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.

Day 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.
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.

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.)

103 The Day Siberia Burned

Imagine if our world had a diary and on the interesting days, someone pulled out a big book and wrote about it. Day 103 was such a day.

It was about 300 million years ago, just a regular 22.5 hour day and on that lovely sunny morning, on the plains of a future Siberia, a Thursday perhaps, the recent rumblings and shaking of the ground took a turn for the worse.

The newly evolved reptiles had developed into millions of species and the air was filled with insects, some absolute monsters.
The oxygen in the atmosphere had been building up now for quite a while, a far higher concentration than the modest levels that would eventually be the norm for the apes of the future who will enjoy a 24 hour day at 21%, no the oxygen level on this lovely sunny morning was about 35%-40%. A lot of oxygen is a good thing, right?

Well, yes, in the same way your plane’s full tank of fuel is a good thing, right up to when it catches fire, then maybe not so good.
Well, all this oxygen made it possible for creatures that get their oxygen through this skin, insects for example, to grow and grow they did. Courtesy Nat GeographicOn this fine sunny morning, there were dragonflies with wingspans like eagles filling the air and let’s not think too much about the local equivalent of mosquitoes.

But aside from the rumblings, life was getting on with what life does and there was no thought for the huge twin asteroids that were already on their way to crash into a future Canada. No matter, that was still a few millions years to go, so certainly no bother for the reptiles and insects.

The first sign of trouble was the smoke and gas arising from a patch of rather large trees. At that moment, the first of many mini volvanos broke the surface over thousands of kilometres of forest. There was going to be trouble and it was not just the trees that were burning and causing all that smoke that blocked out the sun, it was the coal. Vast clouds of thick black choking smoke rose into the upper atmosphere, blocking out the sunlight and quickly spreading around the world.

Yes, the coal, just under the ground, stretching to the horizon in all directions and hundreds of feet thick, was on fire. All that oxygen was not helping either, but why was there so much coal, nearly two million square kilometres of it, as it happens?

wall of coal
An 80-foot wall of coal at a Peabody Energy mine in Powder River Basin in Wyoming. The company filed for Bankruptcy in early April 2016.

The answer to that is, ‘termites’. Well not exactly, more the lack of termites. What had happened it seems, was that as plant life evolved on land, feeding on sunlight as it does, those that could grow taller got the most sunlight and lived to pass on this trait.
The only way to compete was to grow taller and so lignum had been invented, well, evolved actually a couple of hundred million years before this fine sunny morning. It’s a woody substance that stiffened up the stems of plants and in those days, allowed them to eventually to become trees.

Now here was a problem. You see, lignum is very, uhm, woody and hard to break down, to digest. As it hadn’t been around before, there was no creature large or small, that had evolved the dental hardware to handle it. No bacteria could touch it and termites were millions of years away, so the trees grew and grew, got old and died. That’s all the happened, they just lay there, intact. More trees fell on top and more on top of them, until vast swathes of the earth was covered with dead trees that got compressed and turned in the massive coal deposits of the world as we know it.

As the volcanic action spread across the land, lava flowed and coal burned, for centuries. For a few thousand years, the earth was dark and very cold. There was no sunlight to sustain the plants and most creatures on land and most in the oceans too, turned up their toes in one of the great extinction events we now call the Permian extinction.
Eventually, the lava flows stopped in many places and the fire burned out and the sun came back, just long enough to make use of all the recently released carbon dioxide to heat up the earth, in a hot house of global warming as never seen before. What life had managed to survive the dark and cold was now faced with soaring temperatures and bright sunlight. Actually, it was just a trick and the lava began to flow once more and the whole earth was turned back into a cold dark night that lasted for a few more centuries before doing it again, perhaps as many as seven horrible cycles over several thousand years of hot and cold, dark and light.

Yep, day 103 was a big one and it was all because of those dam termites.

(You can see ALL the interesting days in The Magnificent Science Poster which you can download for tuppence.)

Day 8 How We Figured The Age Of The Universe

Imagine if our world had a diary and on the interesting days, someone pulled out a big book and wrote about it. Day 8 was such a day.

It’s 10,500 000,000 million years ago and time to reflect on progress.

In our puny life times, we think of a couple of thousand years as a long time and that is not so surprising given the short span of our lives, a mere 7 or 8 dozen passes around the sun if you’re lucky and that’s it, you’re done.
Look at our history, a mere 500 generations back our grandfathers were just learning the art of growing food. Ten thousand generations back and we had only just become a clearly defined species in our own right, so how could we appreciate the passage of say, a million years?
If we struggle with a million, then what of this day in our diary when the Sun and the Earth were still six thousand million years in the future? Let’s just think about that again, not one million or a hundred million, but six thousand million years in the future. That’s when our Sun and Earth will come into existence. Continue reading Day 8 How We Figured The Age Of The Universe

Day 7 The First Stars In The Milky Way

‘Day 7’ The first stars in the Milky Way are now a thousand million years old.

Aside from the twinkling variety, how many types of stars are there? Seems like a fair question and the answer is a very scientific one too, ‘lots’.
Actually, most of the stars are not alone with twins being the most common setup in most galaxies and a fair helping of triplets too. This is not surprising when you know how the stars get going in the first place.

It is fairly widely known that stars form from clouds of gas but we tend to think of this as a ‘one cloud – one star’ event. In reality, the clouds that start the process are so vast, as they collapse under the force of gravity, the core is usually about 100 times more massive than our Sun. This core then usually fragments into smaller clumps, each one with the potential to become a star. (No, not like an audition).
These protostars will start out 10 to 50 times bigger than the sun depending on how many form out of the cloud core and his happens fairly quickly, perhaps 10 million years or so. (If you’re a universe this is positively scooting along.)
As gas is pulled into the core of each one, the temperature rises to a few thousand degrees and infra-red radiation is released, which is how astronomers can ‘see’ them (no light at this stage). Eventually pressure in the core puts up the ‘no vacancy’ sign and the balance between pressure outwards and gravity inwards reaches an agreement. The core is only about 1% of what the star will become once it moves through the proto stage.
Gravity is still doing its thing and pulling in more gas but the core is full, so it builds up putting more pressure on the core. When the core becomes hot enough to begin nuclear fusion, the stellar wind created pushes back against any new material being gathered by gravity and it is now considered an operational protostar.
The next step for our baby star (and probably its brothers and sisters ‘nearby’) is to start organizing its stellar wind along the rotational axis that is mainly flowing out at the poles. Material excreted forms huge discs and material then tends to fall back to the ‘surface’ and begin to glow. A part of this material is ejected far enough to begin clumping into balls, aka planets either the heavy rocky kind closer to the star or the gas type further out.
This early period is called the T-Tauri phase, a ‘type’ of star and later as it heats up it becomes another ‘type’ of star, a main sequence star. Our Sun is in the main sequence stage. In fact most of a star’s life is spent in the 10,000,000,000-year long main sequence phase. The length of time spent in the T-Tauri (young bull?) phase depends to some extent on the initial size. Very massive stars don’t waste much time in the first stage and move into main sequence very rapidly.
If a really massive star forms in the cloud it can become a supernova when it dies instead of gracefully aging into the white dwarf stage. When the explosion occurs at the end, the pressure on the cloud can create many new protostars, so sometimes there are groups of young stars all in the same neighbourhood. This is the major contributor to the pinwheel effect in spiral galaxies.
At the other end of the scale we have clumps that are not big enough and just don’t make it. To become a protostar the gravity-induced hot spot has to be a minimum of about 75 times more massive than our solar system’s gas giant planet Jupiter.
A clump that is almost big enough will be, say 70 times more massive than Jupiter but its physical size will be similar, meaning a lot of gas has been compressed down to Jupiter size but still not enough to cause nuclear fusion. If you want to be a star you need to be at least 8% of the size of the Sun, the minimum requirements. If not, this is another ‘type’ of star called a brown dwarf, halfway between a gas giant planet and a star. They call it that because of its red colour. (I don’t know either.)

To put this in perspective, Jupiter is roughly the same density as the Sun which should be no surprise being essentially the same gas, 75% hydrogen and 25% helium (measured by mass or ‘weight’ but 90% -10% by volume because helium is heavier than hydrogen).
Jupiter, although all gas (or very nearly all) is 318 times ‘heavier’ than earth but our planet would fit inside 1,320 times over. The smallest star would be the same diameter size as Jupiter but 25,000 times more massive than the earth, not that you’d want this baby too close.

Even if it did not quite make the grade and had to settle for being a brown dwarf, it is still very hot and will stay that way for a very long time because being small with a surface area to match, it takes a long time to cool. Eventually though, nature will have its way and our little brown/red dwarf will fade to become a black dwarf, yet another ‘type’ of star.

The tendency of the clouds in many galaxies to produce stars in batches mean that not only do we see planets revolve around stars, many stars revolve around or in step with other stars too. This is commonly demonstrated as twin stars (binary pairs) orbiting each other in a space Methodist dance, referred to without imagination as a wide pair.
Those in a more intimate embrace tend to exchange bodily material (gas) and while not physically touching, are still referred to as ‘contact’ binaries.
While the more restrained wide pairs evolve separately, they are still married to one another by gravity. Most binaries, double stars to us, appear close to each other and we could assume both about the same distance from us, but in reality one can be much further away only appearing to be close from our perspective.
Only very occasionally, can we find a pair that orbit each other on an ‘edge-on’ plane that aligns with our position so we can see a change or dimming of the light as one passes in front of the other from our vantage point. Nonetheless, twins and triplets are the most common form of star in most galaxies like our own Milky Way.


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How Many Galaxies In The Universe?

Cover: Astronomer Gerard Bodifee with wife TV Presenter Lucette Verboven

Day Six. By this stage in the life of the Universe (11,500,000,000 years ago) there exists something of the order of 170,000,000,000 (170 billion) galaxies each containing between tens of millions and billions of stars.

The name ‘galaxy’ is from the Greek word for milk which is how they described the whiteish appearance of the band of light we know as our home galaxy. Each of the 170 billion galaxies is indeed a group of stars, but much more than that. They almost certainly hold billions of planets, star systems, star clusters and in most cases, a massive black hole near the centre. They also contain a lot of material in the form of vast clouds of gas and dust particles that are mostly the remains of stars that have exploded at the end of their lives.
It has become clear that every galaxy has more mass (the ‘weight’ of something on earth) than we can measure by adding up what we can see. (A cannon ball in space may be weightless but it would still make a mess if it hit you because it still has the same mass.) This non-reflective material is predictably called ‘dark matter’ which incorporates ‘dark energy’. As Einstein showed, matter and energy are different forms of the same thing.

Galaxies come in a range of sizes and types from the dwarf galaxies with only 10 million stars to the big boys that can have one hundred trillion (that is, a hundred million million). 100,000,000,000,000. That’s a lot of zeros and it’s hard to imagine a number so large, especially when we are talking about very hot objects the size of our Sun, which itself is a million times bigger than the earth.
In between there’s not a lot going on, but technically, intergalactic space is not empty, but just as near to it as all get out, maybe 1 atom per cubic metre, which is sparse by anyone’s standards. In the popular press, quoting distances is done in light years, however the scientists in this field tend to use the parsec, which is 3.26156 light years. One might be forgiven for thinking that it’s not exactly a round number, an easily remembered number or one that trips lightly off the tongue, so why use it?
When we see a star, at the same time we also see stars further away. Six months later, when we are on the opposite side of our orbit around the sun, that particular star will appear to have moved slightly compared to the background stars. That’s because we are looking from a different angle.
You can close one eye and look at something close, then look through the other eye and it seems to move against the background. The parsec number is defined by measuring this angle. If it appears to move by 1/3600th of a degree, that is one parsec (like 3,600 seconds in an hour) the light would take 3.26156 years to reach us. The cosmologists need really big numbers and even light years aren’t big enough for the job, so parsecs it is.
Over the years, a fair number of galaxies have been catalogued, tens of thousands in fact but here is the interesting bit, there are 5 main catalogues and they don’t have all the same galaxies listed. Even when they are, they have different identification numbers.

Take Messier 109 for example. In the Messier catalogue, as you would expect, it’s number 109 but in the other catalogues it’s also code number NCG3992, UGC6937, CGCG 269-023, MCG +09-20-044 and PGC 37617. Clever boys.
Now, in the rest of the scientific world, the custom is to assign a name to whatever is being studied, even the least significant, invisible to us, microbe. Here we have entire galaxies, billions of times larger than our whole planet and all they get is a number. Well, up to five numbers actually, depending on how many catalogues we are looking at.

It should therefore come as no surprise that someone thought the galaxies were not getting a fair deal and decided to make a new catalogue, called with great imagination, ‘The Catalogue of Named Galaxies’ to give them a bit of dignity and some spiffy names.
Belgian astrophysicist Gerard Bodifee and the classicist Michel Berger began their new catalogue with one thousand well-known galaxies. Each were given a meaningful and descriptive name using the methods of other sciences like biology, palaeontology and anatomy. For example the aforementioned Messier 109 became the new ‘Callimorphus Ursae Majoris’.
Hell yeah, that’s a much better name.

One cannot pursue the subject of galaxies without mentioning ring galaxies, unusual in that they don’t seem to have much in the middle. They are thought to form in a type of bull’s eye collision when a smaller galaxy passes through the middle, cleaning up so to speak, leaving a neat ring of stars behind.
It looks like that might be what happened to the Andromeda Galaxy, perhaps more than once as it displays a multi-ring structure. There won’t be many rings left after the next collision when our own massive Milky Way smacks into it head on, which it is scheduled to do soon. (Soon in galactic terms, about 200,000,000 years from now.)

Despite the prominence of our galaxy and the millions of other large and very large galaxies, in sheer numbers, dwarfs rule. In fact you could say most galaxies are the smaller variety, perhaps only one hundredth the size of our Milky Way and often host to fewer than a hundred million stars.
Some of these are so small, light photons only take 326 years to travel from one side to the other, almost like crossing the street in galactic terms. They have all the same shapes as their larger cousins, elliptical, spiral and irregular, although the dwarf ellipticals require a little imagination to classify them that way.

Checking out our neighbourhood reveals that twenty seven of the local galaxies are dwarfs and that in itself is somehow surprising, but better yet, the mass of each dwarf (equal to about ten million of our Sun) seems to be very similar, regardless of the number of stars. This, it is argued, lends weight if you pardon the pun, to the conjecture that dark energy/matter is indeed the dark horse in gravitational theory.


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