Lecture 3: Chapter 1- Charting the Heavens Assignment: Read Chapter 1 of Astronomy Today
1.2 Scientific Theory and the Scientific Method Scientific number notation Measures of Distance
1.2 Scientific Theory and the Scientific Method Observation leads to theory explaining it. Theory leads to predictions consistent with previous observations. Predictions of new phenomena are observed. If the observations agree with the prediction, more predictions can be made. If not, a new theory should be made.
1.2 Scientific Theory and the Scientific Method Scientific theories: Must be testable Must be continually tested Should be simple Should be elegant Scientific theories can be proven wrong, but they can never be proven right with 100 percent certainty.
It s only a theory! Theories can only be disproven not proven - What does that mean? Does that mean we can or should ignore the findings? Do we have to give equal time to all theories or points of view?
Sum of angles in a triangle on a flat field A + B + C = 180 degrees
Or A + B + C = 2 right angles A + B + C add up to a straight line
Triangle on a sphere - The Earth A + B + C = 3 right angles A + B+ C not = to 2 right angles
Compression of a gas P = pressure V = volume T = temperature Boyle s law: or P x V / T = constant P x V ------- = constant T This law may break down at very high pressures
According to Galileo addition of velocities is described by total velocity s = u + v However, at high velocities velocity addition (according to Einstein) is given by
The Bernoulli Effect
Scientific arguments are very effective when the circumstances are simple However, we are living in a complex world Scientists argue about the value and significance of observations and about the interpretation of complex phenomena Argument and disagreement is part of the scientific process
Scientific number notation Key Concepts!!Large numbers, scientific notation!!scale of the Solar System: use of scale factors; light travel time!!spaceship Earth? The Night Sky: Constellations
Understanding Big Numbers! Florida population: 18,800,000 (18.8 million)! US population: 308,000,000 (308 million)! Earth population: 6,800,000,000 (6.8 billion)! Stars in our Galaxy 200,000,000,000 (200 billion)! 2010 US defense budget: 685,100,000,000 (685.1 billion dollars)! US debt as of August 22 nd, 2011: 14,638,272,000,000 (14 trillion!)
Name (U.S) Number Scientific Notation How long it would take to count to this number from 0 One 1 10 0 1 second Thousand 1,000 10 3 17 minutes Million 1,000,000 10 6 12 days Billion 1,000,000,000 10 9 32 years Trillion 1,000,000,000,000 10 12 32,000 years (longer than civilization on Earth) Quadrillion 1,000,000,000,000,000 10 15 32 million years (longer than humans on Earth)!"#$%&'()*&!"##"$%&'(%)'!"##"$%&'+,"(-&."/"%0&
!!Compact way of expressing large and small numbers using powers of 10: 5.9742!10 24 kg Mantissa: the significant digits of the number Exponent: The power of 10 of the number
!!!!!!
Working with Exponential Notation!"#$%&'($)*&+)$&+,$*-,+,$.'$*-,$"/),+0&/1,$2'.0,+),3$ Lets say there are about 200 billion (2 x 1011 ) stars in our Galaxy and about 200 billion (2 x 1011) galaxies like our own in the observable universe. 4-,'5$-"#$%&'($)*&+)$&+,$*-,+,3$ 621781.9&7"'$:;<<$,=8"','*)>$ :?$=$@A@@>$=$:?$=$@A@@>$B $ $ $$$$$$B $$:?$=$?>$=$@A:@@C@@>$B$D$=$@A??$ $$DA$=$@A?@$$$$:DA$),=711."'>$
Working with Exponential Notation From movie Contact:!"#$%&'&#()*&#+,$#$%&'&-# `` If only one out of a million of those [stars] has planets, and one out of a million of those have life, and just one out of a million of those has intelligent life, there would be literally millions of civilizations out there..&$"#/+#$%(0,(12+3#,")34#+,'#'&",($#*+'#$%,56&'#+*#"$1'"#)3#$%&# +6"&'716(&#,3)7&'"Y#:#;< == #"$1'"># Division (Subtract Exponents) (4 x 10 22 ) / (10 6 ) = 4 x 10 (22-6) = 4 x 10 16 stars with planets (4 x 10 16 ) / (10 6 ) = 4 x 10 (16-6) = 4 x 10 10 planets with life (4 x 10 10 ) / (10 6 ) = 4 x 10 (10-6) = 4 x 10 4 planets with intelligent life??@ab#$%1$c"#+3(d#9<#$%+,"13/#0)7)()e12+3"b#
Our Solar System - Sizes 1 mile = 1.6 km 12,756 kms = 1.28 x 10 4 km 142,984 kms = 1.43 x 10 5 km 1,292,000 kms = 1.292 x 10 6 km Diameter of Sun ~ 109 times diameter of Earth Diameter of Jupiter ~ 12 times diameter of Earth
Our Solar System - Distances! Distance to Moon = 384,000km = 3.84x10 5 km»! ~ 30 Earth Diameter! Distance to Sun = 150,000,000km = 1.5x10 8 km = 1 Astronomical Unit (AU)»! ~ 12,000 Earth Diameter! Distance from Sun to Pluto = 5,900,000,000km = 5.9x10 9 km = 39.5AU»! ~ 500,000 Earth Diameters
!! A. 6,378 km!! B. 384,000 km!! C. 1.496!10 8 km!! D. 5.906!10 9 km!! E. 3.992!10 13 km!! F. 2.47!10 17 km!! G. 2.74!10 19 km
!! A. 6,378 km!! B. 384,000 km!! C. 1.496!10 8 km!! D. 5.906!10 9 km!! E. 3.992!10 13 km ~ 40 trillion km!! F. 2.47!10 17 km!! G. 2.74!10 19 km
!! Astronomical Unit (AU):! Mean distance from the Earth to the Sun: 1 AU! 1.496 " 10 8 kilometers Used for distances between planets.!! Light Year (ly):! Distance traveled by light in one year: 1 ly = 9.46 " 10 12 kilometers Used for distances between stars. Parsec (parallax second) (ly): How far away is the second nearest star in light years?
How far away is the second nearest star in light years?!! D. 5.906!10 km!! E. 3.992!10 13 km ~ 40 trillion km! F. 2.47 10 17 km 1 ly = 9.46 " 10 12 kilometers Used for distances between stars. Answer is 4 ly
1 Astronomical Unit (AU) Venus Mars Mercury Sun 1 AU Earth Earth-to-Sun distance: 1 AU = 149,600,000 km
Star A large, glowing ball of gas that generates heat and light through nuclear fusion
Planet! Orbits a star; shines by reflected light.! More massive than everything else on its orbit! Planets may be rocky, icy, or gaseous in composition.
Planets may be common!! (1995 today)
Moon (Satellite) An object that orbits a planet.
Asteroid A relatively small and rocky object that orbits a star.
Comet A relatively small and icy object that orbits a star.
Solar (Star) System A star and all the material that orbits it, including its planets and moons
1 Astronomical Unit (AU) Venus Mars Mercury Sun 1 AU Earth Earth-to-Sun distance: 1 AU = 149,600,000 km
100 AU Outer Solar System
8.6 ly 640 ly 815 ly
Question!"#$%&'$()$*+)$,-."/$/0&1),$/-2)$/3$2)&+*0)$ 4-+/&'%)+5$
Looking back in time!!"#$%&'()%$*+#$',(-%&'%.(/0)-'(%'('12"%0'-30045'! 6$0'-3004'*,')"#$%'"-'7*2-%(2%'"2'('/(7++8' Speed = distance / time! d = c t Speed of light, c = 300,000 km/s = 3x10 5 km/s
Distances Beyond Our Solar System! Distance from Sun to nearest stars (Alpha Centauri system)= 37,950,000,000,000 km (3.8x10 13 km) = 4.2 light years (l.y.)
Beyond Our Solar System! Distance from Sun to Center of the Galaxy = 246,000,000,000,000,000 km = 2.46x10 17 km = 28,000 l.y.
Beyond Our Solar System! Distance to nearby galaxies ~ 20,000,000,000,000,000,000 km = 2x1019km = 2x106 l.y.
Beyond Our Solar System! Distance to furthest known galaxies ~ 123,000,000,000,000,000,000,000km = 1.23x1023km = 13x1010 l.y.
Spaceship Earth! We are moving with the Earth.! and not just in one direction! The Earth rotates around it s axis once every day In Florida ~ 960 mi/hr!!!
The Earth orbits around the Sun once every year! 108,000 km/hr (67,108 mi/hr) The Earth s axis is tilted by 23.5º!
Our Sun and the stars of the local Solar neighborhood orbit around the center of the Milky Way Galaxy every 230 million years! (Sun s speed = 600,000 miles/hour) Our Sun moves relative to the other stars in the local Solar neighborhood