Why can't there be a number lower than absolute zero

Absolute zero is not about numbers. It's about temperature, and the

motion of molecules in gases.

You know that the temperature we feel with our skin is the result of the

average speed of all the tiny molecules zipping around or vibrating in

the solid, liquid, or gas.

The faster they're all moving, the warmer the substance feels to us.

The slower they're all moving, the cooler the substance feels to us.

When molecules slow down to zero and lose all of their kinetic energy,

that temperature is what we call 'absolute zero' ... if they're not moving

at all, then they can't move any slower.