A twitter Kindergardener asked how long it takes for light to travel to us from the sun, so I gave her mom some ideas.
Here is what she can do: so pick something to bang together and she can hear it instantly, now walk maybe a couple hundred feet away (500? 1000?) i think it works with couple hundred and bang.
She should be able to notice it looks and sounds funny cuz the there's a delay between seeing you banging and hearing it. There's the clue that sound actually takes time to travel to her. Now for more fun:
When people discoverd 100s of years ago that Jupiter had moons, they realized they could use them like a clock, cuz they went round and round very regularly like the hands of a clock, (slower!) and so people started making tables of what times the moons would appear when!
Back then... clocks didn't work so well on sea going sailing ships and people hoped they could use Jupiter and a small telescope at sea, as a clock! By consulting the tables. But problems occured...
At some parts of the year the Jupiter moon clock ran behind! About 20 minutes behind! But some observant astronomers (like your daughter...) remembered hearing how funny it was when people bang on things far away and you hear a delay in the banging, cuz sound takes time to travel, so
they realized just like the delay in far away banging things, they SAW a delay in the jupiter clock hands when jupiter was FURTHER away from us, and so they reasoned that light itself took time to travel! About 17 minutes from jupiter to earth. This was an amazing discovery because seeing, light, seemed to be INSTANTANEOUS!
And since Jupiter is REALLY far,
that means light is REALLY fast. From banging far away you could probly, time the delay and figure out sound goes about 1000feet in a second. For the speed of light it took a little while to figure out how fast cuz we needed to know how much further earth was from Jupiter every 6 months:
Distances a LOT MORE than a 1000 feet!
Earth is 200 MILLION miles further from Jupiter when it is on the other side of the sun, so
200million miles causes 20 min delay, so the light is traveling
10million miles a minute
a million miles in 6 seconds
sixth of a million in second, about 150,000 miles a second!
Dunno how much of that you can translate for your daughter, but I hope you can try the experiment with her. Maybe with 2 people you help her watch and time it and other person bangs! I've never tried it. I'll try it with a neighbor and try to measure it and get 1000feet per second!
If your daughter ever gets a chance to look at jupiter in a small telescope (binoculars?) maybe with a local astronomy club or something... someone can point out Jupiter and some moons?
I remember the day I was watching someone banging with a hammer and noticing the funny delay and a lightbulb went off in my head and I understood this jupiter clock story!
Finally! This story gives us the answer to her question! Because by looking at the delay in the Jupiter clock, they figured out it took light 17 minutes to go across the orbit of the earth, from one side to the sun and across, so HALF of that is how long light takes to go from the sun to the Earth, about 8 and a half minutes!
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