@CoolWorldsLab

Thanks for watching! Some FAQs...
1. "Isn't a sphere pointless because by this point we'd have fusion reactors?" Fusion reactions require confinement, which means incredibly high pressures and temperatures. For any fusion reactor we build, we have to provide that confinement which costs energy (as well as maintenance). The enormous mass of the Sun provides confinement for free via gravity, so it's pretty hard to beat that! Yet more, 99.9% of the mass of the Solar System is in the Sun, so it's essentially by far the largest fuel reserve. On of top that, 75% of the mass is hydrogen, the optimal element for maximizing fusion efficiency. Why build a fusion reactor when you an essentially perfect one right in front of us?
2. "Isn't it impossible to obtain enough mass to build this stuff?" The mass requirement varies from the mass of Mercury to the mass of Jupiter in the examples cited in the video, so certainly we have enough mass in the Solar System to do it. Dyson calculated that it would take 800 years of Solar luminosity to completely unbind Jupiter. Remember that Jupiter is mostly hydrogen, so it could be fused into whatever elements you want and would broadly lead to a net energy gain in doing so. Now 800 years of continuous energy to build a Dyson sphere might seem like a lot to us, but it's about one fifth of one millionth of the Sun's remaining main sequence lifetime, and that's before doing any stellar engineering to extend its lifespan. So the payback period on your investment is almost instantaneous in cosmic terms, and yields a massive energy profit. Thus we have the materials and motive to do such a thing.
3. "Why would anyone do this?" The video discusses two ideas, habitation and computation (focussing on the latter). But another great point in the comments is that we're essentially already building a Dyson swarm. Every satellite in space harvests solar energy to perform various functions, as we are moving towards millions of satellites in the coming years. It's just a progression at this point towards the Dyson swarm.
4. "What about getting the energy to Earth?" I should have clarified the Earth is basically gone in this picture, dismantled. Beings either digitally upload themselves into the Dyson sphere supercomputer or build a swarm/ring system with habitats instead.
5. "This is a stupid idea". I get it, the idea seems wild. But, it's somewhat the inevitable end point of energy production, as Dyson argued, as well as Kardashev and others. It might seem like science fiction to us, but tell the Victorians we'd have people on the Moon in less than a hundred years and they would they think you were bonkers too! I would think carefully about it before dismissing this idea as stupid - after all this is one of the seminal papers produced by one the most brilliant physicists to ever walk the Earth.
Keep 'em coming and please do share widelt!

@plaguepandemic5651

Man, a civilization living on a Dyson Sphere, facing an imminent apocalypse from an engineering problem they failed to solve in time, would make a great sci-fi novel.

@PunchMcLightning

The fact that you used this clip at the beginning is awesome because that's how I learned what a Dyson Sphere was in the first place and that knowledge always stood with me. I love old Star Trek so much.

@scottbruner9266

9:37 I love how when they collided, it was the STAR, not the sphere, that was destroyed. 😂

@EnneaIsInterested

The real Dyson swarm is a gradual development, so once you have your statites, you can gradually infill. This implies that numerically, once you have an in-space industrial base, it's only a matter of time until the cultural focus is shifted from your planet to the many diverse rotating space habitat communities, indeed, beaming all the energy down to Earth would destroy the Earth, and so cannot be done.

@JohnBrown-no4od

In the book version of "Relics" (novelization of the Scotty/Dyson Sphere episode of Star Trek:TNG), there is no matter within several light years (I believe it was 100) of the star enclosed by the sphere.  In the book, that accomplished two things: First, the sphere builders used all that missing matter to build the sphere, and second, that cleared the area out of any matter that could exert any unforeseen gravitational forces on the sphere.

@NeWx89

I'm glad seeing Stapledon be mentioned. Last and First Men and Star Maker are some of the most extraordinary works of fiction ever written.

@brothermine2292

Also worth analyzing is the "shipstar" featured in Gregory Benford's sci fi novel "Bowl of Heaven."  The structure is a bowl-shaped portion of a sphere, with a hole through its center.  It generates a strong magnetic field to focus the protons of the stellar wind into a fusion plasma jet through the hole.  The jet accelerates both bowl & star, like a giant starship, and the bowl maintains a constant distance from the star while they both accelerate.  Meanwhile, the inner surface area of the bowl, although not as large as the inner surface of a Dyson sphere with the same radius, is immense.

@kurtp2003

I'm surprised there's no mention of using orbital rings as support members for a denser shell.

For those unfamiliar: An orbital ring consists of something like an enclosed particle accelerator or mass driver moving mass in a circuit at higher than orbital velocity such that it counteracts the inward gravitational force on the whole assembly. It does require constant power and maitanence, but the former is easily solved and the latter can be designed out to a large degree. That is, so long as it's designed so no single ring failing can cause the structure to fail.

@sigzil1985

Ooh the transition to the logo in that opening <3

N/A

I am a big fan of Freeman Dysons work (thanks to Isaac Arthur in large part) and REALLY enjoyed this episode. It's interesting that you can actually build a Dyson sphere theoretically, though I think we would do much better to stick with what Dyson really meant and just harness the stars energy with a Swarm of satellites or habitats. a matryoshka brain is another really cool use for a star as well, Great video Cool Worlds! The playing in sandbox mode is why I often get hung up on the simulation Hypothesis. :)

@1edgeman76

OMG, I simply CAN NOT get enough of these episodes!!! You sir and your team are AMAZING. I watch EVERY episode you and your family produce because these little thought experiments are absolutely mind-boggling, thought provoking, and inspirational. Thank you to you and your team for these gems that are educational, provocative, inspirational, and humbling all at the same time in a world full of gross sensory overload for no substantial reason. Truly AMAZING work, as always.

@marcocatano554

This sort of topic entices the imagination. In the end, this may be the most valuable quality of this video. Hats off Dr. Kipping!

@AndrewJohnson-oy8oj

My biggest problem with a Dyson Construct being used for human habitation comes down to three words: Coronal Mass Ejections. The entirety of any CME would hit the Construct full-on.

@davidb2380

Very Interesting video, as usual, but I see some physics problems. OK, the reflected radiation heats the outer layers and causing them to expand. However, in expanding, work is done so the layers become cooler so the ions can then combine forming more neutral atoms. This changes the opacity, so the layers then contract and when that happens, the neutral material gets hotter and they become ions again. The process repeats so the star pulsates. In other words, we have a heat engine.

Second, stars rotate so the equator bulges and we now have non-spherical star. Then because of the von Zipper effect, the outer polar regions being closer to the core will be hotter then those at the equator so we now have a non-spherical star whose outer layers will have a non-uniform temperature. As a result, the Dyson sphere will not be uniformly heated and the reflected radiation will not be uniform. That is Dyson Sphere will reflect back to the star more radiation to its polar region than the equatorial regions. Also, this non-uniformly heated Dyson Sphere will have problems stability wise from the differential heating ? At a minimum, this effect will affect the thickness of the Dyson sphere and the material used.

Third, stars also have stellar winds. Over time, will these winds erode the material of the Dyson sphere ? Stellar winds also carry magnetic fields, which again puts constraints on the material used.

Finally, higher mass stars have outer layers which are radiative, not convective, while low mass stars have convective outer layers. I imagine this too may be a factor, especially since the magnetic fields effect the stellar winds and they are much stronger in low mass stars. It has been a long time since I took courses in stellar interiors and atmospheres, so I would appreciate the comments from a real expert.

@CumminsHider

Contents like this is why I subbed to this channel 8 years ago

@earthknight60

For anyone who wants to take a deep dive into these and other things (such as the starlifting that was mentioned briefly in this episode), pick up a copy of the 1985 book Interstellar Migration and the Human Experience.  I know the name sounds hokey, but it's actually a great collection of research papers from the proceedings of the Conference on Interstellar Migration held at Los Alamos in May 1983.

There are some really interesting and wild ideas in it, with the math and physics broken down and explained.

@z-beeblebrox

Dyson Swarms are my favorite conceptual megastructure, because unlike other Sci Fi megastructure, a Dyson Swarm is immediately beneficial to its builders even when it's only a fraction of the way done. Like, half a space elevator is just an alarmingly close asteroid and a coil of psychotically dangerous feed line. Half an O'Neal Cylinder is just a dumb open tube exposed to the vacuum of space. But if you have 0.01% of a Dyson Swarm? OH NO, you're getting a ton of free energy from that, whatever will you do?! :P

@Satoruu23

this is always a joy to watch, thanks david!

@almartin6824

Of course it’s possible, since 1991 actually….. Dyson designs and manufactures household appliances such as vacuum cleaners, air purifiers, hand dryers, bladeless fans, heaters, hair dryers, and lights.