relative time
DESCRIPTION
this presentation is about how time really works and is there is a distinstion between what we call present past and futureTRANSCRIPT
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Relative time : What its all about?
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content
• Time
• Newton's and Einstein's view of time
• Spacetime
• Illusion of past present and future
• Time and gravity
• Arrow of time
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TIME
• Time, as a physical quantity, reminds us of duration, measuring instruments – sand clocks, watches, atomic clocks.
• Time is a thing that everybody knows until you ask him to tell about it how it works etc
• One way to know about time is measure it using some repetitive process
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Very first clock
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Emit light for 9192631770 times in 1second
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Different clocks
• Clocks tell us what time is but haven't been able to tell us what time itself is?
• Rise of train travel played key role for one of the most startling discovery about time
• Earlier each town has its own time
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Newton`s view about time
• I don't define time space motion as are well known to all absolute space and time in its nature without reference to anything external remains always similar and unmovable
- Naturalis Principia by Newton
• Time exist in and of itself flow equally without reference of anything external
- Principia
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What Is Absolute Space?
• Infinite, unchanging, 3-dimensional “box”
• Existing as a substance independently of material objects and the spatial relationsamong them.
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Street and avenue are making some angle and rest both are same and equally valid
There is nothing like absolute street and absolute avenue but still absolute space
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Einstein`s view
• Time is not universal its individual
• Velocity of light is constant with respect to anything and everything
• Neither time nor space is absolute but spacetime is absolute
• Motion in space effect motion through time and vice versa
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Speed of light is constant
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Rest and motion
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Space-time
• Spacetimes are the arenas in which all physical events take place—an event is a point in spacetime specified by its time and place
• A region of space consider over the interval of time is region of spacetime
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Two dimensional space-time diagram, i.e 3-D
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Spacetime diagrams are like traditional position-time diagrams BUT time goes vertically by convention.
So as time passes things are ‘copied up’:
space
tim
e
Same point in space at different times
Standing Still
1)
2)
3)
space
tim
e
Running
Different points in space at different times
1)
2)
3)
space
tim
e
1)
2)
3) The path in spacetime is called a “world-line”
space
tim
e1)
2)
3)
Notice that for a moving observer the world-line is slanted.
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• The combined speed of any object`s motion through space and its motion through is always precisely equal to speed of light
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Gunfight viewed by observer on train
Bang! Bang
!
He sees both shotsfired simultaneously
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Viewed by a stationary observer at station
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Viewed by a stationary observer at station
Bang! Bang
!
He sees cowboy shoot1st & cowgirl shoot later
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Viewed by a stationary observer at station
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Viewed by a stationary observer at station
Bang!Bang
!
He sees cowgirl shoot1st & cowboy shoot later
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Time depends of state of motion of the observer!!
Events that occur simultaneously according to one observer can occur at different times for other observers
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\View by observer at rest and moving
absolute space-time
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Every moment on the earth that ever happen and will ever happen on the universe will all exist in this space time
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Space-time Loaf of bread
• Einstein viewed space time as loaf of bread
• Each observer cut its slice in its own way
• Two observer having some relative velocity with cut space time bread at some angle small to measure
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Now-anything happening right now
Past
Something our experience tell had happened
Future
Things that are yet to happen
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People like us,
who believe in
physics, know that
the distinction
between past,
present, and
future is only a
stubbornly
persistent illusion.
-Albert Einstein
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Time Dilation
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Twin paradox
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Time and Gravity• Accelerated motion and gravity are same side
of a coin
• Suitably changing your motion you can avoid feeling of sensation due to gravity
• Some guy falling freely will not feel gravity
• Suitable change in motion can create gravity
• Falling guy is really a frame to see accelerated motion
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Rubber Mattress Example
• Imagine 2 bowling balls on a mattress, on earth
• As they roll around on the mattress, they make dimples in its surface
• If they get close to each other, they roll into each other’s dimples
– they are “attracted” to each other
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Mass tells space-time how to curve
Space tells mass how to move
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Space & time are bent, or curved, by matter.
This is gravity. Planets, moons and baseballs go
“as straight as they can.”
www.unmuseum.org
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• All clocks run slower in a strong gravitational field than they do in a weaker field.
• Time ticks slower near the earth than that in empty space
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Time and Experience
Eggs break, ice cubes melt, stars emit radiation, we record memories of the past. And it all happens in a consistent
“direction” (from the past to the future) throughout the universe:
The Arrow of Time.
One of the single most surprising things about the universe is that things change!!
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The Entropy Arrow
According to Boltzmann
Total Entropy always increases(The 2nd Law of Thermodynamics)
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The CPT Theorem
CPT = “Charge-Parity-Time”If the charge of all particles in universe were changed to the opposite charge (so that all particles change to their antiparticles); & at the same time, all were reflected in a mirror; & at the same time, time started to run backwards:
This new world would be indistinguishable from the old world.
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• For law of physics to tell anything we need initial condition
• But for time initial condition is big bang, deepest mystery yet to be uncovered
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"Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. THAT'S relativity.”
-Albert Einstein
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Thanks !!!