SearchUser loginNavigationCreate new accountTeam AgonistEditor in Chief: Steve Hynd ThoughtfulGlobalTimelyMixed Bag of Candy: Corner: Brian Downing's Picks: Numerian's Numbers: Who's onlineThere are currently 3 users and 1191 guests online.
Online users:Syndicate |
How did physics become so strange?I started to write this little essay in response to some physics questions that brodix raised. This will not be as good as the best popular science book ever written but hopefully it will illustrate why modern physics doesn’t ever seem to give straight answers anymore to even the most simple questions. It all started in the 1860s when this man developed his theory of electrodynamics:
At first nobody noticed. Maxwell predicted the existence of electromagnetic waves (but didn’t live to see this prediction experimentally verified) and correctly identified light with electromagnetic waves. This seemingly settled an old score once and for all in favor of Christian Huygens theory of light and relegated Newton’s corpuscular theory (proposed in his famous work, Opticks) to the dustbin of history. There was just one little problem and over time it grew so big it could no longer be ignored. Until then all natural laws were well behaved. They don’t discriminate against you if you happen to live on another star that zips through the cosmos at a different rate of speed than our solar system. Physics laws are usually written down with respect to inertial frames of references (i.e. usually represented by a simple cartesian grid). Inertial means that these systems can have relative motion but don't accelerate. Natural laws could always be transformed between such reference system so that by just representing the coordinates of system 1 in those of system 2 you again retain the exact same form of your equations (this is referred to as being invariant under Galilean transformations). Maxwell’s equations misbehaved. The solution at the time seemed straightforward. Every other wave phenomenons known to man had a mechanical medium e.g. water waves or waves in air to transport sound. So it seemed quite obvious to assume that there must be some very thin and fragile kind of aether to carry electromagnetic waves. With this interpretation not all inertial systems are created equal after all. There are some that are special because they are motionless relative to the aether. The alternative seemed just unthinkable. To illustrate why let’s construct a little thought experiment from the far future. Let’s assume it is the year 3000 and against all odds mankind is still around and your grand1-grand2-grand3…-grandn-niece 10E5 removed just won the pan-galactic lottery. She decides to spend some of the loot on a snappy space yacht and promptly gets lost in a bad part of the solar system because her Galactic Positioning System malfunctions. To her great dismay she sees a pirate space vessel approaching her at ridiculous speed (RS) firing rail guns at her that eject dark matter pellets from the pirate vessel at terrible speed (TS). She is a smart girl and knows that the pellets will hit her beautiful craft at a speed of RS+TS and cause terrible damage. At the same time the pirates also fire their laser weapons at her. The laser light travels a light speed c when it leaves the pirate vessel and although it moves in on its pray at ridicules speed RS the laser does not arrive at the yacht at RS+c but still plain light speed c. Keeping light speed constant in all inertial reference system makes the Maxwell equations properly invariant. On the other hand such outlandish behavior should be totally impossible in a Newtonian universe as well in one that has an aether. The velocities should always be additive. That is what common sense dictates. But all experiments have shown that nature prefers the preposterous scenario as described in my silly little example. It is a testament to Einstein physics instincts that he already rejected the common sense aether explanation before there was clear experimental evidence that light speed is constant in all inertial reference systems. Of course this astounding foresight didn’t come out of the blue. Physics for the longest time equaled mechanics. By the late 19th century this discipline was developed to perfection. I don’t use this term lightly. In the Lagragian and Hamiltonian reformulation of classical mechanics everything can be derived from 3 simple and intuitively understood first principles: Nature follows the same laws …
This formulation of classical mechanics is so stunningly and intoxicatingly beautiful that a young Max Planck was asked by one of his teachers why he would ever contemplate going into the field of physics. After all physics was completed. He was told there was nothing left to be done (other than maybe some minor third degree issues on the fringes). Fortunately he did not believe this teacher. I think what motivated Einstein was to get back to a theory that recaptured this kind of beauty that was threatened by Maxwell's equations - an aether that doesn’t adhere to the equivalence of frames of reference just wouldn’t do. In this sense Einstein was a reconstructist who inadvertently triggered the greatest revolution in physics due to his uncompromising rigor and an otherworldly unconventionalism. Turn in next week when I reveal what happened to your grand1-grand2-grand3…-grandn-niece 10E5 removed and may or may not get around to actually answer brodix questions. quax July 8, 2009 - 12:29am
( categories: Science )
|
![]() Premium AdvertisingAgonist Page on FaceBookAgonist Facebook Activity |