The corrections in his blog post show you the level of precision mathematicians are used to.
A regular interviewer would have left the inaccuracies as they are because it’s too tedious to go over all of them when you have a casual conversation.
Note that the modern cosmic distance ladder has multiple partially independent paths using different techniques, making it more like a DAG. The wikipedia page has a nice diagram.
tbh I would love to see full length video walking through the work that Kepler did with actual numbers, to me that part remained bit unclear. Especially how to get some quantitative values out of the analysis, considering how the eccentricity of the orbits is not really something easily visually discernible.
> In principle, using the measurements to all the planets at once could allow for some multidimensional analysis that would be more accurate than analyzing each of the planets separately
(from the blog post)
I'd also love to see this idea expanded further. Intuitively it feels like adding Venus into the calculations should dramatically help constrain the orbit of Mars, but how exactly that would work out I'm not sure.
The more I learn about Kepler the more I believe that he alone advanced humanity several decades or possibly centuries. His incredible drive to prove his own theory, and then his ability to put that theory down and to match one to the evidence, oh man. I've loved his story since the Carl Sagan Cosmos episode on him sniped me as a kid, but I get just as excited about it in videos like these (part one of this series explains how Kepler determined the orbits of the planets).
If you want to be deeply inspired, read about his life, his book Somnium, what happened to his mother. It's all so profoundly motivating.
Stephen Jay Gould said: "I am, somehow, less interested in the weight and convolutions of Einstein's brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops."
This quote really drives home the point that the overwhelmingly vast majority of scientific discovery and progress throughout history has come with humanity's entirely self-inflicted handicapping, like a V8 engine running on only 1 cylinder. Can't help but wonder what our knowledge here in 2025 would be like had we, as a species, tapped into our full potential by empowering women and people of color (to name just a few categories) earlier. You can almost see it in action with the people mentioned here as time went on.
The gravitational wave based distance measurements are really awesome because they are the only way to verify red shift distances. You can calculate how strong the wave should be based on the difference in mass between the two objects before collision and the combined object after and then calculate how strong the wave should be when it reaches earth. Right now the precision of the distances are only 10% but in the future when something like the Cosmic Explorer with 40km arms is built they will get a lot more precise.
Fantastic video, the methods are explained super clearly.
Also highly recommend David Butler's "How far away is it" video series. He covers the same methods, and spends a good amount of time discussing phenomena along the way (star life cycles, magnetars, black holes, galaxy mergers, etc).
Grant, your content is sublime, but the camera shake in this video is excruciating. It's severely eyestrain inducing. Feeling crazy that no one has mentioned it. You all must have eyes of steel.
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14 Comments
j7ake
The corrections in his blog post show you the level of precision mathematicians are used to.
A regular interviewer would have left the inaccuracies as they are because it’s too tedious to go over all of them when you have a casual conversation.
Gunax
This was very entertaining. I had a rough idea of the timeline before, but had never thought about it in this way (that is, a ladder).
dang
Related. Others?
Climbing the cosmic distance ladder: Terence Tao book announcement – https://news.ycombinator.com/item?id=24743177 – Oct 2020 (13 comments)
Terrence Tao: The Cosmic Distance Ladder – https://news.ycombinator.com/item?id=1782398 – Oct 2010 (6 comments)
jessriedel
Note that the modern cosmic distance ladder has multiple partially independent paths using different techniques, making it more like a DAG. The wikipedia page has a nice diagram.
https://en.wikipedia.org/wiki/Cosmic_distance_ladder
zokier
tbh I would love to see full length video walking through the work that Kepler did with actual numbers, to me that part remained bit unclear. Especially how to get some quantitative values out of the analysis, considering how the eccentricity of the orbits is not really something easily visually discernible.
> In principle, using the measurements to all the planets at once could allow for some multidimensional analysis that would be more accurate than analyzing each of the planets separately
(from the blog post)
I'd also love to see this idea expanded further. Intuitively it feels like adding Venus into the calculations should dramatically help constrain the orbit of Mars, but how exactly that would work out I'm not sure.
csours
They don't go into detail, but Cepheid stars are amazing
https://en.wikipedia.org/wiki/Cepheid_variable
Consensus mechanism for pulsation:
https://en.wikipedia.org/wiki/Kappa%E2%80%93mechanism
Basically the changes in ionization state, opacity, and temperature all influence each other, causing a cycle.
tonetheman
[dead]
throwawayk7h
I have a suspicion Tao's FAQ [1] is at least partially AI generated, based off the language used.
[1] https://terrytao.wordpress.com/2025/02/13/cosmic-distance-la…
erulabs
The more I learn about Kepler the more I believe that he alone advanced humanity several decades or possibly centuries. His incredible drive to prove his own theory, and then his ability to put that theory down and to match one to the evidence, oh man. I've loved his story since the Carl Sagan Cosmos episode on him sniped me as a kid, but I get just as excited about it in videos like these (part one of this series explains how Kepler determined the orbits of the planets).
If you want to be deeply inspired, read about his life, his book Somnium, what happened to his mother. It's all so profoundly motivating.
jayrot
Stephen Jay Gould said: "I am, somehow, less interested in the weight and convolutions of Einstein's brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops."
This quote really drives home the point that the overwhelmingly vast majority of scientific discovery and progress throughout history has come with humanity's entirely self-inflicted handicapping, like a V8 engine running on only 1 cylinder. Can't help but wonder what our knowledge here in 2025 would be like had we, as a species, tapped into our full potential by empowering women and people of color (to name just a few categories) earlier. You can almost see it in action with the people mentioned here as time went on.
Wonderful set of videos.
UltraSane
The gravitational wave based distance measurements are really awesome because they are the only way to verify red shift distances. You can calculate how strong the wave should be based on the difference in mass between the two objects before collision and the combined object after and then calculate how strong the wave should be when it reaches earth. Right now the precision of the distances are only 10% but in the future when something like the Cosmic Explorer with 40km arms is built they will get a lot more precise.
EcommerceFlow
The coolest YouTube videos I’ve seen in a while, even better cause I saw the eclipse last year
merek
Fantastic video, the methods are explained super clearly.
Also highly recommend David Butler's "How far away is it" video series. He covers the same methods, and spends a good amount of time discussing phenomena along the way (star life cycles, magnetars, black holes, galaxy mergers, etc).
https://www.youtube.com/watch?v=HgNJwg2GISs&list=PLpH1IDQEoE…
brendan906
Grant, your content is sublime, but the camera shake in this video is excruciating. It's severely eyestrain inducing. Feeling crazy that no one has mentioned it. You all must have eyes of steel.