Monday, July 6, 2015

About Time

Augustine wrote in his Confessions that as long as no one asked him, he knew perfectly well what time is, but as soon as someone asked him to explain it, he hadn't the faintest idea. I sympathize. Time is a very puzzling thing. Not only is its exact nature an enigma so is the question of the difference between time itself and our measures of time. It's hard to think of time apart from some measurement of it yet it makes sense to ask what it is that we're measuring when we measure time.

In any case, Buzzfeed lists 17 interesting facts about time that perhaps you didn't know. Here are a few of them:
  1. A second isn’t what you think it is. Scientifically, it’s not defined as 1/60th of a minute, but as “ the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom”.
  2. When the dinosaurs were alive, there were 370 days in a year. The Earth’s spin is getting slower because the moon’s gravity is acting as a drag, so days are getting longer, by about 1.7 milliseconds per century.
  3. The smallest standard scientific measure of time is the “ Planck time”. It takes you about five hundred and fifty thousand trillion trillion trillion Planck times to blink once, quickly.
  4. There’s no such thing as “now” as far as physics is concerned. Space and time are fluid, affected by gravity and your speed. Einstein put it like this: “For us physicists, the distinction between past, present and future is only an illusion, however persistent.”
  5. Because light takes time to reach us, everything we see is in the past. The sun you can see out of the window is 8 minutes and 20 seconds old. The light from our nearest star, Proxima Centauri, is 4 years old.
  6. New experiences really do seem to be longer in the memory than familiar ones. It’s called the “ oddball effect”, and it seems to be why time feels like it’s going faster as you get older – because more stuff is familiar to you.
  7. Time passes slower the faster you move. If you flew to the star Sirius at 99% of the speed of light, then flew back again, the people you left behind on Earth would have aged more than 17 years. But you would have aged less than two and a half years.
Philosophers have two different views about what time is like. One theory is called the dynamic view of time. This says that the only existing time is the present moment. The past is gone and the future is not yet. This is the common sense view.

The other theory, the static time theory, holds, like point #4 above says, that all moments of time - past, present, and future - exist simultaneously and that the temporal flow of time is an illusion of our consciousness. Imagine the frames of a movie on a reel of film or the same movie stamped onto a DVD. Every event exists simultaneously with every other event, but our minds experience those events serially.

One of the great questions in cosmology today is whether time had a beginning. On the dynamic theory it seems that it would have, on the static theory perhaps not.

Whatever the case, it is true that, as many scientists and philosophers have noted, the nature of time is one of the universe's greatest mysteries.