The weak equivalence principle (WEP) - which states that all bodies fall at the same rate in a gravitational field, regardless of structure or composition - is one of the key postulates of general relativity. Tests have shown that the WEP is accurate to within one part in 10 trillion, or an uncertainty of 10-13 of the acceleration of gravity. However, a violation of the WEP is suggested by most theories that attempt to unify gravity with the other forces, which is one of the biggest challenges in physics today. Looking for new ways to test the WEP to even greater accuracy and perhaps detect a violation, astrophysicists at the Harvard-Smithsonian Center for Astrophysics have designed a new WEP test to be conducted during free fall in a rocket flight.
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