From Rutherford comes the parable of the two desks. One desk is solid and exists in the solid world of our daily experience, the other is mostly empty space, ghostly and exists in the world of physical ideas. Which desk would be the real one? What is your opinion?
The solar system model of the atom is impossible
The classic model of electrons as little charged balls circling around a positive core encountered serious problems:
Why are the orbits of the electrons around the atom not circular like planetary orbits but spherical? The hydrogen atom with only a single electron in such a circular orbit should be flatter than a dime. But spherical orbiting electrons which would constantly have to change their orbits, buzzing around like annoying flies around your head, are even more inconceivable.
Is it possible that the circular orbit of the electron slowly changes its tilt thus creating a sphere of ephemeral presence? This would be unstable with heavier atoms having multiple electrons repelling each other.
The image of electrons buzzing around, all of them together in the outer shell of any atom heavier than hydrogen, represents a highly unstable atom shell since they all will repel each other.
Why is it that orbiting electrons, which means changing constantly their velocities, do not lose their kinetic energy, as Maxwell equations predict, through the emission of electromagnetic radiation in order to eventually spiral down to the core?
The last-mentioned problem follows immediately from Maxwell's classical electromagnetic theory. A circular moving charge is technically equal to an alternating electric current. An alternating current generates a changing electric field and therefore EM-waves. That is the principle of any radio transmitter. Emitting EM-waves mean loss of energy. The moving electron should therefore quickly lose its kinetic energy in an extremely short time.
In fact, the number of questions kept increasing instead of decreasing after each new discovery. Incidentally, this expanding sea of unknowns is nowadays still the case and it is not expected that this will change in the foreseeable future.
"We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance. "
John Archibald Wheeler, 1911 - 2008
Energy = Mass according to Einstein
In setting up his special theory of relativity in 1905, Einstein derived the equivalence of mass and energy: E = mc2 [17]. The meaning of this astounding simple formula is often interpreted as the idea that mass can be converted into energy (and vice versa). But Einstein's own interpretation is that mass and energy are two sides of the same coin. That means, a certain amount of energy has also a corresponding amount of mass. A small lump of matter therefore represents an enormous amount of "solidified" energy. A mass of 1 kg represents an energy of 9x1016J. Compare this with the total annual energy consumption of The Netherlands: 3.1 x 1018J: about 35 kg of mass.
The formula says also that the mass of an accelerated object increases with increasing speed. Some form of energy has to be transferred to the object in order for its acceleration to happen. The kinetic energy, the energy a moving object has by its movement, will increase and therefore, conform E = mc2, also its mass.
The increasing mass with velocity is an effect that must be seriously considered in large particle accelerators, such as the CERN Large Hadron Collider in Geneva. Protons are accelerated to enormous speeds, very close to the speed of light - and therefore also to considerably larger masses. Because of this increase in mass they need a correspondingly adjusted strong magnetic force field to keep them in their precise circular orbits. At particle speeds very close to that of light, the supercooled magnets used to hold the particles in their orbits must be very precisely adjusted to exert the required larger centripetal forces. But in our everyday environment this effect exists too. E = mc2 means that a fully charged AA NiMh cell will have an extremely minute amount of mass increase compared with the discharged state. Something in the order of 10-10 grams.
It may even be that energy is the primary substance and that mass is just a characteristic of it. Mass is the experience of the effort we have to make to get matter moving (or to slow it down). This is known as inertial mass. Mass is also a source and receiver of gravity, which is known as heavy mass. Both may just as well be properties of primary energy. Since 2012, physicists acknowledge the existence of the Higgs field. A field from which every particle receives its inertial mass. The Higgs field is explained as a field that opposes acceleration, it gives objects inertia. It does not oppose non-accelerated movement. Thus, a new hypothetical field is added to the set of hypothetical fields that the physicist usually considers as being real.
With his General Theory of Relativity - introduced 1915, 1919 confirmed, 1930 generally accepted - where Einstein assumed inertial forces to be the same phenomenon as gravity, Einstein showed that gravity should not be seen as a force but as an effect of curved space-time, which is too difficult to imagine. I have great trouble trying to imagine 3-dimensional curves in 4-dimensional space-time.
Anyhow, the edifice of classical physics - Newton's hard little balls model, causality and the continuity of time, fixed space and time, energy as work in stock - was teetering and started to collapse. A growing and continuously expanding need for more research was descending on the puzzled and puzzling physicists.
Spectral lines. Niels Bohr quantizes the atom
Figure 4.6: Line spectrum of glowing hydrogen gas on a logarithmic scale.
Source: Wikimedia Commons.
One riddle, in the steadily growing mass of new questions that emerged at the end of the 19th century, that could not be solved by classical physics concerned the existence of spectral lines [18]. A hot glowing gas emits EM radiation in only very specific wavelengths or frequencies, a line spectrum. See figure 4.6. Every element we know has its own unique identifying line spectrum signature. As a side: this is how we know that hydrogen is by far the most common element in our visible universe. Those precise lines presented an intriguing puzzle. How did these discrete separate frequencies of a glowing gas come about? Why only these special wave lengths?
The physicists Rydberg, Lyman, Balmer and Paschen had already discovered along empirically ways that a mathematical relationship existed between the wavelengths of glowing hot hydrogen gas, the Rydberg formula [19]:
1/= R(1/n2-1/m2) R=1,097373 x 107 m-1
In this formula, n and m represent integer positive numbers (1,2,3,4,.. etc.) where m> n. Supplying numbers for n and m will yield specific distinct wave lengths. Choosing for instance n=2 and m=3 yields λ = 656 nanometer (nm), which is orange light and is the first Balmer line (Ba-α). The Rydberg formula proved very impressive in its precise predictions, so all the more provocative that a theoretical derivation from classical physical principles had not been found for this rather simple mathematical relation. Nobody at the start