Make your own snowflake

Just one more to add to the list. I have never seen snow in Thailand (although it feels cold enough for some these days) but you can make you own with this great flash based site. Happy cutting!

Levitation

You will need:

* A number of people (more than one for best effect)
* A narrow doorway

What to do:

Stand in the narrow doorway with your arms at your sides. Lift your arms up slightly so that you're touching the doorframe on either side with the backs of your hand


Now exert some effort! Press the back of each hand into the doorframe as hard as you can for 40 seconds.


Keep pushing…


Step away from the doorway and relax. What happens? Your arms will magically begin to levitate with no effort from you.


Get your group of friends to do the same thing and you can all stand around with your arms hanging in the air!

NB. The effect only lasts for a short time, so don't worry, you won't need to walk around like a penguin forever.

What's happening?

When you want a muscle to contract, your body sends an electrical signal along a nerve cell from the brain to the muscle. The signal starts a series of events that result in the contraction of that muscle.

The main event is the release of calcium ions into the muscle cells from the muscle's calcium store, or 'sarcoplasmic reticulum'. This increase in calcium makes the muscle contract.

When the nervous signal stops, the calcium ions go back into the sarcoplasmic reticulum and the muscle can relax.

To lift your arm from your side you use two muscles in your shoulder, the deltoid and supraspinatus muscles. By pressing your arm against the doorway you are sending a command to these muscles to move, but they can't because the doorframe's in the way.

As you carry on pushing against the doorway, you are still telling your muscles to move. A stream of electrical signals arrives at the nerve endings in these muscles. Masses of calcium ions are released into the muscle cells and they can't be completely cleared back into the sarcoplasmic reticulum.

When you move away from the wall, there is so much calcium in your muscles and they can finally contract in response! So even though the command from your nerves has stopped, your arm will lift itself away from your side!

Bored?

Ok, have you broken the new present Santa gave you already? You've watched all the new movies on UBC ages ago on DVD? Just waiting for the batteries on your PSP to recharge? Have a look at these two sites. You can create your own festive rap song (surprisingly addictive) or do a classic word search. Nothing to do with Science, but just something to kill the time and annoy your family with! Happy holidays.

How fast are you?

Think you're fast? Try this clever little trick to work out how fast your reaction time is – and there is no need for high precision clocks!

You will need:

A ruler, or metre stick if you have one
Some volunteers who are prepared to be tested…

What to do:

Hold the ruler at one end, so that the zero is at the bottom, hanging down between your volunteer's thumb and forefinger.
Tell your volunteer that you will drop the ruler some time within the next 5 seconds and their job is to close their thumb and forefinger to catch it as fast as they can after it starts dropping.
Drop it…and record where they managed to catch it. Keep testing them and anyone else wants to try!

What's going on:

Here's a very rough guide to the reaction times taken to grab the ruler at different distances down the ruler…

5 cm = 0.10 seconds
10 cm = 0.14 seconds
15 cm = 0.17 seconds
20 cm = 0.20 seconds
25 cm = 0.23 seconds
30 cm = 0.25 seconds
43 cm = 0.30 seconds
60 cm = 0.35 seconds
80 cm = 0.40 seconds

This experiment measures how long it takes for visual information to reach the brain, and for the brain to process the information, and send a command to your hand to say 'grab NOW!!!'

Whatever time you recorded, you must admit it's pretty speedy considering everything that has to happen inside the brain - plus the time it takes the 'grab now' message to travel from Brain Central out to the Fingers Operational Depot!

You can even take the experiment further; try comparing boys and girls, people of different ages, and you can even turn the lights down…

It's a Cracker!

You will need:

A packet of crackers - dry and fairly big!
A jug of water
Some volunteers
A watch with a second hand

What to do:

Challenge your volunteers to eat three crackers in under a minute, with no water, butter or other lubricant.
Give them a drink of water when the minute is up!
If you volunteers go separately they can try different techniques like shoving the crackers all in at once or breaking them into small pieces first.

What’s going on?

It is almost impossible to eat three crackers in under a minute because our bodies do not manufacture enough saliva to get the crackers to go down. Saliva is a very clever substance; not only does it provide enzymes to start breaking down food in your mouth it is absolutely essential for lubricating the mouth and throat to assist with swallowing. It also helps us taste, and keeps down infections in the mouth.

Our bodies manufacture between 1 and 2 litres of saliva each day, most of which ends up in our stomachs and is digested again. Unfortunately the crackers are very dry, great for storage, but not so great if you are trying to eat loads at once.

If you want to delve a little deeper you can get one of your volunteers to keep a cracker in their mouth for a while, while the enzyme amylase in their saliva gets to work and turns the starch in their cracker to sugar. It should start to taste sweet.

Warning - don't try this alone and do have a drink of water ready as it can cause choking if you aren't careful!

What happens when Science meets Culture?

Click on the image above to launch the page. When loaded drag the dot in the bar at the bottom left and right to answer the question above. The images link to current Science articles. If you are impressed by this then explore more projects by Jonathan Harris here.

MP3's too late for the Yr11 Trial Examinations

It has been some time since the last post. Perhaps time to push that horrible photo down out of view? I came across some excellent revision MP3's on the BBC bitesize website. The subjects include Physics, Chemistry, Biology and English. You can use the BBC website to download 'bitesize' chunks or use the Patana Science page and click on the podcasts icon on this page to download the whole lot in one go. Great for revising on the bus to school. By the way - does anybody listen to the podcasts I put there? Comments please.