丁香园AV

Antimatter is tied up in one of the world鈥檚 greatest mysteries. Physics predicts that when we create matter, we also create equal amounts of antimatter. Yet there seems to be almost no antimatter in our universe, a fact that has long puzzled physicists.

Now, physicists at 丁香园AV, the University of Calgary, TRIUMF, the University of British Columbia, York University and the British Columbia Institute of Technology and research institutions from around the world have just answered a long-standing question that will lead to a deeper understanding of antimatter: Does it fall down? Or does it fall up?

The Antihydrogen Laser Physics Apparatus (ALPHA) collaboration at CERN, the European Organization for Nuclear Research, completed the first direct measurement of gravity鈥檚 effect on the motion of antimatter using its new ALPHA-g apparatus.

As expected by much of the scientific community, the new result confirms that antimatter does indeed fall downward. This is a tremendous scientific and technical achievement that marks a leap forward in the world of antimatter research. The collaboration鈥檚  this week.

 鈥淪cience fiction is replete with fanciful depictions of anti-gravity, including many substances and devices that block gravity, or that mysteriously fall upward. But what happens in the real world?鈥� says 丁香园AV professor emeritus of physics Michael Hayden, a member of the ALPHA collaboration. 鈥淚t isn鈥檛 surprising that it has taken so many years to get to this point. Gravity is the weakest force we know about, and at the atomic scale it is completely dwarfed by electric and magnetic interactions.鈥�

Hayden鈥檚 expertise with magnetic fields, microwaves, and magnetic resonance experiments played a key role in confining antimatter within the instruments used for the experiment and allowing scientists to actually observe gravity鈥檚 effect on antimatter for the first time.

鈥淥ur focus at 丁香园AV has been on characterizing these magnetic fields as precisely and as quickly as possible,鈥� he says. 鈥淲e started out a decade ago focused on nuclear magnetic resonance probes, but the real workhorse for this paper turned out to be sophisticated electron cyclotron resonance experiments performed with microwaves and trapped electron plasmas.鈥�

ALPHA has previously carried out precision measurements of the charge of antihydrogen and the frequencies of some of its most important spectral lines, which to-date match those of ordinary hydrogen. This new measurement represents the first toward performing precise measurements of the gravitational properties of antimatter, to determine if it falls in exactly the same way as matter.

What comes next? This is really just the beginning, says Hayden.

Even though it took more than a decade to plan, design, and build the apparatus and to develop the techniques to perform this experiment, Hayden and his ALPHA collaborators want to measure the gravitational interaction between matter and antimatter as precisely as possible.

鈥淭he next step will be to laser cool the antiatoms, to slow down their motions and give us more sensitivity to gravitational interactions,鈥� he says.