um in the last couple of days there's
been quite a large discussion about some
breakdown of the Large Hadron Collider
this is the huge physics experiment in
um
Geneva and there has been a substantial
loss of helium nobody's quite sure how
much into the experiment now you could
ask why does anybody doing experiments
into the Big Bang need helium and the
answer is that the apparatus is like a
huge
circle and it has charged particles
protons going round and round and so
these particles have to bend around the
corner and to make it Bend they need
very powerful
magnets and the helium comes in for
making the magnets really
powerful and the way you make a magnet
some of you may have done this before is
you take a piece of wire and you wind it
round into a coil like this around my
finger and if you want to make it really
powerful you do make a huge number of
turns of the coil going round and round
and so the strength of the magnetic
field depends on the number of Co coils
and the current Going Through the
Wire and the bigger the current the more
turns the bigger the magnetic field but
of course as you make the wire longer
and longer to get more and more turns
when you put a current through it it
starts heating up just like any sort of
electric heater and if you get it too
big the current will just melt the whole
magnet so if you want a really powerful
magnet then what you do is you have to
make it out of a material which has no
electrical resistance so however much
current you put through within reason it
will not heat up at all because the wire
has no
resistance and to do this you need to
take a material SOC called
superconductor which you cool to very
low temperature and then suddenly it
loses all its electrical
resistance and liquid helium is the best
coolant for doing this because it can
cool materials down to its boiling point
of 4° Kelvin or if you pump on it with a
vacuum pump rather like taking your tea
to boil it at the top of a mountain the
boiling point goes even lower just below
2°
absolute that's -
271 de
centigrade and then you can get really
powerful magnets and whatever has gone
wrong in the LHC is involved in the
magnets suddenly boiling off a large
amount of helium so the reason why
helium has such a low boiling point is
because in a liquid the molecules or in
the case of helium there's only one atom
in the
molecule in a liquid have a positive
interaction they interact they attract
each other which makes it form a liquid
rather than a gas and the stronger the
interaction between the molecules the
higher the boiling point water has
strong interaction between the molecules
so it boils at 100° Centigrade mercury
has an even stronger interaction so it
boils at a higher
temperature and helium has a combination
of being a very light atom and having a
very weak interaction and it is the
combination of very light atom and very
weak interaction that gives this low
boiling point
yeah I'll get different angle cuz means
the same thing two
angles yeah
ready
yeah very satisfying
reaction it's all p in the grass