Weather Explained: What's the temperature in space and why?

If you’ve ever been sitting outside in the hot summer sun, basically melting into a human popsicle puddle, you may have questioned how space may be cold! There is a good chunk of space that is a lot closer to the sun than you, and yet outer space temperature is said to be cold, near absolute zero even. How is this possible? What makes Earth so different from seemingly the rest of the universe? Why is the temperature in space cold? How cold is outer space for real?

We are going to answer all of these questions, and more, but first, we need to lay out the framework so you can best understand the science behind outer space.

• First, we have to establish what heat is in the scientific community. For us, heat is whether you need to put on a sweater or jump in the pool, but in the science world, it is a little more complicated. Heat is how fast particles are moving. The faster they are moving, the hotter the temperature and the reverse is true for the colder temperatures.

• Second, scientists do not use Fahrenheit or Celsius for their space temperature readings. Why would they add another temperature scale into the mix? The truth of the matter is they needed a scale that was based on the idea of absolute zero. The scale is known as Kelvin after the scientist William Thomson, or more dramatically, Lord Kelvin.

• Third, absolute zero is where particles are not moving, so there is no heat transfer. To put this into perspective, 0 Kelvin is equivalent to -273 degrees Celsius and -495 degrees Fahrenheit. It’s pretty chilly.

Now that we have our “what is the temperature in space?” groundwork laid, let’s get into the meat of it all.

What is up with Earth?

Earth is unique, to say the least. Earth seems to be the exception to every outer space rule from sustaining life to having water. Why is it? A lot of it has to do with our amazing atmosphere that does so much for us. It protects us from meteors and other threats from space, helps with the flow of the water cycle, and keeps oxygen and carbon dioxide trapped so living things can, well, live. Another key part of our atmosphere is that it traps the sun’s energy while absorbing the harmful solar rays. We get all the benefits of having the sun  for nearly no cost thanks to our atmosphere. The Earth is about 93 million miles away, and we see temperatures between 185 Kelvin (-126 degrees Fahrenheit or -88 degrees Celsius) to 331 Kelvin (136 degrees Fahrenheit or 58 degrees Celsius). How is it then that the space temperature between Earth and the Sun, space that is closer to the sun, is frigid?

Why is space cold?

Remember in the groundwork section where we said that the hot temperature is from the movement of particles? On earth, there are zillions of gas particles, and they are constantly moving, but not exceptionally fast, according to Popular Mechanics. The sheer number is what heats our planet, and the slight changes in speed dictate what season it is or what the weather might be. You are constantly being bumped up against millions of particles and are warmed by that interaction. In outer space, there are very few gas particles, and while they move really fast as they are energized by stars like the sun, they have to travel great distances to hit anything. If you were up in space without a spacesuit, first of all, you’d be dead, but second, you’d be extremely cold because there are no particles bumping into you. There is little to no heat transfer. This is also why there is no sound in outer space. There are not enough molecules to vibrate and carry the sound. This fact is what makes scenes in Star Wars movies where everything goes silent as ships crash into one another so cool.

However, there are areas in space where the temperature  is extremely hot, reaching into the millions, and they tend to be close to the giant gas balls in space like our sun or in direct line of sight. Spacesuits have both heaters and coolers inside for this very reason. If an astronaut is in the direct line of sight from the sun at the same distance away from the sun as the Earth is, her cooling system will kick in because those temperatures can be close to 393 K (aka really hot), according to Quartz.

How cold is space?

The real answer is that it depends. For intents and purposes, the temperature in space is cold. Very cold. The coolest, or freakiest part, about space, is that there are areas where there are no gas particles, no movement at all, and that is where you’ll find the temperature to be at 0 K or absolute zero. It is unlikely you will randomly stumble upon an area in outer space where there is no background cosmic activity, where nothing is moving.You’ll be in the limbo state of absolute zero, but it is possible. If you’re sent hurtling into the sun, the closer you get, the hotter the temperature will become. The most interesting part is that even if you are floating directly to the sun, you’ll freeze before you burn, even as you get closer. According to Quartz, on Earth, warmth is transferred primarily through conduction, in space, it is through radiation. You will lose your heat slowly, and then all at once and drift through outer space as a human ice cube.

The bottom line: the temperature outer space is brutally cold. The gas particles may be moving really fast, having been energized by the sun, but the outer space is huge and gas particles and stars are lightyears away from one another. There will be no knocking into each other. There is simply too much space.

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