What about dark energy allows it to resist the powerful inward pull of gravity and accelerate the rate of the universe’s expansion? Find out in this episode of Space Time. And watch our previous episodes on dark energy right here:
Part 1 – Will the Universe Expand Forever https://www.youtube.com/watch?v=xZTb6…
Part 2 – Why the Universe Needs Dark Energy https://www.youtube.com/watch?v=-4Pay…
Part 3 – What Does Dark Energy Really Do? https://www.youtube.com/watch?v=RUE_L…

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We’ve come a long way in our understanding of dark energy. In previous episodes we’ve looked at how our universe is paradoxically flat and how dark energy is exponentially accelerating the expansion of the universe. In this episode of Space Time we dive into the true nature of dark energy and how its antigravity effect and its other properties are having such bizarre effects on our universe.

Written and hosted by Matt O’Dowd

Made by Kornhaber Brown (www.kornhaberbrown.com)

Comments
James Bailey
https://www.youtube.com/watch?v=fsARBnvUB2E&lc=z13pj5mygwqhi3t3k23bfdn5fyf1dbsep

Fros7bite
https://www.youtube.com/watch?v=fsARBnvUB2E&lc=z135cleyiorcwhuke223ij3wgzbqs50si

Patrick Romo
https://www.youtube.com/watch?v=fsARBnvUB2E&lc=z13gfr2qkwaezxbu0231ftjxmu3vehuec

ArchNME
https://www.youtube.com/watch?v=fsARBnvUB2E&lc=z13jfhk5mmjehhxrr04cfd3hivjotdmz1yk0k

1019wc1019
https://www.youtube.com/watch?v=fsARBnvUB2E&lc=z13tjvvqxrapjplrw04ci3453zm2yt3iduk0k

Aging Reversed
https://www.youtube.com/watch?v=fsARBnvUB2E&lc=z13yyh45ntaft5pjn04cjthwdnrdfrhqwl00k

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

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)

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

______________________

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

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How does Inflation solve the Big Bang’s problems?

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Although much of the Big Bang Theory is widely accepted to be true, it only gets us part of the way there. Observable truths such as the CMB and the flatness of our universe reveal that there is no way the universe has been expanding at a constant rate since its beginning. It turns out Cosmic Inflation solves the Big Bang’s major problems quite well. So well in fact, that we might not even need a Big Bang at all!

FURTHER READING:

Inflation (cosmology)
http://bit.ly/1Meeff1

Cosmological constant
http://bit.ly/25nlp7Z

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COMMENTS:

Frank Schneider
https://www.youtube.com/watch?v=Aj6Kc…

DBlanding23
https://www.youtube.com/watch?v=Aj6Kc…

jodokastslo
https://www.youtube.com/watch?v=Aj6Kc…

Omicron Vega
https://www.youtube.com/watch?v=Aj6Kc…

______________________

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

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Why does our universe make spheres and disks?

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Our universe is not a very diverse place when it comes to shapes. Large celestial bodies become spheres, galaxies become discs, and there is little room for variation. Why is this? Well it turns out physics has some pretty strict rules when it comes to creating new planetary bodies. On this week’s Space Time, we explore equillibrium and symmetry, the two defining factors that shape our universe.

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COMMENTS:

Felix Ironfist
https://www.youtube.com/watch?v=JDmKLXVFJzk&lc=z12dwzk4iquld5g0323uivizxm2xxxdk2

Florent POUJOL
https://www.youtube.com/watch?v=JDmKLXVFJzk&lc=z13pcn3rgpzxexgym04cfbeokpeaspzidjw

Reuben Silva
https://www.youtube.com/watch?v=JDmKLXVFJzk&lc=z12bcv4w0muzd3ihm04cchbp0s3kyjpj3p00k

Dom Vasta
https://www.youtube.com/watch?v=JDmKLXVFJzk&lc=z13ns1kqdw2kf5bzm04ccd4arybjvvvgcow0k

______________________

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