## Merry Newtonmass!

Today, we celebrate the birth of a man who has impacted the history of the world to a degree which few can match. I speak of course of Sir Isaac Newton, the father of physics.

He was born on December 25, 1642 (under the old Julian calendar). His groundbreaking work forever changed the way we learn about and understand reality. With his invention of the Calculus, he provided the mathematical framework for modelling reality. His study of motion (built upon the work of Galileo and Kepler) overturned two millennia of Aristotle’s deeply flawed and misguided version of physics. His study of light foreshadowed the birth of quantum mechanics. (He correctly realized that light is corpuscular in nature, although his reasoning for that conclusion was flawed.)

He was also knee-deep in the superstitious nonsense of alchemy and engaged in a protracted feud with Leibniz over credit for the invention of the Calculus, but nobody is perfect. (Technically, Newton came up with the Calculus first, by several decades, as shown by the contents of his notebooks, but he made the mistake of holding off on publishing his work.)

In celebration of the life of this great man, I first happily note that the University of Cambridge is making a digitized collection of Newton’s papers available online. Weeee!

Over the days leading up to the anniversary of Sir Isaac’s birth, Chad Orzel over at the “Uncertain Principles” blog has been posting a series of articles entitled “The Advent Calendar of Physics,” with each entry celebrating an important equation in the historical development of physics, starting of course with Newton’s contributions.  They are worth a look-see:

## Force and Momentum

Dec. 1,  a look at the basic definition of force and momentum, Newton’s 2nd Law: $\displaystyle\frac{\mathrm{d}\vec{p}}{\mathrm{d}t}=\vec{F}_{net}$

## Action and Reaction

Dec. 2, Newton’s 3rd Law: $\displaystyle\vec{F}_{12}=-\vec{F}_{21}$

## Newton and Einstein

Dec. 3, the relativistic definition of momentum: $\displaystyle\vec{p} = \gamma m\vec{v}=\frac{1}{\sqrt{1-\frac{\vec{v}^2}{c^2}}}m\vec{v}$

## The Spring’s the Thing

Dec. 4, Hooke’s Law: $\displaystyle\vec{F}_{spring}=-k_ss\hat{L}$

## Introducing Energy

Dec. 5, the relativistic definition of energy: $\displaystyle E_{particle}=\gamma mc^2 = \frac{mc^2}{\sqrt{1-v^2/c^2}}$

## Using Energy

Dec.6, the Energy Principle: $\displaystyle\Delta E_{sys} = W_{surr} + Q$ (complete with obligatory mention of Noether’s Theorem)

## Working for a Living

Dec. 7, the definition of work: $\displaystyle W_F=\int_{r_i}^{r_f}{\vec{F}\cdot \mathrm{d}\vec{r}}$

## Introducing Angular Momentum

Dec. 8, the definition of angular momentum: $\displaystyle\vec{L}_A=\vec{r}_A\times\vec{p}$

## Using Angular Momentum

Dec. 9, the Angular Momentum Principle: $\displaystyle\frac{\mathrm{d}\vec{L}_A}{\mathrm{d}t}=\vec{\tau}_{net,ext,A}$

## Torque

Dec. 10, the definition of torque: $\displaystyle\vec{\tau}_A = \vec{r}_A \times \vec{F}_A$

## Newton’s Gravity

Dec. 11 (posted on the 12th), Newton’s Law of Universal Gravitation: $\displaystyle\vec{F}_{grav,on2by1}=-G\frac{m_1 m_2}{\|\vec{r}\|^2}\hat{r}$

## E and B

Dec. 12, moving on to E&M, we are introduced to the Lorentz force law: $\displaystyle\vec{F}=q\vec{E} + q\vec{v} \times \vec{B}$

## Gauss and Maxwell

Dec. 13, Gauss’ Law: $\displaystyle\nabla\cdot\vec{E}=\frac{\rho}{\epsilon_0}$

## Monopole!

Dec. 14, Gauss’ Law for magnetic fields: $\displaystyle\nabla\cdot\vec{B}=0$

Dec. 15, Faraday’s Law: $\displaystyle\nabla \times \vec{E} = -\frac{\mathrm{d}\vec{B}}{\mathrm{d}t}$

## Ampère and Maxwell

Dec. 16, Ampère’s Law: $\displaystyle\nabla \times \vec{B} = \mu_0 J - \mu_0\epsilon_0\frac{\mathrm{d}\vec{E}}{\mathrm{d}t}$

## Ideal Gas

Dec. 17, diving into statistical mechanics and thermodynamics, the Ideal Gas Law: $\displaystyle PV=Nk_BT$

## Entropy

Dec. 18, Boltzmann’s definition of entropy: $\displaystyle S=k_B \log{N}$

## Science Works

Dec. 19, Max Planck’s formula for the black-body radiation spectrum: $\displaystyle I(\nu)=\left(\frac{8\pi h\nu^3}{c^3}\right)\frac{1}{e^{\frac{h\nu}{k_B T}}-1}$, marking the birth of quantum mechanics.

## Einstein’s Nobel

Dec. 20, a look at Einstein’s work, building on the work of Planck, on the photoelectric effect, for which he was awarded the Nobel prize: $\displaystyle E_{\gamma}=h\nu=\frac{hc}{\lambda}$

## Hydrogen

Dec. 21, the Rydberg formula for the spectral lines of hydrogen: $\displaystyle \frac{1}{\lambda}=R_H\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)$

## Schrödinger

Dec. 22, the Schrödinger equation: $\displaystyle \hat{H}|\Psi\rangle = i\hbar\frac{\partial}{\partial t}|\Psi\rangle$ (or, as Orzel puts it, “the most fruitful booty call in the history of science.”)

## Einstein’s Gravity

Dec. 23, the Einstein field equation from General Relativity, which describes the deformation of space-time by the presence of mass and energy: $\displaystyle R_{\mu\nu}-\frac{1}{2}Rg_{\mu\nu}=8\pi GT_{\mu\nu}$

## Eponym

Dec. 24, Orzel wraps up the Advent Calendar of Physics with the Heisenberg Uncertainty Principle: $\displaystyle \Delta x \Delta p \ge \frac{\hbar}{2}$

Update: Feb. 14, 2012
Here is a physics advent calendar from 2007: A Plottl a Day