Erik Peter Verlinde

Dutch Theoretical Physicist in his way to be the next European Newton. Like all European physicists, he is aware of the strong contribution in that continent to our field. He is more than ten years younger than me, thus I started to follow his work when I had been doing theoretical physics for some time. Due to some mental ailment I don't understand, few people know about me; therefore I know more people than people know me.

I know his work.

I was expecting good things from him. He seems to have finally done it. I write here my understanding of his 2009 accomplishment, just when my friend Alex Filippenko was explaining to high school kids here in Guerrero, and Astronomy graduate students at UNAM in Mexico City, the discovery of Dark Energy, that now Erik can start to explain.

It all starts with Thermodynamics, maybe it was not an accident that he comes from Holland: There Einstein's dear friend, Paul Ehrenfest, proved that Quantum Mechanics was consistent with Classical Mechanics, and contributed to Thermodynamics. I met two other great physicists, Prof. George Uhlenbeck , and Prof. Abraham Pais. They worked in Holland during their careers.

At CINVESTAV they expected us to guide distinguished scientists through town. I was honored to take Prof. Pais around Mexico City. I met his son, he was just a boy, and I was happy to take them around. I practiced my English skills besides.

Prof. Uhlenbeck taught us Statistical Mechanics at a Summer School at CINVESTAV. He said that there was no knowledge frontier. There was no boundary line, on the one side all that there is to discover, on the other all that we already know. He said it was more like an archipelago: Known islands, and unkown islands; all scrambled up; as a fractal boundary we will say now.

Ehrenfest committed suicide, obviously he had mental problems as the ones I write about in some of my last posts in this blog. He couldn't bear his son mental problems, he killed the son Vassily, and then killed himself; like his mentor Ludwig Boltzmann before him.

Uhlenbeck had been Ehrenfest's student, and taught us with commitment. I still remember his beautiful lectures. One day, during that summer, Prof. Marcos Moshinsky, from the "other" Theoretical Physics school in the south of Mexico City at UNAM came to our school in the north. Prof. Uhlenbeck just told all of us to go out to the beautiful garden outside the Physics Department. We sat on the grass with Profs. Moshinski and Uhlenbeck. What a treat!

It does not surprise me that the next giant step in our field was taken in Amsterdam. Where else?

Verlinde took the Thermodynamics insights of Jacob Bekenstein.

I follow Bekenstein's work because he was born in Mexico, even though I have never met him personally, and because his work is fundamental. I was introduced to this work by Terry Sejnowski at UCSB. He told us about the Second Law of Black Hole Thermodynamics, when he was a postdoc in Jim Hartle's group there. Terry even organized a seminar where I met Vinod Jhangiani; the Vinod of my short story.

Verlinde also took Gerardus 't Hooft work. The so-called Holographic Principle: everything on one side of a boundary is coded on the boundary, and an observer on the other side of the boundary sees a statistical representation of it. In Quantum Gravity then, we have a Statistical macroscopic field, as seen from our side of that boundary. Gravity then, is an emergent statistical average, just like temperature, and pressure, in the mechanical theory of heat, developed by Boltzmann; who thus found the concept of Information before any human being. Entropy is the probability of a mechanical state. Later Claude Shannon called it Information.

Now Verlinde tells us that Gravity is statistical, just like Entropy and Temperature, i.e. emergent. Actually Jim Hartle had already told us this much at UCSB. He invited Stephen Hawking there, when he discovered that black holes have temperature. I went to Hawking's talk, he still could talk with his own vocal chords, it was hard to understand him, but it was still possible. We were just a few in a small room as I remember the lecture. He gave us a nice preprint after the talk, with his black hole radiation theory clearly explained.

Verlinde derived Newton's Law of Universal Gravitation mixing together the ideas presented here, and some I don't understand here.

I want to bring the memory of a dear person I hardly knew. Prof. Jerzy Plebanski. Unfortunately I left CINVESTAV, when he came back from Poland, and I went to UCSB. Neverhteless now Lee Smolin has connected the beautiful work of Verlinde with that of Plebanski here.

Finally I want to bring the contribution of my friend Alex Filippenko, whose contribution I have tried to explain in this blog.

I was fortunate to have met him at UCSB, when he was an undergraduate student in the College of Creative Studies, and that he graciously accepted to come to Guerrero as part of the International Year of Astronomy's activities last year.

Alex's colleagues discovered that the Universe has been accelerating since five thousand million years ago, when the dark energy overcame the gravitational attraction; and now Erik can tell us, how to go about calculating how big is the coupling of this majority material with the rest of the Universe.

What a year 2009 was!