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Basically what he’s saying is that gravity is a macroscopic effect of microscopic particle interaction, in the same way as temperature is a macroscopic average of particle collisions.
In both cases temperature and gravity don’t exist as individual forces… X-|
Carter Emmart is the astronomer giving the lecture in the TED|VID above.
If you want to know why you shoud listen to his ideas then read:
The recently launched Kepler space telescope is starting to pay off big time.
Over 700 exo-planet candidates has been found so far and although only 7 has been confirmed so far (as actual existing exo-planets) the statistics are staggering.
When you compare the number of exo-planet candidates with the number of stars that has been searched by Kepler and the total number of stars in the Milky Way you find that:
1) Earth like planerts (in size and mass) seems to be the most common planet type.
2) The Milky Way properly contains about 100 MILLION!!! of these exo-planets in habitable orbits.
Need I say more? 
Please check out this awesome TED Talk where Dimitar Sasselov explains the hole deal in far greater detail.