Written by Matthew Dunn
Illustrated by Alex Hallatt
From absolute zero to the surface of the Sun, there’s a whole range of temperatures in our Universe. Let’s learn more!
Absolute zero is, unsurprisingly, the lowest temperature possible. When things get colder, their particles slow down. At −273.15 °C, they are motionless and entropy is zero. We can’t cool things down to absolute zero, but Finnish scientists have got very close − even as close as 0.000 000 001 °C above it.
While we’re most familiar with nitrogen as a gas in the air around us, when it’s cooled down below −196 °C, it turns into a liquid. Liquid nitrogen isn’t just super cool – it’s also super useful for science. It can be used to store biological samples, freeze off moles that might be cancerous, and cool down superconductors!
The coldest temperature ever recorded on Earth was on the 10 August 2010, in – you guessed it – Antarctica! The recording was made using satellites that detect heat radiating from the surface of the planet.
According to the International Ice Cream Association – who you’d hope would know a thing or two about ice cream – somewhere between −12 and −14 °C is the perfect temperature for this icy treat. But, when you’re not busy licking it, make sure it’s in a freezer set between −18 and −20 °C.
While pressure is also an important factor for changes of state, 0 °C is when ice forms at standard atmospheric pressure. This is no coincidence, because the Celsius scale was originally created by dividing the difference between water’s boiling point (100 °C) and the melting point of ice into one hundred degrees.
Although there is some variation even among healthy people, most of us have an internal temperature close to 37 °C. A change of even one or two degrees to this internal temperature means trouble for our health, with fevers being a common example. And, if body temperature’s not a gruesome enough name for your liking, don’t worry – it used to be called blood heat.
Hottest recorded day on Earth
Death Valley in California lays claim to the title of the hottest place on Earth after the temperature hit 56.7 °C in July 1913. The hottest recorded temperature in Australia is a full six degrees cooler than that, with 50.7 °C recorded at Oodnadatta in South Australia in 1960.
Okay, so not all lava is exactly 1000 °C. The temperature of lava depends largely on what type of rock it’s made out of. While molten rhyolite can be as cool as 650 °C, basalt-based lava can be more than 500 °C higher than that. But, no matter what it’s made of, it’s not something you’d want to get too close to!
Lightning strikes release a huge amount of energy, heating the surrounding air so fast that the air expands faster than the speed of sound. The resulting shockwave is what we hear as thunder.
2 000 000 °C
The Sun’s corona
The temperature of the Sun varies a lot, depending on where it’s measured. At its core, fusion reactions heat it to a whopping 15 000 000 °C, whereas the surface is a mere 5500 °C. Scientists still don’t completely understand why the plasma – or corona – that surrounds the Sun is so much hotter than the surface.
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