Celebrating 100 years of Feynman

Yay! Feynman turns hundred. For the record, I love Richard P. Feynman. He is the perfect human specimen and one of my favorite scientists.


I read Surely You’re Joking, Mr. Feynman and The Pleasure of Finding Things Out a few years back. I started reading his lectures recently, but after a while, some things did not make sense to me and so I thought that rather than developing wrong conceptions, I’ll read them when I have a better understanding of things and the book ain’t going anywhere because it is paper. Your Kindle mobis are always threatened, just so you know. You can always lose them. But the bark of a tree is forever (unless it decomposes, but don’t worry. You won’t live that long). #PhysicalBookSuperiority

Anyway, I was just learning about Feynman’s diagrams and I wanted to share two interesting things I liked:

1. The off-shell particles

When two particles interact there are three events in a broad sense: The incoming of particles, the outgoing of particles and everything in between. These particles that we are observing are called on-shell particles. Within the interacting, new particles are created, destroyed, energy, momentum and other quantities are exchanged. The particles that are present during this interaction phase are called off-shell particles. Now, what is interesting is that these particles do not follow the laws we believe are true. They do not follow conservation of energy or momentum. They can move at higher speeds than the speed of light and they do not follow any concept of “time”. I wonder if we ever manipulate these particles better, what implications and applications will they have. Fascinating.

 2. Antimatter’s sense of time

The Feynman Diagrams are drawn using time as an axis. A “matter” particle, such as an electron is shown having a movement which goes with increasing time i.e. it goes from the past to the future. But an “antimatter” particles, such as a positron is depicted in the opposite way i.e. it follows a reversed arrow of time. This does make sense.

This example is not correct, but still pretty intuitive to prove a point:

Current is I= q/t (q is the charge, t is time; let’s forget about the dq/dt for simplicity)

For an electron let’s suppose that the charge is -q. We take time to be positive t because the electron goes from 1918 to 2018 and not the other way round.

For a particle that goes from 21018 to 1918, time will be -t. In this case, this particle is a positron.

Now for the electron and the positron to have the same current, the positron should have -q charge to cancel the negative in its time variable. This is precisely what the charge of the positron is!

So, time reversal is a thing.

Bad Science Joke: God said “Let opposite times smash” and there was light.



My favorite quote of all time.


Live long RPF’s works. What a man, what a life.

“Thank you very much. I enjoyed myself.”


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