Okay, since a few people have asked: When Edwin Hubble presented evidence in 1925 that M31 was a galaxy outside the Milky Way, Betty White was about to turn three years old. The current oldest living person, a woman in France, was 18 or 19.

There are plenty of people alive today who were born into a world where we didn't yet have proof of anything beyond the Milky Way.

Here's a thread! https://mastodon.social/@mcnees/109614690601381175

The work of Edwin Hubble, Vesto Slipher, Annie Jump Cannon, Milton Humason, and others eventually established a clear relationship between galactic distance and redshift. Between that and scientists like Eddington promoting Lemaître's idea, Einstein came around and agreed that our Universe must be dynamical and expanding.

But Lemaître correctly pointed out that his model would imply an expansion velocity for galaxies — what we now refer to as Hubble's Law.

The idea that other galaxies exist outside our Milky Way had only been confirmed two years prior to this!

Einstein was skeptical of this claim. After all, he'd added a cosmological constant term to the equations of general relativity in 1917 to avoid exactly this sort of behavior.

Lemaître was not the first to propose an expanding universe. For example, Alexander Friedman’s proposal had appeared five years earlier, in his paper “On the Curvature of Space.”

inspirehep.net/literature/8573

Lemaître became a diocesan priest after serving in WWI. Later, he studied with Eddington at Cambridge, working on cosmology and stellar astronomy, applying insights from the still-new field of relativity. His studies took him to Harvard and MIT.

In 1927 he published a paper in Annales de la Société Scientifique de Bruxelles, claiming that relativity implies an expanding Universe. His proposal assumed a once-static configuration (preferred by Einstein at the time) that suddenly begins expanding.

Physicist & astronomer Georges Lemaître was born #OTD in 1894.

In 1927 he proposed a model of an expanding Universe. Then, in 1931, he ran the clock backwards and hypothesized its origin as a “unique atom” or “unique quantum,” paving the way for modern ideas about the Big Bang.

Lemaître and the expanding universe were the subject of a nifty Google doodle back in 2018.

Photo: Bettmann
Gif: The Google Doodle team

@feral_hattie 🙏

@flyhigh It is *so much better* than the other quote.

Today is the 78th anniversary of the Trinity Test, held #OTD in 1945.

The result of scientific collaboration on an unprecedented scale, most participants came to regret what they had unleashed. After the test, Kenneth Bainbridge remarked “Now we are all sons of bitches.”

Oppenheimer, on the other hand, isn’t on record as saying anything immediately after the blast. The Bhagavad Gita quote is a retcon, what he later described as a thought that ran through his head.

@JohnBarentine Wonderful news - these places are such treasures.

The team that worked out the Apollo 11 trajectories from Earth to the Moon included Katherine Johnson. She also performed calculations for how the Apollo Lunar Module would rejoin the Command and Service Module back in orbit

Image: NASA

@fraser I’ve killed a lot of afternoons looking through there.

Sunday morning is a pretty good time to take a look through NASA’s Project Apollo archive on Flickr.

https://www.flickr.com/photos/projectapolloarchive/albums

This is a totally safe thing to do. You definitely won't look up two hours from now and ask where your morning went.

Images: NASA

Apollo 11 launched #OTD in 1969, carrying Neil Armstrong, Michael Collins, and Buzz Aldrin to the Moon.

It was one of the most remarkable scientific collaborations in history, taking humans from Earth to the surface of another world, then returning them safely home.

Images: NASA

@the_roamer thanks!

Good evening.

@MishaVanMollusq that must be a lot to manage.

@snack Please, if there’s something you wanted to ask, or a point you were trying to make about the work she did, don’t be hesitant. Just say what you mean.

@snack Sorry, I don’t understand. Is there a point you were making, or something that wasn’t clear?

@snack Did you have a question about that?