In 1905, **Albert Einstein determined that the laws of physics are the same for all observers** , **and that the speed of light in a vacuum was independent of the motion of all observers.** This was the theory of special relativity. He introduced a new framework for all of physics and proposed new concepts of space and time.

Einstein then spent 10 years trying to include acceleration in the theory and published his theory of general relativity in 1915. In it, he determined that massive objects cause a distortion in space-time, which is perceived as gravity.

## The pull of gravity

Two objects exert an attractive force on each other known as “gravity.” Isaac Newton quantified the gravity between two objects when he formulated his three laws of motion. The pulling force between two bodies depends on how massive each is and how far apart the two are. Even though the center of the Earth pulls you towards it (keeping you firmly on the ground), your center of mass recedes towards the Earth. But the more massive body hardly feels the pull, while with your much smaller mass you are firmly rooted thanks to that same force. However, Newton’s laws assume that gravity is an innate force on an object that can act over a distance.

Albert Einstein, in his theory of special relativity, determined that the laws of physics are the same for all non-accelerating observers, and showed that the speed of light in a vacuum is the same, regardless of the speed at which it travels. which an observer travels. As a result, he discovered that space and time were interwoven into a single continuum known as space-time. Events that occur at the same time for one observer might occur at different times for another.

While working out the equations for his general theory of relativity, **Einstein realized that massive objects caused a distortion in space-time** .

Although the instruments cannot see or measure space-time, several of the phenomena predicted by its warping have been confirmed. It is the experimental evidence of the theory.