Absolute zero — 0 Kelvin or −459.67 °F — is the theoretical lowest temperature in the universe. At this point classical thermal motion stops completely… but quantum physics and the laws of thermodynamics say we can never actually get there.
Key Takeaways
- Absolute zero = 0 K = −273.15 °C = −459.67 °F
- All classical motion stops, but quantum zero-point energy remains
- Third Law of Thermodynamics: impossible to reach in finite steps
- Coldest temperature ever achieved: 38 picokelvin (2021)
- Powers superconductivity, superfluidity, quantum computing & MRI machines
Table of Contents
What Is Absolute Zero?
Absolute zero is the theoretical lowest temperature: 0 Kelvin (0 K), exactly −273.15 °C or −459.67 °F. It’s where, in classical physics, particles would have zero kinetic energy and all thermal motion stops. It’s also the point where a perfect crystal has zero entropy.
Absolute zero shown on temperature scales
Quantum mechanics says even at 0 K, atoms still have tiny zero-point motion due to the uncertainty principle — so true perfect stillness is impossible.
Absolute Zero in Celsius & Fahrenheit
- 0 K = −273.15 °C
- 0 K = −459.67 °F
Brief History & Major Milestones
- 1848 – Lord Kelvin creates the absolute temperature scale
- 1898 – Hydrogen liquefied (−252.87 °C)
- 1908 – Helium liquefied (4.2 K)
- 1911 – Superconductivity discovered
- 1995 – First Bose–Einstein condensate
Why Absolute Zero Is Impossible to Reach
The Third Law of Thermodynamics says:
“It is impossible to reduce any system to absolute zero in a finite number of operations.”
As you cool something, each step removes less and less heat. Near 0 K you would need infinite steps — physically impossible.
How Close Have Scientists Gotten?
- 2021 – 38 picokelvin (38 × 10⁻¹² K) – current world record (University of Bremen)
That’s only 0.000000000038 K above absolute zero!
Weird Quantum Effects Near Absolute Zero
- Superconductivity – zero temperature resistance
- Superfluidity – liquids with zero viscosity
- Bose–Einstein Condensate – atoms act as one giant quantum wave
Real-World Applications & Why Students Study It
- MRI machines (superconducting magnets)
- Quantum computers (Google, IBM)
- James Webb Space Telescope (cooled to ~7 K)
- Atomic clocks for GPS & internet timing
- Physical chemistry & thermodynamics courses
- Astrophysics (cosmic microwave background ~2.7 K)
Common Student Questions
What is absolute zero in Fahrenheit?
Exactly −459.67 °F.
Has absolute zero ever been reached?
No — and the Third Law proves it never can be.
What is the coldest temperature ever achieved?
38 picokelvin (38 pK) in 2021.
What happens to matter at absolute zero?
Classical motion stops completely, but quantum zero-point motion remains.
Are negative temperatures possible?
Yes — in special quantum systems, negative Kelvin temperatures are actually hotter than infinity!
