Happy Valentine’s Day! Love can confuse your brain, and so does this week’s Try This Tuesday.
You don’t need any equipment to try this experiment at home – you just need to stare at your screen, or more specifically the + in the middle of the picture below. You can blink but don’t look away.
If you stare long enough the pink dots should disappear!
It looks like the pink dots have disappeared due to a visual phenomenon called Troxler’s fading or Troxler’s effect. if you fix your eyes on a certain point, then anything in your peripheral vision will fade away and disappear after about 20 seconds. In this experiment our sight was focused on the + in the middle of the screen and the the pink dots in your periphery slowly fade and finally disappear. It works especially well in this experiment at there is such low contrast between the light pink dots and the grey background.
This is a type of optical illusion. If you want to see another, have a look at our spinning disk Try This Tuesday.
This week we will show you how to play a game that you will never lose! For this you will need 12 pegs and a piece of material. Clip all 12 of these pegs in a line along the material.
The rules of the game are simple:
There may only be 2 players.
Each player takes it in turns to remove 1, 2 or 3 pegs from the material.
The winner is person who removes the last peg.
If you follow 2 key steps then you can ensure victory every time. Firstly always let your opponent go first. The second step is to remove enough pegs so that the combined total of the pegs you remove and the pegs your opponent removed on their last turn adds up to 4.
For example if your opponent removes 1 peg then you will remove 3 but if your opponent removes 3 pegs then you should only remove 1 peg.
If you do this then no matter what happens the most pegs you will ever have on your last go will be 3 so you will always win!
This game is actually based on good old times tables and more specifically the 4 times table. If each round adds up to 4 then the 12th peg will always be removed by the person finishing the round as 12 is a multiple of 4.
This means the game could be played with even more pegs as long as the total number of pegs is a multiple of 4.
This Tuesday, you don’t need any equipment to try this experiment at home – you just need to stare at your screen, or more specifically the video clip below:
(don’t worry we aren’t trying to hypnotise you!)
Stare in the dot in the middle of the circle for 20 seconds, you can blink but don’t look away, keep your eyes focused there. After 20 seconds look at someone’s face, if there’s no one around you, get a face up on screen that you can quickly look at.
What did you see?
Hopefully, if it worked you should have seen the face appearing to get bigger. Obviously, it didn’t really grow before your eyes, this is simply an optical illusion playing a trick on your brain.
You see things because your eyes send messages to your brain about different types of light, shapes and movement and your brain makes up an image of the world around you. When you stare at the spinning disk for so long, your eyes continually send messages to you brain to say its spinning. Your brain gets a bit bored of hearing the same message over and over again so kind of stops listening, tunes out the messages and just assumes from now on, this is how it is – everything is spinning.
So when you look away at a face or your hands or anything really, your brain thinks it should be spinning so gets confused and spins the image in the opposite direction, making it appear to grow. After a few seconds, your brain will hopefully catch up and everything will go back to normal.
Here’s a little trick you can play on your friends, or someone you don’t know well enough to already know their birthday…
With the five cards below, you can “guess” anyone’s birthday. Just go through each of the cards in turn and ask them if their birthday (as in the date they were born, not the month, so if they were born on the 17th January, their number is 17) is on the card. Discount the cards their birthday is not on.
With the remaining cards, the cards their birthday is on, add up the numbers in the top left corner and the number you get should be their birthday!
For example, my birthday is the 30th April so 30 in my number. Its on card 1,2,3,4 and not card 0 so you would add up 2+4+8+16=30.
Is it science or is it magic?
Of course it’s science! This actually works on a system called binary, which is the language computers use. Binary is written in 0s and 1s and these together look just like 101001010010010101010 to us but to a computer that might actually mean something.
In this case, when you discount a card, that becomes a 0 and the remaining cards are a 1. So going back to the example of my birthday the cards would read 11110 (reading it backwards) and in binary this means 30.
You’ve probably got exams coming up, maybe you’re supposed to be revising now, chances are you’re surrounded by textbooks. If so here is a quick little experiment you can try.
All you need is two large books with lots of pages, around 200 or so.
Start by interleaving the pages one on top of the other to sandwich the books together, like so:
This doesn’t require any kind of glue or tape but the two books should now be securely stuck together. Challenge your friends to try to pull the books apart – no matter how strong they are, they won’t be able to do it!
So if there’s no glue, why is this? It’s all because of friction. Friction is a force that occurs when one object moves over another – it is the resistance that is felt. When you try to pull the books apart there is friction acting on each page opposing the movement. If you consider there are over 200 pages, this force is multiplied and so becomes super strong!
When you pull the books the pulling motion squishes the pages in the middle with a greater force, this in turn makes the force of friction greater as it acts to oppose this force. So the harder you pull, the more difficult it is to separate the books!
You will need: large tall glass, bicarbonate of soda (baking soda), vinegar, a candle and some matches
1. Add 4 teaspoons of bicarbonate of soda to the glass
2. Pour in roughly 150ml of vinegar, the mixture will fizz.
3. Light the candle.
4. Once the mixture has stopped fizzing, pick up the glass. Without pouring out the vinegar, gently tip the glass from a few centimeters above the candle. Imagine that there is an invisible liquid inside above the mixture. The candle will go out!
You have produced a gas, carbon dioxide, by mixing the bicarbonate of soda with vinegar (also known as acetic acid). Bicarbonate of soda contains carbon dioxide, but it is attached to other molecules. When you mix it with vinegar the bicarbonate breaks down and releases carbon dioxide as a gas.
The following reaction takes place:
bicarbonate of soda + vinegar → sodium acetate + water + carbon dioxide
NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2
Carbon dioxide is heavier than air so stays in the glass until you tip it over the candle. When you pour carbon dioxide on a candle it stops the flow of oxygen which is needed for a flame to burn, and the candle is extinguished.
Real fire extinguishers also use carbon dioxide to put out fires, it is compressed (squashed) into cylinders and sprayed at fires.
We’re feeling very festive this Tuesday so we thought it was the perfect time to make snow with science. All you need for this one is some shaving foam and bicarbonate of soda.
Simply mix the bicarbonate of soda and shaving foam together in a bowl until you get a powdery consistency.
Pick it up and have a play – you might notice that your fake snow actually feels cold too. This is due to the reaction between the bicarbonate of soda and the shaving foam. The reaction is endothermic meaning that it requires heat to occur, it takes this from the environment and so decreases the temperature around it.
The Science of Shaving Foam
Do you think shaving foam is a liquid or a solid? It’s actually a colloid. A colloid is a substance which has droplets of one state surrounded by another state. There are lots of different types of colloids with different combinations of states making up the droplets and the surrounding. In the case of shaving foam, the droplets are gas and the surrounding is liquid making it a foam colloid.
Today we will be experimenting to see what happens when you put a lighter or a flame underneath a balloon filled with two different states of matter: air and water.
You will need two balloons, some water and a lighter
Blow up one of the balloons with air and tie it up.
Fill the other balloon with a little bit of water, blow it up the rest of the way and tie it up.
Hold the lighter under the balloon with the air in it and see what happens. Be careful as it should pop!
Light the lighter under the balloon with some water in it, be careful to hold the lighter under the part of the balloon where the water is. The balloon won’t pop!
This happens because water can absorb heat a lot easier than air and is a better conductor of heat. Water keeps the heat away from the balloon. This is called its ‘heat capacity’ and is why water is often used to cool things down in places such as power plants. The air is not very good at absorbing the heat, so the balloon heats up and pops!
Glass is transparent (see through) but we can still see it. In this experiment we will show you how to make it vanish!
1. Fill a large glass bowl or container with cooking oil.
2. Put a smaller glass bowl inside the large one.
3. Look from the side, can you see it?
This happens due to the refraction of light and how the speed of light changes when it passes from one state of matter to the other.
Light travels through different objects at different speeds. It travels faster in air than in water or glass. We can see glass normally as light passes from air to glass and slows down and changes direction. This distorts (changes) how we see other objects through the glass, telling the brain there must be a transparent object in the way.
The bowl disappears when we put it in cooking oil, as light travels at the same speed in cooking oil and glass. The light doesn’t change direction so your brain doesn’t know that the light has traveled through the glass, making it disappear!
This week’s experiment will show you how a submarine works using just a water bottle and a ketchup sachet.
Take a large (2 litre) plastic bottle and fill it with water
Test a few ketchup sachets in a bowl of water to see if they float, not all of them will have an air pocket in.
Add an unopened sachet of ketchup to the bottle. The sachet should float, but if it doesn’t, try adding some salt to the water. Salt increases the density of water, making the sachet float better.
Make sure the bottle is full of water to the top.
Screw on the top very tightly and squeeze the bottle hard.
The sauce submarine will sink to the bottom. If you let go it will float back up.
You can challenge other people to get the sachet to the bottom, lots of people will try and shake it or turn it upside down!
This experiment is all to do with how things float, or the buoyancy of an object. Water pushes up on the ketchup packet with the force equal to the weight of the water that the ketchup packet pushes out the way. If the displaced water is heavier than the sachet, then it will float because it is less dense than the water.
When you squeeze the bottle you apply pressure to the liquid inside. Liquids cant be compressed (squashed) so the pressure is transmitted to the sachet. The ketchup sachet has some nitrogen gas in (to keep it fresh). The gas is compressed and the sachet sinks and therefore displaces less water and sinks. As soon as you let go the sachet expands again and floats.
Submarines use similar systems to allow them to sink and float easily.