Question

why havent scientists ever been able to get a substance to reach absolute zero? because its too expensive because the particles in all known substances can never completely stop moving

Explanation:

According to the third - law of thermodynamics, as the temperature approaches absolute zero (\(0\space K\) or \(- 273.15^{\circ}C\)), the entropy of a perfect crystal approaches a constant minimum. In reality, all substances are made of particles (atoms, molecules, etc.). These particles have kinetic energy due to their motion. Even at extremely low temperatures, there is always some residual motion of the particles. For example, in a gas, as the temperature is lowered, the average kinetic energy of the gas molecules decreases. But it can never reach zero because that would require the complete cessation of all molecular motion, which is not possible according to the laws of thermodynamics.

Answer:

because the particles in ALL known substances can never completely stop moving