Wendy Freedman

I was at the Carnegie Institution with Alan Sandish.

He kind of disagreed.

Oh, I'm trying to think of when it was announced.

It's already happened.

Oh, yes.

Yes, we did.

We had a nice.

In fact, your people check with me.

Was there a date where I could do this?

Yes.

The Hubble tension is what's arisen in the last decade or so.

We make measurements of the Hubble constant, the current expansion rate, locally using stars like Cepheids.

We also use red giant branch stars and other ways of doing these measurements tied into Type Ia supernovae, these bright supernovae.

Yeah, they're rare stars.

For example, Cepheids, when we go and try and discover them, like we did with Hubble, maybe one in a thousand stars that we measure turns out to be a Cepheid.

So they're rare.

But they also have a signature, and in the case of Cepheids, discovered by Henrietta Leavitt, that the brightness of the star correlates with how fast it's varying in its brightness, so-called period luminosity relations.

And we can use that relationship to determine the distance.

That's right.

Everything that we have done since then rests on her work.