## What is momentum?

Momentum is a central concept in both classical and modern physics. It tells us something about the force that a massive body–or massless particle–exerts in a collision. But how are the classical and quantum formulas related? What exactly is momentum? A textbook description of momentum merely characterizes the classical formula . The formula gives a … Read more

## Here’s why the fundamental constants are not fundamental

Planck’s constant and the gravitational constant are considered fundamental constants of nature. Both are instrumental in calculating physical quantities, but what makes them fundamental? Are they truly irreducible quantities from first principles, or just misunderstood? A close examination of the constants shows why they are not fundamental, but made from fundamental units. Reason #1: The … Read more

## Why is gravity so weak?

One of the pressing questions in modern physics is why gravity seems so much weaker than the other forces. Compared to the electromagnetic force, the gravity we experience is 40 orders of magnitude weaker. Should we even expect these forces to be comparable? It turns out that we should. The maximum force potential of gravity … Read more

## What is the physical meaning of Einstein’s famous equation 𝐸=𝑚𝑐²?

Einstein’s iconic equation 𝐸=𝑚𝑐² is perhaps the most recognized equation of all time. It is famously simple and profound. Ask anyone familiar with the formula and they’ll probably tell you that mass and energy are two different forms of the same thing. They might even tell you that the conversion rate between them is the … Read more

## What is Planck’s constant?

Planck’s constant is the famous constant of proportionality discovered by Max Planck at the end of the 19th century. The constant is instrumental in calculating physical quantities on tiny scales including the properties of elementary particles. Calculating a particle’s wavelength, momentum, and energy is simple. Multiply Planck’s constant by the right inputs and out comes … Read more

## What is the gravitational constant?

The gravitational constant is a number. What sets it apart from other numbers is that you can multiply the gravitational constant by the mass and radius of a large body to find the strength of its gravitational field. Calculating acceleration, force, energy, and other gravitational potentials is simple. Just multiply the constant by the right … Read more