: If you spin a coin in space, would it keep spinning forever and ever until it hit something?
Answer : The coin would slow down as it hits something or as it is acted upon by gravity. If the coin is in a spacecraft with air, it would slow down in a short time - on the order of minutes since there are lots of air to run into. If it is spun in the vacuum of space, it would spin much longer. There are some particles even in deep space that eventually would hit the coin and slow it down, but it would be a very long time - probably years. The other thing that could slow it down is gravity. The coin would be in some gravitational field - Earth's or other planet or the Sun's or a combination of several bodies. This would cause the coin to eventually slow down and have its edge (most mass) pointed at the planet or sun. This would take many years.