Pictured: a clock, one of the most notorious devices used to measure time.
I read this article in Discover magazine a while ago, but forgot about it until it was posted on Digg. I think it's a pretty interesting subject, perhaps worth discussing; but Digg is a terrible place to try and discuss anything. So I came here... aren't you glad? Anyway, here it is: Teh Article.
The trouble with time started a century ago, when Einstein’s special and general theories of relativity demolished the idea of time as a universal constant. One consequence is that the past, present, and future are not absolutes. Einstein’s theories also opened a rift in physics because the rules of general relativity (which describe gravity and the large-scale structure of the cosmos) seem incompatible with those of quantum physics (which govern the realm of the tiny). Some four decades ago, the renowned physicist John Wheeler, then at Princeton, and the late Bryce DeWitt, then at the University of North Carolina, developed an extraordinary equation that provides a possible framework for unifying relativity and quantum mechanics. But the Wheeler-*DeWitt equation has always been controversial, in part because it adds yet another, even more baffling twist to our understanding of time.
“One finds that time just disappears from the Wheeler-DeWitt equation,” says Carlo Rovelli, a physicist at the University of the Mediterranean in Marseille, France. “It is an issue that many theorists have puzzled about. It may be that the best way to think about quantum reality is to give up the notion of time—that the fundamental description of the universe must be timeless.”
No one has yet succeeded in using the Wheeler-DeWitt equation to integrate quantum theory with general relativity. Nevertheless, a sizable minority of physicists, Rovelli included, believe that any successful merger of the two great masterpieces of 20th-century physics will inevitably describe a universe in which, ultimately, there is no time.
First of all, I feel a need to point out the intense irony of the phrase "The trouble with time started a century ago". Moving on, I think this is probably one of the most important parts of the article:
Most of us tend to think of time the way Newton did: “Absolute, true and mathematical time, of itself, and from its own nature, flows equably, without regard to anything external.” But as Einstein proved, time is part of the fabric of the universe. Contrary to what Newton believed, our ordinary clocks don’t measure something that’s independent of the universe. In fact, says Lloyd, clocks don’t really measure time at all.
“I recently went to the National Institute of Standards and Technology in Boulder,” says Lloyd. (NIST is the government lab that houses the atomic clock that standardizes time for the nation.) “I said something like, ‘Your clocks measure time very accurately.’ They told me, ‘Our clocks do not measure time.’ I thought, Wow, that’s very humble of these guys. But they said, ‘No, time is defined to be what our clocks measure.’ Which is true. They define the time standards for the globe: Time is defined by the number of clicks of their clocks.”
I think the guy from NIST may be right in saying that time does not necessarily exist. I'm no expert on physics... come to think of it, I'm not really an expert on anything. But I do think that I can make an understandable argument in favor of a timeless universe regardless, for the sake of debate. So here it goes:
Imagine that all particles of matter contain a set of variables that describe their characteristics as well as positions in space. You can think of these variables as describing the "present". These variables can change, and obviously often do; for example, your position in the universe has certainly changed many times.
Of course, it does nobody any good to speak in present terms all the time. Thus, we assign a value of time to different variables, so that we may establish a mental order of events and properly communicate with others to achieve an ideal set of variables. Ideally, your boss wants your location variable to be "at work" when the location variable of the sun has a certain value, and he/she wants your location to stay the same until the location of the sun has a different value. But that sounds ridiculous, so we define the concept of time with tools (clocks and calendars, days and years) so he/she can say, "I want you to be at work on Monday from 9:00 AM to 5:00 PM". This concept of time is so useful that we have a hard time not
using it. I can't even write this post without it, because it is a necessary part of language (past/future tense, etc.). Time as a concept instead of reality also explains the fact that it always appears to travel forward in a straight line: because the mind orders events in this manner.
Doc: "Bullshit! I already figured it out."
But, if you can, try to think of reality as being "as is," instead of something that is constantly being pushed through some invisible field of "time". You are sitting down and reading this post, and there is nothing else to it. There is no such thing as a "snapshot" of time that can be revisited with some kind of time machine. For example, say that you have an ice cube and a warm drink. You drop the cube into the drink, which cools it. The position of the ice cube has changed, and the temperature of the drink has changed: this is all that has happened in the objective reality outside of your brain. Inside your brain, however, you perceive these changes, apply the idea of time, and order them, so you can do whatever you want with the knowledge you have gained by comparing these differences (like verify that cold objects placed in a warm drink will cool it, a fact that you can use later on or relate to others).
Thus I arrive at this definition of time: An abstract concept used by the mind to order, relate, and analyze differing variables of matter. Pretty slick, right?
There are a few problems with this definition, though. The theory of relativity relies pretty heavily on the concept of time... i.e., time as we measure it seems to change depending on velocity (the whole "astronaut ages slower than his relative on earth" thing). I sometimes read on the internets about "space time" and the warping thereof. Does this mean that time is a real, fundamental part of the universe? Perhaps. It could mean that an object's velocity is related to how quickly its variables can change, which may explain certain parts of the theory of relativity (faster velocity equals slower rate of change?); but again, I am no expert and don't really know what I'm talking about.
Father Time: "I'm in ur universe, pervading ur existencez."
Agree, disagree? Do you think I'm an idiot? While you spend time thinking about whether or not time is real, check out this video from the 70's
of the band Guess Who playing the song "No Time".
Edit: added line about time always traveling forward.
Edit 2: added more examples of time 'measurement' tools
Edit 3: added Back to the Future pic