I wonder ... Which way is down?
A group of students stood on the classroom carpet, holding fist-sized rocks. On the count of three, they all dropped them. The rocks fell in the direction everyone expected: down. “Let’s say you were standing on the opposite side of the earth and dropped a rock,” said teacher Paul Crivelli. “Would your rock fall in the same direction?”
The simple question stumped the fifth graders. The answer seemed easy but when they turned and talked to their partner, not everyone agreed.
They embarked on an investigation as part of their Space Systems: Stars and the Solar Systems science unit.
In their science workbooks, they turned to a drawing of the earth with a child standing on each of the continents. Students drew arrows indicating which way a rock would fall if each child dropped one. Some lines went in the same direction, others pointed into the center of the earth.
They also watched videos of students all over the world dropping rocks. In Canada, Ecuador, Chile, New Zealand, Thailand, Singapore and Turkey, the rocks fell down. But—down was in all different directions!
Crivelli posed another question. “If you dug a tunnel straight through the earth and threw down a rock, would it pop out of the other end?”
“A question that big can’t be tested,” he said. “Think it through. What’s your prediction based on what we’ve been studying?” He reminded them of their vocabulary word gravity.
“The rock is going to be stuck in a loop going up and down,” said Danika.
Ranya said, “It’s going to fall down towards the middle of the earth and just stop.”
“I love the thinking,” said Crivelli. “Let’s get back to our first question, then. Which way is down?"
Through the discussion, students concluded that gravity makes objects fall toward the center of Earth, no matter where you are on the globe. “There are multiple downs,” they agreed.