There are all sorts of resonances around us, in the world, in our culture, and in our technology. A tidal resonance causes the 55 foot tides in the Bay of Fundy. Mechanical and acoustical resonances and their control are at the center of practically every musical instrument that ever existed. Even our voices and speech are based on controlling the resonances in our throat and mouth. Technology is also a heavy user of resonance. All clocks, radios, televisions, and gps navigating systems use electronic resonators at their very core. Doctors use magnetic resonance imaging or MRI to sense the resonances in atomic nuclei to map the insides of their patients. In spite of the great diversity of resonators, they all share many common properties. In this blog, we will delve into their various aspects. It is hoped that this will serve both the students and professionals who would like to understand more about resonators. I hope all will enjoy the animations.

Origins of Newton's laws of motion

History of mechanical clocks with animations
Understanding a mechanical clock with animations
includes pendulum, balance wheel, and quartz clocks

## Sunday, May 29, 2011

### General relativity

 General relativity An extension that Einstein added to his relativity theory explained above, adds in the effects of acceleration and gravity. He called this extension "general relativity", in contrast to "special relativity" that he used to refer to his physics of high speed motion. Concerning gravity, he guessed that in a laboratory inside a space ship coasting along in the presence of the gravitational field of a planet, that everything would appear the same as it would without the gravitational field. Only when the space men or women looked outside their ship could they tell that their path was being altered by the gravitational pull of the planet. Einstein created a math of space and time that would account for gravitational fields in a similar fashion as the above "special" relativity, by allowing massive bodies, such as a planet or star, to warp space and time. The gravitationally curved coasting trajectory of a spaceship would be a "straight line" in Einstein's warped space. This theory does give results consistent with Newton's gravitational theory and also predicts effects that Newton's theory did not, such as a slowing of time in an intense gravitational field. This slowing has been experimentally verified by the Pound-Rebka experiment done in 1959 as well as by other experiments in space craft. General relativity does not suffer all the paradoxes of special relativity. In general relativity we can assign unique properties to each point in space which depend on the energy-momentum density at that point. It is also easy to argue that the reference frame of space located far away from massive bodies forms an absolute reference frame. A valid criticism of general relativity is that it represents "physics via mathematical transforms" and thus does a poor job of the explaining at an intuitive level the causes of observed gravitational effects. Also, it generally is very laborious to use. Perhaps an ether theory of gravity would be a nice supplement to Einstein's theory.

What is space?

The debate between Einstein and Lorentz questions what space is at a fundamental level.

Einstein's view and that of most modern physicists is that it is an empty void without many properties, and in which elemental point-like particles move around. These particles include electrons, protons, neutrons, and photons, and many many other types of sub-atomic particles moving about and interacting via the rules of quantum mechanics. A soup of these particles brings with it a momentum and energy density which effects the curvature of space-time as prescribed in the Einstein field equation. This curvature of space is a property that Einstein's space supports, as well as the property that elemental particles can exist in it. In this view, electric and magnetic fields consists of exchanges of photons between other elemental particles. Efforts by physicists to change the view of gravity from Einstein's distortion of the metric into an exchanges of hypothetical particles called gravitons have so far failed.

Lorentz's view is that space is full of an ether and electric and magnetic fields are stresses in this ether. He would probably also subscribe to gravity being a different sort of stress of the same ether.

At a deep level we will never know what "reality" is. We really only know what our humanly senses tell us: what we actually see with our own eyes and feel with our own hands, etc. Scientific theories are tremendous abstractions from the sensations of our daily lives. We make these scientific theories of the world to explain events we detect via complex instruments but eventually see the results with our eyes. The theories help us invent technologies that help us on a very human level, such as saving a loved one from dying or allowing us to talk to a friend at home while riding on a train.

It is very possible that two different views of reality are equally valid given the scientific evidence we have, if they both result in a faithful reproduction of the world as we humans experience it. Even if one is slightly off in some domain it still may be very useful; for example, the use of Newtonian mechanics for all ordinary engineering design work where velocities are much much slower than the speed of light.