The coldest temperature possible is called absolute zero , and it is defined as 0 kelvin, which is −273.15 °C or −459.67 °F. At this point, you cannot extract any more heat energy from a system.

What is the coldest temperature possible?

Physicists define temperature in terms of how much average kinetic energy (motion) the particles in a substance have. The less they move, the colder it is. Absolute zero is the theoretical limit where you cannot remove any more thermal energy from a system, so by definition nothing can be colder than 0 K.

Because of the laws of thermodynamics, you can get arbitrarily close to absolute zero but never reach it exactly; doing so would require infinite work (energy and perfect control), which is physically impossible.

How cold is that, in everyday terms?

  • Absolute zero in kelvin: 0 K.
  • In Celsius: −273.15 °C.
  • In Fahrenheit: −459.67 °F.

For comparison: the coldest natural air temperature ever directly recorded on Earth is about −89.2 °C (−128.6 °F) at Vostok Station in Antarctica, which is still nearly 184 K above absolute zero.

How close have we actually gotten?

In laboratories, scientists can cool special quantum systems to unimaginably small fractions of a degree above absolute zero.

  • Experiments with ultracold gases (Bose–Einstein condensates) have reached temperatures around tens of picokelvin , i.e., trillionths of a kelvin above 0 K.
  • In one record-setting experiment, a gas was held at about 38 picokelvin (0.000000000038 K above absolute zero) for a short time.

These are far colder than any natural place in the universe that we know of, and they are created only under extreme, carefully controlled lab conditions.

The universe’s “background cold”

Even the “empty” universe is not at absolute zero:

  • The cosmic microwave background radiation has a temperature of about 2.7 K, which is the average temperature of deep space today.
  • As the universe expands over trillions of years, this background temperature will keep dropping and will get closer and closer to 0 K, but never quite reach it.

This distant future, when usable heat is effectively gone and everything is near the lowest possible temperature, is part of what cosmologists call the heat death of the universe.

Why there is a bottom but (almost) no top

Your question also brushes against an interesting contrast people discuss in forums: there is a strict lower bound (absolute zero), but no similarly strict, practical upper bound on temperature.

  • At the low end, kinetic energy cannot go below “no extractable thermal energy,” which is what defines 0 K.
  • At the high end, there are theoretical limits like the Planck temperature (often quoted around 103210^{32}1032 K) where our known physics breaks down, but that’s not a hard “thermodynamic” stop the way absolute zero is; it’s more of a “beyond this, our theories don’t make sense.”

So: cold has a sharp physical floor; heat has a more speculative ceiling.

Mini FAQ

Can anything be colder than absolute zero?
On the normal thermodynamic scale, no: you cannot go below 0 K in the usual sense of temperature. A few advanced physics experiments talk about “negative temperature,” but that uses a special definition for systems with an upper energy limit and does not mean “colder than absolute zero” in the everyday sense.

Why can’t we actually reach 0 K?
Because each cooling step requires work to remove heat, and as you approach absolute zero, the amount of work needed grows without bound. The second and third laws of thermodynamics tell us that reaching 0 K in a finite number of steps is impossible.

Simple numeric snapshot (HTML table)

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Quantity Temperature Notes
Absolute zero 0 K = −273.15 °C = −459.67 °F Theoretical coldest possible temperature
Coldest lab record ≈ 38 picokelvin above 0 K Ultracold gas in a lab experiment
Coldest air on Earth −89.2 °C (Vostok Station) World Meteorological Organization record
Deep space today ≈ 2.7 K Cosmic microwave background temperature
**TL;DR:** The coldest temperature possible is **absolute zero** , 0 K (−273.15 °C, −459.67 °F), where no further heat can be extracted; we can get unimaginably close in the lab, but the laws of physics say we can never quite reach it.

Information gathered from public forums or data available on the internet and portrayed here.