### How To - Understand Physics in 5 Minutes

How To - Understand Physics in 5 Minutes

In 1665 a recent Cambridge University graduate decided to sit and think about the motion of objects. Isaac Newton had an ambitious goal, he wanted to describe the motion of all objects, from a ball to a planet. He realized that many object move because of gravity and so his thinking included gravity. Within two years he had produced a few simple laws that described the motion of all known objects with great accuracy.

It was a remarkable achievement. Newton's Laws remained the cornerstone of physics for centuries.

Then suddenly in 1905 another recent graduate published a theory that showed something amazing. It showed Newton's equations would fail badly if used to describe objects traveling at very high speed, and it gave more accurate equations. The new equations held a big surprise, they predicted that objects could never go faster than the speed of light. Nature imposes a speed limit!

Einstein's new theory was not just an improvement on Newton's theory, it was a total replacement that gave a deep insight into physics and the world it describes. And all this from a physics student who was average in university and could not find a job when he graduated! Albert Einstein's theory became known as "Relativity". It took just a few years of thinking. It changed physics forever.

So now all was good, Physicists could predict the motion of objects with remarkable accuracy. Some even claimed there was nothing else to do and physics was over!

But nature had other ideas. By the early 1900s experimental physicists were discovering new objects. These new objects were confusing, but they all had one thing in common - they were extremely small. At first many scientists refused to believed they even existed, but soon atoms, electrons and photons became accepted.

Of course, describing the motion of these new objects was easy - just use Newton's theory, or if you wanted more accuracy use Einstein's theory. Right? Wrong. When this was tried the results were terrible.

New laws were needed. But this time they were not produced by a recent graduate. It took a generation of physicists, each contributing critical parts to the puzzle, and it was not finished until the 1950s. It was a long hard slog. The laws, designed specifically for small objects, became known as Quantum Mechanics. This time the mathematics was not simple as in Newton and Einstein's case - it was quite advanced and complex. But the accuracy was there. The theory was incredibly accurate!

If you had to summarize Quantum Mechanics in one sentence try this.. "small objects behave very differently than large objects". Who knew!

What happened to Einstein? He never made the transition to the new world of Quantum Mechanics. He understood the mathematics, and even made some critical contributions in the early days, but he rejected its underlying philosophy. However, he had one more giant trick up his sleeve. In 1915, ten years after producing his Relativity theory be produced a much broader theory that included gravity - the thing that got Newton started 250 years earlier. His new theory was called "General Relativity". It's still in use today, because nobody has found a better description of gravity.

So physics is built by three towering achievements: Newton's Laws, Einstein's General Relativity and Quantum Mechanics. The first two were produced by single individuals who's names became legend. The third required a huge team - a whole generation of physicists.

Where does physics stand today? Using giant accelerators such as the Large Hadron Collider (LHC) at CERN experimental physicists are finding even smaller objects and there are hints that Quantum Mechanics may have problems describing them. Not only that, but physicists want to unify General Relativity and Quantum Mechanics into one theory.

Perhaps we need a new physics graduate - preferably one who cannot find a job and has time to think!