Wednesday, 2 February 2011

Perceptions of Light, Time Dilation (again).

I'm still puzzling over our seemingly self-imposed light-speed limitation. In an earlier post I mentioned the Victorian-era 'ether' concept, since disproven, that the entire universe was filled with a mysterious substance that limited the speed at which matter (including light) could travel. This theory (along with my 'perfect matter' idea) is officially in the trash can, but if there is no 'ether', how can we maintain that nothing can travel faster than the speed of light? The limiting factor seems to be in the notion of time and 'mass increase' - but, as I mentioned earlier, it is quite possible to leave time out of the question, and even any equation, for observing physical behavioural patterns concerning light; as for mass, I will try to deal with that in a later post.

Before I get there, I'd like to ask (myself) a few more questions on light-speed, namely concerning Einstein's theory and the findings of Hubble. Einstein's relativity showed that the universe was rapidly expanding (although he himself didn't believe it), but Hubble proved it by measuring the spectrum map of light from different galaxies; Hubble recorded marked 'spectrum shifts' towards the red for the light of galaxies moving away from us, and shifts towards blue for those nearing us. Hubble's findings at first sight follow rules similar to Doppler's - a sound from a source moving towards a listener through air sounds at a higher pitch, and the sound moving away sounds lower - but here may be another (additional) explanation for the shift in the light emissions of different galaxies.

It is a known fact that the speed of light, c, is indeed a constant; it travels at the same speed no matter the frequency of its wave. My main nagging question concerns the relation between a light wave's 'speed' and the object that emits it: in a situation where a light wave's source is 'at rest' (its 'speed' is irrelevant in the absence of any other object, it is 'relative' only unto itself), if indeed there is no 'ether', shouldn't the light's speed remain constant (relative) to its source? Why do scientists insist that, when we add an observer into the equation, that the speed of a light wave (relative to its source) cannot be added/subtracted from the speed of the light source relative to the observer?

Time dilation can be inferred from the observed fact of the constancy of the speed of light in all reference frames.
This constancy of the speed of light means, counter to intuition, that speeds of material objects and light are not additive. It is not possible to make the speed of light appear faster by approaching at speed towards the material source that is emitting light. It is not possible to make the speed of light appear slower by receding from the source at speed.
"Time Dilation", Wikipedia.org, 2011-02-02


It is the "all" in "all reference frames" that bothers me. "All" reference frames... known to us thus far? Measurable by us, again, thus far? I left the second half of the quote in place for context: it just shows that, once it is emitted, light does remain at a constant speed, but I do question the effect of one's movement relative to a light source, namely in our perception of the light's frequency. I'd like to imagine for a second that light can travel faster than 'itself' (relative to 'our' frame of reference), and revisit two concepts (one mentioned above) commonly referenced in discussions on relativity.

Firstly, the above 'Doppler effect': what if, in addition to the red/blue shift caused by the (seeming) increase in frequency caused by the relative velocity between the star and the observer, an 'accelerated speed of light' did figure into the equation? Here on earth, sound is limited in velocity (by our atmosphere, a constant between the source and the observer), but if there indeed is no 'limiting ether' in space, the speed of a light source should figure in the speed of the light it emits (relative to the observer). Were this true, the spectrum shift from an approaching star would be doubly amplified, once by the source's motion relative to the wavelength of its light, and again by the speed at which it was travelling. Imagine a star travelling towards us that emits one burst of light energy in our direction. If the speed of its light is added to the speed of light itself, the frequency of the approaching beam will seem, from the observer's point of view, to be more compact (higher) than would be if both the source and observer were at a state of rest relative to each other; this also would cause a shift in the same direction as the Doppler effect, a shift that could perhaps even be multiplied by the same.

Secondly, time dilation was supposedly proven by an experiment in which the level of cosmic ray muon radiation was measured at the top of a mountain, then at a much lesser altitude; muons decay rapidly in the earth's atmosphere, yet many more made it to lower altitude than expected, and this was attributed to time dilation (time was 'slower' for the almost-light-speed travelling muons), but what if the muons, shot out from massive explosions perhaps the origin of our universe, were in fact travelling faster than light upon their arrival to earth?