In the words of the infamous villain, Dr. Evil: “Lasers.” Lasers focus a narrow, directed light illumination on a specific spot, making them a great tool for shooting enemies from above – from a shark – in the case of cutting, burning, LD burning – or Dr. Evil. These activities produce or require all the heat. Laser beams travel at the speed of light, traveling more than 670 million miles per hour, making it the fastest thing in the universe. So how does a laser produce the slowest thing on earth?
First, it is important to understand the relationship between the temperature of a thing and its motion. Something heated is that the more energy it has and the faster it moves. Even things that seem perfectly fixed – say, a pen or your notebook – are not. At a microscopic level, the particles they create move rapidly. This is also true of organisms. Let us use laziness as an example. If you zoom in on the molecules made by the body of this famous slow animal, you will see them behave like bouncing and jumping indoors why. About 70% of the body of this animal made up of water and these water molecules travel hundreds of miles per hour.
Laser cooling: Therefore, it may seem amazing that I use bright, intense lasers to cool things in my lab tests. I am a physicist who is interested in how atoms and molecules behave at very cold temperatures. This is a strange world where quantum mechanics rules. In this state, particles sometimes behave like ocean waves and unbelievably, sometimes they can be in two different places at the same time. To study this phenomenal behavior, I use lasers to produce clouds of frigid molecules that are the coolest thing on Earth – what we call the Bose-Einstein synthesis. When you cool a bunch of atoms in almost perfect air, the coolest temperature possible, the atoms begin to adhere to quantum mechanics and behave amazingly.
Ultra-cold atoms can provide clues about how other strange materials, such as superconductors studying clouds, work. Superconductors carry more electricity than existing materials, so much so that they could one day used to build super high-speed trains.
Creating the slowest thing on Earth: So how exactly do lasers cool atomic clouds? In the lab, we start by burning lasers in a silver-white metal atom called ytterbium. These atoms, which are really heated, kept inside a 1-foot wide chamber. After a few seconds under the laser beam, however, they cool down, slow down are stuck together in the middle of the chamber. How is it? All light, including a laser, made up of photons, which energy packets that constantly moving. When we light a laser in our chambers, the atoms collide with the form in the flow of phagocytes and cool slowly – as if you were trying to run fast against a strong wind.
These slight collisions reduce the temperature of the atomic cloud by a few million degrees below absolute zero. It is 459 degrees below 0 degrees Fahrenheit. Still not enough reward this cloud for being the slowest thing in the world. It takes one last step to cool it down a bit, a technique we call physicists “evaporative cooling.”
First, we capture all atoms, sometimes using magnetic fields created by conducting electricity through wound-up wires. This creates an invisible well that holds the atoms: sitting at the bottom of the marble in the image. We then reduce the directions of this bowl-shaped ball field by reducing the electric current flowing through the wire. This allows fast, warm atoms to escape from the trap by zooming out of the “bowl”.
Only slowly, the atoms are behind – and they are really outside the absolute freezing point of absolute decimal one decimal one degree above absolute zero. The atoms of this cloud move slowly: if they travel in a straight line instead of shaking around, it will take them a whole hour to travel across a house. For comparison, molecules in your body can dash across that cell in a fraction of a second. Atoms in our icy clouds move literally at speeds slower than snails – and that cloud is the slowest thing on Earth.
