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Q&A, August 4th, 2014
Adam Myers
3. UFOs and the Scientific
Method
Hallmarks of Scientific
Reasoning
Experimental
Scientific
theories are based on observations
(this is Aristotle’s empiricism)
Falsifiable
Scientific
theories make predictions that can be
disproved by empirical observations by more
than one person (this is objectivity)
Simple
Search
for the simplest theory that explains the
observations (also called Occam’s razor)
Astronomy is not Astrology
because
Cause is not Correlation
I
think the importance of prediction is under-stressed
as the critical part of the scientific method
Astronomy is not Astrology
because
Cause is not Correlation
0
Astronomy is not Astrology
because
Cause is not Correlation
0
Astronomy is not Astrology
because
Cause is not Correlation
1
Astronomy is not Astrology
because
Cause is not Correlation
0
Astronomy is not Astrology
because
Cause is not Correlation
1
Astronomy is not Astrology
because
Cause is not Correlation
1
Astronomy is not Astrology
because
Cause is not Correlation
42
Astronomy is not Astrology
because
Cause is not Correlation
I
think the importance of prediction is under-stressed
as the critical part of the scientific method
As Imre Lakatos put it (www.lse.ac.uk/lakatos) a
theory is pseudoscientific if it fails to make novel
predictions of previously unknown phenomena
It’s not that pseudoscience is demonstrably wrong, it’s
that ideas that are impossible to demonstrate wrong
are entirely equivalent in meaning
A classic idea that is impossible to demonstrate wrong
is the contention that something does not exist
UFOs
 It’s
worth asking what a meaningful testable contention
for UFOs (a “UFO hypothesis”) would look like
 Contrary
to the idea that there’s some sort of cover-up,
multiple global scientific committees over many decades
have at least asked the testable question “what fraction
of UFO sightings cannot be naturally explained?”
 For
instance, the Condon Committee (1968) studied 59
cases and found only 1 case that defied natural
explanation
 This
case, the “Lakenheath-Bentwaters Incident”, has
been recently reanalyzed...it turns out that eyewitness
accounts of UFO sightings even in this incident contradict
each other far more than was originally stated in the
Condon report
UFOs
 For
instance, the Condon Committee (1968) studied 59
cases and found only 1 case that defied natural
explanation
 This
case, the “Lakenheath-Bentwaters Incident”, has been
recently reanalyzed...it turns out that eyewitness accounts
of UFO sightings even in this incident contradict each other
far more than was originally stated in the Condon report
 If
99-100% of UFO accounts turn out to be naturally
explicable, then why should your favorite “inexplicable”
account be real?
 except, of course that UFOs are pseudoscience and that
it is impossible to completely prove that a thing does not
exist
 Also,
Pan-STARRS has been scanning the sky repeatedly
for 4 years without detecting any unusual objects!
4. Do gamma-ray bursts have
anything to do with quasars?
A Very Strange Star
 3C
273 is a very
powerful radio source
 Astronomer Maarten
Schmidt took optical
images of it in 1963 and
found it looked like a
normal blue star
 He also took a spectrum
and found it had very
odd spectral lines
 Not a star
Quasar Spectra
I
n
t
e
n
s
i
t
y
400 Wavelength (nm) 900
When
100 Wavelength (nm) 800
a spectrum is taken, a quasar looks
nothing like a star
The Mystery of Quasars
3C
273 is a quasar
(QUASi-stellAR object)
Redshift ~ 0.16 ⇒
Distance ~ 2.4 billion
light years away
Andromeda
galaxy is
~1000 times closer
Apparent
It
Quasar 3C 273
magnitude of 3C 273 ~ 12.9
is easily visible using even an 8-inch telescope
3C 273 must be incredibly luminous
Equal to 2 trillion Suns, or 100 times the entire
Milky Way!
Quasars, In Brief…
 Quasars
are at “astronomical” distances
Most
are over 3 billion light years away, some are at
distances corresponding to the early Universe
 Quasars are at great distances - so are very luminous
The most luminous quasars are (intrinsically) more
than 100 times the brightness of our Galaxy
 Quasar
spectra suggest very hot, rapidly orbiting gas
 Quasars are also long-lived...they shine for tens of
thousands of years
The explanation for such continuously luminous
objects, is that quasars are caused by very hot gas
orbiting black holes at the center of distant galaxies
What is
a Quasar?
Billion Lyr YS, Adam Myers
Life of a Low Mass Star
Main sequence
Core hydrogen burning
Tcore ~ 15 million K
Helium flash
Horizontal branch
Core helium burning
Tcore ~ 100 million K
Red giant
Shell hydrogen
burning
Asymptotic branch giant
Shell helium burning
Iron – The End of the Road
 Supergiants
“burn” heavier and heavier atoms in the
fusion process
 Creates shells of different elements inside the star
 Each stage is faster than the last
 The process stops at iron
Stage Temperature Duration
H fusion 40 million K 7 million
yr
He fusion 200 million K 500,000
C fusion 600 million K
600
yryr
Ne fusion 1.2 billion K
1 yr
O fusion 1.5 billion K
6 mo
Si fusion 2.7 billion K
1 day
Values for a ~20MSun star
When Electron Degeneracy
Just Isn’t Enough
e
p
p
e
p
e
Matter in the core of a
normal star
SQ U
EEZE
e
e
e
p
p
p
e
e
e
p
p
p
e
e
e
p
p
p
e
e
e
p
p
p
Electron-degenerate matter
1 ton per cubic cm
If the core is 1.4 solar masses or more
(called the Chandrasekhar Limit) then a
Type II Core Collapse supernova occurs
SQUE
EZE
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
Neutron-degenerate matter 100
million tons per cubic cm
ν
ν
ν
Neutrinos are
produced as electrons
are forced into nuclei
Supernova
Bright as a Galaxy
Supernovae
are
bright
A star’s
brightness
increases by a
factor of 10,000
This is almost as
bright as an entire
galaxy!
Light from a single
supernova
Combined
light of 100
billion stars
Supernova 1987A
Before
Feb. 23, 1987
Supernova 1987A in 1994
Gamma-Ray Bursts, In Brief…
 If
you look in optical light at the positions of gammaray bursts, the bursts occur in distant galaxies
As
with quasars, most are > 3 billion light years away,
many at distances corresponding to the early Universe
 GRBs
are at great distances - so are very luminous
Gamma-ray
 But
bursts are roughly as bright as quasars
gamma-ray bursts are short in duration
On the scale of seconds to hours, as compared to
quasars which shine for tens-of-thousands of years
 Gamma-ray bursts look more like explosions than
like long-lived processes...the current idea is they are
energy from supernovas, beamed towards the Earth
Q&A, August 4th, 2014
Adam Myers