ELI5: Explain Like I'm 5

Luke's variational principle

Hey there!

Do you remember how in math, we sometimes use a formula to find the solution to a problem? Well, Luke's Variational Principle is a formula that helps us find the solution to a problem in physics called the Hamiltonian.

Now, the Hamiltonian is a fancy word for the total energy of a system, which means how much energy is present in something like a moving object or a group of objects. This energy is made up of two types: kinetic energy (how fast something is moving) and potential energy (how much energy an object has because of its position or shape).

The Hamiltonian is important in physics because it helps scientists understand how energy behaves in a system. But, sometimes it's really hard to figure out what the Hamiltonian is for a particular system, especially if it's really complicated.

That's where Luke's Variational Principle comes in! Luke's Variational Principle helps scientists figure out the Hamiltonian by looking at how the energy of a system changes when it moves from one state to another.

To do this, scientists use something called a Lagrangian, which is like a different formula that helps them understand how the energy in a system is changing. They then use Luke's Variational Principle to figure out what the Hamiltonian is.

Think of it like a puzzle, where you have some pieces (the Lagrangian) and you need to put them together to make a bigger picture (the Hamiltonian). Luke's Variational Principle is like a tool you use to help you figure out how to put the pieces together so they make sense.

So, in short, Luke's Variational Principle is a formula that helps scientists figure out the Hamiltonian of a system by looking at how the energy of that system changes from one state to another. It's like a puzzle piece that helps scientists solve a big puzzle!