We’re living in the middle of a remarkable cosmic coincidence, an incredibly brief period of time where both matter and dark energy both play a part in the fate of our universe. To better understand this video watch our other Dark Energy episodes:
Part 1 – Will the Universe Expand Forever https://www.youtube.com/watch?v=xZTb6sfHEX8
Part 2 – Why the Universe Needs Dark Energy https://www.youtube.com/watch?v=-4PayaEgEZc
Part 3 – What Does Dark Energy Really Do? https://www.youtube.com/watch?v=RUE_LUqcTvM

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In the past few episodes we have delved deep into cosmology. We have been building up the tools we need to understand dark energy and its influence on the universe. In this episode we will discuss the balance between dark energy and matter. If you add up the energy in any large volume of space, about 70% is dark energy and the remaining 30 % is “regular” matter. However the universe has been dark for a relatively short period. At some point in the past there was a perfect balance between energy and matter. Dark Energy has dominated the universe only during the tenure of life on Earth, although it’s effect has been felt for longer than that.

Here’s your Challenge question: For How many of those 100 past doublings has dark energy had any significant effect? Let’s say at least 10% of the energy density. And how for many of those infinite future doublings will regular matter and energy have a significant effect – again, at least 10% of the energy density?

Extra Credit: Also tell me how many billion years ago dark energy started to have a significant effect, and how many billion years in the future matter will cease to … matter?

Prizes: 3 Correct Answers for the “simple” question and 3 Correct Answers for the extra credit parts will receive Space Time t-shirts. To be eligible please explain your reasoning and show your working. Feel free to propose any solutions you come up with for the apparent cosmological coincidence. Do NOT give answers in the comment section – that’ll disqualify you for this and future challenge questions. Email your answers to pbsspacetime@gmail.com with the subject line Dark Energy Challenge within two weeks. We will filter by subject line, so make sure sure you use exactly this phrase to be considered.

Written and hosted by Matt O’Dowd

Made by Kornhaber Brown (www.kornhaberbrown.com)

Will Breakthrough Starshot make it to Alpha Centauri? Let’s find out.

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Yuri Milner’s Breakthrough Starshot is an interstellar travel expedition unlike any other before it. It’s many years in the making and is contingent on a series of incredible advancements in nanotechnology, materials science and laser power. Despite these hurdles, the project has been backed by some of the greatest minds in science today, including Stephen Hawking, legendary engineer Freeman Dyson, UK Astronomer Royal Martin Rees and dark energy Nobel Laureate Saul Perlmutter. Just how likely is it that Starshot’s journey to Alpha Centauri will succeed?

Written and hosted by Matt O’Dowd

Made by Kornhaber Brown (www.kornhaberbrown.com)

And be sure to check out our good friend Physics Girl’s video on Lightsails! https://www.youtube.com/watch?v=oIuvIDhcs8E
Comments
Satya Prakash
https://www.youtube.com/watch?v=RUE_LUqcTvM&lc=z12hu3v5llqfinenf22zfvo5eur2vftyy04

Scot McPhee
https://www.youtube.com/watch?v=RUE_LUqcTvM&lc=z13qwhvw1t3jxxpuz23rwhggwmqgfh3xy04

Sandeep Siwach
https://www.youtube.com/watch?v=RUE_LUqcTvM&lc=z12vxzcyxnbncpm0j22ozrtwqyi4fff5204

Accessless
https://www.youtube.com/watch?v=RUE_LUqcTvM&lc=z13thniqovzydhqcn22tf10y2waahjjhu04

Adrian Abdel
https://www.youtube.com/watch?v=RUE_LUqcTvM&lc=z124f52hsxaoi3o0a22aex3hqoiaxtvdl

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Breakthrough Starshot Initiative
http://breakthroughinitiatives.org/Initiative/3

Geoffrey Landis on light sails
http://www.geoffreylandis.com/laser_ion.htp

A rare look inside the Svalbard Global Seed Vault which is closed ~350 days a year
Check out Audible: http://bit.ly/AudibleVe
More info on the seed vault: http://wke.lt/w/s/EKFlK
My trip to Norway was funded by Screen Australia, Film Victoria and Genepool Productions as part of a new project. More information soon.

Special thanks to Bente Naeverdal and the Crop Trust: https://www.croptrust.org

Dark energy, what exactly does it do? Find out in this episode of Space Time! Part 3 in our Dark Energy series.
Part 1: https://www.youtube.com/watch?v=xZTb6sfHEX8
Part 2: https://www.youtube.com/watch?v=-4PayaEgEZc
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How does dark energy affect the universe’s expansion? Measuring past expansion history should tell us the future expansion without ever having to count any galaxies. To measure this we need to measure the redshift-distance relationship, which we will talk about in detail in this episode.

Written and hosted by Matt O’Dowd

Made by Kornhaber Brown (www.kornhaberbrown.com)

Comments
Pravar Parekh
https://www.youtube.com/watch?v=-4PayaEgEZc&lc=z13yy1xzenqrj1tnp22etlby2syevrie4

Yeshwanth Vejendla
https://www.youtube.com/watch?v=-4PayaEgEZc&lc=z13pvhdpjrfcsl14u04ce3dgrzy5frjqb34

Thomas Waclav (Ceasar)
https://www.youtube.com/watch?v=-4PayaEgEZc&lc=z13fcd5quk3svhbp304cfdjbwwndihnqwj0

Austin Pinheiro
https://www.youtube.com/watch?v=-4PayaEgEZc&lc=z12zgtdockbruxrih04cib2qwqfhgnrxjk00k
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White dwarf supernova simulation from “Three-Dimensional Simulations of the Deflagration Phase of the Gravitationally Confined Detonation Model of Type Ia Supernovae”, Jordan et al., 2007, http://arxiv.org/abs/astro-ph/0703573

Supernova Cosmology Project: Perlmutter et al. 1999, http://arxiv.org/abs/astro-ph/9812133

High-Z Supernova Search Team: Riess et al. 1998, http://arxiv.org/abs/astro-ph/9805201

Part 2 in our Dark Energy series.
Part 1: https://www.youtube.com/watch?v=xZTb6sfHEX8

Check out our sister channel Crash Course Physics to learn more about the basic foudations of Physics:
https://www.youtube.com/watch?v=ZM8ECpBuQYE&list=PL8dPuuaLjXtN0ge7yDk_UA0ldZJdhwkoV

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Now that we know the universe will continue to expand forever, we can begin to complete the first Friedmann equation, and determine the shape and geometry of our universe. At first glance, it would seem that the equation doesn’t quite add up, and that our universe is a hyperbolic plane. But when we add in the cosmological constant, the equation balances out, and we return to a flat universe.

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COMMENTS:

Deiter Meena
https://www.youtube.com/watch?v=xZTb6sfHEX8&lc=z13uzj2y2uf2xl3ck23zwfuxkqyzidsfh

Jack W
https://www.youtube.com/watch?v=xZTb6sfHEX8&lc=z13rih2gupnudr3x004cjbw4pyryezmi0ig

Mychelly Goulart
https://www.youtube.com/watch?v=xZTb6sfHEX8&lc=z13mzpkq3qauip1xw04cjvoxxsj1fhv5uac

Tomek Wooff
https://www.youtube.com/watch?v=xZTb6sfHEX8&lc=z12hxbtrbvezin5ra04cd3cyrou3fxk55o00k

Mr B
https://www.youtube.com/watch?v=xZTb6sfHEX8&lc=z13qfhkoclzqf11dx235d3zj0zucyjsxj04

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Written and hosted by Matt O’Dowd
Made by Kornhaber Brown (www.kornhaberbrown.com)

Will the Universe continue to expand outward or will it succumb to gravity and collapse upon itself? Find out in this episode of Space Time. Help us win a Webby Award by voting here: https://pv.webbyawards.com/2016/online-film-video/video-channels-and-networks/science-education

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Throughout history, there has been much speculation about what the fate of the universe would be. Many theorized that the universe would eventually succumb to the pull of gravity, and reverse its expansion in what was being called ‘The Big Crunch.’ However, with the help of mathematical equations from Newton, Einstein, and Alexander Friedmann, we now have an answer.

Special thanks to NAOJ and the European Southern Observatory for allowing usage of their photo of M83: http://apod.nasa.gov/apod/ap151008.html

Flourine production in lower mass stars: http://phys.org/news/2014-08-toothpaste-fluorine-stars.html
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Correction:
escape velocity = square root of (2GM/r)
– we accidentally left out the 2
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COMMENTS:

Henrique Rigitano
https://www.youtube.com/watch?v=6yLGeviU8FM&lc=z12menfxkpjnwfkfw23ehh4jwmqgst3ag04

ReVenGe TheRedFireFox
[deleted]

Richard van der Linden
https://www.youtube.com/watch?v=6yLGeviU8FM&lc=z13vglqyqzz4zbljq04cfthoqynjxhpwer00k

Mason Glaves
https://www.youtube.com/watch?v=6yLGeviU8FM&lc=z12cgzexssvbzb5ls23csfyq4papudwco

Rod Landaeta
https://www.youtube.com/watch?v=6yLGeviU8FM&lc=z13icr0jtzzqj5ro304cjjmbnpqstrnx52c

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Written and hosted by Matt O’Dowd
Made by Kornhaber Brown (www.kornhaberbrown.com)

Longyearbyen on Svalbard is the northernmost settlement with over 1000 residents
My trip to Norway was funded by Screen Australia, Film Victoria and Genepool Productions as part of a new project. More information soon.

More info on Svalbard: http://wke.lt/w/s/yiYNC

Music licensed from http://www.cuesongs.com “After Catalunya”
Spotify page: https://play.spotify.com/artist/2JnQ2AxkaRjlGCNmfkHiJd
iTunes: https://itunes.apple.com/gb/artist/emphemetry/id414183064

Captions:
Come take a walk with me around Longyearbyen, the largest town on the Norwegian islands of Svalbard.

Parts of it look familiar, but make no mistake, this place is different.

At 78 degrees North, it lies just 800 miles or 1300 kilometres from the North Pole. And with over 2,000 permanent inhabitants it is the Northernmost real town on Earth.

There are only 50km of road, including the small streets between houses, so people get around the island mainly on snowmobile.

In fact there are more registered snowmobiles than residents.

Anyone leaving town is required to travel with a gun and someone who knows how to use it because the islands are also home to polar bears.

The average daytime high is below freezing for all but four months of the year, and from the end of October to mid-February the sun doesn’t rise at all. This is the long polar night.

Living here is tough. This past December an avalanche in town destroyed 10 homes, which used to be here, killing two people.

So how did this cold, remote, ice-covered archipelago come to be inhabited?

The hills around town are rich in coal deposits that have been mined for over 100 years.

The coal was transported to the port via a series of aerial tramways some of which remain today, though they are no longer operational.

Coal is a reminder that Svalbard was not always an Arctic ice world. 360 million years ago it was actually in the tropics North of the equator. A swampy area, it was covered with the precursors to modern ferns, which were much larger than they are today, reaching 10-30 metres in height.

This vegetation was then covered in mud and sand and submerged under the sea. Over time it turned into the coal deposits that in the 20th century brought miners from Norway, Russia, and the US.

Most of the coal mines have now closed and the economy is gradually shifting towards tourism, education and research.

Tourists take trips on snowmobiles and dog sleds.

There is a university centre in Svalbard, which offers semester courses in biology, physics and geology.

And up on the side of a mountain is the Svalbard Global seed vault… but that’s a story for another time.

The locals tell me that interest in the region from different nations is increasing.

As the globe warms and Arctic ice shrinks, trade routes are opening up across the North. And Svalbard is strategically placed between North America, Asia and Europe.

One day in the future Svalbard may no longer be as cold or remote as it once was.

But for now it is a reminder of how through our ingenuity people can live in the most inhospitable of places.

Shot with a DJI Phantom 4 drone

Joni Mitchell was right, we are stardust.

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Stars are our stellar alchemists. They spend their entire lifespan creating and molding elements. In their final moments, a supernova spreads these elements out into the universe, providing the building blocks for new stars, planets, and even us!

‘The Recipe For Life…’ by It’s Okay To Be Smart
http://bit.ly/1UJbRkn

Colliding neutron stars produce heavy elements
Berger, Fong & Chornock 2013 http://arxiv.org/abs/1306.3960
https://www.cfa.harvard.edu/news/2013-19

Stellar Alchemist song by Kim Boekbinder
http://kimboekbinder.bandcamp.com/
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COMMENTS:

Al Hartman
https://www.youtube.com/watch?v=blSTT…

dredawgz1
https://www.youtube.com/watch?v=blSTT…

Adrian Blue
https://www.youtube.com/watch?v=blSTT…

mukul gupta
https://www.youtube.com/watch?v=blSTT…

______________________

Written and hosted by Matt O’Dowd
Made by Kornhaber Brown (www.kornhaberbrown.com)

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Fast Radio Bursts were puzzling physicist for quite some time. They were thought to be the result of large cataclysmic events such as supernovae, but this theory was proven wrong when it was discovered that they could repeat themselves. Now, we think that the rotation of young neutron stars may be the source of these intense energy bursts.

FURTHER READING:
https://en.wikipedia.org/wiki/Fast_radio_burst
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CHALLENGE ANSWER 1:
13.7 billion light years

CHALLENGE ANSWER 2:
7500 light years

CHALLENGE WINNERS:

Ada Warren
Jesús Pestana Puerta
Joel Vallette
Isobel Taylor
Corwin Pearson
Duc Hoang

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Written and hosted by Matt O’Dowd
Made by Kornhaber Brown (www.kornhaberbrown.com)

We also made a video about laser cooling! http://bit.ly/PhysGirl
Check out Audible: http://bit.ly/AudibleVe
Check out Beyond Slow Motion: http://bit.ly/VeBeyondSlowMo
More on this topic: http://wke.lt/w/s/ef3eV

Special thanks to Laser Away in Santa Monica for helping make this happen – your staff was awesome! http://bit.ly/VeLaserAway

Research and filming by Raquel Nuno and Aaron White.