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  • Of all the spectacles mankind has viewed through a telescope,


  • there are few lovelier than a spiral galaxy.


  • Majestic whirlpools of stars, they rotate in a stately and predictable dance.

    星群形成壯麗漩渦, 在其中跳著穩定恆常的舞步

  • The fact that we see many billions of them in our telescopes

    用望遠鏡便可觀察到 幾十億個以上的螺旋星系

  • tells us they are both common and stable.


  • It is perhaps surprising that it is relatively easy to understand the inner workings of these cosmic pinwheels.

    可能會嚇你一跳,要了解這些 宇宙風車的內部運作

  • By combining physical principles worked out by Sir Isaac Newton in the late 17th century,

    最容易的是依據牛頓 (Sir Isaac Newton) 在十七世紀晚期研究出的物理原則

  • with the observed amount of mass in a galaxy,


  • scientists can calculate the rates at which these galaxies rotate.


  • Using these techniques, astronomers predict how fast stars at different distances from the center of the galaxy should move.

    天文學家用此法預測與中心 不同距離的恆星移動的速度

  • Stars very close to the center move slowly.


  • That's because there is very little mass between them and the center of the galaxy to pull them along.


  • Stars a bit further away move faster,


  • because they are being pulled by all of the stars in between them and the center.

    因為它們被它們與核心之中的所有星星 一起甩動

  • As we get really far away, the stars are predicted to move slowly again.

    到很遠以後, 恆星的移動速度又會慢下來

  • Their great distance reduces gravity to a gentle tug,


  • so they move leisurely in their orbits.


  • Knowing this, scientists looked at the galaxies and measured how fast stars were moving.

    科學家觀測星系中 各恆星的軌道速度

  • To their surprise, they found that while the stars closer to the center of the galaxy behaved as predicted,

    驚訝的發現,接近星系中心的恆星 速度和預測相符

  • those further away moved far too quickly.


  • This observation was devastating to the tradtional theories of gravity and motion.

    這對傳統的重力及運動理論 帶來毀滅性打擊

  • If the stars were moving as fast as their measurement suggested,


  • galaxies should have torn themselves apart.


  • It was a crisis, and astronomers and physicists scrambled to find a mistake in their calculation.

    這是個危機,天文學家和物理學家 拼命想找出哪裡算錯了

  • Was Newton's theory of gravity wrong?


  • Was his theory of motion wrong?


  • Or was it possible that astronomers had incorrectly measured the galaxy's mass?


  • All options were investigated, and all were ruled out. Except one.

    調查並排除所有選項後 只剩下一種可能

  • Today, scientists believe that the answer lies in a previously unknown kind of matter, called dark matter.

    如今科學家相信,答案就是 一種未知的物質,稱為「暗物質」

  • This dark matter can be envisioned as a cloud which surrounds most galaxies.

    暗物質好像一團雲 籠罩了多數的星系

  • This matter is very unusual. It is affected by gravity,


  • but it is invisible to visible light and all other forms of electromagnetic radiation.

    但是看不見,也沒有 任何形式的電磁輻射

  • The name "dark matter" originates in this form of matter's inability to emit or absorb light.

    「暗物質」名稱源自這種物質 不會發出或吸收光線

  • Dark matter adds to the gravity of the galaxy


  • and explains the orbital speed of stars far from the galactic center.

    並可解釋遠離星系中心 恆星的軌道速度

  • Dark matter has not yet been directly observed,


  • but scientists believe that it is likely to be real,


  • mostly because the other options have been ruled out.


  • Using dozens of approaches, astronomers and physicists continue to search for direct evidence

    天文學家和物理學家正在嘗試 幾十種方法,想找出直接證據

  • that would prove that the dark matter hypothesis is true.


  • This question is one of the most important physics research questions of the 21st century.

    這是 21 世紀物理學 最重要的研究課題之一

Of all the spectacles mankind has viewed through a telescope,


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B2 中高級 中文 TED-Ed 星系 恆星 物質 速度 重力

【TED-Ed】 探索宇宙的奧妙:是什麼解釋了星星移動的速度 Dark matter: How does it explain a star's speed? - Don Lincoln

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