Space temperature varies due to its composition. The temperature in deep space is 2.725 Kelvin, while closer to Earth it is around 35-40 Kelvin. Measuring space temperature is complicated, as particles have low density, and heat transfer is minimal. Planck’s law is used to determine temperature by analyzing radiation emitted from space. The Milky Way galaxy is slightly hotter than other areas. Other factors that could affect space temperature include dark matter and dark energy.
When calculating temperature in space, it’s important to understand that most estimates need to account for the varying composition of space. Outer space is generally considered to be the portion of the universe that is almost completely empty and, from Earth’s perspective, officially begins at an altitude of about 62 miles (100 kilometers) above sea level. In the vacuum between planets, star systems and galaxies, the temperature in space is generally considered to be 2.725 Kelvin, or -454.72°F (-270.4°C). That’s just a small amount above absolute zero, the lowest temperature at which the motion of matter is thought to cease, at -459.67°F (-273.15°C).
Medium temperature
When scientists speak of 2,725 Kelvin as the temperature in space, they are speaking of an average temperature, actually what is called the cosmic microwave background, which is the remaining energy from the Big Bang. Closer to Earth, such as just outside Pluto’s orbit, the temperature is estimated to be closer to 35 or 40 Kelvin due to the effects of the distant Sun. This is still very cold, but nowhere near as cold as somewhere in deep space away from sunlight.
Temperature measurement
Measuring temperature in space is more complicated than simply using a thermometer, since temperature is only a meaningful figure when heat can be efficiently transferred from one body to another. In space, while the temperature of particles can be very high, their density is very low, so their ability to transfer heat is minimal. They may be millions of degrees into the Kelvin range, but because they so rarely collide with each other, the real phenomenon of temperature or heat transfer doesn’t occur. Temperature in space therefore has to do with the movement and concentration of molecules, which in turn determines how often they collide with each other to gain or lose energy.
For this reason, temperature must be determined using Planck’s law, which says that every object in the universe emits radiation based on its temperature. By looking at the radiation emitted from space and using this formula, scientists found that the temperature is approximately 2,725 K. Different parts of space actually have different temperatures, and the Milky Way galaxy, where Earth is located, is slightly hotter than many other areas.
Influencing factors
It is important to remember that space is actually everywhere and that even human bodies are mostly composed of empty space. So when someone discusses temperatures in a particular region of space, he must also include all objects that appear solid to the naked eye. Other factors that could eventually change experts’ views on what temperature is in space include the effects of dark matter and dark energy, which together make up 96% of all the known universe.
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