The Information of Gravity

The theory of quantum physics is the basis of our modern world. Personal computers, Kindles, cellphones, GPS units, iPods, iPads and all the other toys we enjoy today owe their existence to quantum physics.

And we’re not done yet.

Essentially, the theory states all existence is information. You, me, the world, the Universe is all information of various types.

Now, gravity gets the treatment:

One of the hottest new ideas in physics is that gravity is an emergent phenomena; that it somehow arises from the complex interaction of simpler things.

A few month’s ago, Erik Verlinde at the the University of Amsterdam put forward one such idea which has taken the world of physics by storm. Verlinde suggested that gravity is merely a manifestation of entropy in the Universe. His idea is based on the second law of thermodynamics, that entropy always increases over time. It suggests that differences in entropy between parts of the Universe generates a force that redistributes matter in a way that maximises entropy. This is the force we call gravity.

What’s exciting about the approach is that it dramatically simplifies the theoretical scaffolding that supports modern physics. And while it has its limitations–for example, it generates Newton’s laws of gravity rather than Einstein’s–it has some advantages too, such as the ability to account for the magnitude of dark energy which conventional theories of gravity struggle with.

But perhaps the most powerful idea to emerge from Verlinde’s approach is that gravity is essentially a phenomenon of information.

Today, this idea gets a useful boost from Jae-Weon Lee at Jungwon University in South Korea and a couple of buddies. They use the idea of quantum information to derive a theory of gravity and they do it taking a slightly different tack to Verlinde.

At the heart of their idea is the tricky question of what happens to information when it enters a black hole. Physicists have puzzled over this for decades with little consensus. But one thing they agree on is Landauer’s principle: that erasing a bit of quantum information always increases the entropy of the Universe by a certain small amount and requires a specific amount of energy.

Jae-Weon and co assume that this erasure process must occur at the black hole horizon. And if so, spacetime must organise itself in a way that maximises entropy at these horizons. In other words, it generates a gravity-like force.

That’s intriguing for several reasons. First, Jae-Weon and co assume the existence of spacetime and its geometry and simply ask what form it must take if information is being erased at horizons in this way.

It also relates gravity to quantum information for the first time. Over recent years many results in quantum mechanics have pointed to the increasingly important role that information appears to play in the Universe.

Some physicists are convinced that the properties of information do not come from the behaviour of information carriers such as photons and electrons but the other way round. They think that information itself is the ghostly bedrock on which our universe is built.

Gravity has always been a fly in this ointment. But the growing realisation that information plays a fundamental role here too, could open the way to the kind of unification between the quantum mechanics and relativity that physicists have dreamed of.

arXiv article:

Technology Review post

hat tip


8 responses

  1. that paper was so nice!

    1. The LHC was supposed to start colliding particle beams today Bruce, did they?

  2. yeah, they did. Geneva, 30 March 2010.
    Beams collided at 7 TeV in
    the LHC at 13:06 CEST,
    marking the start of the
    LHC research
    programme. Particle
    physicists around the
    world are looking forward
    to a potentially rich
    harvest of new physics as
    the LHC begins its first
    long run at an energy
    three and a half times
    higher than previously
    achieved at a particle

    1. I wonder what kind of new particles the collision made?

      Nothing very spectacular so far I bet, we’re still here and the Earth isn’t destroyed! 😆

  3. Who said Earth would be destroyed? that was only pathetic falsefront portrayed by some stupids. read my post myth of strange matter,black hole at LHC. it’s debunking that falsefront. 😉

    1. I was only being funny Bruce, I don’t really believe that stuff.

      But I am curious about new particles…

    1. When the scientists at CERN go through the debris left by the LHC particle collisions I wonder if they’ll find that graviton particle they’ve been searching for?

      I’ll be keeping an eye out for that rumor!

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