Read The Return (Enigma of Modern Science & Philosophy) Page 2
Einstein wondered what it was like to sit astride a photon of light and describe the world from its perspective. The basic assumption was that a photon had a continuous existence. What if it hadn’t?
A photon comes into existence when an atomic electron drops from a level of higher energy to one of lower energy. We envisage either a particle or a wave heading off into space at the speed of light. This speed (300,000 kilometers per second) is way beyond our everyday experience and we have no sense of how fast it is. In fact, Einstein in his Special Relativity Theory set down the axiom that nothing travels faster than light.
There is no real definitive proof of this axiom but the laws based upon it have made predictions that subsequent observations have proven true. This basic postulate underpins all of science in the post Einstein era. Yet can it be falsified? Karl Popper, the Austrian philosopher whose ideas on scientific theory have played a big role in our conception of what constitutes scientific validity, sets great store on the falsifiability of any scientific proposition or theory. If you cannot devise a test that can prove a theory false then it is not a theory that is truly scientific.
Applying this to the speed of light is enlightening, to use a smug pun. Since we use light to measure all phenomena, it obviously puts an upper limit on the scale of what we can measure in terms of speed. We can never prove by experiment that anything travels faster than light until we discover a phenomenon that travels at super-light speeds. This dilemma certainly throws a spanner in the works for the falsifiability of the light speed theory.
It pays to examine critically these base axioms of science. If we were to accept that there is no limit to speed of a phenomenon then the laws of science would undergo a revolution.
Maybe we need to ask quasi-philosophical questions about the reality of light before we undertake our scientific endeavor. What is light? Some say it is a particle-like entity - a photon. This photon is, in some sense, a packet of energy that is concentrated in a tiny volume of space. Again this tiny space is way beyond our normal human sensibility and measurement ability. Yet we can perceive the effect of a single photon as a speck on a photographic plate. It has a real reality. Yet others call light a wave phenomenon. A wave is the polar opposite of a particle in that its presence is spread out in space and keeps spreading as long as the light wave leaves its source behind in space-time. After many billions of years it can cover nearly the entire known universe. It becomes a gigantic wave that yet mysteriously reduces to a speck on a screen, located in a non-special space-time location such as the planet Earth.
There is physical evidence for the wavelike presence of light because we know that light waves interfere with each other, sometimes canceling, sometimes adding. Such interference is a characteristic of waves. The famous two slit interference experiment of light underpins most of the theory of quantum mechanics.
Because it is so important, it is worth going into what actually the experiment tells us. The set up is a single source of light that shines on a screen that has two slits allowing two streams of light to pass through. These two slits allow light pass through to a photographic screen. The image on the screen is one of bands of lightness and darkness. These are areas where the waves have interfered - the dark areas arising from the waves canceling each other out, the bright areas resulting from the waves reinforcing each other. This in itself is pass-remarkable and is something that any kid has often experienced as he whiled away pleasant moments throwing stones into the still water of a pond.
What makes this set up one of the most enigmatic experiments in all of science is that when the source of light is made so weak that only single photons pass through the slit screen, the bands of light and dark still emerge. The single photon acts like a wave - one that interferes with itself. If one of the slits is closed the bands disappear and a uniform dispersion of the light is seen on the screen - the interference disappears.
This experiment has caused both scientists and philosophers endless difficulty. How can light be both a particle and a wave? There was an inbuilt inherent contradiction in reality. The scientists shrugged their rationalistic shoulders and adopted the so called Copenhagen Interpretation and accepted that when you look for a wave - you get a wave, and when you look for a photon - you get a photon. The philosophers toiled away but eventually the associated mathematics and science arising from the developing theory became overpowering and the blatant contradiction was lost in the complexity that even the scientists struggled to follow.
Yet the basic problem remains. One phenomenon can’t assume two realities. The very basics had to be re-examined and perhaps overthrown. Maybe light was not so special after all. Someone had to think outside the box.
Inside the box the development of the theory developed at an unparalleled speed in the short history of science. The Einstein revolution of General Relativity gave way to the weird world of Quantum Mechanics. The latter half of the twentieth century saw the development of the Standard Model of Particle Physics which characterized all the myriad constituents of nature and unified all the forces excluding gravity. Gravity was the link back to Einstein’s General Relativity and colossal attempts were made to include gravity in quantum theory, leading to the monster of String Theory with its many dimensions and infinite universes.
The advances of scientific theory are truly staggering. Yet they stand on some really shaky conceptual foundations. If these foundations fail, as fail they must as Popper asserts, then the whole edifice will come tumbling down.
One of the potential Achilles’ heels of modern scientific theory is the finiteness of the speed of light. It was Einstein’s greatest achievement but it may also be his biggest misconception.
So what is light? As already said, it is a release of energy when an electron drops from a higher energy level to a lower level. This energy then travels outward from the electron in a random direction. This point is an essential premise. There is no way to foretell what direction the packet of energy takes. In this sense the single packet is a photon - a discrete energy packet localized in space that travels at this maximal speed. But how does the packet travel? This is one of the deepest questions we can ask of reality. The other is - what is it that makes an energy packet or what is energy?
We know that light can travel in a vacuum. Now a vacuum of old was considered just that - space with no mass or energy. Yet modern quantum theory does not allow such exactitude. Heisenberg’s Uncertainty Principle is another of the basic axioms of quantum theory. One form of it dictates that conjugates properties such as energy and time are limited by a tiny constant called the Planck constant (another of the very basic tenets of quantum theory). This is sometimes written as ΔE*Δt≥h, where ΔE is a tiny increment of energy, Δt is a very small interval of time and h is Planck’s Constant which is a very small number.
Now Einstein in his Special Relativity theory also links energy E and mass m by his famous formula E=mc2 where c is the velocity of light. In a vacuum we say there is no mass but the Heisenberg uncertainty does not allow exactly zero mass so the vacuum must have tiny fluctuations about zero mass. This effectively means tiny fluctuations in energy. The vacuum is now seen as a teeming world of energy fluctuation where particles and their anti-particles are now forming. They exist for the briefest of times - way outside our normal concept of seconds, micro or even nano seconds. Then they annihilate with each other and create energy. The process tick-tacks at an incredible frequency. It is through this tumultuous environment that the packet of energy, that is light, has to propagate.
It is conjectured that the light packet does not stand adrift of the mêlée but is buffeted about by the vacuum. It follows a zigzag path that to our macro-classical scale appears as a straight line of a classical particle. But photons are not loners they hunt in huge packs so studying the behavior of a single one tells us little of the pack behavior. Photons are emitted in their billions and each takes a random direction from the source. This spreads out spherically in space-
time just like a wave. Light as we sense it is a wave. We never experience a single photon.
Yet we said that we can make a source so weak that something like single photons impinges on the double slit screen. We still get interference effects even though each photon is dispatched separately. How can this be so? One explanation could be that the photon does not pass through the vacuum without affecting the underlying chaos of particle, anti-particle, creation and annihilation. What pushes the photon along through the vacuum is this very interaction. The photon impacts on the underlying structure of the vacuum and this impact spreads out through the vacuum as a wave - like a pressure wave ahead of a speeding bullet. This wave is not constrained to travel at the speed of light. There is no resultant sonic boom effect. Cause and effect are reversed as the photon travels into a future created by its own very past.
So in the case of the double slit experiment where photons are singly emitted into the experimental set-up, the vacuum wave created by the photon passes through both slits and causes the resultant dual waves to interfere with a resultant effect on the path of the following photon. The same light and dark bands emerges after a large number of consecutive photons.
One of the oddities of the double slit experiment was that the bands disappeared if an effort was made to determine through which slit a lone photon had passed. But this effort has an in built self-defeating mechanism. The minimum effort to detect the passage of the photon would be to use another photon at the designated slit. But this single photon disrupts the background vacuum and destroys interference potential of the emerging wave. So the bands are indeed expected to disappear.
So where does this leave our view of light. Light when it travels normally as billions of photons can be viewed as a wave, reflecting the waviness of the background vacuum. A single photon acts like a particle but is associated with a unique background wave that fills all of space. This background wave must travel at speeds greater than the speed of light. It is the forerunner of the light quantum preparing the route that it must take in its future. The question, of what is light, reduces to what is a photon or what is energy. This is altogether a much deeper question.