"Ó Senhor, Deus dos Exércitos, quem é semelhante a ti? És poderoso, Senhor, envolto em tua fidelidade." (Salmos 89:8)

"O LORD God of hosts, who {is} a strong LORD like unto thee? or to thy faithfulness round about thee?" (Psalms 89:8)

"耶 和 華 ─ 萬 軍 之 　 神 啊 ， 哪 一 個 大 能 者 像 你 耶 和 華 ？ 你 的 信 實 是 在 你 的 四 圍 。" （詩篇89:8）

"يا رب اله الجنود من مثلك قوي رب وحقك من حولك‎." (مزمور 89:8)

여호와 만군의 하나님이여, 주와 같이 능한 자 누구리이까 여호와여, 주의 성실하심이 주를 둘렀나이다 (시편 89:8)

The world's roundest object helps solve the longest running problem in measurement -- how to define the kilogram.
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A kilogram isn't what it used to be. Literally. The original name for it was the 'grave', proposed in 1793 but it fell victim to the French Revolution like its creator, Lavoisier. So begins the tale of the most unusual SI unit. The kilogram is the only base unit with a prefix in its name, and the only one still defined by a physical artifact, the international prototype kilogram or IPK.

But the problem with this definition has long been apparent. The IPK doesn't seem to maintain its mass compared to 40 similar cylinders minted at the same time. The goal is therefore to eliminate the kilogram's dependence on a physical object. Two main approaches are being considered to achieve this end: the Avogadro Project and the Watt Balance.

The Avogadro project aims to redefine Avogadro's constant (currently defined by the kilogram -- the number of atoms in 12 g of carbon-12) and reverse the relationship so that the kilogram is precisely specified by Avogadro's constant. This method required creating the most perfect sphere on Earth. It is made out of a single crystal of silicon 28 atoms. By carefully measuring the diameter, the volume can be precisely specified. Since the atom spacing of silicon is well known, the number of atoms in a sphere can be accurately calculated. This allows for a very precise determination of Avogadro's constant.

Special thanks to Katie Green, Dr. David Farrant, the CSIRO, and the National Measurment Institute for their help. Thanks also to Nessy Hill for filming and reviewing earlier drafts of this video.

There is debate as to whether this is truly the roundest object ever created. The Gravity Probe-B rotors are also spherical with very low tolerances such that they may in fact be rounder.

Music by Kevin McLeod (incompetech.com) Decision, Danse Macabre, Scissors

Check out 2Veritasium! http://dft.ba/-ve2
MinutePhysics has a great video on Milkman, vomiting levitator: http://dft.ba/-vomphysics
Jetpacking was awesome fun! Despite the fat lip I had a great time. I think knowing a bit about physics actually helps fly the jetpack. It works on the same principle as a rocket (Newton's 3rd law) but unlike the shuttle, you don't carry your own propellant with you. Instead, water is pumped out of the lake by the jetski at up to 60 litres a second. It is then fired out of the nozzles at around 15 m/s creating 1800 N of force, the equivalent of about 150 fire extinguishers. On me this can produce acceleration of about 1.5g's.

Music by Kevin McLeod (http://incompetech.com) Silly Fun, Also Sprach Zarathustra
Supported by Science Alert: http://on.fb.me/14ehuxA
Slow motion filming by Questacon: http://bit.ly/ZoWFGR

My PhD: http://www.physics.usyd.edu.au..../super/theses/PhD(Mu
It is a common view that "if only someone could break this down and explain it clearly enough, more students would understand." Khan Academy is a great example of this approach with its clear, concise videos on science. However it is debatable whether they really work. Research has shown that these types of videos may be positively received by students. They feel like they are learning and become more confident in their answers, but tests reveal they haven't learned anything. The apparent reason for the discrepancy is misconceptions. Students have existing ideas about scientific phenomena before viewing a video. If the video presents scientific concepts in a clear, well illustrated way, students believe they are learning but they do not engage with the media on a deep enough level to realize that what was is presented differs from their prior knowledge. There is hope, however. Presenting students' common misconceptions in a video alongside the scientific concepts has been shown to increase learning by increasing the amount of mental effort students expend while watching it.

How Schlieren imaging works in color, black and white and slow-mo.
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Special thanks to Patreon supporters:
Tony Fadell, Donal Botkin, Curational, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen, Corvi

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

Filming by Raquel Nuno
Sound Effects by A Shell in the Pit

The Nobel Prize for physics in 2011 was awarded to Brian Schmidt, Adam Riess, and Saul Perlmutter for discovering that the universe is expanding at an accelerating rate. This finding was completely unexpected because it was thought that gravity should slow the expansion of the cosmos. The best current explanation of why the universe is accelerating is that there is some energy tied to empty space which pushes matter apart. This 'Dark Energy' makes up 73% of the universe but is very difficult to detect. Hopefully a better understanding of it will lead to a unification of our theories of gravitation and quantum mechanics.

Images courtesy of NASA - NASAimages.org

I used a nitrogen membrane and Stirling cryocooler to liquefy nitrogen out of the air. For this video I partnered with Starbucks to celebrate their Nitro Cold Brew. Order one here: https://starbucks.app.link/derekmuller

Making liquid nitrogen is hard - in fact up until 150 years ago scientists doubted whether it was even possible to liquefy nitrogen. In 1823, At the royal institution in London, Michael Faraday first produced liquid chlorine, kind of accidentally by putting it under high pressure. He similarly liquefied ammonia.

Borrowing a mixture from Thilorier in France, a combination of dry ice, snow and ether, he reached a temperature of -110C. By 1845 he used this mixture plus a hand pump to pressurize gases to liquefy all the known gases except six, which included oxygen and nitrogen. These became known as the “permanent” gases.

A French Physicist Aimé compressed oxygen and nitrogen in tanks and then lowered them into the ocean over 1.6km deep, where the pressure got up to 200 atmospheres. Still the gases didn’t liquefy.

Only at the end of 1877 were the first droplets of liquid oxygen and liquid nitrogen produced, by Cailletet in France. He first tried oxygen by compressing it up to 300 atmospheres, cooled to -30C, but that wasn't even enough to liquefy oxygen. But when he suddenly released the pressure, the expanding gas cooled, he estimated to -200C and he saw a mist and then droplets slide down the walls of his vessel.

It's amazing how far we've come in that now I can purchase a helium-based cryocooler. It compresses and expands the gas to absorb heat from the tip of the cold finger and eject it into the surroundings at ambient temperature.

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?

On a mobile device? Click here: http://www.youtube.com/watch?v=X-QFAB0gEtE for the answer
Two 1.5kg masses are released simultaneously from the top of a 10m high wall. One is attached to a chain while the other is free. Which one will hit the ground first?

Get ready for liftoff to the Sun! ?

Solar Orbiter, a collaboration between European Space Agency and NASA, is launching Sunday, Feb. 9, to study the inner workings of our nearest star. Tune in for launch coverage starting at 10:30 p.m. on Sunday, Feb. 9 to see liftoff, currently targeted for 11:03 p.m. EST.

More info: https://go.nasa.gov/2SiKpNn

This year, NASA is building momentum across the agency and across every mission. This is a year of action. With each milestone, NASA is preparing to go farther than ever before.
NASA is going to the Moon and on to Mars, in a measured, sustainable way. Working with U.S. companies and international partners, NASA will push the boundaries of human exploration forward to the Moon. NASA is working to establish a permanent human presence on the Moon within the next decade to uncover new scientific discoveries and lay the foundation for private companies to build a lunar economy. We inspire generations and change the course of history as we realize the next great scientific, economic and technical achievements in space.


This video is available for download from NASA's Image and Video Library: https://images.nasa.gov/detail....s-NHQ_2020_0210_NASA

Aboard the International Space Station, Expedition 62 Flight Engineer Jessica Meir of NASA discussed the revolutionary Zero-G oven recently used on the orbital outpost during an in-flight question and answer session Feb. 19 with students from the East Middle School in Grand Blanc, Michigan. The oven was launched on a Northrop Grumman Cygnus cargo ship last November, and, along with cookies baked in the oven, was returned to Earth in January on a SpaceX/Dragon resupply vehicle.

On Monday, Jan. 20 starting at 6:50 a.m. EST, NASA astronauts Jessica Meir and Christina Koch will step outside of the International Space Station into the vacuum of space together. The duo will wrap up the work of installing new lithium-ion batteries to upgrade the orbiting lab’s power systems. The spacewalk is scheduled to last about six-and-a-half hours.

Band:
Mike X. Zuniga- (MD)Bass
Aldo Juarez- Drums
Chris Rocha- Guitar
Robert Prado- Guitar
William ''Willie'' Garcia- Keys
Jamie Arroyo- Keys