Tag: physics

Full Video: https://www.youtube.com/watch?v=lR4tJr7sMPM
You may have heard that Einstein’s theory of special relativity imposes a cosmic speed limit: nothing can travel faster than the speed of light. Well, that’s wrong.
All that Einstein said was that light moves at the same speed in every reference frame – and while this implies that nothing with real mass can move faster than light, it doesn’t impose a cosmic speed limit.
Because you can break the speed of light in your backyard. All you have to do is point a laser beam at the moon and flick your wrist. The spot of light from the laser beam will travel across the moon’s face in about half a millisecond, which means it’s traveling at twenty times the speed of light!
How is this possible? Well, think about a computer screen – what’s the speed limit for pixels on the screen? Zero. Pixels can’t move.
But if you cleverly arrange a whole bunch of pixels to turn on and off in a special way, you can make an image that appears to move across the screen, even though every pixel stays put. So you’ve broken the speed of pixels!
The laser pointer on the moon is basically the same – each photon travels to the moon at the speed of light, but the image of a dot that they form on the surface moves twenty times faster! No physical laws are broken because nothing physical is actually traveling faster than light – it’s just an image.

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 we don’t just need energy to power our lives, we need *low entropy* energy! Thanks to Google Making and Science for supporting this series, and to Sean Carroll for collaborating on it! His book can be found here: http://www.penguinrandomhouse.com/books/316646/the-big-picture-by-sean-carroll/

Playlist of the full video series: https://www.youtube.com/playlist?list=PLoaVOjvkzQtyZF-2VpJrxPz7bxK_p1Dd2

Link to Patreon supporters here: http://www.minutephysics.com/supporters.html

This video is about how we don’t just need energy to power our lives, we need *low entropy* energy! This is also known as “free energy”, and one way of thinking about entropy is as the lack of free energy. The sun provides us with useful, low entropy, energy in the form of photons of visible light, which are then absorbed and converted into plants, sugar, complex molecules, etc, before being radiated back into space as heat, which has much higher entropy.

Music for the series was especially composed by Nathaniel Schroeder, http://www.soundcloud.com/drschroeder

REFERENCES & ADDITIONAL INFORMATION

Entropy Balance of Radiation of the Earth system http://www.sciencedirect.com/science/article/pii/0038092X9290097T

Heat balance of global warming/climate change: http://www.skepticalscience.com/4-Hiroshima-bombs-worth-of-heat-per-second.html

More on the Entropy Balance of the Earth System https://www.bnl.gov/envsci/pubs/pdf/2010/BNL-81482-2008-JA.pdf

The Entropy of a Photon Gas: https://en.wikipedia.org/wiki/Photon_gas

Sean’s blog: http://www.preposterousuniverse.com/blog/2016/05/11/big-picture-part-four-complexity/

Another article by Sean about complexity and god: https://www.preposterousuniverse.com/writings/dtung/

Sean Carroll: The Big Picture
(more great articles about entropy, etc on his blog http://preposterousuniverse.com)

Interactive Entropy explainer by Aatish Bhatia: http://aatishb.github.io/entropy/

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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

Go to https://brilliant.org/minutephysics to try everything Brilliant has to offer for free for a full 30 days, and also get 20% off your annual premium subscription!

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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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 bonus material cut from this video at https://nebula.tv/minutephysics

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

Footnote to the main video here: https://youtu.be/HUti6vGctQM

Feedback loops and spurious correlations!

REFERENCES:
Spurious correlations: http://www.tylervigen.com/spurious-correlations
Loopy by Nicky Case: http://ncase.me/loopy/
CERN/CMS paper on di-photon excess: https://cds.cern.ch/record/2139899

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

Full video: https://www.youtube.com/watch?v=1pfqIcSydgE
Chemistry may tell us the recipe for combustion, but the light show is all physics.
When a flame burns cleanly (like a gas flame, blowtorch or the base of a candle), the heat excites the molecules to release light (usually pale-blue) from atomic transitions.
That’s quantum mechanics!
Now when the fuel isn’t as pure and doesn’t entirely burn (like a wood fire or coal fire or the top of a candle flame), there’s still some blue light, but you don’t see it because
it’s overpowered by light from all the particles of soot & smoke – they’re glowing red-hot!

Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!

Created by Henry Reich

Full video: https://www.youtube.com/watch?v=IOYyCHGWJq4
I’m sure you’ve heard some version of this famous thought experiment: you put a cat in a bunker with some unstable gunpowder that has a 50% chance of blowing up in the next minute, and 50% chance of doing nothing.
So until we look in the bunker, we don’t know whether the cat is dead or alive, and when we do look, it is either dead or alive.
But if we repeat the experiment enough times with enough cats and bunkers and gunpowder, we’ll see that half the time kitty survives, and half the time kitty goes bye-bye.
The quantum mechanical interpretation is that before we look, the cat is in a superposition – it’s both dead AND alive – and our act of looking forces nature’s decision.
So our curiosity kills the cat.
But what about the cat’s perspective?
Well, the cat either sees the gunpowder explode, or not – so inside the bunker we actually have these two possibilities: “the powder exploded and the cat saw it explode” or “the powder didn’t explode and the cat didn’t see it explode”.
There’s no option: “the powder exploded and the cat didn’t see it explode” – so the cat’s reality becomes entangled with the outcome of the experiment!
And it’s our observation of the experiment that forces nature to “collapse” to one option or the other.

Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!
Created by Henry Reich

A reply to CGP Grey’s video about teleportation, consciousness and Star Trek. CGP Grey’s Transporter video: https://www.youtube.com/watch?v=nQHBAdShgYI

REFERENCES

Scott Aaronson on teleportation machines: http://www.scottaaronson.com/democritus/lec18.html

The original quantum teleportation paper: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.46.9405&rep=rep1&type=pdf

Link to Patreon supporters here: www.minutephysics.com/supporters.html

Music by Nathaniel Schroeder, http://www.soundcloud.com/drschroeder

MinutePhysics is on Google+ – http://bit.ly/qzEwc6
And facebook – http://facebook.com/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 Created by Henry Reich

This video is about weird condensed matter systems, aka materials that have bizarre emergent particles in them that are unlike most other particles in the universe.

Thanks to the Moore Foundation (http://www.moore.org) for supporting this video.

More info about the physics of weird materials:
The Higgs Boson – https://www.youtube.com/watch?v=9Uh5mTxRQcg

Semiconductor Holes – http://www.eecs.berkeley.edu/~hu/Chenming-Hu_ch1.pdf

Superconductors – https://en.wikipedia.org/wiki/Superconductivity

Quasiparticles – https://en.wikipedia.org/wiki/Quasiparticle

Heavy Fermions – https://en.wikipedia.org/wiki/Heavy_fermion

Link to Patreon supporters here: www.minutephysics.com/supporters.html

Music by Nathaniel Schroeder, http://www.soundcloud.com/drschroeder

MinutePhysics is on Google+ – http://bit.ly/qzEwc6
And facebook – http://facebook.com/minutephysics
And 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

Thanks to Brilliant.org for supporting MinutePhysics – the first 200 people to go to http://www.brilliant.org/minutephysics will get 20% off of a premium subscription to all of Brilliant’s courses and puzzles.

Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
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This video is about the original cold fusion: μ muon-catalyzed cold fusion of deuterium, tritium, hydrogen, into helium-3 and helium 4. The problems with it are the half-life of muons and the sticking of muons to alpha particles. Also involved are neutrons, protons, break-even, etc. This has nothing to do with fusion by capture in palladium electrodes.

REFERENCES:

The original papers: L.W. Alvarez 1957, F.C. Frank 1947, and J.D. Jackson 1957

A History of Muon Catalyzed “Cold” Fusion
http://large.stanford.edu/courses/2016/ph241/yoon1/

Fusion rates
http://www.kayelaby.npl.co.uk/atomic_and_nuclear_physics/4_7/4_7_4.html

Cold Fusion
https://en.wikipedia.org/wiki/Cold_fusion#Proposed_mechanisms

Muon Facilitated Fusion
https://en.wikipedia.org/wiki/Muon-catalyzed_fusion

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

Also, why do some flames look hollow? Thanks to http://www.audible.com/minutephysics for sponsoring this video.

More information about:

Limb darkening – https://en.wikipedia.org/wiki/Limb_darkening

Optical Depth – https://en.wikipedia.org/wiki/Optical_depth

Limb darkening – http://spiff.rit.edu/classes/phys440/lectures/limb/limb.html

Limb darkening and exoplanets – http://zuserver2.star.ucl.ac.uk/~idh/NewGrids/vLimb.pdf

Measuring the solar radius using limb darkening! – http://arxiv.org/pdf/1302.3469.pdf

Halo nebulas – http://blogs.discovermagazine.com/badastronomy/2010/12/16/a-delicately-violent-celestial-shell-game/

Link to Patreon supporters here: www.minutephysics.com/supporters.html

Music by Nathaniel Schroeder, http://www.soundcloud.com/drschroeder

MinutePhysics is on Google+ – http://bit.ly/qzEwc6
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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 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
https://math.stackexchange.com/questions/1329130/what-fraction-of-a-sphere-can-an-external-observer-see

Orbital period
https://en.wikipedia.org/wiki/Orbital_period

Kepler’s third law
https://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 mromega^2=Gfrac{mM}{r^2}, and using omega=frac{2pi}{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 Tto 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 Grho T^2=3pi, aka rho=frac{3pi}{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 rhoapprox 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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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