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# Lower and Upper Temperature Limits

by Ron Kurtus

There are lower and upper temperature limits for an object or material.

The temperature of a material is defined as the average kinetic energy of its atoms or molecules, plus any other energy that can be transferred. In theory, the lower limit of temperature would be when all particles have zero energy. Heating the material gives the particles kinetic energy. The upper temperature limit should be when all of the object's particles were traveling at the speed of light.

Questions you may have include:

• What is the lower temperature limit?
• What happens when a material is heated?
• What is the upper temperature limit?

This lesson will answer those questions. Useful tool: Units Conversion

## Absolute zero limit

The lowest or coldest temperature possible is called Absolute Zero. This absolute zero limit is the temperature of an object when all of its matter has zero energy.

This limit cannot be reached because of the rules of quantum mechanics that require some motion must be present for matter to exist. Usually, absolute zero is defined as the lowest possible temperature allowed by the laws of quantum mechanics.

It is impossible for an object to be at absolute zero because of the effects of gravitation forces, which are everywhere. Gravity and electromagnetic waves provide energy that will increase the temperature of a hypothetical object at absolute zero, if only a slight amount.

Scientists have been able to cool things to a fraction of a degree above absolute zero. At such a cold temperature, matter starts to behave strangely.

## Heating an object

When an object is heated, its atoms and molecules increase in speed and thus increase in their kinetic energy or moving energy. There is a direct relationship between the kinetic energy of the material and its temperature. As the energy goes up, so does the temperature and vice versa.

Not only does the kinetic energy of the particles increase when heated, but also the material may give off electromagnetic radiation. This energy is then transferred to a thermometer through conduction, convection and/or radiation.

The thermometer indicates the temperature or average energy. A little energy, though, is lost in the heat transfer.

## Speed of light limit

The greatest temperature possible is limited by how fast its atoms can travel.

The upper limit that anything can travel is at the speed of light. We don't know why this is the limit; it is simply a property of space. Electromagnetic waves and gravity waves get very close to the speed of light, but they can never reach it. Calling this upper limit the "speed of light" is a misnomer, because light itself cannot really reach that speed.

According to the Theory of Relativity, mass increases dramatically and time slows down as matter approaches the speed of light. Thus, the limiting temperature is often called infinite temperature.

## Summary

Temperature is the average kinetic energy of a material's atoms or molecules, plus any other energy that can be transferred. The lower limit of temperature is absolute zero. Heating material gives the particles kinetic energy. The upper temperature limit is when all of the object's particles are traveling at the speed of light.

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