Why does the tide go in and out?

1. 1

   Wobble says

   At the beach, the sea slowly creeps up the sand. Hours later, it slowly slides back down again. That's the tide going in and out. Far away in the sky, the Moon is gently pulling on the sea, and that pull does most of the moving.

   For ages 4–7
   Hear Wobble

   Checked against What causes tides? (NOAA Ocean Service)

2. 2

   How does the Moon move the sea?

   The Moon's pull helps heap the sea into two big bulges of water. Meanwhile, the Earth keeps spinning, so your beach turns into a bulge, then out again. Inside a bulge, the tide is high. In between, it's low. That's why most beaches get two high tides and two low tides each day.

   For ages 6–9
   Hear Wobble

   Checked against The lunar day (NOAA Ocean Service)

3. 3

   Why is high tide a bit later each day?

   While the Earth spins, the Moon is travelling around the Earth in the same direction. So after one whole spin, your beach has to turn a little further to catch up with the Moon. That takes about fifty extra minutes. So each day, the tides come about fifty minutes later.

   For ages 8–11
   Hear Wobble

   Checked against The lunar day (NOAA Ocean Service)

In Lil' Phil, reaching the bottom of this wonder earns a sticker for Wobble's collection.

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