minutephysics
How to Find an Exoplanet
updated
We think of the moon as orbiting the earth, following a spiraling trajectory as the earth itself orbits the sun. But this is wrong. Not only is the moon's orbit NOT a spiral... there's an argument that the moon actually orbits the sun, not the earth! The moon's trajectory is more like a 12-sided polygon with curved corners than it is a spiral or even a wiggly line.
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Pressure *can* melt ice - like, you only need 500 times atmospheric pressure to melt ice down to negative four degrees celsius. If you have 1000 times atmospheric pressure (like at the bottom of the Mariana trench), then you'll melt ice down to around negative nine celsius. But that's for fresh water. For salty sea water, things are different.
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Created by Henry Reich
If you take a piece of white paper into different lighting conditions, it will be an objectively different color in each situation, but our brains are clever enough to make us feel like it's still white - it's still the same piece of paper, after all. To match our experience, cameras have to do this, too, "balancing" the colors of an image so that a white object looks white under a given light, rather than some other color. And the typical unit to measure the color of a light is the Kelvin. Which is weird, because Kelvin is a unit for measuring temperature, not color. What temperature and the color in a photograph have to do with each other comes down to history and physics.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Solar eclipses don't just happen here on earth - moons of other planets also pass between those planets and the sun, resulting in various types of solar eclipses on Mars, Jupiter, Saturn, Uranus, Neptune, and even non-planets like Pluto, Eris and various asteroids. So, where are the best eclipses in the solar system? For that, we need a tier list.
This Product is supported by the NASA Heliophysics Education Activation Team (NASA HEAT), part of NASA’s Science Activation portfolio.
The material contained in this document is based upon work supported by a National Aeronautics And Space Administration (NASA) grant or cooperative agreement. Any questions, findings, conclusions or recommendations expressed in this materials are those of the author and do not necessarily reflect the views of NASA.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This Product is supported by the NASA Heliophysics Education Activation Team (NASA HEAT), part of NASA’s Science Activation portfolio.
The material contained in this document is based upon work supported by a National Aeronautics And Space Administration (NASA) grant or cooperative agreement. Any questions, findings, conclusions or recommendations expressed in this materials are those of the author and do not necessarily reflect the views of NASA.
Support MinutePhysics on Patreon!
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This Product is supported by the NASA Heliophysics Education Activation Team (NASA HEAT), part of NASA’s Science Activation portfolio.
The material contained in this document is based upon work supported by a National Aeronautics And Space Administration (NASA) grant or cooperative agreement. Any questions, findings, conclusions or recommendations expressed in this materials are those of the author and do not necessarily reflect the views of NASA.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
If you’re in scorching heat, or when your body is working hard and you’ve got hot, hot sweat all over, sticky and stifling - does wiping off the sweat help you cool off? Or is it better to leave it on?
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REFERENCES
Hyperphysics:
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/sweat.html
Engineering Toolbox Mollier Diagram:
http://www.engineeringtoolbox.com/psychrometric-chart-mollier-d_27.html
Sweat Info
http://www.anaesthesiamcq.com/FluidBook/fl3_3.php
Other articles:
http://www.slate.com/articles/health_and_science/explainer/2012/06/should_you_wipe_away_your_sweat_or_does_that_keep_you_from_cooling_down_.html
http://onlinelibrary.wiley.com/doi/10.1111/j.1748-1716.2012.02452.x/abstract
http://lifehacker.com/5921036/dont-wipe-your-sweat-off-your-brow-itll-cool-you-down-faster
http://www.realclearscience.com/2012/06/28/does_wiping_sweat_prevent_you_from_cooling_off_247729.html
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CALCULATIONS
Typical adult human body surface area ~ 1.5-2 m^2
en.wikipedia.org/wiki/Body_surface_area
Evaporation rate at 25°C and 50% humidity, slight air movement (v~.5m/s) = .35kg/m^2/hr
http://www.engineeringtoolbox.com/evaporation-water-surface-d_690.html
So in these conditions, a sweat-covered human can expect to evaporate ~.5-.75 L of water in an hour (For higher humidity (60-70%) it goes to ~.37-.5 L of water/hr). That amounts to ~0.25-0.35mm of sweat (covering the whole body) evaporated in an hour, or 6 micrometers every minute.
Water has latent heat of 2,270 kJ/kg (http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html), so in an hour a human can lose ~1100-1700 kJ of energy. (2270/4.1868 ~ 542 Cal)
BUT that assumes all of the energy came from the person. If some proportion of it came from the air (~1/3-1/2?) then the person is only cooled down partially.
Mass of a human ~ 60-80kg (en.wikipedia.org/wiki/Body_weight), assuming ~specific heat of water, ie 4 kJ/kg/K, could decrease temp by ~4.5-5°C.
Energy used in moderate-hard exercise is ~20-30 kJ/kg/30 min, or ~40-60kJ/kg/h (http://www.weightloss.com.au/weight-loss/weight-loss-tools/exercise-energy-charts.html). Let’s say 50kJ/kg/h, which for average human amounts to 3000-4000 kJ/hr
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
The material contained in this document is based upon work supported by a National Aeronautics And Space Administration (NASA) grant or cooperative agreement. Any questions, findings, conclusions or recommendations expressed in this materials are those of the author and do not necessarily reflect the views of NASA.
We are in the Golden Age of Solar Eclipses, but only for the moment. In fact, I'd argue we're already past peak solar eclipse and it's all downhill from here.
MinutePhysics is on twitter - @minutephysics
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
A lot of people took pictures of the recent solar eclipse in North America and got photos where there’s a ghostly image of the eclipse floating in the sky nowhere near where the sun is!
REFERENCES:
Lens flare prediction based on measurements with real-time visualization doi.org/10.1007/s00371-018-1552-4
Physically-Based Real-Time Lens Flare Rendering http://doi.acm.org/10.1145/1964921.1965003
From the Series of Articles on Lens Names: Tessar, by H. H. Nasse. Carl Zeiss Camera Lens Division March 2011
cambridgeincolour.com/tutorials/lens-flare.htm
toolfarm.com/tutorial/in-depth-lens-flares-for-video
petapixel.com/what-is-lens-flare
maxon.net/en/red-giant/vfx-suite/real-lens-flares
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I was sent a magnetic guitar pick to review, so I reviewed it. Does it work? How? Why? What's the physics of electric guitar strings and pickups? Are magnets useful? Do they affect the strings? The pickups?
Thanks to Pete B. for loaning me the guitar.
Here are links to the youtube channel for the people who make the magnetic pick: youtube.com/@xpick
And the videos critiquing it
Samurai Guitarist: youtube.com/watch?v=zXTHRh1bQsg
Forlorn Hope: youtube.com/watch?v=2E8rrt5gE8Q
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about the physics of geosynchronous and geostationary orbits, why they exist, when they don't, when they're useful for communication/satellite TV, etc.
REFERENCES
Fraction of a sphere that's visible from a given distance
math.stackexchange.com/questions/1329130/what-fraction-of-a-sphere-can-an-external-observer-see
Orbital period
en.wikipedia.org/wiki/Orbital_period
Kepler's third law
en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Third_law
Kepler's 3rd law (which can be derived from Newton's law of gravitation and the centripetal force necessary for orbit as mr\omega^2=G\frac{mM}{r^2}, and using \omega=\frac{2\pi}{T}) is
T = 2pi Sqrt(r^3/(GM)) where M is the mass of the central object, G is the gravitational constant. Alternatively, we can solve for r, r = (T^2/(4pi^2) GM)^(1/3) ~ T^(2/3)/M^(1/3) = (T^2/M)^(1/3).
There is a limit (kind of like the Roche limit but for rotations). A rotating solid steel ball or other chunk of metal that has tensile strength (ie that isn't just a pile of stuff held together by gravity like most planets) would be able to spin faster.
Calculate how much of a planet's surface you can see from a given geosynchronous orbit/radius? (Obviously for lower ones you can see less, etc) - d/(2(R+d)) where d is distance to surface, ie, R is sphere radius, R+d is object radius from sphere center.
Let's plug that in with r being the geostationary orbit radius. That is, we have \frac{1}{2} \left(1- \left(\frac{4 \pi^2 R^3}{T^2 G M }\right)^{1/3}\right)
Average density of a sphere \rho is given by \rho =M/(\frac{4}{3}\pi R^3), ie \rho=\frac{3M}{4 \pi R^3} aka
\frac{M}{R^3}=\frac{4}{3}\pi \rho.
So we can convert the "fraction of planet surface seen" to
\frac{1}{2} \left(1- \left(\frac{3 \pi}{G \rho T^2}\right)^{1/3}\right)
So as either \rho or T\to \infty, the fraction goes to a maximum of \frac{1}{2}. And the point of "singularity" where the orbit coincides with the surface is where G\rho T^2=3\pi, aka \rho=\frac{3\pi}{GT^2}. For a rotation period of 3600s, that corresponds to a density \rho \approx 11000kg/m^3, which is roughly twice the density of the earth. For a rotation period of 5400s, we have \rho\approx 4800kg/m^3, which is basically the density of the earth.
Alternately, if we plug the density of the earth in to an orbit of period 5400s, we get as a fraction of the planet seen:
\frac{1}{2} \left(1- \left(\frac{3 \pi}{G \rho T^2}\right)^{1/3}\right) = 0.02
aka 2\% of the earth's surface.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about a better way to understand Penrose tilings (the famous tilings invented by Roger Penrose that never repeat themselves but still have some kind of order/pattern).
This project was a collaboration with Aatish Bhatia (https://aatishb.com).
REFERENCES
Explore Penrose and Penrose-like patterns: aatishb.com/patterncollider
Video by Derek Muller/Veritasium about Penrose Patterns: youtube.com/watch?v=48sCx-wBs34
Music algorithmically generated, algorithm designed by Henry Reich
N.G. de Bruijn’s paper introducing the pentagrid/Penrose idea: https://www.math.brown.edu/reschwar/M272/pentagrid.pdf
De Bruijn, N.G., 1981. Algebraic theory of Penrose’s non-periodic tilings of the plane. Kon. Nederl. Akad. Wetensch. Proc. Ser. A, 43(84), pp.1-7.
Here are some excellent in-depth references on how to construct Penrose Tiles Using the Pentagrid Method:
Penrose Tilings Tied up in Ribbons by David Austin: http://www.ams.org/publicoutreach/feature-column/fcarc-ribbons
The Empire Problem in Penrose Tilings by Laura Effinger-Dean: http://www.cs.williams.edu/~bailey/06le.pdf
Pentagrids and Penrose Tilings by Stacy Mowry & Shriya Shukla: https://web.williams.edu/Mathematics/sjmiller/public_html/hudson/HRUMC-Mowry&Shukla_Pentagrids%20and%20Penrose.pdf
Penrose Tiling by Andrejs Treibergs: http://www.math.utah.edu/~treiberg/PenroseSlides.pdf
Algebraic Theory of Penrose's Non-Periodic Tilings of the Plane by N. G. de Bruijn: https://www.math.brown.edu/reschwar/M272/pentagrid.pdf
Particularly good and helpful, and (we think) an undergrad thesis which is impressive!: http://www.cs.williams.edu/~bailey/06le.pdf
An interesting popular science read on the discovery on quasicrystals and their connection to Penrose Tilings:
The Second Kind of Impossible by Paul Steinhardt: bookshop.org/books/the-second-kind-of-impossible-the-extraordinary-quest-for-a-new-form-of-matter-9781476729930/9781476729930
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REFERENCES
Page with TONS of info about water and ice
water.lsbu.ac.uk/water/water_density.html
Specifically, a graph showing density & temperature & pressure along the phase line!!!!!
water.lsbu.ac.uk/water/images/ice_water_density_1.gif
Water freezing in isochoric conditions (theory):
nature.com/articles/s42005-020-0303-9
Water pressure/density calculator
omnicalculator.com/physics/water-density
http://www.csgnetwork.com/water_density_calculator.html
Article about pressure vs temperature vs volume expansion: Using freezing as a source of energy
link.springer.com/article/10.1007/s42452-018-0139-z#:~:text=It%20is%20well%20known%20that,energy%20using%20a%20hydraulic%20motor.
Latent heat of water at 0C
link.springer.com/referenceworkentry/10.1007/1-4020-3266-8_124#:~:text=A%20total%20of%20334%20J,the%20latent%20heat%20of%20fusion.
Mariana Trench
en.wikipedia.org/wiki/Mariana_Trench#:~:text=At%20the%20bottom%20of%20the,atmospheric%20pressure%20at%20sea%20level.
Regelation on wikipedia
en.wikipedia.org/wiki/Regelation#:~:text=Regelation%20is%20the%20phenomenon%20of,heavy%20weight%20attached%20to%20it.
Using Ice VI to freeze meat without tissue damage
sciencedirect.com/science/article/abs/pii/S0309174003001931
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Barnes and Noble: bit.ly/3AKwXIl
Penguin Random House: bit.ly/3HgfucP
Books-A-Million: bit.ly/3Q4bEH3
Bookshop: bit.ly/3q26vVk
IndieBound: bit.ly/3TyhX8W
Apple Books: bit.ly/3wNNBp9
FOR INTERNATIONAL EDITIONS, Including the UK and Germany, click here: xkcd.com/what-if-2
The #1 New York Times bestselling author of What If? and How To answers more of the weirdest questions you never thought to ask
The millions of people around the world who read and loved What If? still have questions, and those questions are getting stranger. Thank goodness xkcd creator Randall Munroe is here to help. Planning to ride a fire pole from the Moon back to Earth? The hardest part is sticking the landing. Hoping to cool the atmosphere by opening everyone’s freezer door at the same time? Maybe it’s time for a brief introduction to thermodynamics. Want to know what would happen if you rode a helicopter blade, built a billion-story building, made a lava lamp out of lava, or jumped on a geyser as it erupted? Okay, if you insist.
Before you go on a cosmic road trip, feed the residents of New York City to a T. rex, or fill every church with bananas, be sure to consult this practical guide for impractical ideas. Unfazed by absurdity, Munroe consults the latest research on everything from swing-set physics to airliner catapult–design to answer his readers’ questions, clearly and concisely, with illuminating and occasionally terrifying illustrations. As he consistently demonstrates, you can learn a lot from examining how the world might work in very specific extreme circumstances.
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What if Pluto were plutonium? And Uranus uranium? And Mercury mercury? This video is based off of a chapter of the new xkcd book "What If? 2"
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
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This video is about what happens if you try to pass a portal (like in the video game Portal or Portal 2) through itself - do you get a paradox? Infinite recursion? Impossibility? Contradiction? The end of the world? Collapse of the wavefunction? Ultimately it ends up looking beautiful and weird and recursive and... just watch the video :)
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
What happens if you extend a piston through a portal? Or try to sandwich a cube between two portals? That's right, it's time to explore more portal paradoxes!
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
In order to make something good, you need to have the right combination of three things: Quality, Discernment and Taste. This video is about quality vs quantity, the paradox of quality, how to make good content and good videos, etc. Based on my experience over the last decade running a collaborative creative business, MinuteEarth, where we do regular internal reflection and training on the craft of science communication.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Link to Patreon Supporters: http://www.minutephysics.com/supporters
MinutePhysics is on twitter - @minutephysics
And facebook - http://facebook.com/minutephysics
Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about elastic and inelastic collisions in 1D, 2D and 3D - and how the collision of conservation of energy with conservation of momentum, plus a secret direction, results in a completely predetermined behavior for most collisions.
REFERENCES
1D Collision Calculator:
http://hyperphysics.phy-astr.gsu.edu/hbase/col1d.html#c1
Elastic collision of spheres Wolfram
demonstrations.wolfram.com/ElasticCollisionsOfTwoSpheres
Oblique collisions of two 2D spheres
iopscience.iop.org/article/10.1088/1361-6404/aab330
Ballistic Pendulum
http://hyperphysics.phy-astr.gsu.edu/hbase/balpen.html
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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MinutePhysics is on twitter - @minutephysics
And facebook - http://facebook.com/minutephysics
Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
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MinutePhysics is on twitter - @minutephysics
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Support MinutePhysics on Patreon: http://www.patreon.com/minutephysics
Link to Patreon Supporters: http://www.minutephysics.com/supporters
MinutePhysics is on twitter - @minutephysics
Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about Bell's Spaceship Paradox of Special Relativity, wherein a pair of rockets (or spacecraft) connected by a weak thread accelerate with uniform acceleration, maintaining the same separation, and the question is: does the thread break? And if so, why?
REFERENCES
Interactive Spacetime Globe by Alexander Wu:
alexonscience.com/projects/spacetimeglobe
Read an overview on Wikipedia:
en.wikipedia.org/wiki/Bell%27s_spaceship_paradox
John Baez on Bell's Spaceship Paradox, Rindler Acceleration, etc
https://math.ucr.edu/home/baez/physics/Relativity/SR/BellSpaceships/spaceship_puzzle.html
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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This video is about using Bohmian trajectories to visualize the wavefunctions of hydrogen orbitals, rendered in 3D using custom python code in Blender.
REFERENCES
A Suggested Interpretation of the Quantum Theory in Terms of "Hidden" Variables. I
David Bohm, Physical Review, Vol 85 No. 2, January 15, 1952
Speakable and Unspeakable in Quantum Mechanics
J. S. Bell
Trajectory construction of Dirac evolution
Peter Holland
The de Broglie-Bohm Causal Interpretation of Quantum Mechanics and its Application to some Simple Systems by Caroline Colijn
Bohmian Trajectories as the Foundation of Quantum Mechanics
http://arxiv.org/abs/0912.2666v1
The Pilot-Wave Perspective on Quantum Scattering and Tunneling
http://arxiv.org/abs/1210.7265v2
A Quantum Potential Description of One-Dimensional Time-Dependent Scattering From Square Barriers and Square Wells
Dewdney, Foundations of Physics, VoL 12, No. 1, 1982
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
The Solution to the Windmill Paradox. This video is about the tradeoff of Windmills: the fact that the more kinetic energy you extract from the wind the slower the wind goes, the less wind you have to extract energy from, etc. How much energy is the sweet spot to extract from the wind??
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about the "Kelvin wake" shape of water wakes behind boats - we talk about mach angle, dispersion, superposition of many waves, and how these all lead to the pattern of a wake. We don't get into Froude number though...
REFERENCES
Boat Wake Wikipedia Page: en.wikipedia.org/wiki/Wake
Interactive Boat Wake Simulation: observablehq.com/@rreusser/dispersion-in-water-surface-waves
Feynman Lectures on Water Waves: https://www.feynmanlectures.caltech.edu/I_51.html#Ch51-S4
Building up a Boat Wake from V-Shaped Wakes: editor.p5js.org/aatish/full/bDiykicsC
Wave Dispersion: en.wikipedia.org/wiki/Dispersion_relation
Mach angle shock waves:
sciencedirect.com/topics/engineering/mach-angle
Ship Wakes - Kelvin or Mach Angle? Rabaud and Moisy Paper: journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.214503
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about how physics dictates the design of modern windmills - why they are so big, have so few blades, and have such skinny blades.
REFERENCES
H. Glauert: Aerodynamic Theory, 1935 Division L (Airplane Propellers), Chapter XI: Windmills and Fans
Wind power extraction fundamentals
https://home.uni-leipzig.de/energy/energy-fundamentals/15.htm
Betz's Law
en.wikipedia.org/wiki/Betz%27s_law
Tip Speed Ratio
en.wikipedia.org/wiki/Tip-speed_ratio
Aerodynamics of Wind Turbines Book
amazon.com/Aerodynamics-Wind-Turbines-Physical-Analysis/dp/1119405610
Penn State Wind Turbine Aerodynamics Lesson
https://www.e-education.psu.edu/aersp583/node/469
Wind Power Physics youtube video
youtube.com/watch?v=qx_M0nvDIGU
Why do Wind Turbines Have Three Blades?
rosemary-barnes.medium.com/why-do-wind-turbines-usually-have-3-blades-f7f95d714869
Wind Power Fundamentals
http://web.mit.edu/windenergy/windweek/Presentations/Wind%20Energy%20101.pdf
Wind Power Explained
calcunation.com/blogs.php/the-physics-behind-wind-turbines
Drag Coefficient
http://dx.doi.org/10.1615/AtoZ.d.drag_coefficient
Reynolds Number and Drag
http://www2.eng.cam.ac.uk/~mpj1001/learnfluidmechanics.org/LFM_blank_notes/handout_8_v3.pdf
Reynolds Number
en.wikipedia.org/wiki/Reynolds_number
Viscosity of Air
en.wikipedia.org/wiki/Viscosity#Air
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video covers the General theory of Relativity, developed by Albert Einstein, from basic simple levels (it's gravity, curved space) through to the concepts of how curved spacetime is represented by psuedo-Riemannian manifolds with Lorentzian signature (that is, special relativity and minkowski space are the local tangent space), how matter and energy are represented by an energy-momentum tensor, and how these two together obey the Einstein Field Equations. The solutions to the Einstein Field Equations (including the schwarzschild metric, kerr metric, freedman-lemaitre-robertson-walker metric, etc) represent gravity around massive objects like the sun, earth, and black holes, but also the history and expansion and future evolution of the cosmos. The universe on a large scale is described by general relativity - on a small scale, quantum mechanics. And where they meet... there's still work to be done.
REFERENCES
Wald's textbook - General Relativity
Hartle's textbook - Gravity: An Introduction to Einstein's General Relativity
Carlo Rovelli History of Quantum Gravity: https://cds.cern.ch/record/442809/files/0006061.pdf
Leon Rosenfeld 1930 paper on quantum gravity: http://www.edoc.mpg.de/438547
Kerr Metric Solution - en.wikipedia.org/wiki/Eddington%E2%80%93Finkelstein_coordinates
Schwarzschild Metric - en.wikipedia.org/wiki/Schwarzschild_metric
Eddington-Finkelstein Coordinates - en.wikipedia.org/wiki/Eddington%E2%80%93Finkelstein_coordinates
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video written & produced in collaboration with Aatish Bhatia, aatishb.com
This video is about how cheap, fast, and LESS sensitive rapid antigen tests might be better for screening (& maybe surveillance) than PCR COVID tests due to the nature of contagiousness/infectiveness at various points on the viral load trajectory of symptomatic and asymptomatic COVID sars-COV-2 carriers.
REFERENCES
Thanks to Daniel Larremore for feedback on early versions of this video larremorelab.github.io
Rapid Antigen Testing:
COVID-19 testing: One size does not fit all. science.sciencemag.org/content/371/6525/126
Rethinking Covid-19 Test Sensitivity — A Strategy for Containment. nejm.org/doi/full/10.1056/NEJMp2025631
Test sensitivity is secondary to frequency and turnaround time for COVID-19 screening. advances.sciencemag.org/content/7/1/eabd5393.abstract
The effectiveness of population-wide, rapid antigen test based screening in reducing SARS-CoV-2 infection prevalence in Slovakia. (pre-print, not yet peer reviewed) medrxiv.org/content/10.1101/2020.12.02.20240648v1
Effective Testing and Screening for Covid-19. rockefellerfoundation.org/wp-content/uploads/2020/09/A-National-Decision-Point-Effective-Testing-Screening-for-Covid-19-Full-Report.pdf
Brown University & Harvard University modeling of COVID-19 testing shortfall. globalepidemics.org/testing-targets
Fast Coronavirus Tests are coming. media.nature.com/original/magazine-assets/d41586-020-02661-2/d41586-020-02661-2.pdf
Open letter signed by epidemiologists and infectious disease experts supporting widespread & frequent rapid antigen testing for COVID-19: rapidtests.org/expert-letter
More information on various COVID-19 tests: https://chs.asu.edu/diagnostics-commons/testing-commons
Field performance and public health response using the BinaxNOW Rapid SARS-CoV-2 antigen detection assay during community-based testing. academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa1890/6052342
Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses. cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm
Asymptomatic Spread:
People without symptoms spread virus in more than half of cases, CDC model finds washingtonpost.com/science/2021/01/07/covid-asymptomatic-spread
(More than half of all) SARS-CoV-2 Transmission From People Without COVID-19 Symptoms. jamanetwork.com/journals/jamanetworkopen/fullarticle/2774707
Three Quarters of People with SARS-CoV-2 Infection are Asymptomatic: Analysis of English Household Survey Data. ncbi.nlm.nih.gov/pmc/articles/PMC7549754
Viral Load Curve:
SARS-CoV-2 viral dynamics in acute infections. (pre-print, not yet peer reviewed)
medrxiv.org/content/10.1101/2020.10.21.20217042v2
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Created by Henry Reich
Check out aatishb.com/maskmath to explore and for references.
This video is about how masks (whether surgical, or N95, or cloth) are counterintuitive and actually work much better epidemiologically than one might expect. Masks do double-duty, and the fraction of interactions with masks is much higher than the fraction of people wearing masks, so partially adopted, partially effective masks are able to reduce the basic reproduction number surprisingly well.
REFERENCES:
Aatish’s detailed writeup on github: github.com/aatishb/maskmath/blob/master/model/mathmodel.ipynb
Amid the Coronavirus Crisis, a Regimen for Re-entry: newyorker.com/science/medical-dispatch/amid-the-coronavirus-crisis-a-regimen-for-reentry
Face Masks Against COVID-19: An Evidence Review preprints.org/manuscript/202004.0203/v3
Mask FAQ Test Results: maskfaq.com/test-results
The Effect of Mask Use on the Spread of Influenza During a Pandemic: onlinelibrary.wiley.com/doi/full/10.1111/j.1539-6924.2010.01428.x
Calibrated Intervention and Containment of the COVID-19 Pandemic: arxiv.org/ftp/arxiv/papers/2003/2003.07353.pdf
Cloth Mask Breathability and Filtration Efficiency Technical Report: static1.squarespace.com/static/5e8126f89327941b9453eeef/t/5f2c4463a5c9f75a38d2b26f/1596736614213/N95DECON_cloth_mask_breathability_filtrationtechnical_report_v1_200804.pdf
What kind of mask should I be wearing to protect against COVID-19? http://built-envi.com/what-kind-of-mask-should-i-be-wearing-to-protect-against-covid-19
Masks for all? The science says yes. fast.ai/2020/04/13/masks-summary
The Real Reason to Wear a Mask: medium.com/the-atlantic/the-real-reason-to-wear-a-mask-e6405abbc484
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
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This video was written in collaboration with Aatish Bhatia - aatishb.com
To learn more about using & decontaminating N95 masks: n95decon.org
Thanks to Manu Prakash for useful discussion and feedback (Manu is involved with the N95 decontamination project)
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The physics & engineering of N95 mask design is pretty incredible.
REFERENCES
10X efficiency of electrically charged fibers
"The electrostatic charge of N95 masks is a major contributor to their filtration efficiency, improving it at least 10-fold over uncharged fabric" (Tsai et al., Journal of Electrostatics 2002; Peter Tsai, personal communication).
Prakash Lab COVID-19 Response Group Working Draft Document on N95 masks: docs.google.com/document/d/1aACcbkyZjR7nZy_wWeGQ9U2iGy0y4QajBeOL8RqAZIQ/edit
“Electrostatic charge contributes as much as 95% of the filtration efficiency”
Molina, A., Vyas, P., Khlystov, N., Kumar, S., Kothari, A., Deriso, D., ... & Prakash, M. (2020). Project 1000 x 1000: Centrifugal melt spinning for distributed manufacturing of N95 filtering facepiece respirators. arXiv preprint arXiv:2004.13494. arxiv.org/pdf/2004.13494.pdf
Tsai, P. P., Schreuder-Gibson, H., & Gibson, P. (2002). Different electrostatic methods for making electret filters. Journal of electrostatics, 54(3-4), 333-341. researchgate.net/profile/Phillip_Gibson/publication/222659741_Different_electrostatic_methods_for_making_electret_filters/links/5a5912cba6fdcc3bfb5ab21e/Different-electrostatic-methods-for-making-electret-filters.pdf
History of Electrets
Jefimenko, O. D., & Walker, D. K. (1980). Electrets. The Physics Teacher, 18(9), 651-659. aapt.scitation.org/doi/abs/10.1119/1.2340651
Physics of Air Filtration
Hinds, W. C. (1999). Aerosol technology: properties, behavior, and measurement of airborne particles. John Wiley & Sons. wiley.com/en-us/Aerosol+Technology%3A+Properties%2C+Behavior%2C+and+Measurement+of+Airborne+Particles%2C+2nd+Edition-p-9780471194101
Scientific consortium for data-driven study of N95: n95decon.org
N95 & virus particle sizes
Bałazy, A., Toivola, M., Adhikari, A., Sivasubramani, S. K., Reponen, T., & Grinshpun, S. A. (2006). Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks?. American journal of infection control, 34(2), 51-57. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.488.4644&rep=rep1&type=pdf
Harnish, D. A., Heimbuch, B. K., Husband, M., Lumley, A. E., Kinney, K., Shaffer, R. E., & Wander, J. D. (2013). Challenge of N95 filtering facepiece respirators with viable H1N1 influenza aerosols. Infection Control & Hospital Epidemiology, 34(5), 494-499. ncbi.nlm.nih.gov/pmc/articles/PMC4646082
Liao, L., Xiao, W., Zhao, M., Yu, X., Wang, H., Wang, Q., ... & Cui, Y. (2020). "Can N95 respirators be reused after disinfection? How many times?. ACS nano. ncbi.nlm.nih.gov/pmc/articles/PMC7202248
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Go to http://aatishb.com/covidtrends to explore the graph from the video yourself!
RESOURCES
Grant's 3Blue1Brown Video: Exponential Growth and Epidemics: youtube.com/watch?v=Kas0tIxDvrg
Aatish's Exponential/Logistic Curve-Fitting Site: github.com/aatishb/covid/blob/master/curvefit.ipynb
Data Source: github.com/CSSEGISandData/COVID-19
Our World in Data Page on Coronavirus: ourworldindata.org/coronavirus
How many tests for COVID-19 are being performed around the world? ourworldindata.org/covid-testing
Understanding logarithmic scales: nytimes.com/2020/03/20/health/coronavirus-data-logarithm-chart.html
What we can learn from the countries winning the coronavirus fight: https://www.abc.net.au/news/2020-03-26/coronavirus-covid19-global-spread-data-explained/12089028
(Great explainer on log scales and growth curves explained in the context of COVID-19 in different countries)
This video is a collaboration with Aatish Bhatia about how to see the COVID-19 tipping point - we present a better way to graph COVID-19 coronavirus cases using a logarithmic scale in "phase space" - plotting the growth rate against the cumulative cases, rather than either of these against time.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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This video is about the Ozma problem of distinguishing the chirality (ie left-handedness or right-handedness) of matter using weak interaction processes like beta decay (for example in uranium), or neutral kaon/k-meson decay. This is wrapped up in the phenomenon of CP violation, by which charge and parity are both violated by certain weak interaction processes - this enables antimatter to be unambiguously distinguished from matter, and left handed chirality from right handed.
REFERENCES
The Ozma Search for Extraterrestrial Intelligence (SETI) Project
seti.org/seti-institute/project/details/early-seti-project-ozma-arecibo-message
Sean Carroll on CP Symmetry (& why we shouldn’t trot out baryogenesis all the time)
preposterousuniverse.com/blog/2010/06/04/marketing-cp-violation
Electroweak CP Violation on Scholarpedia
http://www.scholarpedia.org/article/CPviolationinelectroweakinteractions
The Wu Experiment
en.wikipedia.org/wiki/Wuexperiment
Martin Gardner, The New Ambidextrous Universe
books.google.com/books?id=kdLGa8cPPUC&lpg=PP1&pg=PR2#v=onepage&q&f=false
Lecture notes on CP Violation and the CKM Matrix, Cambridge (Mark Thomson)
hep.phy.cam.ac.uk/thomson/lectures/partIIIparticles/Handout122009.pdf
Homochirality
en.wikipedia.org/wiki/Homochirality
L-glucose (vs D-glucose)
en.wikipedia.org/wiki/L-Glucose
Radioactive Nucleus Decay
http://www.radioactivity.eu.com/site/pages/RadioactiveSeries.htm
CP Violation in Semi-Leptonic Decays (SEE PAGE 426 for reference to definition of MATTER)
hep.phy.cam.ac.uk/thomson/lectures/partIIIparticles/Handout122009.pdf
Kaon Decay Modes
http://pdg.lbl.gov/2012/listings/rpp2012-list-K-zero-L.pdf
Flipped bowling Jesus scene in Big Lebowski
youtube.com/watch?v=lWz8NGIisMo
Isotopes of Uranium
en.wikipedia.org/wiki/Isotopesofuranium
Beta Decay
en.wikipedia.org/wiki/Betadecay
The Wu Experiment
en.wikipedia.org/wiki/Wuexperiment
Kaons
en.wikipedia.org/wiki/Kaon
CP Violation in Symmetry Magazine
symmetrymagazine.org/article/charge-parity-violation
Physics Stack Exchange on CP Violation
physics.stackexchange.com/questions/160511/what-cp-violating-processes-do-we-know-of
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about cutting, taping, and rearranging the periodic table into the Left Step form, the Mendeleev's flower form, the cake form, the wide form, the standard form, and so on. A great holiday craft!!
REFERENCES
Alternate Periodic Tables
en.wikipedia.org/wiki/Alternative_periodic_tables
Electronegativity
en.wikipedia.org/wiki/Electronegativity
Atomic Radius Radii
en.wikipedia.org/wiki/Atomic_radius
First Ionization energy
en.wikipedia.org/wiki/Ionization_energy
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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This video is about why words flip left & right (aka horizontally) in a mirror but not up & down (aka vertically). The answer has to do with specular reflection, mirrors being like windows into another world (alternate universes, just with in and out flipped!), and transparency of the things we write on.
REFERENCES
Specular Reflection
en.wikipedia.org/wiki/Specular_reflection
PhysicsGirl video about mirrors
youtube.com/watch?v=vBpxhfBlVLU
Fermat’s principle
http://electron6.phys.utk.edu/optics421/modules/m1/Fermat's%20principle.htm
Thomas-Fermi screening
en.wikipedia.org/wiki/Thomas%E2%80%93Fermi_screening
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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This video is about two-photon (gamma-gamma) physics, and how photons can interact with each other - either mediated by a passing lepton, or gravitationally via lensing, or via vacuum fluctuation pair production of vertical particles (electron-positron pair, for example). This is the so-called "box diagram" feynman diagram.
REFERENCES
Water waves interact with each other (weakly nonlinear shallow water waves)
en.wikipedia.org/wiki/Korteweg%E2%80%93deVriesequation
http://mathworld.wolfram.com/Korteweg-deVriesEquation.html
Paper: Absorption of Very High Energy Gamma Rays in the Milky Way
arxiv.org/pdf/1608.01587.pdf
Paper: Observing light-by-light scattering at the Large Hadron Collider (LHC)
arxiv.org/pdf/1305.7142.pdf
Mass-Energy Scale
http://labs.minutelabs.io/Mass-Energy-Scale
Optical Depth
en.wikipedia.org/wiki/Opticaldepth
The electromagnetic spectrum and photon energies
http://labman.phys.utk.edu/phys222core/modules/m6/The%20EM%20spectrum.html
Gravitational Lensing
http://andybohn.com/research/lensing.html
Ask an Astrophysicist on gamma ray scattering and energies in cosmology
http://teacherlink.ed.usu.edu/tlnasa/reference/imaginedvd/files/imagine/docs/askastro/answers/970412e.html
Measuring Vacuum Polarisation with High Power Lasers
arxiv.org/pdf/1510.08456.pdf
Detecting vacuum birefringence with X-ray free electron lasers and high-power optical lasers
https://indico.desy.de/indico/event/12654/session/2/contribution/8/material/slides/0.pdf
Vacuum birefringence in the head-on collision of XFEL and optical high-intensity laser pulses
arxiv.org/pdf/1807.03302.pdf
ATLAS makes first direct detection of Light-by-light scattering at the LHC
https://atlas.cern/updates/press-statement/atlas-sees-first-direct-evidence-light-light-scattering-high-energy
Two Photon Physics
http://www.hep.ucl.ac.uk/opal/gammagamma/gg-tutorial.html
en.wikipedia.org/wiki/Two-photonphysics
Thesis: The Opacity of the Universe for high and very high energy γ-rays
http://inspirehep.net/record/1254304/files/desy-thesis-13-033.pdf
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This video is about how Russian physicist Aleksandr Fridman corrected Albert Einstein about the expansion of the universe. Einstein thought that general relativity implied that space had to be static and unchanging, but he had made a technical error regarding the differentiation of the metric (in particular, I believe he mistook the determinant of the metric for a scalar rather than a tensor density of weight 2). Friedmann didn't make this differential geometric mistake, and the cosmologies he found from the Einstein Equations were more varied in their properties - they could be expanding, or contracting, or (with the cosmological constant), static.
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REFERENCES
Alexander Friedmann
en.wikipedia.org/wiki/Alexander_Friedmann
Einstein Wrongly Criticizes Alexander Friedmann
https://einsteinpapers.press.princeton.edu/vol13-trans/301
Alexander Friedmann Corrects Einstein
https://einsteinpapers.press.princeton.edu/vol13-trans/363
Einstein Admits his Mathematical Mistake
https://einsteinpapers.press.princeton.edu/vol14-trans/77
Interrogating the Legend of Einstein’s “Biggest Blunder”
arxiv.org/abs/1804.06768
Cosmological Considerations in the General Theory of Relativity
https://einsteinpapers.press.princeton.edu/vol6-trans/433
On the General Theory of Relativity (Einstein)
https://einsteinpapers.press.princeton.edu/vol6-trans/110
The Field Equations of Gravitation
https://einsteinpapers.press.princeton.edu/vol6-trans/129
The Einstein Field Equations
en.wikipedia.org/wiki/Einstein_field_equations
Presentation about the Sequence of Events
http://web.mit.edu/8.286/www/slides07/Einstein-and-Friedmann.pdf
Tensor Densities:
en.wikipedia.org/wiki/Tensor_density
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Watch the main video here: youtube.com/watch?v=pT19VwBAqKA
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REFERENCES
Cynthia Dwork (key inventor of Differential Privacy), giving a great intro talk about differential privacy
youtube.com/watch?v=lg-VhHlztqo
Hazards of Smoking: the Effect on Life Span
nejm.org/doi/pdf/10.1056/NEJMsa1211128
NHL Hockey Birth distributions
quanthockey.com/nhl/birth-month-totals/nhl-players-career-stats.html
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
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REFERENCES
Differential Privacy in the Wild: http://www.vldb.org/pvldb/vol9/p1611-machanavajjhala.pdf
Harvard University Privacy Tools Project: https://privacytools.seas.harvard.edu/differential-privacy
Simons Institute Workshop Video Recordings and Articles Archive: https://simons.berkeley.edu/workshops/schedule/6281
Cynthia Dwork (key inventor of Differential Privacy), giving a great intro talk about differential privacy: youtube.com/watch?v=lg-VhHlztqo
Shiva P Kasiviswanathan and Adam Smith. On the semantics of differential privacy: A Bayesian formulation. Journal of Privacy and Confidentiality, 6(1):1–16, 2014.
Shiva Prasad Kasiviswanathan and Adam Smith. On the ‘semantics’ of differential privacy: A Bayesian formulation. 2015. https://arxiv.org/abs/0803.3946
Daniel Kifer and Ashwin Machanavajjhala. A rigorous and customizable framework for privacy. In ACM Symposium on Principles of Database Systems (PODS), 2012.
Daniel Kifer and Ashwin Machanavajjhala. Pufferfish: A framework for mathematical privacy definitions. ACM Trans. Database Syst., 39(1):3, 2014.
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The world's most entertaining and useless self-help guide, from the brilliant mind behind the wildly popular webcomic xkcd and the #1 New York Times bestsellers What If? and Thing Explainer
For any task you might want to do, there's a right way, a wrong way, and a way so monumentally complex, excessive, and inadvisable that no one would ever try it. How To is a guide to the third kind of approach. It's full of highly impractical advice for everything from landing a plane to digging a hole.
Bestselling author and cartoonist Randall Munroe explains how to predict the weather by analyzing the pixels of your Facebook photos. He teaches you how to tell if you're a baby boomer or a 90's kid by measuring the radioactivity of your teeth. He offers tips for taking a selfie with a telescope, crossing a river by boiling it, and powering your house by destroying the fabric of space-time. And if you want to get rid of the book once you're done with it, he walks you through your options for proper disposal, including dissolving it in the ocean, converting it to a vapor, using tectonic plates to subduct it into the Earth's mantle, or launching it into the Sun.
By exploring the most complicated ways to do simple tasks, Munroe doesn't just make things difficult for himself and his readers. As he did so brilliantly in What If?, Munroe invites us to explore the most absurd reaches of the possible. Full of clever infographics and amusing illustrations, How To is a delightfully mind-bending way to better understand the science and technology underlying the things we do every day.
REFERENCES
How To (Randall Munroe) - see above for links!
Rock melting points
http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/meltrock.html
Syracuse University Researchers Make Lava Using Keweenawan Basalt
http://lavaproject.syr.edu/making-lava/making.html
BEDROCK GEOLOGY OF WISCONSIN MAP: UNIVERSITY OF WISCONSIN–EXTENSION Geological and Natural History Survey
Electric Furnace
amazon.com/Automatic-Electric-Refining-Precious-Aluminum/dp/B07LCKKFWX
Large Geothermal Power Plants
worldatlas.com/articles/largest-geothermal-power-plants-in-the-world.html
calpine.com/operations/power-operations/our-locations/california/ridge-line
Coal Power Plant Capacity
talenenergy.com/plant/colstrip
The size of an A19 or A21 Lightbulb
blog.1000bulbs.com/home/a21-vs-a19
Low melting point Vanadate glass
iopscience.iop.org/article/10.1143/JJAP.50.088002
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
It's super cool!! (and made by Jasper Palfree & the MinuteEarth/MinutePhysics team)
The MinutePhysics video about Why December Has the Longest Days: youtube.com/watch?v=nZMMuv0Ltyo
This video is about the length of a solar day vs a stellar day vs a mean standard day, what they all have to do with each other and the earth's orbit, eccentricity, axial tilt, and so on. Also, aliens and asteroids. It'll explain the equation of time, and why the longest day is in December. The lab will also show you what days are like on all the other planets - Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and even - though it's not a planet - Pluto.
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MinutePhysics is on twitter - @minutephysics
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about how Albert Einstein made a mistake when applying the Field Equations of General Relativity to cosmology (in particular, to a static, constant density universe), and solved the problem by introducing the cosmological constant, rather than allowing for a dynamic universe with a scale factor - that is, the Friedmann-Lemaitre-Robertson-Walker universe, first developed by Alexander Friedmann of Russia. Later, it was discovered by the Slipher and Hubble red-shift that the universe is indeed expanding, and even later, by Schwarz and company in 1998, that the expansion is accelerating - aka, dark energy. And the cosmological constant was re-introduced.
Thanks to Grant Sanderson of http://www.youtube.com/3Blue1Brown for help with the fancy equation animation!
REFERENCES
The Einstein Field Equations
en.wikipedia.org/wiki/Einstein_field_equations
Interrogating the Legend of Einstein’s “Biggest Blunder”
arxiv.org/abs/1804.06768
On the General Theory of Relativity (Einstein)
https://einsteinpapers.press.princeton.edu/vol6-trans/110
The Foundation of the General Theory of Relativity (Albert Einstein)
https://einsteinpapers.press.princeton.edu/vol6-trans/158
Cosmological Considerations in the General Theory of Relativity
https://einsteinpapers.press.princeton.edu/vol6-trans/433
Einstein Wrongly Criticizes Alexander Friedmann
https://einsteinpapers.press.princeton.edu/vol13-trans/301
Alexander Friedmann Corrects Einstein
https://einsteinpapers.press.princeton.edu/vol13-trans/363
Einstein Admits his Mathematical Mistake
https://einsteinpapers.press.princeton.edu/vol14-trans/77
The Field Equations of Gravitation
https://einsteinpapers.press.princeton.edu/vol6-trans/129
George Gamow
en.wikipedia.org/wiki/George_Gamow
Mach’s Principle
en.wikipedia.org/wiki/Mach%27s_principle
Equivalence Principle
en.wikipedia.org/wiki/Equivalence_principle
Sean Carroll and William Press Paper
preposterousuniverse.com/wp-content/uploads/cpt92.pdf
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MinutePhysics is on twitter - @minutephysics
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about the Portal Paradox - a paradox in the video game Portal (and Portal 2) regarding whether or not a companion cube passing through a moving portal plops out of the other end with no speed (velocity, momentum), or shoots out at high speed. It’s a question of conservation of momentum, relativity of velocities, wormholes, 3D printers and quantum teleportation, glitches, and more.
REFERENCES
Conservation of momentum
en.wikipedia.org/wiki/Momentum#Conservation_in_a_continuum
Principle of Locality
en.wikipedia.org/wiki/Principle_of_locality
YouTube video of testing the Portal 2 game engine on the portal Paradox youtu.be/S85nudR6D-Y
Tutorial for how to program the Portal portals on your own: gamasutra.com/view/feature/132164/games_demystified_portal.php
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
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MinutePhysics is on twitter - @minutephysics
And facebook - http://facebook.com/minutephysics
And Google+ (does anyone use this any more?) - http://bit.ly/qzEwc6
Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
This video is about how little we know about the behavior of gravity at short length and distance scales, what the constraints are on the inverse square law/Newton's law of universal gravitation, at the human and microscopic and atomic scales. Only on solar system scales or larger do we have good constraints on Newton's law of gravitation.
REFERENCES
Review of short-range gravity experiments in the LHC era
arxiv.org/abs/1408.3588v2
Zeptonewton force sensing with nanospheres in an optical lattice
arxiv.org/abs/1603.02122
Large extra dimensions
en.wikipedia.org/wiki/Large_extra_dimension
Search for Screened Interactions Associated with Dark Energy Below the 100 μm Length Scale
arxiv.org/abs/1604.04908
Tests of the Gravitational Inverse-Square Law below the Dark-Energy Length Scale
arxiv.org/abs/hep-ph/0611184v1
Photon Mass Experiment
http://dx.doi.org/10.1119/1.13149
Torsion balance experiments: A low-energy frontier of particle physics
E.G. Adelberger, J.H. Gundlach, B.R. Heckel, S. Hoedl, S. Schlamminger
doi:10.1016/j.ppnp.2008.08.002
TESTS OF THE GRAVITATIONAL INVERSE-SQUARE LAW
E.G. Adelberger, B.R. Heckel, and A.E. Nelson
Annu. Rev. Nucl. Part. Sci. 2003. 53:77–121 doi: 10.1146/annurev.nucl.53.041002.110503
Physical Review A, Vol 33, No 1: Improved result for the accuracy of Coulomb's law: A review of the Williams, Faller, and Hill experiment.
Lewis P. Fulcher.
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
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MinutePhysics is on twitter - @minutephysics
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
This video is about how I designed and made my own custom mute guitar pedal for my clip-on mic and piezo pickup on my violin (fiddle). The mic is an AT Pro35 phantom powered XLR condensor microphone, and the pickup is a Fishman V200 piezoelectric transducer. I got all of the parts from PartsExpress.
Thanks to my band (youtube.com/channel/UCEKRoVVSZKGih6v_xK4LAdw), Caleb, Pete, Paul and Troy, and to Hannah for filming.
Link to Patreon Supporters: http://www.minutephysics.com/supporters
REFERENCES:
Gearslutz mute wiring for phantom powered vs dynamic/line-level microphones:
gearslutz.com/board/geekslutz-forum/813680-how-wire-external-xlr-off-switch-pedal.html
Beavis Audio Research:
http://beavisaudio.com/techpages
Pickups on wikipedia: en.wikipedia.org/wiki/Pickup_%28music_technology%29
Microphone mute pedal on “I like to make stuff”
iliketomakestuff.com/make-microphone-mute-pedal
Balanced vs unbalanced audio:
http://www.aviom.com/blog/balanced-vs-unbalanced
Balanced signals on wikipedia:
en.wikipedia.org/wiki/Balanced_audio
Phantom Power:
http://acousticguitar.com/everything-you-need-to-know-about-microphone-phantom-power
Phantom Power explained on Sweetwater:
sweetwater.com/insync/how-phantom-power-works
Piezoelectricity:
en.wikipedia.org/wiki/Piezoelectricity#Mechanism
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Watch the main video: youtube.com/watch?v=lvTqbM5Dq4Q
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
This video explains how Shor’s Algorithm factors the pseudoprime number 314191 into its prime factors using a quantum computer. The quantum computation relies on the number-theoretic analysis of the factoring problem via modular arithmetic mod N (where N is the number to be factored), and finding the order or period of a random coprime number mod N. The exponential speedup comes in part from the use of the quantum fast fourier transform which achieves interference among frequencies that are not related to the period (period-finding is the goal of the QFT FFT).
REFERENCES
RSA Numbers (sample large numbers to try factoring)
en.wikipedia.org/wiki/RSA_numbers
IBM on RSA ibm.com/support/knowledgecenter/en/SSB23S1.1.0.13/gtps7/s7pkey.html
Modulo Multiplication Group Tables http://mathworld.wolfram.com/ModuloMultiplicationGroup.html
Difference of squares factorization en.wikipedia.org/wiki/Difference_of_two_squares
Euclid’s Algorithm en.wikipedia.org/wiki/Euclideanalgorithm
Rational sieve for factoring en.wikipedia.org/wiki/Rational_sieve
General Number field Sieve en.wikipedia.org/wiki/Generalnumberfieldsieve
Scott Aaronson blog post about Shor’s Algorithm scottaaronson.com/blog/?p=208
Experimental implementation of Shor’s Algorithm (factoring 15, 21, and 35) arxiv.org/pdf/1903.00768.pdf
Adiabatic Quantum Computation factoring the number 291311 arxiv.org/pdf/1706.08061.pdf
Scott Aaronson course notes scottaaronson.com/qclec scottaaronson.com/qclec/combined.pdf
Shor’s Algorithm on Quantiki quantiki.org/wiki/shors-factoring-algorithm
TLS And SSL use RSA encryption en.wikipedia.org/wiki/TransportLayerSecurity
Dashlane security whitepaper dashlane.com/download/DashlaneSecurityWhitePaperOctober2018.pdf
Link to Patreon Supporters: http://www.minutephysics.com/supporters
MinutePhysics is on twitter - @minutephysics
And facebook - http://facebook.com/minutephysics
Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
This video explains Shor’s Algorithm, a way to efficiently factor large pseudoprime integers into their prime factors using a quantum computer. The quantum computation relies on the number-theoretic analysis of the factoring problem via modular arithmetic mod N (where N is the number to be factored), and finding the order or period of a random coprime number mod N. The exponential speedup comes in part from the use of the quantum fast fourier transform which achieves interference among frequencies that are not related to the period (period-finding is the goal of the QFT FFT).
REFERENCES
RSA Numbers (sample large numbers to try factoring)
en.wikipedia.org/wiki/RSA_numbers
IBM on RSA
ibm.com/support/knowledgecenter/en/SSB23S1.1.0.13/gtps7/s7pkey.html
Modulo Multiplication Group Tables
http://mathworld.wolfram.com/ModuloMultiplicationGroup.html
Difference of squares factorization
en.wikipedia.org/wiki/Difference_of_two_squares
Euclid’s Algorithm
en.wikipedia.org/wiki/Euclideanalgorithm
Rational sieve for factoring
en.wikipedia.org/wiki/Rational_sieve
General Number field Sieve
en.wikipedia.org/wiki/Generalnumberfieldsieve
Scott Aaronson blog post about Shor’s Algorithm
scottaaronson.com/blog/?p=208
Experimental implementation of Shor’s Algorithm (factoring 15, 21, and 35)
arxiv.org/pdf/1903.00768.pdf
Adiabatic Quantum Computation factoring the number 291311
arxiv.org/pdf/1706.08061.pdf
Scott Aaronson course notes
scottaaronson.com/qclec
scottaaronson.com/qclec/combined.pdf
Shor’s Algorithm on Quantiki
quantiki.org/wiki/shors-factoring-algorithm
TLS And SSL use RSA encryption
en.wikipedia.org/wiki/TransportLayerSecurity
Dashlane security whitepaper
dashlane.com/download/DashlaneSecurityWhitePaperOctober2018.pdf
Link to Patreon Supporters: http://www.minutephysics.com/supporters
MinutePhysics is on twitter - @minutephysics
And facebook - http://facebook.com/minutephysics
Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
Link to Patreon Supporters: http://www.minutephysics.com/supporters
This video is about compressed air cans (aka gas dusters) and why they get cold when you spray them. They cool off because the refrigerant inside (1,1-difluoroethane) is under pressure and boils off when the pressure lowers, and energy lost to the latent heat of vaporization cools the can a lot. Difluoroethane normally boils at -25°C (-13°F), but under ~6 atm (6 bar, 600 kpa) it is a liquid at room temperature. The gas also cools off slightly due to the Joule-Thompson effect of fluid expansion through a throttled valve. Difluoroethane is heavier than air and water soluble, so it is recommended to use it in a ventilated environment to clean your keyboard, etc. Also, 1,1-difluoroethane is a potent greenhouse gas. It is also known as Freon 152a, Ethylidene difluoride, Ethylidene fluoride, HFC-152a, R-152a, and DFE.
Thanks to Tino and Hannah!
REFERENCES
CRC Air Duster Safety Data Sheet
http://docs.crcindustries.com/msds/5185.pdf
Latent Heat of vaporization
en.wikipedia.org/wiki/Latentheat
1,1-difluoroethane chemical and physical properties
webbook.nist.gov/cgi/cbook.cgi?ID=C75376&Mask=3FFF
1,1-difluoroethane on wikipedia
en.wikipedia.org/wiki/1,1-Difluoroethane
Free Expansion of Real Gases, Goussard, 1993
http://dx.doi.org/10.1119/1.17417
Joule-Thompson Expansion Course Notes
http://tccc.iesl.forth.gr/education/local/Labs-PC-II/JT.pdf
Properties of 1,1-difluoroethane
http://www.inchem.org/documents/sids/sids/75376.pdf
pubchem.ncbi.nlm.nih.gov/compound/11-difluoroethane
Medical Effects of difluoroethane
toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+5205
MinutePhysics is on twitter - @minutephysics
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich