How Much Of The Universe Can Humanity Ever See?

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There’s an absolute limit to our access to the universe beyond our own galaxy. There’s a limit to what we can ever hope to explore or send signals to, and a very different limit to what we can ever hope to witness. Today we’re going to explore the latter. We’re going to figure out the absolute limit of our future view of the universe, and of the universe’s ability to influence us. Next time we’ll turn it around and ask: how much of the external universe can WE potentially influence, and even explore?

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Hosted by Matt O'Dowd
Written by Matt O'Dowd & Euan McLean
Post Production by Leonardo Scholzer, Yago Ballarini, & Stephanie Faria
Directed by Andrew Kornhaber
Associate Producer: Bahar Gholipour
Executive Producers: Eric Brown & Andrew Kornhaber
Executive in Charge for PBS: Maribel Lopez
Director of Programming for PBS: Gabrielle Ewing
Assistant Director of Programming for PBS: John Campbell

Spacetime is produced by Kornhaber Brown for PBS Digital Studios.
This program is produced by Kornhaber Brown, which is solely responsible for its content.
© 2023 PBS. All rights reserved.

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[fiskfisk]

Douglas Adams quotes will win my heart every time ❤️

[starrywizdom]

“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space...”

Thanks so much for the *Hitchhikers' Guide to the Galaxy* reference -- there is a tiny corner of my heart that is forever Douglas Adams.

[mrfake]

Props to the camera man for going that far just to get the footage.

[keisimo]

Kudos for the team involved in doing this animations. They REALLY help understanding these advanced topics

[SauceGPT]

I love that you're wearing a shirt that says, "Heat Death is Coming" while talking about the expansion of the observable universe.

We appreciate the little things as well

[pete-m]

This was the BEST explanation of the subject I've ever seen! I understand the principles but had difficulty conceptualizing the 'edges' of the universe. It will take a few rewatches and lots of pausing, but I'm certain I will finally wrap my head around this. Thank you!

[oskarskalski]

PBS Space Time is the best! I always struggled to grasp the idea behind diagrams for each of this horizons and hoped that someone will make a video explaining it and there is no surprise that Matt did it. I will still need to watch this episode again to be able to understand it fully but it is great to have this video.

[alemorita]

This is hands-down the best reference I’ve seen to study conformal diagrams in FRW spacetimes. I’ve struggled with them a lot in the past from books and papers; the effort put into this animations has made them my go-to reference right now. Keep up this amazing work!

[deathxr]

What a magnificent episode. And that's saying a lot, all of your videos are incredibly good.

[jajssblue]

I absolutely love these videos deep diving on conformal mappings! It's such a powerful tool in GR.

[CapoJachu]

Not only I am impressed by how much new information on a topic I thought I grasped I learned from this episode, the way it was presented was absolutely beautiful. I greatly appreciate the effort spent on making this episode. Give the person responsible for the graphs a raise!

[Samael]

This is one of the best episodes, describing the basic concepts and definitions leading to a better understanding of time and expansion and the CMB that I've seen in a while. Good Job.

[Dronebotworkshop]

Always a great day when a new Space Time episode is released!

[rolirolster]

As you told me to imagine being a photon spat out by a star near the beginning of time, racing towards the Milky Way against expanding spacetime, I could feel myself red shifting across the decelerating horizon. Thank you for that superb imagery!

[realzachfluke]

This has to be the best-animated video on YouTube for an educational topic. Coupled with the writing and Matt's ability to present the material, and you've got some of the most beautiful work ever done on this platform, something I do not say lightly.

Mad props to you guys, and thank you for absolutely everything you do.

[EJBert]

I'll be re-watching this one a few times to understand all of the nuances. Great episode!

[Galadonin]

How many time can we rediscover the spacetime diagram ? It'll always blow my mind !

Quick edit : this is how to science vulgarization works. I'm not a fan of math, never been easy. Yet, from particules interaction, to the physics of black holes, expansion, dark matter/energy, geodesics ... We've learned a lot of complicated ways to represent GR to quantum mechanics, it's awesome ! Thanks Matt and your team

[williammogey]

Great episode! Very well explained, and a spacetime diagram that Georgia O'Keeffe would be proud of. Thank you, Matt.

[aaronturkey]

Yes 🙌🏻 for the Hitchhikers Guide to the Galaxy reference!

[Hossak]

"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." Great video :)