Does Timescapes DISPROVE Dark Energy?

The universe is expanding and that expansion is accelerating under the power of dark energy and eventually all matter and energy will be dispersed over such unthinkable distances that nothing can stop space from blowing up infinitely. Unless of course cosmologists blundered and dark energy doesn't even exist. Then it's back to the drawing board.

Sign Up on Patreon to get access to the Space Time Discord!

Check out the Space Time Merch Store

Sign up for the mailing list to get episode notifications and hear special announcements!

Hosted by Matt O'Dowd
Written by Matt O'Dowd
Post Production by Leonardo Scholzer, Yago Ballarini & Stephanie Faria
Directed by Andrew Kornhaber
Associate Producer: Bahar Gholipour
Executive Producer: 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 a production of Kornhaber Brown for PBS Digital Studios.
This program is produced by Kornhaber Brown, which is solely responsible for its content.
© 2024 PBS. All rights reserved.

Space Time Was Made Possible In Part By:

Big Bang
Wojciech Szymski
Bryce Fort
Peter Barrett
Alexander Tamas
Morgan Hough
Juan Benet
Vinnie Falco
Mark Rosenthal

Supernova
Grace Biaelcki
Glenn Sugden
Ethan Cohen
Stephen Wilcox
Mark Heising

Hypernova
Spencer Jones
Dean Galvin
Michael Tidwell
Robert DeChellis
Stephen Spidle
Massimiliano Pala
Justin Lloyd
Matthew Pabst
David Giltinan
Kenneth See
Gregory Forfa
Alex Kern
Zubin Dowlaty
Scott Gorlick
Paul Stehr-Green
Ben Delo
Scott Gray
Антон Кочков
Robert Ilardi
John R. Slavik
Donal Botkin
Chuck Zegar
Daniel Muzquiz

Gamma Ray Burst
Bryan White
Aaron Pinto
Kacper Cieśla
Satwik Pani
Param Saxena
John De Witt
Nathaniel Bennett
Sandhya Devi
Michael Oulvey
Arko Provo Mukherjee
Mike Purvis
Christopher Wade
Anthony Crossland
Grace Seraph
Stephen Saslow
Tomaz Lovsin
Anthony Leon
Lori Ferris
Koen Wilde
Nicolas Katsantonis
Richard Steenbergen
Joe Pavlovic
Kyle Luzny
Chuck Lukaszewski
Jerry Thomas
Nikhil Sharma
John Anderson
Bradley Ulis
Craig Falls
Kane Holbrook
Ross Story
Harsh Khandhadia
Michael Lev
Rad Antonov
Terje Vold
James Trimmier
Jeremy Soller
Paul Wood
Kent Durham
jim bartosh
John H. Austin, Jr.
Faraz Khan
Almog Cohen
Daniel Jennings
Jeremy Reed
David Johnston
Michael Barton
Isaac Suttell
Bleys Goodson
Mark Delagasse
Mark Daniel Cohen
Shane Calimlim
Tybie Fitzhugh
Eric Kiebler
Craig Stonaha
Frederic Simon
Jim Hudson
Michael Purcell
John Funai
Adrien Molyneux
Bradley Jenkins
Vlad Shipulin
Justin Waters
Thomas Dougherty
Zac Sweers
Dan Warren
Joseph Salomone
Julien Dubois

[RyanRidden]

Great video, thank you covering my group's work! There is definitely still plenty more work to do with Timescape, but its making a lot of progress. We're currently actively working on the BOA analysis, since this has subtle cosmological dependencies that need to be calculated in a Timescape context. One correction for this video is for the primary source of time dilation in Timescape. In General Relativity acceleration and deceleration cause clocks to tick slower, the greater the acceleration/deceleration the slower the clock ticks. This natural consequence of General Relativity is the primary cause of time dilation in Timescape, not the difference in average densities between voids and walls which is well known to be negligible. The way this manifests in Timescape is that gravity has acted to decelerate the Universe from the begining, however, the strength of gravity and therefore the deceleration was greater in denser regions. The difference in deceleration between filaments and voids was quite small (about 1Angstrom per second squared), but when integrated over this history of the Universe, this small effect leads to the large time differences predicted by Timescape. The standard model does not incorporate this effect from General Relativity, and assumes the Universe shares the same universal time frame.

[Zakificus]

One thing I love about science is that even negative results help move things forward. Ruling out things it isn't, is a good consolation for not finding out what it is, yet.

[Aztherion]

I’ve noticed that this channel isn’t showing up quite as often as before. Bad algorithm, shame on you! This is for sure one of the best channels out there! ❤️

[gb]

I've been watching this channel for over eight years, and it's still fantastic. One of the best channels on YouTube in my opinion.

[nathanpaulyoung]

Proudly being a datapoint. Love PBS Spacetime! It's a public service that we need more of!

[Daystar]

This is the first Spacetime video I've seen in my feed for months, and I've been subscribed for years. Thank you, my fellow data points.

[AllenKey]

This is the kind of channel that Youtube NEEDS to be promoting within and outside of the current community. Education, broadening horizons, we need these things more desperately than ever.

[dobuhaishen]

Can't be entirely confident, but believe there's a reasonable chance that this is my first-ever Youtube comment. Absolutely adore the content this channel produces; & is an indispensable source of knowledge from a field I have no connection to. Beyond my own layman's interest. The commitment, consistency, and balanced discourse you provide the community on these topics is unparalleled. Thank you Matt, and the entire team, as well as those of means who contribute to their Patreon. In the same vein, hopefully this comment, can serve as a meager offering in a similar spirit.

[A-ultra]

This has been my favorite channel on Youtube for 6 years now. It's hands down the best resource for learning about Astrophysics on Youtube.

[andrewblennerhassett]

So tired of YouTube pushing shorts at the expense of high quality content like this

[joeqmix]

PBS Space Time is one of the best channels out there. It justifies the very existence of YouTube.

[ronniefogg]

I'm a physical therapist, but I've always loved soaking up all the math and science knowledge that I can. I'm happy to be another data point because I truly appreciate the quality of PBS Space Time. Like great movies, it isn't afraid to trust the intelligence of its audience, and that's a truly rare gem these days.

[AllothTian]

When I read about Timescapes my first thought was: "They weren't accounting for that already?" But because it's such an obvious consideration, I knew there had to be more to the story. Sure enough, I wasn't aware of the additional tests. Thanks!

[RagoonX]

I've been watching this channel for about a decade now. It's taught me so much and even helped me get through some rough times. I will gladly be a data point!

[discodansin]

I used to watch PBS Space Time videos when I was a teenager. I stopped watching them in college but when I graduated I got an urge to watch them again. I was delighted to see the channel has been active all those years and this channel has reminded me that physics and cosmology will always be core interests of mine.

[jsthe]

This channel deserves so many more views

[rationaltexan]

Commenting for the algorithm. This channel is one of the most thought-provoking in all of YouTube. I absolutely love how the information is presented at a fast pace, and while simplified, doesn't feel dumbed down or patronizing. As a non-physicist, it actually inspires and challenges you to get up to speed and I love that.

[dischordia]

Certainly one of the very best channels YouTube has even hosted

[unlearningify]

Love it. It hurts my heart a little bit that this channel isn't one of, if not the most, pushed science channel on YouTube, as it's by far the best channel out there. Here's to many more years of content, and Matt specifically, we just couldn't do without our "Actor".

[kylelooper]

I normally don't feel knowledgeable enough to comment on these videos, but I take from them what I can, and I love the content.