I've created an educational product to help people learn chemistry!
You can buy it here: http://www.snatoms.com

In the mid 1800's scientists successfully passed an electric current through a vacuum in a glass tube. They saw a glow from the tube that seemed to emanate from the negatively charged plate called the cathode. Since scientists didn't know what the glow was they called it a cathode ray. There was debate over whether the cathode ray was a wave phenomenon like light or a stream of negatively charged particles. JJ Thomson effectively resolved the debate in 1897 by performing a clever experiment that determined the charge to mass ratio of the particles making up the cathode ray. He also showed that this same particle was in all different cathode materials so it must be a constituent common to all atoms. This changed our understanding of the atom from the previous billiard ball model to Thomson's plum pudding model of the atom.

The total solar eclipse from Madras, Oregon on August 21, 2017. As the moon passed in front of the sun turning day to night and revealing the sun's corona, apparently all I could think to say was 'Oh my goodness!'

Special thanks to Patreon Supporters:
Nathan Hansen, Donal Botkin, Ron Neal, Zach Mueller, Jeff Straathof, Curational, Tony Fadell

Everyone says not to photograph your first solar eclipse and I think they might be right. I was focused on getting the exposure right for Bailey's beads and the diamond ring, plus making sure to get the corona and solar flares. This was a bit stressful but I'm delighted with the results.

This video originally included more info but since I'm uploading from Madras where the internet is sluggish, I cut out three minutes so the upload would happen before I had to leave for my flight.

Special thanks also to Dr. Teagan Wall for sharing this experience with me and Raquel Nuno for inspiring me to come to Oregon.

Music from http://epidemicsound.com "Spinning Earth 2" and
Kevin MacLeod http://incompetech.com "Big Mojo"

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"

UV cameras expose a hidden world and reveal the incompleteness of our perception
The Physics Girl looks at sunscreen: https://youtu.be/GRD-xvlhGMc
How to make sunscreen from scratch: https://youtu.be/lMXAY5F28L0

In summary, ultraviolet light interacts differently with matter for a number of reasons:
1. Some pigments selectively absorb UV so they may appear white in the visible but dark in the UV. The pigments usually dissipate the UV energy as heat, though the breaking of bonds can also occur.
2. Fluorescent molecules absorb UV light and re-radiate that energy as visible light. This makes them look dark in the UV but glowing under black light.
3. Ultraviolet light scatters more than visible light because the wavelength is shorter and Raleigh scattering is proportional to the reciprocal of wavelength to the power of four.

Special thanks to HHMI BioInteractive for their awesome animations of melanocytes and how the melanin in melanosomes protect your DNA. To see the full video explaining how we get our skin color, check out: https://www.youtube.com/watch?v=VC0TL_lYLm8

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

References:

Overview of main UV effects:
Visualizing Rayleigh Scattering through UV Photography
https://journals.ametsoc.org/d....oi/pdf/10.1175/BAMS-

Arctic animals are photographed in the UV to increase visibility and get an accurate count:
Lavigne, D. (1976). Counting Harp Seals with ultra-violet photography. Polar Record, 18(114), 269-277. doi:10.1017/S0032247400000310

Absorption spectrum of melanin: http://www.cl.cam.ac.uk/~jgd1000/melanin.html

"The spectroscopy of human melanin pigmentation," by N. Kollias. In: Melanin: Its Role in Human Photoprotection, pp. 31 - 38. Valdenmar Publishing Co. (1995).

"Optical properties of human sclera, and their consequences for transscleral laser applications," by A. Vogel, C. Dlugos, and R. Nuffer, Lasers in Surgery and Medicine 11(4), pp. 331 - 340 (1991).

"The incidence and time-course of latanoprost-induced iridial pigmentation as a function of eye color," by P. Wistrand, J. Stjernschantz, and K. Olsson, Survey of Ophthalmology 41(S2), pp. S129 - S138 (1997).

Music by Epidemic Sound: https://www.epidemicsound.com "Spring Moods 5"

Mars InSight will be the first to detect seismic activity on Mars’ surface, first to measure rate of heat transmitted from interior, first to dig nearly 5m down, first to measure magnetic fields on Mars’ surface, and first to use a robotic arm to place instruments on the surface of Mars (assuming it lands of course…)

If you want to watch the InSight landing “live” (with 4-minute speed of light time delay), go to: https://ve42.co/insight

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

Animations courtesy of NASA

Script and Filming with Raquel Nuno

Editing and graphics by Ignat Berbeci

Answer video: https://www.youtube.com/watch?v=BickMFHAZR0
The longest vertical straw you can use is 10.3 m http://www.youtube.com/watch?v=HUmZrtiXDik
This is because the weight of water in the straw must be supported by the pressure difference at its two ends. At the bottom, the pressure is atmospheric, and at the top, the lowest pressure you can create is a perfect vacuum (pressure = 0). Atmospheric pressure can support a water column about 10m high - BUT with 0 pressure at the top, the water would start boiling. This is called cavitation and it obviously can't be happening in trees.
After I posted the straw video, I received a lot of questions about how trees could be taler than 10m. I assumed there was a simple answer because there are plenty of trees taller than that. But as I asked around and read articles about it, I couldn't really find an explanation I was happy with.

Maybe there is not a continuous water column inside the tree, so each section only lifts water a little ways? This could be but it seems to require a series of pump mechanisms, and how would you join this pump sections together? Perhaps capillary action is holding the water up? But the xylem tubes in a tree seem too wide (~50 um) for this effect to be significant. Maybe osmotic pressure could push the water from below rather than sucking it up from above? But some trees live in mangroves, where there is much higher solute concentration in the sea water than in their roots, so osmosis would work the other way.

Eventually I spoke to a plant biologist and sorted this all out, but I wanted to give you a little back to school challenge. How do you think this could work?

On the surface of Earth all objects accelerate downwards at the same rate - at least, they're supposed to. But we all know dust, pieces of paper, and feathers fall slower. This is of course due to the influence of air resistance. In this experiment we use an evacuated cylinder to test whether a coin and feather really do accelerate at the same rate.

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.

There are a few persistent misconceptions about what causes the seasons. Most believe it is the distance between the Earth and sun which varies to give us seasonal temperature variations. However it is actually the directness of the sun's rays leading to more intense sunshine in summer and less in winter.

Countries are powered by a diverse range of energy sources, but in Australia electricity generation mainly has one source: fossil fuels. Coal, natural gas, and oil account for over 90% of the country's electricity. Hydro provides 7% with only 0.3% provided by wind and solar. Should Australia consider nuclear power? It is a complicated issue leaving many uncertain about its place in Australia's energy future.

In 2020, NASA will send a new rover to the Martian surface with one of its objectives to search for evidence of ancient life on the planet. I made this clip as a correspondent for Bill Nye Saves the World on Netflix.

Touring the Jet Propulsion Lab (JPL) in Pasadena was an awesome experience. I didn't think we were going to get into the control room but we got lucky. Some of the greatest moments in the history of space exploration have taken place there. They have a giant vacuum chamber where they can take the rover down to the atmospheric pressure on Mars (roughly .01x Earth's atmosphere) and test all of the devices to make sure there are no electrical discharges due to the reduced pressure. I also enjoyed seeing how the rocks will be cored and stored in tubes and deposited on the Martian surface awaiting pickup by the following mission.

Images courtesy of NASA.

Filmed by Raquel Nuno from 3:30 onwards.

Music: http://epidemicsound.com "Serene Story 2"

Vitamins are 13 molecules essential for life that our bodies can't make themselves.
Watch Vitamania here: https://ve42.co/vita

Now available worldwide, except France and Germany where it will be broadcast on ARTE soon. Subscribe on the Vitamania website for updates.

Use #vitamania to join the conversation on Twitter and Facebook.

Vitamania is a Genepool Productions feature documentary for SBS Australia, CuriosityStream, and ARTE France. Principal production investment from Screen Australia, in association with Film Victoria.

What happens when a super long slinky is dropped?

What was the procedure to launch a nuclear missile?
Uranium premieres: July 28 & 29 on PBS at 10pm ET/ 9pm Central
France and Germany: July 31 at 10pm on ZDF/arte
Norway: August 5 & 6 at 21:30 on NRK2
Australia: August 9, 16, 23 at 8:30pm on SBS
Sweden: TBD
Middle East: TBD

For more information on other screenings go to
https://www.facebook.com/uraniumtwistingthedragon
www.genepoolproductions.com

A big thank you to The Titan Missile Museum, Yvonne and Chuck.
http://www.titanmissilemuseum.org/

Space footage courtesy of NASA

To see what this looks like from under a glass table, see http://www.youtube.com/watch?v=E9WUaBGH7_I

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

1, 2, 3 A song about 'lectricity
because it powers our lives
makes it possible for us to thrive

because it powers our lives
makes it possible for us to thrive

Oh, 4, 5, 6, volts of potential difference
makes electrons go round
if the circuit is complete and sound

Circuit's closed
Voltage There
Current Flows
Power Everywhere

We use AC,
in factories
and homes because we can transform it
High voltage
transmits with lower loss
but low voltage is best for safety
I said what is electricity?

Well, so 1,2,3 a song about 'lectricty
because it powers our lives
makes it possible for us to thrive

because it powers our lives
makes it possible for us to thrive

Oh, 4,5,6 volts of potential difference
makes electrons go round if the circuit is complete and sound

Heat makes steam
turns turbines
and a magnet in
coils of wires

We use AC,
in factories
and homes because we can transform it
High voltage
transmits with lower loss
but low voltage is best for safety
I said what is electricity?

Oh yeah, Oh yeah, C'mon!
How'd it be
no energy
of the electrical persuasion
I know we'd
have no computers
no internet or mobile phones yeah
Powers the world
Makes the world
We need electricity yeah

More about the Alaska Trip: http://education.projectaether.org

Channel 10 Breakfast: http://www.tenbreakfast.com.au (6-9am weekdays in Australia)

March 26 segment on live TV talking about solar storms and my upcoming trip to the Great White North. As you watch this I will probably be on a plane high over the pacific.
PS a student recently told me that my hair to beard ratio is a bit off and watching this clip I tend to agree. However, it is still -20 C at night in Alaska so I'll need all the insulation I can get.

Right: https://www.youtube.com/watch?v=AS9OXzSRBMQ
Left: http://www.youtube.com/watch?v=FWQ-HJ4oGKQ
It Depends: https://www.youtube.com/watch?v=R3GHiMOHEy8
What happens when nylon rope is wound around a spool and pulled horizontally to the right? Will the spool go to the right, to the left, or does it depend on how the rope is pulled?