This Is How Cold Space Really Is

(Hint: Pack a Parka)

A astronaut in space with Earth in their helmet reflection
Photo: Radiomoscow/Getty Images

Space travel is having a real moment. From billionaires rocketing themselves to the edge of earth's atmosphere, to companies launching futuristic balloons that will soon safely float people to new heights, it's the last frontier that adventurous travelers have been waiting for.

If you plan on being one of the newest class of traveling astronauts, we have a tip for you: Pack a coat, or a portable fan, depending on where you're headed.

Recently, broke down just how steamy and frigid things can get in space. As the website reports, the hottest areas in the universe are those directly surrounding stars. For example, Popular Science explains that our sun reaches temperatures around 27 million degrees Fahrenheit at its core but cools off to (a still wildly hot) 10,000 degrees at its surface. However, even objects close to these stars can have massive temperature swings, including Mercury, the closest planet to the sun, which says vacillates between 800 degrees Fahrenheit in the day to 95 Kelvins (-288 degrees Fahrenheit) at night.

But what about in the empty void of space? That's where things get a little more complex.

According to, radiation from a star doesn't really do much until it hits an area or object with "a lot of particles" for it to interact with. So, when the radiation from our sun hits the earth's atmosphere, it vibrates, causing heat, thus our warm (and habitable) temperatures.

But, all the area in between is a mere vast nothingness, thus can be much, much cooler than around planetary objects. However, the temperatures do not technically hit absolute zero. Instead, it's 2.7 Kelvins, or about -45 degrees Fahrenheit.

The temperature hovers in this range thanks to what is known as "The cosmic microwave background," or CMB for short, which separately explains is "leftover radiation from the Big Bang or the time when the universe began." Though you can't see the CMB, it's everywhere, around everything in the universe.

And really, this is a level of space travel the average person won't have to worry about for some time (unless Elon Musk really comes through on his promise to send people on a one-way ticket to Mars). Instead, let's look at the temperature on a more realistic scale — that of the stratosphere, which is the destination point for the upcoming World View balloon ride.

According to the National Weather Service, temperatures here range from an average -60 degrees Fahrenheit at the tropopause (the boundary between the lower level troposphere from the stratospherebase), to a max temperature of 5 degrees Fahrenheit at the top of the stratosphere, which actually makes it a bit warmer than some of the coldest destinations on the surface of the earth. So, for now, you'll be fine if you want to travel to the edge.

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