To learn more about how antimatter interacts with gravity and whether it too falls down at exactly the same speed as ordinary matter, CERN is busy with two exciting new antimatter gravity experiments that are known as ALPHA-g and GBAR.
While scientists understand that with no friction forces involved, because of gravity, objects with different mass will still fall down at exactly the same rate as each other. However, what is not understood yet is if the same is true with antimatter and ordinary matter. According to CERN, it is hoped that their two bold experiments will finally answer this question.
The ALPHA-g antimatter gravity experiment at CERN is very close to the ALPHA experiment, which uses antiprotons from the Antiproton Decelerator (AD) and creates neutral antihydrogen atoms by binding the antiprotons with positrons that come from a sodium-22 source. The resulting neutral hydrogen atoms are then kept safely inside of a magnetic trap, so that microwaves or laser lights can be shone on them, which allows their internal structure to be studied.
The APHPA-g experiment is very similar when it comes to both the creation and trapping of antiatoms, with the slight variation of the experiment being a vertical set-up. This is useful to scientists as it allows them to look at these vertical positions and “precisely measure the vertical positions at which the antihydrogen atoms annihilate with normal matter once they switch off the trap’s magnetic field and the atoms are under the sole influence of gravity. The values of these positions will allow them to measure the effect of gravity on the antiatoms.”
The second CERN antimatter gravity experiment is GBAR and takes a wholly different and unique approach. It will be making antihydrogen ions (one antiproton and two positrons technically) by using the ELENA deceleration ring’s antiprotons and positrons that will be supplied by a linear decelerator. Once the antihydrogen ions have been trapped and cooled down significantly to 10 microkelvin, laser light will be utilized to take away one positron, which will, in effect, change them into neutral antiatoms.
Once this has been completed, the natural antiatoms will be set free from their trap and dropped 20 centimeters down, so that scientists can observe how they behave. After all of the work involved with GBAR and ALPHA-g, CERN has just announced that the first beams of anitprotons have now officially been received by the new experiments, and time is of the essence here as the accelerators at CERN will soon be shut down for important maintenance work that will be conducted over the next two years.
“We are hoping that we’ll get the chance to make the first gravity measurements with antimatter, but it’s a race against time,” ALPHA Spokesman Jeffrey Hangst notes.
Meanwhile, GBAR’s Patrice Pérez explained that while antimatter gravity work is currently being done now, work will continue at CERN again in earnest in 2021, when gravitational effects will be measured.
“The GBAR experiment is using an entirely new apparatus and an antiproton beam still in its commissioning phase. We hope to produce antihydrogen this year and are working towards being ready to measure the gravitational effects on antimatter when the antiprotons are back in 2021.”
According to CERN, the two antimatter gravity experiments are especially important as if there does turn out to be a difference in how matter and antimatter respond to gravity, this could help to explain why the universe contains so much matter instead of antimatter.