We are
bounded in a nutshell of Infinite space: Blog Post #12,
Free Form #2: Relativity, yes we are doing this, it is what it is, it’s not as
bad as it seems.
On one of the most recent entries, we went over
the nature of relativity and the role it plays when analyzing microlensing and
other astrophysical phenomena that have to do with light and gravity. But what
exactly is relativity, the mythical and wonderful description of the universe
compiled, proved, and understood first by Albert Einstein in the first decade
of the twentieth century?
As we had presented in an earlier blog post:
“Relativity describes the nature of the Four-dimensional world we
inhabit, these dimensions being length, width, height, and time, 3 space
dimensions and a time dimensions. Working off this knowledge, Einstein
developed a description of all space as truly being a sort of fabric, a
space-time fabric, whose perception is changed based on individual reference
frames (from where you observe the event(s) ). Adding in the nature of the
speed of light in a vacuum, the one absolute constant in the universe, and the
nature of gravity and how it warps space time, bending the fabric, we can
understand how light is affected by gravity.”
Thus, we have briefly explained the effect
of gravity and light when these two interact with one another, but we have not
delved into the inner nature of relativity, and the most important realization
that serves to understand the what is actually occurring not only when gravity
is in play, but in all physical reality.
The understanding that cements all
relativity, and re-defined physics, was establishing that there is one universal
constant in the universe, one fact that never changes, from which all of
relativity is derived: the speed of light is the maximum speed of the universe,
an unchangeable value that will always be the same while in a vacuum (light can
change speed and direction when it changes the medium it goes through). Why is
light constant?, you might ask: because it needs to be, and the evidence that
proves it is more than conclusive. But another explanation for why it is
constant is that light (and by this we mean the entire electromagnetic
spectrum) is one of the 4 fundamental forces of nature, and thus mold much of
reality around themselves.
Regardless, the fact is that light is
assumed to be constant in any case, and because of this, many sets of equations
were created, none of which have been dis-proven after many tests and
experiments, essentially confirming that relativity with a constant speed of
light is the most plausible system.
Now then, as to the actual effect light has
on objects and reference frames, this is when things get a bit more confusing.
So light we have just seen that it has to be constant in any circumstance, so
all other variables, like space and time, are the ones that must change and
make accommodations in order to maintain a constant speed of light. The classic
example Einstein gives in his papers on Special and General Relativity is the
case of two persons, one on a train heading in a direction towards a point
where a lightning bolt just hit the ground, and another person stands some
distance away and can observe both the train and the lightning bolt. In this scenario, the person on the train is
moving at a speed v, who will hit the
rays of light with this speed and thus (one would expect to) perceive the speed
of photons as the intrinsic speed of light minus the speed of the person. This would
differ from the person outside the train, seeing the lightning bolt come and
thus (expect) to perceive light at its normal speed.
However, the speed of light must be
CONSTANT at all times, so the person on the train must have something change in
order for him to experience the speed of light at the correct value. What
happens is, as Einstein describes in Special Relativity, that the person moving
with speed v experiences time (and
length and differently, it slows down in his (moving) reference frame and so
the speed of light he perceives is maintained at the constant rate.
For the person outside the train, he would
see the light coming from the lightning bolt at its normal speed, without any
special considerations to be taken into account. But as he sees the light going
towards the train in the distance, he would clearly see the light in direction
of the train has the same speed as the light that reached his reference frame, maintaining
the constant speed of light and set consolidated with the perception of the
person on the train, instead of two people experiencing two different speeds of
light.
This sums up the overall principles of
relativity, but additionally gravity comes into play in a deeper sense and with
it the entanglement of quantum mechanics and how it can (or cannot) be consolidated
with general relativity, which we will leave for another time.
Nevertheless, this sums up a lot of the
intuitive nature of relativity, and hopefully compels you to believe the speed
of light never changes, but of you are not, go and prove it (just bear in mind
people have been trying to do just that for about a century).
Not only is the speed of light constant, it is also the absolute limit of how fast you can go!
ReplyDeleteI’m curious to read your treatise on gravity and quantum mechanics next time!
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