biostasis.substack.com/p/cryonics-101
4 corrections found
Absolute zero is the temperature at which all molecular motion ceases.
This is not correct in modern physics: matter still has quantum-mechanical zero-point motion at absolute zero.
Full reasoning
NIST explicitly says that while classical 19th-century physics treated motion as stopping at absolute zero, quantum theory does not. On NIST's Kelvin: Introduction page: at absolute zero, matter still has random motion called "zero-point motion". NIST's About Cryogenics page likewise says molecules are in their lowest, but finite, energy state at absolute zero.
So the statement is outdated/classically simplified: absolute zero is not the temperature at which all molecular motion ceases. Thermal motion goes to zero, but quantum-mechanical zero-point motion remains.
2 sources
- Kelvin: Introduction | NIST
According to classical, 19th-century physics, motion completely stops at absolute zero. But according to the quantum theory introduced in the 20th century, matter does have random motion at absolute zero, called "zero-point motion".
- About Cryogenics | NIST
Molecules are in their lowest, but finite, energy state at absolute zero.
The National Institute of Standards and Technology considers the field of cryogenics as that involving temperatures below −180 °C (93 K; −292 °F).
NIST's own definitions do not use −180 °C/93 K here; NIST says cryogenics generally refers to about −150 °C or, often, below 120 K (−153 °C).
Full reasoning
This statement misstates NIST's definition.
On NIST's About Cryogenics page, NIST says that "the term cryogenics has generally been used to refer to temperatures below approximately -150 C" and also that "the cryogenic region is often considered to be that below approximately 120 K (-153 C)". NIST's Cryogen Safety Program similarly defines cryogenic fluids as liquids with normal boiling points below -150°C (123 K).
Those official NIST descriptions contradict the article's claim that NIST considers cryogenics to involve temperatures below −180 °C (93 K). The NIST threshold given in the post is therefore inaccurate.
2 sources
- About Cryogenics | NIST
Over the years the term cryogenics has generally been used to refer to temperatures below approximately -150 C... In terms of the Kelvin scale the cryogenic region is often considered to be that below approximately 120 K (-153 C).
- Cryogen Safety Program | NIST
Cryogenic fluids are defined as liquids with normal boiling points below -150°C (-238°F, 222°R, 123 K).
the Freon refrigerants, hydrocarbons, and other common refrigerants have boiling points above −120 °C.
This overgeneralizes hydrocarbons: some hydrocarbons boil well below −120 °C. For example, methane is a hydrocarbon with a normal boiling point of −161.5 °C.
Full reasoning
The sentence is too broad as written because not all hydrocarbons have boiling points above −120 °C.
NIST's own About Cryogenics page lists methane among common cryogenic fluids and gives methane's normal boiling point as 111.7 K / −161.5 °C, which is below −120 °C. EPA also identifies methane (CH₄) as a hydrocarbon.
Because methane is both a hydrocarbon and has a boiling point below −120 °C, the article's blanket statement that hydrocarbons have boiling points above −120 °C is incorrect.
2 sources
- About Cryogenics | NIST
Table 1. Normal boiling points of common cryogenic fluids ... Methane 111.7 K, -161.5 °C.
- Importance of Methane | US EPA
Methane (CH4) is a hydrocarbon that is a primary component of natural gas.
Tissues stored at 196° C - the temperature of liquid nitrogen - don't decay just five or ten times more slowly than those at body temperature.
This temperature sign is wrong: liquid nitrogen is about −196 °C, not +196 °C.
Full reasoning
Liquid nitrogen's normal boiling point is about 77.4 K, which is −195.8 °C (about −196 °C), not +196 °C.
NIST's About Cryogenics page lists nitrogen among common cryogenic fluids and gives its normal boiling point as 77.4 K / −195.8 °C. So the article's sentence is missing the minus sign and states the temperature incorrectly.
1 source
- About Cryogenics | NIST
Table 1. Normal boiling points of common cryogenic fluids ... Nitrogen 77.4 K, -195.8 °C.