Relativity Theory
The theory of relativity was introduced by Albert Einstein around the
early
nineteen hundereds. It is a theory which enables the human mind to
understand
the possible actions of the universe. The theory is divided into
two parts, the
special, and the general. In each part, there is a certain
limit to which it
explains and helps to comprehend. In the special, Einstein
explains ways of
understanding the atom and other small objects, while the
general is designed
for the study of large objects, such as planets. The
theory of relativity having
being created, succeeded the two hundred year old
mechanics of Isaac Newton,
thus showing Einstein as more of a futuristic
thinker and adapter. Einstein
introduced the concept of Relativity, which
means that there is no absolute
motion in the universe. Einstein showed that
humans are not in a flat, absolute
time of everyday experience, but in a
curved space-time. Take for example the
Earth as a whole. The earth has a
circumference of around twenty five thousand
miles, and it can be covered
within a twenty-four hour time frame. Having this
completion of distance
covered within the set amount of time, shows that the
Earth rotates a
little over one-thousand miles per hour. it can be assumed that
something in
the solar system is not moving, and we can measure how fast the
earth is
moving by relative to the object. However, no matter what object is
chosen,
it is moving as well, thus showing that nothing is fixed and that
everything
is moving, and it is unknown how fast or in what direction. The
Theory of
Relativity is a theory compressing mechanics, gravitation, and
space-time.
Having known this, it is seen so that all things are related, but
can not be
thought of as individual. The Theory of Relativity is known for
having two
parts to it. The first part is the special relativity; the other is
the
general relativity. Special relativity is known for it’s publication
in
1906; it is used for microscopic physics, such as atoms and small
objects. The
other type of relativity, the general, is known for its
publication in 1916,
well after the birth of it’s counterpart. The general
half of the theory is
intended for astrophysics and cosmology, such as solar
systems, planets, and
large objects. A British Astronomer named Sir Arthur
Eddington, was one of the
first to fully understand the Theory of Relativity.
A little humor about his
intelligence can be seen to when he was asked about
there being three people who
understood the Theory of Relativity, his
response was "who is the third?"
The discovery of Quasars, the 3 kelvin
microwave background radiation, pulsars,
and possibly blackholes were studied
with to see the accuracy of the Theory of
Relativity with gravity. This
led the development of the space program,
telescopes, computers, etc...to
make better calculations of the accuracy of the
theory. The Theory of
Relativity has two main parts, the special and the
general. The internal part
of the special theory is in reference to any region,
such as a free falling
laboratory, in which objects move in straight lines and
have uniform
velocities. In the lab, nothing would appear to be moving if
everything in
the lab was falling, the movement of the lab is relevant to the
person that
is in the lab. The principle of relativity theorizes that
experiments in an
internal frame, is independent from uniform velocity of the
frame. An example
of this is the speed of light. The speed of light within the
internal frame
is the same for all, regardless of the speed of the observer. Two
events that
are simultaneos in one frame, may not be simultaneos when viewed
from a frame
moving relative to the first one. Movement looks different
depending on where
the observer is located, how fast it is moving, and in what
direction. An
interesting fact about the special relativity, is that the
mechanical
foundations of special relativity were researched in 1908 by a
german
mathmetician named, Hermann Minkowski. Minkowski ler einstein to
postulate the
vanishing of gravity in free fall. In any free fall, laws of
physics should take
on special relitavistic forms, this is what led to the
EEP(Eisteins Equivalence
Principle.) A consequence of EEP is that the
space time must be curved. It is
techinical, consider two frames falling
freely, but on opposite sides of the
Earth. According to Minkowski, spare
time is valid locally in each frame, but
since the frames are accelerating
towards each other, the two Minkowski
space-times can not be extended untill
they meet. Therefor, with gravity, space
time is not flat locally, but spaced
globally. Any theory of gravity that
fulfills EEP, is called a metric theory.
Along with the special side of the
theory, is the genral side of it. The
principle to show space-time curved by
presence of matter. To determine
curvature, requires a specific metric theory of
gravity, such as general
relativity. Einsteins aim was to find the simplist
equations, he found a set
of 10. To test the general theory Einstein performed
three tests.
Gravitational red shift, light deflection, and perihelion shift of
mercury.
To test light deflection, Einstein used the curve space-time of the
sun
light; it shoul be deflected 1.75 seconds of arc if it glazes the solar
surface.
The concept of gravitational lenses is based on the already
discussed and proven
relativistic prediction that when light from a celestial
object passes near a
massive body such as a star, its path is deflected. The
amount of deflection
depends on the massiveness of the intervening body. From
this came the notion
that very massive celestial objects such as galaxies
could act as the equivalent
of crude optical lenses for light coming from
still more distant objects beyond
them. An actual gravitational lens was
first identified in 1979. Another of the
early successes of general
relativity was its ability to account for the puzzle
of Mercury's orbit.
After the perturbing effects of the other planets on
Mercury's orbit were
taken into account, an unexplained shift remained in the
direction of its
perihelion (point of closest approach to the Sun) of 43 seconds
of arc per
century; the shift had confounded astronomers of the late 19th
century.
General relativity explained it as a natural effect of the motion
of
Mercury in the curved space-time around the Sun. Recent radar
measurements of
Mercury's motion have confirmed this agreement to about
half of 1 percent. One
of the remarkable properties of general relativity is
that it satisfies EEP for
all types of bodies. If the Nordtvedt effect were
to occur, then the Earth and
Moon would be attracted by the Sun with
slightly different accelerations,
resulting in a small perturbation in the
lunar orbit that could be detected by
lunar laser ranging, a technique of
measuring the distance to the Moon using
laser pulses reflected from arrays
of mirrors deposited there by Apollo
astronauts. One of the first
astronomical applications of general relativity was
in the area of cosmology.
The theory predicts that the universe could be
expanding from an initially
condensed state, a process known as the big bang.
For a number of years
the big bang theory was contested by an alternative known
as the steady state
theory, based on the concept of the continuous creation of
matter throughout
the universe. Later knowledge gained about the universe,
however, has
strongly supported the big bang theory as against its competitors.
Such
findings either were predicted by or did not conflict with relativity
theory,
thus also further supporting the theory. Perhaps the most critical piece
of
evidence was the discovery, in 1965, of what is called background
radiation.
This "sea" of electromagnetic radiation fills the universe at
a
temperature of about 2.7 K (2.7 degrees C above absolute zero).
Background
radiation had been proposed by general relativity as the remaining
trace of an
early, hot phase of the universe following the big bang. The
observed cosmic
abundance of helium (20 to 30 percent by weight) is also a
required result of
the big-bang conditions predicted by relativity theory. In
addition, general
relativity has suggested various kinds of celestial
phenomena that could exist,
including neutron stars, black holes,
gravitational lenses, and gravitational
waves. According to relativistic
theory, neutron stars would be small but
extremely dense stellar bodies. A
neutron star with a mass equal to that of the
Sun, for example, would
have a radius of only 10 km (6 mi). Stars of this nature
have been so
compressed by gravitational forces that their density is comparable
to
densities within the nuclei of atoms, and they are composed primarily
of
neutrons. Such stars are thought to occur as a by-product of violent
celestial
events such as supernovae and other gravitational implosions of
stars. Since
neutron stars were first proposed in the 1930s, numerous
celestial objects that
exhibit characteristics of this sort have been
identified. In 1967 the first of
many objects now called pulsars was also
detected. These stars, which emit rapid
regular pulses of radiation, are now
taken to be rapidly spinning neutron stars,
with the pulse period represent
the period of rotation. Black holes are among
the most exotic of the
predictions of general relativity, although the concept
itself dates from
long before the 20th century. These theorized objects are
celestial bodies
with so strong a gravitational field that no particles or
radiation can
escape from them, not even light--hence the name. Black holes most
likely
would be produced by the implosions of extremely massive stars, and
they
could continue to grow as other material entered their field of
attraction. Some
theorists have speculated that supermassive black holes may
exist at the centers
of some clusters of stars and of some galaxies,
including our own. While the
existence of such black holes has not been
proven beyond all doubt, evidence for
their presence at a number of known
sites is very strong. in conclusion,
relativity is a way of looking at
things, keeping in mind that everything is
moving, and that we really have no
way of know just how fast. This theory, along
with complex equations
developed many years ago, helped to explain certain long
misunderstood things
about planets and their movements. But the same thinking
about very large
objects, in motion, like stars, planets, solar sysems, simply
does not work
accurately when you look at microscopic things, like atoms. Too,
since the
development of the theory of relativity, we have made many
technological
advances that have allowed us to make accurate measurements, and
to basically
confirm the theory is correct.