Placeholder Image

字幕表 動画を再生する

  • In the late 19-teens, Albert Einstein had a new hammer, and he was in search of nails

  • to hit.

  • He had just developed a new and more powerful mathematical description of gravity , and

  • was using it to make predictions willy-nilly.

  • First, Einstein checked that his new description matched up with the previous state-of-the-art

  • description of gravity, newton’s law, for situations where newton’s law agreed with

  • experiments.

  • And it did.

  • So far so good.

  • Then Einstein plugged in the orbit of Mercury and got a prediction that correctly matched

  • the experimental observations of the day; observations which had an anomaly that couldn’t

  • be explained with Newton’s law of gravitation.

  • He plugged in starlight passing by the sun and got a prediction that it should bend because

  • of the sun’s gravity; this was later confirmed.

  • He plugged in starlight leaving large stars and got a prediction that the spectrum of

  • the light should be redshifted as it climbs out of the gravity well; this was later confirmed.

  • He plugged in empty space and got a prediction that waves of gravitation should propagate

  • through it; this, too, was later confirmed.

  • And he plugged in the universe and got a prediction that it should be static and unchanging.

  • Which was wrong.

  • Now, the general understanding at the time was that the universe didn’t expand or contract,

  • and while there were starting to be rumors that distant nebulas were consistently moving

  • away from us , Einstein was firmly in thestatic universecamp.

  • And it just so happened that when Einstein did his calculation about the universe, he

  • made a small but significant technical mistake that implied that the universe couldn’t

  • be expanding or contracting.

  • I suspect Einstein probably didn’t catch the mistake for two reasons: because tensor

  • calculus is hard and annoyingly subtle, and because he agreed with the result so had no

  • reason to question it.

  • This is all the more significant because the mistake ultimately meant that his equations

  • predicted the universe couldn’t have anything in it at all, and Einstein had to find a totally

  • different clever mathematical trick in order for his equations to describe a universe that

  • did have stuff in it in spite of his mistaken calculation.

  • Anyway a few years later, Russian physicist Alexander Friedmann plugged the universe into

  • Einstein’s equations, and he didn’t make the mistake Einstein did.

  • He got a prediction that the universe could either be expanding, or contracting, or static,

  • depending on how much stuff there was in it and the balance of matter and energy.

  • But Einstein still didn’t realize that he had made a mistake: instead, he published

  • a criticism of Friedmann’s work, justifying his critique with the same erroneous calculation

  • as before.

  • So Friedmann wrote Einstein a private letter, graciously (but firmly) explaining to Einstein

  • the correct calculation, and (again graciously) asking Einstein to either show him where HE

  • was wrong, or publish a correction.

  • And Einstein eventually saw that Friedmann was right - so he admitted it and published

  • a retraction of his previous criticism.

  • Turns out the equations of general relativity could describe an expanding or contracting

  • universe after all.

  • The scientific end to this story is that Friedmann died before the conclusive experimental data

  • came in and showed that the universe is expanding, so he never knew which possible outcome of

  • his equation was right.

  • And Einstein died before the conclusive experimental evidence came in that showed that the mathematical

  • trick he had used to adjust for his mistake turned out to be super useful and is now used

  • to describe dark energy.

  • So Einstein was famously upset about the whole episode; the story is typically written to

  • suggest that he simply regretted being wrong.

  • And maybe that’s the truth.

  • But speaking as a physicist - and to be clear, this is purely my own personal speculation

  • - I kind of wonder if Einstein also was kicking himself in the pants because if he hadn’t

  • made that silly math error, maybe he could have arrived, years earlier, at the same equations

  • as Friedmann (and which are now called the Friedmann equations, and are the foundation

  • of our modern understanding of the large-scale structure of the universe).

  • But I’m not entirely sure he would have been able to do what Friedmann did - because

  • all people, even scientists, have biases, and biases tend to be held so strongly and

  • so deeply that they not only blind us to alternatives, they blind us to their existence.

  • The beauty of keeping an open, rational and scientific mindset is that when one of your

  • biases is wrong, youre more willing to look at the evidence, see that youre wrong,

  • and admit it.

  • But that’s really hard to do, even - or maybe especially - for somebody like Einstein.

  • And I wonder if Einstein would have been able to see past his bias about the static nature

  • of the universe without outside help.

  • Einstein, like all of us, was human after all.

  • What we can take from Einstein’s actions in this story is this : we can understand

  • that we can be wrong, and when we are, graciously admit it.

  • This video is sponsored by a platform that’s all about understanding when youre wrong

  • and trying to improve: of course, it’s Brilliant.org.

  • Brilliant has courses and quizzes and puzzles to master logic, math and science skills in

  • whatever size dose you want, and theyre sporting a new look.

  • What I like about their redesign is that it’s not just cosmetic - the interactive quizzes

  • and problems are getting more and more interactive and animated!

  • Do you know what the angles on the outside of a pentagon add up to?

  • What about why solar panels are tilted, and how you pick the right angle?

  • For something a little more in-depth, I’d recommend theirmathematical fundamentals

  • course.

  • To sign up for free, go to brilliant.org/minutephysics - that lets Brilliant know you came from here,

  • plus Brilliant is offering 20% off of a premium subscription to the first 200 people to go

  • to that link.

  • Again, that’s brilliant.org/minutephysics, and thanks to brilliant for supporting MinutePhysics.

In the late 19-teens, Albert Einstein had a new hammer, and he was in search of nails

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B2 中上級

アインシュタインを正した男 (The Man Who Corrected Einstein)

  • 0 0
    林宜悉 に公開 2021 年 01 月 14 日
動画の中の単語