(The DNA molecule pictured was not the first molecule)
‘Day 2’ Things were pretty quiet on a Saturday night at the Universe bar 13,800,000,000 years ago. The protons and the neutrons had been busy capturing electrons for the last 380 million years, well most of it anyway, creating all the stable atoms we were going to need to make stars and planets and zebras. But that was getting a bit monotonous.
In the open reaches of space, vast clouds of stable atoms of helium and hydrogen would later coalesce under gravity to ignite the nuclear fires that become the galaxies of stars that have come and gone in the inconceivable length of time since the beginning, but for now, some were joining forces to create organic molecules.
At least the lights were on. Space was ‘clear’ now that the electrons were under control. Photons had previously been restricted by the unattached electrons floating about but now the electrons were bound up in atoms of hydrogen and helium (mainly) the photons were free to travel. Infinitely.
The period before this, before space was ‘clear’ is called, predictably, The Dark Ages. No prizes for imagination there. The roundup and capture of the electrons by the neutrons making the space soup clear is called The Recombination and the issue of the travel permits for the photons is called Decoupling.
Stable atoms of both hydrogen and helium were all over the place, but seen one you’ve seen them all. What the universe needed was some molecules and that’s exactly what was about to happen. About 13,500,000,000 years ago, simple organic molecules were formed but before we get there we should look at the helium atoms.
Helium may be colourless, odourless and tasteless and settles for second place in abundance after hydrogen, but it has other redeeming features. It is virtually inert so it does not react with other materials and when compressed with hydrogen under sufficient gravity, it makes a wonderful star.
While the helium does not ‘burn’, it does make up about 24% of stars like our Sun (which is not due on the scene for another 8,900,000,000 years) but the fusion of the hydrogen component of the star makes more helium, eventually turning all the hydrogen into helium.
It really is a fascinating gas. Almost all the helium in the universe, despite all the new stuff being made by stars and the gas created by the degradation of uranium, was created in the first few minutes after the Big Bang.
It remains a liquid no matter how cold it gets and you need to add a considerable amount of pressure as well to make it a solid. Even so, it is difficult to tell the difference but it gets even weirder. As a liquid, helium is a superfluid which means it has no measurable viscosity. It can flow over, under or through almost anything, making it a little difficult to work with. In fact it will even crawl up the side of containers to escape. Try to imagine that.
Perversely it expands as it gets colder and it’s so crystal-clear, you need to float something like a piece of polystyrene foam on top so you can see the surface. At certain temperatures it will even leak through the solid bottom of a container.
Most space helium is the plasma version quite unlike what is found on earth. The charged particles show up here as part of the solar wind that provides us with the spectacular aurora at the poles.
Despite its abundance in space, helium, well known for its Donald Duck voice trick, is relatively rare on earth. Most of our local helium is a result of radioactive decay in minerals of uranium and thorium making about 3000 metric tons a year. In order to capture the gas, one needs to be attentive as when it is released, the earth’s gravity is not sufficient to stop it escaping into space.
It was first detected as part of the spectrum of sunlight in 1868, a few years later, an Italian named Palmieri found the first helium on earth when he was analysing the lava of Mount Vesuvius. The first significant quantities were found (in concentrations of 1 or 2%) in natural gas fields in America, still the largest supplier of the gas today.
The first primary use of helium was for air-ships, although later it became the gas of choice as a shield against oxygen in arc welding and handy for atomic bombs too. In 1927 America banned the export of what was a rare commodity and this forced the German Zeppelins to use hydrogen and we know how that turned out. By the mid 1990s, Algeria was producing enough helium to supply all Europe and is now the world’s second biggest producer.
Helium is used in purging containers, welding shielding, controlled atmospheres and leak detection but small amounts are also used in breathing mixtures for underwater work (and party balloons).
However, the main use for helium today is in cryogenics, primarily as a cooling liquid for the superconductor magnets in the medical world’s 25,000 MRI scanners. Within the MRI scanner, strong and uniform magnetic fields are produced which provoke the excited hydrogen atom protons in the water molecules of human tissue. This is what creates a signal that is processed to form an image of the body.
We’ve all heard of the largest of all molecules, DNA, but molecules come in more than a few types and sizes. At its heart though, a molecule is just two or more atoms that get together. In the case of DNA, a lot of atoms get together. While this is the standard way of defining a molecule, the exception is a branch of science called ‘the kinetic theory of gases’ where they often call any gas particle a molecule. When two atoms of hydrogen are connected, they form a homonuclear molecule, but when they are joined by an atom of oxygen we get a compound chemical called water. H2O.
Generally speaking, molecules are the basic elements of ‘soft’ matter, water, trees, animals, the atmosphere and are called organic molecules to emphasise the point.
‘Hard’ matter, rocks, metals, gems, diamonds, glass and salts are also made of atoms of course, but the atoms are chemically bonded in a different way so they have no identifiable molecules.
Molecules made of two part hydrogen to one part oxygen (water) were very plentiful and some formed in large clumps to become ice and dust comets. 380,000,000 years have passed since the Big Bang and now organic molecules are common throughout the universe and eventually, will be coming our way.
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