Mapping the History and Fate of the Universe. DOE Science Colloquium. Eric Linder Lawrence Berkeley National Laboratory. Uphill to the Universe. Steep hills: Building up - Eroding away - . Start Asking Why, and. There is no division between the human world and cosmology. . . .
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History and Fate of the Universe
DOE Science Colloquium
Lawrence Berkeley National Laboratory
Building up -
Eroding away -
There is no division between the human world and cosmology.
Everything is dynamic, all the way to the expansion of the universe.
Bertschinger & Ma ; courtesy Ma
Our Sun is one of 400 billion stars in the Milky Way galaxy, which is one of more than 100 billion galaxies in the visible universe.
Earth 107 meters
Solar system 1013 m
Milky Way galaxy 1021 m
Local Group of galaxies 3x1022 m
Local Supercluster of galaxies 1024 m
The Visible Universe 1026 m
Quarks Protons1 GeV
Nuclei form1 MeV
Atoms form1 eV
[Room temperature 1/40 eV]
Stars and galaxies first form:1/40 eV
The subtle slowing down and speeding up of the expansion, of distances with time: a(t), maps out cosmic history like tree rings map out the Earth’s climate history.
data from Supernova Cosmology Project (LBL)
graphic by Barnett, Linder, Perlmutter & Smoot
Exploding stars – supernovae – are bright beacons that allow us to measure precisely the expansion over the last 10 billion years.
In 1998, the Supernova Cosmology Project and Hi-Z Team discovered the expansion was speeding up
– but gravity pulls things together and should slow the expansion. What is counteracting gravity?
Einstein said that energy contributes to mass:
Gravity arises from all energy, not just the usual mass.
The pressure P of a substance affects the gravity, but this is usually very tiny (because the speed of light c is large, so mc2is much bigger than P).
But doesn’t this just add to the gravity? Unless the pressure is negative.
What does negative pressure mean?
When something expands, it usually cools (loses energy).
But if you expand (stretch) a spring, it gains energy.
Quantum physics predicts that the very structure of spacetime should act like springs.
Space has a “stretchiness”.
This gives a negative pressure. Add this to the usual mass (galaxies, stars). If there’s enough quantum stuff, it will win out, and the universe will act like the total mass is negative!
Is this antigravity? No.
No – it’s gravity just as Einstein predicts it, but since it acts like negative mass, it doesn’t bring galaxies together, it pulls them apart.
Normal gravity is attractive. This is repulsive.
(Not being judgmental, so call it:)
Dark energy speeds up the expansion of the universe. By measuring the acceleration using our tree ring (supernova) method, we find that dark energy makes up ~75% of the universe!
Because it dominates over the matter contents (which make up only ~25%), dark energy will govern the expansion, and the fate of the universe.
95% of the universe is unknown!
Einstein considered something like it when he first invented general relativity. He wanted just enough negative pressure to balance the mass, so the universe would be static. He called it the cosmological constant, but abandoned it later when observations showed the universe was expanding.
Why not just bring back the cosmological constant ()?
When physicists calculate how big should be, they don’t quite get it right.
They are off by a factor of
1,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000.
This is modestly called the fine tuning problem.
But it gets worse: because the cosmological constant is constant, it is the same throughout the history of the universe.
Why didn’t it take over the expansion billions of years ago, before galaxies (and us) had the chance to form?
Or why didn’t it wait until the far future, so today we would never have detected it?
This is called the coincidence problem.
Think of the energy in as the level of the quantum “sea”. At most times in history, matter is either drowned or dry.
On beyond ! It’s high time you were shown
That you really don’t know all there is to be known.
-- à la Dr. Seuss, On Beyond Zebra
We need to explore further frontiers in high energy physics, gravitation, and cosmology.
New quantum physics?Quintessence (atomic particles, light, neutrinos, dark matter, and…)
New gravitational physics? Quantum gravity, supergravity, extra dimensions?
We need new, highly precise data
Insensitive to initial conditions:
Höflich, Gerardy, Linder, & Marion2003
Time after explosion
Brightness tells us distance away (lookback time)
Redshift measured tells us expansion factor (average distance between galaxies)
Over time the SN atmosphere expands and thins, allowing us to see every layer.
The energy spectrum of a supernova tells us in fine detail about its origin and properties.
~2000 SNe Ia
10 billion years
Nearby Supernova Factory
G. Aldering (LBL)
Cleanly understood astrophysics leads to cosmology
To see the most distant supernovae, we must observe from space.
A Hubble Deep Field has scanned 1/25 millionth of the sky.
This is like meeting 10 people and trying to understand the complexity of the entire population of the US!
Dedicated dark energy probe
e.g. SNAP: Supernova/Acceleration Probe
9000 the Hubble Deep Field
plus 1/2 Million HDF
• Redshifts z=0-1.7 • Exploring the last 10 billion years • 70% of the age of the universe • Your life from 12-40 years old
Both optical and infrared wavelengths to see thru dust.
Needed data quality
Dark energy theories
Current ground based compared with
Binned simulated data and a sample of
Dark energy models
First Principles of Cosmology E.V. Linder (Addison-Wesley 1997)
Size of Universe
Future Age of Universe
Looking back 10 billion years
to look forward 40 billion
Snapshot of universe at 380,000 years old, 1/1100 the size
Hot and cold spots simultaneously the smallest and largest objects in the universe: single quantum fluctuations in early universe, spanning the universe at the time of decoupling.
Planck satellite (2007)
Relic imprints of quantum particle creation in inflation - epoch of acceleration at 10-35 s and energies near the Planck scale (a trillion times higher than in any particle acclerator).
These ripples in energy density also occur in matter, as denser and less dense regions.
Denser regions get a “head start” and eventually form into galaxies and clusters of galaxies. How quickly they grow depends on the expansion rate of the universe.
It’s all connected!
Supernovae: direct probe of cosmic expansion
Time: 30-100% of present age of universe
(When you were 12-40 years old)
Cosmic matter structures: less direct probes of expansion
Pattern of ripples, clumping in space, growing in time.
3D survey of galaxies and clusters.
CMB: direct probe of quantum fluctuations
Time: 0.003% of the present age of the universe.
(When you were 0.003% of your present age, you were a 2 celled embryo!)
CMB tells us about the geometry of space - flat? curved?
But not much about evolution (snapshot) or dark energy (too early).
Gravity bends light… - we can detect dark matter through its gravity, - objects are magnified and distorted, - we can view “CAT scans” of growth of structure
Lensing by (dark) matter along the line of sight
Lensing measures the mass of clusters of galaxies.
By looking at lensing of sources at different distances (times), we measure the growth of mass.
Clusters grow by swallowing more and more galaxies, more mass.
Acceleration - stretching space - shuts off growth, by keeping galaxies apart.
So by measuring the growth history, lensing can detect the level of acceleration, the amount of dark energy.
Contemporary Physics Education Project (CPEP)
Size of Universe
Future Age of Universe
What is dark energy?
Will the universe expansion accelerate forever?
Does the vacuum decay?
How many dimensions are there?
How are quantum physics and gravity unified?
What is the fate of the universe?
Uphill to the Universe!
Let’s find out!
Breakthrough of the Year