Absolute Zero and the Temperature of Space

You are outside in freezing weather when it is snowing or you are a mountain climber climbing the Himalayas, you are very cold but have you ever thought about how much colder you can get?

It is accepted that everything in the universe has a limit, heat has a limit, and so does light. For example, the speed of light in a vacuum is approximately 300 thousand kilometers per second. So is there a limit to cold?

Absolute cold, that is, a temperature that cannot be lowered, does exist, of course, absolute zero is the lowest possible temperature point in thermodynamics and is defined as -273.15°C or 0 Kelvin (K). At this temperature, the atoms and molecules of a substance drop to the lowest possible energy level, meaning their motion is reduced to a minimum. Theoretically, all thermal motion stops at absolute zero. In other words, it is not possible to drop to this temperature or below, only to come very close.

The lowest temperature ever reached is 100 picocelvins, or just 1 ten-billionth of a degree, 0.0000000001 degrees above absolute zero.

Now let's talk about "Space". First of all, not everywhere in space is the same temperature, of course since the atoms are very sparse there is almost no heat transfer, but when you are standing somewhere close to the Sun (150 million km is considered close) it is possible to see -100 degrees in the shade and +100 degrees in the sun, that is, the moment you go outside the Earth you can be exposed to this 200 degree temperature difference, so you need to be well protected and careful.

So how many degrees is space? Since atoms are very sparse here, it should be absolute zero, right? The temperature in space is usually measured as 2.7 Kelvin (approximately -270.45°C). This temperature is considered to be a result of the radiation left over from the Big Bang, called the "cosmic microwave background radiation" (CMB), and one of the evidences of the Big Bang.

In space, the density of matter is extremely low, so heat has a very hard time spreading. However, since it is not heat in the true sense, although it is very close to absolute zero, this temperature is not absolute zero due to the presence of photons that carry energy.