Hello everyone, welcome to the Mindscape Podcast. I'm your host, John Carroll.

And today we're going to do the rare thing here on Mindscape and actually talk about something that I'm supposed to be an expert in.

You know, when we talked to Netta Engelhart a little while ago about black hole information, and I've actually written papers about black hole information,

but it's never been the central concern of my research, it's always been sort of a sidelight for me.

One thing that I have been very, very concerned about is large-scale cosmology, the expansion and acceleration of the universe.

So today we're extremely happy to have as our guest, Adam Reese, who is one of the discoverers of the acceleration of the universe,

and who has been noting that there is another cosmological anomaly known as the Hubble tension that calls into question,

the beautiful fit that we have in our cosmological models that we've been very proud of over the last 20 years

since the acceleration of the universe was discovered.

As Adam alludes to in the podcast, he and I were graduate students together.

In the astronomy department at Harvard at the same time, Adam was a floor below me in Perkins Hall.

My office mate was Brian Schmidt, who went on to lead the high-redshift supernova team.

So Adam and Brian were two people who shared the Nobel Prize with sole promoter for discovering the acceleration of the universe.

So I like to think that even though I had nothing to do with the actual research, that I least put them in the mindset of thinking about the acceleration of the universe,

I was interested in it at the time. I wrote a review article with Bill Press and Ed Turner about the possibility that there could be a cosmological constant.

Though to be perfectly honest, I was absolutely not saying in the early 1990s that there probably is a cosmological constant or dark energy or the acceleration of the universe.

You would have won money from me if you had tried to bet me at even money and you would take him the side that there was a non-zero cosmological constant.

I was skeptical and in my review article, I gave you all the reasons to be skeptical. I said, here's why it would be really weird if this were actually true.

Adam and Brian and Saul and their two big and very, very talented teams showed that there was.

So that was a huge surprise. As we talk about in this podcast, it was the kind of thing even though it was a huge surprise in 1998 when they discovered the acceleration of the universe,

we instantly had a good explanation for the surprise. The idea of a cosmological constant had been proposed by Einstein in 1917.

This is why in 1992 we could write a review article about it even though we were skeptical that it was there, we knew what it would be like if it were there.

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