Search FQXi


Lorraine Ford: "Eckard, -------- P.S. to my previous post: So what is creativity?..." in Your Invitation to FQXi's...

Eckard Blumschein: "Pentcho, "light is always propagated in empty space with a definite..." in Ripping Apart Einstein

Georgina Parry: "Peter , thanks. Time reversal signal processing is transmitting the..." in Your Invitation to FQXi's...

Jason Wolfe: "Hi Peter, I remember one time I tried to explain how an inertial reference..." in The Quantum Pet Store:...

Thomas Ray: "" ... Einstein should have concluded: Since the consequent (either clock..." in Ripping Apart Einstein

Akinbo Ojo: "Peter, let me further simplify and clarify the scenario as you suggested..." in Faster than Light

John Merryman: "Vladimir, Mostly this is my synthesis of all the stuff I've learned over..." in Why Quantum?

Peter Jackson: "Akinbo; 1) A set up (Observer-Source-Observer) fixed in your office..." in Faster than Light

click titles to read articles

Quantifying Occam
Is the simplest answer always the best? Connecting Medieval monks to computational complexity, using the branch of mathematics known as category theory.

Heart of Darkness
An intrepid physicist attempts to climb into the core of black hole.

Why Quantum?
Entropy could explain why nature chose to play by quantum rules.

Reality's NeverEnding Story
A quantum version of Darwinian natural selection could enable the universe to write itself into being.

The Quantum Dictionary
Mark Van Raamsdonk is re-writing how we define the shape of our universe. Can such translations help to unite quantum theory and gravity?

September 18, 2014

The Myth of Gravity
A new model in which gravity is not a fundamental force could—counterintuitively—give a controversial quantum gravity theory a boost. It may also change our picture of spacetime, and do away with dark energy.
by Sophie Hebden
April 24, 2010
Bookmark and Share

Erik Verlinde
University of Amsterdam
When thieves stole Erik Verlinde’s laptop and keys, while he was holidaying in the south of France, they could have had little notion that their crime would lead to a new model for gravity. But forced into taking an extra week’s vacation time, Verlinde began to ponder whether gravity might not be a fundamental force of nature, arising instead from thermodynamics. His ideas could give the controversial loop quantum gravity theory—in which spacetime is made up of quantum threads—a boost, and help explain the accelerated expansion of the universe.

Gravity may be the force that we are most familiar with in everyday life, but physicists do not yet understand its origin. Newton told us that apples fall towards Earth with an acceleration that depends on the Earth’s mass, the apple’s mass, and its distance from the centre of the Earth, while Einstein described gravity by the warping of the fabric of spacetime. But while these theories describe how gravity works, they don’t explain how it arises.

Verlinde, a string theorist at the University of Amsterdam in the Netherlands, believes that the key to understanding gravity is "information." He was inspired by early work on information storage in black holes by Stephen Hawking and Nobel laureate Gerard ’t Hooft. "When I was about fifteen I saw them on television talking about the physics of elementary particles and black holes," says Verlinde. "I knew then that I wanted to work in that area."

The Television Event Horizon

Hawking and ’t Hooft had both worked on the so-called holographic principle, which relates the information content—or entropy—of a black hole to the surface area of its event horizon, the hypothetical sphere around the black hole where gravity becomes so strong even light can’t escape. It’s as if the horizon is a spherical television screen with all the information about the three-dimensional volume within encoded on the pixels on its surface. Verlinde has shown that by combining the holographic principle with the thermodynamic quantities of heat and mechanical work, it’s relatively straightforward to derive Newton’s classical equation of gravity. (See "Decoding Entropic Gravity" for more details.)

Entropic force?
Imagining a particle near a spherical holographic screen
allows you to derive Newton’s law of gravity.
The work has been causing a stir amongst physicists. "Verlinde’s paper is remarkable in that we all felt so stupid for not having seen it before," says FQXi’s Lee Smolin of the Perimeter Institute, Ontario. "The mathematics involved is just high school algebra."

It might sound like re-inventing the wheel, but the approach implies that gravity is nothing more than the result of a system maximising its entropy, or disorder. At first glance, this looks like bad news for the quantum gravity crowd. If gravity is an "entropic force," there is no longer a need for physicists to attempt to reconcile general relativity with quantum mechanics, or hunt for the hypothetical graviton (the particle posited to carry the gravitational force just as photons mediate the electromagnetic force), says Paul Frampton, at the University of Tokyo in Japan. Rather, all we need to explain the interactions of particles is the Standard Model of particle physics and entropy. "It means that everyone looking into quantum gravity is misguided," says Frampton.

Quantum Threads

However, not all gravity researchers take that view. Smolin, a long term proponent of loop quantum gravity (LQG), believes that Verlinde’s work is not only compatible with LQG, it could even help to explain how familiar Newtonian gravity might emerge in this picture. According to LQG, spacetime isn’t the smooth fabric that Einstein envisioned; rather, if you zoom down to scales of 10-33 cm, the fabric turns out to be woven from quantum threads. The key point for Smolin is that the holographic principle is also valid in this framework, allowing him to apply a version of Verlinde’s argument to demonstrate directly for the first time that loop quantum gravity has a limit that yields Newtonian gravity.

Smolin notes that Verlinde’s model is tied to earlier work by FQXi member Ted Jacobson, who had shown in 1995 that Einstein’s equations of general relativity could be derived using thermodynamics and the holographic principle. "The wonderful thing about the arguments of Jacobson and Verlinde is they give a deep reason for why a quantum theory of gravity should yield the phenomena of gravitation," Smolin writes in his recent paper (arXiv:1001.3668v2).

There isn’t a fundamental
gravitational interaction.
Is that crazy enough?
- Paul Frampton
Frampton and colleagues Damien Easson and Nobel Laureate George Smoot have been looking at possible observable consequences of Verlinde’s entropic force. So far, cosmologists have struggled to explain why the expansion of the universe is accelerating using just standard general relativity. Instead, they attribute the acceleration to some mysterious "dark energy." To find a possible alternative to dark energy, Smoot’s team considered a spherical screen that lies on the apparent horizon of the universe, where distant objects recede at the speed of light. As information is sucked out across the horizon, the area of the screen grows, which, according to the holographic principle, increases the entropy of the universe. This gives rise to an entropic force that could explain the acceleration, "derived as a response to various microscopic fundamental forces such as electromagnetism," says Easson, at Arizona State University, Tempe. However, Easson adds that the work is "extremely speculative" at this stage (arXiv:1002.4278v2).

If such derivations of dark energy stand up then Verlinde’s ideas "could in some sense complete general relativity," says physicist Sabine Hossenfelder at the Nordic Institute of Theoretical Physics in Sweden. However, there is still a long way to go before physicists will abandon the notion that gravity is a real force as there are several things that remain vague in Verlinde’s formulation, she adds.

Frampton, however, is convinced that Verlinde is on the right track. "I believe that gravity is entirely explained by increases in entropy; there isn’t a fundamental gravitational interaction," he says. "That’s the bottom line. Is that crazy enough?"

Comment on this Article

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!
  • Please enter the text of your post, then click the "Submit New Post" button below. You may also optionally add file attachments below before submitting your edits.

  • HTML tags are not permitted in posts, and will automatically be stripped out. Links to other web sites are permitted. For instructions on how to add links, please read the link help page.

  • You may use superscript (10100) and subscript (A2) using [sup]...[/sup] and [sub]...[/sub] tags.

  • You may use bold (important) and italics (emphasize) using [b]...[/b] and [i]...[/i] tags.

  • You may also include LateX equations into your post.

Insert LaTeX Equation [hide]

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation
clear equation
insert equation into post at cursor

Your name: (optional)

Important: In order to combat spam, please select the letter in this menu between 'L' and 'N':

Recent Comments

The Nature of Spatial Content:

As a result of experiment and observation we are predisposed to thinking that nature abhors a vacuum, vacuum being unfilled void or space. By nature we mean the totality of all phenomena that exhibit behaviour. Vacuum, which we consider to be devoid of behaviour, we conclude to be hostile and unnatural. We take this position because our immediate environment is almost totally natural. It teems with phenomena exhibiting behaviour. But if we take the larger,...

The gravity is dependent on the mass and the ultimate source of the mass is the electromagnetic force. The only attracting force between same electric charges is the magnetic force if they are moving in the same direction. Probably the Big Bang caused accelerating Universe gives this parallel motion and the general magnetic attraction - we intercepting as gravitation.

Hello Erik,

Simply Congratulations on your out of the box work...

The arena you have chosen to explore with you open approach to ideas and intuition, along with the science of our finite truth through mathematics, bodes well for the future of knowledge. Which needs new ideas to move us forward to a more universal community of cultures, through science.

Cheers, and good journey to you,


read all article comments

Please enter your e-mail address:
Note: Joining the FQXi mailing list does not give you a login account or constitute membership in the organization.