在http://en.wikipedia.org里，我看到有关时间的定义是这样写的（中文翻译在后面）：Time is a basic component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects. Time has been a major subject of religion, philosophy, and science, but defining time in a non-controversial manner applicable to all fields of study has consistently eluded the greatest scholars.

In physics and other sciences, time is considered one of the few fundamental quantities.^[2] Time is used to define other quantites – such as velocity – and defining time in terms of such quantities would result in circularity of definition.^[3] An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, has a high utility value in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called space-time brings the nature of time into association with related questions into the nature of space, questions that have their roots in the works of early students of natural philosophy.

Among philosophers, there are two distinct viewpoints on time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. Sir Isaac Newton subscribed to this realist view, and hence it is sometimes referred to as Newtonian time.^[4][5] The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz^[6] and Immanuel Kant,^[7][8] holds that time is not itself something and therefore is not to be measured.

Temporal measurement has occupied scientists and technologists, and was a prime motivation in navigation and astronomy. Periodic events and periodic motion have long served as standards for units of time. Examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the international unit of time, the second, is defined as a certain number of hyperfine transitions in caesium atoms (see below). Time is also of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in human lifespans.

为了能够容易理解，我在翻译时做了简化，希望没有曲解。可是万一我有疏忽，那就当作是本人无能，请见谅。

“时间是用来测量有序事件、比较事件持续性、和间歇性、及定量物体运动。时间是宗教、哲学、和科学里的一个主要题目，而且，能够给出一个在各个领域都能接受的时间定义让人类精英煞费苦心。

在物理和其它科学，时间被认为是几个基本定量之一。时间用来定义其它定量 – 如速度 – 并且用其它定量可以反过来定义时间。时间的运算定义，例如：循环往复运动物体中有一个数的概念，比如秒，在高级实验和生活中都具有很高的应用价值。在时间的运算定义中，把时间是否存在先放在一边，仅仅是考虑运动次数。对于单一连续体的观察，又引进了一个相关问题-空间概念。空间在早期自然哲学中也是一个热门话题。

在哲学上，对于时间有两种观点。一种观点认为时间是宇宙中的一个基本结构，是事件顺序发生的坐标。牛顿阐述过这样的观点，所以，这种观点也被认为是纽顿时间。另一观点则持相反的观点：认为根本就没有时间-空间这样一个盒子来装载物体的运动，时间-空间-数都是人为定义的。弗里德里希·莱布尼茨和伊曼努尔·康德认为时间本身是不存在的并且也不被测量。

测量时间的概念被当今科学家和技术人员广泛认可。时间概念在航行和太空方面极为重要。周期事件和运动被用来当做时间单位。秒被认做是国际时间单位。时间具有社会意义，经济价值，和个人人生价值。”

是呀，无论时间本身是不是存在，但是作为衡量事件次序的单位，时间对于人具有特别重要的意义。例如：寿命，从生到死的过程。人也许正是由于对生命的珍惜，所以才对时间的含意格外关注。

人人都知道：过去是现在的积累，现在是过去的延续，未来是现在的希望，现在是未来的过去。可是，我有一个问题：如何定义“现在”（Now）？如果用秒来测量时间的一个区间，那么时间的长度是可以测量的，但是，谁能找到“现在”？在任何您认为是“现在”的时刻，那个“现在”都不是“现在”。其实，佛祖早就发现了这个问题。从另外一个角度看，如果有时间，并且是连续的，那么，在测量任何一点时所使用的时间都会使得“现在”无法确定。如果“现在”无法确定和测量，那么“现在”也就没有意义了。没有了现在，那么过去和未来也就不好用现在来定义了。当然，我们可以定义昨天为今天的过去；明天为今天的将来。以及，我们可以定义前一个小时，后一个小时等等。也就是说，我们无法找到“现在”，但是我们可以找到“现在”所处的范围。这个范围可以是非常的渺小，甚至是趋于无穷小。这样在生活上，我们也就可以使用一个时间区间来代替“现在”。

从上面的论述，也许可以认为“现在”是不存在的，只是一个人为设计的高明计量方法。如果“现在”不存在，那么时间本事也可能是不存在的。时间、空间可能和数学、艺术一样都是人类智慧设计出来的“道”。是解释和感受世界的手段。

时间对于我们人来说是自然存在、无可争议的事实。真的是这样吗？时间如果不存在您会做何感想？