For more info, please see http://www.physics.usyd.edu.au/~cross
In baseball and cricket the best pitchers and bowlers know how to make the ball move due to the effects of aerodynamics. If one side of the ball is rough, the ball swings towards that side because turbulent air 'clings' to that side of the ball and is deflected. Although baseballs and cricketballs appear symmetric, they can be made to fly through the air with a smooth or rough side by judicious angling of the seams combined with the axis of rotation.

The merging of two neutron stars was detected by gravitational waves and then by telescopes in all parts of the electromagnetic spectrum. This is a historic detection as it demonstrates:
- the first gravitational waves detected from inspiraling neutron stars
- the first joint observation by gravitational wave and electromagnetic wave astronomy
- identification of a gamma ray burst in conjunction with merging neutron stars
- how gravitational waves and gamma rays can be used together to locate their source

All evidence so far indicates that the data support General Relativity.

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

Graphics from:
Jets and Debris from a Neutron Star Collision
This animation captures phenomena observed over the course of nine days following the neutron star merger known as GW170817. They include gravitational waves (pale arcs); a near-light-speed jet that produced gamma rays (magenta); expanding debris from a "kilonova" that produced ultraviolet (violet), optical and infrared (blue-white to red) emission; and, once the jet directed toward us expanded into our view from Earth, X-rays (blue).
Credit: NASA's Goddard Space Flight Center/CI Lab

Virgo Helps Localize Gravitational-Wave Signals
Sky localizations of gravitational-wave signals detected by LIGO beginning in 2015 (GW150914, LVT151012, GW151226, GW170104), and, more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2017, scientists were better able to localize the gravitational-wave signals. The background is an optical image of the Milky Way. The localizations of GW150914, LVT151012, and GW170104 wrap around the celestial sphere, so the sky map is shown with a translucent dome.
Credit: LIGO/Virgo/NASA/Leo Singer (Milky Way image: Axel Mellinger)

Variety of Gravitational Waves and a Chirp
The signal measured by LIGO and Virgo from the neutron star merger GW170817 is compared here to previously detected binary black hole mergers. All signals are shown starting at 30 Hertz, and the progression of GW170817 is shown in real time, accompanied by its conversion to audio heard at the end of the movie. GW170817 was observable for more than 30 times longer than any previous gravitational-wave signal.
Credit: LIGO/University of Oregon/Ben Farr

LIGO is funded by the NSF, and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project.

More than 1,200 scientists and some 100 institutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at http://ligo.org/partners.php

The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia; and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.

On a stream of water you can levitate light balls of all sizes and even disks and cylinders. The mechanism is not the Bernoulli effect...
Want to make this at home? https://youtu.be/BppcHF2EdAY

My friend Blake from InnoVinci emailed me with a cool idea for a video and footage of levitating balls in water streams. Initially it was tough to explain the physics of what was going on. The standard Bernoulli effect relies on the object being completely immersed in the upward-flowing fluid. But in this case the water seems to form a single stream around the object and it's deflected away and down from the stream. By Newton's third law, the force on the water by the ball is equal and opposite to the force of the water back on the ball, pushing it up into the stream. There is a stable equilibrium position because if the ball moves into the stream, it "cuts off" the water going over the ball so it drifts out. If it drifts out too far, then lots of water passes over the ball, pushing it back into the stream.

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

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

Filmed by Raquel Nuno
Slow motion by Hollywood Special Ops http://hollywoodspecialops.com

Music from Epidemic Sound http://epidemicsound.com "Colored Spirals 3" "Magnified X 3" "In Orbit 2" "ExperiMental 1"

The best and worst predictions in science are both based on the same underlying physics
Check out the Great Courses Plus: http://ow.ly/cePe303oKDM
Support Veritasium on Patreon: http://bit.ly/VePatreon

Special thanks to:
Prof. Sean Carroll
Prof. Brian Schmidt
Prof. Stephen Bartlett
Prof. Geraint Lewis

More on this topic: http://wke.lt/w/s/XDkwi

Patreon supporters:
Bryan Baker, Donal Botkin, Tony Fadell, Jason Buster, Saeed Alghamdi, Nathan Hansen

Virtual particles are a way of talking about fields and their interactions as though particles are doing all the work. This is why there is some controversy around using the term 'virtual particles'. Some people think the term is useful, especially since in calculating with Feynman diagrams you draw all the particle interactions that are possible (and then do the calculations to get the right answer). While others feel this terminology is misleading because virtual particles don't behave like real particles and can't be observed.

Why does time appear to speed up as we get older? Can we slow it down?
Thanks to the National Geographic Channel for sponsoring this video!
The new season of Brain Games starts Sunday, February 14th at 9/8c - http://po.st/90S7Ow

Brain Games is an Emmy-nominated TV series that explores the inner workings of the human mind through experiments and interactive games. Did you know it's estimated that you have more than a dozen senses in addition to the standard five? One of those is a sense of time or chronoception. Tune in to the new season of Brain Games to learn about all of your senses, and more, starting Sunday, February 14 at 9/8c

References:

Ageing and duration judgement:
http://bit.ly/1TRN0cr

Nerve conduction velocity slowing with age:
http://bit.ly/23Wq6oE

Experiments with rats suggest time perception is distributed across brain:
http://bit.ly/1T6IjdO

Time perception with repeated stimuli:
http://bit.ly/1TRNbo5

Energy usage in brain with age:
http://bit.ly/1nXliOU

Time perception in moments of fear / danger:
http://bit.ly/1RoK7Ps
http://1.usa.gov/1TRNa3w
http://bit.ly/1Q8tDvW

Attention’s relation to time perception and recollection of perceived time:
http://bit.ly/20odeD8
http://bit.ly/1TRNfEf

Are you heaviest at night before you go to bed and lightest in the morning? I tried to tease out the factors to figure out what really causes weight gain and loss during the day, and what causes daily weight fluctuations.

This is the solution to: http://youtu.be/QD3hbVG1yxM
Watch this first!

Explanations for http://youtu.be/1Xp_imnO6WE
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For more on deflecting polar streams with electric fields, see:
http://pubs.acs.org/doi/abs/10.1021/ed077p1520


I'm in Hobart for a live show on Friday at UTAS followed by gigs in Sydney and Canberra next weekend.

Learned helplessness can prevent people from achieving their goals, something I've experienced first hand.
Check out Audible: http://bit.ly/AudibleVe
More walk and talk videos: http://bit.ly/2Veritasium

The answer to the question - what happens to a tennis ball tied to the bottom of a slinky after the top of the slinky is let go?

For a great explanation, check out Rhett Allain's analysis here: http://www.wired.com/wiredscie....nce/2011/09/modeling

How much would it take for you to risk $10?
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Can you solve this? http://bit.ly/248Ve
Regression to the mean: http://bit.ly/VeRTTM

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Psychological literature shows that we are more sensitive to small losses and than small gains, with most people valuing a loss around 1.5-2.5 times as much as a gain. This means that we often turn down reasonable opportunities for fear of the loss. However over the course of our lives we will be exposed to many risks and opportunities and this invariably means that taking every small reasonable bet will leave us better off than saying no to all of them.

NOTE: The video is not saying to accept every bet, only those with reasonable odds (preferably in your favour), and those which if you lose would not cause significant financial or other damage. In those cases it is wise to be loss averse!

Filmed by Adrian Tan

Thanks to Physics Girl for suggestions on previous versions of this video. https://www.youtube.com/physicswoman

Check out the original double slit experiment: http://www.youtube.com/watch?v=Iuv6hY6zsd0 - oh, and for the sun to be seen as single photons, you would have to be ~1000 light years away, so well past Pluto. For clarification on this video, please see: http://www.youtube.com/watch?v=OW7tfrTh66c
What would you see if you were drifting through space, looking back at the sun? Well its light intensity would decrease as the inverse square of distance from the sun. And you would imagine the intensity would decrease smoothly, asymptotically approaching zero.

But this is not what happens.

If you had sensitive enough eyes, like frogs' eyes, you would find that at some point the sun would start to flicker. You would see flashes of light separated by complete darkness. And as you drift further from the sun, what's strange is that these flashes do not decrease in brightness, but they do become less frequent. That's because light comes in lumps, called quanta or photons, which are indivisible. So if you try to spread light out very thinly, you reach a point where there are only single bits of light reaching an observer's eye at any given time.

I should acknowledge the book "The Fabric of Reality" by David Deutsch, which contains a similar story about a frog and a torch. It inspired me to make this film. Thanks also to MinutePhysics for reviewing earlier drafts and suggesting I make it more ridiculous.

Used in everything from bullet-proof vests to the walls of the Pentagon, polyurea's strength comes from its long-chain molecules.
Check out How Ridiculous: http://bit.ly/VeHowRidiculous
Snatoms magnetic molecules: http://bit.ly/VeSnatoms
Veritasium on Patreon: http://bit.ly/VePatreon

Special thanks to South Bay Line-X: http://southbaylinex.com/

Thanks to Patreon supporters:
Nathan Hansen, Bryan Baker, Donal Botkin, Tony Fadell, Saeed Alghamdi

Filmed by Prashanth Venkataramanujam

SFX by A Shell in the Pit

Hope this was worth the wait! So many people helped with this video: Prof John Sperry, Hank Green, Henry Reich, CGP Grey, Prof Poliakoff, my mum filmed for me in beautiful Stanley Park and Jen S helped with the fourth version of the script.

Prof John Sperry http://biologylabs.utah.edu/sperry/john.html
Hank Green (SciShow) http://www.youtube.com/user/scishow
Henry Reich (minutephysics) http://www.youtube.com/user/minutephysics
CGP Grey http://www.youtube.com/user/cgpgrey
Prof Poliakoff (Periodic Videos) http://www.youtube.com/user/periodicvideos

Also thanks to the Palais de la Decouverte - they helped me with the whole vacuum pump setup in Paris. No, I could not actually suck water up 10m - I did about 4m, but the vacuum pump was easily able to do it and I saw spontaneous boiling on all of our various trials. Footage from this may end up on 2Veritasium.

Trees create immense negative pressures of 10's of atmospheres by evaporating water from nanoscale pores, sucking water up 100m in a state where it should be boiling but can't because the perfect xylem tubes contain no air bubbles, just so that most of it can evaporate in the process of absorbing a couple molecules of carbon dioxide. Now I didn't mention the cohesion of water (that it sticks to itself well) but this is implicit in the description of negative pressure, strong surface tension etc.

Lift is an important concept, not only in flying but also in sailing. This week I'm talking to Olympic Sailor, Hunter Lowden. But before I get to the physics of sailing I thought I would explain lift since it's generally poorly understood.

minutephysics http://bit.ly/Muh6CC
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efit30 http://bit.ly/O4CMme
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numberphile http://bit.ly/numberphile



Music by Nathaniel Schroeder
youtube: http://bit.ly/pakJLE
myspace: http://mysp.ac/qtmZQj

Can we see things travelling faster than light?
Check out Audible: http://bit.ly/AudibleVe
Music by Amarante "One Last Thing" http://bit.ly/VeAmarante
Awesome animations by http://youtube.com/minutephysics
Thanks to Prof. Geraint Lewis for input on earlier drafts of this video.

The expanding universe is a complicated place. During inflation the universe expanded faster than light, but that's something that actually happens all the time, it's happening right now. This doesn't violate Einstein's theory of relativity since nothing is moving through space faster than light, it's just that space itself is expanding such that far away objects are receding rapidly from each other. Common sense would dictate that objects moving away from us faster than light should be invisible, but they aren't. This is because light can travel from regions of space which are superluminal relative to us into regions that are subluminal. So our observable universe is bigger than our Hubble sphere - it's limited by the particle horizon, the distance light could travel to us since the beginning of time as we know it.

The Salton Sea is the largest body of water in California, home to the second most diverse group of birds in America and it exists by accident.
Another great video on the Salton Sea: https://youtu.be/otIU6Py4K_A
I used archive from this video.

Music by Kevin MacLeod, www.incompetech.com ‘Mirage’, ‘Hyperfun’, ‘Marty Gots a Plan’, ‘Past the Edge’

Who on Earth is exposed to the most ionizing radiation?
Check out Audible: http://bit.ly/AudibleVe
I'm filming a documentary for TV about how Uranium and radioactivity have shaped the modern world. It will be broadcast in mid-2015, details to come. The filming took me to the most radioactive places on Earth (and some places, which surprisingly aren't as radioactive as you'd think). Chernobyl and Fukushima were incredible to see as they present post-apocalyptic landscapes. I also visited nuclear power plants, research reactors, Marie Curie's institute, Einstein's apartment, nuclear medicine areas of hospitals, uranium mines, nuclear bomb sites, and interviewed numerous experts.

Notes about measuring radiation:
Sieverts are a measure of 'effective dose' - that means they measure the biological impact of the energy transferred to tissues from radiation.

Obviously I owe a debt to the fantastic chart made by xkcd, which inspired my visual approach to this video.
https://xkcd.com/radiation/

DOSES MAY VARY
The level of radiation varies widely around the world depending mainly on altitude and geology (excluding nuclear accidents).

Estimates of particular doses also vary. All numbers reported in this video should be taken as order of magnitude only.

The most contentious claim may be that smokers receive the highest dose of ionizing radiation. This is not a whole body dose, but a dose to the lungs as specified in the video. References are here:
http://en.wikipedia.org/wiki/H....ealth_effects_of_tob
http://www.rmeswi.com/36.html

Special thanks to:
Physics Girl: https://www.youtube.com/physicswoman
MinutePhysics: https://www.youtube.com/minutephysics
Natalie Tran: https://www.youtube.com/communitychannel
Bionerd23: https://www.youtube.com/bionerd23
Nigel and Helen for feedback on earlier drafts of this video.

Music is "Stale Mate"

Silicone oil droplets provide a physical realization of pilot wave theories.
Check out Smarter Every Day: http://bit.ly/VeSmarter
Support Veritasium on Patreon: http://bit.ly/VePatreon

Huge thanks to:
Dr. Stephane Perrard, Dr Matthieu Labousse, Pr Emmanuel Fort, Pr Yves Couder and their group site http://dualwalkers.com/
Prof. John Bush: http://math.mit.edu/~bush/
Dr. Daniel Harris
Prof. Stephen Bartlett
Looking Glass Universe: http://bit.ly/LGUVe
Workgroup Bohemian Mechanics: http://www.mathematik.uni-muenchen.de/~bohmmech/
Filmed by Raquel Nuno

Thanks to Patreon supporters:
Nathan Hansen, Bryan Baker, Donal Botkin, Tony Fadell, Saeed Alghamdi

Thanks to Google Making and Science for helping me pursue my #sciencegoals. If you want to try this experiment, instructions are here: link.springer.com/article/10.1007/s12650-016-0383-5

The standard theory of quantum mechanics leaves a bit to be desired. As Richard Feynman put it, "I think I can safely say that no one understands quantum mechanics." This is because observations of experiments have led us to a theory that contradicts common sense. The wave function contains all the information that is knowable about a particle, yet it can only be used to calculate probabilities of where a particle will likely turn up. It can't give us an actual account of where the particle went or where it will be at some later time.

Some have suggested that this theory is incomplete. Maybe something is going on beneath the radar of standard quantum theory and somehow producing the appearance of randomness and uncertainty without actually being random or uncertain. Theories of this sort are called hidden variable theories because they propose entities that aren't observable. One such theory is pilot wave theory, first proposed by de Broglie, but later developed by Bohm. The idea here is that a particle oscillates, creating a wave. It then interacts with the wave and this complex interaction determines its motion.

Experiments using silicone oil droplets on a vibrating bath provide a remarkable physical realization of pilot wave theories. They give us a physical picture of what the quantum world might look like if this is what's going on - and this theory is still deterministic. The particle is never in two places at once and there is no randomness.

Edited by Robert Dahlem

Sound design by A Shell in the Pit

Why is there a bright spot behind spherical objects?
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Filmed by Nathan Watkins and Raquel Nuno, animation by Meg Rosenburg. Music by Kevin MacLeod, http://www.incompetech.com 'Scissors' 'Mirage' ' Marty Gots a Plan'. Special thanks to Laura Vican for helping with the experiment.

References:
http://www.princeton.edu/~rvdb..../images/Questar/Pois
Why Toast Lands Jelly-side Down: Zen and the Art of Physics Demonstrations By Robert Ehrlich