# #TryThisTuesday: Invisibility Cloak

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?

### The Science

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!

# #TryThisTuesday: Submarine

This week’s experiment will show you how a submarine works using just a water bottle and a ketchup sachet.

1. Take a large (2 litre) plastic bottle and fill it with water
2. 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.
3. 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.
4. Make sure the bottle is full of water to the top.
5. 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!

### The Science

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.

# Celebrating Marie Curie

Marie Curie was born 149 years ago today. We think she is one of the most inspiring female scientists as one of the first women to make an outstanding contribution to science. Her work overturned established ideas in physics and chemistry and helped overcome societal barriers for women.

Marie Sklodowska was born in Poland in 1867. In 1891 she went on to study physics and maths at Sorbonne University in Paris. She met Pierre Curie, professor of the School of Physics, who she married in 1895, becoming Marie Curie.

The Curies worked together investigating radioactivity, the process where atoms decay by emitting radiation. With help from other physicists they discovered new elements, polonium (named after her home country, Poland) and radium in 1898. This work was extremely difficult as they were constantly exposed to radioactive elements, which made them feel ill, an effect known as radiation sickness. They received the Nobel Peace Prize in Physics for their work in 1903. Marie Curie was the first woman to win a Nobel Prize.

Unfortunately, Pierre died from being knocked down by a carriage in 1906. Marie Curie took over his professor post and became the first woman to teach at Sorbonne University. She received a second Nobel Peace Prize in 1911 for her work in chemistry where she determined a way to measure radioactivity.

Her research was crucial in development of X-rays. Marie developed small mobile X-rays that were used in World War One to diagnose injuries. She worked with her daughter at the front line to help diagnose injuries.

Marie Curie died due to exposure to radioactivity during her work in 1934. The Marie Curie Hospital was opened in 1930, specialising in radiological treatment of women suffering from cancer. The Marie Curie charity was established in 1948 which now offers care, support and guidance for people with a terminal illness.

# World Egg Day: Eggsellent Experiments

Happy world egg day! Here are some cracking eggsperiment that you can at home on this very important day:

### Egg in a Bottle

For this experiment you will need a hard boiled egg, an empty plastic bottle, a scrap of paper and a lighter.

Light the paper and drop it into the bottle. After a second place the egg on top of the bottle and observe the results.

The lit paper heats up the air in the bottle, causing it to expand slightly and for some air to escape. The egg creates a seal so more air cannot enter. As the air cools inside the bottle it decreases the pressure and forces the egg into the bottle.

### Floating Egg

All you need to try this one is an egg, a glass, water and salt.

Fill you glass half full with tap water and carefully place the egg inside. It should sink. Add some salt until the egg floats. The salt increases the density of the water, when you add enough the egg becomes less dense than the water so floats to the top.

Next dribble spoonfuls of tap water down the side of the glass until it is full. The egg should appear to float in the middle of the glass, it is actually floating on top of the salt water with a layer of fresh water above it.

### Hard boiled Spin

Lay a hard boiled egg flat on its side and spin it. Put your finger on it to stop and then let go, nothing remarkably happens there. Try the same with a raw egg and when you let go it will start spinning again on its own accord.

This is all due to momentum. When you spin the eggs you spin their insides too. In the hard boiled egg, the insides are fixed to the shell so it behaves as you would expect. In the raw egg the insides continue to spin after you’ve stopped the shell. When you let go, the momentum of the spinning yolk carries the shell and the whole egg starts spinning again.

# 9 Scientific Mistakes in Disney and Pixar

Sorry to crush your dreams but we have inspected some of our favourite Disney films and some things just don’t sit right in our scientific minds. Here are nine examples of what would really happen, according to science. But remember anything is possible in the world of Disney…

### 1. Finding Nemo

All clown fish are born male. Each group of clown fish has one female, the biggest fish. When the female dies, the biggest male fish will become female, this is know as being a sequential hermaphrodite.  When Nemo’s mother was killed by the barracuda, Marlin would have become female, leaving Nemo as the dominant male.

### 2. The Lion King

Rafiki is introduced to us in the Lion King, where he performs Simba’s birth ceremony. He also sings a song in the film “Asante sana, squash banana, wewe nugu, mimi hapana”. This is a Swahili rhyme which translates to “Thank you very much (squash banana), you’re a baboon and I’m not!”. Rafiki doesn’t belong to any species, he is a cross between a mandrill and a baboon, he has the colourful nose and cheeks of a mandrill and the mane and long tail of a baboon.

### 3. Up

In the film Up, Carl ties thousands of balloons to his house to go on an adventure to South America. However, the number of balloons he uses are not enough to lift a house. Estimating that the house weighs 45,000 kg, you would need over 3 million balloons!

### 4. Inside Out

Inside Out personifies five major emotions; Joy, Sadness, Fear, Anger and Disgust which all work together to guide and protect their human (Riley). However, there are actually six core emotions, with Disney missing out surprise. These six emotions are found to be universally recognized and expressed across the world, even in remote tribes that would not have learned the meaning of such facial expressions elsewhere.

### 5. Tarzan

After baby Tarzan was left alone in the jungle to be raised by gorillas, he eventually grows up and meets Jane who teaches him to speak English. Unfortunately in the real world, no matter how great a teacher Jane was, Tarzan would never have been able to talk. Scientists have described a critical period up to the age of 5 which is vital for language development. If children, like Tarzan, aren’t exposed to a human language in this time they will be unable to learn to speak later in life.

Aladdin and Jasmine travel from Cairo (Egypt) to Athens (Greece) in one second on the magic carpet, meaning they would have to travel at 621 miles per second! The air resistance would be 100 million times larger than their weight, causing them to burn up, like when meteors burn up when they enter our atmosphere.

### 7. Star Wars

Star Wars is well know for its fights in space, full of explosions, blaster and engine sounds. However, space is a vacuum, meaning that it is devoid of matter, there are no gases or air there. Sound can’t travel in a vacuum, as sound vibrations don’t work, therefore we shouldn’t be able to hear any sound.

### 8. The Good Dinosaur

In the good dinosaur, a young dinosaur by the name of Arlo befriends a human boy. Arlo is an Apatosaurus which lived around 151 million years ago. Human beings as we are or Homo sapiens only evolved between 200,000 to 100,000 years ago so in reality Arlo and his friend would have missed each other by quite a few million years.

### 9. Finding Dory

When searching for Dory’s family in Finding Dory, we discover that Dory was born in captivity, in an aquarium. However, Dory is a species of fish known as the Blue Tang. This species can’t be bred in captivity and have to be caught from their wild home of coral reefs in the Indo-Pacific Sea.