Spiralling under Control

An apple falls from a tree -but would an antimatter apple fall in exactly the same way?The gravitational interaction between matter and antimatter is still insufficiently understood, but so far evidence suggests that the gravitational mass of matter is the same as that of antimatter.To test this further, the ALPHA collaboration at CERN has developed a way of measuring anti-hydrogen atoms in free fall.Anti-hydrogen atoms are produced by mixing antiprotons (supplied by CERN's Antiproton Decelerator) and positrons in a Penning trap.The anti-atoms are trapped in the three-dimensional potential minimum created by additional magnetic fields.When these fields are switched off, the anti-atoms are released, but their escape is short-lived as