How to teleport Schrödinger’s cat: this video presents the full quantum teleportation procedure, in which an arbitrary qubit (spin, etc) is teleported from Alice to Bob by way of a pair of particles entangled in a bell (EPR) state and the transmission of information via a classical channel.

Is it better to walk or run when it's cold out? If you run, then you have to deal with wind, wind chill, etc, but your body generates more heat. If you stay still, standing or walking slowly, you don't generate as much heat, but don't deal with the wind. Note: the simple calculations in this video don't very well take into account the baseline metabolic rate/heat generation, even at rest, of humans.

This is a video about how science is both inherently political and apolitical. And how hopefully we won't end up in nuclear war...

The universe is expanding – this we know from looking at red shifts of distant galaxies – but the acceleration of the universe's expansion is harder to measure. It requires measuring the change of recession velocity over time, and it's done by comparing Type Ia supernovas as standard candles at different distances, which is how we know the universe is accelerating!

This video is about what would happen if we built a giant ring around earth – what would happen to the ring, that is. Would if fall? Collapse? Start spinning?

This video is a footnote for the video about the ring around the earth: https://www.youtube.com/watch?v=4xSPlQUejd8 Essentially, a ring around the earth is in unstable equilibrium, so it would stay put, but then fall one way or the other as soon as any asymmetry (even thermal or quantum fluctuations) developed.

Neutral particle oscillation (like neutrino oscillation) is a superposition effect, and a similar effect can also be seen in a coupled double pendulum system where the interaction states are in superpositions of the "free" modes (called eigenstates).

This video is about a multistable perceptual illusion, similar to the hollow face illusion, whereby maps or aerial or satellite photos look upside down/inside out, ie, concave (valley) parts look convex and convex (mountainous) parts look concave. Just flip the images around and things will make a lot more sense! It's just because our eyes gauge depth based on the location of shadows, and the sun always casts shadows on the bottoms of things.

This video is about why it's harder to successfully land spacecraft and landers and rovers on Mars than on Earth, or Venus, or the Moon, or Titan, or asteroids. It all comes down to atmospheric density! When there's no atmosphere, you can do a powered descent in a flimsy tinfoil spacecraft like the Lunar Module, and when there's plenty of atmosphere you can do an unpowered descent via heat shield and parachutes like the space shuttle, Apollo command module, Soyuz, Huygens, etc. But on Mars with its thin air, you have to do both powered & unpowered descent, getting the worst of both worlds.

This video is about the local and global geometry and curvature of space and spacetime, aka, is space flat? Negatively curved? Positively curved? etc.

Can Batteries Power Everything? This video is about the physical and chemical limitations to electrolytic batteries, and how we might surpass the energy density and specific energy of lithium-ion batteries (like the Panasonic 18650 batteries used in the Tesla Model S, for example).

This video is about the differences between the corpses or final degenerate dense star forms that dead stars take: black holes, neutron stars, and white dwarfs. The main distinguishing features between them are the mass cutoffs (Chandrasekhar limit and Tolman-Oppenheimer-Volkoff Limit), the matter that makes them up (electrons, protons, neutrons, singularity?), and what holds them up against gravity – not thermal pressure from nuclear fusion like in a star like the sun, but electron or neutron degeneracy pressure (fermi pressure/pauli exclusion principle), and the strong nuclear force, and... nothing (in the case of a black hole).

This video is about how causal models (which use causal networks) allow us to infer causation from correlation, proving the common refrain not entirely accurate: statistics CAN be used to prove causality! Including: Reichenbach's principle, common causes, feedback, entanglement, EPR paradox, and so on.

Feedback loops and spurious correlations!

We live in an era of self driving cars, autonomous drones, deep learning algorithms, computers that beat humans at chess and go, and so on. So it’s natural to ask, will artificial superintelligence replace humans, take our jobs, and destroy human civilization? Or will AI just become tools like regular computers. AI researcher Max Tegmark helps explain the myths and facts about superintelligence, the impending machine takeover, etc.

This video is about Bell's Theorem, one of the most fascinating results in 20th century physics. Even though Albert Einstein (together with collaborators in the EPR Paradox paper) wanted to show that quantum mechanics must be incomplete because it was nonlocal (he didn't like "spooky action at a distance"), John Bell managed to prove that any local real hidden variable theory would have to satisfy certain simple statistical properties that quantum mechanical experiments (and the theory that describes them) violate. Since then, GHZ and others have managed to extend the theoretical work, and Alain Aspect performed the first Bell test experiment in the late 1980s.

This video is about using particle accelerators as part of the solar panel silicon wafer manufacturing process. The accelerators embed protons into the wafer crystals, allowing them to break and separate from the main crystal in much thinner wafers with no waste silicon. Thus, monocrystalline silicon can be used, which is more efficient.

This video is about the international system of units (SI), the international prototype kilogram (the IPK or "le grande k"), and specifically, why we need to redefine our base units in terms of fundamental constants - aka, concepts & ideas - rather than physical objects. The second is already defined in terms of a certain number of oscillations of a photon of the ground state hyperfine splitting energy of Cesium, the meter is then defined as how far light travels in a particular fraction of a second, and hopefully soon, the kilogram will be defined either using the Avogadro approach of counting silicon atoms in a sphere, or using the Watt (Kibble) Balance approach of measuring Planck's constant, h, as used in the formula E=hf for the energy of a photon, which relates to mass via Einstein's famous E=mc^2.

This video is about Simpson's paradox, a statistical paradox and ecological fallacy where seemingly contradictory results are implied by a single set of data depending on how it's grouped. The paradox can arise in medical studies, student test scores, and so on.

For ages I’ve been thinking about doing a video analyzing time travel in fiction and doing a comparison of different fictional time travels – some do use wormholes, some relativistic/faster than light travel with time dilation, some closed timelike curves, some have essentially “magic” or no consistent rules that make any sense, or TARDIS's, or whatever. This video is an explanation of how time travel functions in different popular movies, books, & shows – not how it works “under the hood", but how it causally affects the perspective of characters’ timelines (who has free will? can you change things by going back to the past or forwards into the future?). In particular, I explain Ender's Game, Planet of the Apes, Harry Potter and the Prisoner of Azkaban, Primer, Bill & Ted’s Excellent Adventure, Back to the Future, Groundhog Day, Looper, the video game “Braid”, and Lifeline.

This video is about how to tell whether or not university admissions are biased using statistics: aka, it's about Simpson's Paradox again!

This video is about the Schwarzschild radius of a black hole, (its "event horizon"), and how much mass and density is required to reach the point of no return where an object like a star, neutron star, red giant, etc will collapse into a black hole singularity. You can calculate it yourself using just the volume equation for a sphere, and the equation for the Schwarzschild radius (and knowing the speed of light and Newton's gravitational constant).

This video is about how efficient various reactions are at converting mass to energy (as we know from the Einstein mass-energy equivalence of E=mc^2). Antimatter is very efficient but it is not naturally-occurring. Chemical reactions like fire or explosions are very inefficient. Nuclear fission and nuclear fusion are better, but not amazing on an absolute scale. Non-rotating black holes (Schwarzschild) and rotating (Kerr) are by far the most efficient, due to their accretion disks and very small radius of their innermost stable circular orbits.