Gravity Can Push Away — A Quantum Experiment ✎ express
Gravity always pulls — an apple falls down, planets orbit in circles. But by placing a source of gravity in two places at once, you can get the opposite. Physicists have proposed an experiment: a massive body is put into a quantum state, smeared across space like a cloud. Then a tiny particle is shot into that cloud.
In classical physics, the particle would be attracted to each position of the mass and travel along an average path. But after a special selection of the measurement outcomes of the source, two versions of gravity interfere.
Unlike gravitational waves, this phenomenon requires a quantum description. Ideas of quantum gravity, which call for a revision of the foundations of physics, were developed by scientists such as John Archibald Wheeler, Roger Penrose, and Stephen Hawking.
The big surprise: repulsion occurs only in half the cases when you select the right outcome. And the source mass must be smaller than a grain of sand, but huge by the microworld's standards. Such an experiment is feasible right now and will for the first time let us 'feel' the quantum nature of spacetime.
Quantum gravity was considered almost elusive: the forces are so weak that at the micro level they can't be measured. This experiment proves otherwise.
Science fiction writers have long dreamed of antigravity: Asimov created it with quantum converters. Now scientists propose a real quantum trick to see repulsion in the lab for the first time.