What weighs more : a kilogram of feathering or a kilo of lead?This sure-enough jokeis really no gag to physicists – since the time of Galileo , they have been trying to demonstrate that object in a gravitational force field experience the same acceleration . This is the universality of complimentary fall , and it has now proven to be right to less than one part per 1,000 trillion .

As reported in papers in Physical Review Letters and a special issue of Classical and Quantum Gravity , research worker used a limited satellite to precisely test the so - called Weak Equivalence Principle , a cornerstone of Einstein ’s general theory of relativity . In a gravitative field , with no other effect acting upon them , two target made of different stuff and with different masses are expected to be subjected to the same acceleration .

To examine this , scientist built theMICROSCOPE orbiter . In it , they placed two homocentric cylindrical test masses : one atomic number 22 and one atomic number 78 - rhodium admixture . These masses were kept motionless and supervise by static accelerometer . A violation of the equivalence rule will see the two masses have dissimilar accelerations .

Galileo is say to have certify that by dropping cannon ball of dissimilar masses from the Leaning Tower of Pisa . Apollo 15 commander David Scott did it witha plume and a hammeron the Moon . This experiment bring that intellect to a preciseness of one part in 1015 .

“ We have new and much better constraints for any future theory , because these theories must not spoil the comparability principle at this level , ” Gilles Métris , a scientist at Côte d’Azur Observatory and appendage of the MICROSCOPE team , say in astatement .

The latest data is 10 times better than theinitial results published in 2017and 100 times better than what can be done on Earth . The squad propose that there are way to push the precision even further with a new satellite , maybe make it 100 prison term more precise .

“ For at least one decade or perchance two , we do n’t see any improvement with a space satellite experiment , ” add Manuel Rodrigues , a scientist at the Gallic aerospace lab ONERA and member of the MICROSCOPE squad .

Testing the Weak Equivalence Principle is not just a way for scientists to prove that Einstein was wrong . General Relativity is our best theory of sobriety so far , but it does n’t turn well with quantum mechanics . investigate soberness at the highest precision might give us insight into how to resign the two .