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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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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.



Everything is dynamic, all the way to the expansion of the universe.

Our Expanding Universe

Bertschinger & Ma ; courtesy Ma

Our Cosmic Address

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

Our Cosmic Calendar

Inflation1016 GeV

Quarks  Protons1 GeV

Nuclei form1 MeV

Atoms form1 eV

[Room temperature 1/40 eV]

Stars and galaxies first form:1/40 eV

Today:1/4000 eV

Mapping Our History

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.


Discovery! Acceleration

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.

Discovery! Acceleration

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.

Negative pressure

What does negative pressure mean?

When something expands, it usually cools (loses energy).

Cool Oven

Hot Oven

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.

Dark Energy

Normal gravity is attractive. This is repulsive.

(Not being judgmental, so call it:)

Dark Energy

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.

Frontiers of Cosmology



95% of the universe is unknown!

cf. Tonry et al. (2003)



Cosmic Concordance

  • Supernovae aloneAccelerating expansion

  •  > 0

  • CMB (plus LSS)

  •  Flat universe

  •   > 0

  • Any two of SN, CMB, LSS

  •  Dark energy ~75%

Dark Energy Is…

  • 75% of the energy density of the universe

  • Accelerating the expansion, like inflation did when the universe was only 10-35 seconds old

  • Determining the fate of the universe

  • But what is it?

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.

What’s the Matter with Energy?

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.

What’s the Matter with Energy?

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.

Cosmic Coincidence?





Think of the energy in  as the level of the quantum “sea”. At most times in history, matter is either drowned or dry.

Dark energy



On Beyond !

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

Type Ia Supernovae

  • Exploding star, briefly as bright as an entire galaxy

  • Characterized by no Hydrogen, but with Silicon

  • Gains mass from companion until undergoes thermonuclear runaway

  • Standard explosion from nuclear physics


Insensitive to initial conditions:

“Stellar amnesia”

Höflich, Gerardy, Linder, & Marion2003

Standard Candle


Time after explosion

Brightness tells us distance away (lookback time)

Redshift measured tells us expansion factor (average distance between galaxies)

Supernova “CAT Scan”

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.

History & Fate

Hubble Diagram

~2000 SNe Ia






redshift z

10 billion years

Supernova Properties Astrophysics

Understanding Supernovae

Nearby Supernova Factory

G. Aldering (LBL)

Cleanly understood astrophysics leads to cosmology

Looking Back 10 Billion Years


Looking Back 10 Billion Years

Looking Back 10 Billion Years

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!

Dark Energy – The Next Generation

Dedicated dark energy probe

e.g. SNAP: Supernova/Acceleration Probe

Design a Space Mission




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.

Weighing Dark Energy

Exploring Dark Energy

Needed data quality

Dark energy theories

Current ground based compared with

Binned simulated data and a sample of

Dark energy models

The History of Our Universe

First Principles of Cosmology E.V. Linder (Addison-Wesley 1997)

The Fate of Our Universe

Size of Universe




Future Age of Universe

Looking back 10 billion years

to look forward 40 billion

Cosmic Background Radiation

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)

The Universe: Early and Late

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!

Cosmic Archaeology

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!)

Geometry of Space



CMB tells us about the geometry of space - flat? curved?

But not much about evolution (snapshot) or dark energy (too early).

Gravitational Lensing

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

Gravitational Lensing

N. Kaiser

Lensing by (dark) matter along the line of sight

“Galaxy wallpaper”

Gravitational Lensing

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.

The Next Generation

SN Target

Fate of the Universe

Contemporary Physics Education Project (CPEP)

Frontiers of the Universe

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!

Frontiers of Science

Let’s find out!



Breakthrough of the Year


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