This week on "Ask a Physicist" we have a doomsday twist. Is it possible to make strange new elements that could ultimately destroy the world or are you destined to be Mendeleev's bitch? In this week's column, we find out.
Today's question comes to us from our own Annalee Newitz and Charlie Jane Anders who ask:
Could there be elements in the universe that we haven't discovered yet? Or is the periodic table all we're going to get?
Whenever I get an email from the management, I generally am forced to conclude that they have some sort of doomsday scenario in mind. Today's question seems innocuous, but lurking beneath the surface, I'm pretty sure I detect their evil scheme.
Before I get started, I'd like to put out a reminder to continue sending me your questions about life, the universe, and everything. Now, on to business.
How chemistry works
Let's begin with a simple question: what makes one element different from another?
All atoms are made up of two constituents, a nucleus in the middle, and electrons on the outside. The nucleus can be further broken down into protons and neutrons, but smashing nuclei apart requires, well it obviously requires the energies in nuclear reactors. From the viewpoint of chemistry, one nucleus is exactly the same as the other, so long as it has the same number of protons The electrons — the part of the atom that actually gets shuffled around in chemical processes — only care about the charge of the nucleus, and thus, the protons.
The periodic table is fundamentally nothing more than a counting tool for protons. Hydrogen has an atomic number of one, so there's one proton. It's what makes hydrogen hydrogen. Even wacky versions — isotopes — of hydrogen like deuterium and tritium which have 1 and 2 neutrons, respectively, behave the same as ordinary no neutron hydrogen from a chemical perspective. Helium has an atomic number of two, and can have either 1 or, much more commonly, 2 neutrons, and so on.
To give another example, the most common isotope of carbon has 6 protons (by definition) and 6 neutrons. However, up in the stratosphere, carbon-14, a version with 8 neutrons is created. It only accounts for about 1 carbon in a trillion, but it ends up being useful. Chemically, carbon-12 (aka normal carbon) and carbon-14, are exactly the same so plants and animals (through breathing and eating other living things) have the same 1 in a trillion ratio in our bodies — until we die. At that point, the carbon-14 starts decaying, and as you probably know, we can use this fact to figure out how long ago something or someone lived.
There are lots more isotopes, but Annalee and Charlie Jane were looking for fundamentally new elements. The short answer is that we're not going to get something midway between hydrogen and helium, or something like that, since the elements are all determined by how many protons are in them, and there has to be an integer number. However, we can (and have) made ones at the high end of the periodic table.
And a bit of nuclear physics
For instance, in 2009, a group of Russian scientists discovered element 117, Ununseptium. When I say, "discovered", I really mean that they made it in a lab, which means, in this case, smashing the holy hell out of calcium and berkelium (itself, something you also have to cook up in a lab) into one another. The result was something on the order of half a dozen atoms, and they only stuck around for the merest of instants.
The problem is that massive particles, like ununseptium, which is nearly 300 times the mass of ordinary hydrogen, tend to be fairly unstable. In general, they'll want to decay into lighter particles as quickly as possible, and in the process, they release their energy in the form of radiation. This is one of the reasons that uranium and plutonium are such nasty stuff.
For ununseptium, the problem is that it has a half life of less than a 10th of a second, so while it's "stable" by nuclear standards ("unstable" things have a half-life of 10^-10 seconds or so), it's nothing that's going to exist in nature. In principle, we make heavier elements, but we're not going to discover them lying around.
Atoms aren't the only option
But if you want to go off the periodic table script entirely, there is another option: don't use protons and neutrons at all. As you may recall (or as Alasdair explained in an excellent article a while back), protons and neutrons are made of more fundamental particles, known as quarks. In particular, they are made of the two lightest quarks, up and down. Protons are made of up-up-down, and neutrons of up-down-down.
But there are 4 other quarks out there. The next lightest is the strange quark, and in terms of charge, it looks just like a down quark. We could create elements out of hyperons, rather than just protons and neutrons. The difference is that hyperons contain strange quarks.
For instance, the Sigma hyperons have the same charge and similar mass to protons or neutrons, which means that elements made from Sigma hyperons would be identical to those made of protons and neutrons. The only problem is that they decay quickly — very quickly. The Sigma^+ (roughly the equivalent of a proton) decays in about 10^-10 seconds, and the Sigma^0 (which takes the place of the neutron) decays in 10^-19 seconds.
Not everyone sees the (fleeting) production of these particles as good news. One of the doomsday scenarios that people were concerned about with the Large Hadron Collider (LHC) was that "Strangelets," (the equivalent of an atomic nucleus but with at least one hyperon in there) were supposed to bond to ordinary matter, and somehow the ordinary matter would catlyze into lower-energy strangelet matter. Ostensibly, this would continue indefinitely, basically destroying the planet and everything on it. If it sounds familar, this is basically the plot from Superman Returns, but with Strangelets replaced by kryptonite.
Photo by Scott Beale
I more or less take it for granted that Annalee and Charlie Jane wanted to build some sort of strangelet bomb, and that was the entire point of their question.
My co-author, Jeff Blomquist, and I took the rather bold position that concerns of strangelets, mini black holes, and other doomsday scenarios stemming from the LHC were, to put it gently, a bit misguided and dispel them in Chapter 4 of our book. Since we wrote it before the LHC came on line and the earth was not, in fact, destroyed, I think we deserve some credit. We probably wouldn't be quite so smug if the world were destroyed, but that's a chance we were willing to take.
Dave Goldberg is the author, with Jeff Blomquist, of "A User's Guide to the Universe: Surviving the Perils of Black Holes, Time Paradoxes, and Quantum Uncertainty." (follow us on twitter, facebook, twitter or our blog.) He is an Associate Professor of Physics at Drexel University. Feel free to send email to firstname.lastname@example.org with any questions about the universe.
Top two images via Shutterstock