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vgr's profile
Venkatesh Rao
Venkatesh Rao
Venkatesh Rao
@vgr

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Venkatesh Rao

@vgr

Conversational account. For work follow @ribbonfarm, @breaking_smart, @artofgig. Tweets are 90% vacuous views, apathetically held. Mediocritopian. IKEA builder.

Los Angeles, CA
venkateshrao.com
Joined August 2007

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    1. Venkatesh Rao‏ @vgr Aug 9
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      Something I’ve been thinking about. The earliest telescopes after Galileo were often very high f numbers to mitigate chromatic aberration because they didn’t know how to make achromatic lenses and reflectors hadn’t been invented. So very long tubes for small apertures.pic.twitter.com/ZSA865fVJH

      4 replies 17 retweets 84 likes
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    2. Venkatesh Rao‏ @vgr Aug 9
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      So long tubes, flatter lenses. Johannes Hevallius made the 46m long telescope in the engraving above with an objective that looks like it’s less than 6-8” in 1673. Today you can get more power with a tube less than 0.5m long. A 100x reduction in tube length.pic.twitter.com/XJz0Q7CXIl

      1 reply 2 retweets 25 likes
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      Venkatesh Rao‏ @vgr Aug 9
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      This is the magic of folded optics. High quality glass of various sorts and an artful mix of mirrors and lenses gets you this 100x improvement.

      2:12 PM - 9 Aug 2020
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      • Tera Adams Sarah McManus airborne caipira Anita Cryptberg Arlyn Culwick Mike Abundo Billy Smith Jim Andrakakis Vinay Gupta
      1 reply 1 retweet 20 likes
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        2. Venkatesh Rao‏ @vgr Aug 9
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          Modern research scopes do even better. When I was getting into astronomy in the 80s, the Mt. Palomar 6m telescope was the largest. A traditional reflector. Now we’re on our way to 30 thanks to interferometric techniques that use segmented hexagonal mirrors https://www.forbes.com/sites/startswithabang/2017/01/25/worlds-largest-telescope-will-revolutionize-the-future-of-astronomy/#233260d8516b …pic.twitter.com/jZtxqKuBfE

          1 reply 2 retweets 18 likes
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        3. Venkatesh Rao‏ @vgr Aug 9
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          These are way more powerful than Hubble but being terrestrial they are limited by atmospheric turbulence etc. But interferometric methods even buy you mitigation for that. With adaptive optics you can probe turbulence with a laser and adjust your segmented mirror to compensate.

          1 reply 0 retweets 11 likes
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        4. Venkatesh Rao‏ @vgr Aug 9
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          Of course, it’s even better if you can put such advanced telescopes in space, and create synthetic apertures out of individual physical optical elements 100s of miles apart. Part of my PhD work 20y ago was on scheduling algorithms for such “large baseline space interferometers”

          2 replies 0 retweets 18 likes
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        5. Venkatesh Rao‏ @vgr Aug 9
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          The largest of such concepts that had a shot at being launched was the TPF (Terrestrial Planet Finder), canceled in 2011 https://en.wikipedia.org/wiki/Terrestrial_Planet_Finder …

          1 reply 0 retweets 5 likes
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        6. Venkatesh Rao‏ @vgr Aug 9
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          It’s a fascinating journey of a) shrinking constructions b) coming up with new constructions. There’s probably a Moore’s law of telescopic power. I think microscopes have evolved more radically between Leeuwenhoek and modern atomic-force microscopes, but I stan telescopes

          1 reply 0 retweets 14 likes
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        7. Venkatesh Rao‏ @vgr Aug 9
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          The state of the art for amateurs is really large Dobsonian telescopes. This guy built a 70“er... creeping close to world record pro telescopes like Mt. Wilson 100” instrument which was the record holder until 1949 🤯https://blog.nationalgeographic.org/2013/11/08/worlds-largest-backyard-telescope/ …

          1 reply 2 retweets 20 likes
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        8. Venkatesh Rao‏ @vgr Aug 9
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          Biggest is not best of course. The best we’re likely to see in our lifetimes is the Hubbke successor, the James Webb space telescope, dur to launch next year after many slippages. I expect it will slip again due to covid. https://en.wikipedia.org/wiki/James_Webb_Space_Telescope …

          2 replies 0 retweets 12 likes
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        9. Venkatesh Rao‏ @vgr Aug 9
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          There’s also radio astronomy and stuff of course but there’s something special about the evolution of visible spectrum telescopes. They are the extension of our eyes. We will likely never make it past the Great Filter but we will likely be able to see past it within a century.

          1 reply 0 retweets 8 likes
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        10. Venkatesh Rao‏ @vgr Aug 9
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          I’m betting in less than 100 years if civilization does not collapse we’ll have surface imagery of exosolar terrestrial planets. Concepts for these are already being researched. It’ll be the greatest stretching of human consciousness ever.

          1 reply 3 retweets 20 likes
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        11. Venkatesh Rao‏ @vgr Aug 9
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          I didn’t realize this until a few years ago, but we can already image stars other than the sun with enough resolution to see discs instead of point sources. Only supergiants for now. But damn 🤯 https://astrobob.areavoices.com/2014/06/06/can-we-really-see-other-stars-as-true-disks-you-betcha/ …pic.twitter.com/hunvTQpa01

          1 reply 4 retweets 25 likes
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        12. Venkatesh Rao‏ @vgr Aug 9
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          Think how mind-blowing this is. For Galileo it was a real shock to see the phases of Venus and Jupiter with satellites. That stuff has gotten a bit meh now due to space missions, but imagine how huge it was in the 1600s to see discs other than the sun and moon.

          2 replies 0 retweets 15 likes
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        13. Venkatesh Rao‏ @vgr Aug 9
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          You can still get Galilean soul-stirring goosebumps by looking at Jupiter or Saturn live through a small hobby scope. It’s not as dramatic as Cassini or Juno mission photos, but otoh you’re seeing LIVE images. Photons hitting your eyes are literally from Jupiter/Saturn.

          1 reply 2 retweets 13 likes
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        14. Venkatesh Rao‏ @vgr Aug 9
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          It sometimes makes me very sad that so much of the universe is read-only. You can see it but not reasonably expect to get to it. Still the fact that we can read so much more than we can write creates a kind of life poetry out of our instruments.

          3 replies 7 retweets 30 likes
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        15. Venkatesh Rao‏ @vgr Aug 9
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          “Ah, but a man’s teach should exceed his grasp, else what’s a heaven for?” — Robert Browning. This is not a universal sensibility though. One of the weirdest life experiences for me is that there are people who are simply completely disinterested in things they can’t act on.

          2 replies 2 retweets 19 likes
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        16. Venkatesh Rao‏ @vgr Aug 9
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          Sherlock Holmes was one. He didn’t know that the earth revolves around the sun, and when Watson tells him, he days he’ll do his best to forget the fact. There’s many people like this. Agency or nothing. The read-only universe might as well not exist.

          2 replies 2 retweets 16 likes
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        17. Venkatesh Rao‏ @vgr Aug 9
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          ‘The purpose of humanity is to build bigger telescopes’ isn’t a bad philosophical axiom. It’s certainly more meaningful than ‘build bigger computers’ or ‘create more material comfort’ or ‘relieve more suffering’ imo. Ground species purpose in boundary conditions of consciousness.

          2 replies 4 retweets 20 likes
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        18. Venkatesh Rao‏ @vgr Aug 9
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          Venkatesh Rao Retweeted peppermint bmo

          Damn. TIL NRO spy satellites are probably more powerful than Hubble in raw optical terms though designed for spying on your phone rather than distant galaxieshttps://twitter.com/eigenrobot/status/1292596559184420864?s=21 …

          Venkatesh Rao added,

          peppermint bmo @eigenrobot
          Replying to @vgr @NatReconOfc
          🤷‍♂️ I never enjoyed optics pic.twitter.com/VPwRji336U
          3 replies 3 retweets 15 likes
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        19. End of conversation

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