What is absolute zero?

Absolute zero refers to the theoretical lowest temperature achievable, at which the motion of particles theoretically comes to a complete halt, indicating that the system has reached its minimum possible energy state. At this temperature, which is defined as 0 Kelvin, the system exhibits no thermal energy, and hence, no kinetic energy of particles.

This concept is significant in the study of thermodynamics and quantum mechanics, as it implies a foundational limit to how low a temperature can go. In practice, absolute zero cannot be reached, but scientists have been able to get very close to it. The definition aligns closely with thermodynamic principles and illustrates fundamental limits in physics.

In contrast, reaching room temperature is far from absolute zero, extreme pressure does not define a zero thermodynamic temperature but rather affects states of matter, and while the Kelvin scale's endpoint indicates absolute zero, the primary characteristic defining it is the minimum energy state of a system. Thus, the clarity that absolute zero is lowest possible temperature with minimal energy is essential to understanding the fundamental characteristics of thermodynamics.