Albert Einstein’s relativity theory 101


Everyone knows the name Einstein – whether you know it from your science lessons, your own reading, word of mouth, or that epic picture with his tongue sticking out (forever legendary), we all know that Einstein provided the world with some of the most revolutionary scientific theories that changed the world in which we know it. Because of his work on Gravity, through his Theory of Relativity, Albert Einstein was even awarded the Nobel Prize in Physics in 1921. But if you haven’t got enough time to read his whole paper, this is it in a nutshell.

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The concepts

Albert Einstein first started working on his Theory of Relativity from 1907 until 1915. Although Einstein finally cracked it, his work involved the interworking of many different theories previous to his. He used his own Theory of Special Relativity, Lorentz Transformation Equations, Fundamental Laws and Principles of Relativity and his own Theory of General Relativity as well as the historic work from Isaac Newton and Galileo.

The beginning

Until Einstein’s discovery, the world worked under the ideas of Isaac Newton and his Laws of Motion. His first Law of Motion is that an object will remain stationary unless acted on by another force – i.e., you will only move on the swing if someone pushes you or you push yourself against the ground. But Albert Einstein questioned this motion. He noted that if he fell off a roof, or was free-falling towards the ground, he did not feel any force pushing against him and that he felt weightless. It felt as if he was accelerating; getting faster the closer he got to the ground.

The confusion

Einstein felt confused with this notion. On the one hand, Isaac Newton’s Law of Motion would state that something without force would travel at a constant speed – however, he would be traveling at an accelerated speed with no force against him. This anomaly in Newton’s theory prompted him to formulate the theory of gravity. He soon began to delve further into the idea and vowed to explain the origins of gravity itself.

Gravity in space

Einstein went on to research gravity even further and explored an accelerating spaceship in space. If a person were to drop a ball in a spaceship, it would be impossible for that person to distinguish whether the ball dropped to the floor because of the acceleration of the ship, or because of gravity. Therefore, Einstein reported that all laws of physics (e.g. gravity and inertia) are exactly the same, but that space-time that includes matter is actually curved, rather than a straight line. This interconnects gravity with time and space, which is known as the space-time continuum. This explanation was backed up by a scientific study executed in 1919 that involved a solar eclipse, the orbit of the planet Mercury and the redshift of light, where they found that the positions of the stars shifted because of the curvature of the light. These results propelled Einstein into the realm of legendary scientists.


Gravity on Earth

Gravity on Earth is a little easier to understand than that in Space, as we feel its effects constantly for ourselves. Gravity acts on all objects equally, the only difference being the size and mass of the object itself. If two objects of different size and weight (for example, an elephant and a mouse) were put in a vacuum (where there is no air resistance), then they would both fall towards the ground at the same acceleration. It is this air resistance, and other forces at work once these objects are taken out of the vacuum that make them fall at different speeds. No matter what, though, all objects on Earth are pulled towards the Earth’s centre of Gravity – the centre of the Earth. Gravity is what keeps us firmly on the ground – without it, we would float off into space.

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