What is quantum physics? Put simply, it’s the physics that explains how everything works: the best description we have of the nature of the particles that make up matter and the forces with which they interact Quantum physics underlies how atoms work, and so why chemistry and biology work as they do

Schrödinger was moved by the Upanishads He discussed it with everyone he met and made determined efforts to incorporate it in his life The epitaph on his tombstone reads, “… So all Being is an one and only Being; And that it continues to be when someone dies; [this] tells you, that he did not cease to be”

In 1935 physicist Erwin Schrödinger devised his famous thought experiment involving a cat that could, surprisingly, be both dead and alive at the same time Mathematically, the feline is in an entangled superposition of quantum states – known as the “Schrödinger-cat” state

Although sound travels as a wave, the individual particles of the medium do not travel with the wave, but only vibrate back and forth centered on a spot called its equilibrium position, as shown below Sound is a longitudinal wave

Light is Quantized It isn’t light as a particle However, light is still pretty weird There is a quantum nature to the electric and magnetic fields in light (quantum theory of radiation) But most of the stuff you look at can be explained using a classical wave model of light and a quantized model for matter

Light behaves mainly like a wave but it can also be considered to consist of tiny packages of energy called photons Photons carry a fixed amount of energy but have no mass They also found that increasing the intensity of light increased the number of electrons ejected, but not their speed

Because photons are discrete particles, they have a certain amount of energy, but not a wavelength because they are not waves Before that, Isaac Newton had claimed that light was really a stream of particles, but he did not have much evidence Young made a clear case by demonstrating that light interferes with itself

Visible light is carried by photons, and so are all the other kinds of electromagnetic radiation like X-rays, microwaves and radio waves In other words, light is a particle

The speed of light in a vacuum is miles per second (kilometers per second), and in theory nothing can travel faster than light In miles per hour, light speed is, well, a lot: about mph If you could travel at the speed of light, you could go around the Earth 75 times in one second

Light is a form of energy that travels as waves Their length — or wavelength — determines many of light’s properties