What is the lowest possible temperature at which nothing can be colder and no heat energy remains?

The lowest possible temperature at which nothing can be colder and no heat energy remains is known as absolute zero. This is the point at which the fundamental particles of nature have minimal vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion.

Here are the steps to understand this concept:

1. Temperature is a measure of the average kinetic energy of the particles in a system. Kinetic energy is the energy of motion, so the faster the particles are moving, the higher the temperature.

2. As a system loses heat, the average kinetic energy of its particles decreases. This means the particles are moving