Einstein’s Warped Universe Ted Jacobson Department of Physics, University of Maryland.
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Transcript of Einstein’s Warped Universe Ted Jacobson Department of Physics, University of Maryland.
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Einstein’s Warped Universe
Ted Jacobson
Department of Physics, University of
Maryland
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"A practical profession is a salvation for a man of my type; an academic career compels a young man to scientific production, and only strong
characters can resist the temptation of superficial analysis."
Image © The Albert Einstein Archives, The Jewish National & University Library,The Hebrew University of Jerusalem, Israel.
Einstein in the Bern patent office, 1905
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Special relativity (1905) time, space, and mass (E=mc2)
General relativity (1915)
• gravity and inertia • warped time and space
Einstein’s theories of relativity
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“…the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest.”
“…light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body.”
“So we see that we cannot attach any absolute signification to the concept of simultaneity...”
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Spacetime
"Henceforth, space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality”
H. Minkowski, 1908
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timelikelightlike
spacelike
PAST
FUTURE
ELSEWHERE
ELSEWHERE
like
like
The Light ConeOne space dimensionnot included
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The twin “paradox”
25 years
25 years
24 light-years
7 years
7 years
SPACE-LIKE
TIME-LIKE
Time elapsed
between two events
depends on the path
in spacetime,
and is LONGEST
on the straight path.
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No time passes along a light ray!
25 years
25 years
25 light-years
0 years
0 years
SPACE-LIKE
TIME-LIKE
Elapsed time LONGEST
on the straight path
in spacetime.
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Spatial distance
4 miles
4 miles
3 miles
5 miles
5 milesDistance elapsed
between two points
depends on the path
in space,
and is SHORTEST
on the straight path.
(confusingly OPPOSITE to the case with time)
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Gravity
Universal attraction
of two masses.
Interpreted by Newton as
a “force” that explains both
the falling of an apple
and the orbit of the moon.
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Composite photo from NASA/ESA Cassini spacecraft
Gravity
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“I was sitting in the patent office in Bern when all of a sudden a thought occurred to me: if a person falls freely, he won’t feel his own weight. I was startled. This simple thought made a deep impression on me…”
“Then there occurred to me the happiest thought of my life…” “The gravitational field has only a relative existence …”
“Gravity cannot be held responsible for people falling in love."
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Parabolic flightallows long free-fall
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Morag Wightman, choreographer and performance artist
Free-fall: straight line in spacetime
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Gravity is curvature of spacetime
Spatial curvature analogy:
Initially parallel lines don’t stay parallel
appleearth
Spacetime
time
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apple
earthA
B Apple free-fall is the straightest path in spacetime between A & B,and the path of longest time.
Time runs slower lower down!
How much slower? One billionth of a second per year per footat the earth’s surface (g/c2).
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Spatial Analogy: straight line on a curved earth
Mercator map: rhumb lines in blue and green; part of a great circle in red
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Gravity bends light
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Einstein ring image of a galaxy
(Hubble space telescope)
Foreground“lens”galaxy
backgroundgalaxy
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Multiple images of one galaxy
Lensed by a clusterof galaxies
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(Image by Brian McLeod, Harvard-Smithsonian Center for Astrophysics.)
If a black hole with the mass of Saturn (apparent diameter 5 yds) floated by…
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Black Holes
Collapse to a black hole
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View towards the center of the Milky Way galaxy
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Stars orbit a giant black holeat the center of our galaxy
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From Black Holes and Time Warps, by Kip S. Thorne
A spinning black hole drags empty space around, like a tornado drags the air
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Expansion of the Universe
closed or open?
flat or curved?
expand forever?
origin?
beginning of time?
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Sprouting Universes?
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Black hole singularity:an end of
time?
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Fate of a black hole singularity?
time endsfractured time continues
plump babyUniverse born
The End
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A baby universe is born…
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Black Holes and Time Warps, Kip S. Thorne.A book for the general reader about the physics and astrophysics, with a historical and personal view on the scientists involved.
General Relativity from A to B, R. Geroch.An explication of the fundamental concepts with almost no math.
Flat and Curved Space-Times, G.F.R. Ellis and R.M. Williams. A textbook introducing the fundamentals to students with no more than basic high school algebra, trigonometry, and the concept of a function.
http://www.aip.org/history/einstein/American Institute of Physics, Einstein web site
http://einsteinyear.org/facts/Institute of Physcs, Einstein web site
Further reading