Nothing in the universe — or in a lab — has ever reached absolute zero as far as we know. Even space has a background temperature of 2.7 kelvins. But we do now have a precise number for it: -459.67 Fahrenheit, or -273.15 degrees Celsius, both of which equal 0 kelvin.

William Thomson

To Kelvin’s mind, absolute zero was where a temperature scale should begin, but for convenience, he used the markers and intervals of the widely-known Celsius scale as a base for his own.

Summary: On the absolute temperature scale, which is used by physicists and is also called the Kelvin scale, it is not possible to go below zero – at least not in the sense of getting colder than zero kelvin. At zero kelvin (minus 273 degrees Celsius) the particles stop moving and all disorder disappears.

Universe’s oldest known quasar discovered 13 billion light-years away. Astronomers have found the farthest known source of radio emissions in the universe: a galaxy-swallowing supermassive black hole.

16 Psyche

Why black holes are the scariest things in the universe. For one, falling into a black hole is easily the worst way to die. Halloween is a time to be haunted by ghosts, goblins and ghouls, but nothing in the universe is scarier than a black hole.

The comet has been described as “the single most dangerous object known to humanity”. In 1996, the long-term possibility of Comet Swift–Tuttle impacting Earth was compared to 433 Eros and about 3000 other kilometer-sized objects of concern.

The cold will eventually kill you for sure, but the fact that an atmosphere can’t really exist near absolute zero should be your primary concern. So the answer would be however long you can go without oxygen.

At 70 degrees F (21 C), you experience “profound,” deadly hypothermia. The coldest recorded body temperature a person has ever survived is 56.7 degrees F (13.2 degrees C), according to Atlas Obscura.

If the humidity is low, humans can endure even hotter temperatures. In a burning building or a deep mine, adults have survived 10 minutes at 300 degrees. Children, however, cannot withstand such temperatures, and 120-degree cars can be deadly in just minutes.

Changes in speed are expressed in multiples of gravitational acceleration, or ‘G’. Most of us can withstand up to 4-6G. Fighter pilots can manage up to about 9G for a second or two. But sustained G-forces of even 6G would be fatal.

“Our bodies are surprisingly resilient in many situations, but rapid acceleration is not one of them. While the human body can withstand any constant speed—be it 20 miles per hour .”

9 g

An upwards acceleration of about 5g is enough to overwhelm the ability of your heart to pump blood to your brain. The blood pools in your head, your face swells up and your lower eyelids are forced over your eyes. This is called ‘redout’ because all you see is the light shining through your eyelids.

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