There are few things we take more for granted than the concept of gravity. Through history, physicists like Isaac Newton and Albert Einstein have developed theories about the Universe that depended on the idea that objects large and small are naturally attracted to one another in space—keeping our feet firmly planted on the Earth and keeping planets in orbit around the Sun.
But Dutch theoretical physicist Erik Verlinde thinks that gravity isn't a fundamental force of nature. Rather, what we call gravity, he says, is instead the aggregated effects of other microscopic phenomena that we don't yet have a firm understanding of.
In a paper published in December 2009 on arXiv.org, Verlinde laid out his argument that gravity is not a "fundamental force," and is instead an "emergent phenomenon" like thermodynamics or hydrodynamics. "The results of this paper suggest gravity arises as an entropic force, once space and time themselves have emerged," wrote Verlinde in his paper. "If the gravity and space time can indeed be explained as emergent phenomena, this should have important implications for many areas in which gravity plays a central role."
Verlinde explains this further to Big Think, saying: "The equations that we currently use to describe gravity are basically obtained from averaging, or at least describing things at a much tinier scale and then forgetting about certain details." He says when you start applying Einstein's theories of gravity to things like black holes and dark matter, the attraction appears to resemble an effect rather than a force.
What will this change in the conception of gravity this mean for our everyday lives? Not much, admits Verlinde. But he thinks his theory could lead physicists to a better understanding of the Big Bang and a more refined way of thinking about the early Universe.
Why We Should Reject This
Verlinde admits that there are a number of big unanswered questions that could potentially undermine his ideas. Chiefly among them is how this concept of gravity is able to fit with existing theories of quantum mechanics.
"In quantum mechanics ... you think about particles as waves," says Verlinde. "They can add up and subtract and you get sort of patterns of waves doing all kinds of weird things, and this can also happen to particles. If entropy would play a role in gravity, then you might wonder whether this interference that happens in gravity, in quantum mechanics would still hold and would still be true."
Sean Carroll, a physicist at the California Institute of Technology told Big Think that Verlinde's approach to entropic gravity is "a very provocative idea," but says it's unclear where it will lead. "This is one of those big-picture ideas that might turn out to be the foundation of everything, or might just evaporate in the wind—it's too early to tell," Carroll said.
"The basic notion that gravity is emergent is a very robust one," says Carroll. "The question is, emergent from what? Verlinde has highlighted an intriguing connection between gravity and entropy, but we're not yet sure what the deep-down constituents are whose entropy we're actually talking about."
— "On the Origin of Gravity and the Laws of Newton." Paper submitted by Verlinde to arXiv.org in January, 2010, putting forth the idea that gravity does not exist.
— Erik Verlinde's faculty page from the University of Amsterdam.