Chapter 2 – The Science of Life in the Universe
The Big Idea
This is a “perspective” Chapter
How did we get to the point where we can address
the question of extra-terrestrial life
in a scientific way?
And what does “scientific way” mean, anyway?
Jump ahead
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Ch 2.2 - The Copernican Revolution
The Heliocentric All Star Team I.
•
Nicholas Copernicus (~1540)
– revives the heliocentric idea
•
Tycho Brahe (~1580)
– most precise naked-eye planetary positions
– accuracy ~1/60 of a degree!
•
Johannes Kepler (~1610)
– detailed analysis of Tycho’s data
– heliocentric model works best
– planet orbits are ellipses
– planet orbital speeds vary
– bigger orbits → longer periods
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“3 Laws of Planetary Motion”
Life in the Universe - Ch. 2
(see Figs. 2.7 – 2.9)
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Ch 2.2 - The Copernican Revolution
The Heliocentric All Star Team I.
•
Nicholas Copernicus (~1540)
– revives the heliocentric idea
•
Tycho Brahe (~1580)
– most precise naked-eye planetary positions
– accuracy ~1/60 of a degree!
•
Johannes Kepler (~1610)
– detailed analysis of Tycho’s data
– heliocentric model works best
– planet orbits are ellipses
– planet orbital speeds vary
– bigger orbits → longer periods
Fall 2014
“3 Laws of Planetary Motion”
Life in the Universe - Ch. 2
(see Figs. 2.7 – 2.9)
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The Heliocentric All Star Team II.
•
Galileo (early 1600’s)
– first telescopic observations favored heliocentric model
(but couldn’t prove Earth moves!)
– early understanding of physics of motion
•
Isaac Newton (~1700)
– discovered physical principles behind Keplers’ results
– mathematically describes the physics of motion
Newton’s Three Laws of Motion
(see Fig 2.12)
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The Heliocentric All Star Team II.
•
Galileo (early 1600’s)
– first telescopic observations favored heliocentric model
(but couldn’t prove Earth moves!)
– early understanding of physics of motion
•
Isaac Newton (~1700)
– discovered physical principles behind Keplers’ results
– mathematically describes the physics of motion
Newton’s Three Laws of Motion
(see Fig 2.12)
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Kepler’s Three Laws
1.
Orbits are
ellipses
Fall 2014
2.
Orbital
speed changes
during orbit
Life in the Universe - Ch. 2
3.
Orbital size
and period are
related
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But What About Extraterrestrial Life?
•
Greek “atomists” believed heavens composed of same element as Earth
- and populated by life.
•
Others (“Aristotelians”) believed Earth to be unique – the special
center of the Universe
Copernican Revolution showed that Earth does not occupy a special
place in the Universe…
Earth is just another place…
What happens here probably happens in lots of other places…
Made it easier to believe the life might exist elsewhere
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So it seems intellectually reasonable
to think about extra-terrestrial life
But how do we approach
the issue “scientifically”?
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Ch 2.3 - The Nature of Modern Science
definition:
“science” = the view that the physical Universe is governed by a welldefined set of rules (i.e., is a “rational” place)
= the endeavor to uncover those rules
The rules that govern the physical Universe can be expressed
mathematically
(this is a great thing)
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“The Scientific Method”
• An idealized view of how science
proceeds
This is the key part
• A scientific theory is testable
• A scientific theory is “falsifiable”
• A scientific theory can never be
proven to be right!
Fig 2.13
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Distinguishing Science from Pseudo-Science
• There are several characteristics
which define scientific thinking
• UFO-ology, creationism, belief in
psychic powers, astrology, etc. all
fail to achieve one or more of
the hallmarks.
• They are not science
Fig 2.14
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So, our approach to Life in the Universe
will be a “scientific” one.
We will utilize only reliable & repeatable
observations
If we formulate any conclusions,
explanations, or theories,
they must be testable and falsifiable!
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“Science in Action”
Ch 2.4 - The Fact and Theory of Gravity
Isaac Newton
•
Newton first realized that an attractive “force” (gravity) could explain
many different phenomena
Falling apples, rocks, cows,…
Earth’s orbit around Sun
Moon’s orbit around Earth, etc.
•
Strength of force depends only
only on masses & separation!
•
Successfully predicted comet
orbits, existence of Uranus,…
Fig 2.16
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But what the heck is a “force”
“Action at a distance”
sounds a bit like magic.
Newton’s Universal Law of Gravitation
really doesn’t tell us what gravity is.
And it doesn’t actually work all the time!
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Albert Einstein
•
Suggests gravity results from curvature of space!
mass distorts space
orbits are straight lines in curved space!
Fig 2.17
•
“General Relativity” reproduces all of Newton’s results – plus - it works
in places where Newton’s theory didn’t
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General Relativity has passed all tests so far
But is it right?
Do we understand gravity?
Probably not!
GR not consistent with quantum mechanics
(the study of the subatomic world)
There’s probably a bigger theory out there,
but we don’t know what it is yet…
…predicting & testing go on…
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