The theory of relativity was introduced by Albert Einstein around the earlynineteen hundereds. It is a theory which enables the human mind to understandthe possible actions of the universe. The theory is divided into two parts, thespecial, and the general.
In each part, there is a certain limit to which itexplains and helps to comprehend. In the special, Einstein explains ways ofunderstanding the atom and other small objects, while the general is designedfor the study of large objects, such as planets. The theory of relativity havingbeing created, succeeded the two hundred year old mechanics of Isaac Newton,thus showing Einstein as more of a futuristic thinker and adapter. Einsteinintroduced the concept of Relativity, which means that there is no absolutemotion in the universe.
Einstein showed that humans are not in a flat, absolutetime of everyday experience, but in a curved space-time. Take for example theEarth as a whole. The earth has a circumference of around twenty five thousandmiles, and it can be covered within a twenty-four hour time frame. Having thiscompletion of distance covered within the set amount of time, shows that theEarth rotates a little over one-thousand miles per hour. it can be assumed thatsomething in the solar system is not moving, and we can measure how fast theearth is moving by relative to the object.
However, no matter what object ischosen, it is moving as well, thus showing that nothing is fixed and thateverything is moving, and it is unknown how fast or in what direction. TheTheory of Relativity is a theory compressing mechanics, gravitation, andspace-time. Having known this, it is seen so that all things are related, butcan not be thought of as individual. The Theory of Relativity is known forhaving two parts to it.
The first part is the special relativity; the other isthe general relativity. Special relativity is known for its publication in1906; it is used for microscopic physics, such as atoms and small objects. Theother type of relativity, the general, is known for its publication in 1916,well after the birth of its counterpart. The general half of the theory isintended for astrophysics and cosmology, such as solar systems, planets, andlarge objects.
A British Astronomer named Sir Arthur Eddington, was one of thefirst to fully understand the Theory of Relativity. A little humor about hisintelligence can be seen to when he was asked about there being three people whounderstood 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 ofRelativity with gravity. This led the development of the space program,telescopes, computers, etc. . . to make better calculations of the accuracy of thetheory.
The Theory of Relativity has two main parts, the special and thegeneral. 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 andhave uniform velocities. In the lab, nothing would appear to be moving ifeverything in the lab was falling, the movement of the lab is relevant to theperson that is in the lab. The principle of relativity theorizes thatexperiments in an internal frame, is independent from uniform velocity of theframe. An example of this is the speed of light. The speed of light within theinternal frame is the same for all, regardless of the speed of the observer.
Twoevents that are simultaneos in one frame, may not be simultaneos when viewedfrom a frame moving relative to the first one. Movement looks differentdepending on where the observer is located, how fast it is moving, and in whatdirection. An interesting fact about the special relativity, is that themechanical foundations of special relativity were researched in 1908 by a germanmathmetician named, Hermann Minkowski. Minkowski ler einstein to postulate thevanishing of gravity in free fall. In any free fall, laws of physics should takeon special relitavistic forms, this is what led to the EEP(Eisteins EquivalencePrinciple.
) A consequence of EEP is that the space time must be curved. It istechinical, consider two frames falling freely, but on opposite sides of theEarth. According to Minkowski, spare time is valid locally in each frame, butsince the frames are accelerating towards each other, the two Minkowskispace-times can not be extended untill they meet. Therefor, with gravity, spacetime is not flat locally, but spaced globally. Any theory of gravity thatfulfills EEP, is called a metric theory. Along with the special side of thetheory, is the genral side of it.
The principle to show space-time curved bypresence of matter. To determine curvature, requires a specific metric theory ofgravity, such as general relativity. Einsteins aim was to find the simplistequations, he found a set of 10. To test the general theory Einstein performedthree tests.
Gravitational red shift, light deflection, and perihelion shift ofmercury. To test light deflection, Einstein used the curve space-time of the sunlight; 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 provenrelativistic prediction that when light from a celestial object passes near amassive body such as a star, its path is deflected. The amount of deflectiondepends on the massiveness of the intervening body. From this came the notionthat very massive celestial objects such as galaxies could act as the equivalentof crude optical lenses for light coming from still more distant objects beyondthem.
An actual gravitational lens was first identified in 1979. Another of theearly successes of general relativity was its ability to account for the puzzleof Mercury’s orbit. After the perturbing effects of the other planets onMercury’s orbit were taken into account, an unexplained shift remained in thedirection of its perihelion (point of closest approach to the Sun) of 43 secondsof arc per century; the shift had confounded astronomers of the late 19thcentury. General relativity explained it as a natural effect of the motion ofMercury in the curved space-time around the Sun. Recent radar measurements ofMercury’s motion have confirmed this agreement to about half of 1 percent. Oneof the remarkable properties of general relativity is that it satisfies EEP forall types of bodies.
If the Nordtvedt effect were to occur, then the Earth andMoon would be attracted by the Sun with slightly different accelerations,resulting in a small perturbation in the lunar orbit that could be detected bylunar laser ranging, a technique of measuring the distance to the Moon usinglaser pulses reflected from arrays of mirrors deposited there by Apolloastronauts. One of the first astronomical applications of general relativity wasin the area of cosmology. The theory predicts that the universe could beexpanding 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 knownas the steady state theory, based on the concept of the continuous creation ofmatter 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 relativitytheory, thus also further supporting the theory. Perhaps the most critical pieceof evidence was the discovery, in 1965, of what is called background radiation. This “sea” of electromagnetic radiation fills the universe at atemperature of about 2. 7 K (2.
7 degrees C above absolute zero). Backgroundradiation had been proposed by general relativity as the remaining trace of anearly, hot phase of the universe following the big bang. The observed cosmicabundance of helium (20 to 30 percent by weight) is also a required result ofthe big-bang conditions predicted by relativity theory. In addition, generalrelativity has suggested various kinds of celestial phenomena that could exist,including neutron stars, black holes, gravitational lenses, and gravitationalwaves.
According to relativistic theory, neutron stars would be small butextremely dense stellar bodies. A neutron star with a mass equal to that of theSun, for example, would have a radius of only 10 km (6 mi). Stars of this naturehave been so compressed by gravitational forces that their density is comparableto densities within the nuclei of atoms, and they are composed primarily ofneutrons. Such stars are thought to occur as a by-product of violent celestialevents such as supernovae and other gravitational implosions of stars.
Sinceneutron stars were first proposed in the 1930s, numerous celestial objects thatexhibit characteristics of this sort have been identified. In 1967 the first ofmany objects now called pulsars was also detected. These stars, which emit rapidregular pulses of radiation, are now taken to be rapidly spinning neutron stars,with the pulse period represent the period of rotation. Black holes are amongthe most exotic of the predictions of general relativity, although the conceptitself dates from long before the 20th century.
These theorized objects arecelestial bodies with so strong a gravitational field that no particles orradiation can escape from them, not even light–hence the name. Black holes mostlikely would be produced by the implosions of extremely massive stars, and theycould continue to grow as other material entered their field of attraction. Sometheorists have speculated that supermassive black holes may exist at the centersof some clusters of stars and of some galaxies, including our own. While theexistence of such black holes has not been proven beyond all doubt, evidence fortheir 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 ismoving, and that we really have no way of know just how fast. This theory, alongwith complex equations developed many years ago, helped to explain certain longmisunderstood things about planets and their movements. But the same thinkingabout very large objects, in motion, like stars, planets, solar sysems, simplydoes not work accurately when you look at microscopic things, like atoms. Too,since the development of the theory of relativity, we have made manytechnological advances that have allowed us to make accurate measurements, andto basically confirm the theory is correct.
