Ask A Scientist© Astronomy Archive

Question: Why is it so hard to quantify gravity?
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It is not.  Gravity can be measured by producing a local 
acceleration which cancels it out.  Gravity is exactly detectable as a local 
acceleration and can be precisely measured.  The biggest problem with gravity 
is that it enters into the equations of motion for a particle as a part of 
space and time.  This means that we have to find out the structure of space 
from the distribution of masses and then find the motion in that warped space.  
This is difficult.  Another aspect of gravity is that it is very weak.  The 
excitations of gravity, the gravitons are expected to exist, but are so weak 
that no one can seem to measure them.  Many have tried for several years.
Sam Bowen
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