29Aug2018

Stop The World And Let Me Off!

giddy

Have you ever wondered, why we don’t feel earth’s rotation? I mean, we’re all on this rock spinning, right? So why aren’t we all feeling giddy!

It’s a good question and has a surprisingly simple answer. Yes, it’s no surprise to anyone that our planet, with its atmosphere and everything on it, is continuously spinning. Earth spins on its axis once in every 24 hour day. The speed of Earth’s rotation at the equator is 1,600 kilometres per hour. Stay with me! This means that at this very moment, you’re travelling at something like 465 metres per second, or a little less if you’re situated near to one of the poles.

So the question here is, why can’t we all feel it? Well there is simple physics behind all this. The precise answer lies in the nature of Earth’s movement.

The constant spin of the Earth confused our ancestors. They noticed that the stars, the sun and the moon, all appeared to move above the Earth in an arc. Because they couldn’t feel Earth move, they logically figured this to mean that Earth was stationary and the heavens moved above us.

Think of being on an aeroplane when it’s smoothly travelling at a constant speed and constant altitude. You’ve unbuckled your seatbelt to go on a walk down the aisle, but you can’t feel the movement of the plane. The reason is simple, you, and everything around you are travelling at the same speed. The only way you know you’re moving is if you glance at the clouds outside.

Now, if Earth were to change suddenly change direction, we’d certainly feel that, and it wouldn’t be pleasant, like a sudden slam on the brakes at a planetary scale. Whoa!! See, I told you it was easy to understand.

OK, so why does Earth spin so constantly, like it has for billions of years? Hmm, that’s another good question and again, has a simple answer. Because there’s nothing stopping it!

Our Solar System formed from a hot spinning Sun that stretched out into a flattened disc to form all the planets.  Those newly formed planets inherited that rotation.  So all our planets, moons, and everything else scattered in our system is still spinning after billions of years because of ‘inertia.’

https://s3.amazonaws.com/s3.timetoast.com/public/uploads/photos/4190185/Fig1_18.jpg?1474699931

The formation of the Sun and planets

Now, as I mentioned earlier, the spin of our planet is happening at an almost constant rate, but nothing lasts forever. Earth is slowing down ever so slightly thanks to the Moon being a bit of a gravitational drag. It pulls on the tidal bulge of our planet, which causes tidal friction. Our clocks hate that.

As a result, sometimes we need to add an extra second to our clocks, because Earth’s rotation is slowing down by about two thousandths of a second every day. However, because this change in speed is so tiny, for our purposes, it still feels like Earth is rotating at a constant rate. In other words, it feels like nothing at all.

OK, Bottom line – why don’t we feel Earth rotating, or spinning, on its axis? It’s because Earth spins steadily, and moves at a constant rate in orbit around the sun carrying you as a passenger right along with it. Told ya it was simple.

Our days are warming up again as we pass the Spring Equinox on Friday 23rd. As I mentioned last week this day marks the beginning of autumn in the northern hemisphere and of spring in the southern hemisphere. It’s often said that day and night are equal on the equinox.

Looking skyward, Mercury is very low to the western horizon as Venus continues to shine brilliantly in the western sky throughout the month. By the end of the month, Venus, Saturn and Mars are found in a line stretching across the western sky. Last chance, take a look!  Written by: Dave Reneke

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