I'm having a argument with a colleague, I don't know how to explain to him that if you spin a handspinner in space it will spin indefinitly (if you don't hold it). I agree that if you hold it, it will slow down because of the friction with the center part. Would it theoreticaly spin forever?
Assuming a perfect vacuum, you're both partially right. The spinner would slow down due to friction with the bearing. However, this also speeds up the bearing so at some point, the entire spinner is spinning at the same rate, at which rate it would spin forever.
Furthermore, even if you do hold it, the entire spinner will eventually stop spinning with respect to your hand, but will transfer angular momentum to you, so that you and the spinner are both spinning in space. If you then let go of the spinner it would continue spinning at the new lower rate, again indefinitely.