We already know that mesons are particles made of one quark and one antiquark. Mesons are divided into two types: flavored and unflavored.
Unflavored mesons are less complicated. An unflavored meson has a quark and antiquark of the same flavor — top and anti-top, for example. This meson is called the theta meson. Because the two quarks have the same flavor, it has no flavor. Flavored mesons are composed of a quark and antiquark with different flavors, such as strange and anti-bottom, called the strange B meson. Each combination of quark and antiquark has a unique name that identifies it.
All mesons are very unstable. The most stable mesons only last a few hundredths of a microsecond before they decay. Charged mesons decay into electrons and neutrinos. Uncharged mesons may decay to photons. I’m not sure what “may” means in this context; maybe it means that scientists are not sure about what they decay into.
Like electrons, quarks are fundamental particles. That means they can’t be separated into smaller parts. They are one of the smallest building blocks of matter.
Quarks come in six different flavors. The flavors are up, down, top, bottom, strange, and charm (If my little sister were a quark, she’d be a strange quark.)
Quarks and sometimes anti-quarks can combine to make two different kinds of particles, called mesons and baryons. Mesons have two quarks in them, and baryons have three quarks.
Neutrons and protons are baryons. Neutrons are made of one up quark and two down quarks. A proton is two up quarks and one down quark. Protons and neutrons make up the nucleus of an atom, so that gives you an idea of how tiny quarks are.
A kaon is an example of a meson. A kaon is made of one up quark and one strange anti-quark. A kaon is a kind of particle that decays very quickly — that means that it turns into smaller or different particles.
Anonymous asked: Hi Gwen! I first have to say that I LOVE your blog. Secondly, I have a question: I took a class on astrophysics in college, and my professor taught us about different theories about the "shape" of the universe. I have to admit that I really didn't understand that. Can you explain some theories (or maybe your favorite theory) about the shape of the universe?
Thank you for the compliment :)
Sure I can!
The “shape” of the universe is a theory about the eventual fate of the universe. At the beginning, the Big Bang pushed the universe open, and gravity is constantly pulling it closed. The shape of the universe tells you which force wins in the end. There are three shapes that the universe could be: flat, open, or closed.
A flat universe is like a draw in chess. Neither force wins. The universe keeps expanding, but over time it slows down and approaches zero. But it never stops.
An open universe is where the Big Bang wins. The universe keeps expanding without slowing down.
A closed universe is where the force of gravity wins. After a long time, a “Big Crunch” happens, which means the universe stops expanding and starts getting smaller. Some scientists think that if a Big Crunch happens, a new Big Bang might happen after that.
Anonymous asked: Gwen, I really like your blog! I learned about Dark Matter a few years ago, but am very confused by it. Can you explain what it is to me? Thanks! -Ben
Hi Ben! Thanks for the question. I loooooove dark matter! Dark matter can only be identified by its gravity. It holds galaxies together. It is unknown what dark matter is made of. Maybe it is made of wimps (weakly interacting massive particles.) Or axions, squarks, and photinos. Dark matter you cannot see, but it’s not the same as a black hole.
Dark matter is the name we gave stuff we don’t understand yet, so it is okay that you’re confused. I want to research dark matter when I grow up. It is still ver-r-ry mysterious.
hakushokuwaisei asked: How did you become interested in science, specifically in astrophysics?
I have always been interested in science. I watch a lot of Magic School Bus and I learned a lot about science from it. I’m a fan.
First I wanted to be a marine biologist, because I wanted to see things that live in the ocean. Then I became interested in being a pediatrician when I went to the doctor for a checkup, and I wanted to learn more about what doctors do. Finally, I got a book about physics, and I learned about Schrödinger’s cat, and black holes, and the theory of wormholes. There were a lot of interesting things in that book.
So now I want to help people discover new stuff about science.
By the way, here is a picture of me getting ready to go on a SCUBA-diving adventure.
This is Schrödinger’s Cat, which is my favorite thought experiment. A thought experiment is an experiment that’s just for thinking about. You aren’t supposed to do thought experiments in a lab.
Erwin Schrödinger liked to think about cats, I bet because he always wanted to have one. He was an Austrian physicist who developed a lot of experiments. This one is a quantum experiment about radioactivity.
In this experiment, you imagine that there is a source of radiation. The source is connected to a hinge and a hammer, and the hammer will break a bottle full of cyanide if the source decays. Decay is when a source of radiation emits radiation and particles like alpha and beta particles.
You also imagine that this setup is inside of a box with a cat, and this box is a special box that no information can pass through. That means there’s no way for us to tell what’s happening inside the box.
Schrödinger argued that, until we open the box, the cat is both alive and dead because of quantum superposition, which is when an object is in two states at once. Another example is how photons can act like both a particle and a wave.
Even though Schrödinger thought this up a long time ago, scientists are still trying to figure it all out, and that includes me.
Hi, astrophysics enthusiasts! It’s Gwen’s mom, Elizabeth.
Gwen is excited that so many people like her blog, and she really wanted to enable questions so that people could ask her about science stuff. I’ve enabled them— including anonymous questions so that you don’t need a tumblr to ask— but all questions will be screened by one of her parents.
Feel free to ask G about science facts or her feelings/opinions on science-y things.
(She would also like me to point out that she has created an “About The Picture” page where she explains her avatar.)
An atom is the basic building block of matter.
Atoms are made of electrons, which revolve around a nucleus, in a place called the electron cloud. Electrons are “elementary particles,” which means they are not made of any simpler parts. The nucleus is made of protons and neutrons, which in turn are made of particles called quarks. We’ll talk more about quarks in a later post.
Protons have a positive charge, and neutrons have no charge. Neutrons and protons hold each other together through a force called the strong force. If there weren’t any neutrons, the nucleus would fall apart, because protons have the same charge, so they repel each other. The neutrons help because they have strong force but they don’t have a charge.
Usually an atom has no charge, which means that it has the same number of protons and electrons. Sometimes an atom can get a charge. This happens when an electron moves away from one atom and joins another. Then the first atom has a positive charge (because there are more protons than electrons in it) and the second has a negative charge.
There’s another way that atoms can change: reactions can take place in the nucleus. One is called nuclear fission. This is when a neutron hits a nucleus and causes it to split into two smaller nuclei called fission fragments, and it also produces more neutrons. If the right kinds of atoms are around, this can cause a chain reaction, where the neutrons that get released cause more fission reactions.
The second kind of nuclear reaction is called nuclear fusion. This is when two nuclei hit each other and fuse into one bigger nucleus. It may release a neutron, but not always.
Nuclear reactions usually take place only under high heat and pressure. For example, fusion takes place in the sun’s core. Electron reactions can happen under any kind of temperature or pressure. For example, when you take off your sweater, you might hear a crackle—that is static electricity, which is a kind of electron reaction.
Quantum mechanics isn’t astrophysics, but it’s good to know. Let’s start with energy, because energy and matter are related.
Quantified energy is like a hose. The hose sprays only at whole-foot distances, and drops of exactly 1 ml each. In quantum mechanics, every electron can absorb none or all, but not part, of the energy of a photon, aka a quantum.
Energy comes in different forms: potential, kinetic, and matter. Matter is supercondensed energy. So that covers that.
The UV catastrophe was a theory saying if you heat a box in such a way it traps photons, it should produce infinite UV! The photon trap is known as a black box. This theory was tested by a physicist named Max Planck, who found it was incorrect. Instead, the box produces finite amounts of visible light.
Schrodinger said particles can behave like waves and vice-versa. Electrons travel like waves, and remember light and photons?
Light behaves like a particle when electrons absorb its energy! Young’s double-slit experiment shows how light also behaves like waves.
Remember, electrons are matter, electrons orbit the nuclei of atoms, and I will talk about atoms in my next post.
Hi, I’m Gwen and I like space. Here is some background on astrophysics in case you don’t know a lot about it.
Let’s start with what astrophysics is. Astrophysics is a branch of physics which works on space. There are a lot of odd things in astrophysics, like the theory of wormholes which can lead into other times or places, or black holes which can suck up anything beyond what’s called their “event horizons”— their points of no return.
Inside of a black hole, there is a single point called a singularity, whose density is infinite because it has no size. Anything that falls beyond the event horizon goes into part of the singularity forever. Outside the event horizon, there is an area called the ergosphere— anything in the ergosphere rotates with the black hole but does not fall in. A black hole’s strong gravity causes something passing far away from the black hole to continue its path, but change its course.
Stephen Hawking has theories that go against the singularity theory. Stephen Hawking says that instead of singularities, there are wormholes inside of black holes. He says that anything inside of a black hole you cannot see, and that might be because the stuff that’s gone beyond the event horizon might be in another universe.
I care about black holes and wormholes because I think they are very, very, very interesting.
I want to be an astrophysicist so I can figure out if wormholes are real, and learn more about space and quantum mechanics.
I will talk about quantum mechanics in my next post.