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Dyson Spheres






Does Dyson Spheres exist?
Yes
42%
 42%  [ 3 ]
No
14%
 14%  [ 1 ]
I don't really know what to think :/
42%
 42%  [ 3 ]
Total Votes : 7

HeavyVanilla
Have you ever heard about these hypothetical universal megastructures?
If so, do you think they exists? Is it even possible to build them?
Would a civilization need to build it, if it had the technology?
Have hypothetical aliens already built them?

What do you think?

Source: http://en.wikipedia.org/wiki/Dyson_Spheres
ocalhoun
HeavyVanilla wrote:
Have you ever heard about these hypothetical universal megastructures?

Of course.
Quote:

If so, do you think they exists? Is it even possible to build them?

I'd suspect its possible. It would start as just a few energy-gathering platforms orbiting a star. More platforms would be added, the existing ones would be expanded, some would be connected with each other... Finally, the star would be fully enclosed.
Quote:

Would a civilization need to build it, if it had the technology?

If they needed power on a cosmic scale for some reason... (Perhaps the energy to construct custom-made black holes for wormhole travel? Though for that, I suspect they would need several spheres, as well as an ingenious way to manipulate that much power.)
Quote:

Have hypothetical aliens already built them?

Supposing there are hypothetical aliens, and given the age and size of the universe... probably.
Xrave
The material needed to build such a thing is almost the size of the moon. I thought about that once while dazing off on a train - if one can build a steel structure that encases the earth so that it hovers a kilometer off from the ground, held there by the equalization of the earth's gravity. It's a probable theory, but it needs a lot of material. I suppose the energy output is worth it though, if you do make a sphere of solar panels go around the sun. but I don't think any wire would be thick enough to transfer all that energy Razz
ocalhoun
Xrave wrote:
but I don't think any wire would be thick enough to transfer all that energy Razz

If you can build something the size of a Dyson sphere, you can build some very huge wires...
If the energy is converted to a stable, coherent, low frequency during collection, huge waveguides could be used to transmit the energy, which would also be convenient when the time came to channel the energy, though it would be inconvenient for storing the energy.

For extremely high power applications, waveguides are much more practical than wires.
tchaunt
Xrave wrote:
The material needed to build such a thing is almost the size of the moon. I thought about that once while dazing off on a train - if one can build a steel structure that encases the earth so that it hovers a kilometer off from the ground, held there by the equalization of the earth's gravity. It's a probable theory, but it needs a lot of material. I suppose the energy output is worth it though, if you do make a sphere of solar panels go around the sun. but I don't think any wire would be thick enough to transfer all that energy Razz


The spheres aren't supposed to be giant layers of metal-like material. Quite the opposite, they are supposed to be made up of small satellites that are arranged in a spherical manner around the star. These satellites won't literally collect all of the star's energy, just most of it. Check out the pictures on the wiki page for a better explanation.
ocalhoun
tchaunt wrote:
These satellites won't literally collect all of the star's energy, just most of it.

... depending on the implementation... It would start that way, but it could theoretically progress to the point of 100% coverage, though it would probably be more efficient to get 50% coverage of two different stars.
Gagnar The Unruly
According to Wikipedia, Dyson himself thought that 100% coverage was unrealistic. A single ring seems like the simplest, most effective option. Adding more satellites & orbital pathways increases the chances of collision.
ocalhoun
Hm... thinking along those lines... a complete sphere around anything... could it work? The ring around the axis of rotation could be held up by being in orbit, but supposing we call that the equator, what about the poles? Would they have to be held up only by the rigidity of the structure, or could the entire contraption be made to rotate along multiple axes so that all points could be held up by their momentum?
Bikerman
Err....what are you measuring rotation against - what is the 'fixed' point?

PS - scrap that - the fixed point is obviously the central sun (DUH!).
Wiki has the following:
Wiki wrote:
If assuming a radius of one AU, then the compressive strength of the material forming the sphere would have to be immense. Any arbitrarily selected point on the surface of the sphere can be viewed as being under the pressure of the base of a dome 1 AU in height under the Sun's gravity at that distance. Indeed it can be viewed as being at the base of an infinite number of arbitrarily selected domes, but as much of the force from any one arbitrary dome is counteracted by those of another, the net force on that point is immense, but finite. No known or theorized material is strong enough to withstand this pressure, and form a rigid, static sphere around a star. It has been proposed by Paul Birch (in relation to smaller "Supra-Jupiter" constructions around a large planet rather than a star) that it may be possible to support a Dyson shell by dynamic means similar to those used in a space fountain. Masses travelling in circular tracks on the inside of the sphere, at velocities significantly greater than orbital velocity, would press outwards due to centrifugal force. For a Dyson shell of 1 AU radius around a star with the same mass as the Sun, mass travelling ten times orbital velocity (300 km/s) would support 99 (a=v2/r) times its own mass in additional shell structure. The arrangement of such tracks suffers from the same difficulties as arranging the orbits of a Dyson swarm, and it is unclear how much energy would be consumed ensuring the velocity of the masses was maintained.

source - http://en.wikipedia.org/wiki/Dyson_sphere
(the original contained some spelling errors which I have corrected since I abhor Americanisms - travelling has 2 ls Smile )
Gagnar The Unruly
Bikerman wrote:

(the original contained some spelling errors which I have corrected since I abhor Americanisms - travelling has 2 ls Smile )


There are more of us than there are of you! 'Traveling' stands!
Bikerman
Gagnar The Unruly wrote:
Bikerman wrote:

(the original contained some spelling errors which I have corrected since I abhor Americanisms - travelling has 2 ls Smile )


There are more of us than there are of you! 'Traveling' stands!

The old 'Argumentum ad populum' fallacy cuts no ice with me buddy. Who invented the damn language anyway? A few colonists travelling to a far land doesn't change the bleedin' spellin' Smile
ocalhoun
Rolling Eyes
Dialects aside, could a complex rotation along more than one axis cause a Dyson sphere to be supported orbitally the same way a ring could be held up with a simple rotation?
My mind is at the breaking point trying to visualize the forces applied to various parts of the sphere while spinning in both X and Y, but I'm leaning towards saying that it would support it, at least most of the way.

And I'm not sure about assuming it would be built at a distance of 1 AU... I would think that the best plan would be to build it as close as possible, which would depend mainly upon the heat resistance of the materials used. Most materials should be able to handle it hotter than 1 AU, allowing the construction to be smaller, more efficient (how close it can be built would also depend on how well it can absorb energy), easier to support, and use far less materials.
Xrave
that'd be extremely effective, multi-layering of solar panel satellite rings... but said satellites are under constant danger of outer-space bombardment, comets and space garbage that could smash into one and destroy the whole thing...
ocalhoun
Xrave wrote:
that'd be extremely effective, multi-layering of solar panel satellite rings... but said satellites are under constant danger of outer-space bombardment, comets and space garbage that could smash into one and destroy the whole thing...

A good early warning system and a way to direct concentrated solar energy should take care of that.
Xrave
ocalhoun wrote:
Xrave wrote:
that'd be extremely effective, multi-layering of solar panel satellite rings... but said satellites are under constant danger of outer-space bombardment, comets and space garbage that could smash into one and destroy the whole thing...

A good early warning system and a way to direct concentrated solar energy should take care of that.


how would you expect to detect, and then direct concentrated solar energy onto a bolt or a nut 3 centimeters in diameter?
ocalhoun
Xrave wrote:

how would you expect to detect, and then direct concentrated solar energy onto a bolt or a nut 3 centimeters in diameter?

To detect it, more advanced forms of our familiar technology of radar would work, it would simply be a matter of making it more powerful and more sensitive, which we can assume people advanced enough to build something so large would be capable of.

As for directing the energy to destroy it:
1: Use the star's power directly, using an array of mirrors or fiber-optic-like devices to redirect a large portion of the star's power to the small area of the bolt.
2: Use the power gathered from the star to operate some very powerful lasers/masers, which can be aimed at the bolt.

If you're going to bother making a Dyson sphere, you obviously already have the capability to gather and manipulate the huge amounts of energy produced. All you need is a way to direct enough of that energy into the approaching object.
Xrave
meh meh ^^ sounds waaaay far into science fiction for me.
ocalhoun
Xrave wrote:
meh meh ^^ sounds waaaay far into science fiction for me.

Often the only difference between good science fiction and science fact is time.

Landing men on the moon, having a global communications network, and having working machines too small to see with the naked eye would all seem very science fiction-ish in their own time.
Xrave
It's still hard to imagine though...
The-Nisk
This should really be in the science fiction thread.

Nevertheless, I love sci-fi, so here goes.
It would take some rather extraordinary materials, and some even more extraordinary engeneering, as for the applications....it gets really interesting there.

The actual solar panels would have to be improved drasticaly to be able to handle the intensity of sunlight (can you think of a material that handles photoelectric effect well with minimum heat output?), also the method of power outputing would have to be a pretty good one. But how exactly are you going to extract energy from something which rotates about a star? You'd have to build a station(s) that orbit the sun with the panels and make use of it's power output. These panels would require some pretty powerful shielding with rocket (or some other advanced equivalent) stabilizers should they get knocked off the orbit by space debris (the shielding would have to be strong enough to resist such debris). Again if you have panels that can stabilize themselves and resist projectiles, how are you going to output power energy from such a device? I think a new method of energy transfer would be required, if sure some of you physics geeks can imagine the warious ways without me mentioning wormholes (probably some application of quantum wackiness mentioned by indi) etc.

I see someone sugested a concentrated ray of light as a defence mechanism....I would like to point out that 'things' can move pretty damn fast in space...that plus the fact that they can also be pretty big.....so even if we have technology that can handle real quick calculations, there is the limited speed of the physical adjustments (spheres rotations etc) to utilize such a weapon...and if the object is big(and we can never tell how big it can be) we wont be able to destroy it in one shot, then there's also the range of such a weapon.....it's just impractical/difficult.
However a good old sci-fi 'force-shield' might provide the answer, there are already some cold-plasma force shields in research....eventualy we might have one that can be used against projectiles.

As for what would you do with soo much energy? well someone already mentioned wormholes (although I do not think that blackholes will be used). Then there's time travel, and perhaps multiverse travel (that would be awesome but could be impossible), dimensions i duno, my knowledge of physics is yet very limited, my imagination however isn't. Rolling Eyes
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