Cheating Physics

By Alice Orszulok

Scientists have come up with a trick to break Isaac Newton’s Third Law of Motion.

Over 300 years ago a man named Isaac Newton lived in England. When he was just a boy, while other children at school were playing catch or ball games, Isaac was busy creating sundials and model windmills powered by a mouse on a treadmill. When he grew up, he worked on developing calculus and physics. During his lifetime, he came up with three basic ideas that are applied to the physics of motion. These ideas are now called Newton’s Three Laws of Motion.

Newton’s Third Law states that for every action there is an equal and opposite reaction. Think about when you sit in a chair. Your body exerts a force downward and that chair needs to exert an equal force upward or the chair will collapse. Ever since the 17th century this law has been widely upheld, however a group of German scientists have come up with a trick that lets light accelerate (move very quickly forward) all by itself without any opposing force.

This is not something you’d be able to do at home. It involves working with particles called photons, which are believed to have no mass at all and require a state of negative mass—a state that scientists aren’t even sure exists. What the scientists did was create an optical diametric drive. This drive is basically an anti-gravity system, which requires an object with positive mass to collide with an object with negative mass, causing both to accelerate forever in the same direction. If this were to work, scientists could build a spaceship so fast that we could potentially reach the stars. NASA tried to build a diametric drive in the 1990s for this reason, but failed because as far as we know there’s no such thing as an object with negative mass.

Scientists have gotten around this technicality by using photons to create something called effective mass. When manipulated just right, light can have negative effective mass, which is what the team’s optical diametric drive is designed to do. The device takes pulses of light and splits them between two connected fibre-optic loops, one bigger than the other. As the pulses travel through the different sized loops at slightly different times, they share photons that give them effective mass, some positive and some negative. These pulses then accelerate in the same direction, ultimately breaking Newton’s Third Law of Motion.

This concept is extremely complicated, so it’s ok if you don’t understand it straight away. What’s exciting is that the idea of laser pulses that accelerate continuously in the same direction could make computers and other communications devices, such as mobile phones, become faster and more powerful. However, we’re still in the experimental stage of the new technology, so new super phones or spaceships that can surpass the speed of light are still a long way off.

Source [New Scientist]

Keyword [Mass]

Mass is the measurement of how much matter is in an object. It is commonly measured by how much something ways, such as kilograms, however your weight can change depending on where you are. For instance, you weigh less on the moon than you do on Earth, but you mass remains the same.