215: The Big Card
Dear Hank & John
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What's Under the Ground?
Children know all these things without any look at the remarkably cool ways that we figured this out, and it's not that complicated. If you want to know what's under the ground, you can send a sound wave down,. You can see like dinosor bones beneath thes. The good news is the earth makes those sounds itself the time, and they're called earthquakeso. And so when we listen to earthquakes as they travel around the planet, we can pay attention to how fast they move through different areas of the planet. This next questionis from alice, who writes, dear john and hank, i was recently at a talk at a book festival, and she said that
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