was good") was that Dyson Spheres were kind of a non-workable,
and that a species who'd advanced far enough to actually make one could
probably just colonize another system anyway.

~~~
sbierwagen
A swarm-Dyson sphere, which is the only kind that can be realistically built,
is incremental. You just keep building habitats in orbit around the sun, until
eventually you capture all the sunlight.

~~~
nitrogen
Clearly a solid Dyson sphere is not orbiting its host star, and could
eventually drift into the star. However, might it be possible to harvest
enough energy from the star to power a propulsion system that keeps the sphere
in place?

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technolem
Won't gravity stop this from happening? Seriously, the shell of the sphere
will be balanced on the outskirts of a gravity well right? So if it moves this
will move the center of the gravity well and both the star and sphere should
fall back towards the center.

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nitrogen
According to Newtonian gravity, an object inside a sphere experiences zero net
gravity from the sphere, and vice versa.

<http://en.wikipedia.org/wiki/Dyson_sphere#Dyson_shell>

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guard-of-terra
It's interesting, but a bit like trying to detect a large and advanced by
looking for products of horse manure decomposing in huge heaps. I think it was
Mendeleev who thought that getting rid of horse shit will be the main problem
of ever-growing cities in XX century.

The need for energy is definite, but the amount and character of such need is
debatable. Maybe civilizations shrink and don't use so much energy? Maybe they
mine million of stars at once? Maybe they get their energy out of thin vacuum?

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tzs
Build your Dyson sphere with large gaps in the galactic plane. Then observers
at most other stars in your galaxy will see your star, and then you don't have
to either build a giant sphere or come up with exotic heat management systems
to avoid detection.

~~~
molmalo
The main problem is that the galactic plane is not really a plane :)

Suppose your star is located exactly in the plane, and its axis is orthogonal
to the galactic plane. Then, defining "up" and "down" as the opposing
directions in that star's axis, you would still have a lot of stars "up" and
"down" the plane.

So, even if you only have only one disk orbiting the star, with a high enough
orbital inclination, that's still visible from a lot of stars.

And of course, there would still exist a plane containing the disk's orbit,
from where the disk eclipses the star.

Even more, the disk itself would still be detectable from other planes,
because it's hotter than the background.

Then, if your civilization wants to keep hidden its existance, you still need
to develop some kind of stealth tech for the sphere. :)

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hollerith
>the sun beams a total of 120,000 terrawatts per day onto our planet. That's
10,000 times the amount that flows through our industrial civilization.

Should be "terrawatts", not "terrawatts per day". (I stopped reading there.
There 100s of 1000s of people who know enough physics never to make such a
mistake. I'll read one of them instead.)

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lurker14
"terawatts", not "terawatts".

~~~
mcantor
'"terawatts", not "terrawatts"', not '"terawatts", not "terawatts"'.

~~~
fractallyte
Although 'terrawatts' is a rather charming play on the word, considering the
context...

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cek
The issue I have with Dyson Sphere's is in 1960 the idea of the singularity
hadn't really been floated. I think it is far more likely that civilizations
either die or upload.

~~~
jerf
It is not clear to me how that is a contradiction. An uploaded civilization
may still desire more computational power, and unless there's an infinite
computation escape hatch in physics (and there is currently not even a trace
of such a thing), that's going to involve getting more energy from the star.
On an exponential growth curve, even improving your civilization's energy
efficiency by a factor of a hundred quadrillion still only buys you a blip on
the scale on cosmic time scales before you start wanting to expand again.

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hcarvalhoalves
Is it just me, or is there someone else who thinks theories like these are so
naive it borders the ridiculous?

Isn't it too pretentious to think that, not only other similar civilizations
_do_ exist (which is a stretch already), but also predict their infra-
structure necessities _and_ what kind of solution they are going to come up
with?

I known I'm nobody and Mr. Dyson is a Nobel-prize grade genius, but come on...
this is (much) more fiction than science.

PS: Let the downvotes commence.

~~~
sbierwagen
If they want to affect the environment, or perform computations, they have to
use energy. If they have to use energy, they have to get energy from
somewhere. Hydrocarbons don't last for more than a couple centuries. Heavy-
element fission will get you another century. Light-element fusion will get
you another ten thousand years.

Whither comes the energy for a million year civilization? Should they _ignore_
their star? Just let all that power go streaming by?

(Dyson won theHeineman Prize, Harvey Prize, Wolf Prize, Templeton Prize,
Pomeranchuk Prize, Fermi Award, and the Poincare Prize; but did not win a
Nobel.)

~~~
hcarvalhoalves
Maybe you proved my point. Just look at how many _if_ s this theory depends
upon.

1\. That a civilization similar to ours exists 2\. That such civilization
exists in the same time frame as us 3\. That such civilization's demands on
energy are similar to ours 4\. That such civilization expands enough to face
energy shortcomings 5\. That the best source of energy such civilization finds
is a nearby star 6\. That they arrive to the same conclusion as Mr. Dyson
about the best way to harness the power from this star (the biggest pretension
by far in my opinion) 7\. That they manage to build it

A very interesting chain of propositions, but really? I find amusing that are
people willing to take this more seriously than a simple imagination/future
prediction exercise.

We can't even reliably predict how _our own civilization_ will look like in a
matter of _decades_. Now imagine how naive is to think we can predict which
problems hypothetical begins similar to us are going to face, let alone
predict a particular the solution they are going to come up with.

~~~
sbierwagen
Son, you don't have to start jumping up and down and gibbering excitedly about
the singularity. This ain't hard.

All life uses energy. All civilizations will always use energy, because they
are made of life forms. (biological or silicon-- who cares)

If civilizations grow steadily, then their need for energy will grow steadily.
If they don't flame out, then they'll need to expand beyond their host planet,
and intercept more solar energy, until eventually all sunlight is captured,
and you've got a Dyson sphere.

If civilizations grow until they hit a threshold, then stay steady-state for
the rest of the universe's lifespan, then we'll only be able to detect them if
the threshold is pretty big-- if they just stay on their planet, then they'll
be hard to spot, without really big space telescopes.

~~~
hcarvalhoalves
Thanks, but again, you're explaining me the reasoning behind it (I _get_ it,
otherwise I wouldn't be arguing it), and losing the point about why I say it's
pretentious in the first place.

Intelligence and wisdom are different qualities.

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lutusp
Let's be realistic. A civilization so advanced as to be able to capture the
entire energy of a star, probably also has energy alternatives, and probably
wouldn't want to attract the attention of lesser beings (like us) by trapping
a star's output in a detectable way.

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aplusbi
Why wouldn't they want to attract the attention of lesser beings?

~~~
lutusp
> Why wouldn't they want to attract the attention of lesser beings?

Because they might attract the attention of greater beings.

~~~
kamaal
>>Because they might attract the attention of greater beings.

As a life form we don't seem to be taking any precautions to 'hide' from
others.

Why are assuming others would like to 'hide'?

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Haplo
It could very well be that the only civilizations that still exist are the
ones that are good at hiding. All the others (even if they are the big
majority) might have been destroyed after giving a signal of life/existence.

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goombastic
It is equally likely an advanced civilization would have found out ways to
engineer/create energy unlike how we imagine it. It might even seem irrational
to us, magical, impossible even.

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w1ntermute
Solar power? I'm pretty sure they'd be using nuclear fusion.

~~~
sbierwagen
You're not thinking very big, or in terribly deep timescales. There's not a
lot of easy-to-access hydrogen in the solar system, and most of it is at the
bottom of steep gravity wells. (The gas giants)

On the other hand, if you put your solar collector well inside Mercury's
orbit, where the solar flux is dramatically higher, then you get plenty of
power, without having to maintain and fuel a reactor.

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treelovinhippie
About time they started looking for Dyson Spheres!

