How is the Moon the perfect distance to cause total eclipses?

How is the Moon the perfect distance to cause total eclipses?

“I understand that total eclipses are incredible events where the Moon blocks out the Sun, creating a momentary darkness during the day. It's like a celestial magic trick! But what I'd love to know is why the Moon's size and distance from Earth make this amazing phenomenon possible.

Could you please explain this in a way that someone who's not an astrophysicist like me can understand? I'm curious about the science behind it and what makes our Moon just the right fit for these spectacular total eclipses.

Thank you so much for taking the time to answer my question. I eagerly await your response.” - Tonya


Thanks for the question Tamara!

The occurrence of total solar eclipses, where the Moon perfectly covers the Sun, is a remarkable cosmic coincidence that arises from several factors, including the relative sizes and distances of the Earth, the Moon, and the Sun.



Here's how it works:

Relative Sizes: The Sun is much larger than the Moon, approximately 400 times wider, but it's also approximately 400 times farther away from Earth. This means that from our perspective on Earth, both the Sun and the Moon appear to be almost the same size in the sky. The Sun's larger size is counteracted by its greater distance.

The Moon's Orbit: The Moon follows an elliptical orbit around the Earth, which means its distance from Earth is not constant. However, on average, the Moon is about 384,400 kilometres away.

The Earth's Orbit: Earth orbits the Sun in an elliptical orbit as well. This means the distance between Earth and the Sun varies over the course of a year, but the average distance is about 149.6 million kilometres.


The crucial aspect that leads to total eclipses is that the Moon's orbit is tilted with respect to Earth's orbit around the Sun. This tilt creates what's known as the "ecliptic plane," the plane in which solar eclipses occur. Solar eclipses can only happen when the Moon crosses the ecliptic plane at the same time as it's directly between the Earth and the Sun. When this happens, you have a total solar eclipse.


Total eclipses are relatively rare because this alignment has to be almost perfect for it to occur. If the Moon is a bit too far from Earth, it won't fully cover the Sun, resulting in an annular eclipse. If the Moon is a bit too close, it will completely cover the Sun but still leave a ring of sunlight around its edges, which is known as a total solar eclipse.


In essence, the Moon is at the perfect distance to create a total solar eclipse because it fits just right in the sky to block the Sun completely, but this alignment is a product of the relative sizes and positions of the Earth, the Moon, and the Sun. It's a stunning cosmic dance that has fascinated humans for centuries.



The section where we explain the above to 5-year-olds (and Flat Earthers).


 Imagine the Sun, the Moon, and the Earth like a big cosmic game of hide and seek.

The Sun is like a giant lamp in the sky, and it's really, really bright.

The Moon is like a nightlight, not as bright as the Sun, and it lights up our night sky.

The Earth is where we live, and it's like our home.


Now, sometimes, the Moon moves between the Earth and the Sun. It's a bit like when you stand in front of a lamp, and your shadow appears on the wall. The Moon's shadow is much bigger, though.

And guess what? When the Moon is just the right distance from the Earth, and it lines up perfectly between the Earth and the Sun, it can make the Sun disappear for a little while. That's what we call a "total eclipse." It's when the Sun goes away, and it gets all dark for a little bit.

But don't worry! Total eclipses are rare, so the Sun comes back, and it's all bright again. It's like playing peek-a-boo with the Sun and the Moon in the sky!



You’ve come this far…
Why not venture a little further into A.S.S. - our exclusive Australian Space Society. 

And keep thrusting Australia into the deep unknown…


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