Big Bang Timeline
10-45 sec (1032K)
10-35 sec (1027 K)
We have no physics to describe conditions at
these large energy densities and high temp.
Inflation begins, Quark-Antiquark Freezeout starts
(1,000,000,001 quarks to every 1,000,000,000 antiquark)
10-32 sec (1025 K)
Inflation ended, present-day observable Universe
was ~10 cm across
10-5 sec (1013 K)
Protons and neutrons form (no more free quarks)
1-15 min (108 K)
First elements (2H and 4He nuclei) form
380,000 yr (3000 K) Atoms form from nuclei and electrons
100 Myr (10 K)
Stars, galaxies, and planets begin to form. We
think the first stars ionized the Universe and
created heavy elements. Then star clusters and
dwarf galaxies formed from later generations of
stars. These star groups merged together to form
larger and larger galaxies.
10 Gyr (3 K)
Present Universe, expanding exponentially
1978 Nobel Prize in Physics: discovery of Cosmic
Background Radiation(CBR), the “echo” of the Big Bang
2011 Nobel Prize in Physics : The discovery of the
accelerating Universe
Saul Perlmutter
Brian Schmidt
Adam Riess
Modified from a presentation by:
Heidi Newberg
Rensselaer Polytechnic Institute
With Newtonian physics, it is impossible to predict the future of the Universe
Gravitational attraction should pull all the galaxies together
Einstein’s Field Equations
Stuff describing the
curvature of space(time),
otherwise thought of as
the Force of Gravity.
Stuff like
mass and
energy
Einstein’s Field Equations
is related to
Stuff describing the
curvature of space(time),
otherwise thought of as
the force of gravity.
Stuff like
mass and
energy
Is the Universe FLAT?
The density of the universe also determines
its geometry. If the density of the universe
exceeds the critical density, then the geometry
of space is closed and positively curved like
the surface of a sphere.
If the density of the universe is less than the
critical density, then the geometry of space is
open (infinite), and negatively curved like the
surface of a saddle.
If the density of the universe exactly equals
the critical density, then the geometry of the
universe is flat like a sheet of paper, and
infinite in extent.
http://map.gsfc.nasa.gov/media/990006/index.html
There is no static solution
If mass pulls the Universe together, we
cannot have a Universe that stays as
it is forever.
is related to
Einstein’s Field Equations
+ Λ
No static solution
is related to
Add a part that pushes the Universe apart
Λ = the cosmological constant
Doppler shift and inverse square law
Objects that are moving away have
longer wavelengths.
Objects that are farther away look
dimmer. If you know how bright a
source is, you can determine the
distance by how bright it seems.
Hubble’s Law
Around 1930, Hubble
showed that the speeds
with which galaxies
were moving away
from us is proportional
to their distance from
us.
(Km/S)
v = H0d,
where H0 is Hubble’s
constant
(Measured
from Doppler
shift of
spectral lines)
(Mpc)
(Measured from brightest stars method)
Expanding Universe
Expanding Universe
Supernova in IC4830
Image of galaxy with supernova
Image of galaxy
Supernovae get brighter and dimmer again within a few weeks.
(Km/S)
Hubble Diagram from Type Ia Supernovae
(Mpc)
Reiss, Press, and Kirschner (1996)
z



H0
c
d
The galaxies don’t really have a velocity.
is related to
Einstein’s Field Equations
is related to
+Λ
No static solution
is related to
----
This is the biggest blunder of my life.
Don’t need
a static
solution!!!
Low mass
Critical density
Lots of mass
Gnab Gib
Cosmological Parameters
Quantities that describe the Universe:
：
H0: The current rate the Universe is expanding
Ω0: The current mass density
Λ: The funny constant for pushing the Universe
apart
The State of cosmology in 1988
• Hubble constant controversy – some say it is 50
km/s/Mpc and others insist 100 km/s/Mpc
• Age of Universe: 6-12 billion years (depending on
Hubble constant). Age of stars in globular clusters:
15-20 billion years
• Theorists insist Ω0 = 1.0
• Observers only see Ω0 of 0.2 to 0.4, even including
unseen dark matter
Graduate Thesis Project is to
Weigh the Universe
Supernova Cosmology Project
The 4.0 meter Anglo-Australian Telescope
They built a special wide-field camera
This is what we are looking for.
Gerson
This search failed to find
supernovae because:
(1)The weather was terrible at the
AAT.
(2)The seeing was 2”, which meant
most supernova positions were less
than a seeing disk from the galaxy
center.
(3)AGN variability produced a
large set of false detections.
(4)They did not have scheduled
follow-up.
(5)Supernovae were dimmer than
expected.
Rich Muller suggested that maybe
Gerson had needed to re-orient it.
In 1992, the group had
overspent all budgets, had no
distant supernovae, and was in
quite a lot of trouble.
The funding and the control
was shifted from Carl
Pennypacker (who had started
the project) and Rich Muller
(who was the group leader) to
Saul Perlmutter (who was a
postdoc and the primary
technical driver for the
software). The search moved
to the CTIO 4m telescope, and
began to find supernovae.
Success brought competitors
The Hi-Z Super Nova (SN) Search team was composed of a dozen
well-seasoned astronomers who were experts in SN
phenomenology . They were less well funded than the LBL group,
not centrally controlled, generally dismissive of the astronomical
knowledge of the Supernova Cosmology Project members, and
jealous of the constant funding that the physicists were getting to
do science.
The Hi-Z team had the expertise and the contacts on the telescope
time assignment committees. The LBL group were experts in data
analysis, had several years head start, consistent funding, and an
established organization structure.
The race was on.
In a flat Universe:
ΩM = 0.28
[±0.085 statistical]
[±0.05 systematic]
Probability of Λ=0; 1%
In a flat Universe:
ΩM = 0.28
[±0.085 statistical]
[±0.05 systematic]
Probability of Λ=0: 1%
is related to
Einstein’s Field Equations
is related to
is related to
+Λ
No static solution
+Λ
Don’t need
a static
solution!!!
But we need an
accelerating
solution
is related to
is related to
Einstein’s Field Equations
is related to
is
related
to
相关于
没有静态解
Don’t need
a static
solution!!!
is related to
+Λ
No static solution
不需要静态
解
But we need an
accelerating
solution 但需要
加速解
+
Dark Energy
The change in the scale
factor with time
3
2
1
0
Size of Universe
4
H0 = 71 km/s/Mpc, ΩM = 0.3, ΩΛ = 0.7
-20
-10
0
10
Time (Gyr)
20
30
Dark Energy
Since the Λ term contributes positively to the energy
density of the Universe, it contributes to the curvature
the same way normal matter and dark matter do.
Since the pressure has the opposite sign, it is said that
“dark energy” has negative pressure, and this causes
the Universe to expand exponentially.
But there is still much that is unknown: what substance,
field, or force is responsible? Can Λ vary with time?
Assigning the Credit
Saul Perlmutter
Recognized leader of
Supernova Cosmology
Project, first author on
prize-winning paper,
technical innovator,
dedicated years of his life to
this cause.
Brian Schmidt
PI of Hi-Z SN
group, wrote
software
reduction code.
Adam Riess
First author of prizewinning paper (as a
graduate student), later
used HST to discover
more distant supernovae
at z~1.0
Hi-Z SN Search
Supernova Cosmology Project
The Hi-Z paper was submitted first, but with fewer supernovae. They
had the advantage of having seen the SCP results at conferences, and
knew that the SCP results agreed with theirs.
Robert Kirshner, Harvard
Gerson Goldhaber, celebrated
professor, and thesis advisor for both
Adam Riess and Brian Schmidt.
Postdoc advisor of Brian Schmidt. He
spent a lifetime studying supernovae.
particle physicist who joined Supernova
Cosmology Project about 1990. He
claims to have been the first to look at the
supernova data and believed that it
showed an acceleration.
Students and postdocs who made the observations, wrote the data reduction software,
figured out how to calibrate the light curves, and compiled the results had mixed
career results.
A Nobel Tradition
Arthur Compton
Discovered Compton Effect
Ernest Lawrence
Invented cyclotron Luis Alvarez
Richard Muller
Invented hydrogn McArthur FellowSaul Perlmutter
Discovered
Bubble chamber
accelerating
Universe
Dr. Newburg
The Nobel Prize in physics is given
for making important discoveries.
They are not given for:
• Intelligence
• Hard work
• Solid science
• Procuring the most grant money
• Popularity
• The most papers and citations (lifetime
achievement)
Tips for winning a Nobel Prize
None are required, and all together are not sufficient.
(1) Dare to work on something really important.
(2) Love it so much that it is your top priority. Procure a long-term
source of funding that does not depend on short term
accomplishments.
(3) Choose advisors and mentors who have reached their own
professional goals.
(4) Have a new idea every day, and a good one every week.
(5) Persevere through failure.
Where Do We Go From Here?
(1) Theorists need to explain the physical meaning of dark
matter (cosmological constant, quintessence, …).
(2) Experimentalists will measure how closely the expansion of
the Universe matches General Relativity with a constant Λ. 。
(3) The stellar models still predict 15 Gyr old globular clusters
in a 13.7 Gyr Universe
(4) We still need to figure out what the dark matter is.