science

A few weeks ago I wrote to you about how everything was made of tiny little lego-brick-like atoms. Later, I wrote about how some things, like gold and diamonds, are made up of the same type of atom-brick. But like most toys made from of lego bricks, most things in reality are made up of many different types of atom joined together not just one type.

Like lego, atoms can be made to join with other atoms to make bigger and more complicated shaped bricks. These bigger bricks are known as molecules. It is this fact that makes the world around us full of very different types of stuff. Although the whole universe, that we know of so far, is made up of just 98 types of atom you can build very different types of things by joining them together in different ways and different arrangements. It is worth saying that although they are bigger than atoms, molecules are still very very small things indeed. Even the big complicated ones.

The above picture shows six lego brick molecules that I made up in my head using just four types of lego brick. It didn’t take me very long to do. Have a go yourself if you have some lego or other building blocks at home. Make some models of molecules and see how easy it is to come up with new shapes using only a few types of brick.

A good example of a very simple and small molecule is water. It is made of one type of atom brick joined up with two types of another. One drop of water contains huge numbers of these molecules rubbing against and sliding around each other. It just so happens that this combination and arrangement of atom bricks makes stuff that is wet in warm weather but frozen solid when it’s cold and that can turn into vapour when it gets very hot, such as in a kettle.

For an example of a much more complicated molecule that contains lots of different types of atom bricks you need look no further than your own hair and finger nails. Much of these parts of you is built from molecules of something called keratin. One molecule of keratin is made of more than 4000 atoms stuck together in a long spiral shape. These molecules stick to each other to make very long, strong chains. If water is just like three Lego bricks of two different types joined together then this molecule is like the Lego Star Wars Death Star - made of lots of bricks of lots of different types. The Death Star model has 3803 bricks to be exact so a keratin molecule has even more parts than that. Even so, it is still very small because atoms are incredibly tiny things indeed.

Because they are all sorts of shapes and sizes each type of molecule acts differently to others. This is why millions of water molecules together in a glass of water are see-through and liquid but lots of keratin molecules create tough bendy stuff like your nails.

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stars

We all know that out in space things go around other things. They circle round and round. Our planet, the Earth, goes around the Sun. Our Moon travels around us. The moons of Jupiter orbit around it and Jupiter itself rotates around the Sun just like we do.

The words we use to describe this movement are a bit misleading. They can make you think that things travel around other things in perfect circles. Around. Round. Orbit. Circle. The fact that the planets and our Sun are sphere-shaped also gets us into the same mindset. So let me tell you something that might surprise you; the planets in our solar system don’t go around the Sun in circles like the drawing at the top of this post. They follow a different shaped path shown in the drawing below:

The shape of these paths are called ellipses. An ellipse is like an oval shape. In space, things go around other things in elliptical orbits not circular orbits. There are a few important things to say about this. Let’s use the Sun and the Earth as an example but the same rules apply to all things in orbit around other things.

Firstly, the Sun is not in the centre of the ellipse. It’s over to one side. If we think of us on the Earth going around the Sun once every year this means that we are at different distances to the Sun depending upon where we are on that path. Because the path is so big and the ellipse is nearly circular we don’t noticeably see the Sun getting bigger or smaller in the sky. However, there are times the Moon is a little bit closer or further away on its elliptical orbit around us and it is possible to measure the difference in size. You may have heard some people get carried away and talk about a ‘super moon’ on nights when the Moon is full and also closest to the Earth - but take it from me, it isn’t very noticeable.

Secondly, the shape of the ellipse can be different. It can be very long and narrow or almost circular. Comets have very long narrow paths, whereas most of the planets have nearly circular ellipses. The long narrow elliptical paths have their centre very far to one side, whereas the circular ones have it almost in the middle. This is why comets come from so far away out in space and go so close around the Sun, sometimes close enough to burn up completely.

Thirdly, the reason for the elliptical shape is gravity. The Sun is heavier and is pulling the Earth towards it. Because the Earth has speed of its own in another direction it doesn’t simply get pulled into the Sun, but these two forces cause the elliptical orbit that it travels upon. This also means that the speed of travel is not the same all the time. Half the time during the orbit our Earth is falling towards the Sun and is speeding up, whereas, after it has passed it at the closest distance it ever gets to it, it flies away from the Sun and starts to slow down. The second half of Earth’s orbit is spent slowing down until it reaches the most distant point away from the Sun when it begins the cycle again speeding up and falling towards it.

So how fast does the Earth travel around the Sun? It depends upon what day you ask and where in it’s orbit it happens to be. It is closest to the Sun (and fastest) around 3rd January each year and furthest away (and so slowest) around 4th July. Instead people give the simple answer as an average of all those possible speeds, which is just under 30 kilometres every second or 66 000 miles per hour. If it helps, thats fast enough to get to the Moon in 3 and half hours! But remember because the Earth travels on an ellipse not a circle half of the days of the year we go faster than that and half of the year we go slower.

The last thing to say is that with elliptical paths you can see that it is much easier for two or more orbits to cross one another, increasing the chance of space objects bumping into each other at high speeds. This makes for a much more exciting Universe and explains why, everywhere we look around the Solar System, things have and still are bumping into other things. Next time you look at the craters on the Moon think about how they got there.

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minibeasts

We all like ladybirds. They are the colourful beetles that we sometimes see in the garden or in the park. They don’t bite or sting, they do a good job by eating the little insects who attack our garden flowers and are even quite friendly - allowing us to pick them up, if we are gentle, and then unfolding their wings and flying away when they have had enough of the attention.

You probably know already that there are different kinds of ladybirds. Most are red and black, but some are yellow and black, some are orange and black , some are white and black and some are black with red spots. They also have different numbers of spots on their backs. Some have two spots, some have five spots, some have seven spots, some have eleven, and so on all the way to twenty-four spots. It isn’t true that a ladybird gets more spots as it gets older - they stay the same number all through it’s adult life. All in all there are 47 different kinds of ladybird in Britain!

The photo at the top of this blog post is a seven-spot ladybird that I found on one of my apple tree’s in my back garden. It was sitting on that leaf when I found it. The seven-spot is one of the most common types of ladybird in Britain. Sadly this year I’ve only seen two so far in my garden, and it may have been the same one twice!

Where do ladybirds come from? Are there baby ladybirds? Well, yes! But they don’t look quite like the grown-up ones. Here is a photo of a baby ladybird I photographed earlier this summer:

Do you remember the famous story about the Very Hungry Caterpillar, by Eric Carle? A ladybird also starts out in life as a little egg on a leaf and then, instead of hatching out as a hungry caterpillar, it hatches out as a hungry baby ladybird. Baby insects of many kinds, not just ladybirds, are called larvae, so we will use that word too. Ladybird larvae hatch out in late spring or early summer and eat the same little insects that the grown up ladybirds eat. A few weeks later, after a whole lot of munching, they make a house for themselves, just like the hungry caterpillar does, called a pupa. They stay covered up in this special house for about a week and then come out as a beautiful grown up ladybird. Here is a photo of two pupae (the word is different for more than one pupa) sharing the same stinging nettle leaf:

At the time I am writing this post, at the end of August, most of the adults will have emerged by now but you might still be able to see the pupae houses that they left behind if you look around carefully. The really interesting thing about ladybird pupae is that every different type of ladybird has its own style and colour of pupa. There are lots more pictures of ladybirds, nymphs and pupae that I have taken this summer on my tumblr photo stream so be sure to have a look there if you want to see more photos.

If you want to learn more about the different kinds of ladybirds you might be able to find in your garden or in the park then I would recommend two fold out poster guides by the Field Studies Council; Guide to Ladybirds of the British Isles and Guide to the Ladybird Larvae of the British Isles. They are small enough that you could take them to the park to help you recognise different kids of ladybird or you could put them up on your wall at home. If you are really really interested in knowing more about ladybirds then I would have a look at the UK Ladybird Survey website - it has lots more stuff about the ladybirds that live in our country.

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stars

Catching Up With A Comet

Photo by ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Ten years ago the European Space Agency launched a rocket into the sky. It whizzed around the sun a few times, speeding up as it went, and then around a few planets, including the Earth three times, on a cleverly planned path to hit a very small target a long way away. Clever is not really a big enough word - you try throwing something at target so far away that it won’t hit it until ten years later! The spacecraft at the top of this rocket is called Rosetta.

At the beginning of this month, August 2014, Rosetta reached its target, a comet speeding its way towards our Sun that at the moment is somewhere between the orbits of Mars and Jupiter. This comet has the rather long and difficult name of 67/P Churyumov-Gerasimenko, because of the two people who discovered it. For the sake of the rest of this blog post, and mostly because I can’t pronounce it properly, let’s just call it comet 67/P. Here is a map of Rosetta’s journey:

Source: ESA

Comets are big dirty snowballs of ice and rock that sometimes come from very far out in space and loop around the sun. We think there are countless numbers of them surrounding our solar system in a dark region of space far away from the light of our star called the Oort Cloud, where they have been for a very long time not doing very much. Comets are different from asteroids - asteroids are made mostly of rock and are only found inside our solar system. Sometimes something, maybe a bump with a neighbour, causes a comet to fall in towards the Sun from the Oort cloud and it begins a long journey slowly picking up speed - it can take millions of years until it reaches the inner solar system. Three or four of these long-period comets fall in towards us like this each year. When they arrive they sometimes loop around the Sun and whizz off again never to return, sometimes they get too close and burn up and sometimes they get ‘captured’ by the Sun’s gravity and start to make much smaller circles inside the solar system where we can see them buzzing past us at regular intervals thereafter - we call these ones short-period comets.

This comet, 67/P, is a short-period comet that goes around the Sun every six and a half years or so and is about 3 kilometres by 5 kilometres in size. Since it was discovered it has been around the sun seven times. It isn’t a perfect sphere as you might imagine it should be. Far from it, as you can see from the photo at the beginning of this post, it is an odd shape.

Of course you already know that comets are things that sometimes are bright enough to be seen in the night sky and they have long tails behind them. So where is the tail on this one? The tails are caused when comets get closer to the sun and some of the ice begins to melt. Comet 67/P is on its way toward the sun right now and it is going to be Rosetta’s job to follow it closely for the next 18 months and watch what happens to it as it starts to melt and its tail begins to grow. In fact it is already starting to melt as this next photo shows:

Photo by ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Unfortunately, like most comets, 67/P isn’t close enough or big enough to be so bright that we can see it from Earth with our own eyes, although it can be seen with a telescope. But you don’t need a telescope. The cameras on Rosetta are sending back the most incredible pictures we have ever seen of a comet close up.

This event is important because this is the closest we have ever been to a comet before. The Rosetta spacecraft is less than 100 kilometres from the comet right now and soon will be about 30 kilometres away. In November, it is going to launch a small landing craft, called Philae, onto the surface of the comet. We’ve never tried anything like this before. We’ve seen plenty of comets in telescopes but have never touched one until now.

Knowing more about comets is important because we think they are very old - as old as our Sun and the planets spinning around it. Learning more about comets may mean we learn more about how our solar system was created 4500 million years ago. When Rosetta finds out some more interesting things I’ll let you know.

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minibeasts

These past few weeks you might have seen some tall-ish green plants with bright yellow flowers at the top. They grow in fields and rough ground all through the summer and one place you can find them a lot is by the sides of roads. This plant is called ragwort. Sometimes ragwort has stripey yellow caterpillars on it. This summer I have noticed lots of ragwort and lots of caterpillars. Maybe like you, I had no idea what these were called. It turns out they are called Cinnabar Moth Caterpillars and they are rather special.

Normally small animals want to be colours that help them hide in the places that they live. Yellow and black is a funny colour if you want to hide on green plant stems and leaves; its a very loud colour mix that can be seen easily! Do you know of other animals that are yellow and black striped? Bees and wasps are too and, as every small boy and girl knows, these insects are dangerous and have nasty stings. They don’t need to hide - their stripes are a warning to other animals. The stripey caterpillar is saying the same thing to other creatures, particularly to small birds who might want to eat it as a tasty snack. It is saying “Watch out, you might not like the taste of me!” and they are right - because the caterpillars don’t taste nice and are poisonous to things who eat them.

Here is the really clever bit; how do these little caterpillars become poisonous? They are not born that way. They eat the leaves of a poisonous plant and become poisonous themselves. Which plant? Ragwort! Ragwort tastes bad and is poisonous to animals who try to eat it, even big animals like horses, so obviously don’t try that yourself, but it is not poisonous to Cinnabar Moth caterpillars and I suppose that they must like the taste of it because they eat a lot of it - many ragwort plants I have seen these past few days have had all the leaves chomped off!

Just as in the story everybody knows, The Very Hungry Caterpillar, eventually these stripey caterpillars make a cocoon for themselves and then turn into a beautiful butterfly. Well not a butterfly actually in this case but a moth. A Cinnabar Moth is a moth that flies in the daytime, unlike most moths who fly at night time, and it also looks a lot more pretty than most moths do. It is poisonous too, which is why it is not worried about having a beautiful bright red colour on it. Here is a picture of what one looks like, but I didn’t take it:

Image courtesy of Wikimedia Commons | Taken by Svdmolen

In the next few weeks there should be a lot less caterpillars and a lot more moths so maybe I will find some and take a photo of one myself to show you. In the meantime have a look and see if you can find any ragwort, caterpillars or moths like these where you live.

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minibeasts

Imagine you are in a deep dark forest. Imagine incredibly tall, slender tree trunks that sprout out of the ground and reach up all the way into the sky. Moving around on the ground is not easy because of the criss-cross of tree trunks that overlap each other. The noise of the wind moving through the tops of the tall trees is very loud. On the floor of this forest it is quite dark but the sky can normally be seen because, unlike in the woods that you and I know, there are not so many leaves on the trees here.

Now imagine that you live in this forest and you want to talk to your family or to your friends. You know they are not so far away but you can’t see them all of the time because of all the trees in the way. How would you find them? How would you let them know you are there and you are OK? You would probably shout very loud to talk to them. Louder than the noise of the wind blowing through the leaves. Your shouting might sound like this:

listen to ‘Grasshoppers & Crickets’ on Audioboo

(sorry for the funny robotic sounds - Audioboo thought it was being clever by trying to correct the hum of the crickets!)

Welcome to the world of grasshoppers and crickets! I recorded the sound of these grasshoppers talking to each other in a field close to my home. Here is a photo of that field. It is just a meadow of grass in July.

To you and me it is a meadow of grass about waist height but to a small insect it is that great forest I have described. I also took the picture of that pretty green grasshopper at the top of this blog post in the same field on the same day. It was about the size of the tip of my thumb. Shortly after I took a photo of another grasshopper that I found in the same patch of grass:

Whoa! Wait a minute! They look very different but they both look like grasshoppers, don’t they? What is going on here?

It turns out that in my country, Britain, there is not just one type of grasshopper. There are 28 types! There are 15 different types of grasshopper and 13 types of cricket. Some of them live here all the time and some are tourists who come around from time to time. Standing up and seeing them from a distance they have always looked the same to me. The first time I noticed a difference between them was when I took these two photos. The second darker one I noticed was quite a bit bigger than the first - about half the length of my thumb. The photos close up show all sorts of other differences. What differences can you see between them?

So you see a grasshopper is not just a grasshopper. Any grasshopper you see in the summertime belongs to its own special family and there are other types from different families that look similar from far away but different close up. Next time you see one take a closer look if you can and see if you can find out what it’s family name is. If you want some help with that I am using the Field Studies Council Guide to British grasshoppers and allied insects fold out booklet and you might find that helpful too.

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stars

Seeing the stars is a hard thing to do when you are young. This is one of the reasons why I want to tell you some useful things about stars on this blog - so that when you do get the chance to see them with your own eyes you are able to look for the things that are interesting. When you are young every minute of star-gazing time is precious.

I’m writing this in July. In the UK, where I live, it is summertime. This should be a good time for seeing the stars because the skies are often less cloudy and it is normally nice and warm outside. The evenings are warm but they are also light, which is where the problem begins. That big star very close to our planet that we call the Sun is still in the sky or has only just gone down under the horizon and the sky is still too bright to see any stars. They are there, of course. They are there all day but imagine trying to see a small candle flame at the end of the road when someone is shining a powerful torch up close in your face - you just won’t see that candle.

This time of year most children go to bed when it is still light outside. Or should do. By the time the stars are properly out and nice and bright it is nearly midnight! That is no good at all even for many grown-ups. Things are different in winter in the UK. Nights are much longer and around Christmas time it can be dark by four o’clock in the afternoon and it will stay that way until nearly eight o’clock in the morning. That gives us 16 hours of darkness where we might be able to see the stars! That sounds much better, doesn’t it? But it is winter and it is more likely that there will be bad weather and clouds in the way that block out the stars. If there aren’t it is quite likely that the sky will be beautifully clear and full of stars but it will also be very cold outdoors and after a short while you’ll want to go back inside and warm up.

When it is warm outdoors in summer, the sky is light in the evening. When the sky is dark in the evening in winter, it is often also very cold. So you see it really is not easy to watch the stars with your own eyes when you are young living here in Britain. I have been thinking about this problem and I have some ideas about how to get outdoors and see the night sky. Here are my ideas:

Idea 1 - If the weather forecast says the sky is going to be clear one night in Spring (February to April) or Autumn (September to November) that might be the time to go outdoors when the sky gets dark earlier than the summer but it is still warmer than in winter.

Idea 2 -  It is difficult to see most stars on warm, light summer evenings but it is sometimes possible to see planets. Mercury and Venus can sometimes be seen in the sky shortly after the sun goes down and when they are there they are usually very bright. Sometimes Mars and Jupiter are also in the sky at this time of year and can be seen earlier in the evening twilight before the stars come out. It is best to look at a star chart on a phone application or on the internet before you go out to know if there are any planets up that evening and where in the sky they will be.

Idea 3 - The same is true for the Moon in summer. It will be in different parts of the sky at different times of the month but there will be one week every month when the Moon will be in the sky and easily seen during the early evening, if the weather lets you.

Idea 4 - On a cold clear winter evening wrap up really warm and go outside for just ten minutes and see how many stars you can see. Don’t worry about looking for anything in particular. Just stand underneath them and enjoy the view. Then keep that memory safe. Whenever you see a photo of stars you can remember that you stood under the same stars yourself. Even just ten minutes of sky-watching is better than no minutes.

Idea 5 - Keep reading my blog posts about stars as and when I post new ones on this web site. When you are able to get out next and see real stars you may be able to find some that I’ve been talking about and know some more about them.

There is nothing like seeing the stars for yourself in real life, rather than hearing people talking about them, or seeing pictures of them on television or in a picture.

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stars

Arcturus peering through the clouds at night | Image copyright Graham Jarvis 2014, all rights reserved

Today I’m going to tell you about a star. Just one. Its not a particularly special star but there is a very good reason that I am going to talk to you about this star first, of all the many many stars in the sky. It is because it is easy to find. If we are going to to talk about stars in the night sky together I want to you to be able to look up and see what I am seeing. Even if you don’t know much about stars, I think I will be able to teach you how to find this one.

The name of this star is Arcturus. Funny name, isn’t it? All stars have names given to them by people who watch stars for a living but some stars have nick-names that are often very old. Arcturus means something like “bear-watcher”, in the Greek language. Why would a star watch a bear? Well it goes back to the days before television and street lights, when people had little to do in the evening but look up at the stars on clear nights. They imagined they could join the stars with lines (like a dot-to-dot puzzle) and draw shapes with them. Its the same as when you see a cloud in the sky that looks like something familiar. One shape high up in the sky they thought looked like a big bear. It also was in the northern part of the sky and north was the direction that Greek-speaking people knew bears lived. The star we are talking about, Arcturus, isn’t part of this dot-to-dot shape but is nearby - like it might be at a distance watching the bear-shape. So that is how it got its name.

These days we don’t see bears in our gardens quite so often and street lights make the night stars a bit harder to see and so the dot-to-dot bear shape is harder to notice. I am sure you have seen another shape up in the sky that we would both recognise. To me it looks like a saucepan and handle. To others it looks like an old-fashioned plough; the type that used to be pulled by horses on farm fields. Have you seen that shape before? It is called The Plough or The Big Dipper and is actually part of the nose and back of the big bear. Don’t worry if you you can’t see the whole bear - I still can’t make out all of it either. The Plough shape is often found high in the Northern part of the sky. I made a picture of the shape so you can look at the night sky and find it yourself one night:

So if that is the nose of the bear then where is the bear-watcher? It is not so far away. If you draw an imaginary curved line using the curve of the saucepan’s handle to guide you then you will find a very bright star a little distance away. People who like watching stars remember this way of finding it by saying they arc to Arcturus. Look at the dotted line curve on the diagram and follow it to the bright star.

Arcturus is the fourth brightest star in the sky. Two of the even brighter stars can only be seen in places much further south than where I live in England and so, for me, Arcturus is the second brightest star in my sky. The best time to see it is in the Spring and Summer.

I really hope that you get a chance to see it for yourself in your sky because I want to talk more about it another time and I want you to know that it is a real thing. Not something that someone made up in a story. But I will understand if you don’t get a chance to see it by the time I next write. If fact, the difficulties of being able to see the stars when you are young is what I will talk about next time.

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