Part Two – A Lucky Escape For The Newly Born Earth

A lot of gas and dust had been gathering in a certain corner of the Milky Way. It was 4,630 million years ago, that’s 4.63 billion, if you can get your head around big numbers and for some time, the gas cloud had been getting denser, thicker, heavier, blocking out the light from nearby stars. As atom piled upon atom, each attracted by the mass of other atoms at the centre of the cloud, space was warming up as the heat generated by the pressure built up. Close by the cloud, it was too hot to be exposed and the gravity was so strong, any particle, atom, rock or passing comet, was pulled in towards a terminal meeting with the cloud, a guaranteed end to existence.

One day, maybe it was a Monday, the last atom required to set off this time bomb rocketed into the cloud and the crushing gravitational mass began fusing the hydrogen and helium atoms under the incredible pressure, releasing a steady stream of energy radiating out in all directions and a brilliant white light of hot plasma lit up the area for billions of miles.

We call it The Sun. The full story of how it came to be, can be found in …..
‘Day 21: The Birth of The Sun’.

(The ‘Diary of the Universe’ covers about 300 ‘Days’ each with its own story)

As ancient as our 4,630,000,000 year old sun is, on the day it was born, two thirds of all the time that has ever existed in our Universe, had already passed by.

The gravitational forces were so powerful, every scrap of material for millions of miles was pulled into the nuclear furnace that was fusing the gas atoms at millions of degrees. Way out in the blackness, where the gravity was weakest, a few rocks were orbiting the star like weights on the end of a string, travelling too fast to fall into the fire but too close to escape, doomed to spend forever or even longer trapped on the longest voyage possible.

In total, they made up less than one percent, less than one fifth of one percent, a minuscule 0.14% of the material within influence of the star. Our planet is just a small part of that 0.14%. We are a million times smaller than The Sun.

A trifling 130 million years later, our bit of rock was still a bit warm from all the ‘aggregation’ a fancy way of saying lots of rocks were piling in on top of each other melting the early adopters until we had a core of molten magma containing a handy few million tonnes of gold and other heavy bits.

On the surface, the rock was still moving there too, oozing around at about 1200 degrees Celsius. Above the bubbling cauldron, the atmosphere was a heady mixture of nitrogen, carbon dioxide and a touch of water vapor. Sorry, no oxygen.

While the earth was waiting for things to cool down a bit, it could not avoid the annoying interruption of large bits of rock that were the left over crumbs from the Sun’s table. Annoying as being pelted with rocks can be, it was nothing compared to the visitor that was set to arrive a little while later.

Just 155 million years after our little planet got a start in life, just a baby, a rather hot babe, a little sister arrived. Yes indeed, we used to have one more planet in our neighbourhood and her name was Theia. She was by all accounts, a cute little thing, about the size of Venus and she popped in travelling at about 5 times the speed of a bullet.

The meeting was not a gentle affair, no gentle sisterly kiss, rather more like a headbutt of gargantuan proportions, an upper cut from the south west that nearly missed us, but it didn’t. Where a future northern hemisphere would be, siblings came together with a crash of unbelievable violence, which gets its own article on
The planet Theia colliding with earth. Everything important that ever happened. History of the Universe.
‘Day 25 – The Day The Earth Crashed’.

For the next 100 years, a microsecond of Universal time, rocks that got themselves blasted off into space, rained down, upon the earth, creating some mighty splashes in the molten goo. The interesting bit was that only about half came back. “What happened to the rest”?, one may ask. Look up my son, on most nights you will see the other bit. Yes, it’s the moon albeit a lot further away than on that sunny morn.

Close moon. Everything important that ever happened. History of the Universe.By the time ‘Day 27’ comes around, 4.38 billion years ago, it was an anniversary of sorts, mainly for the Sun, because it had just completed its very first birthday, aka, one trip around the galaxy. If all goes well, it should be able to make about 40 circuits before the light goes out. (So far, The Sun has make 20 circuits, putting it in middle age so I guess the earth is middle aged now too, as we have been faithfully tagging along since the beginning.)

It took a good half a billion years for the temperature to drop far enough for the surface rock to solidify, forming a thin, hard crust on a liquid core. The earth was tilted off the vertical by 24 degrees by the massive impact with Theia which will turn out to be a very good thing, giving us the seasons that will stimulate and sustain life, when it finally arrives.

By the time The Sun has its second birthday, the Moon has moved away from its initial position, a very close 22,000 kilometres, to 68,000 kilometres away.

The accumulation of rock over the past half billion years, including the donation by Theia, has added considerably to the mass of the earth which encourages even more debris, pulled in from the outer reaches by earth’s strong gravity of the mass of the rock and iron core composition.bombardment

By the third lap around the galaxy, water degassed from the mantle together with vast volumes delivered by billions of meteors, primarily composed of ice, covers the whole solid surface of the planet. By ‘Day 32’ the earth has slowed down a bit, from the giddy 6 hour day just after the collision, to a slightly more sedate seven and a half hours.

Over the next 200 million years volcanic activity really got underway, pushing up many islands across the whole planet. The moon is 87,000 kilometres away now, (50k miles) and still causing massive 1,000 foot high tines. By ‘Day 35’ the sun completes its fourth orbit around the centre of our galaxy, and as the earth’s spin slows to a 9 hour day, molecules of chemical elements form the first single cell.

This article covers just about 20 ‘Days’ in the Diary of the Universe, the full list of 300 events can be found here.
There are about 300 ‘Days’ of Earth History, listed in our ‘Diary of The Universe’ poster and it’s interesting to follow the development of our little patch. You can download the whole poster for printing.

All about The Moon. No, really.

(You can see ALL the interesting ‘days’ in the magnificent science poster which you can download and print. See what it looks like here.)

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Day 25 – The Day The Earth Crashed

Imagine if our world had a diary and on the interesting days, someone pulled out a big book and wrote about it.

the bookDay 25 was such a day and as important as days go, this one was especially memorable.

It was about 4,475 million years ago and it was a warm day, well, hot actually as the surface was mostly molten rock tipping the scales at around 1000 degrees centigrade. Our freshly minted sun was just a pup, only 150 million years old and had gobbled up most of the material in this particular part on the outer rim of this particular arm of this particular spiral galaxy in this particular cluster of galaxies, well, you get the idea.

The few scraps (0.14%) that were left over included the rocky bits, Mercury, Venus, Earth, Mars, Theia, ….. Theia? Yep, there was a planet called Theia zooming around the new sun, just as we were.

Among the others, all gas and no substance, poor old Jupiter couldn’t find enough hydrogen and helium to really get going as a star and other gassy ones, Saturn, Uranus and Neptune were way out of contention for ‘star’ material.

We not sure about Theia’s orbit but we do know it was rocky and on a collision course with us because one fine morning, it arrived, tootling along at 5 times the speed of a bullet and smacked into the northern hemisphere of earth.

We know that because the collision tipped the earth over 24 degrees to the side, which turned out to be a very good thing for people who enjoy spring. Without that collision, we would have no seasons and I’d miss that.

If you were around on that day, you would have wanted to be standing well back behind the barrier because it made quite a bang with a large chunk of rock being blasted off into space. Unfortunately, lots of bits didn’t quite make it that far and a rain storm of disconsolate rocks began pelting down at an alarming rate. If ever there was a day to remember your hard hat, this was the one.

Over the next little while, most of the rocks that stayed ‘up there’ (a relative term as there is no up or down in space) became very attracted to each other and after mere 100 laps around the sun, a century as we know it, we had a moon.

We also had a fairly brisk day too and if you had been around to see it, you would have been able to watch the sun strolling across the sky because the day was only 3 hours from sun up, to sun down, that is, a 6 hour day.
This is because when Theia paid her visit, she came from our south west, hitting the top half a glancing blow that caused us to spin like a merry-go-round.
In the time that has elapsed since that fateful day, we have slowed down quite a bit to our familiar 24 hour day. Our orbit around the sun has slowed quite a bit since then too but that’s another story.

At this point, the moon was ‘right there’, in front of you, a mere 22,000 kilometres away. This is so close, it covers the sky so you would not be able to see any stars and the tide, well, if we had water, which we didn’t, suffice to say, the tides would have been memorable.Close moon. Everything important that ever happened. History of the Universe.
As it happened, when our water was finally delivered, the moon was still incredibly close, by our standards today and yes, the tides were something to behold, 1,000 foot high and that’s after they died down a bit.

At the beginning the moon was sneaking off at a fair cracking pace but has slowed its escape now to just 38mm a year giving it an average getaway speed of 85mm a year, which is not much I hear you say, but it’s fast enough to have drifted 360,000 kilometres.

What future then for our pet rock? Well, that depends on the Sun which is planning some serious expansion in another half a billion years or so and it will be reaching out once a month trying to catch the moon as it orbits the earth.
By then, the orbit will be much wider and the ‘month’ will be longer too, probably about 42 days, so it’s all a bit of guess work at this stage. Unfortunately, the most likely scenario it will end up much like one of Saturn’s rings only rocks around the earth, not pretty ice crystals around Saturn.

AND, this is just a one line entry in what I believe is the greatest scientific gift poster that anyone could gift to a child. But that’s just my opinion.Dan Hughes. Everything important that ever happened. History of the Universe.

The Big Bang Explained. Sort of

All about The Moon. Really.

(You can see ALL the interesting ‘days’ in the magnificent science poster which you can download and print. See what it looks like here.)