# 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 riders 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. See How Special Relativity Works for details.

In a practical sense, this idea has problems because of the centrifugal forces 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 is very nearly zero friction on them. These flywheels are able to achieve speeds up to about 200,000 rotations per minute (rpm). 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 a flywheel with a 3-foot (1-meter) circumference and about a 12-inch (32-cm) diameter were running at 1 million rpm, the outer edge of the flywheel would be traveling at only about 34,000 miles per hour (55,000 kph) -- nowhere even close to the speed of light at 186,000 miles per second.