time travel

1. Power point presentation
By
ROHIT KUMAR KOUNDAL
Student in physics major
T.J.C.M Govt. Degree College , Sujanpur Tihra
E-mail : koundalrohitkumar@gmail.com

3. “The laws of physics are the
same in all inertial frames."
“The speed of light is
constant in all frames."
The Postulates of the Special Theory of Relativity
Special Theory of Relativity
was developed by
Albert Einstein in 1905
Albert Einstein (1879-
1955 )
Born: Germany

4. Given two frames, one moving at
constant velocity with respect to
the other, how do we transform
the coordinates?
The traditional answer would have
been:
z
y
x x'
y'
z' v
Galilean
Transformations
Galileo
Galilei
(1564 -1642 )
Born : Italy

5. Lorentz transformations
Hendrik Antoon Lorentz
Nationality : Netherlands
(1853 -1928)

6. Values of g - chart
v g =1/(1-v2/c2)
0.01 c 1.00005
0.1 c 1.005
0.5c 1.15
0.6c 1.25
0.8c 1.67
0.9c 2.29
0.99c 7.07
1.00c 
Larger than c Imaginary number

7. 1
1 – v2/c2
g =
v=c
x x
x
x
x

Never-never
land

8.  Lorentz and Fitzgerald never denied the existence of ether. They
postulated an independent effect ("contraction") that masked its
visible consequences.
 However Poincare, in
1900, asked the
question:
"Does the ether
really exist?"
Jules Henri Poincaré
(1854–1912)
Residence France
Nationality French

9. Michelson-Morley
No aether wind detected: 1907 Nobel Prize
Morley (1838-1923)

11. Michelson – Morley Expt

12. Derivation of expression for fringe shift
• The time taken by the light ray to travel the longitudinal path t1=
• The time taken by the light ray to travel the Transverse path t2 =
• Time difference = t1- t2 =
• If the apparatus is rotated through 900 , then it will become t2- t1
• Time interval between original position and after rotated through 900
= = 2(t1- t2) =
• Fringe shift =
• Where v = 3104 m/s, c = 3108 m/s, d = 11 m, and
 = 600 nm = 60010-9 m
• Hence 0.4 of fringe.
• The apparatus was able to measure a fringe shift of 0.01 of fringe. But
Michelson and Morley could not observe any fringe shift
experimentally. This is the negative or null result . Hence they
concluded that there is no ether medium.
2
2
2
1
d v
c c
 

 
 
2
2
2
1
2
d v
c c
 

 
 
2
3
dv
c
T

2
3
2dv
c
2
2
2
c T dv
n
c
 

 = =
n
 =

14. Michelson Interferometer

15. Length contraction
man on
rocket
Time = t0 =t/g
Length = vt0
L0
v
time=t
L0 = vt
=vt/g =L0/g

16. L = L0/g
g >1  L < L0
Length measured when
object is at rest
V=0.1c
V=0.86c
V=0.99c
V=0.9999c

17. George Francis
FitzGerald
(1851-1901)
Born : Ireland

18. Moving clocks run slower
t
t0
t= g t0
t= t0
1
1 – v2/c2
v
g >1  t > t0

19. Relativistic mass increase
m0 = mass of an object when it
is at rest  “rest mass”
m = g m0
mass of a moving
object increases
by the g factor
as vc, m
as an object moves
faster, it gets
harder & harder
to accelerate
g
v=c

20. Albert Einstein"
"The mass of a
body is a measure
of its energy
content"
“A theory can be proved by experiment; but
no path leads from experiment to the birth

21. Moving clocks run slow
Moving objects appear shorter
Moving object’s mass increases
summary

22. Thank you all