MISTERIOUS POWER

TIME

Space Dimensions

Only one coordinate is required to specify a point in one dimensional space

1D

Two coordinates are required to specify a point in two dimensional space

X

YThree coordinates are required to specify a point in three dimensional space

y

zX

Space and Time Dimension•It is impossible to imagine a four-dimensional space. •However, it is easy to draw diagrams of two-dimensional spaces

Time

Distance

sun Alpha Centauri

Light

Ray

LIGHT CONEMaxwell suggested that if a if a pulse of light is emitted at a particular time at a particular point in space, then as time goes on it will spread out as a sphere of light whose size and position are independent of the speed of the source.

SimilarlyThe light spreading out from an event forms a (three-dimensional) cone in (the four-dimensional)space-time. This cone is called the future light cone of the event. In the same way we can draw another cone,called the past light cone, which is the set of events from which a pulse of light is able to reach the given event

Future Light Cone of Event

Death of sun does not effect us immediately because we are not in the future light cone

Event when Sun dies

Earth

Sun

The Earth enters the future cone of death of sun after approximately 8 minutes

0 1 2 3 4 5 6 7 8 9 10

Minutes

ABSOLUTE SPACE

• Think of a train moving on a track and a person in the train sitting on the seat. If he bounces a ball and catch it. He will say that he threw the ball in a vertical path and if the height was h then the ball traveled 2h distance.

h

Train Compartment

An Observer on the platform would see the ball moving on such a path defined below

Another observer can also say that train is at rest and track is moving or earth is moving in reverse direction

Sun

Earth is also moving on a path round the sun and Sun is also moving on a round path in galaxy and Galaxy is also moving on a milky way. So there is no absolute space or position.

Earth

• There is no absolute space means that Space is not independent of universe. Similarly Time is also not absolute. But Pre-Einstein theorem did not say anything about absolute time.

• After 1915 Einstein made the revolutionary theorem Which was called “General Theory of Relativity”.

GENERAL THEORY OF RELATIVITY

• He said that space is not flat. It is curved by the distribution of mass and energy in it.

• Bodies like the earth are not made to move on curved orbits by a force called gravity.

• They follow the nearest thing to a straight path in a curved space.

• In general relativity, bodies always follow straight lines in four-dimensional space-time, but they nevertheless appear to us to move along curved paths in our three-dimensional space.

CURVED SPACE DUE TO MASS

The mass of the sun curves space-time in such a way that although the earth follows a straight path in four-dimensional space-time, it appears to us to move along a circular orbit in three-dimensional space.

• Another prediction of general relativity is that time should appear to slower near a massive body like the earth.

• Energy of light is directly promotional to the frequency of light.

• As light travels upward in the earth’s gravitational field, it loses energy, and so its frequency goes down. To someone high up, it would appear that everything down below was making longer to happen.

TEST OF CONCEPT

• This prediction was tested in 1962, using a pair of very accurate clocks mounted at the top and bottom of a water tower. The clock at the bottom, which was nearer the earth, was found to run slower, in exact agreement with general relativity.

SPACE-TIME

Series1

Time

x

y

Again taking the example of train and the ball

• A Person on the platform will say that ball is moving on a triangular path due to the motion of the train on a horizontal track.

The distance travelled by ball will be 2√(h2+t2).

h

• It can simply be said that distance 2h travelled by ball in the train is less than the travelled distance according to the outer observer.

• It is also clear that the time examined by the outer observer will be more that the time according to the observer in the train.

WITHOUT EINSTEIN’S GENERAL THEORY OF CURVED SPACE-TIME GPS SYSTEMS WOULD NOT WORK

• Clocks on satellites are used to “triangulate” locations. But the timing needs to be very accurate. (~ 20 ns)

• The satellites are at altitudes of ~ 20,000 kmwhere the gravitational field of the Earth is much lessthan at the surface of the Earth.

• Clocks run faster in this environment and this needs correcting for (+45000 ns/day).

• The satellites are also moving fast enough (14000 km/h) to need corrections from Special Relativity too (slow down by -7000 ns/day).

• GPS would fail after a few minutes without these corrections

Fantasy or Reality

TIME MACHINE

• Time can not exist without space and likewise space cannot exist without time. This relation is called space-time continuum.

• Traveling faster than the speed of light could open up the possibility of time travel to the past as well as to the future.

• The problem is that the speed of light is believed to be the highest speed at which something can travel.

• But time travel in the other direction is not as difficult, and the future may one day be a possible destination.

Most theories of time travel don't rely on machines. Instead, time travel will likely be done by way of natural phenomena that will transport us instantly from one point in time to another.

For time travel , Writers have developed so many theories and ideas with the help of imagination an scientific facts.

Three Phenomena , which we are not even sure exist, include:• Rotating black holes • Wormholes • Cosmic strings

BLACK HOLES

Black Holes have such strong gravitational field that even light cannot escape it might be possible to pass through them and exit out of a "white" hole. A white hole would have the reverse action of a black hole. These white holes would be our way to enter other times or other worlds.

WORM HOLES

In space, masses that place pressure on different parts of the universe could eventually come together to form a tunnel .A wormhole could be a type of tunnel-like structure existing in the universe that could be used for a time travel portal.

COSMIC STRINGS

• The latest is the String theory proposed by Princeton physicist J. Richard Gott in 1991.

• Scientist believes that string-like objects were formed in the early universe.

• These strings may line the entire length of the universe and are under immense pressure.

• These cosmic strings, which are thinner than an atom, would generate an enormous amount of gravitational pull on any objects that pass near them.

• Objects attached to a cosmic string could travel at incredible speeds, and because their gravitational force distorts space-time, they could be used for time travel.

• A spacecraft could be turned into a time machine by using the gravity produced by the two cosmic strings, or the string and black hole, to propel itself into the past. To do this, it would loop around the cosmic strings.

PROBLEM WITH TIME TRAVEL

• You could travel back to a time before you were born. The mere fact that you could exist in a time before you were born creates a paradox. If you were born in 1960, how could you exist in 1955?

• The most famous paradox is the grandfather paradox.

• What would happen if a time traveler went back and killed one of his or her ancestors before the traveler was born?

• If the person killed his or her grandfather, then how could that person be alive to go back and kill his or her grandfather?

THE ANSWER IS PARALLEL UNIVERSE

PARALLEL UNIVERSE• Theory regarding time travel brings up the idea of parallel universes, or

alternative histories.

• In the theory of parallel universes, you may have traveled to another universe, one that is similar to ours, but has a different succession of events.

• The idea here is that every action causes the creation of a new universe, and that there are an infinite number of universes that exist.

• When you killed your ancestor, you created a new universe that was identical to your own up until the time you changed the original succession of events.

Time is complicated but still very interesting. We still need so many years to understand the nature and time and one day we will be able to build time machine.

Thank you