字幕表 動画を再生する 英語字幕をプリント What would happen if you put a couple of physicists in a room with a rope, a box and a black hole? They might come up with a plan to power the Earth for centuries. This is WHAT IF, and here's what would happen if we could harness the energy of a black hole. Black holes aren't something you come across every day. To make a black hole of your own, you'd have to squeeze a star ten times bigger than our Sun into a sphere the diameter of New York City. Black holes are very dense and have enormous mass. And as we know from a famous Albert Einstein equation, everything that has mass also has energy. In the case of a black hole, we're talking a whole lot of energy. Theoretically, we could collect all that power without any super-advanced new tech. And if we did, we'd have access to more energy than we'd know what to do with. But of course, it's not all that easy. What makes black holes such an attractive energy source? It's their high energy conversion rate. Let's do some math. Take a 3 kg (6.6 lb) kitten and multiply his mass by the speed of light squared. You'll see that the energy contained within this one little kitty is enough to power up 6.4 million American homes for a year. But you could never extract all that energy from a cat. The best energy producers we have right now - nuclear fission and nuclear fusion - only gather 0.08 and 0.7 percent of the potential energy in mass. Black holes are a different story. Their energy conversion rate sits around the 40 percent mark. But finding a black hole wouldn't be easy. With today's available technology, even getting into the neighborhood of a black hole would take you about 12 million years. Let's fast-forward and assume that we've found a black hole nearby. How would we go about getting the most out of it? We could try throwing stuff into the black hole. The gravitational pull of a black hole would cause anything dropped into it to speed up and release energy as it went. Or we could drop things in the accretion disc of a black hole, where all the dust particles are caught in its orbit. From there we'd be collecting energy in the form of radiation - something known as the Penrose process. Some great minds have come up with a theory that a box designed to collect energy could be sent from a safe distant point via a rope to a location close a black hole's event horizon, filling with radiation in the process. One problem here is ensuring that the box and the rope don't get sucked into the hole. According to some calculations, the box suitable for this task could only be the size of bacteria so that the rope could still support it. We might as well dip "strings" right into the event horizon and drain a black hole completely dry. It would take a very long time, but... once it's done, the most ambitious energy dreams would come true. We could abandon our power plants and finally stop polluting the planet. We could fuel up our rockets and go explore outer space. We'd start building megastructures in space. The things we could do with unlimited energy... But first, we'd need to spend millions of years traveling to a suitable black hole. That is, unless we could develop a warp drive technology to speed things up. But that's a story for another WHAT IF.