Between 1942 and 1945 an entirely new industry, employing tens of thousands of people, was created in America. It was one of the most significant events of the past century. America was at war with Germany and Japan and was in a race to development the atom bomb before its enemies.
There were peaceful uses for nuclear technology. Radiation machines to treat cancer, radio-pharmaceuticals used in nuclear medicine and power generation.
It took only three years to develop the atom bomb but the science behind this began more than a century earlier.
In 1814, Joseph von Fraunhofer invented the first spectroscope using a prism, diffraction slit and telescope to analyze light from the sun.
In 1859, Robert Bunsen and Gustav Kirchhoff used a spectroscope to analyze light emitted by a heated sample. They identified the characteristic spectral lines of lithium, potassium and sodium and proved that each element had a unique spectra. In the process, they detected spectral emission lines of an undiscovered chemical element, which was later found to be caesium. A year later Bunsen discovered rubidium using the same technique.
By 1862 Foucault had measured the speed of light to be nearly 300 000 km/s and found it to be constant regardless of the speed of the moving light source. The Michelson–Morley experiment (1887) refuted the stationary aether theory which led to the development of the Lorentz transformation.
Hendrik Lorentz shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect. He also derived the transformation equations underpinning Albert Einstein's theory of special relativity.
Einstein used these unexpected ideas to formulated the theory of special relativity in 1905, deriving the Lorentz transformation, length contraction and time dilation. Einstein was also inspired by Maxwell's theory of electromagnetism . . . Space dimensions and time were no longer constants.
Einstein's theory of relativity is one of the foundations of modern physics (alongside quantum mechanics). Einstein is best known for his mass–energy equivalence formula E = mc2 (Energy = mass times the velocity of light squared) and for his discovery of the law of the photoelectric effect, a pivotal step in the evolution of quantum theory.
Einstein realized that the principle of relativity could also be extended to gravitational fields and in 1916 he published a paper on general relativity. He continued to deal with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules. He also investigated the thermal properties of light which laid the foundation of the photon theory of light and the photoelectric effect.
Einstein proposed in 1905, that the energy of electrons, knocked out of certain metals by light (the photo-electric effect), depended not on the brightness but on the colour (on its frequency). He suggested that light did not travel in waves, as had been proven by many experiments, but that it travelled in 'energy quanta' (now called photons). Photons had energy which depended entirely on the frequency and this could be transferred to electrons. (A brighter light of the same frequency merely produced more electrons). The idea of photons was not widely accepted until S. N. Bose derived the Planck spectrum in 1924.
The electron.
In 1896, at Cambridge University in Britain, J.J. Thomson demonstrated that cathode rays were negatively charged particles, about one thousandth of the mass of hydrogen atoms, which could be deflected with a magnetic field. And they were emitted from any element used as a cathode, so they had to be a constituent of all atoms.
He used a glass tube sealed at both ends containing two metal plates (the anode and the cathode) attached across a battery. When all the air was pumped out, the charged emptiness in the tube glowed. Changing the anode plate into a cylinder inside the tube allowed the stream of electrons to pass through the cylinder and hit the glass end of the tube causing it to fluoresce. Enlarging the glass end and covering it with phosphors created the cathode ray oscilloscope also know as a TV tube. The stream of electrons from the cathode could be deflected by magnetic fields.
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Ziff under fire
Science FictionAmerican security agents, suspecting Dr Zhang is hacking into U.S. computers, try to abduct him. The Canadian Security Intelligence Service is also interested. And Murga is back in town with a proposition. I agree to tests of my super normal flyi...
