Neutrinos are perhaps the most enigmatic particles in the universe. They were first discovered in the 1950s as a product of radioactive decay, but they are also produced in nuclear fusion reactions. As a result, copious amounts of neutrinos are produced in the Sun through the pp-chain and CNO nuclear fusion processes in the core of our star. This makes the Sun a perfect candidate for doing neutrino astronomy. But when we first starting observing solar neutrinos in the 1960s, revealed mystery known as the solar neutrino problem. The solution to this problem wasn’t proven until the late 1990s, and it demonstrated that neutrinos are far more strange than we had imagined.
Highland Fling
Yesterday I talked about millisecond pulsars, and the way in which they might gain such rapid rotation. Another property of millisecond pulsars is that they demonstrate very clearly that pulsars are neutron stars. It all has to do with their rapid rotation and the physics of centripetal (or centrifugal) force.
Big Bang Burger Bar
Lately there’s been news of a radical new theory proposing that the universe began from a hyper-dimensional black hole. Most of the reports seem to stem from an article posted a while back on the Nature blog, which references the original paper. So let’s have a little reality check.
Cloud Atlas
Atoms are made of electrons, protons and neutrons. Protons and neutrons are in turn made up of quarks. These are just some of the elementary particles that make up the foundation of modern particle physics. But how do we know about these particles when we can’t see atoms directly, much less their constituents? One of the early methods was through a device …
Calvinball
In Bill Watterson’s comic strip Calvin and Hobbes, there is a game known as Calvinball. The basic idea of Calvinball is that rules are added by players as the game progresses. Players can add to the rules as you go along, but once a rule is in place it can’t be undone. The result is a hodge-podge game where the action is incomprehensible by anyone but the participants. Often in popular science quantum theory is portrayed as the physics version of Calvinball, even though that isn’t how quantum theory works. Quantum objects may be strange, but they aren’t making up rules as the universe plays on.
Sword of Damocles
According to legend, when Damocles declared that his king, Dionysius, must have a posh and easy life, Dionysius offered to trade places with Damocles. There was only one catch. Dionysius decreed that a sword be suspended over the throne by a single horse hair, so that Damocles would always know the peril of being king. Since then the Sword of Damocles has come to represent a threat of doom that could strike without warning. While the prospect of living under a hanging sword doesn’t seem pleasant, stories of impending doom are quite popular, particularly within popular science.
Into Darkness
Yesterday I wrote about how interstellar clouds of methyl alcohol can be induced to create microwave laser regions (astrophysical masers). This was due to a stimulated emission of light in excited atoms. As strange as that seems, you can also have the opposite effect, or stimulated absorption.
Gravity Check
Yesterday I wrote about how we test whether unitless constants such as alpha (α) change over the history of the universe. You might also have noticed that I said if such constants did change, then it would mean either fundamental physical constants change or there is some exotic physics going on. We looked at the physical constants yesterday, so today let’s look for exotic physics.
Variables of Nature
Within physics there are certain physical quantities that play a central role. These are things such as the mass of an electron, or the speed of light, or the universal constant of gravity. We aren’t sure why these constants have the values they do, but their values uniquely determine the way our universe works. For example, if the mass of electrons were smaller, atoms would be smaller. If the gravitational constant were larger, you’d need less mass to create a black hole, and neutron stars might not exist.