Diffraction 實驗裡，因光子同時通過前後兩塊gatings，所以才有diffraction pattern。
咁對光子來說，時間是沒有意義(不可定)，還是永遠等於 零????
更新1:
Could a single photon produce diffraction pattern? Diffraction is produced by a beam of light, or a collection of photons. [Time] is not invloved in such process.
更新2:
To physics8801: 下面個兩個link太多英文字，睇到我眼花，可唔可以幫我解解，唔該。 http://www.physlink.com/Education/AskExperts/ae444.cfm http://www.sciam.com/article.cfm?chanID=sa003&articleID=5116CF53-E7F2-99DF-3B64CF41CFBB5B91