It's like the sound of silence... only louder
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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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https://www.youtube.com/watch?v=qyi5SvPlMXc
Thanks to http://www.audible.com/minutephysics for supporting this video, which is about how the way we describe the world can influence the way we perceive it. In particular, with regards to Bohmian mechanics, Schrodinger wave functions, Feynman path integrals, and Galilean moons attached to Jupiter by springs.
Thanks to everyone who supports MinutePhysics on Patreon!
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REFERENCES:
Scans of Galileo’s notes:
http://www.dioi.org/galileo/scans.pdf
Scans of Galileo’s publication: http://www.chlt.org/sandbox/lhl/GalileoSkel1610/page.41.a.php?size=240x320
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https://www.youtube.com/watch?v=lHaX9asEXIo
To keep your brain sharp with quick daily math & science puzzles, head to http://www.brilliant.org/minutephysics
This video is about how to create muons in a particle accelerator via bombardment of heavy nuclei with protons, which results in creation of charged pions (plus and minus). The pions then decay into muons and mu neutrinos, and the muons then decay into electrons or positrons and more neutrinos. Muons also form in the upper atmosphere due to cosmic rays, and the uses of muons includes experimental tests of time dilation in special relativity, catalyzing muonic cold nuclear fusion, and more.
Muons on wikipedia: https://en.wikipedia.org/wiki/Muon
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
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MinutePhysics is on twitter - @minutephysics
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https://www.youtube.com/watch?v=zBr9YiSwdzM
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
AMAZING Interactive Entropy explainer by Aatish Bhatia: http://aatishb.github.io/entropy/
This video is about why entropy gives rise to the arrow of time, and also how the initial low-entropy condition of the universe is responsible for the fact that we experience time right now, and how ultimately it will lead to the high-entropy heat death of the universe.
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https://www.youtube.com/watch?v=yKbJ9leUNDE
Time Dilation - boosting 5 seconds to fill 10 seconds since 1905
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!
Music by Nathaniel Schroeder http://www.soundcloud.com/drschroeder
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https://www.youtube.com/watch?v=Q__r6eIT7Go
This video is about how life arose and what its main function or purpose in the universe seems to be. Thanks to http://www.audible.com/minutephysics for supporting this video, and to Sean Carroll for collaborating on it!
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 life arose and what its main function or purpose in the universe seems to be. Throughout the universe there is a driving tendency for entropy to increase and free energy to be used up; however, sometimes there is some sort of barrier holding back further potential increase in entropy - these entropically favored but not directly possible reactions (like hydrogen nuclei fusing to become helium, or carbon dioxide reacting with hydrogen to form methane and water), *can* be achieved by larger systems, often complex or complicated, that allow multi-step reaction chains that ultimately lead to the entropically favored state. These systems, (stars, whose nuclei foster conditions amenable to fusion of hydrogen into helium, and life, which fosters conditions amenable to hydrogenating carbon dioxide) are naturally entropically favored, once they arise. And thus the purpose of both life, and stars, can be seen, in the context of the universe, as being a catalyst system that helps facilitate increases in entropy that are not otherwise possible.
Music for the series was especially composed by Nathaniel Schroeder, http://www.soundcloud.com/drschroeder
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https://www.youtube.com/watch?v=HxTnqKuNygE
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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?
Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
Link to Patreon Supporters: http://www.minutephysics.com/supporters/
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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
https://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 (https://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
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https://www.youtube.com/watch?v=VkNF0rXuDXw
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!
Music by Nathaniel Schroeder http://www.soundcloud.com/drschroeder
Thanks to Nima Doroud for contributions. Created by Henry Reich
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https://www.youtube.com/watch?v=oJGFei3wKs4
Concrete doesn’t dry - it sets!
Thanks to http://www.audible.com/minutephysics for supporting this video.
More about the hydration reaction: http://iti.northwestern.edu/cement/monograph/Monograph5_3.html
Portland Cement Hydration: http://people.ce.gatech.edu/~kk92/hyd07.pdf
Calcium Silicate Hydrate: https://en.wikipedia.org/wiki/Calcium_silicate_hydrate
How concrete gets stronger and cures over time: https://courses.washington.edu/cm425/strength.pdf
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https://www.youtube.com/watch?v=2qegAzbrI1U