Tomorrow, on May 9, 2016, there’s going to be an amazing event in our giant sky. Mercury will pass through outer space exactly between us and the Sun, and will look like a small black dot sliding across it. A “transit” like this is super rare. For one thing, the only planets that can pass between us and the Sun are Mercury and Venus, since they’re the only planets closer to the Sun than we are. Even though we and they fly around the Sun in circles, we orbit at different speeds, and those orbits are not tilted at the same angle. So Mercury crosses our view of the Sun only about 13 times in a century (100 years), and Venus only about twice a century! (NOTE: you can see the transit only with a telescope and a filter…do not ever look right at the sun!!) Luckily, Mercury is tiny enough that it will block only a teeny bit of the Sun, and we can still have a sunny day.
Wee ones: The last transit was way back in in 2006. Were you alive for that one?
Little kids: The last Mercury transit was 2006, and the next one will be in 2019. Which of those is closer in time to this year’s? Bonus: Mercury will start crossing the Sun at 7:30 a.m. and finish around 2:30 pm. How many hours does that give you to see the black dot?
Big kids: If the Earth is 93 million miles away from the Sun, and Mercury is 36 million miles away from it, how far is Mercury from Earth when they line up tomorrow? Bonus: What’s the farthest apart Earth and Mercury can be in space?
The sky’s the limit — for real: If we count tomorrow’s transit as your 1st and the 2019 one as your 2nd, then Mercury had a transit every 8 years after that, how old would you be for the 6th transit?
Wee ones: Different for everyone…if you’re 10 years old or older on May 9, 2016, then you were around for the last one!
Little kids: To 2019, since that’s just 3 years from now; the other was 10 years ago. Bonus: 7 hours.
Big kids: 57 million miles. Bonus: 129 million miles, when they’re on opposite sides of the Sun.
The sky’s the limit: Different for everyone: take your age tomorrow (May 9, 2016) and add 35 years. You’ll be 3 years older in 2019, and another 32 years older than that after 4 more 8-year chunks.