UV at ground level is non-ionizing but it damages DNA and causes photoaging - how?
Also, it turns out glass doesn't block all UV (specifically UVA passes through). This is something I learned filming with the UV camera inside.

Special thanks to Dr. Hayley Golbach, @hayleysgold on twitter
https://twitter.com/hayleysgold

Ultraviolet light causes damage to DNA, leads to cancer and photoaging: age spots and wrinkles. I was curious about this because UV is technically non-ionizing. A photon of UV doesn't have enough energy to strip an electron off atoms or molecules. However it does have enough energy to trigger photo-chemical reactions. For example, it causes pyrimidine dimers - the unauthorized covalent bonding of adjacent thymine or cytosine bases in our DNA. If these spots are not properly repaired, they may lead to mutations and cancer. Photoaging is typically the result of degradation of collagen and elastin fibers - scaffolding that supports the skin. This leads to wrinkles and saggy-looking skin.

Huge thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen, Yildiz Kabaran, Terrance Snow, Stan Presolski, James M Nicholson, KIMoFy

Support Veritasium on Patreon: http://ve42.co/patreon

Music from Epidemic Sound http://epidemicsound.com "Serene Story 2"

The kilogram, mole, kelvin, and ampere will be redefined by physical constants. For a limited time, get 3 months of Audible for just $6.95 a month: http://audible.com/VERITASIUM or text VERITASIUM to 500500

Will this be the last video I make about SI units? Quite possibly. There's something about being so precise and defining the systems within which science works. When we can more accurately and routinely measure a kilogram, a mole, a kelvin and an ampere, then we can make better observations, we can better detect anomalies and improve our theories. That is why this is so important to me.

Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Ron Neal, Nathan Hansen, James M Nicholson, Terrance Shepherd, Stan Presolski

Special thanks to NIST: http://nist.gov

Additional graphics by Ignat Berbeci

Music from http://epidemicsound.com "Experimental1"

Scientists like Prof Sinclair have evidence of speeding up, slowing, and even reversing aging.
Thanks to LastPass for sponsoring this video. Click here to start using LastPass: https://ve42.co/VeLP

What causes aging? According to Professor David Sinclair, it is a loss of information in our epigenome, the system of proteins like histones and chemical markers like methylation that turn on and off genes. Epigenetics allow different cell types to perform their specific functions - they are what differentiate a brain cell from a skin cell. Our DNA is constantly getting broken, by cosmic rays, UV radiation, free radicals, x-rays and regular cell division etc. When our cells repair that damage, the epigenome is not perfectly reset. And hence over time, noise accumulates in our epigenome. Our cells no longer perform their functions well.

To counter this decline, we can activate the body's own defenses against aging by stressing the body. Eat less, eat less protein, engage in intense exercise, experience uncomfortable cold. When the body senses existential threats it triggers longevity genes, which attempt to maintain the body to ensure its survival until good times return. This may be the evolutionary legacy of early bacteria, which established these two modes of living (repair and protect vs grow and reproduce). Scientists are uncovering ways to mimic stresses on the body without the discomfort of fasting. Molecules like NMN also trigger sirtuins to monitor and repair the epigenome. This may slow aging.

Reversing aging requires an epigenetic reset, which may be possible using Yamanaka factors. These four factors can revert an adult cell into a pluripotent stem cell. Prof. Sinclair used three of the four factors to reverse aging in the retinal cells of old mice. He found they could see again after the treatment.

Special thanks to:
Professor David Sinclair, check out his book "Lifespan: Why We Age & Why We Don't Have To"
Assistant Professor David Gold
Noemie Sierra (for polyp images)
Genepool Productions for telomere animations from Immortal: https://ve42.co/immortal
Epigenetics animations (DNA, histones, methylation etc) courtesy of: http://wehi.tv
Animation: Etsuko Uno
Art and Technical Direction: Drew Berry
Sound Design: Francois Tetaz & Emma Bortignon
Scientific Consultation: Marnie Blewitt
Courtesy of Walter and Eliza Hall Institute of Medical Research

Filming, editing and animation by Jonny Hyman and Derek Muller

Music from https://epidemicsound.com "Clearer Views" "Innovations" "A Sound Foundation" "Seaweed"
Additional music by Kevin MacLeod from https://incompetech.com "Marty Gots a Plan"

This is what a nuclear disaster area looks like.
Check out Audible: http://bit.ly/AudibleVe
Broadcast locations and times:

North America: PBS, July 28 & 29 @ 10pm ET / 9pm Central
Europe: ZDF/arte, July 31 @ 10pm
Australia: SBS, August 6, 13, 20 @ 8:30pm EST

Not broadcast in your country? Contact your local broadcaster and/or email www.genepoolproductions.com

Music by Kevin Macleod http://incompetech.com 'Come Play With Me' & 'Lost Frontier'

*Watch with headphones on!
Is 45 minutes really the longest anyone can stay in a perfectly silent, pitch-black room?
Support Veritasium on Patreon http://bit.ly/VePatreon
Check out Audible: http://bit.ly/AudibleVe
Want to watch the whole hour of silence? http://youtu.be/jr1UMFC9DV0

Many stories have circulated claiming the longest anyone has stayed in an ultra-quiet anechoic chamber is 45 minutes, the reason being any longer would drive you insane. To me this sounded like unsubstantiated rubbish, like the claim the Great Wall is the only manmade structure visible from space. So I put my own psyche on the line, subjecting myself to over an hour of the most intense quiet on Earth. No, this was not THE quietest room on Earth (-9dB) but it is one of the quietest, and the truth is once you put a person inside, they are by far the loudest thing in there so the sound rating of the room is irrelevant.

I was not surprised to find that I could stay in there for as long as I liked and feel perfectly fine. What was surprising is that my heartbeat was audible. You can hear it on the sound recording. Now I wasn't consciously aware of the sound of my heart while in the room, but I was more aware of the feeling of it beating.

Huge thank you to everyone at BYU: Duane Merrell, Spencer Perry, Cameron Vongsawad, Jazz Myers, Ann Clawson, and Robert Willes.

Can you solve these four rotation-related riddles?
Support Veritasium on Patreon: http://ve42.co/patreon
Test yourself playlist: http://ve42.co/testurself

Huge thanks to Patreon supporters:
Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen

I came across these four physics puzzles over the years in discussions with Neil deGrasse Tyson (riddle 4: which part(s) of a moving train are going backwards with respect to the ground?), Simon Pampena (riddle 2: run around a track twice, the first time slowly, the second time much faster so that the average for the two laps is twice the speed of the first lap). Someone tweeted me a video of the mystery cylinder rolling down the ramp in riddle 1 (sorry I'm not sure who it was). Riddle three about a bicycle going forward or backward when it's bottom peddle is pulled back was brought to me by a number of people and I appreciate all of their help!

Filmed by Raquel Nuno.
Thanks to everyone at the Palais de la Decouverte! I've had this footage for five years and am only finally releasing it now. I wanted to talk about the way grass grows on a spinning turntable but I couldn't locate the footage...

Want to help plant 20M trees by 2020? Go to https://teamtrees.org #teamtrees
Huge thanks to all the YouTubers who organized this. My apologies for the repost.
These videos are from 2012 so my interest in trees goes back a long ways. I think these videos discuss two of the most interesting and amazing facts about our leafy friends: they are made mostly of CO2 (which comes from us breathing out amongst other sources) and they can transport water up a tube higher than any we can currently manufacture. So trees are out to get you. But we do much worse to them so we owe it to them to plant some more. 20 mil is a good start.

One of the most common physics misconceptions is that an unbalanced force causes constant motion. In truth, an unbalanced force leads to changes in motion - accelerations.

Can you predict what happens to the golf ball?
Stays where it is: http://bit.ly/buoyStay
Goes down: http://bit.ly/buoyGoDown
Goes up: http://bit.ly/buoyGoUp

In this experiment we see that a golf ball is denser than detergent (it is also denser than pure water incidentally, which is why water hazards are so effective at ruining a golfer's day on the course). But, a golf ball is less dense than a saturated salt solution. Now the question is: if you pour the detergent on top of the golf ball in the salt solution, what will happen to the golf ball?

Special thanks to Duane Merrell for the idea, which I saw demonstrated at BYU back in February. Thanks to Emil Malmsten for excellent filming, and his Stockholm colleagues who were game to have a chat to me about this experiment.

Droplets levitate on a bath of liquid nitrogen and are spontaneously self-propelled. Thanks Audible! Start a 30-day trial and your first audiobook is free. Go to https://audible.com/VERITASIUM or text VERITASIUM to 500500.

Special thanks to Dr. Anaïs Gauthier
Physics of Fluids: https://pof.tnw.utwente.nl/

Self-propulsion of inverse Leidenfrost drops on a cryogenic bath
Anaïs Gauthier, Christian Diddens, Rémi Proville, Detlef Lohse, and Devaraj van der Meer
PNAS January 22, 2019 116 (4) 1174-1179; published ahead of print January 22, 2019
https://www.pnas.org/content/116/4/1174

For a detailed description of the setup:
http://www.lps.ens.fr/~adda/pa....piers/Langmuir2016.p

And self-propulsion is also seen: http://www.lps.ens.fr/~adda/pa....piers/InvLeidenfrost

Other recent (hot) Leidenfrost experiments that might be interesting:
* Leidenfrost wheels: https://www.youtube.com/watch?v=glRGl-eYuXo
* Leidenfrost maze: https://www.youtube.com/watch?time_continue=174&v=vPZ7sx3EwUY
* Leidenfrost explosions: https://www.youtube.com/watch?v=z0sp3AjgUy4

Special thanks to Patreon supporters:
Donal Botkin, James M Nicholson, Michael Krugman, Nathan Hansen, Ron Neal, Stan Presolski, Terrance Shepherd

Thanks to Prof. Kevin McKeegan at UCLA for the liquid nitrogen

Filming by Raquel Nuno

Additional animations by Alan Chamberlain

A recent survey of scientific literacy in Australia found 30% believe it takes one day for the Earth to go around the sun. This video provides qualitative evidence for the finding from Sydney's Eastern beaches.

A bisected grape in the microwave makes plasma. But how does it work? A grape is the right size and refractive index to trap microwaves inside it. When you place two (or two halves) close together the fields interact with each other creating a maximum of electromagnetic energy where they touch. This creates heating, sparks, and plasma, which is further fed with energy directly by the microwaves.

Huge thanks to Hamza Khattak, Prof. Pablo Bianucci and Prof. Aaron Slepkov (unavailable for the call) for chatting to me and helping me understand the physics of this cool phenomenon.

Linking plasma formation in grapes to microwave resonances of aqueous dimers
https://www.pnas.org/cgi/doi/1....0.1073/pnas.18183501

Special thanks to Patreon supporters:
Donal Botkin, James M Nicholson, Michael Krugman, Nathan Hansen, Ron Neal, Stan Presolski, Terrance Shepherd

Thanks also to Steve Bosi, my original plasma collaborator.

Animations by Alan Chamberlain

Music from http://epidemicsound.com "Seaweed"

Students at UCF are designing an inexpensive 3D printed arm for kids.
To find out more and to get involved, check out: http://office.tumblr.com

Big thanks to Microsoft and the Collective Project for introducing me to Albert and his amazing team. They are continuing to help people around the world one hand at a time and they could use your help.
Learn more and see how you can get involved by checking out The Collective Project on Tumblr, follow @MSONeNote on Twitter or head over to http://Onenote.com/collectiveproject

In April 2012, I was part of a team of scientists, teachers and students who travelled to Alaska to observe the Northern Lights or Aurora Borealis. Our mission was a unique one - to launch weather balloons up to 100,000 feet loaded with experiments, tracking devices and HD cameras. This is the result of our trip, produced for Catalyst on ABC1 http://www.abc.net.au/catalyst/

My hypothesis is that the algorithm, rather than viewer preference, drives views on the site. As the algorithm shifts, various YouTubers experience burnout (as what used to work no longer works) and right now click-through rate is the key metric. So clickable titles and thumbnails are the only way to get a lot of impressions and hence views - they are the only way to go viral. This leads me to wonder which audiences will become most prevalent on the site and if there will even be a place for educational content. In the long-term, hopefully YouTube is able to measure satisfaction through surveys and other metrics to ensure an optimal experience for everyone on the site.

Flipchart artwork by Maria Raykova
Filmed by Raquel Nuno
Thumbnail by Ignat Berbeci

Negative Pressure Exists! http://bit.ly/TFilQ8
Vsauce's Space Straw: http://bit.ly/XubIm3
Smarter Every Day's Prince Rupert's Drop: http://bit.ly/10VQBGW
ViHart's Optimal Potatoes: http://bit.ly/14egJoe

Thanks to Questacon for filming! Check out their slow-mo playlist: http://bit.ly/ZoWFGR
Science Alert brings science to your news feed: http://on.fb.me/14ehuxA

Music by Kevin Mcleod (http://incompetech.com): Pale Rider & The Cannery

Mosquitoes are attracted to me and it's likely due to my genes.
This video is sponsored by 23andMe https://23andme.com/veritasium
Huge thanks to Prof. Immo Hansen and team: http://ve42.co/hansen

References:
Genome Wide Association Study for self-reported mosquito attractiveness:
http://ve42.co/MossieGWAS

The twin study showing correlated attractiveness is stronger for identical twins:
http://ve42.co/MossieTwins

Some things we know make mosquitoes more attracted to you:
Exercising, higher metabolism, higher body temperature, more body odor, being pregnant, type O blood, infrequent bathing, lactic acid, ammonia, acetone.

There are a number of folk remedies people believe protect them from mosquito bites like drinking alcohol, eating garlic, or taking vitamin B. These do not appear to provide any benefit in lab studies and in fact drinking alcohol is associated with increased mosquito activity because it causes blood vessels near the surface of the skin to dilate.

And apparently some of your attractiveness to mosquitos is simply genetic. This may be mediated through your immune system, which is what a lot of the genes identified were associated with.

Molecular models are microSnatoms: http://snatoms.com

Filming in New Mexico by Raquel Nuno
Animations by Jacqui Robertson

The opinions and conclusions drawn in this video are those of Veritasium and not 23andMe.

We put aerogel to the test vs 'not-a-flamethrower', a huge 2000°C flame to a large fiberglass blanket infused with silica aerogel - formerly the lightest solid (that title is now held by graphene aerogel).

Special thanks to:
Aerogel Technologies: https://ve42.co/aerogeltech
Aspen Aerogels: https://ve42.co/aspen
Ben: @BenScho999999
Dr. Stephen Steiner and the Aerogel Technologies team

The footage of aerogel materials in cold environments was provided courtesy of Aspen Aerogels. Their product, cryogel, was shown to be flexible in liquid nitrogen while preventing cold burns to the hand. They are the manufacturer of the blanket used in the main portion of this video.

This is the finale of my three-part series on aerogel. I'll put links to the other parts below:
World's Lightest Solid: https://youtu.be/AeJ9q45PfD0
I Waterproofed Myself With Aerogel: https://youtu.be/GcdB5bFwio4

Huge thanks to Patreon supporters:
Alfred Wallace, Arjun Chakroborty, Bryan Baker, Chris Vargas, Chuck Lauer Vose, Dale Horne, Donal Botkin, Eric Velazquez, halyoav, James Knight, Jasper Xin, Joar Wandborg, Kevin Beavers, kkm, Leah Howard, Lyvann Ferrusca, Michael Krugman, Mohammed Al Sahaf, Noel Braganza, Philipp Volgger, Pindex, Ron Neal, Sam Lutfi, Stan Presolski, Tige Thorman

This is an educational video demonstrating scientific experiments performed by professionals. It should not be attempted by viewers.

Music from Epidemic Sound: http://epidemicsound.com "Running Against the Clock" "Dangerous Forests"

I am nearing the end of a 6-week road trip filming for an Australian TV show called Catalyst (http://abc.net.au/catalyst). Along with co-presenters Anja and Simon, I have travelled from Perth towards our destination, Melbourne, picking up all the interesting science stories along the way.

Since we have been working long days I haven't had time to make any new Veritasium material. Instead I thought I'd share some things I have done for this show in the past, including narrating short 'factoid' segments like this one. Hope everyone is having a great holiday season and I look forward to getting back to Veritasium stuff in a few weeks.

Nuclear Fungus
Producer: Nicky Ruscoe
Researcher: Kiri Beilby
Editor: Chris Spur
Graphics: Rapt Animation P/L

http://abc.net.au/catalyst

How should we depict an atom? Like a solar system with electrons orbiting the nucleus on hula hoop orbits? That idea is so last century! Bosi takes us into the quantum world, where an electron's position and velocity aren't well defined - all we can calculate are the probabilities e.g. of finding an electron at different points in space. When we do that, we find electrons do not neccessarily occupy circles or spheres in space. Rather their probability densities make all sorts of interesting shapes from the dumbell to the peanut with the donut around it.