“Ten Things Everyone Should Know About Time”
September 27, 2011 1 Comment
Cosmic Variance has an interesting and brief article about the nature of time – ten realities about time that we may not realize. They’re already brief points so I won’t try to summarize them all (go read it!), but here are some parts I like:
2. The past and future are equally real. … Intuitively we think that the “now” is real, while the past is fixed and in the books, and the future hasn’t yet occurred. But physics teaches us something remarkable: every event in the past and future is implicit in the current moment… As Einstein put it, “It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.”
4. You live in the past. About 80 milliseconds in the past, to be precise. Use one hand to touch your nose, and the other to touch one of your feet, at exactly the same time. You will experience them as simultaneous acts. But that’s mysterious — clearly it takes more time for the signal to travel up your nerves from your feet to your brain than from your nose. The reconciliation is simple: our conscious experience takes time to assemble, and your brain waits for all the relevant input before it experiences the “now.” Experiments have shown that the lag between things happening and us experiencing them is about 80 milliseconds.
10. A lifespan is a billion heartbeats. … Remarkably, there exist simple scaling laws relating animal metabolism to body mass. Larger animals live longer; but they also metabolize slower, as manifested in slower heart rates. These effects cancel out, so that animals from shrews to blue whales have lifespans with just about equal number of heartbeats — about one and a half billion, if you simply must be precise. In that very real sense, all animal species experience “the same amount of time.”
Obviously these are imperfect points by virtue of being extremely simplified, but they’re pretty interesting nonetheless. I find the “you live in the past point” particularly interesting. Reality is changing faster than we can perceive it; everything you think you see is wrong (in that your perception does not match your body’s current state, albeit only by 80 milliseconds). Keanu “whoa”.