Moments of Discovery

1
The Uncertain Nature of Gravity
An Illustration of Science as a Process of
Investigating Nature
2
The Nature of Science

• Ideas are supported by testable and verifiable
  data or observation
• Science is a process or way to investigate
  nature.
• Scientific knowledge doesnt mean possessing the
  truth.
• Science seeks consistency between observations
  and models

3
Once Upon a Time

• We were certain that
• The Earth was the Center of the Universe
• The Earth was motionless
• All things fell toward the Earth unless there
  were in the perfect celestial realm

4
Aristotle Puts Us in the Center of the Universe
5
Arrogance and the Anomaly
Three Choices 1. Ignore it 2. Fit it to your
Bias 3. Throw out your Bias
6
Discovery in ScienceHow are understanding of
gravity evolved

• Usually occur accidentally
• Often is a first response to new instrumentation
  or new forms of thinking or new kinds of cultural
  interchange
• May often be ignored depending on cultural bias

7
Newtons Apple and Laws
Apple always falls down? Gravity is an attractive
force only? (so no anti-gravity!) All matter
attracts each other? Why hasnt the Universe
collapsed?
8
Two Kinds of Mass
9
Equivalence Principle
10
Information and Communication

• Physics works by information exchange via
  particles
• Particles can be screened because particles
  interact with matter
• But There is no such thing as a GRAVITY SCREEN!

11
Physics to Engineering

• For all practical aspects we are done now
  Newtons laws provide the scientific foundation
  to engineer the planet.
• But, remember the Anomaly
• 1859 precision observations of the orbit of
  Mercury DISAGREE with Newtonian Mechanics!

12
Now we need a new Theory

• Einstein Gravity Curvature of Spacetime

13
Ouch, Curved Spacetime?

• More mass greater curvature
• Affects time
• E mc2 means that photons have energy related
  mass and therefore follow the curvature

14
The Need for Dark Matter

• 1970s Start to measure rotational properties
  of other galaxies
• Invariably observe flat rotation curves

15
Resolution

• Galaxies must be surrounded by Halos of dark
  material than contain 90 of the total mass?
• But what is this dark matter? ? We still dont
  know after 30 years of detailed investigation and
  theory
• Is there another explanation?

16
Maybe we still dont understand Gravity?

• Maybe gravity works differently on different
  acceleration scales?
• This means the effective acceleration on an
  object changes so the force law changes ? no need
  for dark matter
• Modified Newtonian Dynamics (MOND) empirically
  fits the data as well as the Dark Matter Theory
• But MOND violates the Equivalence Principle
  ?therefore if its correct, Einsteins theory has
  a major flaw

17
Reconciliation An Extra Dimension

• Gravitons ? the exchange particles in the
  gravitational force are different they leak to
  another dimension
• Explains why the Gravitational force is so weak

18
The Mysterious Dark Energy
ACTS LIKE ANTI GRAVITY!
19
Summary

• We have a good understanding of how gravity works
  on the Earth
• What is the nature of the Dark Matter?
• If MOND is correct alternative, what is the
  nature of SpaceTime now that the equivalence
  principle is violated
• Does the extra dimension explain how gravity
  works throughout the Universe
• What is the nature of the Dark Energy?

20
Bottom Line
Apparently Life is not so Simple anymore. There
is much still to learn!
21
Our Current Response
Will we Acquire Global Wisdom in Time?
22
The Coming Resource Scarcity

• The Decline of Oil

23
How the Universe Helps

• Its a big place, with much to discover
• People think about it in scientific,
  philosophical and artistic terms
• It is your ultimate environment life is made
  from star dust
• It reminds us of the great unknown and may help
  to humble us during our more arrogant moments

24
The value of Universities

• Provides a safe haven for discovery (both
  personal and intellectual)
• Instills critical thinking in terms of conflicts
  between discovery, comfort zones, and potential
  paradigm shifts
• Helps students appreciate the intrinsic value of
  research and asking questions
• Astronomy is a good venue to teach these
  attributes of science and discovery

25
Discovery is Everywhere
26
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27
New Kinds of Solar Systems
28
A Tenth Planet?
29
Origin of Life?
30
STAR DUST
31
Perspectives

• Science is Discovery
• Most is Unknown
• Certainty is unwarranted
• Knowledge is contextual
• Cultural Bias Drives our Decisions
• Finite Resources require wisdom to Manage
• Can we re-acquire this Wisdom?

32
The End