Absolute zero is the lowest theoretically attainable temperature, corresponding to 0 Kelvin (K) or -273.15 degrees Celsius. At this limiting temperature, particles in a system possess their minimum energy, the quantum zero-point energy, and all thermal motion ceases.
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How to measure it in class
Although it is impossible to reach absolute zero in the classroom, FizziQ allows you to explore concepts related to absolute temperature and extrapolate toward this theoretical limit.
Steps:
- Use the FizziQ temperature sensor to measure different temperatures
- Measure atmospheric pressure with the barometer at different temperatures
- Plot pressure P versus temperature T (in °C) at constant volume
- Extrapolate the line obtained: it crosses the temperature axis at -273.15°C
- This intersection corresponds to absolute zero where pressure would be zero
Scientific activities on this topic
The concept of absolute zero can be explored through several activities:
- Gas law: https://www.fizziq.org/en/activities/gas-law/
- Thermal convection: https://www.fizziq.org/en/activities/thermal-convection/
- Study of the relationship between pressure and temperature
- Experimental determination of absolute zero by extrapolation
Learn more
History of discovery:
The existence of a minimum temperature was anticipated as early as the 17th century. Guillaume Amontons (1702) noticed that gas pressure decreased linearly with temperature and extrapolated toward a “temperature of absolute cold.”
Jacques Charles (1787) and Joseph Gay-Lussac (1802) refined this relationship. By extrapolating their gas expansion measurements, they estimated absolute zero at around -273°C.
William Thomson (Lord Kelvin) formalized the concept in 1848 by introducing the absolute temperature scale that bears his name. He demonstrated that this limit was fundamental and independent of the type of gas used.
Why is absolute zero unattainable?
The third law of thermodynamics (Nernst theorem, 1906) states that it is impossible to reach absolute zero in a finite number of operations. The closer we get, the harder it becomes to extract energy from the system.
However, physicists have managed to reach extraordinarily low temperatures:
- Laser cooling: a few microkelvins (10⁻⁶ K)
- Bose-Einstein condensates: a few nanokelvins (10⁻⁹ K)
- Current record: about 100 picokelvins (10⁻¹⁰ K)
Zero-point energy:
Even at absolute zero, quantum mechanics predicts that a system retains residual energy called “zero-point energy.” This energy is a consequence of Heisenberg’s uncertainty principle: particles can never be perfectly still.
Phenomena at very low temperatures:
Near absolute zero, remarkable quantum phenomena appear:
- Superconductivity: zero electrical resistance
- Superfluidity: zero viscosity in liquid helium
- Bose-Einstein condensate: all atoms occupy the same quantum state
Formula
Temperature scale conversion:
T(K) = T(°C) + 273.15
T(°C) = T(K) - 273.15
Value of absolute zero:
- 0 K (Kelvin)
- -273.15 °C (Celsius)
- -459.67 °F (Fahrenheit)
Average kinetic energy of a particle:
E = (3/2) kB T
where kB = 1.38 × 10⁻²³ J/K (Boltzmann constant)
At T = 0 K, this classical energy is zero (but quantum zero-point energy remains).
Application examples
- Thermometer calibration and definition of the Kelvin scale
- Industrial cryogenics for gas liquefaction (nitrogen, helium)
- Superconductors for medical MRIs and particle accelerators
- Research in quantum physics and Bose-Einstein condensates
- Cryogenic preservation of biological samples
- Cooled infrared detectors for astronomy
FAQ
Q: Can absolute zero be reached? A: No, the third law of thermodynamics prohibits reaching exactly 0 K. We can approach it asymptotically but never reach it in a finite number of steps. Current records are on the order of 10⁻¹⁰ K.
Q: What happens at absolute zero? A: Theoretically, all thermal motion stops. In practice, quantum mechanics imposes residual energy (zero-point energy). Quantum phenomena such as superconductivity and superfluidity appear at very low temperatures.
Q: Why doesn’t the Kelvin scale have negative values? A: The Kelvin scale is an absolute scale based on the kinetic energy of molecules. Since kinetic energy cannot be negative, temperature in Kelvin cannot be negative either. 0 K corresponds to the minimum possible energy.
Q: What is the lowest temperature measured on Earth? A: In the laboratory, physicists have reached about 100 picokelvins (10⁻¹⁰ K) with laser-cooled atoms. In nature, the lowest recorded temperature is -89.2°C in Antarctica.
Q: Is space at absolute zero? A: No, space has a temperature of about 2.7 K due to the cosmic microwave background radiation from the Big Bang. Some regions may be colder, but not at absolute zero.
Related concepts
Temperature - Kelvin scale - Ideal gas law - Thermodynamics - Kinetic energy - Boltzmann constant - Superconductivity - Superfluidity - Third law of thermodynamics