Physics in a nutshell

It is a well-established fact that the universe is expanding. It grows without center, like an inflating raisin cake, but an infinite raisin cake filling all of space in all directions. The raisins are the galaxies. A problem I’ve had with this explanation is that if everything were to double in size — galaxies, houses, you and me, rulers — then we’d never notice. I might be a towering giant, but if the room is equally huge, I wouldn’t know….

Here’s an explainer on beam stability during acceleration in a radio-frequency electric field.

Liquid nitrogen plumbing often develops a layer of ice, even in the summer. Photo: tibchris How do you cool off in the summer? A cold drink? A dip in the pool? Air conditioning? I guarantee that it involves making something else hotter: The second law of thermodynamics requires heat to flow from high temperatures to low temperatures unless additional energy is added to the system. Cooling off with water heats up the water, and air conditioners expel more heat outside…

This diagram shows the so-called tune space for an accelerated particle beam. The colored lines indicate resonances in tune space to be avoided. The dot represents a possible stable area where neither horizontal nor vertical tunes are near a line. In my last column, we concluded that circular accelerators that pass charged particles through a set of accelerating cavities many times is an effective strategy for achieving high energies. However, maintaining a beam while it makes many passes around the…

Somehow, you have to get those marvelous tracks to film. Imagine you’re a particle physicist in 1932. You have a cloud chamber that can show you the tracks of particles, and you have a camera to capture those tracks for later analysis. How do you set up an apparatus to take pictures whenever tracks appear? At first, you might just try to be quick with your finger, but since the tracks disappear in a quarter of a second, you’d end…

Click to view complete cyclotron illustration in Hyperphysics. The particle beam traverses the cyclotron gap starting near the center. It first moves from the bottom electrode to the top. Then the voltage reverses so that the beam can now cross over from the top electrode to the bottom. This pattern continues, and, with the help of a magnetic field, the beam travels in a gradually outward-moving path until it exits the cyclotron. Image: Hyperphysics In my last column we began…

Magnet systems in modern particle physics experiments are used to analyze particle charge and momentum, but the field is strong enough and covers enough volume to give a whale an MRI exam. Broadly speaking, a modern particle physics detector has three main pieces: (1) tracking, which charts the course of charged particles by letting them pass through thin sensors, (2) calorimetry, which measures the energy of charged or neutral particles by making them splat into a wall and (3) a…

Accelerators use cavities (the structures running through the center of the tunnel) to kick particle beams to higher and higher energies. Photo: Reidar Hahn In my last column I discussed scattering experiments as a major tool for gathering information about our world. I suggested that we could get more detailed information than our light beams, in combination with our eyes, can provide if we devised more powerful beams and detectors. We concluded that providing beam energy by using flashlight batteries…