Quantum Mechanics For Kids! Trivia Quiz

Answer: The tiniest particles (bits) that everything is made of

Atoms are the building blocks that everything is made of - a bit like the lego bricks of nature. Atoms are tiny. Think how many grains of sand there must be on one beach. There may be that many atoms in one single grain of sand!

But just as lego bricks are made of something (plastic), atoms are also made of something. Atoms are made of particles (tiny bits). You might have heard of protons, neutrons and electrons. Quantum mechanics studies how these "bits of atoms" or "sub-atomic particles" behave.

Answer: The smallest amount of something

A quantum is a specific amount of energy. A quantum is such a small amount that it cannot be divided to make a smaller amount. It is sometimes thought of as a "packet" of energy.

Answer: How things interact

In scientific terms, mechanics is the study of how different things interact with each other, and the forces involved in their interactions. Quantum mechanics is the study of how the tiniest particles interact with each other, and the tiny packets of energy involved in their interactions.

Answer: No, they will go in the direction they intended to go

Watching the cars doesn't change their behaviour. But when scientists try to "watch" particles, it makes the particles do something different. This is because they are so small that the instruments scientists use to look at the particles interferes with what the particles are doing.

It is a bit like if you are a very bad birdwatcher - if you cause too much disturbance the birds won't behave naturally, and they will fly away. This is called "observability" or the "observer effect" and means that it is very difficult for scientists to find out about these tiny particles.

Answer: Light can behave like a particle and like a wave at the same time

Amazingly, light sometimes behaves like a particle and sometimes like a wave! In the early 20th century, scientists disagreed about which it was and did not believe that it could be both at the same time. They did experiments to try and discover which theory was right, and found out that in some experiments light acted like waves (one continuous piece) and in other experiments it acted like particles (individual pieces).

This is called "wave-particle duality." Later on, scientists discovered that everything actually behaves like a wave and a particle. So even you have a wavy side!

Answer: When light hits a metal, the metal releases electricity

When the light hits the metal, it knocks electrons out of the metal. If light was a wave, then we would expect the speed of the electrons being knocked out to depend on the intensity (or brightness) of the light. Think about a wave in the sea hitting a beach ball - the stronger the wave, the faster the ball will fly forwards.

The famous scientist Albert Einstein did some experiments to investigate this effect. What Einstein found was that the brightness of the light didn't change the speed the electrons were knocked out. Instead, he noticed that the number of electrons being knocked out changed, depending on how bright the light was. The brighter the light, the more electrons got knocked out.

Einstein used this discovery to show that light comes in little particles, which scientist call photons. The photoelectric effect could be summed up by saying that for each photon that hits the metal, one electron gets knocked out. Because the electrons were all knocked out at the same speed, Einstein said that each photon was like a packet, each containing the same amount of energy - a quantum of energy.

This discovery earned Einstein the Nobel Prize in 1921.

Answer: Yes! Spooky!

If you answered "No way!", you are in good company - this was exactly what Einstein thought as well! If coins worked like that, we could both toss a coin right now and I would be able to tell you how yours had landed by looking at mine. But spookily, two subatomic particles which are miles away from each other can become linked in such a way that the actions of one can affect the other.

This is called "entanglement".

Answer: If we know where a particle is, we can't know how fast it is moving, and vice versa

In the "normal" world we can measure how fast a car is going and exactly where it is. That's how people get caught breaking the speed limit! However, in the crazy quantum world it's not so easy to pin things down. There are pairs of measurements such that we can only know one or the other of them. For example if we know where a particle is we can't know how fast it is moving, or what direction it is going in. This is what "uncertainty" is about, and it was summed up by a scientist called Werner Heisenberg.

The best scientists can do is to say how likely it is a particle will be doing a certain thing. For example they cannot say whether a particle will be in place A or place B, but they have a function called a "wave function" that says there is a 50% chance it will be at A and a 5% chance it will be at B - so it is more likely to be at A.

Answer: 100% because the scientist has seen it and knows it is there

This causes a bit of a contradiction or paradox. The wave function that describes the position of the particle tells us that there is a 50% probability of the particle being at place A, but we have spoilt it by changing the probablility to 100%! This is called the "collapse of the wave function" or the "measurement paradox".

Answer: No, it is either dead or alive

In the "normal" world, a lot of things are either one thing or another. Dead or alive. On or off. In the "quantum world" particles can be more than one thing at the same time. This is called "superposition of states". "Superposition" means one thing on top of another.

There is a famous thought experiment called "Schrödinger's cat" where a scientist called Erwin Schrödinger made up an argument which went a bit like this:
(1) Put a cat in a box so we can't see it or hear it
(2) Put some poison in the box that can be released by a quantum particle being in position A
(3) If the quantum particle is in position A, the poison is released and the cat is dead
(4) If the quantum particle is in position B, the poison is not released and the cat is alive
(5) Because the particle can be in both position A and position B at the same time, the cat can be both dead and alive at the same time.

This is a very puzzling idea even for very clever scientists!