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Comment by choonway | Hacker News Reader

Building a dyson swarm, or even a fraction of it would be the real game changer. Distance from sun to moon - 148,000,000 km. Radius of earth - 6,370 km

fraction of light emitted by sun falling on earth (pi6370^2) / (4pi*(148e6)^2) = approx 4.6e-10 or 0.00000000046 or 0.000000046%

To put it in perspective - if we could collect 100% of the light energy emitted from the sun each day, it would amount to the energy that the earth receives from the sun in 6 million years.

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A better perspective is how much of the energy we already get that we're using. Some quick math tells me that to get 10x our current total energy usage in solar panels would only take 1% of the total surface of the earth, 3.4% of the land area and 56% of the Sahara. So just putting solar panels on deserts across the world and building a worldwide grid would be a much more feasible project than trying to capture directly from the sun. All those solar panels would cost ~13x our world yearly GDP so it's not completely unreasonable either.

https://docs.google.com/spreadsheets/d/1B3Vtm-bk8NIntYc8mZRw...

We are building it - it's called photovoltaics and growing fast.

It is more efficient to use mirrors and reflect the light energy to the destination instead of using it to charge batteries / transmission lines and transport it physically. Perhaps a concentrator on the moon or something?

Giant parabolic concentrators in space also essentially become weapons and therefore no major nation will allow others to possess them. Laser beams to transmit power may be more efficient but same problem with weaponization

It only goes to show that there can be only one winner in space, not that solar concentrators can't be built.

I think the game may have to change a few times already before a Dyson swarm (or even a significant fraction of one) could be built. We're going to need cheap clean power in large quantities to even think about manufacturing something like that.

You have to walk before you can run.

If you want baby steps - we can start building an autonomous factory on the moon to build more solar cells. No need for nuclear fusion.

To put that in perspective though, to create a sphere surface just 2 solar radii away from the center of the sun, you would need to launch ~1.3*10^16 kgs worth of Sputniks into orbit (assuming sputnik would have been enough to convert and transmit sunlight into electricity. This is just the weight of the satellites themselves - add launch vehicles and the placement vehicles, and you're looking at numbers that start to rival the weight of mountains.

you don't need to build solar cells - a reflector will do. and you don't need to launch these reflectors from the earth - launching them from the moon or mercury is much less demanding. you just need to build factories in space.

Even from the moon, we are talking mountain-sized masses. This is way outside the scope of what is possible with current technologies.

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