Alchemy in the 21st century

7 min readMar 14, 2019

Fig.1: A transmutation circle from Fullmetal Alchemist: Brotherhood[1]

People who watch anime might recognize the image shown above as a ‘transmutation circle’, from Fullmetal Alchemist. But what is transmutation, and what is ‘Alchemy’ in the first place?

Alchemy is a proto-science, an older form of what we call ‘Chemistry’ today. While it was practiced all over the world, there were two fundamental things Alchemy sought to accomplish:

Conversion of base metals (like Iron) to noble metals (like Gold). It was termed as transmutation of base metals to noble metals.
Derivation of the Elixir of life, which grants the user immortality.

The Holy-Grail-of-sorts of Alchemy was the Philosopher’s stone, which could convert any metal to gold, and could manufacture any amount of the Elixir of life. Sounds cool, huh?

Except, it didn’t work.

The basic underlying idea for metal transmutation is:

All materials are made up of the 5 elements: Earth, Water, Air, Fire, Ether. If a metal can be broken into its constituent ‘elements’, then recombination in a different proportion can be done to convert any metal to gold.

Great idea. Though, today we know metals are made of Atoms, rather than the 5 elements. However, if it were just atoms, metal transmutation should be possible, if we strip down a piece of metal into its constituents, right?

Almost. Except, atoms have something called a ‘nucleus’, which is fundamentally different for different elements. A nucleus basically is a set of neutrons (which have no charge) and protons (which are positively charged). Different elements have different number of protons, though they might have the same number of neutrons.

So can we add or remove protons from base metals, and transmute them to gold?

Probably.

On a winter day in 1938, Lise Meitner and her nephew Otto Frisch were pouring over results of Otto Hahn — he had bombarded Uranium atoms with neutrons. Hahn and Strassmann had discovered the presence of Barium as a product of the neutron bombardment, but these two gentlemen were chemists — they did not quite understand the physics behind the reactions. Thus, using George Gamow’s liquid drop model, Meitner and Frisch identified the nuclear fission process, in which a heavier element breaks up into lighter elements on bombarding with neutrons. Essentially, we can remove protons and neutrons from the nucleus, thereby converting heavier elements to lighter elements[3].

Hans Bethe, in 1939 described the process of elemental fusion in stars to transmute lighter nuclei to heavier nuclei — to explain the mechanism of energy generation in stars (though Eddington had proposed a cruder version much earlier). This was done by his theory of the p-p cycle, which involved converting Hydrogen — the lightest element — to its isotope Deuterium, and then to Helium. Thus, we can fuse lighter elements to heavier elements[4].

This seems to be a free lunch — we know how to go from lighter to heavier elements, and the other way round. And as we know, there is no free lunch in science. So are there any caveats?

Yes. The Binding energy curve:

The figure above shows something called the ‘Binding energy curve’. It is a measure of how stable a given element is — the higher the binding energy per nucleon, the more stable an element is. The most stable element is thus Iron — meaning all fusion and fission products will stop at Iron, and proceed no more.

Gold, we know has higher atomic mass than Iron, and thus lies to the right of the plot. Hence, while we could probably convert Gold to Iron, we cannot go the other way round. It seems nature would not have us transmute any metal to gold after all!

Or is it? How did the gold (which people use right now) come into existence? Heck, how did the unstable Uranium form in the first place?

It so happens this is a very deep question. To answer, we will need a short detour to cosmology.

George Gamow, an eminent Russian physicist, set his graduate student Ralph Alpher to work on what kinds of elements might have been formed in the Big Bang (this was in 1948, and remember, Big Bang was a joke at that time. Almost the whole world believed in the Steady State theory, then). Since the universe was a soup of particles at Big Bang, there were no elements per se — just a soup of protons and neutrons. Alpher figured out the elements can be formed, and this was later refined to show elements only till Lithium might be formed — again due to stability issues[6]. Thus, primordially, we have had only light elements in our universe — which further adds to the conundrum: How in the world did Gold and Uranium form in the first place?

In 1957, Margaret and G.R. Burbridge, William Fowler and Fred Hoyle conjured up something called the ‘r-neutron capture’ process. Jargon apart, the process is simple, so to speak: In a neutron rich environment, nuclei like Iron rapidly capture neutrons and grow to heavier nuclei, thus forming elements in the Lanthanide and the Actinide series. There is a slower version of the process, called the ‘s-process’, which proceeds only till the Actinides[7]. These are technically not fusion reactions, so are not quite restricted by the Binding energy seen in Fig.2.

The capture processes can happen in the core of a collapsing star, which is undergoing a Supernova. Sometimes, the expanding ‘bubble’ of supernova can produce a ‘shock’ due to its large velocity, and perform fusion to produce elements. But, are these events enough to produce the Gold we see around us today?

Seems there are better methods!

Fig.3: Neutron star-Neutron star merger event.

We know this. We have seen these simulations over the web so much now, that all of us here might be armchair experts in Gravitational Wave observation (while certainly not downplaying the immense complication involved in these observations!).

Using data from observation run of August 2017, researchers at LIGO looked at the merger of two Neutron stars (for a short review of collapse, look here), in both the Gravitational waves emitted, and the electromagnetic radiation emitted — from Gamma to Radio wavelength. Therein, researchers found evidence of formation of Gold and Platinum — not a couple of grams, but approximately 3 to 13 Earths of Gold[8]. That’s a lot of gold!

How does gold form in these mergers? Apparently, it follows the ‘r-process’ which was formulated in the Supernova, and generates enough material due to the dense structure of the Neutron stars! Thus, Nature performs Alchemy!

Thus, with these discoveries, the periodic table merits to be updated as:

Fig.4: How each element in the periodic table was formed. Elements after Uranium are not naturally occurring, and are created in laboratory. Graphic by Jennifer Johnson[9].

Humans have been struggling to transmute base metals to gold for centuries now — on the way formulating the entire branch of chemistry. Some big names have always been associated with alchemy — Isaac Newton (yep, the gravity guy — among other things), Robert Boyle (Boyle’s law, anyone?), etc. However, we see here how beautifully nature manufactures heavy metals, and transmutes Hydrogen to Iron,Gold, and all the way to Uranium. The processes which create these elements are some of the most violent ones which occur in our universe — remember that when you wear gold the next time!

But can we, as a civilization exploit and perform this alchemy at whim? Probably not. The densities required for the r process to occur are 10²⁴ free neutrons per centimeter³ — that’s much denser than our atmosphere here at mean sea level, at a temperature of 1 billion Kelvin — hotter than the core of Sun!

Such extreme conditions are not possible to be reached by us — at least not right now. However, there could exist an advanced civilization capable of bringing two Neutron stars together, and making them merge to form gold — probably, it would be the same kind of civilization which saves Cooper and the entire humanity in Interstellar!

In creating gold, we totally forgot the Elixir of immortality and the Philosopher’s stone. Tell you what, people are not immortal — ideas are. That, in essence, is the Elixir of immortality.

And as for the Philosopher’s stone, it simply doesn’t exist. Yet.

For people interested in knowing more, and thirsty for dirty technical details, juice in the references below!

References

Technical references:

Supernova nucleosynthesis: http://www.int.washington.edu/PHYS554/2011/chapter7_11.pdf
r-process in nucleosynthesis: http://jhguth1942.tripod.com/cosmofluorescence/id2.html
The original r-process paper by the Burbridges, Fowler and Hoyle: Synthesis of the Elements in Stars: E. Margaret Burbidge, G. R. Burbidge, William A. Fowler, and F. HoyleRev. Mod. Phys. 29, 547 — Published 1 October 1957.
NS-NS merger event: Simplified article — http://news.mit.edu/2017/ligo-virgo-first-detection-gravitational-waves-colliding-neutron-stars-1016
NS-NS r-process paper: Benoit Côté et al 2018 ApJ 855 99, doi: https://doi.org/10.3847/1538-4357/aaad67
Radio observation of the merger event: A radio counterpart to a neutron star merger by Hallinan.G. et.al, Science 22 Dec 2017 : 1579–1583.

Alchemy in the 21st century

References

Technical references:

Written by Vishal Upendran