The Center for Communicating Science issued a challenge specifically to working scientists to write an explanation of time suitable for 11 yr olds. http://www.centerforcommunicatingscience.org/the-flame-challenge-2/ The contest is closed, and the winners will be judged by 11 yr olds, and announced in June.
I was fascinated by this challenge because I find the topic of time pretty compelling, and so even though I’m not a scientist, I wanted to give it a try. Since I did this only for myself, I gave myself some parameters. I didn’t want to distill time to a single definition, but rather show kids some of the myriad ways science looks at time. I didn’t want to talk down to these kids, but I’m not a teacher, either, so I had to guess at what would be a suitable level.
Here’s my offering; my 300 words.
Time is the counting method we humans have created to document change. We all understand time and clocks. However, scientists get far more complicated when studying time. We even have a unit of time which is the shortest in which any change can be detected, called Planck Time. It’s so incredibly small that it’s impossible for us to even imagine, but it is very useful when trying to understand the nature of change.
It can get confusing, because we also talk about things ‘outside’ of time, like the ‘spooky’ action of two particles that are ‘entangled’– change a property of one and the other simultaneously changes, no matter how far apart they are. Quantum physicists also talk about something called superposition – which means that a particle is in every possible position at all times until we try and look at it, which then forces it to stop at one position.
Time has no fixed rate of change. Einstein figured out that space and time are two sides of the same fabric – that’s ‘relativity’, because that fabric shrinks and stretches unequally from the density of every object within it.
You and I experience our lives at slightly different rates of time. Those differences are so small that it’s not noticeable to us on this little planet. But think of black holes; some scientists think that there’s a point inside a black hole where time stops- where no change can happen. Others think time never totally stops, but slows as the hole compacts… then perhaps explodes, creating a new universe! We just don’t know.
My goal isn’t to give you a single definition of time, but to show you that time is about change, it’s something completely mind-blowing and understanding time will continue to fascinate us for a long, long … time.
For a couple of very interesting books on time, consider Sean Carroll's "From Here to Eternity" and Lee Smolin's "Time Reborn".