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What is a Dyson Sphere?

Posted by: roygrif - Tue Aug 31, 2004 8:40 pm
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What is a Dyson Sphere? 
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Post What is a Dyson Sphere?   Posted on: Tue Aug 31, 2004 8:40 pm
Keep hearing reference to this. Any good sites to look at?

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Post    Posted on: Wed Sep 01, 2004 2:45 am
The wikipedia is your friend...
http://en.wikipedia.org/wiki/Dyson_sphere


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Post    Posted on: Thu Sep 02, 2004 1:09 am
Thanks for the link, very helpful.

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Post Re: What is a Dyson Sphere?   Posted on: Thu Sep 02, 2004 1:01 pm
roygrif wrote:
Keep hearing reference to this. Any good sites to look at?


The Dyson Sphere is the ultimate skyscraper. It makes Larry Niven's Ringworld look puny by comparison.
'Nuff said.

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Post Re: What is a Dyson Sphere?   Posted on: Thu Sep 02, 2004 8:03 pm
spacecowboy wrote:
roygrif wrote:
Keep hearing reference to this. Any good sites to look at?


The Dyson Sphere is the ultimate skyscraper. It makes Larry Niven's Ringworld look puny by comparison.
'Nuff said.


not many things can do that. dyson spheres are cool.

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Post    Posted on: Fri Sep 03, 2004 11:34 am
I'm not sure, wether a Dyson sphere would be a good idea.

A Dyson sphere is a sphere surrounding totally a star in its center at all sides - whatever direction you are looking in.

This means that no light, no radiation and to particles can leave for the space. In other words the total energy sent out by the central star will remain within the sphere and cumulated there.

Because of this the heat within the sphere will be increasing until the star collapses or explodes. The light and radiation will be permanently intensified until that event.

In an open system like our solar system all radition etc. can escape into the interstellar space.

So the time characterized by conditions allowing intelligent life within a Dyson sphere will be significantly shorter than in normal open systems.

As an alternative Dyson spheres might be modified providing holes and equipments to focus all radiation, particles etc. wanted to leave to that holes. But even that might be very very tricky if possible at all.

What ways to rescue the idea?

Additionally - do we know significantly that the material of our system is sufficient to build a Dyson sphere and all spacecrafts and tool to build it?



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Post    Posted on: Fri Sep 03, 2004 8:38 pm
well of course all the radiation is trapped by a dyson sphere, that's a good part of the whole idea. you need a LOT of power to run something as big as that, and a star is a good source of energy.

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Post    Posted on: Sat Sep 04, 2004 2:49 am
I remember reading about some theories of how it can't tbe proven that the earth is not in fact a huge hollow sphere and we are on the inside surface. the stars would be lights of cities on the other side, while the sun is half dark and it's spinning, which explains the night day cycle. pretty funny stuff in its naivete(these 'ideas' appeared sometime in the 19th century)

anyways, a dyson sphere around a star would not have a day/night cycle. oh and it would be freaking huge. and unless it is dotted with holes, it'd be pretty hard to evacuate if the star decided to go nova or become a giant.
note that Wikipedia mentions a dyson shell would not have gravity inside to hold the atmosphere, but I think that is wrong because for structural reasons such a shell would definitely be thicker than any planet known and probably denser, which means it would generate a lot more gravity than an earth-sized planet.

I take this idea as more proof that scientists aren't engineers as well :)

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Post    Posted on: Sat Sep 04, 2004 3:01 am
ok, I corrected wikipedia.
found another way to waste my time.
woohoo!!!?!?!?
:roll:

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Post    Posted on: Sat Sep 04, 2004 7:19 am
The energy of the central star will be of use only while building the sphere. After the sphere is ready this energy will be of danger if a certain portion cannot leave for the space outside the sphere.

A day-night-cycle in principle can be established by ´huge satellites orbiting the central star throwing theier shadows onto the inner surfce of the sphere.

The masses of material required for a sufficient amount of natural gravity of the sphere are not given in a system like ours. If the masses were there it would take hundreds or thousands of years to build the sphere. So in our system its utopic.

But consider stars of much less size than the sun and becuase of this providing much less radiation, particles and light - in such cases a Dyson sphere might be the right thing. There might be a certain maximum size allowing a sphere and the sphere might be that special thing required to establish life in the surroundings of such dwarf stars.

I don't remember this moment wether there have been detected exoplanets around dwarf stars already and if so I don't know the distance of this stars. But combinend to Dyson spheres these dwarf stars might be excellent space stations within the inerstellar space.

Waht about this?

What will be the minimal size, radiation, particle stream and light required to make a station of such a system? What are the required distances from the inner side of the sphere to the central dwarf star? What are the amounts of material required? And what time will it take to construct the sphere?

An alternative might be the construction of a sphere around a planet to protect it agianst radiaition etc. - this sphere will be much smaller and easier to build than a sphere around a central star.

May be a little less utopic perhaps.



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Post    Posted on: Sat Sep 04, 2004 4:50 pm
shadow squares wouldn't work nearly as well with a dyson sphere as with the ringworld. as a matter of fact, nothing would work as well with a dyson sphere as with the ringworld i don't think. the only way i can think of a dyson sphere or part-dyson sphere being better than ringworld would be if the inside was all solar panels and you used it as a mass-production facility for antimatter or some equivalently hard-to-make thing.

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Post    Posted on: Sat Sep 04, 2004 5:28 pm
Hello, TerraMrs,

you are sounding like you would prefer Dyson spheres with a hole - the Rinmgworld in principle is really that.

But at least in these open Dyson spheres gravity only could keep a sufficient atmosphere except the inner side is colsed against the open space at its inner side.

To provide the required natural gravity eraurocktchick87 has mentioned elemant 115. There has bes been an argument doubting that but really not very long ago it has been reported that another element has been created in particle accelertors heavier than element 115 with a lifetime of nearly half an hour. The comment was that a supposed isle of stability might be seen at the horizon. This isle of stability contains elements much heavier than element 115 - they might provide the gravity needed for a ringworld. But what amount will be required? And what energies to create this amount? Is there any chance to find it naturally created somewhere?

Very heavy ellements and chances - there is another possible source of natural gravity much more probable to be found. The particle physicists have identified six or eight different kinds of quarks. At least one of them is super-heavy - I don't know how heavy it is but noone can carry it by his hands if I'm right. Additionaly it has been reported that there were two earthquakes insufficiently explained. May be that each of them occured at opposites sides of earth and during a certain period of time. Some scientists detetcted that the explanation of the earthquakes themselves as well as the period of time between them might be superheavy quarks entering earth's surface from space - undetected because of their sub-atomar size. They must have been components of other particles because quarks cannot exist free as a consequence of quantum-physicle laws.

So super-heavy quarks might be an ideal source of gravity for ringworlds - provided they will be found as well as a method to handle them.

There is something else to be added - not long ago too in a particle accelerator accidentally an a strange atom has been created containing a quark normally not to be found in atoms.



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Post    Posted on: Mon Sep 06, 2004 1:54 am
Ekkehard Augustin wrote:
I'm not sure, wether a Dyson sphere would be a good idea.

A Dyson sphere is a sphere surrounding totally a star in its center at all sides - whatever direction you are looking in.

This means that no light, no radiation and to particles can leave for the space. In other words the total energy sent out by the central star will remain within the sphere and cumulated there.

Because of this the heat within the sphere will be increasing until the star collapses or explodes. The light and radiation will be permanently intensified until that event.


FYI, a Dyson sphere still irradiates energy to the outside. From Wikipedia:

Quote:
A star contained within a Dyson sphere would not be directly visible to the outside universe, but the Dyson sphere itself would radiate an equivalent amount of energy in the form of infrared light due to solar heating from within. In addition, since Dyson spheres are composed of solid matter instead of heated gas, the emission spectrum of the Dyson sphere would more closely resemble a black body spectrum than the typical emission spectrum of a star, which has distinct emission peaks.


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Post    Posted on: Mon Oct 11, 2004 1:00 pm
109Ace wrote:
....
note that Wikipedia mentions a dyson shell would not have gravity inside to hold the atmosphere, but I think that is wrong because for structural reasons such a shell would definitely be thicker than any planet known and probably denser, which means it would generate a lot more gravity than an earth-sized planet.
...


Hi 109Ace,

I'm afraid the Wikipedia is right on this. the reason for this is that the gravity inside the sphere cancels itself out.

If you're "standing" on the inner surface of the sphere then the gravity from the part of the sphere below your feet is pulling you down. Unfortunatly, the gravity from the rest of the sphere is pulling you up. When you do the maths, the forces from the sphere cancel out inside it. It seems crazy, but it is correct.

It doesn't matter how dense you make the sphere, it still cancels out. Of course, the sphere doesn't have to have a uniform density. You could make part of the sphere more dense or thicker, and just live there.

The Wikipedia also points out that the gravity doesn't cancel out on the outside. So you could put an atmosphere on the outside, although it would be a bit dark.

Cheers,
Alun.


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Post    Posted on: Thu Oct 14, 2004 9:46 am
Hello, NeuronExMachina,

I know what you have mentioned.

But the Dyson sphere has to transform light, UV etc. to other kinds of radiation located somewhere else at the spectrum - it has to transform it to infrared light.

This means that the material the sphere is made of - the Dyson sphere itself - will be heated and it will remain heated until the central star collapses.

The dark-body-radiation will be the sign that the inner side is heated.

Additionaly infrared is of less energy than light, UV, Röntgen and other short-wave-sections of the spectrum. The difference will be left in the material of the sphere or in its volume as a whole. The high-frequency-wave are coming from the cetral star permanently and each difference will be added to the sum of the former differences. So the temperature inside will be increased. perhaps the material will melt or the sphere will explode one day or something else like this - unless all the differences are caught by something like antennas and transmitted directly without transformation to infrared from the outer side into space by additional antenna-like equipment.

The cumulation will take place - think of what happens if the sun shines onto stones: they store the heat and add the differences. So they become hot more and more until they melt... but they really transform the sunlight to infrared which they send to the environment...



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