The Crisis in Cosmology

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The search for a single number: the hubble constant, which is the rate of expansion of our universe, has consumed astronomers for generations. Finally, two powerful and independent methods have refined its measurement to unprecedented precision. The only problem is that they don’t agree. This calls into question some of our most basic assumptions about the universe.

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Previous Episode: Why String Theory Is Wrong

Hosted by Matt O'Dowd
Written by Matt O'Dowd
Graphics by Luke Maroldi
Directing by Andrew Kornhaber

In 1929, Edwin Hubble discovered the universe. He gave us our first incontrovertible proof that there are galaxies outside the Milky Way by measuring the distances to the spiral nebulae. They were many millions of light years from us –far outside the Milky Way and so must be galaxies in their own right. Combined with the Doppler-shift velocity measurements of Vesto Slipher, Hubble revealed that the galaxies are not only receding from us, but they are receding at a rate proportional to their distance.

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سلطان الخليفي

[vellyxenya]

"Dark Energy = Dark matter * (Speed of Dark)^2" got me laughing for much longer than I should have

[johnk]

A decent treatment of this outstanding problem in current cosmology... not too overly detailed, clear, and thorough ! Great job !

[artbyjes]

I get excited when there’s an argument between prediction and observation at this level — because it means we are missing something. And that means more science!

MORE SCIENCE! 😁👍

[firestem]

Thank you PBS and Matt! This is one of the most enjoyable and informative shows on youtube and anywhere else. I'm fascinated by astrophysics and these episodes only help to raise my interest until I can start taking these courses for my degree.

[josephcampbell]

Socrates: Shall we set down astronomy among the objects of study?

Glaucon: I think so, to know something about the seasons, the months and the years is of use for military purposes, as well as for agriculture and for navigation.

Socrates: It amuses me to see how afraid you are, lest the common herd of people should accuse you of recommending useless studies.
— Socrates

[Eilen]

I love to imagine what PBS Space Time will talk about 20 years from now, seeing how much questions about space time still haven’t been answered ^^

[RR-fioh]

Whether you use standard candles or cosmic microwave, your frozen burrito is still going to have a great cold spot.

[MCsCreations]

That's great. It may means that we are wrong about something and need to rethink things. And that's a great opportunity for us to discover what is wrong, but also to consolidate what's right.

[TheBendejo]

"We know everything, as long as we can prove this number is constant"
"... damnit."

[martir.]

7:41 subtitles say "are a factor of 100, 000 cooler", but actually 1/100, 000. A mere 10 orders of magnitude wrong :)

[ahmedabbas]

*An engineer walks in*
Just take the average of the results and call it a day...

[antoineroquentin]

we could just cut the photons in half and count the rings

[Myvoetisseer]

Man I'm smart.

*watches PBS video*

Man I'm stupid.

[DorianLust]

Question: Does the Local equation assume it starts from a singularity?

What if it didn't? How big would the initial universe need to be to make the two equations align?

[michaelsommers]

I really do wish you'd include links to the papers you cite.

[carterredfearn]

Why did this get taken down for like 30 minutes? I was watching and it was just deleted from existence. Am I a time Traveller?

[LeeGoGators]

I think it's fair to say the calculation based off the CMBR relies on more assumptions than that of Type 1a Supernovae.

[FlamingAtheist]

I need to get the BGM for these episodes. They are so calming and great to listen to while having a learn

[Dzeroed]

Well the answer is obvious isn't it?
Hubble Constant = 42

[RandallStephens]

A shame y'all didn't take the opportunity to recognize Chandrashekar who did the math to figure out the critical mass that makes IA supernovae luminosity so highly predicable--and for whom the Chandra X-ray telescope was named for.