If you’ve been to the beach, you’ve noticed: sometimes the water is high. Sometimes it’s low. The water moves up and down throughout the day. Why? The answer is in the SKY! 🌙
The Moon Pulls the Ocean
Yes — the Moon, 384,000 km away, actually pulls on Earth’s oceans! Gravity from the Moon reaches all the way to Earth and tugs on whichever side of Earth faces it.
Where the Moon’s pull is strongest (the side of Earth facing the Moon), the water ‘bulges up’ — that’s high tide.
Why Two Tides Per Day?
Here’s the weird part: there are TWO bulges of water — one on the side facing the Moon, and one on the side AWAY from the Moon!
The far-side bulge happens because the water on the side away from the Moon gets ‘left behind’ as the Earth itself is pulled slightly toward the Moon.
So as Earth spins, every spot passes through 2 bulges (high tides) and 2 low spots (low tides) per day. That’s why high tide happens every ~12 hours.
The Sun Helps Too
The Sun also pulls on Earth’s oceans — but it’s much farther away than the Moon. The Sun’s effect is about half as strong as the Moon’s.
When the Sun and Moon line up (full Moon or new Moon), their pulls combine, making extra-high and extra-low tides called spring tides.
When the Sun and Moon are at right angles, they cancel each other a bit, making smaller tides called neap tides.
How Big Are Tides?
🌊 In open ocean: about 1 meter
🌊 Near most coasts: 1–3 meters
🌊 In the Bay of Fundy (Canada): 16 meters! World record!
🌊 Mediterranean Sea: only 30 cm (tides are smaller in enclosed seas)
Without the Moon
If the Moon disappeared, tides would shrink to a third of their current size. The oceans would barely move. Many sea creatures depend on tides to feed and reproduce — life would change dramatically!
Tides: the moon’s gentle daily hug on our planet. 🌊🌙
