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You might think the Moon is just a pretty light in the sky, and that life on Earth would continue pretty much the same way if it disappeared, but would it?

The Moon’s effect on the ocean tides

The ocean tides are strongly affected by the Moon’s gravity. On the side of the Earth facing the Moon, the ocean water is pulled towards the Moon, causing it to bulge outwards and drawing the water away from the shores. We call this ‘low tide’. As it rotates away from the Moon, the gravitational pull lessens, and the water relaxes back, causing water to rush back towards the shore. We call this ‘high tide’!

However, there are two high tides and low tides a day… so where does the second one come from?

Click to reveal the answer

Well… the Earth also gets pulled towards the Moon by its gravity. In doing so, it leaves the oceans on the far side behind a little! That causes the same bulge on the far side from the Moon, and another ‘low tide’/’high tide’ cycle, just like on the side closest the Moon.

diagram showing two high tides on opposite sides of the Earth

Without the Moon, the tides would therefore become much weaker. They wouldn’t disappear entirely however, since the Sun also has a similar albeit much weaker effect.

So how would a lack of tides affect life on Earth?

Without tides, we would not be able to harness tidal energy to generate electricity, and many animals which rely on tides and the resulting tidal currents would likely struggle to survive. For instance, many birds and fish feed by waiting for the tides to wash smaller sea creatures they feed on out to sea. This concentrates them into a much smaller area, resulting in a bigger catch. Fishermen use knowledge of this to increase their catches too!

The Moon’s stabilising effect on the Earth’s tilt

Our planet is tilted at 23.5 degrees compared to its orbit around the Sun. This causes the seasons by changing which parts of the Earth are pointed towards the Sun over the course of the year (the Earth’s orbit around the Sun). In December, the northern hemisphere is pointed away, whilst the southern hemisphere is pointed towards the Sun. As a result, December is winter in the northern hemisphere, and summer in the southern hemisphere! In June, the opposite is true.

The Moon prevents external gravitational forces from affecting the Earth’s tilt, such as the other planets in our Solar System as they pass by. Without them, it’s predicted that the Earth’s tilt could vary by up to 85 degrees! That means the planet would effectively be on its side, with the Sun rotating around the poles! Imagine how dramatic the shift in climate would be with the North and South pole becoming the hottest places on the planet, and the equator becoming the coolest…

diagram showing Earth tilted on its side facing the Sun

So, how would this shift in the planet’s tilt affect life on Earth?

Whilst human communities might be able survive such a shift by relocating to different areas of the globe, the vast majority of animals would find themselves unable to adapt to their rapidly changing environments and many would likely face extinction. Natural disasters would also abound as the polar ice melted and changing weather patterns brought hurricanes, floods, and earthquakes to areas unprepared for them!

  • How do you think humans would respond to rapidly changing climates on Earth?
  • What would be the difficulties involved in mass relocations of human populations?