Welcome to brain Stuff from how Stuff Works dot com where smart happens. Join Josh and Chuck, the guys who bring you stuff and should know, as they take a trip around the world to help you get smarter in a topsy turv economy. Check out the all new super Stuff Guide to the Economy from house stuff Works dot com, available now exclusively on iTunes. Hi Am Marshall Brain was today's question. If you could spin a carousel fast enough to get its rim moving at nearly the speed of light,
would time stand still for people on the carousel. At least in the theoretical sense, this idea is reasonable. If the carousel were spinning so that the outer edge of the carousel moved at nearly the speed of light, then time would appear to slow down for people on the carousel. When the carousel writers looked out at the world spinning by, the days would pass very quickly, so the people on the carousel would age very slowly relative to people not
on the carousel. This would create essentially a time machine that lets the passengers on the carousel travel into the future. In a practical sense, this idea has problems because of the centripetal force that the carousel would generate. Some of the fastest rotating objects in existence today are high speed flywheels. High speed flywheels float on magnetic bearings in a vacuum chamber,
so there's very nearly zero friction on them. These flywheels are able to achieve speeds up to about two hundred thousand rotations per minute. The main problem with flywheels running this quickly comes in the form of rotor disintegration. The
outward forces on the rotor are huge. Even if you assume that the flywheel has a twelve inch diameter running at a million rpm, the outer edge of the flywheel would be traveling at only about thirty four thousand miles per hour, nowhere even close to the speed of light at a hundred eighty six thousand mile per second. The other option would be to create an extremely large carousel. Say you built a ring as big as Earth's orbit, or about a hundred eighties six million miles in diameter.
This ring would only have to spend at a rate of about one revolution per hour compared to the Earth's one revolution per year to achieve something near the speed of light. Building this ring and then accelerating the entire thing, of course, would be a big project. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at how stuff works dot com. For more on this and thousands of other topics, go to how stuff works dot com.