字幕表 動画を再生する 英語字幕をプリント A machine that can sustain motion forever with no energy input is the greatest dream in engineering. And while many have tried to invent a perpetual motion device, all have failed. Will we ever create such a machine and harness free energy forever? Short answer? Nope. Sorry to be a stick in the mud, but a machine that can keep its parts moving forever violates some pretty fundamental laws that govern how we think our universe works, and videos on the youtubes where people claim to have invented perpetual motion machines are as fake as my girlfriend's laughs at my jokes. First let's lay out just what we mean when we say a machine that can keep going forever. If you created a perpetual motion machine and set it running it would just keep going, longer than any of us would live, longer than our sun would live, as long as the entire universe itself would live. And getting more energy from an outside source is cheating, it should keep running in total isolation. You're not allowed to power it with light or ambient heat or by leaving money in your will for your grandchildren if they give it a push every now and then. That's a pretty daunting challenge, but it hasn't stopped people from trying. Over the years they've come up with ideas that seem plausible in a sketch on a patent application, but less workable in reality. A classic example that comes in many variations is the overbalanced wheel. No matter if they use fluids or rolling balls or weights on articulated arms, the concept is always the same: as the wheel spins, masses on one side move to a wider radius, providing more torque and unbalancing the wheel to keep it spinning forever. Except the wheel isn't unbalanced. There are more weights on one side of the wheel, balancing out the side with fewer weights but more torque. All that really accomplishes is the center of gravity gets shifted below the axle, making the wheel behave more like a pendulum, swinging back and forth before stopping. A simple wheel might work better, and while a well made wheel will spin for a long time, it will eventually succumb to the great nemesis of all machines: friction. If friction could be totally eliminated it would be possible to make a machine that runs forever. Just give it that initial bit of energy and so long as it doesn't lose any, it'll just keep going. But no surface is smooth enough to be frictionless. Well maybe with the exception of superfluids, but even those are usually supercooled which means you'd need to use energy to maintain those low temperatures. Mechanical parts will rub, which will turn some of the mechanical energy into heat and cause the machine to slow down. But while a machine that, once started, can run forever is theoretically possible at best, machines that power themselves and generate free energy from nothing are flat-out breaking the law. Which law? The first law of thermodynamics, which is you do not talk about thermo- wait no I'm thinking of something else. It's the idea that in a closed system, energy cannot be created or destroyed, only converted into other forms of energy. This is one of those laws on which we've built our entire understanding of the universe, anything that would upend it would rewrite multiple scientific disciplines. A machine that can keep itself running forever and could power your toaster to boot would be more than 100% efficient. In other words, it would get something from nothing, and from everything we've ever seen ever, that's just not possible. So, sorry but every time a video surfaces of some zany wheel that can supposedly spin forever, you can rest assured that it's fake. At this point the never-ending stream of phony claims about them is the only thing that's perpetual. So getting your own perpetual motion machine might be a far away fantasy, but getting a brand new cell provider isn't. Visible is the new way to think about phone service. No stores. No annual contracts. No hidden fees. Just 40 bucks a month for unlimited messages, minutes, and data at speeds up to 5 megabits per second. All on Verizon's 4G LTE Network. When you think the future of phone service, think Visible. Visible is the new way to think about phone service. $40/mo phone service that's actually $40/mo. Unlimited everything (including data at speeds up to 5 Mbps). All on Verizon's 4G LTE Network. No hidden fees. Ever. When you think the future of phone service, think Visible. Don't forget to subscribe so you never miss an episode, and check out this video for more on the science of engineering. One last thing- Despite their impossibility people still keep dreaming up perpetual motion machines, to the point that the U.S. patent office flat out refuses to review new patents for them. Thanks for watching, I'll see you next time.