Wednesday Science Limerick: Helium

They say one degree Kelvin is cold
Liquid Helium’s quite uncontrolled
When put in a jar
It’s behaviour’s bizarre
It climbs out – that’s a sight to behold

Helium is a most interesting element. It is the lightest of the chemically inert noble gases and the second commonest element in the universe. It was first discovered because of its spectrum in sunlight – which is why it is called Helium – after the Greek word for the sun ἥλιος (helios). The nucleus, the alpha particle, is also a product of radioactive decay.

It has the lowest boiling point of any substance (4.22 degrees Kelvin) and it is still a liquid at absolute zero, although a solid can be formed at high pressure. Below 2.1768 degrees Kelvin it become superfluid. This is a strange property where a thin film spreads out over all surfaces connected to the liquid and the liquid flows through the film from higher to lower levels. In the diagram the film covers all surfaces of the sealed container and from the outer to the inner bowl until the levels are equal. If the container was not sealed the liquid helium would escape.

In fact there are two isotopes of helium, He4 (2 protons and 2 neutrons) – as described, and He3 (2 protons and 1 neutron) which does not become superfluid until a much lower temperature. These strange properties are hard to understand without some knowledge of quantum physics and the meaning of words like "Boson" and "Fermion" – but should you want to know more the articles on Wikipedia are well written.

For more about the background to these Wednesday Science Limericks, and this one in particular, see below the fold.

My weekly Limericks arose because I started entering Mad Kane’s LimerickCompetition and decided to include some with a science slant. Sometimes the limericks on this blog have first been aired in the competition. This week the rhyme word was “Cold” and they stirred up some discussion. My first two were

The weather on Titan is cold
Saturn's moon is a joy to behold
You'll see mountains of ice
The volcanos are nice
And the rivers are methane I'm told

and

In the Ice Age the weather was cold
And great mammoths walked over the wold
And men lived in a cave
Were courageous and brave
They were huntsmen both fearless and bold

Following favourable comments about my educational limericks I explained

It’s a result of having been to Dartington. My earlier schools taught me how to be conventional - but Dartington taught me that you didn't have to follow the crowd - but could be an individual. I loved science (thanks to Jack Hamshere) and want others to understand the wonders of the world we live in. As a result of entering the competition I now have a regular "Wednesday Science Limerick" on my own blog http://www.trapped-by-the-box.blogspot.co.uk/ which includes details of the background science. Of course I could write "limericks on variations of "boy meets girl and bonk" theme but I would just be one of a crowd.

And followed this up with what is now this week’s “Wednesday Science Limerick”

They say one degree Kelvin is cold
Liquid Helium’s quite uncontrolled
When put in a jar
It’s behaviour’s bizarre
It climbs out – that’s a sight to behold

This attracted the response from Brian Allgar:

Says Christopher, “Helium’s cool”,
But I never learnt physics at school.
Although I may want ’em,
The facts about Quantum
Just mystify me as a rule.

Fred Bortz wrote saying he used limericks in his science writing and made an inaccurate comment relating to He3 and superfluidity – which I corrected with another limerick.

Superfluid H e 4 we know
Is looking for somewhere to flow
While lazy He 3
Just stays where it be
For a fermion’s bound to be slow

Sue Dulley chipped in

The Helium debate leaves me cold:
I doubt that I dare be so bold With a mere BSc (Just a starter degree) As to venture where Drs have strolled.

 Fred Bortz “Indeed, my memory was as fuzzy about the isotopes. In gratitude for the correction:”

Helium's strange when it's cold. Its fluid behavior's quite bold. My memory's flawed, But when my brain's thawed I'll remember what I was once told.

Madeleine Begun Kane wrapped it up with

It all appeared rather involved, But the isotope battle's resolved. Our science-type doctors Had NO need for proctors. Who was right? Who was wrong? That's been solved