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The universe is big, but it’s peanuts compared to the eternally inflating multiverse. But just how many universes are there? What are they like? And most importantly, what can they tell us about … aliens?

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Hosted by Matt O’Dowd
Written by Matt O’Dowd
Graphics by Leonardo Scholzer
Directed by: Andrew Kornhaber
Executive Producers: Eric Brown & Andrew Kornhaber

End Credits Music by J.R.S. Schattenberg: https://www.youtube.com/channel/UCRl6-nb4iOnsij-vnpAjp0Q

Imagine it: the observable part of our universe is 93 billion light years across, and that’s just a small fraction of the stuff created in our Big Bang. But in the eternal inflation picture, ours is just one among uncountable bubble universes. Bubbles that are continuously appearing and growing within a vastly larger spacetime that itself expands at an exponentially accelerating rate. A greater inflationary spacetime whose expansion never ends. We looked at the bizarre idea of eternal inflation in recent episodes – but we stopped short of exploring the full implications of this proposition. Those implications are, frankly, completely nuts. Some may also be true.

Big Bang Supporters:
Alexander Tamas
Anton Lifshits
David Barnholdt
David Boyer
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You know what a planet is, right? A big round thing that orbits a star. Uh, not so fast. The surprisingly vicious debate over the planetary status of Pluto has given us a fascinating glimpse into what a scientific definition really is. And perhaps the word planet is too vague to be used as a scientific definition at all.

Hosted by Matt O’Dowd
Written by Drew Rosen and Matt O’Dowd
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We love to classify things. Labels help us keep stuff organized in our heads. In science, categorization provides a fast and easy way to know the properties of a member of the group just by knowing what group it belongs to. Chemists group elements on the periodic table, those groups exhibit similar chemical behavior that reflect outer-shell electron number. Biologists group organisms by similar physical characteristics, and this taxonomy reflects genetic relationships. Astronomers are all about space taxonomy. We classify galaxies based on their shape, black holes based on how they feed, stars based on their colour and brightness, and planets by… well, by a set of criteria that has caused more tension and heartbreak than any made-up grouping scheme really should. Because a change in that scheme demoted Pluto from planet to not-planet. Today we’re going to settle whether this was reasonable, and whether we should keep the word “planet” at all.

Big Bang Supporters:
Alexander Tamas
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David Barnholdt
David Boyer
David Nicklas
Fabrice Eap
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Quasar Supporters:
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Spinning objects have strange instabilities known as The Dzhanibekov Effect or Tennis Racket Theorem – this video offers an intuitive explanation.
Part of this video was sponsored by LastPass, click here to find out more: https://ve42.co/LP

References:
Prof. Terry Tao’s Math Overflow Explanation: https://ve42.co/Tao

The Twisting Tennis Racket
Ashbaugh, M.S., Chicone, C.C. & Cushman, R.H. J Dyn Diff Equat (1991) 3: 67. https://doi.org/10.1007/BF01049489

Janibekov’s effect and the laws of mechanics
Petrov, A.G. & Volodin, S.E. Dokl. Phys. (2013) 58: 349. https://doi.org/10.1134/S1028335813080041

Tumbling Asteroids
Prave et al. https://doi.org/10.1016/j.icarus.2004.07.021

The Exact Computation of the Free Rigid Body Motion and Its Use in Splitting Methods
SIAM J. Sci. Comput., 30(4), 2084–2112
E. Celledoni, F. Fassò, N. Säfström, and A. Zanna
https://doi.org/10.1137/070704393

Animations by Ivy Tello and Isaac Frame

Special thanks to people who discussed this video with me:
Astronaut Don Pettit
Henry Reich of MinutePhysics
Grant Sanderson of 3blue1brown
Vert Dider (Russian YouTube channel)

Below is a further discussion by Henry Reich that I think helps summarize why axes 1 and 3 are generally stable while axis 2 is not:

In general, you might imagine that because the object can rotate in a bunch of different directions, the components of energy and momentum could be free to change while keeping the total momentum constant.

However, in the case of axis 1, the kinetic energy is the highest possible for a given angular momentum, and in the case of axis 3, the kinetic energy is the lowest possible for a given angular momentum (which can be easily shown from conservation of energy and momentum equations, and is also fairly intuitive from the fact that kinetic energy is proportional to velocity squared, while momentum is proportional to velocity – so in the case of axis 1, the smaller masses will have to be spinning faster for a given momentum, and will thus have more energy, and vice versa for axis 3 where all the masses are spinning: the energy will be lowest). In fact, this is a strict inequality – if the energy is highest possible, there are no other possible combinations of momenta other than L2=L3=0, and vice versa for if the energy is the lowest possible.

Because of this, in the case of axis 1 the energy is so high that there simply aren’t any other possible combinations of angular momentum components L1, L2 and L3 – the object would have to lose energy in order to spin differently. And in the case of axis 3, the energy is so low that there likewise is no way for the object to be rotating other than purely around axis 3 – it would have to gain energy. However, there’s no such constraint for axis 2, since the energy is somewhere in between the min and max possible. This, together with the centrifugal effects, means that the components of momentum DO change.

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Humanity’s future is glorious. As we master space travel, we’ll hop from one lifeless world to the next. Life will blossom in our path and the galaxy with shimmer with beautiful Earth-like orbs. Hmmm… maybe. This won’t sound so far fetched if we prove we can do it at least once. If we successfully terraform Mars.

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We already have the technology to bring humans safely to Mars and set up small settlements – or at least could do within a generation. But those settlements will need to be cocooned – shielded against the deadly cold, intense radiation, and the fatal lack of atmospheric pressure. Surely if we want to thrive on Mars – to make it into our second home – these settlers, or their descendants, will need to be able open the airlocks, shed their spacesuits, and step out onto a survivable surface. We’ll need to terraform Mars, as our first step in terraforming the galaxy.

Red Iris Mars habitat by James Telfer: http://bit.ly/JamesTelferRedIris

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Big Bang Supporters:
Alexander Tamas
Anton Lifshits
David Nicklas
Fabrice Eap
Juan Benet
Morgan Hough

Quasar Supporters:
Mark Heising
Mark Rosenthal
Vinnie Falco

Hypernova Supporters:
Chuck Zegar
Danton Spivey
Donal Botkin
Edmund Fokschaner
Hank S
John Hofmann
John R. Slavik
Jordan Young
Joseph Salomone
Matthew
Matthew O’Connor
Syed Ansar

Gamma Ray Burst Supporters:
Adrien Hatch
Adrian Molyneux
Alexey Eromenko
Andreas Nautsch
Bradley Jenkins
Brandon Labonte
Carlo Mogavero
Dan Warren
Daniel Lyons
David Behtala
DFaulk
Dustan Jones
Geoffrey Short
James Flowers
James Quintero
John Funai
John Pollock
Jonah
Jonathan Nesfeder
Joseph Dillman
Josh Thomas
Kevin Lee
Kevin Warne
Kyle Hofer
Malte Ubl
Mark Vasile
Nathan Hitchings
Nicholas Nachefski
Nick Virtue
Paul Rose
Scott Gossett
Sigurd Ruud Frivik
Taras Vozniuk
Tim Jones
Tim Stephani
Yurii Konovaliuk
سلطان الخليفي

A planet has been predicted to orbit the sun with a period of 10,000 years, a mass 5x that of Earth on a highly elliptical and inclined orbit. What evidence supports the existence of such a strange object at the edge of our solar system?

Huge thanks to:
Prof. Konstantin Batygin, Caltech
Prof. David Jewitt, UCLA

I had heard about Planet 9 for a long time but I wondered what sort of evidence could support the bold claim: a planet at the very limits of our ability to detect one, so far out that its period is over 60 times that of Neptune. The planet 9 hypothesis helps explain clustering of orbits of distant Kuiper belt objects. It also explains how some of these objects have highly inclined orbits – up to 90 degrees relative to the plane of the solar system. Some are orbiting in reverse. Plus their orbits are removed from the orbit of Neptune, the logical option for a body that could have ejected them out so far. The fact that the perihelion is so far out suggests another source of gravity was essential for their peculiar orbits.

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Music from http://epidemicsound.com “Observations – From Now On” “Magnified XY”

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Earth’s magnetic field protects us from deadly space radiation. What if it were drastically weakened, as a precursor to flipping upside down? I mean, it has before … many, many times..

Hosted by Matt O’Dowd
Written by Matt O’Dowd
Graphics by Leonardo Scholzer
Directed by: Andrew Kornhaber
Produced By: Kornhaber Brown

Special Thanks to Lathrop Lab at University of Maryland:
https://complex.umd.edu/

Check Out Lathrop Lab’s YouTube Channel to learn more about their 3-meter experiment that models the Earth’s core:
https://www.youtube.com/channel/UC-nUrQmFR3pFgEVwW0qAURA

Spaceship Earth has a literal deflector shield. A geomagnetic field. Lines of magnetic force, forged by currents in the planet’s molten core, erupt from the surface close to the north south geographic poles, connecting to each other to wreath the planet in a dipole field, like a gigantic bar magnet. Magnetic fields exert a force on moving charged particles, causing them to spiral around those force lines. That’s helpful, because Earth is constantly bombarded by very fast moving charged particles, especially coming from the Sun. Our magnetic field deflects the worst of these. Not all planets are so lucky. Mars, with its solid core, has no such shield – and so the red planet’s atmosphere was stripped away by the solar wind billions of years ago.

Want Even More Great Space Content? Check out the Exciting Summer of Space Playlist
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Big Bang Supporters:
Alexander Tamas
Anton Lifshits
David Nicklas
Fabrice Eap
Juan Benet
Morgan Hough

Quasar Supporters:
Mark Heising
Mark Rosenthal
Vinnie Falco

Hypernova Supporters:
Chuck Zegar
Danton Spivey
Donal Botkin
Edmund Fokschaner
Hank S
John Hofmann
John R. Slavik
Jordan Young
Joseph Salomone
Matthew
Matthew O’Connor
Syed Ansar

Gamma Ray Burst Supporters:
Adrien Hatch
Adrian Molyneux
Alexey Eromenko
Andreas Nautsch
Bradley Jenkins
Brandon Labonte
Carlo Mogavero
Dan Warren
Daniel Lyons
David Behtala
DFaulk
Dustan Jones
Geoffrey Short
James Flowers
James Quintero
John Funai
John Pollock
Jonah
Jonathan Nesfeder
Joseph Dillman
Josh Thomas
Kevin Lee
Kevin Warne
Kyle Hofer
Malte Ubl
Mark Vasile
Nathan Hitchings
Nicholas Nachefski
Nick Virtue
Paul Rose
Scott Gossett
Sigurd Ruud Frivik
Taras Vozniuk
Tim Jones
Tim Stephani
Yurii Konovaliuk
سلطان الخليفي

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Do you want to major in Astrophysics? Are you thinking about becoming (or ever just wondered how one becomes) an Astrophysicists? Do you want to know Matt O’Dowd’s origin story? Then buckle up and enjoy the ride and try your astrophysics skill in calculating bubble universes to try to win some free Space Time Swag from the Merch Store.

Hosted by Matt O’Dowd
Written by Matt O’Dowd
Graphics by Murilo Lopes
Directed by: Eric Brown
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To Jump to Challenge Question:
https://youtu.be/n8cEZM1lN5g?t=617

Email Challenge Answer to by 9/9/19:
PBSSpacetime@gmail.com
Subject line: Eternal Inflation Challenge

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Big Bang Supporters:
Alexander Tamas
Anton Lifshits
David Nicklas
Fabrice Eap
Juan Benet
Morgan Hough

Quasar Supporters:
Mark Heising
Mark Rosenthal
Vinnie Falco

Hypernova Supporters:
Chuck Zegar
Danton Spivey
Donal Botkin
Edmund Fokschaner
Hank S
John Hofmann
John R. Slavik
Jordan Young
Joseph Salomone
Matthew
Matthew O’Connor
Syed Ansar

Gamma Ray Burst Supporters:
Adrien Hatch
Adrian Molyneux
Alexey Eromenko
Andreas Nautsch
Bradley Jenkins
Brandon Labonte
Carlo Mogavero
Dan Warren
Daniel Lyons
David Behtala
DFaulk
Dustan Jones
Geoffrey Short
James Flowers
James Quintero
John Funai
John Pollock
Jonah
Jonathan Nesfeder
Joseph Dillman
Josh Thomas
Kevin Warne
Kyle Hofer
Malte Ubl
Mark Vasile
Nathan Hitchings
Nicholas Nachefski
Nick Virtue
Paul Rose
Scott Gossett
Sigurd Ruud Frivik
Taras Vozniuk
Tim Jones
Tim Stephani
Yurii Konovaliuk
سلطان الخليفي

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We actually have a pretty good idea of what might have happened before the Big Bang. That is, as long as we define the Big Bang as the extremely hot, dense, rapidly expanding universe that is described by Einstein’s equations. That picture of the universe is very solid down to about a trillionth of a second after the supposed beginning of time. We can make good guesses down to about 10^-30th of a second. But before that?

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Check out the Big Bang and Cosmic Inflation Playlist to learn More
https://www.youtube.com/watch?v=aPStj2ZuXug&list=PLsPUh22kYmNCc3WCKb5yF136QSRf0xErm

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Big Bang Supporters:

Alexander Tamas
Anton Lifshits
David Nicklas
Fabrice Eap
Juan Benet
Morgan Hough

Quasar Supporters:

Mark Heising
Mark Rosenthal
Vinnie Falco

Hypernova Supporters:
Chuck Zegar
Danton Spivey
Donal Botkin
Edmund Fokschaner
Hank S
John Hofmann
John R. Slavik
Jordan Young
Joseph Salomone
Matthew
Matthew O’Connor
Syed Ansar

Gamma Ray Burst Supporters:

Adrien Hatch
Adrian Molyneux
Alexey Eromenko
Andreas Nautsch
Bradley Jenkins
Brandon Labonte
Carlo Mogavero
Dan Warren
Daniel Lyons
David Behtala
DFaulk
Dustan Jones
Geoffrey Short
James Flowers
James Quintero
John Funai
John Pollock
Jonah
Jonathan Nesfeder
Joseph Dillman
Josh Thomas
Kevin Warne
Kyle Hofer
Malte Ubl
Mark Vasile
Nathan Hitchings
Nicholas Nachefski
Nick Virtue
Paul Rose
Scott Gossett
Sigurd Ruud Frivik
Taras Vozniuk
Tim Jones
Tim Stephani
Yurii Konovaliuk
سلطان الخليفي

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.

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This is a VR180 video so pop on your Google Cardboard or VR Headset to be totally immersed in our world! No headset? No problem. Move your mobile phone around and catch the total 180 experience. Have fun looking down from the catwalk!

How can you build a telescope that can see the entire night sky without moving its dish? Well in this special episode of Space Time we took a tour of the Arecibo Observatory with a VR 180 camera so you could explore the incredible ingenuity of Arecibo’s giant spherical dish that allows it to reflect light from every spot on the sky in a symmetric way. We also talked to Dr. Abel Méndez about Exoplantes and Aliens!

Check out our interview with Dr. Abel Méndez about Finding Exoplanets and Talking to Aliens:
https://youtu.be/RrH9LwD1bx4

Hosted by Matt O’Dowd
Written by: Matt O’Dowd
Directed by: Eric Brown
Director of Photography: Eric Brouse
Sound: Brett Van Duesen
Editing: Brian Nils Johnson
Assistant Editing: Daniel Sircar
Produced By: Kornhaber Brown

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