What would happen if you kept a piece of copper near absolute zero in your room?

Imagine this: one winter morning you walk into the kitchen. On the table lies a piece of copper. It looks like any other piece of copper. But its temperature is only a few degrees above absolute zero - about minus 269 degrees Celsius. Now you leave it at normal room temperature. What would happen then?

You might think ice would start forming around the piece of copper in an instant, the window glass would be covered in white mist, and soon the whole room would freeze over, just like in a film. But in reality that would never happen. Exactly the opposite would occur.

The piece of copper would start absorbing heat from its surroundings until its temperature came close to the temperature of the room.

You have surely rubbed your two hands together on a winter morning. Rub them for a while and your hands grow warm. But no fire or hot water was put into your hands from outside. So how did your hands get warm?

In fact, when two hands are rubbed together, friction converts mechanical energy into heat. As a result, the energy of the random motion of the molecules and atoms inside the hands increases. That is why our hands become warm.

The temperature of any substance is related to the thermal motion of the particles inside it. In general, the higher the temperature, the greater the energy of the particles' random motion. For example, the molecules of hot coffee move thermally faster than the molecules of cold coffee.

Now back to the question. Think: if the temperature of an object keeps falling until it reaches the very lowest limit, what happens? The lowest limit of temperature is called absolute zero. Its value is 0 Kelvin, or minus 273.15 degrees Celsius.

Now back to the piece of copper on the kitchen table. Suppose a piece of copper cooled with liquid helium has a temperature of about 4 Kelvin. It is brought to normal room temperature and placed on the table. First, heat will enter the copper through the part touching the table. At the same time, it will also gain heat from the surrounding air.

If the air in the room is 25 degrees Celsius, there will be a huge temperature difference between the piece of copper and the room. Because of this difference, the rate of heat flow may be high at first. As the copper's temperature rises, that difference will shrink.

But keeping the piece of copper in the room will not freeze the whole room. Rather, the air around the copper may cool slightly. That too will depend on the size and mass of the piece of copper, the size of the room, and how quickly heat arrives from around it.

Another thing may happen. When the water vapour in the air touches the extremely cold surface of the copper, it may condense into water or ice. If the temperature is low enough, ice may form on the surface. So even if a white coating appears on the piece, it is not proof of some freezing ray; it may simply be the result of water vapour in the air condensing.

Such low temperatures are not created merely to satisfy curiosity. They have important uses in many areas of modern science and technology. Quantum computers are a good example. Some quantum computers use superconducting circuits, which must be kept at very low temperatures so that thermal disturbance is reduced and the qubits can hold a particular quantum state.

Special refrigeration machines are used for this, which can bring the temperature down to a few millikelvin. That temperature is far lower than the average background temperature of space, about 2.7 Kelvin.