We all know that some things feel hot, and others cold, but is
there more to temperature than that?
When an object feels hot, the atoms inside it are moving fast in random directions,
and when it feels cold, they are moving slowly. Our body
interprets that random atomic motion into what we feel as hot and
cold, and a thermometer interprets that atomic motion as a certain
number of degrees.
So when I'm heating something, I'm just making its atoms move faster?
Exactly. If the object is
a solid the atoms are vibrating back and forth, and if it is a gas
like the air, the atoms are flying around much like little
balls.
They are bouncing around so that sometimes an atom is going fast,
and other times it is slow. It seems like its temperature must be
changing all the time.
In a group of atoms there is always a
whole range of speeds, but while the speed of one atom changes,
the average of all of them does not. See how each time an atom slows down, there
has to be another that speeds up? So temperature is really describing the
range of speeds of the bunch of atoms together. Physicists
often like to use a different scale for temperature that is
directly related to the speed atoms are going in a gas. This is called the
Absolute scale, and one degree on it is the same as one degree
centigrade, which is 9/5 of a degree Fahrenheit. The difference between
the Centigrade and Absolute scales is the zero label.
What is so "Absolute" about it?
Well, look what happens if you set the temperature of the atoms
in the box as low as it can go.
The atoms are stopped.
So that is as cold as the atoms can be.
We call that Absolute Zero.
I get it! When the atoms are all stopped the gas is ABSOLUTELY
as cold as can be!
Yes, and that is really cold. The thermometer shows a comparison of the
Absolute (also known as the Kelvin) and Fahrenheit scales of
temperature. Absolute Zero is -459 degrees Fahrenheit.
Is anything actually at Absolute Zero?
The coldest place in
nature is the depths of outer space. There
it is 3 degrees above Absolute Zero.
Why doesn't it get down all the way to Absolute Zero?
That is a really interesting question.
It turns out that the heat left over from the Big Bang that
created the universe is
everywhere, and it keeps the temperature in space from going any lower than
3 degrees Kelvin.
Measuring this temperature (offsite link) is the strongest evidence
we have that the
Big Bang (offsite link) actually happened. However, people can do a
lot better than nature when it comes to getting things cold. For
almost a century we have been able to build refrigerators that get
to lower than 3 degrees above Absolute Zero, and for quite a while we have
been able to even get lower than 1/1000 of a degree (offsite link) above Absolute Zero.
However, a big step was when Cornell and Wieman cooled a small sample of
atoms down to only a few billionths (0.000,000,001) of a degree above
Absolute Zero! That was what they needed to do to see
Bose-Einstein condensation.
We all know that some things feel hot, and others cold, but is
there more to temperature than that?
When an object feels hot, the atoms inside it are moving fast in random directions,
and when it feels cold, they are moving slowly. Our body
interprets that random atomic motion into what we feel as hot and
cold, and a thermometer interprets that atomic motion as a certain
number of degrees.
So when I'm heating something, I'm just making its atoms move faster?
Exactly. If the object is
a solid the atoms are vibrating back and forth, and if it is a gas
like the air, the atoms are flying around much like little
balls.
They are bouncing around so that sometimes an atom is going fast,
and other times it is slow. It seems like its temperature must be
changing all the time.
In a group of atoms there is always a
whole range of speeds, but while the speed of one atom changes,
the average of all of them does not. See how each time an atom slows down, there
has to be another that speeds up? So temperature is really describing the
range of speeds of the bunch of atoms together. Physicists
often like to use a different scale for temperature that is
directly related to the speed atoms are going in a gas. This is called the
Absolute scale, and one degree on it is the same as one degree
centigrade, which is 9/5 of a degree Fahrenheit. The difference between
the Centigrade and Absolute scales is the zero label.
I get it! When the atoms are all stopped the gas is ABSOLUTELY
as cold as can be!
The coldest place in
nature is the depths of outer space. There
it is 3 degrees above Absolute Zero.
Why doesn't it get down all the way to Absolute Zero?
