The Driving Questions�Scientific Motivation for the SKA
S.A. Torchinsky�Observatoire de Paris�SKADS Project Scientist
S.A. Torchinsky (1 of 1051920)
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Driving Questions
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The Driven Outline
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Some Definitions
Scientific Motivation�and�the Square Kilometre Array
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What is the “SKA” ?
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What is “Scientific Motivation” ?
Topic for discussion at�Café de Flore…
Why do we want to understand the Big Picture?
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Is there a Big Picture?
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Exceedingly brief�technical overview
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Δd
Electronic box
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Δd
Electronic box
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Δd
Electronic box
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Δd
Electronic box
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Synthesised beam
By selecting the path length, or by introducing a phase shift, we can electronically�steer the beam.
More technical details today with Philippe Picard
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Possible SKA Configuration
Station
Core ~5km dia
Central
Processing
Facility
Comms links
Not to scale!
180km
Dishes spread
along spiral
Dishes
AA-hi
AA-lo
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Three Technologies
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Beamformer Chip
Electronic box
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Scientific Motivation
Fundamental questions�for which we seek answers
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Key Science Questions
Tests of gravity
Epoch of Reionisation
Cosmic Magnetism
Cradle of Life
Large Scale Structure
Transient Universe
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SKA Science Book
Chris Carilli & Steve Rawlings,
New Astronomy Reviews, Vol.48, Elsevier, Dec. 2004
http://www.skads-eu.org/p/SKA_SciBook.php
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Cosmology, Galaxy Formation
and Astroparticle Physics on
the Pathway to the SKA
Hans-Rainer Klöckner, Steve Rawlings,
Matt Jarvis, Angela Taylor (eds.)
Cosmology, Galaxy Formation and Astroparticle Physics on the Pathway to the SKA
Available online:
www.skads-eu.org (click “memos” or “documents”)
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Cradle of Life
What conditions are necessary for the development of life?
How are planetary systems formed?
Is the solar system a special case?
How and where are complex (organic) molecules formed?
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Cradle of Life
G. Bryden / NASA
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Cradle of Life
Is there anybody out there?
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Indicators of �Extra Terrestrial Intelligence
Project
Phoenix
Allen
Telescope
Array
SKA
Jill Tarter
SETI at leakage levels from nearby stars
eg:
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Cradle of Life
The stellar environment and processes leading to the formation of stars, and planetary systems: on Wednesday…
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Strong Field Tests of Gravity
Is Einstein right about gravity?
Is there a strong-field limit at which GR is no longer the correct description of gravity?
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Strong Field Tests of Gravity
How right is Einstein about gravity?
What is the strong-field limit at which GR is no longer the correct description of gravity?
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Strong Field Tests of Gravity
Binary orbit permits determination of masses
Relativistic effects permit (re) determination of masses.
ALL MUST AGREE
http://www.jb.man.ac.uk/~pulsar/
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Strong Field Tests of Gravity
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Pulsar Timing Array
Is there a gravitational wave background? Is it primordial?
Can we probe the Universe at times before the Epoch of Recombination when the Universe was opaque to EM radiation?
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Pulsars
more on pulsars tomorrow with Aris Karastergiou
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Interlude
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The History of the Universe
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End of Interlude
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Probing the Dark Ages
When did the first luminous objects form? When was “first light”?
How did they form, and over what period of time?
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Epoch of Reionisation
SKA will detect the Epoch of Reionisation and map the evolution history of the first luminous objects
Di Matteo et al
More from Benoit Semelin on EoR tomorrow
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Cosmic Magnetism
M 51 VLA+Eff 6cm
(Fletcher & Beck)
What is the origin of magnetic fields in the Universe?
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Cosmic Magnetism
SKA will measure Faraday rotation of > 107 polarised background sources
NGC 891 (Krause)
More from�Rainer Beck tomorrow
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Dark Energy
What is the nature of Dark Energy?
Is it just a geometrical feature of General Relativity?�(was Einstein wrong when he thought he was wrong?)
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Large Scale Structure
Billions of galaxies!
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Baryonic Acoustic Oscillations
More on BAO with Françoise Combes tomorrow
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Dark Mass
Where is the dark mass in the Universe?
How is it distributed?
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Cosmic Shear
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The Distribution of Matter
Clusters: Chiarra Ferrari on Wednesday
Galaxies: Wim van Driel on Wednesday
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Transients
Start recording…
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Transient signal
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Transients
Is there a population of powerful, irregular, transient sources?
What are they?
How do they generate the energy they emit?
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Transients
requires:
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Transient signal
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Transients
More from Aris Karastergiou tomorrow.
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Fundamental Questions
Are we asking the right questions?
Suppose we could ask a super intelligent space alien …
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fundamental questions
Why is there so much human suffering?
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fundamental questions
Is there a God?
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fundamental questions
What is�Dark Energy?
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These are the wrong questions
These are the wrong questions!
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The Unknown
“These are the�wrong questions!”
Woody Allen, Stardust Memories
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Is there a Big Picture?
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Examples of Wrong Questions
If you walk so far that you reach the end of the Earth, will you fall over the edge? Will you fall forever? What supports the Earth?
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Examples of Wrong Questions
How fast are we moving with respect to the ether?
What might have been a better question?
Is there an ether?
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Examples of Wrong Questions
How can I make the General Theory of Relativity compatible with the Steady State Universe?
oops
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Examples of Wrong Questions
What is north of the North Pole?
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Examples of Wrong Questions
What happened before the Big Bang?
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Before time…
there can be no doubt that the universe was not created in time but with time. An event in time happens after one time and before another, after the past and before the future. But at the time of creation there could have been no past, because there was nothing created to provide the change and movement which is the condition of time.
St. Augustine of Hippo (417A.D.)
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Smart guys…
As for the ‘antipodes’, men, that is, who live on the other side of the earth, where the sun rises when it sets for us, men who plant their footsteps opposite ours,
there is no rational ground for such a belief.
fabled
St. Augustine of Hippo (418 A.D.)
…are not always right
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Smart guys…
…are not always right
Don’t be afraid to question the smart guys!
1889: Heinrich Hertz, “no practical purpose for EM waves”
1915: Einstein, a cosmological constant to maintain a static universe
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The Unknown
SKA improves all of these
SKA is designed for the Key Projects but with an overriding design philosophy of flexibility to maximise the likelihood of new discoveries
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Discoveries are made…
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And discoveries are made…
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New questions
It’s up to you to think of new questions!
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Scientific Motivation
?
Tests of gravity
Epoch of Reionisation
Cosmic Magnetism
Cradle of Life
Large Scale Structure
Transient Universe
The Unknown
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