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Programme '2': clues to our Planet's spin

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Stephen Marsh Stephen Marsh | 17:00 UK time, Monday, 26 September 2011

Distance travelled ~ 691'332'800 km

On our journey around the Sun for 23 Degrees we are focussing on three main themes that control our climate and weather, Tilt, Orbit and Spin. And at the moment we are filming the show about Spin.

The team are on the road in Ecuador. They have gone to the Ecuador rainforest to learn how solar energy powers a power circulation system in the atmosphere that dictates the climate in bands around the world. Kate is also going to drive along the equator at around 1060 miles an hour. Well not quite - her car's going 60 but the planet at the equator is spinning at 1000mph, so for a few moments she's probably the fastest person on the planet.

The next stop after the heat of South America is the Bay of Fundy in Canada. Fundy has the highest tidal range in the world and Kate and the team are going to witness it first hand.

From there it's down to Bermuda to go snorkelling to learn about our planets spin , nice work if you can get it.

One of the things I find fascinating about our planet is that it carries a record of its own history written in its rocks. Some of this history is obvious - you can't miss the impact of giant craters blasted out by asteroid strikes. But some are less obvious - unless you know where to look. Kate's studying corals as these tiny creatures hold the secret to our distant past - and how fast our planet once spun.

Every day corals lays down growth rings of limestone and these daily growth rings build up to create an annual growth ring [a bit like a tree ring]. If you count the daily rings you get 365 days a year, which is what you'd expect.

deep see coral ring

Image credit Owen Sherwood

But if you look at 400 million year old corals you get a very different picture. They have rings just like the modern coral but they are a little bit narrower. But what's really surprising is that if you count the daily growth rings you don't find 365 you find 410. That means that when this coral was alive 400 million years ago the world was a very different place.

But however you measure it - in hours or days the Earths' orbit around the Sun always takes the same amount of time. A year is always constant. The only explanation for the ancient corals having 410 daily growth rings is that millions of years ago the days were shorter. So when this coral was in the oceans there were less hours in each day - in fact a day lasted just 21 hours. And for that to happen the Earth must have been spinning faster.

If we calculate back even further in time we find that around 4 billion years ago, when the Earth was still young, a day lasted just 6 hours. Which means the planet was spinning 4 times faster than today.

That's pretty wild - and we know that because of corals. Wonderful.


  • Comment number 1.

    I Think the vast majority appear to spin the same way the star does, But just because a Jupiter-like planet forms in the planetary boondocks doesn't mean it stays there

    [Unsuitable/Broken URL removed by Moderator]


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