8 ms·
Part two of Grant Sanderson's video with Terry Tao on the cosmic distance ladder
- j7ake 2y agoThe 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.
- maxnoe 2y agohttps://terrytao.wordpress.com/2025/02/13/cosmic-distance-ladder-video-with-grant-sanderson-3blue1brown-commentary-and-corrections/ https://terrytao.wordpress.com/2025/02/13/cosmic-distance-la...
- pavon 2y agoNote this blog post also has links to both parts of the video. (Our corporate firewall annoyingly blocks a bunch of new gTLDs, including xyz).
- hakaneskici 2y agoAs a side question, what's the rationale for this? Is there a list of nsfw gTLDs?
- pxeger1 2y ago.xyz (alongside some others like .top, .biz?) in particular have a reputation for phishing/malware/etc., I think because they’re among the cheapest to register.
- ziddoap 2y agoThe funny thing is, the number 1 & 2 spam/phishing/malware domains that hit my company's mail server is gmail.com and outlook.com, followed by random .com domains. My domain block list is approaching 1,000 domains and I don't think I have a single .xyz or .biz in there. There's a few .top. But the overwhelming majority is .com.
- daedrdev 2y agoI feel like .zip and .mov gTLDs are more understandable to have blocked
- mcpherrinm 2y ago.top is definitely a shady spot. They’re inexpensive and not very responsive to abuse reports - https://www.icann.org/uploads/compliance_notice/attachment/1225/hedlund-to-wenxia-16jul24.pdf https://www.icann.org/uploads/compliance_notice/attachment/1... .xyz though I mostly associate with abc.xyz, the investor relations page for Alphabet.
- ericjmorey 2y agoDirect link to video: https://youtu.be/hFMaT9oRbs4 https://youtu.be/hFMaT9oRbs4 Announcement post on bsky: https://bsky.app/profile/3blue1brown.com/post/3liu3ybnowk2w https://bsky.app/profile/3blue1brown.com/post/3liu3ybnowk2w
- Gunax 2y agoThis 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 2y agoRelated. Others? Climbing the cosmic distance ladder: Terence Tao book announcement - https://news.ycombinator.com/item?id=24743177 https://news.ycombinator.com/item?id=24743177 - Oct 2020 (13 comments) Terrence Tao: The Cosmic Distance Ladder - https://news.ycombinator.com/item?id=1782398 https://news.ycombinator.com/item?id=1782398 - Oct 2010 (6 comments)
- jessriedel 2y agoNote 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 https://en.wikipedia.org/wiki/Cosmic_distance_ladder
- csours 2y agoCosmic distance scaffold?
- zokier 2y agotbh 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.
- asattarmd 2y agoThere are videos by Welch labs that go into detail about what he did: https://www.youtube.com/watch?v=Phscjl0u6TI https://www.youtube.com/watch?v=Phscjl0u6TI https://www.youtube.com/watch?v=MprJN5teQxc https://www.youtube.com/watch?v=MprJN5teQxc
- csours 2y agoThey don't go into detail, but Cepheid stars are amazing https://en.wikipedia.org/wiki/Cepheid_variable https://en.wikipedia.org/wiki/Cepheid_variable Consensus mechanism for pulsation: https://en.wikipedia.org/wiki/Kappa%E2%80%93mechanism 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.
- mithrene 2y agoI’m an asteroseismologist and really pleased to see a link to the Kappa mechanism. I usually teach it as a heat engine concept, and it’s applicable to most stars in the classical instability strip. Another class of variables that aren’t mentioned are the solar like oscillators, driven by convection on the surface of the star. https://en.m.wikipedia.org/wiki/Solar-like_oscillations https://en.m.wikipedia.org/wiki/Solar-like_oscillations Our sun is one such example and has a period of 5 minutes!
- csours 2y agoNeat! There is no scientifically imaginable form of life that could evolve or survive in or on stars. (So to be clear, this is all a flight of fancy) Anthropic bias suggests that liquid water and carbon are essential to life. BUT! I do think it's fun to imagine what assumptions a solarian biologist would make about the world. What would Solarian Bias look like? What might be easier for a solarian physicist to understand? Would they have a different view of gravity? They would start with a better understanding of astronomy than us, assuming they could make observations of the 'sky'; As the band Mogwai says "The Sun Smells Too Loud". All manner of EM observations would be more obscure (or rather their instruments would be dazzled). They would have to find some kind of Spot on the Sun where it's dark enough to see out. Maybe they could learn to ride the flares! They would definitely start with a better version of the atom - there's no way to ignore fusion and fission if you live on the sun! Or! What if it were possible to make observations of gravity from the surface of a neutron star. We have math and observations from here that make sense to us, but perhaps there's something that would just 'click' if you lived next to one. Anyway, thanks for coming to my TEDx talk.
- tonetheman 2y ago[dead]
- throwawayk7h 2y agoI 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-ladder-video-with-grant-sanderson-3blue1brown-commentary-and-corrections/ https://terrytao.wordpress.com/2025/02/13/cosmic-distance-la...
- dado3212 2y agoAny specific parts?
- Folcon 2y agoConsidering the author in question, it may be equally accurate to say that AI generated content has been fed a lot of his writing as training data.
- NotYourLawyer 2y agoNothing jumps out at me.
- UltraSane 2y agoTao is so prolific LLMs have been trained on a LOT of his writings.
- prawn 2y agoIt's been a while since I read his writing, but I skimmed and didn't see anything that sounded unlike him. He writes with a very neutral tone. It did make me wonder though how effectively you could lean on AI to flesh out a list of questions, but I think in this case he has the expertise to write each response quickly and he'd be conscious that this is overall a piece of content doing properly.
- djmips 2y agoI read it and it sounded like 100% all natural organic intelligence generated.
- erulabs 2y agoThe 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.
- anamexis 2y agoBesides the Cosmos episode, do you have any recommendations on learning more?
- ziotom78 2y ago"Blind watchers of the sky" is one of the best presentations of Kepler's and Galileo's oeuvre I have ever read. (I am an astrophysicist, but this book can be read by non-specialists too.)
- simpaticoder 2y agoI agree, and if you want to learn more about him I highly recommend this two-part series: https://www.youtube.com/watch?v=Phscjl0u6TI https://www.youtube.com/watch?v=Phscjl0u6TI What is particularly wild is that Kepler had to wait for Tycho Brahe to die to steal his data before Brahe's heirs got their hands on it. Not only that, but Kepler was very close to making epicycles work but he was not satisfied with the (relatively small) predictive errors. So, if not for Kepler's combination of...flexible morality and unsatified nature, physics as we know it would have been delayed or perhaps never discovered at all!
- z3phyr 2y agoThe important thing is to be self aware enough to clearly differentiate between good and bad, even when doing bad stuff sometimes could be beneficial.
- jayrot 2y agoStephen 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.
- istjohn 2y agoI wonder. I'm against wealth inequality, but for thousands of years, the human labor required to feed, clothe, and shelter a family wouldn't have allowed anyone to learn, preserve, and advance human knowledge without the labor of many being exploited one way or another by an elite few. That's not to justify anything or argue against egalitarianism today.
- District5524 2y agoA great point! I beleive today the main problem is no longer the amount of human labor needed to feed or clothe, but to have access to those universities/labs/companies that have the necessary resources to enable meaningful research that humanity values. Costs of creating food and clothe have plummeted - this is good from any possible point of view, and clearly shows we do no longer "need" inequlity from these perspectives. However, access to human institutions does not follow the same democratization and pricefall. In several fields (space, medical and material sciences), advances we yearn for require lots of capital/military power. In many fields, innovations are tied to huge amounts of money to be spent (mostly accessible only in one particular capital market of the world). But even in "cheaper" fields (like mathematics, economics etc.) simply being heard requires working in prestiguous universities. And many of those have no choice but to select and hire people based on their previous work or their financial capabilities. Thus, reinforcing the same stratification as we've seen with food and clothing, and slowing the process of finding the right bright minds to do what they excel at in greater numbers. It's quite unlikely we will solve any major part of this social problem before 2086 (or any projected population peak)... People seem to be still stuck in celebrity culture in politics and everywhere.
- UltraSane 2y agoThe 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 2y agoThe coolest YouTube videos I’ve seen in a while, even better cause I saw the eclipse last year
- merek 2y agoFantastic 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=PLpH1IDQEoE8QWWTnWG5cK4ePCqg9W2608 https://www.youtube.com/watch?v=HgNJwg2GISs&list=PLpH1IDQEoE...
- udkl 2y agoAnyone looking for additional recommendations : the popular "A short history of nearly everything" by Bill Bryson covers in a historical context how these planetary distances were calculated
- brendan906 2y ago[flagged]
- captainmuon 2y agoThe cosmic distance ladder is fascinating. At university, we had an astrophysics professor who said his secret worry is that something was broken about the ladder. If you have a wrong assumption close to the bottom, then the error would compound the more you go to larger distances. And you would not just have quantitative errors, such as mismeasured distances, but qualitative errors. The objects you think you are looking at might be something completely different. It is unlikely because the picture we have is consistent. But it could be also wrong and still consistent. The big open questions such as dark matter / dark energy could be the only hints we have that something is wrong. I'm an experimental particle physicist by training and know that feeling. We never see the particles directly, but reconstruct them in a complex chain. Hits in a detector become tracks, tracks are assigned to particles according to our expectation of how those particles behave. Bunches of tracks are interpreted as decaying heavier particle. Sometimes I wonder if we missed something important in the early days of quantum mechanics and particle physics, and some of the things we think we are investigating don't actually exist, or are subtly different than we think. But we look at the data though our lens, and see what we are expecting to see. My gut feeling says everything is consistent, and experiments match the theory so incredibly closely that it can't be a coincidence, but I don't think there is a mathematical proof. It could be that our theory is just so flexible that it lets us see Higgs particles and top quarks, even though the actual entities are something different. Like when people thought planets move in epicycles. I know it is likely nonsense, but it is what motivated me every now and then to go back and revisit the basics of our field, like how is a particle state defined in QM, how does it interact with the experiment, how do we reconstruct larger objects, and so on.
- DiogenesKynikos 2y agoLuckily, the bottom rung of the distance ladder, parallax, is only dependent on geometry, and is therefore completely solid. With the Gaia space telescope, there are now parallax measurements almost to the center of the Milky Way. Having parallax measurements to that distance helps to build multiple versions of the next rung in the ladder (such as Cepheids and the tip of the red giant branch).
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- vmilner 2y agoThis is so good. It reminded me of the foreword to Simon Jenkins’ “A short history of England” when he says that breadth of knowledge should come before depth (ie knowing about the details of Henry VIII or Charles I beheading fits better after a solid grounding in the overall scope of English history) Similarly I now have a much clearer idea of how (say) the main sequence of star formation and standard candle stars fit into the historical picture.