# Dhanashree (13) asks “Why is sound a longitudinal wave?”

Dhanashree, thank you for the question. I asked my team about the question and they arrived at the following answer….which I was not happy with …….

There are two types of ways in which waves manage to travel ……. Longitudinal and Transverse. I can see the way the waves they develop BUT need time to think about how to explain them. Longitudinal waves travel along straight lines away from the source …  I am trying to understand how the particles associated with the travelling disturbance (sound) travel in each of these ways.

How do the particles of air (in longitudinal movement) make further particles of air move in the same way…if they are doing forward and back vibrations? The vibrating air particles (or particles of any gas) must be moving forwards as well as moving back and …thus moving the wave forward.

So …to answer your question …..sound is created by things vibrating, the drum skin vibrates, up and down when it is hit…….the air above the drum skin follows this vibration, and the air next to the vibrating air , starts to vibrate and so on. This is your longitudinal vibration.

With Transverse vibrations the particles move up and down. Like waves …which stay in the same place.  More thinking about this later.

# Amasidda (?) asked “Give one reason to prove that light is form of energy”

Then Amasidda you might be able to answer the question yourself.  Think about what all forms of energy – electric (electricity), light, heat (thermal), movement (kinetic), nuclear, chemical, sound, gravitational, can do. Can they all in some way do work? Can they all be converted from one from one form of energy to another?

What do you think ‘work’ is? Let me know in the comment box below.

# Unknown (age 7) asked – “Why is the sky blue?”

Hello unknown. I would not normally answer questions to an unknown questioner, but, as it it such an interesting question I asked my friends for some comments.

You are right. Where does the colour come from? It was in 1671 that the famous scientist, Newton, discovered that white light was a mixture of different coloured lights. He did this by passing white light (the light from the Sun) through a glass prism. Look at what he got……….

Later it was found that some of the blue light in the Sun’s light had difficulty passing through the Earth’s atmosphere. this blue light was scattered as it passed through the atmosphere therefore giving the sky a blue colour.

Some of the blue light still got through and appears as part of the white light in the prism experiment and also in the rainbow. In the rainbow the drops of rainwater act as small prisms.

Hope this makes sense. if you want to give your name please let me know in the comment box.

(amended 21/9/18 – raindrops as prisms added)

# “How does speed affect the energy of motion during a collision?” asked Damián Muñoz (9)

Sorry Damian it doesn’t really answer the question you asked. They have just presented you with more questions.
Let’s look at what they said.

Firstly energy is about work. The Energy or Work associated with a moving car is its movement. This type of energy is called Kinetic Energy. We could change the car’s Kinetic Energy by making the slope steeper (move the slope up a rung). It will make it go faster.

How do we measure the energy it is gaining as it moves faster and faster down the slope? Yes it does go faster while it is on the slope (we say that it is accelerating). Remember it starts with no energy at all (not moving). When it reaches the bottom of the slope it is going at its fastest speed.

We could measure the energy by seeing how long it takes to stop moving when it reaches the bottom of the slope. Try it. Make sure the test is fair. Fairness is very important in science investigations.

Alternatively you could involve it in a collision at the bottom of the slope…..say some cardboard or paper and see how far the car can push the shape it collides with. That would be another way to measure the ‘work’ that the moving car could do.

Damian, think about it. Experiment, and let me know how you got on.

Science Master

# Hamish Astra (11) asked “What are electrons and protons and neutrons made of?”

What a question. I suddenly feel very humble because that is a question that I should have asked myself but I never have. Thank you. I asked my friends to help me and here are the responses.

I have, discovered that electrons are still fundamental particles BUT they have found two types of electrons a negatively charged electron and a positively charged electron so they are now called leptons.  That does not however answer your question. What is a lepton made of?

My friends are quite correct Protons and Neutrons are no longer fundamental particles. (A fundamental particle is a particle that is not made of anything else) It was in 1911 that a scientist called Rutherford first discovered the proton and neutron. Then,in 1968, other scientists found that protons and neutrons were made up of fundamental particles called quarks. The next question of course is what are quarks made of?

To be continued

# “Questions about the Universe” by Lewis Jordan Sexton (13)

Lewis, thank you very much for your thoughts and the questions in your own mind that you are thinking about. Wow.

I’m tempted to tell you a story about a question that my wife asked to her mother when she was about your age. “Mother what is the Universe and what was the big bang?” Her mother’s reply was “They are very big questions, I think your time is better spent making sure that this planet we are living on lasts as long as possible, rather than worrying about the Universe”

For readers who are interested here is the what Lewis submitted. Lewis, if you would like me to remove it send a request in the comment box below.

My thinking is that we have no idea, at the moment, whether any of the the thoughts put forward by various scientists are valid. It seems to me to be a classic case of a set of developing scientific ideas as the tools and thoughts of the the scientists develop.

For example notable scientists like Newton and Einstein developed ideas relating to your thoughts  which were effectively disproved. This is in fact the way that all scientific arguments progress. For example ……When Albert Einstein was formulating his ground-breaking theory of gravity in the early 20th Century, at a time when astronomers only really knew of the existence of our own galaxy, he used the simplifying assumption that the universe has the same properties in all its parts, and that it looks roughly the same in every direction wherever, in the Universe, an observer happens to be located. Like Sir Isaac Newton two hundred years before him, he assumed an infinite, static or “steady state” Universe, with its stars suspended  motionless in a vast void.

One of the driving forces behind the development of science thinking is to disprove earlier scientific thinking. It is called falsification.

It was a philosopher,Karl Popper who said you can only have a scientific theory if it can be proved to be false. This is what has happened to the scientific theories of Einstein and Newton. Some of their ideas/theories on gravity and the nature of the Universe have been successfully disproved. New theories by Hubble (the telescope scientist) disproved the stable Universe idea’s of Newton and Einstein. This led to new scientific ideas of an expanding (rather than a stationary static state)  Universe …which could be false? To illustrate how scientist are challenging Hubble’s ideas it is now known that the Universe is expanding at an accelerating  rate than rather than a steady rate …….the mystery continues.

Have a look at this website The Physics of the Universe.

I shall continue thinking and possibly updating.

# If pressure on a gas is increased what will happen inter-particle force?” asks Prince (13)

You have to think of how you are going to increase the pressure of a gas.

I can think of two methods …..imagine the gas in a Coke tin. The gas particles are rapidly moving around, bouncing of each other and the sides of the container. We can increase the pressure by

(1) decreasing the volume of the coke can ….the particles therefore will hit the sides more often (increasing pressure) or (2) increasing the amount of gas in the can which again increases the number of gas particles that hit the side of the can, again increasing pressure.

In both these cases the intermolecular forces are quite small. Most gas particles are fairly inert , they have intermolecular forces but they are slight. Water H2O and NH3; (ammonia) are probably exceptional.

HOWEVER as you increase the pressure further the gas molecules have less room to move and they get closer to each other …the intermolecular forces increase UNTIL they are so strong (because there are so many molecules in the small space) that the gas becomes a LIQUID. This is helped if you reduce the temperature at the same time (molecular movement is temperature dependant).

Science Master

# Lachlan(12) asks “How does a trebuchet work?”

Lachlan – my first question is what is a trebuchet?

Simple answer …It’s a type of catapult.

Here is an image of  a very early trebuchet

Here is an image that may help your understanding and give you some clues on how the trebuchet works. When the mass 1 is released it begins to accelerate towards the ground. In doing so a force is applied to the beam pulling it down. That force is then applied, via the beam to the mass 2. What do you think will happen to Mass 2?

The support for the beam, the fulcrum, is in a particular position. Any thoughts on that? You could create a see-saw and investigate the application of forces when the fulcrum  changes position ……altering d1 and d2.

# “Is time travel possible ?” asks Lachie (9)

Thanks for the question Lachie . My friend is correct, Albert Einstein thought that time travel would be possible because of something he called relativity. It seems to be about the time it takes to move through a given distance (space) and the speed of light. The faster you go the slower the time that has past. That is a very, very difficult idea to understand. Even I find it difficult ….. but lets try and give you an example

Suppose you could move through space at or around or about 186,000 miles per second, which is the speed at which light travels?

Say you were 9 years old when you left Earth in a spacecraft traveling at about the speed of light (which is much faster than we can achieve now), and celebrated only five birthdays during your space voyage. When you get home at the age of 14, you would find that all your classmates were 59 years old, retired, and enjoying their grandchildren! Because time passed more slowly for you, you will have experienced only five years of life, while your classmates will have experienced a full 50 years.

So, if your journey began today in 2018, it would have taken you only 5 years to travel to the year 2068, whereas it would have taken all of your friends 50 years. In a sense, this means you have been time traveling.

According to Einstein’s ideas you can only move forward in time you cannot move backwards. However we do not at the present time have any vehicle that could reach the speed of light so if you want to travel in time you might have to wait a little while.
(revised 23rd May 2018)

# “How, where or when we’re magnets found or made?” asks Sam (11)

Thanks for the question Sam. Magnets and magnetism was first discovered about  9000 years ago. A long time ago. It was found in rocks and called ‘lodestone’. Lodestone is a naturally occurring compound of iron. It is thought that it was magnetised by lightning strikes.

We will make our own magnets by using a slightly weaker form of electricity.  Here are my team.

Firstly let us try to make a magnet (without using lightning)

You will need a battery and a length of wire and some paperclips. The a collection of nails. Try and find as many different nails as you can. Wrap the wire around the nail and sellotape the bare wire ends to the terminals of the battery. See the diagram below. See how many paperclips you can pick up? Are some nails better than others?

DO NOT USE MAINS ELECTRICITY. IT IS VERY DANGEROUS.

You might have found out that only certain metals can be made into magnets. These metals are called ferromagnetic metals.

Included in this group are the metal iron and the alloys of iron with the metals cobalt, nickel.

It is thought that in these metals (including iron) have some electrons called ‘free electrons’ (not sure what an electron is, then go to Science Master Special – Atoms and Atomic Structure). It is these ‘free electrons’ that are involved in magnetism. In the alloys the  ‘free’ electrons align themselves with the magnetism of the external magnet, making a (for the alloys) a permanent magnet.

Look at the short video I have made below. In the ferromagnetic metal (iron alloy) crystal domains you will see free electrons. In the metal these will be moving freely. As they begin to interact with the external magnetic field, they begin to align themselves, making a permanent magnet.