Einstein’s Warped Universe

Ted Jacobson

Department of Physics, University of

Maryland

"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

Special relativity (1905) time, space, and mass (E=mc2)

General relativity (1915)

• gravity and inertia • warped time and space

Einstein’s theories of relativity

“…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...”

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

timelikelightlike

spacelike

PAST

FUTURE

ELSEWHERE

ELSEWHERE

like

like

The Light ConeOne space dimensionnot included

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.

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.

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)

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.

Composite photo from NASA/ESA Cassini spacecraft

Gravity

“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."

Parabolic flightallows long free-fall

Morag Wightman, choreographer and performance artist

Free-fall: straight line in spacetime

Gravity is curvature of spacetime

Spatial curvature analogy:

Initially parallel lines don’t stay parallel

appleearth

Spacetime

time

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).

Spatial Analogy: straight line on a curved earth

Mercator map: rhumb lines in blue and green; part of a great circle in red

Gravity bends light

Einstein ring image of a galaxy

(Hubble space telescope)

Foreground“lens”galaxy

backgroundgalaxy

Multiple images of one galaxy

Lensed by a clusterof galaxies

(Image by Brian McLeod, Harvard-Smithsonian Center for Astrophysics.)

If a black hole with the mass of Saturn (apparent diameter 5 yds) floated by…

Black Holes

Collapse to a black hole

View towards the center of the Milky Way galaxy

Stars orbit a giant black holeat the center of our galaxy

From Black Holes and Time Warps, by Kip S. Thorne

A spinning black hole drags empty space around, like a tornado drags the air

Expansion of the Universe

closed or open?

flat or curved?

expand forever?

origin?

beginning of time?

Sprouting Universes?

Black hole singularity:an end of

time?

Fate of a black hole singularity?

time endsfractured time continues

plump babyUniverse born

The End

A baby universe is born…

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