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.

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.

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

How much would it take for you to risk $10?
Check out Audible: http://bit.ly/AudibleVe
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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

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

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.

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.

All the large-scale structure in the universe may owe its existence to nothing.
Sponsored by the Dyson 360 Eye Robot #ad: http://bit.ly/2cGqBRV
Support Veritasium on Patreon: http://bit.ly/VePatreon

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

Let's see how clearly I can explain this. We think of empty space as, well... empty, the epitome of nothingness. But as our understanding of physics has evolved we have realized that it's not truly empty. Space is filled with fields. There is a field for every subatomic particle. One for electrons, up quarks, down quarks, neutrinos and so on. In empty space these fields are basically zero, flat, nil. But it's impossible to make them perfectly zero so there are always some quantum fluctuations in the fields, even in a perfect vacuum. These are sometimes called virtual particles but they should really just be thought of as little disturbances in the field. Vacuum fluctuation play a role mediating the interactions of subatomic particles but they don't really have an impact on the large-scale structure of the universe, EXCEPT during inflation, right after the big bang when the universe increased in size 10^26 times. Due to this rapid expansion, those tiny fluctuations were blown up to the scale of the observable universe. And we know this by looking at the cosmic microwave background radiation where we can see slightly hotter and cooler parts of the early universe that correspond to density fluctuations. And it is these density fluctuations that allowed matter to clump together into large structures like the gigantic gas clouds that would go on to contain stars and planets. In case the video isn't clear, this is what I've been trying to say.

Animations by Gustavo Rosa

This video was sponsored in part by Dyson #ad

These are the molecular machines inside your body that make cell division possible. Animation by Drew Berry at the Walter and Eliza Hall Institute of Medical Research. http://wehi.tv

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

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

Every day in an adult human roughly 50-70 billion of your cells die. They may be damaged, stressed, or just plain old - this is normal, in fact it’s called programmed cell death.

To make up for that loss, right now, inside your body, billions of cells are dividing, creating new cells.

And cell division, also called mitosis, requires an army of tiny molecular machines.DNA is a good place to start - the double helix molecule that we always talk about.

This is a scientifically accurate depiction of DNA. If you unwind the two strands you can see that each has a sugar phosphate backbone connected to the sequence of nucleic acid base pairs, known by the letters A,T,G, and C.

Now the strands run in opposite directions, which is important when you go to copy DNA. Copying DNA is one of the first steps in cell division. Here the two strands of DNA are being unwound and separated by the tiny blue molecular machine called helicase.
It literally spins as fast as a jet engine! The strand of DNA on the right has its complimentary strand assembled continuously but the other strand is more complicated because it runs in the opposite direction.
So it must be looped out with its compliment strand assembled in reverse, section by section. At the end of this process you have two identical DNA molecules, each one a few centimeters long but just a couple nanometers wide.

To prevent the DNA from becoming a tangled mess, it is wrapped around proteins called a histones, forming a nucleosome.
These nucleosomes are bundled together into a fiber known as chromatin, which is further looped and coiled to form a chromosome, one of the largest molecular structures in your body.
You can actually see chromosomes under a microscope in dividing cells - only then do they take on their characteristic shape.

The process of dividing the cell takes around an hour in mammals. This footage is from a time lapse. You can see how the chromosomes line up on the equator of the cell. When everything is right they are pulled apart into the two new daughter cells, each one containing an identical copy of DNA.
As simple as it looks, this process is incredibly complicated and requires even more fascinating molecular machines to accomplish it. Let’s look at a single chromosome. One chromosome consists of two sausage-shaped chromatids - containing the identical copies of DNA made earlier. Each chromatid is attached to microtubule fibers, which guide and help align them in the correct position. The microtubules are connected to the chromatid at the kinetochore, here colored red.
The kinetochore consists of hundreds of proteins working together to achieve multiple objectives - it’s one of the most sophisticated molecular mechanisms inside your body. The kinetochore is central to the successful separation of the chromatids. It creates a dynamic connection between the chromosome and the microtubules. For a reason no one’s yet been able to figure out, the microtubules are constantly being built at one end and deconstructed at the other.
While the chromosome is still getting ready, the kinetochore sends out a chemical stop signal to the rest of the cell, shown here by the red molecules, basically saying this chromosome is not yet ready to divide
The kinetochore also mechanically senses tension. When the tension is just right and the position and attachment are correct all the proteins get ready, shown here by turning green.
At this point the stop signal broadcasting system is not switched off. Instead it is literally carried away from the kinetochore down the microtubules by a dynein motor. This is really what it looks like. It has long ‘legs’ so it can avoid obstacles and step over the kinesins, molecular motors walking the other direction.

Studio filming by Raquel Nuno

Why do spikes form on ice cubes? Without them the world would be vastly different.
Awesome Jingle by Accent: http://bit.ly/AccentVe
Thanks to Prof. Stephen Morris from UofT: http://bit.ly/1GFANBE

Filmed in part by Martin Marek in Olomouc, Czech Republic

Time lapse of a growing ice spike by Lesley Hill, Russ Sampson and Edward Lozowski, with technical help by Kenny Lozowski.

Ice spike image by Dan and Lynn Wolaver: http://wolaver.org/log/09.11.29.htm

Concerned ice spike video by rocknut420: https://www.youtube.com/watch?v=GwM0we_t94c

Earth footage courtesy of NASA: https://www.youtube.com/watch?v=G4BPOEmugtM

Ice vase image by PgunnG: http://www.reddit.com/r/pics/c....omments/1voeqk/so_i_

Second ice vase image by A K Haart: http://akhaart.blogspot.com/20....15_01_01_archive.htm

For a report on ABC's Catalyst program (http://www.abc.net.au/catalyst/), I visited the Large Hadron Collider in Switzerland to find out what is being done now that the Higgs Boson has been discovered.

Although its mass has been measured around 125-126 GeV most of the other properties of the particle remain unknown. Its spin appears to be 0 or 2 but more results are required to nail this down. If it is the standard model Higgs, the spin should be 0, resulting in a fairly symmetric distribution of decay products in the detectors.

We may know this year if it's not the standard model Higgs - this would be the case if it doesn't decay into specific particles with the expected frequency. However if it is the standard model Higgs, it may take many more years to be certain. The large hadron collider will be shut down in 2013 for upgrades so that higher energies up to 14 TeV can be tested. Right now the LHC is operating at 8 TeV. The next announcement is expected in December.

The nutrient content of food is declining. Is it because of soil depletion, selective breeding, or... something else?
Watch my new documentary, VITAMANIA: http://ve42.co/vita

I came across this story as I was making the film Vitamania. When you ask sellers of vitamins why you should take vitamin supplements even if you eat a healthy diet, they will say because our food doesn't contain all the nutrients it once did. This is supposedly due to soil depletion, cold storage, food ripening off the vine, and global transport of out-of-season foods. And to an extent this is true. Foods contain the greatest amount of nutrients if they are eaten soon after they are harvested. An unexpected source of nutrient decline is the increasing amount of carbon dioxide in the atmosphere. It causes plants to grow faster and bulk up on carbs but at the expense of other nutrients, so in percentage terms the amount of nutrients are actually declining. For now this decline is modest so supplementing with vitamin pills is probably unnecessary for most people with a healthy diet but it may be a concern in future.

Thanks to Kate Pappas & Chris Kamen for writing, producing and filming this video with me
Edited by Lucy McCallum
Sound mix by Wayne Hyett
Fact Checking by Calvin Lee and Claire Smith
Thanks to the Collingwood Children’s Farm and Glenn Fitzgerald from the University of Melbourne & Agriculture Victoria

Further Reading:

https://www.sciencedirect.com/....science/article/pii/
https://www.ncbi.nlm.nih.gov/p....ubmed/15637215/?ncbi
http://soils.wisc.edu/facstaff..../barak/poster_galler
https://www.politico.com/agend....a/story/2017/09/13/f
http://www.abc.net.au/news/201....8-05-24/scientists-w

Do negative air ions improve mood, anxiety, depression, alertness?
Part of this video was sponsored by LastPass, click here to find out more: http://bit.ly/2RZZTZk

Special thanks to Prof. Jack Beauchamp and Dr. Nathan Dalleska from Caltech for all their help running these experiments and discussing the research. For more, check out the links below:
http://www.cce.caltech.edu/peo....ple/jesse-l-jack-bea
http://beckmaninstitute.caltech.edu/eac.shtml

If you want to dig into the research on negative ions yourself, I suggest starting with the review studies:

Air ions and mood outcomes: a review and meta-analysis.
Perez V, Alexander DD, Bailey WH.
BMC Psychiatry. 2013 Jan 15;13:29.
https://www.ncbi.nlm.nih.gov/pubmed/23320516

Air ions and respiratory function outcomes: a comprehensive review
Dominik D Alexander, William H Bailey, Vanessa Perez, Meghan E Mitchell, and Steave Su
J Negat Results Biomed. 2013; 12: 14.
https://www.ncbi.nlm.nih.gov/p....mc/articles/PMC38485

Exposure of laboratory animals to small air ions: a systematic review of biological and behavioral studies.
Bailey WH, Williams AL, Leonhard MJ.
Biomed Eng Online. 2018 Jun 5; 17(1):72.
https://www.ncbi.nlm.nih.gov/pubmed/29866122

Thumbnail photography by Raquel Nuno

VFX by Alan Chamberlain

Sound recording by Whitney Clavin

Motion Graphics by Charlie Kilman

Music from Epidemic Sound: http://epidemicsound.com "Capture a Picture 1" and "Seaweed"

Boredom makes you more creative, altruistic, introspective, and helps with autobiographical planning.
This video was sponsored by LastPass: http://bit.ly/2wAsdUu

I feel like this video might come across as condescending but the person I'm really talking to is myself. Despite the fact that I know how useful it can be to be bored, I still find myself trying to fill every last moment with stimulus. Boredom is unpleasant - the open, unstructured thinking that can take place can also feel pointless. But now I'm made this video to remind myself how important boredom is so hopefully I'll make more time to be bored.

More resources:

The boredom leads people to shock themselves study:
Just Think: The challenges of the disengaged mind
https://wjh-www.harvard.edu/~d....tg/WILSON%20ET%20AL%

Boredom leads people to consider their future and set goals study:
Back to the future: Autobiographical planning and the functionality of mind-wandering
https://www.sciencedirect.com/....science/article/pii/

On boredom and altruism:
https://pdfs.semanticscholar.o....rg/ca72/0f959d3c9c31

Does boredom make us more creative?
https://www.tandfonline.com/do....i/abs/10.1080/104004

Amazing filming by Raquel Nuno

Music from http://epidemicsound.com "I Think I Was There" "Critical Thinking 2" "Wide Open" "Seaweed" "A Sound Foundation 1"

Music also by Kevin MacLeod http://incompetech.com "Fig Leaf Rag"

In 2018 the kg will be defined by Planck's constant, not a hunk of metal.
Try a free book from Audible for 30 days http://ve42.co/audible
Special thanks to the staff at NIST who made this possible: Darine Haddad, Jon Pratt, Stephan Schlamminger, and Ben Stein.

Additional footage and animations by Sean Kelley, Jennifer Lauren Lee, and Frank Seifert.

I have been obsessed with measurement for a long time and I'm not sure quite how it happened. The world's roundest object played a role in this. I guess I'm just fascinated by how difficult it is to pin down a quantity like a kilogram. A physical object seemed like a good idea until the mass of the international prototype kilogram wasn't as constant as expected. These methods of the Kibble balance and silicon sphere have shown better precision than 20 parts per billion, making them superior to the old method. The agreement between Avogadro approaches

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

Interferometer video by TSG Physics: https://www.youtube.com/watch?v=j-u3IEgcTiQ

Music from http://epidemicsound.com "ExperiMental1" by Gunnar Johnsén

Studio filming by Raquel Nuno

This is what the world would look like if you could see invisible air currents, temperature gradients, and differences in pressure or composition of the air.
Support Veritasium on Patreon: http://ve42.co/patreon

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

I first saw a Schlieren imaging setup around ten years ago in Melbourne. I was immediately fascinated by the way I could see the warm air coming off my hand. I hadn't expected the currents to be moving that fast or to be so visible. This was a tricky setup to get right because alignment is very important and here I'm just working with what I had lying around the house mostly (plus the mirror). For the best Schlieren photography, making sure the mirror is stable is essential. I want to improve my setup so the mirror doesn't wobble back and forth too much creating the pulsing light and dark sections of this video.

The relationship between index of refraction of air and temperature, pressure, humidity and wavelength is complicated. This website will calculate it for you: http://emtoolbox.nist.gov/Wavelength/Ciddor.asp

Slow motion by Hollywood Special Ops: http://www.hollywoodspecialops.com

Sound Effects by A Shell in the Pit: http://www.ashellinthepit.com

Filmed by Raquel Nuno
Special thanks to Blake Nichols for assistance

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

The truth, with photons.
I hope I've articulated everything clearly in this video. If not, I'll clarify in comments. Thanks to everyone who appears in this video and thanks to everyone who watches this video!

Veritasium is of course a combination of the latin 'veritas' meaning truth, and the common element ending 'ium'. I guess this is my version of the 'draw my life' craze that rolled through YouTube many years ago. Except I wanted to tell my story with the actual moments, the photons, the stored magnetic states. There's something about that which is so important to me (because I think the alternative involves fooling yourself) which is why I'm so fascinated by film and video.

One of my inspirations for the name Veritasium came from the end of the poem Ode on a Grecian Urn by John Keats, in which he writes:
"Beauty is truth, truth beauty,—that is all
Ye know on earth, and all ye need to know."

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

Music from http://epidemicsound.com
Magnified X1 - Gunnar Johnsen
Fluorescent Lights - Martin Gauffin
Dissolving Patterns - Ebb & Flod
Luna - Ebb & Flod

Additional music by Kevin MacLeod: http://incompetech.com
Sneaky Snitch

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"