Classical vs quantum mechanics

Space, time and gravity get weird when they are studied at a super subatomic scale, where the quantum nature of gravity starts to kick in.

Albert Einstein taught us that space and time could warp and bend like a piece of fabric. We experience this warping of the space-time continuum as grav...

Technical issues

When you’re learning quantum mechanics as a student, you’re taught the classical model for something, then given rules for quantising that classical theory. However, classical theories do not define quantum theories very well. When you straightforwardly app...

The idea is that all the quantum mechanical information inside a black hole can in certain circumstances be considered as spread out on the boundary of the black hole. 

If you think of the interior of the black hole as a three-dimensional region of space, and the boundary as a two-dimension...

In theoretical physics, the AdS/CFT correspondence is called Maldacena duality or gauge/gravity duality.

• Juan Maldacena applied the holographic principle to black holes and anti-de Sitter space. Because there’s no gravity there, you can define quantum field theory on it and have no con...

Consider gas in a box. A box full of some gaseous substance is made of atoms and molecules.

When we look at the gas in the box with our eyes, or our thermometers, we don’t see each individual atom or molecule, its position and velocity. We see coarse-grained features of the system. We can i...

The Higgs boson is a real particle but it’s hard to detect because it has a very short lifetime and quickly decays into other particles.

It can decay into two particles, an electron and a positron. When you consider quantum mechanics, you can predict roughly how long it will take th...

The particles and forces of the world come from fields that spread all throughout space and time and have a quantum mechanical nature. There’s a quantum mechanical field for the photon, the gluon, the Higgs boson, for gravity, etc. But the important thing to remember about field theory is that

Classically, for a particle, you have a clear idea of where a particle is and how fast it’s moving. And you can measure whatever you want.

However, there is less agreement on what quantum mechanics is saying because you have to use words like "measurement" and "observation." You can observe...