A pulsing black hole in the centre of a distant galaxy sheds light on black hole and galaxy formation. How fast are black holes rotating and how does that rotation change over its life-span?

Huge thanks to Prof. Geraint Lewis and study author Dr. Dheeraj Pasham.

A loud quasi-periodic oscillation after a star is disrupted
by a massive black hole
https://ve42.co/pasham

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

Music from http://epidemicsound.com "Colorful animation 4" "serene story 2" "To the stars 01" "Black Vortex

Animations by Alan Chamberlain and courtesy of NASA

Epigenetics means women have different active x-chromosomes in different cells. Animation courtesy of http://wehi.tv
Music by Amarante: http://bit.ly/VeAmarante
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: http://wehi.tv

When a female embryo is four days old it consists of just 100 cells. At this point the x-chromosome from Mom and the one from Dad are both active. But in order for proper development to occur, one of the x chromosomes must be switched off.

Through a tiny molecular battle within each cell, one of the x-chromosomes wins and remains active while the loser is deactivated.

This is done by wrapping the DNA tighter around proteins, modifying histone tails, and DNA methylation - molecular markers to indicate this DNA should not be read.

What's surprising is that it's pretty random which x chromosome wins - sometimes it's Mom's and sometimes it's Dad's. So when a female is just 100 cells big, her cells have a mix of active x-chromosomes, some from Mom and some from Dad.

Huge thanks to the Royal Institution, Professor Frank James, and Katie Atmore for filming.
For the Sixty Symbols version of this experiment click http://bit.ly/RGfLY5

Michael Faraday created the first electric generator in 1831 using a coil of wire and a permanent magnet. When the magnet was moved relative to the coil, current was induced in the coil. A similar experiment can be performed with a copper tube and a magnet. Although copper is not magnetic, it is a conductor. As the magnet falls through the pipe, the magnetic field changes over different sections of the pipe. This induces swirling currents (called eddy currents), which create a magetic field that opposes the motion of the magnet. This means work must be done to move the magnet through the pipe. This work generates the electrical energy, which is then dissipated as thermal energy in the pipe. The same basic principle is used to generate electricity throughout the world: moving a magnet inside copper coils.

Experiments A Cappella http://bit.ly/TtdflV
Where Did The Earth Come From http://bit.ly/VQBzQJ
The Coastline Paradox http://bit.ly/TIapxM
Microwave Grape Plasma http://bit.ly/QkCwUt


Music by Kevin McLeod (http://www.incompetech.com) Sneaky Snitch and Danse Macabre

Complete unedited interviews: http://www.youtube.com/watch?v=8dcw98B2Nzg
Trees can weigh hundreds or even thousands of tons, but where do they get this mass from? A few common answers are: the soil, water, and sunlight. But the truth is the vast majority of a dry tree's mass comes from the air - it originated as carbon dioxide

Is punishment or reward more effective as feedback? Do new medical treatments really work? What about streaks in sport? Without considering regression to the mean, we are prone to making significant errors.

Check out Audible.com: http://bit.ly/ZJ5Q6z
Filmed at Perimeter Institute: http://pitp.ca

Is punishment or reward more effective for helping people learn. A lot of people would say different incentives motivate different people, or in different circumstances, but in psychology there is a sizable body of evidence that in order to learn skills, positive feedback is more effective. This fining has been verified not just with humans, but also with other species.

It was strange then that after Daniel Kahneman discussed this research with Israeli fighter pilot instructors that he was met with resistance. They found the opposite was true: when they reprimanded a cadet for performing poorly, he invariably improved, but if they praised a cadet for an excellent performance, the next attempt was not as good. In order to solve this apparent contradiction we first need to understand regression to the mean.

Teacher study: http://bit.ly/1h8puVT
Rugby player study: http://bit.ly/1aNSrBI

Microwave grape plasma: http://www.youtube.com/watch?v=RwTjsRt0Fzo
Northern Lights: http://www.youtube.com/watch?v=knwiWm4DpvQ
Nanodiamonds in candle flames: http://www.youtube.com/watch?v=KzOkuGQC3Rw
Relight Candle Trick: http://www.youtube.com/watch?v=1tXPVTIisl0

Is a flame really a plasma? Well it depends on your definition of plasma, but there are certainly ions in a flame, formed as molecules collide with each other at high speed, sometimes knocking electrons off of their atoms.

Special thanks to the Palais de la Decouverte for helping me perform this experiment. Using tens of thousands of volts on two metal plates, we created a strong electric field around the plasma. This pulled positive ions in one direction and negative ions in the other direction elongating the flame horizontally and causing it to flicker like a "papillon" (butterfly). Then we showed that much longer sparks can be made through the flame than through air since the ions increase the conductivity.

Raw interviews: http://www.youtube.com/watch?v=8dcw98B2Nzg
The question has arisen often enough that I thought I'd answer it. If you hold views that are consistent with the majority of the population, does that make you stupid? I don't think so. Science has uncovered a lot of counterintuitive things about the universe, so it's unsurprising that non-scientists hold beliefs inconsistent with science. But when we teach, we must take into account what the learners know, including their incorrect knowledge. That is the reason a lot of Veritasium videos start with the misconceptions.

Want to read my PhD? You can download the full text here: http://www.physics.usyd.edu.au..../pdfs/research/super

An atom is mostly empty space, but empty space is mostly not empty. The reason it looks empty is because electrons and photons don't interact with the stuff that is there, quark and gluon field fluctuations.
It actually takes energy to clear out space and make a true 'empty' vacuum. This seems incredibly counter-intuitive but we can make an analogy to a permanent magnet. When at low energies, like at room temperature, there is a magnetic field around the magnet due to the alignment of all the magnetic moments of the atoms. But if you add some energy to it by heating it, the particles gain thermal energy, which above the Curie temperature makes their magnetic moments randomly oriented and hence destroying the magnetic field. So in this case energy is needed to clear out the field, just as in the quantum vacuum.

Special thanks to Professor Derek Leinweber, find out more about his research here: http://bit.ly/ZZTKFP

The physics behind Kelvin's Thunderstorm explained. No, it is not a practical way of generating electricity, which is why we use turbines at hydro stations.

This video goes into more detail about the phenomenon demonstrated in this Hunger Games collab video: http://youtu.be/Rwa26CXG1fc

Is the future of the universe already determined?
Vsauce tackles "What is Random?": https://youtu.be/9rIy0xY99a0

Special Thanks to: Prof Stephen Bartlett, Prof Phil Moriarty, Prof Andrea Morello, Prof Tim Bedding, Prof Michio Kaku, A/Prof Alex Argyros, Henry Reich, Vanessa Hill, Dianna Cowern, George Ruiz and Mystery Cat. Views expressed in this video are not necessarily those of the amazing experts listed above but their advice was invaluable in making this video.

Quantum simulation by PhET:
https://phet.colorado.edu/en/s....imulation/quantum-tu

Music by
Jake Chudnow: https://soundcloud.com/jakechudnow
Amarante Music: https://soundcloud.com/amarantemusic

DNA animations by http://www.wehi.tv

Space animations by NASA

Topic inspired by The Information - a history, a theory, a flood by James Gleick

Filmed on location at the University of Sydney, Washington DC and LA

Stained glass is thicker at the bottom - so is it a liquid? Earth's mantle enables plate tectonics, so is it a liquid?
Check out Audible: http://bit.ly/AudibleVe
Sign up for the mailing list: http://www.veritasium.com
Pitch drop experiment: http://www.thetenthwatch.com

Thanks to Meg Rosenburg for scripting and animation, Raquel Nuno for filming and Aaron White for script consultation.

How does a transistor work? https://www.youtube.com/watch?v=IcrBqCFLHIY
Silicon-28 sphere: http://bit.ly/10J1G2o
This episode supported by audible.com: http://bit.ly/ZJ5Q6z

We have looked at how a transistor works, the fundamental unit of classical computers, and how a quantum computer works in theory, taking advantage of quantum superposition to hold exponentially more information than classical computers. Now we look at the practical side of making a quantum bit, or qubit. How do you put it in a state where it is stable? How do you read and write information on it? These processes are described for a solid state qubit - a phosphorous atom in a silicon crystal substrate. Both the electron and the nucleus of the phosphorous atom can be used as qubits.

Thanks to A/Prof. Andrea Morello: http://bit.ly/17wZ7lt

Thanks to Henry Reich (MinutePhysics) for pushing me to make the explanations and visualizations clearer.

Heisenberg's uncertainty principle tells us that it is impossible to simultaneously measure the position and momentum of a particle with infinite precision. In our everyday lives we virtually never come up against this limit, hence why it seems peculiar. In this experiment a laser is shone through a narrow slit onto a screen. As the slit is made narrower, the spot on the screen also becomes narrower. But at a certain point, the spot starts becoming wider. This is because the photons of light have been so localised at the slit that their horizontal momentum must become less well defined in order to satisfy Heisenberg's uncertainty principle.

I based this video on one by Prof. Walter Lewin of MIT: http://bit.ly/100Wk2K

Henry (MinutePhysics) has previously made a video about Heisenberg's Uncertainty Principle where he treats it as less spooky and more a consequence of waves: http://bit.ly/TV3xO5

Sixty Symbols has a great video on Planck's constant: http://bit.ly/11upebY

Thanks to the University of Sydney for hosting this experiment, especially to Tom and Ralph for their assistance getting it working.

Music: Kevin McLeod (Incompetech.com) Mirage and Danse Macabre

We have just seen the first image of a black hole, the supermassive black hole in the galaxy M87 with a mass 6.5 billion times that of our sun. But what is that image really showing us?

This is an awesome paper on the topic by J.P. Luminet:
Image of a spherical black hole with thin accretion disk
Astronomy and Astrophysics, vol. 75, no. 1-2, May 1979, p. 228-235
https://ve42.co/luminet

Using my every day intuition I wondered: will we see the "shadow" of the black hole even if we're looking edge on at the accretion disk? The answer is yes because the black hole warps space-time, so even if we wouldn't normally be able to see the back of the accretion disk, we can in this case because its light is bent up and over the black hole. Similarly we can see light from the bottom of the back of the accretion disk because it's bent under the bottom of the black hole. Plus there are additional images from light that does a half turn around the black hole leading to the inner rings.

What about the black hole "shadow" itself? Well initially I thought it can't be an image of the event horizon because it's so much bigger (2.6 times bigger). But if you trace back the rays, you find that for every point in the shadow, there is a corresponding ray that traces back to the event horizon. So in fact from our one observing location, we see all sides of the event horizon simultaneously! In fact infinitely many of these images, accounting for the virtually infinite number of times a photon can orbit the black hole before falling in. The edge of the shadow is due to the photon sphere - the radius at which light goes around in closed orbits. If a light ray coming in at an oblique angle just skims the photon sphere and then travels on to our telescopes, that is the closest 'impact parameter' possible, and it occurs at sqrt(27)/2*r_s

Huge thanks to:
Prof. Geraint Lewis
University of Sydney https://ve42.co/gfl
Like him, I'm hoping (predicting?) we'll see some moving images of black holes tomorrow

Prof. Rana Adhikari
Caltech https://ve42.co/Rana

Riccardo Antonelli - for excellent images of black holes, simulations and ray-tracing code, check out:
https://ve42.co/rantonels

The Event Horizon Telescope Collaboration
Check out their resources and get your local link for the livestream here: https://ve42.co/EHT

Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Ron Neal, Stan Presolski, Terrance Shepherd, Penward Rhyme

Filming by Raquel Nuno
Animation by Maria Raykova

NOTE: This video will appear in a playlist on Smarter Every Day hence the references to Veritasium. Destin does lots of cool science stuff - check out his channel if you haven't already http://www.youtube.com/destinws2

We have been collaborating on rotational motion, which is timely for some of the videos I've been doing lately. In this video I talk about gyroscopic precession - the "wobbling" of a spinning top around its axis.

This is caused by the torque due to the object's weight. The big idea is that the torque vector increases angular momentum in the direction of torque. So if there is no angular momentum initially, it will cause the system to swing in such a direction that it is rotating with new angular momentum in the direction of the torque. However, if there was angular momentum to begin with, the torque will change the direction of that angular momentum by causing precession.

It's a little shaky but if you average out the oscillations I think the result is clear. Again, huge thank you's to A/Prof Emeritus Rod Cross, Helen Georgiou, Alex Yeung, and Chris Stewart, Tom Gordon, the University of Sydney Mechanical Engineering shop, Duncan and co. Ralph and the School of Physics.

The Higgs Boson is awesome but it's NOT responsible for most of your mass! Thanks to audible.com for supporting this episode: http://bit.ly/ZJ5Q6z
The Higgs mechanism is meant to account for the mass of everything, right? Well no, only the fundamental particles, which means that electrons derive their mass entirely from the Higgs interaction but protons and neutrons, made of quarks, do not. In fact the quark masses are so small that they only make up about 1% of the mass of the proton (and a similar fraction of the neutron). The rest of the mass comes from the energy in the gluon field. Gluons are massless, but there is so much energy in the field that by E=mc^2 there is a significant amount of mass there. This is where most of your mass comes from and the mass of virtually everything around you.

Thanks to Professor Derek Leinweber for his great images, animations and explanations. Check out his site to find out more: http://bit.ly/ZZTKFP

Back in 2012, we all met for the first time at BrainSTEM - a conference of science YouTubers, instigated by Henry of MinutePhysics (Thank You Henry!!!) bringing together the most awesome STEM personalities from around the world. People like Vsauce, John Green, Vihart, Destin from Smarter Every Day, CGP Grey, Brady Haran of Numberphile et al. I had an awesome three days hanging out with all the cool people in this video and hopefully this is only the start of many fruitful collaborations to come. Thanks everyone!!!

Now this happens to be video 100 for me. It's not really about science, but I think it's pretty awesome because it features all of my YouTube heroes.

Does quantum entanglement make faster-than-light communication possible?
What is NOT random? http://bit.ly/NOTrandoVe
First, I know this video is not easy to understand. Thank you for taking the time to attempt to understand it. I've been working on this for over six months over which time my understanding has improved. Quantum entanglement and spooky action at a distance are still debated by professors of quantum physics (I know because I discussed this topic with two of them).

Does hidden information (called hidden variables by physicists) exist? If it does, the experiment violating Bell inequalities indicates that hidden variables must update faster than light - they would be considered 'non-local'. On the other hand if you don't consider the spins before you make the measurement then you could simply say hidden variables don't exist and whenever you measure spins in the same direction you always get opposite results, which makes sense since angular momentum must be conserved in the universe.

Everyone agrees that quantum entanglement does not allow information to be transmitted faster that light. There is no action either detector operator could take to signal the other one - regardless of the choice of measurement direction, the measured spins are random with 50/50 probability of up/down.

Special thanks to:
Prof. Stephen Bartlett, University of Sydney: http://bit.ly/1xSosoJ
Prof. John Preskill, Caltech: http://bit.ly/1y8mJut

Looking Glass Universe: http://bit.ly/17zZH7l
Physics Girl: http://bit.ly/PhysGirl
MinutePhysics: http://bit.ly/MinPhys
Community Channel: http://bit.ly/CommChannel
Nigel, Helen, Luke, and Simon for comments on earlier drafts of this video.

Filmed in part by Scott Lewis: http://google.com/+scottlewis

Music by Amarante "One Last Time": http://bit.ly/VeAmarante

A head-vaporizing laser with a perfect wavelength detecting sub-proton space-time ripples.
Huge thanks to Prof Rana Adhikari and LIGO: http://ligo.org
Here's how he felt when he learned about the first ever detection: https://youtu.be/ViMnGgn87dg

Thanks to Patreon supporters:
Nathan Hansen, Donal Botkin, Tony Fadell, Saeed Alghamdi, Zach Mueller, Ron Neal
Support Veritasium on Patreon: http://bit.ly/VePatreon

A lot of videos have covered the general overview of the discovery of gravitational waves, what they are, the history of the search, when they were found but I wanted to delve into the absurd science that made the detection possible.

When scientists want one megawatt of laser power, it's not just for fun (though I'm sure it's that too), it's because the fluctuations in the number of photons is proportional to their square root, making more powerful beams less noisy (as a fraction of their total). The smoothest mirrors were created not for aesthetic joy but because when you're trying to measure wiggles that are a fraction the width of a proton, a rough mirror surface simply won't do.

Filmed by Daniel Joseph Files

Music by Kevin MacLeod, http://www.incompetech.com "Black Vortex" (appropriately named)

Music licensed from Epidemic Sound http://epidemicsound.com "Observations 2" (also appropriately named)