One of my favorite things about the universe is that it shouldn’t exist. Not in like an existential why are we even here? way, but in a real-deal “god who?” science-says-so way. It should have blown itself up just as quickly as it Big Banged its way into existence.
That’s because of antimatter, the stuff that is opposite to “proper” matter in every way and when it comes in contact with regular old matter (ROM), will annihilate both itself and the ROM in a flash of gamma rays. Paul Dirac figured antimatter out in 1928 while working to put Einstein’s theory of relativity together with quantum mechanics. He realized that for electrons to exist, they needed to have an antielectron partner. All of them, and all of the ROM should have immediately met its antimatter mirror and annihilated before any of the great This could have happened.
An electron, by existing, leaves a sort of imprint or hole in the vacuum, and that electron imprint is actually a positron, an electron’s opposite and a very real thing. A positron is a positively charged electron. It gets together with an antiproton, a negatively charged proton, and you get an “anti” atom, like antihydrogen: one positron and one antiproton. Using the appropriate antiparts you could make an antianything, including an antiyou that looked an acted just like the ROM you.
We’ve found all of these things (not the antiyou, the antiparts). It’s not like dark matter, a thing that should exist but we can’t see it. Positrons are actually used every day by medicine in PET scans. A certain sort of radioactive isotope is injected into the body that emits positrons as the isotope decays, and these positrons travel a very little ways through the body’s tissue until they hit an electron and annihilate, giving off gamma rays. Which are detected by the PET system and used to make 3D maps of your insides.
The Inevitable pipe dreams: bombs and energy
Theoretically, we could use antimatter to power spaceships: the energy released in an antimatter collision is three times that of a nuclear reaction and leaves no waste. In 2004, the U.S. Air Forced copped to being interested in antimatter for weapons uses—again, the energy release is massive and “clean.” In a speech at the time, the Air Force’s Kenneth Edwards explained that the energy potential of antimatter, “is 10 billion times … that of high explosive.”
As far as being used for energy, a Q&A from CERN explains, “There is no possibility to use antimatter as energy ‘source’. Unlike solar energy, coal or oil, antimatter does not occur in nature; we first have to make every single antiparticle, and we have to invest (much) more energy than we get back during annihilation.”
“Antimatter could only become a source of energy if you happened to find a large amount of antimatter lying around somewhere (e.g. in a distant galaxy), in the same way we find oil and oxygen lying around on Earth,” it continues. “But as far as we can see (billions of light years), the universe is entirely made of normal matter, and antimatter has to be painstakingly created.”
The physics community’s response to both of these ideas could be characterized as a polite scoff. If antimatter’s lack of utility in blowing things up or getting us to interstellar space somehow makes it less interesting, the jokes on you.
How to make it
So let’s talk about that painstaking creation. After nearly 20 years of work, it was only last fall that researchers at CERN were able to create and snag an antihydrogen atom for any amount of time. And last week, CERN announced that antimatter has been created and contained – within a magnetic field, or “bottle” – for a considerable 16 minutes. The significance is that now we’re able to study it, probe it, see what it does. And, most importantly, see how it’s different from ROM.
The Alpha experiment’s space at CERN
Last week in a phone interview, I asked CERN’s Jeffrey Hangst — who works specifically at the Alpha antimatter experiment — a very stupid question: what could surprise you about antimatter? It’s stupid because the answer is “anything.” This is the sort of New World research where any increased knowledge entails a surprise. “Nothing I think would surprise us,” Hangst says. “Physics is fundamentally an experimental science. You don’t know anything until you measure it.”
But gravity, a thing we don’t really know much about in terms of regular matter (even its strength), could be something. “I suppose the oddest thing would be if you did a gravitational measurement on antihydrogen and it falls up,” he says. “No one expects that, but we know absolutely nothing about gravity and antimatter. So we have to check that.”
What if researchers can’t find any difference at all between matter and antimatter? “Then you would know that at least, that in the atomic system of antimatter [there is no difference]. That would mean that you could look other places for what’s going on. We usually say that the kind of symmetries that we study—they’re always obeyed until they’re not. You just never know where the exception will come.”
Antihydrogen creation happens at ultracold temperatures
Looking out into the universe, we just see matter. We usually have pretty good explanations for the gamma rays we see, and they don’t involve massive collisions between antimatter and matter stars or galaxies. But, one could imagine a ball of antimatter weaving through the solar system, avoiding any normal matter, until it hits Earth. A one-in-a-trillion-trillion (or something like that) shot of antimatter broken off from some unseen reservoir of antimatter hiding out in the cosmos.
Frank Close starts off his book on antimatter, Antimatter, with a passage about the Tunguska event. If you remember, this is the 1908 incident in which a massive explosion, bright enough to be viewable from London, above a remote area in Siberia essentially made said area a non-area.
This was before nuclear weapons and, as for the source being an asteroid or comet, a crater has never been found. Was antimatter the culprit? It’s been speculated. But certainly not: the debris around the area matches more with the explosion of an asteroid as it entered our atmosphere, and, again, it still seems pretty unlikely that a ball of antimatter wouldn’t have hit something, anything, before impacting Earth’s surface.
In any case, the speculation over that event offers more of an example of the magnitude of antimatter, and what it’s capable of. Somehow that magnitude makes the questions of “where is it” or “what happened to it?” all the weirder.
Reach this writer at firstname.lastname@example.org.Image/video courtesy CERN.