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WonderExperimental physics biography

In 1956 the physicist Chien-Shiung Wu showed that some nuclear processes do not behave the same way as their mirror image. Her experiment with radioactive cobalt-60 overturned 'parity conservation', a rule physicists had long taken for granted.

Chien-Shiung Wu

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Physicists had long assumed that the laws of nature work the same way in a mirror image, a principle called parity conservation. In 1956 the theorists Tsung-Dao Lee and Chen-Ning Yang pointed out that nobody had tested this for the weak nuclear force, which drives beta decay, a kind of radioactivity in which a nucleus gives off an electron. Wu, a leading expert on beta decay at Columbia University, cooled cobalt-60 to near absolute zero at the National Bureau of Standards and lined up its nuclei with a magnetic field. The electrons came out mostly in one direction, so the mirror version of the experiment would give a different result. Lee and Yang won the 1957 Nobel Prize in Physics; Wu was left out, although she received the first Wolf Prize in Physics in 1978.

Türkçe oku
Fizikçi Chien-Shiung Wu, 1956'da bazı atom çekirdeği süreçlerinin ayna görüntüleriyle aynı biçimde gerçekleşmediğini gösterdi. Radyoaktif kobalt-60 ile yaptığı deney, fizikçilerin uzun zamandır sorgulamadan kabul ettiği “parite korunumu” ilkesini yıktı.

Fizikçiler uzun süre doğa yasalarının ayna görüntüsünde de aynı işlediğini varsaymıştı; bu ilkeye parite korunumu denir. 1956'da kuramcı fizikçiler Tsung-Dao Lee ile Chen-Ning Yang, bunun zayıf nükleer kuvvet için hiç sınanmadığına dikkat çekti. Zayıf kuvvet, bir atom çekirdeğinin elektron saldığı bir radyoaktiflik türü olan beta bozunmasına yol açar. Columbia Üniversitesi'nde beta bozunmasının önde gelen uzmanı olan Wu, ABD Ulusal Standartlar Bürosu'nda kobalt-60'ı mutlak sıfıra çok yakın bir sıcaklığa kadar soğuttu ve çekirdekleri bir manyetik alanla aynı yöne çevirdi. Elektronlar çoğunlukla tek bir yöne fırladı; yani deneyin aynadaki karşılığı farklı bir sonuç verecekti. 1957 Nobel Fizik Ödülü Lee ile Yang'a verildi; Wu ödülün dışında kaldı, ama 1978'de ilk Wolf Fizik Ödülü'nü aldı.

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Background reading: Chien-Shiung Wu
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