A recent survey of scientific literacy in Australia found 30% believe it takes one day for the Earth to go around the sun. This video provides qualitative evidence for the finding from Sydney's Eastern beaches.

How long does it take for the earth to go around the sun?

There are a few persistent misconceptions about what causes the seasons. Most believe it is the distance between the Earth and sun which varies to give us seasonal temperature variations. However it is actually the directness of the sun's rays leading to more intense sunshine in summer and less in winter.

What causes the seasons?

This is the first Veritasium science video. It addresses one of the most fundamental concepts in science: the idea that all things are made of atoms, tiny particles that are in perpetual motion. They attract each other when a little distance apart and repel when squeezed together.

Atomic Theory

JJ Thomson proposed the first model of the atom with subatomic structure. He had performed a series of experiments and was credited with the discovery of the first sub-atomic particle, the electron. He therefore proposed a new model of the atom called the plum pudding model. In this model, the plums represent negatively charged electrons which can be plucked out of the atom, leaving behind some positively charged pudding. In this film, cherry tart is used as a delicious substitute for plum pudding.

Thomson's Plum Pudding Model of the Atom

In the mid 1800's scientists successfully passed an electric current through a vacuum in a glass tube. They saw a glow from the tube that seemed to emanate from the negatively charged plate called the cathode. Since scientists didn't know what the glow was they called it a cathode ray. There was debate over whether the cathode ray was a wave phenomenon like light or a stream of negatively charged particles. JJ Thomson effectively resolved the debate in 1897 by performing a clever experiment that determined the charge to mass ratio of the particles making up the cathode ray. He also showed that this same particle was in all different cathode materials so it must be a constituent common to all atoms. This changed our understanding of the atom from the previous billiard ball model to Thomson's plum pudding model of the atom.

Cathode Rays Lead to Thomson's Model of the Atom

Scientists have to work with some very large and some very small numbers. To represent these numbers more easily, they use scientific notation. Scientific notation relies on powers of 10.

This video gives examples of how to represent a large and small number and explains powers of ten.

Scientific Notation - Explained!

🎶Well an atom's made of protons, neutrons, and electrons... 🎶

I'm Atoms (Scientific Cover of Jason Mraz's I'm Yours)

If the sun were entirely made of protons, how many would there be in the sun? How can this be worked out using the Google search field?

Scientific Notation - Example

There is a common perception that weight and mass are basically the same things. This video aims to tease out the difference between mass and weight by asking people what makes a car difficult to push. The standard answer is that it is difficult to push because it's heavy. But heaviness is a measure of weight, the gravitational pull of the Earth attracting the car to Earth's center. When the car is pushed on a flat road, the force of gravity does not oppose the motion. Instead, the resistance felt is an indication of the car's mass which determines its inertia. Inertia is the property of matter which means it tends to resist acceleration - the greater the mass, the less the acceleration for a given amount of force.

The Difference Between Mass and Weight

If you spin a raw egg and then stop it, it will start spinning again without you having to touch it. A boiled egg, on the other hand, stops and stays stopped. Why is this? Well, a raw egg contains a yolk that moves inside the egg independently of the shell. If you stop the shell, the yolk inside continues to move due to its inertia and it, therefore, gets the egg spinning again.

Egg Experiment to Demonstrate Inertia

A song about Gravity set to the tune of John Mayer's Gravity.

Gravity (Scientific Version of John Mayer's Gravity)

If the Earth were the size of a basketball and the moon a tennis ball, how far apart would they be? Diagrams that are not to scale make us think that they're closer than they really are.

How Far Away is the Moon? (The Scale of the Universe)

Force is a central concept in physics. By analysing the forces on an object, its resulting motion can be determined. But what exactly is a force? The word force is used in everyday language in a variety of contexts, only some of which reflect the scientific definition of force. In this video, people at Victoria Park in Sydney are interviewed on their ideas of force and the forces that act on them.

What is a Force?

What forces (i.e. pushes or pulls) are acting on you right now? Most people can identify the gravitational force down, but there must be something else otherwise you would accelerate down towards the center of the Earth. The other main force on you is called the normal force. It is a force perpendicular to the surface that supports you, like the ground or the seat of your chair. You compress this surface and it acts like a spring, pushing you up.

What Forces Are Acting On You?

It takes the moon about 27 days to orbit the Earth. What makes it go round? It is the gravitational attraction of the Earth on the moon. Due to the moon's velocity, the Earth keeps pulling the moon towards it without the moon actually getting closer to the Earth. This is similar to how satellites orbit the Earth.

Why Does the Moon Orbit Earth?

People have a lot of different ideas about what gravity is: a downward force that stops you from flying off into space, an attraction smaller objects experience towards larger objects or a mutual attraction between all masses. It is the last of these ideas that best reflect a scientific conception of gravity.

What Is Gravity?

There is a gravitational force of attraction between the Earth and the moon, but is it mutual? That is, are the forces on the Earth and the moon equal? Most people would say no, the Earth exerts a greater force of attraction because it is larger and has more mass. This is a situation in which Newton's Third Law is relevant. Newton's Third Law says that for every force, there is an equal and opposite reaction force. So the force the Earth exerts on the moon must be exactly equal and opposite to the force the moon exerts on the Earth. But how can that be - that the same size force keeps the moon orbiting, but barely affects the Earth? The answer is inertia - the tendency for all objects with mass to maintain their state of motion. Since the Earth has much more mass than the moon, it has greater inertia and therefore experiences much less acceleration for the same amount of force.

Best Film on Newton's Third Law. Ever.

Newton's Law of Universal Gravitation can be summarized as "all mass attracts all other mass." But if this is true, why don't we notice the gravitational force of attraction between everyday objects? The reason is that the gravitational force is quite weak.

Calculating Gravitational Attraction

A basketball and a 5kg medicine ball are dropped simultaneously. Which one hits the ground first? It seems obvious that the heavy one should accelerate at a greater rate and therefore land first because the force pulling it down is greater. But this is forgetting inertia - the tendency of mass to resist changes in motion. Therefore, although the force on the medicine ball is greater, it takes this larger force to accelerate the ball at the same rate as the basketball.

Which Hits The Ground First?

If you drop a heavy object and a light object simultaneously, which one will reach the ground first? A lot of people will say the heavy object, but what about those who know both will land at the same time? What do they think? Some believe both objects have the same gravitational pull on them and/or both fall to the ground with the same constant speed. Neither of these things is true, however. The force is greater on the heavy object and both objects accelerate at the same rate as they approach the earth, i.e. they both speed up but at the same rate.

Misconceptions About Falling Objects

If you've seen footage from the International Space Station or any of the space shuttle missions, you know that astronauts float around as they orbit the Earth. Why is that? Is it because the gravitational force on them is zero in space? (Or nearly zero?) The truth is that the strength of the gravitational attraction is only slightly less than it is on Earth's surface. So how are they able to float? Well, they aren't floating - they're falling, along with the space station. They don't crash into the Earth because they have a huge orbital velocity. So as they accelerate towards the Earth, the Earth curves away beneath them and they never get any closer. Since the astronauts have the same acceleration as the space station, they feel weightless. It's like being in a free-falling elevator (without the disastrous landing).

Is There Gravity In Space?

Newton's Three Laws of Motion are a landmark achievement in physics. They describe how all objects move. Unfortunately, most people do not really understand Newton's Laws because they have pre-existing ideas about the way the world works. This film is about those pre-existing ideas. By recognizing what people are thinking, it becomes easier to describe the correct scientific concepts of Newton's Three Laws and how they differ from this 'intuitive physics'.

Three Incorrect Laws of Motion

A short a cappella tribute to experimentalists. It is sung while performing three simple experiments with household items: Mentos dropped in diet Coke, a tea bag emptied and burned, and a ping pong ball floating in the air stream of a hair dryer.

Experiments A Cappella

It is a common view that "if only someone could break this down and explain it clearly enough, more students would understand." Khan Academy is a great example of this approach with its clear, concise videos on science. However, it is debatable whether they really work.

Khan Academy and the Effectiveness of Science Videos

Most people recognize that atoms are the fundamental building blocks of all matter around us. An atom itself is composed of protons, neutrons, and electrons. The simplest atom is the hydrogen atom because it consists of only one proton and one electron. If a neutron is added to the nucleus, the atom is still hydrogen, just a more massive version. Atoms of the same element (i.e. those with the same number of protons) but different numbers of neutrons are called isotopes.

What Are Atoms and Isotopes?

Many videos on YouTube show water freezing almost instantaneously. This video shows you how to replicate the experiment and it explains how the phenomenon works.

Supercooled Water - Explained!

What is radiation? Are all types harmful? What are the most common sources of damaging radiation? Most people view radiation as harmful and negative without understanding what makes it potentially damaging and which forms should be avoided. For example, many felt radiation from mobile phones probably caused cancer but few focused on the carcinogenic effects of UV rays.

How Damaging is Radiation?

A planet has been predicted to orbit the sun with a period of 10,000 years, a mass 5x that of Earth on a highly elliptical and inclined orbit. What evidence supports the existence of such a strange object at the edge of our solar system?

Does Planet 9 Exist?

The misconception is that electrons carry potential energy around a complete conducting loop, transferring their energy to the load.

The big Misconception about Electricity

Digital computers have served us well for decades, but the rise of artificial intelligence demands a totally new kind of computer: analog.

Future Computers Will Be Radically Different (Analog Computing)

To make antivenom, you first need to collect venom from the world’s most deadly snakes.

Huge thanks to the Australian Reptile Park for having us over to film – special thanks to Zac Bower for milking all of these snakes for us and Caitlin Vine for organizing the shoot.

How Horses Save Humans From Snakebites

One scientist caused two environmental disasters and the deaths of millions. A part of this video is sponsored by Wren.

The Man Who Accidentally Killed The Most People In History

How Electricity Actually Works

This is an image of the supermassive black hole, Sagittarius A*, at the center of our Milky Way galaxy.

How did they actually take this picture? (Very Long Baseline Interferometry)

Astronomers think there should be 5 times as much dark matter as ordinary matter – a shadow universe that makes up most of the mass in the universe. But after decades of trying, no experiments have found any trace of dark matter – except one.

This video is sponsored by Brilliant.

The Absurd Search For Dark Matter

The 100 Prisoners Riddle feels completely impossible even once you know the answer. This video is sponsored by Brilliant.

The Riddle That Seems Impossible Even If You Know The Answer

Fritz Haber is the scientist who arguably most transformed the world. Part of this video is sponsored by Wren.

The Man Who Killed Millions and Saved Billions

Which experts have real expertise? This video is sponsored by Brilliant.

The 4 things it takes to be an expert

This tiny robot can jump higher than anything else in the world. This video is sponsored by Brilliant

World's Highest Jumping Robot

Adhesives based on gecko skin can hold huge weights – without sticking to anything.

The Stickiest Non-Sticky Substance

Welcome to Micromouse, the fastest maze-solving competition on Earth.

The fastest Maze-Solving Competition on Earth

People don’t understand the scale of the Universe.

Do People understand the Scale of the Universe?

How a rainfall simulator saves millions of lives.

The rainiest Place on Earth

The blue LED was supposed to be impossible—until a young engineer proposed a moonshot idea.

Why it was almost impossible to make the Blue LED

How do QR codes work? The checkerboard patterns taking over the world, demystified.

I used to hate QR codes. But they're actually genius

An element of truth | Science and engineering videos

Veritasium is a channel of science and engineering videos featuring experiments, expert interviews, cool demos, and discussions with the public about everything science.

All Episodes of Veritasium

Browse all episodes of Veritasium

Season 1

How long does it take for the earth to go around the sun?

Season 1 Episode 1 - Aired 8/15/2010

What causes the seasons?

Season 1 Episode 2 - Aired 8/16/2010