Every once in a while， a science-fiction book， movie or TV show will feature characters who can do what we all wish: Stop time.
But is such a thing possible? Answering that question requires a deep dive into the farthest corners of physics， philosophy and human perception.
First， we have to define time. “To a physicist， it's not that mysterious，” Sean Carroll， a theoretical physicist at the California Institute of Technology， told Live Science. “Time is just a label on different parts of the universe. It tells us when something is happening.”
For him， it makes little sense to talk about stopping time. We know that a car is moving because， at different moments of time， it's at a different location in space， he said. “Motion is change with respect to time，so time itself can't move.” In other words， if time stopped， all motion would stop too.
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While sci-fi has sometimes given us protagonists who can pause time for everyone else， such situations raise a great deal of questions. “Are you stopping the air from moving?” Carroll asked. “Because if so， then you're imprisoned by the air.”
A time-stopping character would also likely be unable to see anything， he added，because light rays would no longer reach their eyeballs. “There's not really any consistent scenario in which time stops.”
So much for physics. But time is more than just something read on a clock. It's also a feeling that we have in our heads and bodies， as well as the natural rhythms of the world. Yet in those cases， time can become something subject to personal whims.
“Thinking about the subjective impression of time gets interesting，” Craig Callender， a philosopher who specializes in time at the University of California， San Diego， told Live Science.
He described a well-known psychological illusion known as “chronostasis，” in which a person places a clock at the edge of their vision and then stares at something else for a moment. Glancing back at the timepiece and focusing on the second hand will make it pause.
The question then becomes， what is the relationship between our perceptions of time and the time physicists are talking about? Callender has written a number of books that attempt to explore the connection between the two， and as yet， there isn't much consensus on a final answer.
Regarding the ultimate flow of time， Callender favors a picture “where there's nothing flowing， but the story of yourself is flowing.”
And what does he believe regarding the possibility of stopping time? “If we think of our subjective sense of time， then we can stop portions of it with chronostasis，”Callender said. “But that's probably the closest we can do.”
隔三差五，科幻書籍、電影或電視劇會著力塑造一些角色能做到我們都想做的事情：停住時間的腳步。
不過這種事情可能嗎?回答這個問題需要深入探究物理學(xué)、哲學(xué)及人類感知能力的最悠遠(yuǎn)角落。
首先，我們必須定義時間。加州理工學(xué)院理論物理學(xué)家肖恩·卡羅爾對趣味科學(xué)網(wǎng)站說：“在物理學(xué)家看來沒那么神秘。時間不過是給宇宙不同組成部分貼的標(biāo)簽。告知我們某些事情的發(fā)生節(jié)點(diǎn)。”
對他來說，談?wù)撟寱r間停止沒什么意義。他說，我們之所以知道汽車在移動，是因為在不同時刻，它處在不同的空間位置�！斑\(yùn)動是相對于時間的變化，因此時間本身是不動的�！睋Q句話說，如果時間停止，所有的運(yùn)動也會停止。
科幻作品有時為我們呈現(xiàn)了能夠讓其他人的時間暫時靜止的主人公，不過這種情況會帶來許多問題。卡羅爾問：“你要讓空氣停止流動嗎?因為如果是的話，你會被空氣禁錮。”
他還說，能讓時間停止的人很可能也看不到任何東西，因為光線不再能夠抵達(dá)他們的眼球�！捌鋵�(shí)在時間停止的情況下不存在任何連續(xù)的場景�！�
從物理學(xué)上講就是如此。不過時間不僅僅是在時鐘上標(biāo)示的東西。它還是我們頭腦和身體中的一種感覺，也是這個世界的自然節(jié)律。不過，在這些情況下，時間會成為容易受個人心血來潮影響的東西。
加利福尼亞大學(xué)圣迭戈分校專門研究時間的哲學(xué)家克雷格·卡倫德對趣味科學(xué)網(wǎng)站說：“思考對時間的主觀印象很有意思。”
他提到“停表錯覺”這種著 名的心理錯覺，具體來說是把時鐘放在視線邊緣，然后盯著別的東西看上一會兒。重新看向時鐘并盯住秒針，會感覺它停了下來。
接下來的問題成了，我們對時間的感知和物理學(xué)家談?wù)摰臅r間有什么關(guān)系?卡倫德著有大量論著，試圖探究兩者之間的關(guān)聯(lián)，不過迄今為止，尚未就最終答案達(dá)成多少共識。
關(guān)于時間最終的流逝，卡倫德贊同這樣一種描述：“什么都沒有流逝，正在流逝的只是你自己的故事。”
至于他如何看待讓時間停止的可能?卡倫德說：“想到自己對時間的主觀感覺，那么我們可以借助停表錯覺在某種程度上停住時間。不過這或許是我們所能做到的最接近于讓時間停止的事�！�
資料來源考試網(wǎng)校老師主講教材精講班課程，完整講義下載進(jìn)入個人中心>>
