Transcript Albert Einstein

During the late 1800’s, the field of science
desperately needed a new theory to revise
the old Newtonian-based physics.
The laws of Newtonian principles were beginning
to show problems; for example, the
precession of Mercury’s orbit could not be
completely accounted for.
Einstein revolutionized all aspects of science and
modern thought through his theories of
general and special relativity and idea of
equivalence.
Albert Einstein was taken seriously after rigorous
testing of his theories. One example is the
famous advance of Mercury's perihelion.
Because Newton's law did not correctly
predict this, Einstein's theory gained
approval for a new revolution in science.
Furthermore, the eclipse experiment of 1919
helped to prove his bending of light theory.
These proofs helped him to gain wider
acceptance of his theories. Einstein recieved
the a Nobel Prize in 1921, not for his
research on relativity, but for his 1905 work
on the photoelectric effect.
• Time’s “Man of the
Century” for 1900s
• Helped defrock Newton’s
Laws as absolute
– See also quantum physics
• Changed our entire
concept of space and time
• Key figure in the nuclear
age
March 14, 1879:
Albert Einstein was born in
Ulm, Germany
Einstein saw a
wonder when he
was four or five
years old: a
magnetic compass.
The needle's
northward swing,
guided by an
invisible force,
impressed him.
The compass
convinced him that
there had to be
"something behind
things, something
deeply hidden."
Einstein knew, from then
on, that he wanted to
teach math and
Science at a University
someday.
The problem was, he
wasn’t a very good
test-taker and could
not get a job at a
University because of
it.
Rumor has it that he had
even failed a Math
test, but some people
question that because
of the way grades
were assigned back
then.
Albert Einstein
develops his
Special Theory of
Relativity.
He did this while
working as a Patent
Clerk in Germany.
He wasn’t really even
a scientist at the
time.
Relative to who is
watching, space and
time are transformed
near the speed of light:
distances appear to
stretch; and clocks tick
more slowly.
Einstein’s theory meant
that Sir Isaac Newton
was wrong.
Space and time are not
absolute - and the
universe we live in is
not actually the one
Newton "discovered.”
Einstein
His work anchors the
most shocking idea in
twentieth century
science: we live in a
universe built out of
tiny bits of energy
and matter.
Next, in April and May,
Einstein publishes
two papers.
In one he invents a new
method of counting
and determining the
size of the atoms or
molecules in a given
space.
In the other he explains
the phenomenon of
Brownian motion.
The net result is a proof
that atoms actually
exist - still an issue at
that time.
And then, in June, Einstein completes special
relativity - which adds a twist to the story:
And of course, Einstein isn't finished. Later in 1905
comes the most famous relationship in physics…
The energy content of a body is equal to the mass of
the body times the speed of light squared.
At first, even Einstein does not understand the full
implications of his formula.
In 1907, Einstein
begins to apply the
laws of gravity to his
Special Theory of
Relativity.
In 1910, Einstein
answered a basic
question: "Why is the
sky blue?" He solved
the problem by
looking at the effect
of the scattering of
light by individual
molecules in the
atmosphere.
Einstein completes his
General Theory of
Relativity.
Einstein challenged the
way the world thought
about gravity – and Sir
Isaac Newton himself by describing gravity as
the warping of spacetime, not a force acting
at a distance.
A solar eclipse proves
Einstein right, and he
becomes an overnight
celebrity.
An experiment had
confirmed that light
rays from the sun were
deflected by the gravity
of the sun in just the
amount Einstein had
predicted in his theory
of gravity, General
Relativity.
• During the 1920's
Edwin Hubble
and Milton
Humason
photographed the
spectra of many
galaxies with the
100 inch
telescope at
Mount Wilson.
Comparison of laboratory to blue-shifted object
Comparison of laboratory to red-shifted object
Hubble and recession
of galaxies:
Further away,Greater redshift !
Hubble guessed their
distances by size and
brightness -underestimated
by factor 10!
Like raisins in rising raisin cake,
galaxies move away from each
other in our expanding universe.
Wavelength is shorter when approaching
Stationary waves
Wavelength is longer when receding
Cepheid variable stars are pulsating stars, named after
the brightest member of the class, Delta Cephei.
Cepheids are brightest when they are hottest, close to
the minimum size. Since all Cepheids are about the
same temperature, the size of a Cepheid determines its
luminosity.
Thus there is a period-brightness relationship for
Cepheids.
Since it is easy to measure the period of a variable star
and they can be very bright, Cepheids are wonderful for
determining distances to galaxies!
“Instability strip” -region in H-R
diagram with large,
bright stars
Outer regions of star
are unstable and tend
to pulsate
Star expands and
contracts, getting
brighter and fainter
Henrietta Leavitt studied variable stars that were all at
the same distance (in the LMC or SMC) and found that
their pulsation periods were related to their brightnesses
Polaris
(The North Star)
is not constant, it
is a Cepheid
variable!
Cepheid Variable Stars
as distance indicators:
“standard candle”
Vital discovery by
Henrietta Leavitt
(1912)
Andromeda found to be far outside Milky
Way – another “island universe” : galaxy!
Edwin Hubble in 1924
identified Cepheids in
Andromeda (M33) 
showed they were far
outside of Milky Way!
His first big discovery.
Next was expansion of
the universe – wow!
Hubble using new
100” Hooker telescope
at Mt. Wilson (above LA)
• Using the Doppler effect, Hubble
calculated the velocity at which each
galaxy is receding from us.
• Using the period and brightness of
Cepheid variables in distant galaxies,
Hubble estimated to distances to each of
the galaxies.
• Hubble noticed that there was a linear
relationship between the recessional
velocity and the distance to the galaxies.
• This relationship is know as Hubble’s Law:
v = Ho d
recessional velocity = Hubble’s Constant  Distance
• Ho is known as the Hubble constant and is
about 75km/s/Mpc.
• This means that a galaxy that is 1
megaparsec from Earth will be moving
away from us at a speed of 75km/s.
v = Ho * d
Ho is called the Hubble constant. It is generally
believed to be around 65 km/sec/Mpc…plus or
minus about 10 km/sec/Mpc.
Note: The further away you are, the faster you are
moving!
Distance = Velocity/(Hubble constant)
To get a rough idea of how far away a very distant object is from Earth,
all we need to know is the object's velocity.
The velocity is relatively easy for us to measure using the Doppler effect,
or Doppler shift.
v = Ho d = cz
where
v = velocity from spectral line measurements
d = distance to object
Ho = Hubble constant in km s-1 Mpc -1
z is the redshift
Space between
the galaxies expands
while galaxies stay
the same size
v = H0d and d =vt
Solving for t, we find the age of the Universe is:
t ~ 1/H0
If H0 = 65 km/s/Mpc, then the age of the Universe is
~ 16 x 109 yr or 16 billion years
The greatest mistake of Einstein’s career
might not have been such a mistake after
all. A new growing movement states the
Universe might not end in a Big Crunch,
but rather, the force of antigravity is now
being used to explain why the expansion
of the universe is not slowing down. And
now this repulsive force is instantly
becoming the biggest mystery in science.
Einstein begins pursuing his idea
of a unifying theory that ties
everything in the universe
together.
Einstein continued in his dying
days, to figure out a single
central theory that explained
everything in the universe.
An extension of his work has
become known as String
Theory, which says that
everything in the universe is
made up of tiny strings of
energy – nothing, really!
1933: Einstein and his wife,
Elsa, escape Nazi
Germany and set sail for
the United States.
1939: World War II begins.
Einstein writes a now
famous letter to
President Franklin D.
Roosevelt urging nuclear
research and warning
him of Germany’s
building of an atomic
bomb
This is a picture of his last blackboard.
"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."
"Anyone who has never made a mistake
has never tried anything new."
"If A equals success, then the formula is:
A=X+Y+Z. X is work. Y is play. Z is
keep your mouth shut."
1. The Laws of Physics are the same for all
observers, no matter their motion, as
long as they are not accelerated.
(Galilean inertia, essentially)
2. The speed of light is constant and is the
same for all observers independent of
their motion relative to the light source.
Galilean Relativity at low relative speeds
• Showed Newton didn’t know everything.
– Together with quantum physics, threw a
wrench into determinism
• Forever changed the way we think about
space and time.
– Moving watches don’t stay synchronized
– Gravity not really a force but curvature
• No action at a distance after all?
• Nuclear energy/weapons
The Special Theory of Relativity (1905)
• Einstein elevated the
Michelson-Morley null result
into a fundamental principle
of nature:
The speed of light is constant,
independent of the motion of
the source or the observer.
This required him to treat “space”
and “time” as a single entity:
Space
Time
Spacetime
Albert Einstein (1879-1955)
The General Theory of Relativity (1916)
• Extension of special
relativity to include
gravity.
• Matter warps spacetime;
falling object follow
straight lines in curved, 4dimensional spacetime.
• “Space tells matter how
to move; matter tells
space how to curve.”
General Relativity and the Universe
• Einstein attempted to find solutions to his
equations that described the complete
spacetime “shape” of the universe.
• Much to his consternation, he discovered that he
could not find static solutions – they all
described a universe that was either expanding
or contracting.
• Since this was clearly nonsense, Einstein
modified his equations, adding a term that
corresponded to the energy of the vacuum. He
called this term the cosmological constant.