RelativityTheory

By:-Albert Einstein

About Albert Einstein

He was Born on :-

14 March 1879

At :-Ulm, Kingdom of Württemberg , German Empire

And died on:-

18 April 1955 (aged 76)

At :-Princeton, New Jersey, United States

He resided at:-Germany, Italy, Switzerland, Austria, Belgium and United States during his lifetime

Citizenship:-Kingdom of Württemberg (1879-1896)Stateless (1896–1901)Switzerland (1901–1955)Austrian of the Austro-Hungarian Empire (1911–1912)German Empire (1914–1918)Weimar Republic (1919–1933)United States (1940–1955)

Spouse:-

Mileva Marić (1903–1919)Elsa Löwenthal (1919–1936)

Children:-Lieserl (1902–1903)Hans Albert (1904–1973)Eduard Tete (1910–1965)

SpecialRelativity

Einstein's theory of Special Relativity is based on two postulates:Relativity Principle: The laws of nature are the same in all inertial reference framesThe speed of light in a vacuum is the same in all inertial frames

•

• When we move with high speeds clocks run slow, and meter sticks are length contracted. In both cases the amount of the time dilation or length contraction is specified by the boost factor Gamma. The boost factor for an object moving with velocity v is given by the formula

• Gamma (𝛾) =1

1−𝑣2

𝑐2

The concept of clocks working slower and length of objects becoming shorter

are termed as time dilation and length contraction respectively

• An object is longest in its own rest frame, while clocks at rest tick most rapidly, i.e. show the shortest elapsed time interval between two events. As seen in a frame in which they are moving , objects are contracted and clocks tick more slowly. In their own rest frame, all lengths and clocks seem normal no matter how fast another observer sees them to move.

• In normal Galilean velocity addition formula, vtotal = v1 + v2 but here the formula to add velocities of objects will be:-

relativistic velocity addition formula which

is:-

𝑣𝑡𝑜𝑡𝑎𝑙 =(𝑣1 + 𝑣2)

(1 +𝑣1𝑣2𝑐2

)

So if we use regular Galilean formula

then we will always get absurd results

• The prime example of a situation governed by special relativity is a region far, far away in the depths of space, far away from all stars and planets (and their gravitational influence). Imagine that, in this dark void, there are freely moving space stations, drifting along without any acceleration or rotation. On each of these stations sits an observer, with his own clocks and his own measuring rods, measuring times and distances. In addition, each such observer has a fully equipped physics lab on board, where he or she can perform a variety of experiments to explore the laws of physics. This is the kind of observer Einstein talks about, an observer in a free, non accelerated frame of reference. Such frames of reference (and such observers) are commonly called inertial frames of reference

If you think about space stations drifting along in empty space, some statements that are surely relative spring to mind right away: statements

about velocities. Imagine that, from the point of view of observer A sitting on the upper deck of his

or own space station, the station of observer B passes by at considerable speed:

The principle of relativity

• But from the point of view of observer B, his own station is at rest. For him, it is observer A's station that is moving:

• So who is moving and who is at rest? The answer depends on which observer you ask. Whether or not a space station moves - and with what speed - is an example of an observer-dependent, relative statement.

Relativity of space and time

• Einstein's theory, simultaneity is a relative concept. Imagine that there are two events which an observer in space station A judges to be simultaneous - say, the explosion of a firecracker at one point in space and an alarm clock going off a few miles away. For an observer in space station B, which is moving relative to A, this statement will not necessarily be true: In general, such an observer will come to the conclusion that one of the events happened earlier than the other.

• Similarly, temporal duration depends on the observer. This relativistic effect is called time dilation. Summarized briefly: Moving clocks are slower than stationary ones. A bit more precisely: An observer on station A measures time using his on-board clock. Station B, passing A at high speed, has an exact copy of A's clock on board. Yet, from the point of view of A, the clock in station B runs more slowly than his own. A down-to-earth version of this effect can be tested with the help of elementary particles such as those particles accelerated inside the "proton synchrotron" of the European research centre CERN.

Space-time• In special relativity, as was mentioned briefly, simultaneity is

relative, and so are time and space. Observers moving relative to one another come to different conclusions about which events happen simultaneously ("at the same time"). They agree only about what events there are, not about where or when these events take place. Space-time, the totality of all events, is absolute. But there are different ways to slice that collection of events into snapshots of simultaneity. When viewed in succession, these snapshots show how, with time, changes take place in space. Different observers, looking at different successions of snapshots, come to different conclusions about which events are simultaneous. Space-time is absolute, space and time are not.

E=mc²• The relativistic increase of mass happens in a

way that makes it impossible to accelerate an object to light speed: The faster the object already is, the more difficult any further acceleration becomes. The closer the object's speed is to light speed, the greater the increase in inertial mass; to reach light speed exactly would require an infinitely strong force acting on the body. This enforces special relativity's speed limit: No material object can be accelerated to light speed.

• The increase in inertial mass is part of a more general phenomenon, the relativistic equivalence of mass and energy: If one adds energy to a body, one automatically increases its mass; if one takes energy away from it, one decreases its mass. In the case of acceleration, the object in question gains kinetic energy ("movement energy"), and this increase in energy automatically means an increase in mass.

On the other hand, even an object at rest turns out to have a certain amount of energy. Energy and (inertial) mass are inextricably linked by Einstein's famous formula. Every body of mass m will necessarily have a total energy

E=mc²

Conclusion• Special relativity is more than just another

branch of physics. It is a framework into which other physical laws can be embedded: All physical laws in which space and time play a role naturally depend on the properties of space and time, and those are governed by special relativity. Indeed, relativistic generalizations have been found for almost all laws of physics that predate special relativity.

General Relativity

According to this theory Massive objects cause a distortion in space

time.Which is given by the equation:-

𝐺𝜇𝑣 + ∆𝑔𝜇𝑣 =8𝜋𝐺

𝑐4𝑇𝜇𝑣

• With the general theory of relativity, in which Einstein managed to reconcile relativity and gravitation, he had to discard the traditional physics worldview, which saw space as merely a stage on which the events of the world unfold. Instead, space-time is a dynamic entity, which is distorted by any matter that is contained in it, and which in turn tells that matter how to move and evolve. This interaction between spacetime and matter is described by Einstein's geometric, relativistic theory of gravity.

• The consequences of that theory are spectacular. For instance, general relativity predicts that even light is deflected by gravity -a prediction that has been confirmed by numerous astronomical observations

Einstein's geometric gravity

In Einstein's theory of

general relativity, gravity is a

distortion of space-time.

Particles follow the straightest

possible paths in that space-time. But because space-time is now distorted, even on those straightest paths, particles accelerate as if they were under the influence of what Newton called the gravitational force.

Major application of General relativity

• Newtonian physics predict an elliptical orbit of a planet, with the sun in one of the focal points..

• For the same situation, Einstein's theory predicts a slightly different orbit: not an ellipse, but a kind of rosette. As Mercury orbits around the sun, the two points of each orbit closest to the sun and furthest away from it (in astronomical lingo: perihelion and aphelion) should ever-so-slightly shift from one orbit to the next. The following figure shows an exaggerated version of this movement:

• In the solar system, where there's more than one planet orbiting the sun, the situation is a bit more complicated. There, the mutual gravitational pull of the planets on each other leads to a slight shift of perihelion and aphelion points, even without Einstein's results. However for Mercury, where the relativistic effect should be strongest, the shift that we observe is slightly larger than expected. Even when the influence of all the other planets taken into account, a slight extra contribution is left over. A simple calculation in general relativity predicts exactly that tiny additional shift.

The light side of gravity• For the propagation of light, Einstein's theory makes

a clear prediction: Light is deflected by gravity. Just as test particles move on the straightest-possible lines in curved space-time (i.e. on space-time geodesics), so does light.

• The most basic example: Light rays passing a massive body are bent towards that mass. This effect increases for light rays that pass the body at smaller and smaller distances from it

• The first measurement of this relativistic effect was made by British astronomers in 1919. They used the fact that light deflection changes astronomical observations. The "location of a star in the night sky" is simply short-hand for "the direction from which that star's light reaches us". Starlight that passes close to the sun before reaching us gets deflected, as sketched in the figure above (but by a much smaller amount than is shown there). This starlight will thus reach us from a slightly different direction than when the sun is in some different region of the sky. Accordingly, the star's position in the night sky is shifted slightly.

Conclusion

• Einstein's theory of gravity led physicists to a variety of new models and phenomena.

Blackholes

Formation and properties• When massive stars explode in a supernova,

the collapsing central

• region will generically

• have so much mass that

• even neutron matter

• cannot halt the collapse.

• The collapse continues,

• and when this happens, a black hole is born

The black hole itself isn't a solid object, but rather a region of space

with very special

Properties : Matter or light

can enter that region from

the outside,but nothing

that has entered can ever return. The border separating this region from the rest of the world is called the event horizon or, more simply, the horizon of the black hole.

As the name implies, an outside observer will receive no light from a black hole.

However, if you could come close enough,

you could notice how its presence deflects the light of far-away objects behind it.

The light of the stars and galaxies close to the center of the image is deflected by the black hole's gravitational influence. The most obvious effect is that the light from one of the objects is distorted to form a ring around the black hole. This phenomenon, called an "Einstein ring", only occurs when the object and the black hole are precisely aligned with the observer.

Conclusion• Relativistic physics is necessary to

fully understand the most energetic phenomena in the universe -from supernova explosions of stars to the driving force that makes some active galactic nuclei the brightest objects in the universe.