Number 7: The magnetic grape

You remember how in school your teacher told you that only things with iron in them are magnetic; spoons, nails that sort or thing? Well your teacher didn't get that quite right. Because it turns out that  everything is magnetic to some extent. Even grapes. And that's why this happens:

If you want to try this yourself..

You'll need:

• 2 grapes
• A wooden skewer (NOT A STEEL ONE)
• A pin
• Something to stick the pin through so that it points upwards on a stable base. I used an old film canister, but bit of cork would do just as well.
• A neodymium magnet. The stronger the better but you probably want one with at least 20 Kg pull.

Safety:

THIS IS REALLY IMPORTANT

The neodymium magnets are really powerful. So...

1. Don't let kids play with them.
2. Don't put them near your credit cards, phone, watch or any other electrical equipment.
3. Don't put 2 magnets anywhere near each other because they'll fly towards one another, shatter and send chunks flying.
4. If you have any medical implants don't go anywhere near them.
5. Read the safety instructions that come with the magnets.

What to do:

1. Push the 2 grapes onto either end of the skewer

2. Push the pin through the cap of film canister, so that its pointing upward. Put the cap back on the canister.

3. This is the tricky but. You need to balance the skewer and grapes on the point of the pin. If you get close then adjust the balance by pushing one grape further onto the skewer.

4. Once you've managed that just put the edge of the magnet near one of the grapes and watch them spin.

What's going on?

There are actually numerous types of magnetism. At school we only learn about ferromagnetism. Then there's paramagnets (which are attracted to ferromagnets) and diamagnets (which are repelled by ferromagnets). These 2 types of magnetism are much weaker than ferromagnets so you generally can't see the effect. Which is why you need a set up like this and a powerful magnet to observe it.

Since the water in the grape is diamagnetic its repelled by the strong ferromagnet near it and that makes the grapes spin on the pin. 

You can demonstrate the same principle another way shown here.

Incidentally this effect is central to how MRI scanners in hospitals work.

Number 6: Count to 60 (or even 144) on your fingers

The only reason we use a decimal number system (mathematicians call this base-10) is because we have 10 fingers. But I've always thought that base-10 is a bit rubbish and the ancient Sumerians agreed with me. They preferred base-60. This was probably because they figured out a way to count to 60 on there hands.

Here's how its done:

Instead of counting out each number with a whole finger, count out segments of fingers using your thumb as a marker. That way you can count to 12 on your left hand. For example in this picture I've counted to 5.

5 using the Sumerian system

Then when you get to 12 put one finger down on the right hand. Start counting the segments of your left fingers again, then when you reach 12 put a second finger down on the right. And so on.

29 on my fingers using the Sumerian system.
5 on the left hand plus 24 on the right hand (remember each finger in the right hand counts for 12)

So each finger segment on the left counts for 1. And each finger on the right counts for 12. Which means that when all the fingers on the right hand are down you've got to 60 (5 X 12 = 60).

There's still traces of this counting system left today, just think about how we measure out time; 60 seconds in a minute, 60 minutes in a hour and hours going from 1 to 12.

P.S. I suppose the Sumerians actually missed a trick because if they counted each segment on the right hand as 12 then they could have go to 144!

Citizen science: Phylo the sequence alignment game

Citizen science in the form of computer games are coming think and fast. Phylo is the latest offering and I've got to say its pretty additive.

Phylo, match up the coloured blocks, score points, help scientist fight diseases!

This time the aim is to help scientist who study genomes match up the DNA in the genes from one species with those of another species. The is important because if a gene is more or less the same in many different species then it probably means that its particularly important.

So how come scientist don't just let computers work it all out? Well it turns out that computer programs are pretty rubbish at this sort of problem because they painstakingly work through all possible ways to align the bits of DNA and that takes ages. But the human brain is really good at spotting patterns, so we get the job done much more efficiently. Have a go at the game and you'll soon find you are scoring better than the computer.

The game is really quite simple, each building block of the DNA (remember those A,T,G & Cs) are represented by a different colour block. All you have to do is slide the blocks around and get the colours on one line to match up with colours on another line. You get points for every match and points taken away for incorrect matches or gaps.

The other really nice thing about Phylo is that you can enjoy it for its own sake. You don't have to know a thing about DNA, genes or genomes to be able to play it. So literately anyone can have a go.

If you'd like to read more you can find the original journal article here.

Citizen science: RNA folding

Folding computer games seem to be all the rage. I wrote about the protein folding game fold.it the other day.

Now here's another one, this time its helping solve the RNA folding problem. 

So if you liked the protein folding game give this one ago as well find out about another critical molecule in our cells.

Number 5: The rolling can

You can have a lot of fun with static electricity and here's a great example.

What you'll need.

• A balloon
• An empty drink can.  It needs to be aluminium. It may have a little sign on it that says ALU or try sticking a magnet to it. If the magnet sticks then its steel, if not then its probably aluminium.
• A hairy head (without any gel or hairspray) or a woolly jumper (thats a sweater if you are in the USA).

What to do.

• Blow up the balloon and tie a not in it.
• Rub the balloon against your hair (or woolly garment).
• Lie the can down on a flat surface.
• Hold the bit of the balloon that your were rubbing near the can.
• The can will roll towards the balloon!

What's going on?

Rubbing the balloon on your hair charges it up with static electricity which makes the balloon negatively charged. When you put the balloon near the can it pushes electrons (which are also negatively charged) to the other side of the can. This makes  the side which is nearest the balloon positively charged. Positive charges are attracted to negative charges so the can moves towards the balloon.

Number 4: The disappearing O.

Here I've got a really great and surprising example of how your brain makes stuff up.

What you'll need:
Nothing really, just this page. Or you could draw the X and O on a bit of blank paper.

          X                                                                    O                             

What to do:
1) Close your left eye.
2) Look at the X, but pay attention to the O.
3) Slowly move towards the screen.
4) When you are about 15cm or 6 inches from the screen (you'll need to be closer on a small screen) the O should disappear.

What's going on?
The retina at the back of your eyes is covering in cells that are sensitive to light. But at the spot where the optic nerve (which connects your eye to your brain) is attach to the retina there are none of these cells. Any light that falls on this blank patch isn't registered. Which means that when the light from the O hits that spot you don't see it.

So how come we don't notice this blind spot all the time? Well you're brain is pretty amazing, it just makes up some stuff based on what it sees around the blind spot and clones it in the space. There is white space around the O and thats what your brain sticks into the gap. You can see just what a good job your brain does by doing the same experiment on the X below.

Once again close your left eye and pay attention to the sentence 'Nothing missing is there?'. Nothing missing is there?

X                                                 Nothing missing is there?