superluminal propeller tip

[mopc]

If you build a propeller-like spinning device with very long blades, and you spin it so fast that the ends of the blades would reach light speed, what prevents the tips from reaching light speed? Of course supposing the hardest conceivable materials and an engine that generates as much power as the Sun to spin such a behemoth.

[eburacum45]

The ends would eventually become so massive, due to relativistic effects, that they would break off- no material is infinitely strong, so no spinning propeller can ever approach light speed.
This article might help explain why the mass of the tips will increase;
http://en.wikipedia.org/wiki/Relativistic_mass

[mopc]

The ends would eventually become so massive, due to relativistic effects, that they would break off- no material is infinitely strong, so no spinning prpeller can ever approach light speed.
This article might help explain why the mass of the tips will increase;
http://en.wikipedia.org/wiki/Relativistic_mass

Yeah, that's pretty much what I imagine, or that the engine would never have the power to propel the 'near-infinite'( [-X ) mass! Looks like I;m not debunking Einstein this year yet.

[papageno]

Don't forget that in Relativity there is no such thing as rigid body as intended in Classical Mechanics (in theory, a rigid body is defined as a system of massive particles, with relative distances constant and the same in all frames of reference; in Relativity these distances are no longer the same in all reference frames).
Also, the bonding of atoms and molecules in a material occurs via electromagnetic interaction.
If you spun the propeller at relativistic speeds, assuming the propeller does not break, it would be significantly deformed because the electromagnetic field would have a significant delay in propagating from the center to the rim.