How hot is that, on the scale of everything?
Temperature has a floor and no ceiling. Everything humans experience sits in a narrow band just above the floor.
Almost exactly a room temperature
300 K is hotter than 5 of the 11 references on this page.
Reference figures are measurements and are rounded; the unit conversion behind them is exact.
| Reference | Size | Yours ÷ theirs | Note |
|---|---|---|---|
| coldest lab temperature | 1×10⁻¹⁰ K | 3,000,000,000,000× | |
| cosmic microwave background | 2.73 K | 110× | |
| liquid nitrogen | 77 K | 3.9× | |
| a domestic freezer | 255 K | 1.18× | |
| room temperature | 293 K | 1.02× | |
| a candle flame | 1,300 K | 0.231× | |
| molten steel | 1,800 K | 0.167× | |
| the Sun’s surface | 5,772 K | 1/19.2 | |
| lightning | 30,000 K | 1/100 | |
| the Sun’s core | 15,700,000 K | 1/52,333 | |
| a fusion reactor | 150,000,000 K | 1/500,000 |
Worth knowing
- Fusion reactors run at 150 million kelvin — ten times the centre of the Sun — because they cannot match its crushing pressure.
- Laboratory cooling has reached under a billionth of a kelvin. Absolute zero itself is unreachable, not merely difficult.
Frequently asked
What is absolute zero?
0 K, or −273.15 °C: the point where a system has the least possible thermal energy. The third law of thermodynamics forbids reaching it in a finite number of steps.
Is there a maximum temperature?
Not in ordinary physics. The Planck temperature, about 1.4 × 10³² K, is where current theory stops describing anything, not where temperature stops.