Hi guys!!! This is a presentation on the time travel.Many of us don't know about time travel, so here you can find the complete information regarding the time travel. If you guys have any doubts then feel free to ask me in the comments section. THANK YOU!!!!

1. TIME TRAVEL
By
G.Sai Kiran (318)
Mech-B1
SNIST

2. INTRODUCTION
 Time travel is the concept of movement
between certain points in time, analogous to
movement between different points
in space by an object or a person, typically
using a hypothetical device known as a time
machine.

3.  It is uncertain if time travel to the past is
physically possible.
 Forward time travel, outside the usual sense
of the perception of time, is an extensively-
observed phenomenon and well-understood within
the framework of special relativity and general
relativity.

4. TIME TRAVEL IN PHYSICS
 Time travel to the past is theoretically possible in certain
general relativity spacetime geometries that permit traveling
faster than the speed of light, such as cosmic strings,
transversable wormholes, and Alcubierre drive.

5. POSSIBILITIES OF TIME TRAVEL
 Travelling in time could be possible in the following
four ways
1. Wormholes
2. Cosmic string
3. Supermassive black hole
4. Travelling at the speed of light
……and time machine is what actually based
on above hypothesis

6.  WORMHOLES
 A wormhole (or Einstein–Rosen bridge) is a speculative
structure linking separate points in spacetime.
 A wormhole would allow an object to travel from one point to
another faster than the speed of light,
 Problem: No wormhole has ever
been discovered, and even if it was, it
would be far too small for scientists to
manipulate for the purposes of time
travel

7.  COSMIC STRINGS
 Described as one-dimensional "cracks in the universe" and
some of the strangest structures observed by cosmologists.
 The approach of two such strings parallel to each other, will
bend space-time so vigorously and in such a particular
configuration that [it] might make time travel possible .
 Problem: Again, cosmic
strings only exist only in
theory.

8.  SUPERMASSIVE BLACK HOLE
 A black hole is a region of spacetime exhibiting such strong
gravitational effects that nothing—not even particles and
electromagnetic radiation such as light—can escape from
inside it
 If a spaceship were to orbit a black hole, those on board
would only experience eight minutes of time for every 16-
minute orbit.
 Problem : It's a long way away and
it doesn't even take us very far into
the future

9.  TRAVELLING AT THE SPEED OF LIGHT
 We all know that the speed of light is 3x10^8 m/s.
 In Einstein's special theory of relativity, “time” as a universal
concept. Instead, time passes differently for different
observers, depending on the observers' motion and - more
importantly, speed.
"If you go fast, your clock runs slow
relative to people who are still’’
 Problem: According to the laws of physics, nothing can
travel as fast as the speed of light – let alone a spaceship.
Even the Large Hadron Collider, the strongest particle
accelerator in the word, can't make protons move that fast.

10. Time travel in fiction:Time travel themes in science fiction
and the media can generally be grouped into three
categories: immutable timeline; mutable timeline; and
alternate histories
History of the time travel concept: In Hindu mythology, the
Mahabharata mentions the story of King Raivata
Kakudmi, who travels to heaven to meet the creator
Brahma and is surprised to learn when he returns to
Earth that many ages have passed.

11.  No-communication theorem:
 When a signal is sent from one location and received
at another location, then as long as the signal is
moving at the speed of light or slower, the
mathematics of simultaneity in the theory of relativity
show that all reference frames agree that the
transmission-event happened before the reception-
event.
 When the signal travels faster than light, it is
received before it is sent, in all reference frames. The
signal could be said to have moved backward in time.
This hypothetical scenario is sometimes referred to
as a tachyonic antitelephone.

12. Absence of time travelers from the future
The absence of time travelers from the future is a variation
of the Fermi paradox. As the absence of extraterrestrial
visitors does not prove they do not exist, so does the
absence of time travelers not prove time travel is physically
impossible; it might be that time travel is physically possible
but is never developed or is cautiously used.

13. Several experiments have been carried out to try to
entice future humans, who might invent time travel
technology, to come back and demonstrate it to people of
the present time
Some versions of the many-worlds interpretation can be
used to suggest that future humans have traveled back
in time, but have traveled back to the meeting time and
place in a parallel universe.

14.  THE GRANDFATHER PARADOX
 The grandfather paradox is a paradox of time travel in which
inconsistencies emerge through changing the past.
 A common objection to the idea of traveling back in time is
put forth in the grandfather paradox or the argument of auto-
infanticide.
 If one were able to go back in time, inconsistencies and
contradictions would ensue if the time traveler were to
change anything; there is a contradiction if the past
becomes different from the way it is.

15. CONT…
 The paradox is commonly described with a person who
travels to the past and kills their own grandfather, prevents
the existence of their father or mother, and therefore their
own existence.
 Philosophers question whether these paradoxes make time
travel impossible.
 Some philosophers answer the paradoxes by arguing that it
might be the case that backward time travel could be
possible but that it would be impossible to actually change
the past in any way, an idea similar to the proposed Novikov
self-consistency principle in physics.

17. POSSIBLE OUTCOME
 Your time machine would break down, or your gun would
jam when you tried to kill your grandfather, or maybe you'd
have a sudden stroke and be paralyzed.
 Whatever it was, the universe would appear to resist the
creation of paradoxes, because the timelines where it
doesn't, you cease to exist.

18. SOLUTION
 This is for the case if only he created a time machine and no
one else knew

19. FINALLY….
I came to point that time travel to future is more probable than
to the past despite all these confusing paradoxes .
But we can’t ensure that time travel is impossible at the same
time
Surely possible

20. THANK
YOU