We know that for waves to travel in space they need a medium. As a wave travels in a medium, the particles of the medium oscillate to and fro or up and down depending upon the type of the wave. For example as sound waves travel in air medium, the particles of air move to and fro, and this movement of particles results in alternate compressions and rarefactions in the medium. We know that sound waves also travel in liquid media (e.g. water) and some solid media. The particles of all these media also execute a similar to and fro waving motion when sound waves propagate through them. And we know that as water waves (or ripples) propagate in a pond, the particles of the medium (which is obviously water) oscillate up and down. So we consider water waves as transverse waves in contrast to sound waves which are longitudinal waves.
Then what about light? First of all, to the physicists of the pre-modern era, it was not clear whether light is composed of particles or waves. After centuries of debate on the nature of light, Young’s double slit experiment (1803) had confirmed that light behaves like waves. Half a century later, Maxwell, building upon the equations of electromagnetism, had calculated the speed of light waves as 3×108m/sec (referred to as ‘c’ by the physicists). These two developments posed two very difficult questions to the physicists of those days:
1) If light is a wave, then what is the thing which does the ‘waving’ or oscillation? In other words what is the medium for light waves? As far as scientists knew, there wasn’t any medium in the outer space. But if there isn’t really any medium in the outer space, then how could light, which behaves like waves, reach us from the Sun and other stars?
2) The next question that bothered physicists was that, if light travels at speed ‘c’, it is with reference to whom? Whenever we mention the speed of an object, there is always a reference frame to it whether explicit or implicit. For example when we say that a car moves at 100kmph, we mean that the car moves at 100kmph speed with reference to the road (or to a stationary observer on the road). Obviously the said speed is not with reference to someone who is inside the car or to someone who is following the car on a bike. Similarly the propagation speed of a wave is always mentioned with reference to the medium in which the wave travels. When we say that sound waves travel at speed of 330m/sec, the said speed, though not explicit, is always with reference to the medium in which the waves travel. So, when Maxwell calculated the speed of light as ‘c’, it implied that this speed must be with reference to the medium in which light waves should be travelling. But as just been mentioned, there isn’t any medium in the outer space as far as scientists know. But if there is no medium in the outer space, the speed of light that Maxwell calculated is with reference to whom?
Before the advent of modern physics with all its weird theories, scientists believed in the existence of an ever pervading medium called Ether. Everything in this universe including planets, stars etc were thought to remain suspended and move about in this stationary universal medium. And this putative Ether medium was thought to act as the medium for light waves (hence the name ‘lumiferous Ether’). Though there was no proof of its existence, the Ether hypothesis had enjoyed good support from the physicists of the pre-modern era as that was able to explain how light waves from outer space could reach us on Earth and also was able to provide the answer for the reference frame problem. But over a relatively short span of time, the above Ether hypothesis gave way to the weird theories of the modern physics. And we must talk about three things here which made physics ‘advance’ in the wrong direction.
Michelson- Morley experiment: Michelson presumed that when Earth moved through the stationary Ether medium, it would result in what is called as Ether wind. So he predicted that light beams made to travel to and fro in perpendicular directions i.e. one light beam passed parallel to the Ether wind direction and another beam passed across the wind, would take different times to cover the same distance. But to the astonishment of the scientific community, Michelson’s famous experiment failed to detect any difference in the times taken by the two light beams and thus ruled out any such thing called Ether wind. From this and other observations (aberration of star light), scientists concluded that there isn’t anything like Ether in our universe. (We will discuss later why scientists are wrong to assume so and will expose the misconceptions upon which this famous experiment was devised).
Light and Electromagnetic radiation: From the work of great physicists like Faraday and Maxwell, scientific community had learnt more about electro-magnetism and electromagnetic radiation. It became known that electromagnetic waves get generated from relative motion between electric and magnetic fields. And the scientific community had realised that light is a form of electromagnetic radiation and that visible light comprises only a small part of the total spectrum of electromagnetic radiation. And having discarded the Ether medium, the intelligent physicists had ‘understood’ electromagnetic waves as ‘self propagating’ transverse waves with electric and magnetic fields oscillating at right angles to the direction of propagation. While we the ordinary minds may not correctly grasp the physicists’ imagination of these ‘mythical’ waves of transversely oscillating electric and magnetic fields, the point to note here is that, according to the intelligent physicists, electromagnetic waves (i.e. light waves) do not require any medium to propagate in space unlike mechanical waves (e.g. sound waves).
Emitter theory: But the above ‘understanding’ of the scientific crowd on EM waves had made the second question even tougher to answer i.e. if EM waves are self propagating and if they don’t require any medium , then Maxwell’s calculated speed of electromagnetic waves is with reference to whom?
At this juncture, some scientists believed that the calculated speed of EM waves must be with reference to the source that generated them (Emitter theory). But observations on neutral pion decay didn’t seem to support the ‘emitter theory’. Scientists observed that light photons (EM waves) travelled at the same speed ‘c’ whether they were emitted by fast moving particles (neutral pions) or slow moving particles. In other words, light photons’ velocity didn’t vary with the velocity of the source unlike the case with projectiles in our everyday world!
Another argument against the emitter theory was that Electromagnetic waves get generated when there is relative motion between a magnet and a conductor (e.g. copper wire). In other words, a source of EM waves contains two basic components (a magnet and a conductor) both of which move relative to each other. So if we assume that Maxwell’s calculated speed of EM waves is with reference to the source, which one of the two components of the source shall we consider as representing the source? I.e. shall we swear upon the magnet’s frame or the conductor’s frame as representing the reference frame of the source as a whole?
Imagine that we kept a magnet at rest and moved a copper wire with speed ‘v’ with respect to the magnet and generated EM waves. Here we may assume that the so generated EM waves travel at speed ‘c’ with reference to the magnet because this was the one at rest. In that case obviously the speed of the same EM waves becomes ‘c+v’ in the reference frame of the copper wire. But because motion is relative we can argue that it was actually the copper wire that was at rest and hence the Maxwell’s calculated speed ‘c’ must refer to the copper wire’s reference frame and not to the magnet.
But how can the generated EM waves travel at the same speed with reference to both the magnet and the conductor which are moving relative to each other? In other words, how can a light beam travel with the same speed ‘c’ with reference to two different objects in two different reference frames?
Emitter theory thus failed to solve the reference frame issue and the scientific turmoil continued. Amidst this scientific turmoil came Einstein with his weird and ‘wonderful’ theory of special relativity which mesmerised the confused scientific folk and ‘solved’ the reference frame issue. He said that the speed of light waves (i.e. electromagnetic waves) remains the same to every observer irrespective of one’s state of motion or reference frame. Special theory of relativity woven upon this weird law of constant speed of light then lead to the weird propositions of time dilation, space contraction etc and later paved the way for another weird theory called general relativity.
Now we will analyse each of the above things that mislead the scientific crowd and allowed the weird theories to sprout and flourish in the realm of science masquerading as modern physics.
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