Strange optical illusions

Concentrate on the cross in the middle, after a while you will notice that this moving purple dot will turn green! Look at the cross a bit longer and you‘ll notice that all dots except the green one will disappear. More mind bending illusions can be found on this powerpoint (right click, file save as) and this website. Enjoy!

Ever wondered who was bigger – King Kong or Godzilla? Well, you’re still not really going to find out, but it's one of 20 interesting questions you'll find about your senses on the BBC website’s Senses Challenge. Have a go, see what you think…and find out what goes with white chocolate, broccoli, caviar or bacon? Eww, just the chocolate please. I got 12/20 - post a comment about how many you got!

Wave Machine

What you need

A roll of gaffer tape. Duck or Elephant brands are the best. Which is a shame, since they're twice the price of the others, but so it goes.
Lots of wooden kebab skewers.
More fruit pastilles than seems reasonable.
Two tables or chairs of the same height.
a ruler, or a number of fingers that are approximately the same width as a ruler.

What you do

Stretch the gaffer tape between the furniture. It's probably best to try this with a 2 metre span the first time, but I've done spans of up to 4 metres with some success. You need to stretch the tape taut, which means sticking it down firmly - go right round the table or chair if you can. Mind that varnish!
Starting from one end, stick kebab skewers to the tape so they stick out evenly on either side. This is why you need good-quality tape - you'll need strong adhesive to hold the skewer. A damp day will ruin the adhesive, too - if your skewers fall off, this could be why.
Space the skewers about a ruler's-width apart. The exact spacing isn't critical, so long as they're fairly evenly-spread. Keep adding skewers until you've reached the end of the tape.
Now put a fruit pastille on each end of each skewer. You might think you'd only need twice as many sweets as you've used skewers, but mysteriously they tend to disappear. Further experimentation is required to ascertain precisely why. Much more experimentation. Way more, in fact.
However, be careful when pushing the sweets onto the skewers. Careful in case you accidentally poke your finger, but also because you want the skewer to stay balanced - it should rest horizontally. You may need to push things around a bit to make sure your wave machine stays balanced all along its length.
Once that's done, your wave machine is ready. Hold the skewer at one end, swiftly pulse it up and down, then let go. You should see the pulse travel the length of your tape, reflect off the far end, and return to the start. If you drive the end continuously, you can set up a standing transverse wave, too.

What's going on

Transverse wave machines like this have been around for years, but they're normally very expensive. Not only does this version cost far less, it often works better too!

The tape acts as a torsion spring, but - and this is key - one with a very low spring constant, and very low damping. The fruit pastilles and kebab skewers provide a high angular momentum, too. The result is a wave that travels down the tape at a surprisingly slow speed, as the tape struggles to return to its central position.

With a little practice, you can demonstrate not just standing waves, but things like wavepacket dispersion too. Now that's something you didn't expect to see done with a fruit pastille, right?

(the photo, by the way, is of an early prototype of this demo. It works quite well with elastic, as you see here, but the gaffer tape version is simpler, more reliable, cheaper, looks better, and is easier to set up)

How round is your planet?

When is a planet not a planet? That is the question. At least according to the International Astronomical Union (IAU). For the first time, the organisation will be officially defining the word "planet", and it is causing much debate in the world of astronomy. There is only one thing that everyone seems to agree on: there are no longer nine planets in the Solar System.
The whole debate was sparked off by the discovery in January of last year of a potential 10th planet, temporarily named 2003 UB313, which is bigger than Pluto.
Pluto is already an unusual planet. It is made predominantly of ice, and is smaller even than the Earth's Moon.
In 1992, scientists at the University of Hawaii discovered a new collection of objects beyond Neptune called the Kuiper Belt. Some suggest Pluto should no longer be considered a planet, but a Kuiper Belt Object. One researcher has come up with a clear planetary definition he would like to see the IAU adopt. In a nutshell – is it round?
This definition could lead to a Solar System with as many as 20 planets, including Pluto, 2003 UB313, and many objects previously classified as moons or asteroids.
New categories of planet could be introduced. Mercury, Venus, the Earth and Mars would be "rocky planets". The gas-giants Jupiter, Saturn, Uranus and Neptune would be a second category. Pluto, 2003 UB313, and any other objects passing the "roundness test", would be reclassified as a third type of planet - perhaps "icy dwarfs". Whatever the final outcome, by September there will no longer be nine planets in the Solar System. What? What about My Very Easy Method Just Shows Us Nine Planets? How are we supposed to write a rhyme to remember twenty or so planets? There’s no respect…
For more information check out the BBC News website
Pluto - NASA

Super massive black hole at the centre of our galaxy

Listen Now - 17062006
Download Audio - 17062006

How do you prove that something is there when it can't be seen? Although for
decades the existence of a super massive black hole at the centre of our galaxy
was viewed with scepticism by many astronomers, a team at the University of
California, Los Angeles did the maths to prove it and have taken spectacular
pictures of the galactic centre.

Transcript

You wouldn't think they'd miss a lump the size of a zillion suns lurking down
there in the middle of the galaxy, would you! But it was surprisingly hard to
locate. Professor Andrea Ghez of the University of California, Los Angeles, led
a team who brought it off.

Andrea Ghez: The idea of super massive black holes, black holes that
have a mass of maybe a million to a billion times the mass of our sun wasn't
predicted theoretically, unlike the little black holes that were first thought
of theoretically and then demonstrated observationally. So people didn't believe
that these things could exist, they had no idea how they would form, so why
would there be one at the centre of our galaxy?

Robyn Williams: So how was the argument turned around?

Andrea Ghez: The argument was turned around by doing the experiment to
look for a super massive black hole, and the way we did this was using
principles from freshman physics, measure the masses of a thing by watching how
something orbits around it, just like planets orbiting the sun; you can weigh
the mass of the sun and figure out how small it is. You can actually weigh a
black hole at the centre of our galaxy by watching how stars orbit the centre of
the galaxy. This way you prove that there's a lot of mass inside a very tiny
volume, and that's the proof of a black hole.

Robyn Williams: I suppose, it being black, you can't actually take a
picture of it, can you?

Andrea Ghez: We've seen the plasma around it, and this is a material
that's very hot because it's falling into the black hole, so in that sense you
do have another signature of a black hole by looking at things being heated by,
again, it's the gravity heating things up locally. But from that you can't prove
that it's a black hole but you can look at its dining habits.

Robyn Williams: What it's about it eat. Remind us what a plasma
is.

Andrea Ghez: A plasma is a very hot set of electrons and protons that
are separated from each other, whizzing around.

Robyn Williams: So it's the ingredients of an atom that's not in a
kind of atomic structure, as such, it's just the mash.

Andrea Ghez: Right. Plasma is a gas that's so hot that the electrons
can't stay bound, so they separate out and the atoms aren't whole, you just see
the electrons and the protons and neutrons.

Robyn Williams: So how far away is this plasma soup from the black
hole itself?

Andrea Ghez: The plasma soup is quite close to the black hole. It
extends roughly the size of our solar system. I guess it's a good size to think
of in thinking about the plasma.

Robyn Williams: Well, I would have thought that close enough to be
swallowed ages ago.

Andrea Ghez: It is getting eaten up but it's continually
replenished.

Robyn Williams: How?

Andrea Ghez: From stars that lose their outer shells, that stuff that
falls in towards the centre of the galaxy gets heated up by the black hole and
that's the plasma that you see today.

Robyn Williams: So you're suggesting, in some ways, that the black
hole is characterised by a kind of halo effect of this plasma, and this is what
you might expect to find in other galaxies as well?

Andrea Ghez: Absolutely. Whatever we see in our own galaxy, you expect
to see in other galaxies. Our galaxies are completely garden variety, ordinary
galaxies, so whatever is here must exist in many other galaxies.

Robyn Williams: Why so prosaic? Why can't ours be unique?

Andrea Ghez: Whenever astronomers think that we are unique, we get
ourselves into trouble. I think the general argument is we're probably pretty
typical; our sun is pretty typical and our galaxy is quite common. We see things
that look like our galaxy in outer space.

Robyn Williams: Give me an idea of the ways in which that black hole
may have grown. Was it there more or less in the beginning of the formation of
the galaxy, and has it got bigger? What else has happened to it?

Andrea Ghez: There was a large debate just a few years ago; which came
first, the galaxy or the black hole? And today we actually recognise that they
had to form together. We've recognised that there's a connection between the
size of the black hole and the size of the central part of the galaxy, and the
only way that that could exist, that connection, is if they were formed
together. So they came together and they grew together. Black holes get bigger
by swallowing material around it, so they grow throughout their life, and our
galaxy's also growing throughout its life.

Robyn Williams: Is there a limit, like there is in stars, to that sort
of growth? In fact, I think there is a formal limit to the size of stars,
indeed. And is there a point at which a black hole cannot grow anymore?

Andrea Ghez: That's a good question and people are actually posing
that question today, and we don't have evidence but there's certainly theories
that there may be ways in which black holes regulate how large they get, but we
don't know the answer today.

Robyn Williams: We may have many black holes kind of budding off.

Andrea Ghez: Maybe. Or maybe they get so big that they keep things
from falling onto it. In other words, when they get big, they go on a diet.

Robyn Williams: So they repel stuff. I see.

Andrea Ghez: That's one idea. We don't know for sure.

Robyn Williams: What was the paper you published in December?

Andrea Ghez: We published a paper on the first view of the centre of
our galaxy using something called laser guide star adaptive optics. It's new
technology that has allowed us to get the most pristine view of the centre of
the galaxy that we've ever had before.

Robyn Williams: So you can actually, in other words, picture it?

Andrea Ghez: We can picture it. We can make the prettiest picture
you've ever seen. We've had the telescope experience Lasik surgery, so the
pictures that we're obtaining today are much clearer than what we could see
before which allows us to see much more detail than what we could see
before.

Robyn Williams: What's it like?

Andrea Ghez: What we see at the centre of the galaxy with these
pictures taken with infrared light, which is just long ward of what your eye
detects, we see light from stars, we see light from the dust that's there, so we
can tell that's it's a fairly hot environment. The pictures that we take, we
take every year, so what we actually see is the stars moving and we see them
moving at incredibly high speeds, which allows us to first discover the black
hole and then to explore whether or not there's any extended halo of dark matter
surrounding the central black hole. There may be an entourage of mini black
holes. That's what we're looking for today.

Robyn Williams: That dark matter is not itself black hole.

Andrea Ghez: Right. So that maybe there's an extended contribution of
dark matter around the black hole itself.

Robyn Williams: Where might people see this picture? Have you put it
on the web or anything like that?

Andrea Ghez: We have a website. If you got to
www.astro.ucla.edu/research/galcenter you'll find our pictures there.

Robyn Williams: That's astro.ucla.edu/research/galcenter to look at
the centre of the Milky Way. Andrea Ghez is professor of physics and astronomy
at the University of California, Los Angeles. And I have no doubt she was a
formidably clever young girl at school.

Guests

Prof Andrea Ghez
Department of Physics & Astronomy
University of California Los Angeles
http://astro.ucla.edu/~ghez/

Further Information

UCLA Galactic Center Group

What is this photo?

SNACK CARD CHALLENGE!! When was the last time we had a snack card challenge? So long ago I can't remember. If you can tell me what is going on in this photo and where it came from then a 100 baht snack card (not one of the dodgy year 9 ones!) could be yours. Add a comment to this post (first name and tutor group only). Here are some clues to help:

• I am microscopic in size
• I am part of an amphibious animal
• I am undergoing an essential life process

Ps Students only!!!!!!!

Getting ketchup out of the bottle…

What you need:

A bottle of tomato ketchup (not the squeezy kind, that's cheating).
A drinking straw (the bendy kind).
A hotdog (the 'cooked through so it doesn't kill you' kind).

What you do:

Prepare the hotdog for ketchup addition.
Invert the ketchup bottle over the hotdog.
Note the lack of ketchup movement.
Note the continued lack of ketchup movement.
Turn the bottle upright again.
Stick your thumb over the end of the straw, then plunge it into the ketchup, ideally so it goes right to the bottom of the bottle.
Remove your thumb, and bend the straw over the neck of the bottle.
Hold the bottle neck and straw with one hand.
With a deft flick, invert the bottle and straw over the hotdog.
Observe the dramatic flow of ketchup.
Wonder if, on reflection, that wasn't a tad more ketchup than you wanted on your hotdog.

What's going on:

Ketchup doesn't come out of the bottle for a number of reasons, but fundamentally because it's very thick. For the ketchup to get out, air has to get in to fill the space it leaves behind, and the thick ketchup tends to plug the neck of the bottle. Plugged neck = no air in = no ketchup out. Stalemate.

The straw provides an alternative route for the air: it can get in simultaneously with the ketchup getting out. Free flow of air = free flow of ketchup = empty bottle in seconds flat. Try it, it's quite dramatic. You stick your thumb over the straw when you insert it so it stays full of air, rather than itself getting clogged with ketchup.

Exactly this idea is used when refuelling Formula 1 racing cars - the tanks can be filled much more quickly if air is pumped out while fuel is pumped in. Of course, the fuel should be high-octane petrol rather than ketchup. If it isn't, somebody's made an almighty mistake, and you shouldn't eat the pitlane hotdogs.

An interesting experiment in artificial intelligence (A.I.)

Think of an object and the A.I. will try to figure-out what you are thinking by asking simple questions. The object you think of should be something that most people would know about, but, never a specific person, place or thing. I though of "bottle opener" and it took 26 questions - add a comment below with your "object" and how many questions it took - see if you can crack the A.I. - remember the object must be an everyday one. (nearly forgot - click on the image to go to the site!)

Do you know what stem cells do? Click him to find out

Have you used photo story yet?

The Legendary Diet Coke & Mentos Experiement

I tried this experiment with my year 7 class out on the front field last term - ask any of the students in 7B what happened! These guys took it one step further and used over 400 litres of coke and 500 mentos - see the effect below - classic science!




How does it work? Read here. What can happen if you try to do it in your stomach? Watch below.

(warning - do not watch if you are easily offended!).

Polystyrene Tile Glider

For those moments when you absolutely positively have to make something fly, a paper aeroplane is a perfectly good stop-gap. But if you've a little more time, why not try something a little more ambitious? Particularly when it's even simpler to make, since there's no folding or creasing involved.

What you need:

A polystyrene ceiling tile. You can buy these in packs of ten from DIY shops - they're quite cheap, and each tile makes two gliders. Go for as smooth a surface as you can find - some tiles have ghastly patterns on them.
A few paperclips.
Sticky tape.
A cutting mat (or large sheet of cardboard), craft knife, long ruler or straight edge, and a responsible adult who doesn’t have shaky hands …

What you do:

Cut the tile from corner to corner. Be very, very careful here …
Equally carefully, cut a large triangle out of the middle of the long edge. Each side of the triangle should be about 10cm long, but it's not critical. You'll end up with a shape that looks a bit like a stealth bomber, only much smaller, white, made of polystyrene, and costing about $2bn less. The 'front' is the right-angle corner, so the 'wings' are the... er... bits sweeping back on either side.
Here's the tricky bit: you need to bend up the last 10cm of the wings, just a little bit. You'll find you can gently curl them against the table - gently, to avoid snapping them. Half a centimetre of bend is plenty, but try to get it even on both sides.
Now tape three or four paperclips under the nose of the glider. You'll need to experiment to see how many works best for you.
To launch the glider, hold it from the triangle cut-out, pinched between your thumb and forefinger. Point the nose just slightly down, and gently push the glider away from you, along the line of its nose. With luck, it'll waft gracefully off across the room.

What's going on:

If your glider flies at all, you'll probably notice that it flies spectacularly well. Head to a school hall or gym, and see just how far it'll go. Quite likely, it'll go much further than a paper dart would, and possibly it'll go further than the room does.

A flying wing is a remarkably efficient aerodynamic shape. The wing area is huge and the weight is low, which means it can fly quite slowly - which causes less drag. Also, your glider is stable not because of a clumsy tail or fins, which would add drag, but because of the way vortices of air form over it. Bending the wingtips up is crucial to help shape those vortices.

Here are some small but useful pictures of the glider from The Big Bang tv show.

We also made a winch launch system for the gliders, which you'll find here.

And if you want to know more about flying wing designs, this is a good place to start.

Build a colourful and tasty model of a DNA strand - a perfect excuse to go and buy lots of yummy sweets from a pick and mix shop! (and eat them!)

You will need:

2 different coloured long candy or liquorice cords with a fondant centre
1 large packet of midget gems or similar sized soft sweets
1 box of cocktails sticks
Needle and thread

What to do:

Take the two candy cords - assign one colour to represent the pentose sugar molecules and the other to represent the phosphate molecules.
Cut the candy cords into 2 - 3 centimetre pieces.
Using the needle and thread string half the candy pieces together lengthwise alternating the two colours to form a chain.
Repeat step 3 with the remaining half of candy pieces to form a second chain of the same length.
Lay the two chains down side by side so pieces of the same colour are opposite one another.
Count the number of pentose sugar molecules you have in one chain (you should have the same number in both chains). Then take this number of cocktail sticks. These represent hydrogen bonds that hold the base pairs together.
Divide the packet of midget gems and into four different colours. Assign names to the each of the four colours to represent the nucleotide bases - adenine, cytosine, guanine or thymine.
The bases have to be paired up on the cocktail sticks. Adenine always pairs with thymine and guanine with cytosine, so make sure you get the right colours matching.
Push each end of a cocktail stick into candy pieces representing pentose sugar molecules lying opposite one another - the cocktail sticks should join the two chains together so they look a bit like the rungs of a ladder.
Hold the end of each chain and twist slightly to get the double helix effect for your DNA model.

What’s happening?

The structure of DNA is known as a double helix and was determined in 1953 by Crick and Watson. DNA stands for Deoxyribonucleic acid and is a code containing all our genetic information. We could call it the recipe for life. The Human Genome Project (HGP) sequenced and mapped all of the genes - together known as the genome - of members of our species, Homo sapiens. Completed in April 2003, the HGP gives us the complete genetic blueprint for building a human being.
For more information on the Human Genome Project (HGP)
Find out more DNA facts and trivia. Maybe even do the DNA dance. Come on sugar! Swing yer bases!

Ok, so here's one not to try at home!!!!!!

What you need

A leaf blower
Some toilet rolls
The cardboard tube from a roll of cling-film
The end of a cardboard box
Some tape

What you do

Cut a disc out of the cardboard box, larger in diameter than your toilet rolls, and cut a hole in the middle of this just large enough to pass the cardboard tube through. Do that, and tape the disc in place, so you've made what looks a bit like a very short stubby sword with a handguard. We'll call it a 'handle.'
Hold the handle with one hand, and put a toilet roll on the end your hand isn't holding. If you're doing this right, the guard should be between your hand and the toilet roll. Tilt the whole thing so the toilet roll is leaning into the guard, and finally make sure the loose flap of toilet paper is draped over the top of the roll, facing away from you.
Now, aim the leafblower high, turn it on, and very carefully bring the toilet roll up so it's just beneath the flow of air.
You should find that the airflow spools the toilet paper off the roll, sending it flying high in the air and emptying the roll in seconds. This is quite (a) funny, (b) spectacular and (c) ecologically unsound – so we’re not recommending you do it toooo often. But it’s fun while it lasts.

What's going on

The fast-moving jet of air from the leafblower is at a lower pressure than the air around it. So, when you bring the toilet paper close, the high-pressure air beneath it lifts the paper and shoves it into the airstream. It's accelerated, of course, and that sends the arc of paper spooling out across your room/playground/garden/mesmerised dog/etc.
It's a wonderfully fun trick - just make sure the cardboard disc guards your hand from the fast-spinning toilet roll. It's possible to collect a nasty friction burn if you're not careful. Believe me, I know.
Also, do think about what happens to the paper afterward. The experiment is a heap of fun, the science is solid... but the aftermath is messy.

Do you recognise these answers?

Here are a few examples of how not to answer questions in your Annual exams:Answer 1 Answer 2 Answer 3 Answer 4 Answer 5

They are genuine answers from a science exam! Seriously though, the following information in link and learn (under each topic heading) may be useful in your revision:

• Year 7 & 8: revision quizzes, key words, checklists and questions (click here)
• Year 9: past paper questions by topic, key words and definitions (click here)
• Year 10: topic revision notes, past paper questions (see IG past papers)
• Year 12: JOBU's & ANRO's websites, absorb Physics and Chemistry on link and learn

If there is anything else you would like to see on this site (apart from the 2006 Annual exam papers and answers!) let us know

Science sites worth a visit

If you are looking for a good biology site then biology4kids.com could be for you. This site offers and introduction to the science of biology. You can start by choosing one of the sections or try the site map that shows you all of the topics that are covered. If you surf the site and get lost in all of the information, use the search function on the side of the page. The same people also host chemistry4kids.com and geography4kids.com - some useful material on there for the environmental management and ecosystems students.