|What is the closest to absolute zero that has
ever been reached?. What would happen to a
substance if it were cooled to absolute zero?
|Question Date: 2002-12-05|
Absolute zero is defined as zero degrees
The closest recorded temperature to absolute zero
that I could find is 0.0001K, for helium gas.
Your question about what would happen to an
object cooled to absolute zero is a great one! All
molecules are constantly in motion (the bonds
between atoms are vibrating and changing shape).
The speed of this motion is dependent on the
temperature of the molecule. As you can
probably guess, motion is faster at higher
temperatures. Changes in molecule motion with
temperature are responsible for phase changes.
Water vaporizes at
high temperatures because as the water molecules
move faster they bump into one another more often,
pushing each other away and taking up more and
more space, eventually forming a gas (steam).
Water freezes at low temperatures because as
the water molecules slow down they
coalesce, or come together like pieces in a
puzzle to form a crystal- like matrix.
(Why is ice LESS dense than
water, then? If the molecules are moving slower,
they should be closer together, right? Ice is
less dense than water -- it floats.)
Even when water
freezes, the molecules are still vibrating. Only
at absolute zero do molecules stop moving
completely. What sort of phase change would
this cause? According to Einstein, who based
his work on an Indian physicist Satyendra Nath
Bose, this would result in a completely new form
Albert Einstein speculated that when
molecules stop moving, the atoms would fall
together and merge into one atom. The individual
atoms (oxygen and hydrogen, in the case of water)
would loose their identities and form what
Einstein called a "superatom" or what we
now call a Bose-Einstein Condensate.
Last year, Carl E. Wieman at the
University of Colorado in Boulder won the Nobel
prize for his work on Bose-Einstein Condensates.
The closest to absolute zero anyone has reached
is around 150 nano Kelvin. The group ended up
receiving the 1997 Nobel Prize in Physics for it.
They got the prize because they ended up proving a
theory called Bose-Einstein Condensation
which had been made decades before it was proven.
They achieved the cooling by taking
already cold vapor of atoms, (3K 87Rb atoms) and
slowing them down further with a 3 dimensional
laser setup. If you want more detail your welcome
to look at
this link here
For the really good stuff, look up Steven Chu
on the web. He has some good educational equipment
hiding somewhere. A quick explanation of
Bose-Einstein Condensation (or BEC) is that due to
quantum mechanics, there is a limit on how well
you can know the product of a particles momentum
and position at the same time. This theorem is
called the uncertainty principle. So if you
know exactly what the velocity of a particle is,
you can't know its position exactly no matter how
good your equipment is. You do however know a
region that the particle could exist. If you had
a billion particles, each with the same velocity,
each time you looked you would find the particle
in a different place.
So what Einstein
theorized was that if you could slow down an atom
enough, due to quantum mechanics the atom size
would spread out. If you kept slowing the atom
down, it could overlap with other atoms. That is
exactly what happened, the atoms ended up
spreading out enough that the atoms existed as a
single entity, rather than a collection of
PS. An interesting fact:
The navy funded the research. What the grant
proposal promised was the possibility of the most
accurate clock in the world. As far as I know no
one intends to ever build the clock.
The record for the coldest temperature which
has ever been reached depends upon what you
kind of substance you are interested in. The
coldest temperature which a solid object has been
cooled to is about 60 microKelvin, or 60
one-millionths of a degree above absolute zero.
Certain gases have been cooled to about one
nanoKelvin, or about one one-billionth of a degree
above absolute zero.
However, this temperature can't be maintained
indefinitely because the gas slowly solidifies,
and warms up when it does so. In a certain
kind of machine called a "nuclear
demagnetization refrigerator", it is possible
to take a piece of copper and cool only the atomic
nuclei to temperatures of roughly 1/4 of a
nanoKelvin. This is kind of an unusual situation
though, where the nuclei of all the atoms are very
cold, but the electrons of the atoms are much
warmer. You can read some more about nuclear
demagnetization refrigerators at
and some about the very cold gases at
link I don't know what would happen to a
substance if it were cooled to absolute zero.
Certainly very many changes happen to it on the
way to absolute zero.
If you think of water for example, it changes from
steam at high temperatures to liquid water as it
cools. When it gets still colder it becomes ice,
which is a solid. These changes are examples of
phase transitions, in which a substance
changes its properties dramatically as the
temperature changes. Some substances (like the
element dysprosium) become magnetic when
they get colder; others become liquids that flow
without any friction at all (like helium); still
others allow electrical current to flow through
them without any resistance (like aluminum).
Mostly these changes take place because as the
substance gets colder, the vibrations of the atoms
in the substance become weaker and weaker. At
absolute zero the vibrations nearly stop all
together - the only vibrations left are called the
"zero-point motion", but they can't produce any
I'm not sure what the current record is, but I
believe it's around a few billionths of a degree
above absolute zero. For reference, the coldest
parts of space appear to be about 3 Kelvin! As
you approach absolute zero, atoms and molecules
lose their energy and slow down. At absolute zero,
atoms and molecules in a system would be in their
lowest possible energy state. However,
according to the Third Law of Thermodynamics,
it is not possible to bring a system down to
However, even though absolute zero
cannot be achieved, dramatic changes in the
physical properties of matter (such as
Bose-Einstein condensation and superconductivity)
can emerge at temperatures near absolute zero.
Click Here to return to the search form.
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.