SCIENCE: An orbiting ‘Microscope’ is about to discover if Einstein was right.

According to Einstein’s theories, two objects in perfect free fall should move in exactly the same way. There’s only one place where you can keep something in permanent free fall, and that’s orbit.

So scientists loaded two different pieces of metal – one titanium and the other a platinum-rhodium alloy – into a satellite called Microscope and sent it into orbit on a Russian Soyuz rocket from Arianespace’s launch pad in French Guiana over the weekend.

“In space, it is possible to study the relative motion of two bodies in almost perfect and permanent free fall aboard an orbiting satellite, shielded from perturbations encountered on Earth,” said Arianespace.

If the two objects move identically then Einstein was right and we can chalk up another victory for humanity. Nice. If they behave differently, however, then that’ll be even more exciting – it’ll “shake the foundations of physics”, according to France’s CNES space agency, which financed 90% of the project.

What’s also remarkable is that a French-built satellite is traveling onboard a Russian rocket launched from a South American facility to test a century-old theory of a German-born Jewish physicist.