Skip to content
By using Twitter’s services you agree to our Cookies Use. We and our partners operate globally and use cookies, including for analytics, personalisation, and ads.
  • Home Home Home, current page.
  • About

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @
  • Language: English
    • Bahasa Indonesia
    • Bahasa Melayu
    • Català
    • Čeština
    • Dansk
    • Deutsch
    • English UK
    • Español
    • Filipino
    • Français
    • Hrvatski
    • Italiano
    • Magyar
    • Nederlands
    • Norsk
    • Polski
    • Português
    • Română
    • Slovenčina
    • Suomi
    • Svenska
    • Tiếng Việt
    • Türkçe
    • Ελληνικά
    • Български език
    • Русский
    • Српски
    • Українська мова
    • עִבְרִית
    • العربية
    • فارسی
    • मराठी
    • हिन्दी
    • বাংলা
    • ગુજરાતી
    • தமிழ்
    • ಕನ್ನಡ
    • ภาษาไทย
    • 한국어
    • 日本語
    • 简体中文
    • 繁體中文
  • Have an account? Log in
    Have an account?
    · Forgot password?

    New to Twitter?
    Sign up
michael_nielsen's profile
michael_nielsen
michael_nielsen
michael_nielsen
@michael_nielsen

Tweets

michael_nielsen

@michael_nielsen

Searching for the numinous. Co-purveyor of https://quantum.country/ 

San Francisco, CA
michaelnielsen.org
Joined July 2008

Tweets

  • © 2019 Twitter
  • About
  • Help Center
  • Terms
  • Privacy policy
  • Imprint
  • Cookies
  • Ads info
Dismiss
Previous
Next

Go to a person's profile

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @

Promote this Tweet

Block

  • Tweet with a location

    You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more

    Your lists

    Create a new list


    Under 100 characters, optional

    Privacy

    Copy link to Tweet

    Embed this Tweet

    Embed this Video

    Add this Tweet to your website by copying the code below. Learn more

    Add this video to your website by copying the code below. Learn more

    Hmm, there was a problem reaching the server.

    By embedding Twitter content in your website or app, you are agreeing to the Twitter Developer Agreement and Developer Policy.

    Preview

    Why you're seeing this ad

    Log in to Twitter

    · Forgot password?
    Don't have an account? Sign up »

    Sign up for Twitter

    Not on Twitter? Sign up, tune into the things you care about, and get updates as they happen.

    Sign up
    Have an account? Log in »

    Two-way (sending and receiving) short codes:

    Country Code For customers of
    United States 40404 (any)
    Canada 21212 (any)
    United Kingdom 86444 Vodafone, Orange, 3, O2
    Brazil 40404 Nextel, TIM
    Haiti 40404 Digicel, Voila
    Ireland 51210 Vodafone, O2
    India 53000 Bharti Airtel, Videocon, Reliance
    Indonesia 89887 AXIS, 3, Telkomsel, Indosat, XL Axiata
    Italy 4880804 Wind
    3424486444 Vodafone
    » See SMS short codes for other countries

    Confirmation

     

    Welcome home!

    This timeline is where you’ll spend most of your time, getting instant updates about what matters to you.

    Tweets not working for you?

    Hover over the profile pic and click the Following button to unfollow any account.

    Say a lot with a little

    When you see a Tweet you love, tap the heart — it lets the person who wrote it know you shared the love.

    Spread the word

    The fastest way to share someone else’s Tweet with your followers is with a Retweet. Tap the icon to send it instantly.

    Join the conversation

    Add your thoughts about any Tweet with a Reply. Find a topic you’re passionate about, and jump right in.

    Learn the latest

    Get instant insight into what people are talking about now.

    Get more of what you love

    Follow more accounts to get instant updates about topics you care about.

    Find what's happening

    See the latest conversations about any topic instantly.

    Never miss a Moment

    Catch up instantly on the best stories happening as they unfold.

    1. michael_nielsen‏ @michael_nielsen Apr 9
      • Report Tweet

      Most scientific & mathematical disciplines I know of have results that educated outsiders can appreciate and go "wow" after a brief acquaintance, even without understanding the details. Does anyone know of such a result for category theory?

      56 replies 25 retweets 278 likes
      Show this thread
    2. michael_nielsen‏ @michael_nielsen Apr 9
      • Report Tweet

      Note the word "brief" here. This request is easily fulfilled for fields ranging from linguistics to algebraic geometry to general relativity to molecular biology. Curious if there is such a result for category theory.

      3 replies 0 retweets 16 likes
      Show this thread
    3. michael_nielsen‏ @michael_nielsen Apr 9
      • Report Tweet

      Eg general relativity: gravitational lensing, the existence of black holes, the fact the planets are really going in "straight lines" (geodesics) around the sun, in the right geometry... each has a great 2-minute explanation. (And dozens of other phenomena, too.)

      5 replies 0 retweets 29 likes
      Show this thread
    4. michael_nielsen‏ @michael_nielsen Apr 9
      • Report Tweet

      The one thing I know of that sort of fits - the definition of the tensor product of modules in terms of a universal mapping principle is clearly inspired by category-theoretic ideas (and is very nice). But not a big "wow", & needs quite a bit of background to be "brief"

      2 replies 0 retweets 19 likes
      Show this thread
    5. michael_nielsen‏ @michael_nielsen Apr 9
      • Report Tweet

      An example, from general relativity: "If you're on a spaceship, and carry a really good clock down near to the event horizon of a black hole, and come back, you'll find that time has slowed down relative to people who didn't go on the trip". Dwell on that, & it's mindblowing.

      1 reply 3 retweets 15 likes
      Show this thread
      michael_nielsen‏ @michael_nielsen Apr 9
      • Report Tweet

      Or an example from complex analysis: suppose you have a function that's analytic everywhere in the complex plane. Than integrate it round a closed curve in the complex plane, and you'll find that you get 0. Again, it's mindblowing!

      6:24 PM - 9 Apr 2019
      • 32 Likes
      • Tequehead Zhu JQ davidad  🎇 John @ Khipu.ai Salvo R. daniel burfoot Brian who survived a powerline
      2 replies 0 retweets 32 likes
        1. michael_nielsen‏ @michael_nielsen Apr 9
          • Report Tweet

          For the last, you need to know what analytic means: (f(z+epsilon)-f(z))/epsilon approaches a constant limit as epsilon approaches 0, everywhere. Intuitively, the key thing going beyond real differentiability is that epsilon can approach 0 from any direction in the complex plane

          2 replies 0 retweets 19 likes
          Show this thread
          Thanks. Twitter will use this to make your timeline better. Undo
          Undo
        1. New conversation
        2. Liu Yao‏ @liuyao12 Apr 9
          • Report Tweet
          Replying to @michael_nielsen

          Mindblowing or not really depends on one’s preconception in the field. In this case integral of a vector field around a closed loop. On a related note, I find it mindblowing that an analytic function is fully determined (or encoded) by its values inside any tiny neighborhood.

          1 reply 0 retweets 1 like
        3. Timothy Gowers‏ @wtgowers Apr 10
          • Report Tweet
          Replying to @liuyao12 @michael_nielsen

          I was about to make a similar comment to the first part of this one. Another result one might choose is that if a function is complex-differentiable once, then it is complex-differentiable twice (and hence infinitely many times).

          0 replies 0 retweets 3 likes
        4. End of conversation

      Loading seems to be taking a while.

      Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.

        Promoted Tweet

        false

        • © 2019 Twitter
        • About
        • Help Center
        • Terms
        • Privacy policy
        • Imprint
        • Cookies
        • Ads info