How long before our civilization reaches Type I, Type II, Type III civs

[Sayonara]

Solar flares consist of hot ionised gas rushing out from the sun. They have to cover 150 million kilometers to get to Earth orbit, which takes quite a while. Warning travels at the speed of light, and even with today's technology, we get warning 20 to 48 hours ahead of a flare. In our Dyson swarm civilisation, we can expect even more than that, and a chance for habitats to move out of the way. If that is insufficient time, then there is no reason for the habitats to swarm at 1 AU. They could orbit further out and get more warning. This would even permit more habitats in orbit. It would be easy for an advanced technology to compensate for lower energy flux with more collectors.

Your argument here is actually enough to convince me. Although I have not checked your figures, I am inclined to agree that with sufficient warning (an important caveat) components in a swarm could move out of the way of an impending flare. Because of their arrangement it would not even be necessary for all habitats to constantly monitor the sun at all times - they can inform each other of worrying telemetry.

OTOH, I think it is quite likely that either the shell or swarm civilisation might be able to deflect the matter from such an ejection with some degree of confidence and ease (and probably style too).

 

This statement is based on the missile hypothesis, and is used today by the military as an excuse to spend megabucks on developing anti-missile defenses. If I were a terrorist wanting to explode an H bomb in Washington, I would not deliver it by missile. My delivery vehicle would be a battered old Volkswagon Kombi van.

That would do significantly less damage than an air-burst. If the bomb is on or in the sphere, the area of total devastation will be many times smaller. In fact, much of the precious radiation of doom will be directed out of any breaches into the void of space, and inward towards the star (although there is an unknown quantity here, because the gravitation system being employed on the shell could affect the explosive pattern).

 

If an H bomb attack were planned against a Dyson sphere, the individuals perpetrating that atrocity would get more impact by dismantling the bomb and reassembling it inside the sphere. It would do serious damage all right.

No it would not. You are talking about a structure with a surface area of over 2.5x10¹⁷ square kilometres. The most powerful nuclear weapon ever detonated was dropped with a detonation altitude of 4km and resulted in a mushroom cloud of about 30-40km across, and a fireball of 4.5km radius. This was the single most powerful device ever used in all of human history, yet much of its power was wasted as radiation spilling into space.

 

Even assuming an effective airblast radius of 1000km, if such a device were used against a Dyson shell the affected zone would be 0.00000000125% of the total surface area. An expensive way of inflicting a pinprick wound.

 

In fact, it is worse than that. A highly advanced technology would likely have anti-matter bombs!

What happened to using the physics of the present? You cannot have your cake and eat it. Antimatter bombs are nowhere near as probable as "lots of thrusters".

 

The problem is that if you carry that view into a science discussion, you end up discussing science fiction, or even fantasy. If something is theoretically impossible today, we cannot simply assume that advanced physics will find a 'magical' way to do it tomorrow. I think it is valid to postulate advanced technologies that are marginally possible in theory only. However, to postulate advanced technologies which are theoreticaly impossible by today's understanding .....well why not postulate a magic wand while you are at it.

Bullpoop. We are discussing a civilisation which is capable of grinding up the entire solar system, and recycling it into a vast megastructure the very idea of which - shell or swarm - would turn the master-engineers of a thousand planets pale.

 

Yet on the one hand you state that such a civilisation "would likely have" antimatter bombs, despite the obvious physical problems that come with that technology, yet you poo-poo the idea that this civilisation will know how to apply the principles of thrust, or indeed that they might have had a good long think about that before they started to build the structure that we have already pre-supposed.

 

Your goalposts must be spaced equally with everyone else's, Lance, and they should stay firmly rooted in the ground.

 

For the record, it was not me but Reaper who said "Even if we do assume that this hypothetical civilization has found a way to mass produce antimatter bombs..." etc.

 

As a side note, I think you are on dangerous ground if you are going to start poo-pooing Arthur C Clarke on the basis that he wrote sci fi.

 

To be honest I don't know why we are still discussing the shell wrt these arguments. There are much better objections, for example the strength argument I mentioned earlier. If you do the calculations you will see that they turn out to be ludicrous (although there may eventually be a way around this, since you have enough empty space in the shell to build a "webwork" of support structures).

 

I think that for the purposes of this thread we should write off the sphere and assume a swarm for Kardashev-II, and then we can all move on with the topic.

[SkepticLance]

To Sayonara

 

First

Thank you for the gracious capitulation on the first point. I always admire people who can do that, far more than the more common variety of human irk who cannot ever admit barking up the wrong tree. Good for you!

 

Second - re H bombs.

You are correct in saying that an H bomb blast in or on a Dyson sphere would be trivial relative to the entire structure. It would still kill millions of people, though, and the inhabitants might not consider that trivial. So the answer depends on whether you are talking relative damage to the sphere or absolute damage in millions of deaths.

 

Third - anti-matter bombs.

Perhaps I have not made my point very clear. I think that speculation is fine if it sticks to what might be possible in theory. If something is totally impossible according to currently understood science, I think that kind of speculation is inappropriate to this forum.

 

If you have anti-matter, then making a bomb is dead easy. The problem is getting the anti-matter in the first place. Currently we make it in accelerators an atom at a time. Could a future civilisation make enough (or find a source somewhere else) to make a bomb? Actually, I don't know. It is possible in theory, though, which makes it a candidate for speculation.

 

Fourth - is a Dyson sphere possible to move?

I could be wrong. However, I think this 'possibility' is very tenuous. You talk about moving a Dyson sphere. It would mass as much or more than our entire solar system. Have you calculated how much reaction mass you would have to eject to send it moving one way? And the same again to stop its movement relative to the sun? The only practical way I could see anyone moving a Dyson sphere, even to a very minor extent is to use 'the physics of the impossible' which puts it outside the defined area of speculation.

 

 

Fifth - poo-pooing Arthur C Clarke

Please do not misunderstand me. I admire his work. I have read most of his novels and enjoyed them. However, I have a very clear picture in mind of the difference between fiction and fact. I read fiction with great pleasure, and on the science forum I discuss fact (or speculations hopefully based on fact).

 

Finally

I agree with your last paragraph.

Cheers.

[Pangloss]

No. A Level II civilization almost certainly will use Unobtanium.

 

Nah they'll use scrith. Much easier to work with; all you need is an appropriately-sized cziltang brone.

[Mr Skeptic]

I'd use solar sails to move my Dyson sphere.

[Sayonara]

Thank you for the gracious capitulation on the first point. I always admire people who can do that, far more than the more common variety of human irk who cannot ever admit barking up the wrong tree.

You are quite welcome.

 

You are correct in saying that an H bomb blast in or on a Dyson sphere would be trivial relative to the entire structure. It would still kill millions of people, though, and the inhabitants might not consider that trivial. So the answer depends on whether you are talking relative damage to the sphere or absolute damage in millions of deaths.

But remember why you raised this point; you were exploring the vulnerability of the shell to disasters natural and man-made. Although you stated that a swarm could evade natural disasters such as solar flares, you omitted to mention how they would be affected by an H-bomb attack such as that which might threaten the sphere.

 

In the case of a weapon with the explosive power I used above, the death toll in a swarm habitat would be about the same. However the death rate and damage rate would both be 100%, on account of the habitat being utterly destroyed. This is a much more serious loss to the civilisation if that habitat contained unique social elements.

 

Perhaps I have not made my point very clear. I think that speculation is fine if it sticks to what might be possible in theory. If something is totally impossible according to currently understood science, I think that kind of speculation is inappropriate to this forum.

"More thrust than I can imagine" is not totally impossible according to currently understood science, though, is it? I shall demonstrate below.

 

Is a Dyson sphere possible to move?

I could be wrong. However, I think this 'possibility' is very tenuous. You talk about moving a Dyson sphere. It would mass as much or more than our entire solar system. Have you calculated how much reaction mass you would have to eject to send it moving one way?

You don't need any reaction mass. You have portal stations at regular intervals across the surface of the shell, in a grid pattern. These stations channel radiation from the star out through the shell, up a tower which supports a solar sail. There is constant "outward pressure" on the sails, and this can be directionally biased as required by temporarily closing the relevant pattern of portals.

[insane_alien]

going back to the hbomb, in a dyson swarm it could be much more destructive than on a dyson sphere.

 

1/ the dyson sphere would hold up well because of the enormous strength needed already, damage to the sphere would be minimized

 

2/ (this is my main point) debris from a unit of the swarm could affect other units and so on. we are already seeing a similar issue on a more local scale. with all the space junk we have up here scientists believe it is approaching a 'critical mass' where the number of collisions will grow exponentially due to existing space junk colliding and breaking up. now, if a dysons swarm is to capture all of the suns energy then that means its going to be relatively densely packed. one little hbomb could trigger a cascade of collisions each making the situation worse.

 

of course, i fully expect a civilisation that has actually built a dyson swarm to have mechanisms in place to prevent such an occurence

[SkepticLance]

To Sayonara

 

I guess I got sidetracked on the security issue. You are correct that an H bomb would be a disaster to a swarm as well as a sphere. I think we can agree that bastards with nuclear weapons are catastrophic in any society.

 

I have to admit also that I had not considered the solar sail possibility in relation to moving a Dyson sphere. You would not use sails, of course, since the entire inner surface of a sphere is a kind of sail. What you would need is a means of altering the reflectance/absorbance of that inner surface. A degree of thrust could be obtained by absorbing charged particles from the solar wind, versus reflecting them, or perhaps channeling them to the outside. So one side of the sphere becomes equivalent of a mirror and the other similar to a black absorbing surface.

 

I do not know how much thrust you could get that way. Would it be enough to move something weighing more than the entire solar system? I do not know.

 

To insane alien

 

A point you may not have taken into account. The Dyson swarm does not need to be dense. In fact, for safety reasons, it is probable that a large minimum distance be set between habitats. However, a thinly spread swarm that occupies a space between (say) 1 to 5 AUs from the sun could still intercept pretty much all the energy while still staying well away from each other. The habitats further out could use widespread collectors or concentrating mirrors to take in the more diffuse solar energy they need. Assuming they were not burning deuterium instead.

[insane_alien]

space junk isn't dense either. but there will be a minimum density for capturing all of the suns rays practically (you don't have a few masssive ones out by pluto only able to gather a few watts per square meter. and no tiny ones getting incinerated close to the sun)

[Sayonara]

I do not know how much thrust you could get that way. Would it be enough to move something weighing more than the entire solar system? I do not know.

I have no idea how much thrust you could generate to be honest, but we could do some rough calculations which would give an approximate range. Adjustments to correct variances in a 1AU radius will not have to result in immediate changes so we can afford to be lazy with our accelerations.

 

[edit]Turns out that if you start building your portal stations at the pole and place them at 100km intervals along a circumference, then base the other circumferences off a 100km spacing along the equator, and each portal has a 100m² aperture (which is conservative!), your energy interception due to those portals is about 3 exajoules per second (3x10¹⁸ joules). Not sure how that translates into light pressure, but it's a whopping great energy boost for whatever storage cells you are using when the sails aren't being pushed.[/edit]

 

I would advocate channelling energy outside the shell to interact with sails, rather than using the inner surface, for two reasons.

It doesn't use up as much valuable shell surface, which can be put to better use. Also, because the light passing through portal stations can be reflected about the place in any way we see fit, the sail area supplied by a single portal could be many times larger than the respective area of shell which is occupied by that portal.

 

Maybe we should have a "Dyson Mechanics" thread, since this topic often seems to usurp the point of other threads.

Edited July 11, 2008 by Sayonara³

[Deja Vu]

Oooo, I love this topic, allow me to add something to this here.

 

On constructing the dyson sphere (or swarm, which ever you prefer), one has to remember that not all of the mass in the solar system would be suitable for building. Most of the matter in the solar system is hydrogen, with Jupiter being more massive then all of the planets in the solar system combined. So, the Dyson sphere itself will not be as massive as some think.

 

 

The entire mass of all the planets in the solar system is estimated to be about only .135% of that of the entire solar system, with the Sun being the bulk of that. Jupiter is about 90% hydrogen, and so as such is unusable for building. Most of the usable material would come from the 4 inner planets, whose combined mass is calculated to be about 1.11822x10^25 kg. Please correct me if I'm wrong here, I'm not using a very suitable calculator for this estimate, though it does seem about right since Earth is about 5.97x10^24 kg and Venus about 4.88 x 10^24 kg respectively (Mars and Mercury have masses of at least an order of magnitude lower). The asteroid belt has less mass then that of even a small planet, so I won't include it. Anyways, 1.11822x10^25 represents all of the usable matter in the solar system needed to construct this dyson sphere.

 

I don't have time right now to calculate how thick such a structure would be, I'll do it later, but given it's mass it will be very difficult to move or adjust the thing, if we assume the Sayonara's figure at face value. The energy needed to change it's velocity by, say 20 m/s, would be about 1.47775x10^28 Joules, using the formula E=1/2mv^2. Solar sails simply wouldn't be enough.

 

Keep in mind though that this is a very simplistic calculation, I'm sure there are other things we would have to worry about or take into account.

 

Given this, it would be much more practical to build a swarm. SkepticLance's idea isn't too bad compared to building a sphere.

[SkepticLance]

To Deja Vu

 

Nice numbers. It is always good to see things quantified.

I would not write off Jupiter too quickly, though. It, and the other gas giants, do contain a lot of Hydrogen. However, we still do not know what lies beneath the surface, and there might be rocky material equivalent to thousands of Earths. At least!

[Deja Vu]

To Deja Vu

 

Nice numbers. It is always good to see things quantified.

I would not write off Jupiter too quickly, though. It, and the other gas giants, do contain a lot of Hydrogen. However, we still do not know what lies beneath the surface, and there might be rocky material equivalent to thousands of Earths. At least!

 

Thank you.

 

On the subject of Jupiter's core, there are many competing theories as to what it is made out of. As for it's mass, it is not equivalent to thousands of Earth's unfortunately, the mass of it's core is at most about 15 times the Earth's mass from what I've read. Even then though, that's still a substantial amount.

 

The composition of it's core is mostly debated, with some saying that it is rocky, and others saying that it might be made of ice or of organic material. They all agree though that the core is solid.

 

Regardless, I think it is very unlikely we will use any of Jupiter's mass in a Dyson sphere. The pressures near the core are enormous, and in my opinion it would be easier to mine a star then to take material out of a gas giant's core. It's moons might be used though.

 

And another thing, why bother? It would just simply add more mass and make it even more difficult to maintain.

[Sayonara]

I don't have time right now to calculate how thick such a structure would be, I'll do it later, but given it's mass it will be very difficult to move or adjust the thing, if we assume the Sayonara's figure at face value. The energy needed to change it's velocity by, say 20 m/s, would be about 1.47775x10^28 Joules, using the formula E=1/2mv^2. Solar sails simply wouldn't be enough.

 

Alternatively, at a push, you could harvest the entire power of the star's radiation, which would be just under 4x10²⁶ watts at the surface of the shell. If you had some way of buffering this energy for later use, you would be able to release it to provide plenty of thrust when necessary.

[Deja Vu]

Alternatively, at a push, you could harvest the entire power of the star's radiation, which would be just under 4x10²⁶ watts at the surface of the shell. If you had some way of buffering this energy for later use, you would be able to release it to provide plenty of thrust when necessary.

 

That's precisely what I was thinking. To store it though you would need a solid or a liquid fuel that has a very large energy density. This is of course assuming that the collectors on such a sphere have 100% efficiency, which of course implies that a real life dyson sphere would collect less energy then is available from the sun.

 

I should note that I just realized that I made an error when calculating that figure above, I had added an extra digit somewhere. The correct figure should be 2.236x10^27 J. Doesn't change difficulty of moving one though.

 

 

Also note that the thrust generated from solar sails alone would be wholesomely inadequate to keep the sphere from crashing into the sun. Should the gravity of an object, say, a gas giant or a small star, perturb the dyson sphere too much, you would also have a tough time trying to adjust it.

 

The best solution, IMO, would be to just simply use less mass then is available for the construction of the Dyson sphere and/or to use the gravity of other bodies to help keep it adjusted.

[SkepticLance]

There is a very simple way of reducing the mass needed for a Dyson sphere. Simply use the advanced genetic engineering techniques no doubt available to modify humans, so that they can live in weightless conditions with no health detrement. If there is no need for Earth level gravity, a Dyson sphere could be made of very thin material.

[Deja Vu]

This thread got me thinking about the possible engineering challenges that a Type II civilization would possibly face when building a Dyson sphere, so I took the time to do more calculations. I will gloss over the math and just post the solutions to save space. If you want to look over some of the math, just let me know. Maybe you can correct any errors you might find, if there are any.

 

First there are stability issues. As I stated before you would need a great deal of energy to provide the thrust necessary. However, it is entirely possible to use gravity to help keep the sphere stable. Since the sphere will be enclosed around the sun there will be no net force between the sun and the sphere, but that doesn't necessarily mean that the sphere won't crash. What I've been thinking about though is using the gas giants to help keep it stable. I have not done any serious calculations on this since they tend to be messy and in some cases beyond what I can do, but I don't think it is unreasonable that, given proper planning and maintenance, you might be able to keep it stable for millions of years. This would eliminate the need for thrusters if this civilization found a way to use the gravitational force of the gas giants for stability.

 

But that's where the good news ends I'm afraid, because everything else seems to make the possibility of living on one staggeringly improbable.

 

For one, the gravitational pull of this object once it is built. As I said before, since the sphere encloses the star, there is no net force between the sphere and the star, and as such we can just treat them both as a single object. Since you guys proposed a distance of 1 AU from the shell to the sun, I used that as my guide. Standing on the surface of one at that distance, the acceleration due to gravity will be about .059 m/s^2. This is, of course, much lower than the force of gravity you would experience from standing on the Earth. It doesn't really get better from the orbit of Venus, or even the orbit of Mercury. For an acceleration of 1 m/s^2, the shell would have to be about 4.20x10^10 meters from the sun (about 42 million kilometers). For an acceleration due to gravity similar to Earth, it would need to be about 11 million kilometers away. Unfortunately, it would be at that point probably glowing red hot and not very suitable for living on it.

 

For amusement, I wanted to see what would happen if I decided on keeping it 1 AU away from the sun and then trying to produce a significant centripetal force. In order to produce a gravitational pull similar to Earth, you would have to spin it. Really, really fast. It's velocity would have to be about 40 times faster than the velocity of the Earth itself while it moves around the sun. And that's only around it's "equator", never mind what happens elsewhere.

 

There is a very simple way of reducing the mass needed for a Dyson sphere. Simply use the advanced genetic engineering techniques no doubt available to modify humans, so that they can live in weightless conditions with no health detrement. If there is no need for Earth level gravity, a Dyson sphere could be made of very thin material.

 

It actually wouldn't matter how much mass you put into the dyson sphere, because it is very insignificant compared to the mass of the sun. So it's okay to assume the sun's gravitational pull. At a distance of 1 AU, I agree that you certainly would need genetically modified humans, probably to the point where they won't be humans in the recognizable sense! The gravitational pull would be much too low.

 

 

Now, you would encounter less problems if you decided just to use it for power generation. But to live on a Dyson sphere would bring up a great many more problems to solve. The problems listed above aren't even the tip of the iceberg, such as how strong the sphere itself would have to be in order to stay intact, etc. etc.

Edited July 13, 2008 by Deja Vu
multiple post merged

[SkepticLance]

To Deja Vu

 

Thank you for those comments. They meet the ultimate criterion for extreme wisdom. They agree with my own thoughts! (Just kidding)

 

I had concluded right at the start that a space habitat was a better bet. You won't need to adapt humans for microgravity, since you can spin a habitat for artificial gravity. If enough population needs to be housed, you end up with a Dyson swarm.

 

However, the habitats still retain the great virtue of mobility. If something serious enough happens, which is likely if we look at long time spans, such as the sun becoming unstable, then all those habitats can move off to find another home. Our sun is destined to swell into red giant status, and a mobile habitat that can move into a more distant orbit would mean survival. Or the move might come just from a difference of political opinion.

[Sayonara]

Now, you would encounter less problems if you decided just to use it for power generation. But to live on a Dyson sphere would bring up a great many more problems to solve. The problems listed above aren't even the tip of the iceberg, such as how strong the sphere itself would have to be in order to stay intact, etc. etc.

 

Yes, the shell is a problematic structure alright when considered as a habitat. But this thread is about Kardashev scale civilisations, which involves energy utilisation, so a shell still has its uses here. You don't necessarily have to have everyone living on it or in it!