Sure, our atmosphere protects us from a horrible Universe that’s trying to kill us, but sometimes it prevents us from learning stuff too. Case in point, the atmosphere blocks highly energetic particles from reaching our detectors. But there’s a way astronomers can still detect their influence: Cherenkov Radiation; the cascade of radiation that blasts out as a high-energy particle makes its way through the atmosphere, like a radioactive rainshower.
Ep. 288 Phases of Matter
As we quickly learn with water, matter can be in distinct phases: solid, liquid, gas and plasma; it all depends on temperature. But why do different materials require different temperatures? And what’s actually happening to the atoms themselves as the material switches phases?
Ep. 287 E=mc^2
It’s mind bending to think about this, but the light in your house, and the house itself are really the same thing. Matter and energy are interchangeable. This was the amazing revelation made by Albert Einstein, with his famous formula: E=mc^2. This is the process that the Sun uses to turn hydrogen into radiation through fusion, and the terrible damage from a nuclear weapon.
Ep. 270: Inertia
An object at rest tends to stay at rest. An object in motion tends to stay in motion. Isaac Newton dismantled the traditional idea that objects would tend to slow down over time, and described the concept of inertia: the amount an object will resist changes in its motion.
Ep. 269: Mass
Last week we talked about energy, and this week we’ll talk about mass. And here’s the crazy thing. Mass, matter, the stuff that the Universe is made of, is the same thing as energy. They’re connected through Einstein’s famous formula – E=mc2. But what is mass, how do we measure it, and how does it become energy, and vice versa.
Ep. 268: Energy
Our entire civilization depends on energy: getting it, converting it, burning it, and conserving it. But how do physicists think about energy? How do they measure and quantify it. And what is energy’s special relationship with mass?
Ep. 267: Infinities
Forever is a funny thing. Today we’re going to talk about infinities. That’s right, all the different kinds of possible infinities. How you add them, subtract them, and use them to think about the scale of the Universe.
Ep. 263: Radioactive Decay
Nothing lasts forever, even atoms. Heavier elements decay into lighter elements, releasing energy as radiation. But thanks to this radiation, astronomers can get a glimpse into what’s going on inside distant start. Let’s take a look at the whole process of radioactive decay, the different events that happen, and how humans use this fundamental force of nature for our own needs.
Ep. 260: The Technology of Lasers and Masers
Just when you think you understand it, light will do some amazing things. Just look at the discovery of lasers, and their use in almost every technology you can think of: from cutting, to transmitting information to, yes, astronomy. And nature has figured out its own version of laser technology, called the maser, which has kept astronomers puzzled and excited for years.
Ep 254: Reflection and Refraction
Light can do some pretty strange stuff, like pass through objects and bounce off them; it can be broken up and recombined. In fact, everything we “see” is actually the end result of reflection and refraction of light. Time to understand how it all works.
Ep. 253: Rayleigh Scattering (Why is the Sky Blue?)
Next time a kid asks you, why is the sky blue? Answer them: because of Rayleigh scattering. If they’re not happy with that answer, feel free to expand based on the knowledge we’re about to drop today, right into your brain.
Ep. 252: Heisenberg Uncertainty Principle
Quantum theory is plenty strange, but one of the strangest discoveries is the realization that there’s a limit to how much you can measure at any one time. This was famously described by Werner Heisenberg, with his uncertainty principle: how you can never know both the position and motion of a particle at the same time.
Ep. 250: Precision
Accuracy, precision and reproducibility. These are the foundations of science that make our progress possible. How do these play into a scientist’s daily activities? And just how precise can we get with our measurements?
Ep. 249: Schrödinger's Cat
You’ve probably all heard of Schrödinger’s Cat, that strange thought experiment designed by Erwin Schrödinger to show how the strange predictions of quantum theory could impact the real world. No cats will be harmed in the making of this episode, maybe.
Ep. 206: Fission
Last week we talked about fusion, where atoms come together to form heavier elements. This week, everything comes apart as we talk about nuclear fission. How it occurs naturally in the Universe, and how it has been harnessed by science to produce power, and devastating weapons.
Ep. 205: Fusion
When the Universe formed after the Big Bang, all we had was hydrogen. But through the process of fusion, these hydrogen atoms were crushed into heavier and heavier elements. Fusion gives us warmth and light from the Sun, destruction with fusion bombs, and might be a source of inexpensive energy. We’ll also look into the controversy of cold fusion.
Ep. 204: Temperature
Now we’re going to answer a question that a 4-year old might ask – what is temperature? Why are things hot and why are they cold? How hot or cold can they get? And how is this all important for astronomy?
Ep. 181: Rotation
Everything in the Universe is spinning. In fact, without this rotation, life on Earth wouldn’t exist. We need the conservation of angular momentum to flatten out galaxies and solar systems, to make planets possible. Let’s find out about the physics involved with everything that spins, and finally figure out the difference between centripetal and centrifugal force.
Ep. 165: Doppler Effect
You know how a police siren changes sound when it passes by you? That’s the doppler effect. It works for sound waves and it works for light waves. Astronomers use the doppler effect to study the motion of objects across the Universe, from nearby extrasolar planets to the expansion of distant galaxies. Doppler shift is the change in length of a wave (light, sound, etc.) due to the relative motion of source and receiver. Things moving toward you have their wavelengths shortened. Things moving away have their emitted wavelengths lengthened.
Ep. 164: Inside the Atom
We’ve talked about the biggest of the big, now let’s focus in on the smallest of the small. Let’s see what’s inside that basic building block of matter: the atom. You probably know the basics, but with ever more powerful particle accelerators, physicists are revealing particles within particles, announcing new discoveries all the time.
Ep. 140: Entanglement
One of the most amazing aspects of quantum mechanics is quantum entanglement. This is the strange behavior where particles can become entangled, so they’re somehow connected to one another – no matter the distance between them. Interact with one particle and the other reacts instantly; even if they’re separated by billions of light-years.
Ep. 139: Energy Levels and Spectra
Last week we took a peek into the tiny world of quantum mechanics, and its unintuitive, but very accurate mathematical predictions. And although we all appreciate the physics lesson, you’re probably wondering what this all has to do with astronomy. Well, today we bring it all home and explain how quantum mechanics has given astronomers one of the most powerful tools they have to study the nature of the cosmos.
Ep. 138: Quantum Mechanics
Quantum mechanics is the study of the very tiny; the nature of reality at the smallest scale. It’s a science that defies common sense, and delivers no helpful analogies. And yet it delivers the goods, making scientific predictions with incredible accuracy. Let’s look into the history of quantum theory, and then struggle to comprehend its connection to the Universe.
Ep. 117: Time
Today, time rules our lives. We live each day with the moments broken up into hours, minutes and seconds. We never seem to have enough time. But can you imagine not being able to tell time at all, where the movements of the Sun and the stars was the only way to know what time it was? Let’s learn about the history of time, methods of telling time, and Einstein’s historic discovery that time isn’t as fixed as we thought it was.
Questions Show – light speed, Andromeda galaxy, dark matter and black holes
Another week, another roundup of your questions. This week listeners asked: will reaching light speed destroy the Universe? When is Andromeda going to look really, really cool with the unaided eye? Why didn’t dark matter all turn into black holes? And there’s even more. If you’ve got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we’ll try to tackle it for a future show.