"Graviffraction" - Einstein's dream

It was in the year between 1904 and 1905 that Albert Einstein embarked upon three studies that would change the face of physics. The first was the study of heat. He studied Brownian Motion - the way in which particles in a colloid jiggle about. This explained how energy is stored in material as warmth. Ludwig Boltzmann had discovered the mechanical equivalent of heat. The second study took him into the realm of photoelectrics. Max Planck had discovered that light consists of a kind of "atoms". The term "atomiki" (indivisibles) had been coined by Democrit of Smyrna, who stated that only atoms and free space are real. The term was picked up by Dalton and JJ Thomson as the smallest, indivisible piece of material. So Planck, in his search for a new word, introduced the concept of a "quantum" for the smallest piece of energy. Planck's constant, when multiplied by the frequency of any particular colour of light, will tell you how many watt-seconds are the least amount of light of that colour that are possible. The third study by Einstein went into the nucleus of the atom, in the search for an explanation of the riddle of radium. How can a piece of metal stay warm - seemingly forever? Where is the energy coming from? Einstein's second work - on the photoelectric effect - was the one that brought him the Nobel prize. It related to the puzzle that light can travel at a huge, but fixed and finite, speed through free space - and therefore must consist of nothing solid. Nevertheless, when it collides with something it can cause that thing to move. Such calculations are traditionally based upon studies of momentum - the product of mass and velocity. We know what the mass is - it is nothing at all, because light is nothing at all. We also know the speed of light. In a vacuum, it is known as c (which is about 300 million metres persecond, or 186 thousand miles per second). So when we use the MKS system (metres, kilogrammes and seconds), we multiply zero by three hundred million - and this gives us the momentum of light. It must surely be nil. However, when light hits an atom of metal it can throw out an electron from the metal. This is the photoelectric effect. Planck goes into some detail about the quantization of energy in his Nobel prize lecture: http://nobelprize.org/physics/laureates/1918/planck-lecture.html So we can say that one quantum of light delivers one single electron. The fact that the electron moves means that it has momentum. That is the product of the mass of the electron and its speed. So when we divide the momentum by the speed of light, we come up with the mass of a quantum of light. This is a sensation. Energy should be weightless, but here we find that it has mass. Einstein then continued his studies of the movement of the electron by likening that movement to its behaviour under the influence of a voltage. It turns out that for each frequency of light, there is an "electron-volt" rating which describes what would happen if that light struck an electron. The electron-volt value can be obtained from Planck's result in Joules (Watt-seconds) simply by multiplying by a special constant. His researches showed that the electrons are held in place inside the atoms by means of known voltages, the work functions. When light sets them free, the energy of the light in electron-volts is divided up two ways. The first part of the voltage if that which is needed to overcome the work function. The second part is the energy that is left over in the liberated electron. This work on the photoelectric effect was so important because it tied together many loose ends of physics. The spectral lines of light could now be defined as electron-voltages, and one could tell exactly where the light originated in the atoms. The atom was now looked upon as an electrical machine, and one could predict how metals would behave when used as photocells, for example. So the whole world of photoelectrics arrived - with sound-stripe on film and invisible-ray burglar alarms. At the same time, one could predict the properties of metals in an electroplating bath (although the photoelectric work-function was becoming supplemented with the electrochemical work-function). Einstein received the 1920 Nobel prize for physics - but it was delayed for a year. He received the prize itself whilst on board a ship visiting Japan. His lecture to the Nordic Assembly of Naturalists was not his acceptance speech, therefore. Already he is thinking of relativity: http://nobelprize.org/physics/laureates/1921/press.html We have entered into a world where matter has mass (weight under standard gravity), and so also has energy. But are the two kinds of mass the same? When we have a lump of material of mass M1, and place it at a distance D from a second piece of material of mass M2, we get an attraction between the two. The law is simple. It is M1 times M2 divided by D and divided again by D. That calculation defines the acceleration, or pull, that one piece of material will exert on the other. But what of light? Max Planck had said that the smallest quantum of light is h times v. Here h is Planck's constant and v is the frequency of that light. Einstein now delivered his famous clich