Produce anti-particle anti-energy

Ten things you didn't know about antimatter

In the book Angels and Demons Professor Langdon tries to save Vatican City from an antimatter bomb. And in Star Trek, the collision of matter and antimatter provides energy to propel the spaceship Enterprise faster than the speed of light. But antimatter isn't just the medium of science fiction - while these scenarios are stretched, there are still plenty of facts about antimatter that will tickle your brain cells.

1. Antimatter should have destroyed all matter in the universe

Antimatter particles are almost identical to their matter counterparts, except that they have the opposite charge and rotation. Matter and antimatter particles are produced as a pair and when they meet they instantly annihilate each other, leaving nothing behind but energy.

This means that the big big bang should have produced and destroyed the same amount of these particles. So why do we exist in a universe that is almost entirely made of matter? As far as physicists can explain, this happened because, in the end, one extra particle of matter for every one trillion (109) The matter-antimatter pair remained there. Physicists work very hard to explain this asymmetry.

2. Antimatter is closer than you think

Small amounts of antimatter keep raining down on the earth in the form of cosmic rays - energetic particles from space. These antimatter particles reach our atmosphere at speeds from less than a square kilometer per century to more than 10,000 per square meter per second. Scientists have also found evidence of the production of antimatter from cyclones.

But other sources of antimatter are even closer to home. For example, bananas release a positron - the antimatter equivalent of an electron - approximately every 75 minutes. This happens because bananas contain a small amount of potassium-40, a naturally occurring isotope of potassium. When potassium-40 breaks down, it occasionally spits out a positron in the process.

Our body also contains potassium-40, which means that positrons are also emitted by us. Since antimatter is immediately extinguished when it comes into contact with matter, these antimatter particles are very short-lived.

3. Humans have only produced a small amount of antimatter

Matter-antimatter annihilations have the potential to release a large amount of energy. A gram of antimatter could produce an explosion the size of a nuclear bomb.

Scientists make antimatter in experiments, but the amount made is tiny. All antiprotons that are produced at the Fermilab Tevatron particle accelerator (now no longer active) only added up to 15 nanograms, and CERN’s so far only to about 1 nanogram.

The problem lies in the efficiency and cost of producing and storing the antimatter. It would cost approximately 25 million billion kilowatt-hours of energy and over a million billion US dollars to produce 1 gram of antimatter.

4. There is such a thing as an antimatter trap

In order to study antimatter, one has to prevent it from being annihilated by matter. Scientists do this by trapping charged particles, such as positrons and antipositrons, in devices called stall traps. These traps are comparable to small accelerators. Inside, particles swirl around as magnets and electric fields keep them from colliding with the wall of the trap.

However, stall traps do not work with neutral particles, such as anti-hydrogen. Because they have no electrical charge, they cannot be captured by electrical fields. Instead, they are held in Ioffe traps, which take advantage of the particles' magnetic properties. Ioffe traps work by creating a region of space where the magnetic fields increase in all directions. The particles are attracted to the areas with the weakest magnetic field, just like a marble rolling in a ball eventually reaches the ground.

5. Antimatter could fall off

Antimatter and matter particles have the same mass, but differ in properties such as electrical charge and rotation. The Standard Model - the theory that best describes particles and their interactions - suggests that gravity should have the same effect on matter and antimatter; nevertheless it has to be shown first. Experiments at CERN such as AEGIS, ALPHA and GBAR are trying to find out.

Observing the effect of gravity on antimatter is not as easy as watching an apple fall from a tree. These experiments need to trap antimatter or slow it down by cooling it down to temperatures just above 0 degrees. And because gravity is the weakest of the fundamental forces, physicists must use the uncharged antimatter particles in these experiments to prevent interference from the much stronger electrical forces.

6. Antimatter is researched in particle accelerators

You have heard of particle accelerators, but did you know that there are also particle decelerators? CERN has a machine called the Antiproton Decelerator, a storage ring that can capture and slow down antiprotons in order to study their properties and behavior.

In circular particle accelerators like the large hadron storage ring, particles get a shot of energy every time they stop rotating. Decelerators work backwards; instead of a burst of energy, the particles are kicked back to slow down their speed.

7. Neutrinos could be their own antiparticles

A matter particle and its antimatter partner carry opposing charges, which make them easy to distinguish. Neutrinos - almost massless particles that rarely interact with matter - have no charge. Scientists believe they could be Majorana particles, a hypothetical class of particles that are their own antiparticles.

To determine if this is the case, scientists look at what is known as neutrino-less double beta decay. Some radioactive nuclei decay at the same time, releasing two electrons and two neutrinos. If neutrinos were their own antiparticles, then in the aftermath of the double decay they would annihilate and scientists would only observe electrons.

Finding Majorana neutrinos would help explain why matter-antimatter asymmetry exists. Physicists suggest that Majorana neutrinos can be either heavy or light. The light ones exist today and the heavy probably existed right after the Big Bang. These heavy Majorana neutrinos would have to have decayed asymmetrically, leaving behind a small excess of matter that allowed our universe to exist.

8. Antimatter is used in medicine

Positron emission tomography uses positrons to produce high resolution images of the body. Positron-emitting radioactive isotopes (like those in bananas) are linked to chemical substances, such as glucose, that are naturally used by the body. This compound is injected into the bloodstream, where it breaks down naturally, releasing positrons that hit the electrons in the body. These particles annihilate with each other and produce gamma rays that are used to reconstruct images.

Doctors can already target tumors with precise beams of protons that only release their energy after penetrating healthy tissue. But scientists working on CERN's antiproton cell experiment (ACE) have instead studied the effectiveness and usefulness of antiprotons, which add an extra boost of energy. The technique has been used effectively in hamster cells, but scientists have yet to conduct the studies in human cells.

9. Leftover antimatter could still be dormant in space

To solve the problem of antimatter-matter asymmetry, scientists are looking for leftover antimatter from the Big Bang. They are looking for these particles with the help of the alpha-magnetic spectrometer (AMS), a particle detector on the international space station.

The AMS contains magnetic fields that bend the path of the cosmos particles to separate matter from antimatter. Its detectors evaluate and identify the particles as they fly through.

10. Antimatter could fuel spaceships

Just a handful of antimatter could produce a huge amount of energy, making it a popular fuel for future science fiction vehicles.

Antimatter rocket propulsion is hypothetically possible, but no technology is currently available to mass-produce or collect the antimatter in the required volume. Someday, when we find a way to create or collect enough antimatter, antimatter-powered interstellar travel may become a reality.

Acknowledgment

This article is reproduced with the kind permission of SymmetryMagazinew1in which it was published as the original.

Web links

  • w1 - Symmetry-Magazin is a free online magazine that covers particle physics. It was jointly established by the Fermi National Accelerator Laboratory and the SLAC National Accelerator Laboratory (USA). To see the original article, visit theSymmetry website.

author

Diana Kwon is a freelance science journalist based in Berlin, Germany. Her work is in numerous editions of the Scientific American, Quartz and New Scientis in print and online.