Temperature

The third law of thermodynamics states that it's impossible to cool a system to absolute zero (0 Kelvin or -273.15 °C). As an object gets colder, it requires exponentially more energy to remove smaller amounts of heat, making the final step of reaching true zero an infinite challenge.

While space itself is extremely cold, scientists have achieved temperatures even lower than the cosmic background radiation in labs. Researchers at the University of Colorado Boulder cooled rubidium atoms to just 38 billionths of a degree above absolute zero, creating a Bose-Einstein condensate to study quantum phenomena.

Scientists estimate the temperature of Earth's solid iron-nickel inner core to be around 5,200 degrees Celsius (9,392 degrees Fahrenheit). This extreme heat is a remnant from the planet's formation and ongoing radioactive decay.

This phenomenon, known as the Mpemba effect, is still not fully understood but has been observed for centuries. Hypotheses include supercooling, evaporation, convection currents, and dissolved gases affecting the freezing process.

While the surface of the sun is around 9,940 degrees Fahrenheit (5,500 degrees Celsius), lightning can reach temperatures of 50,000 degrees Fahrenheit (27,760 degrees Celsius). This intense heat causes the air to expand explosively, creating thunder.