What will be the last sign of civilization visible on...

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• What will be the last sign of civilization visible on Earth?

• Where would you leave something to survive the longest? What will destroy it?

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• A moon landing, dark energy, string theory of its time….

The theory of the solar system was recognized as a significant step for the knowledge of mankind

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Doubt thou the stars are fire; Doubt that the sun doth move; Doubt truth to be a liar; But never doubt I love.

Hamlet’s appeal to Ophelia (1603)

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Or if they list to try Conjecture, he his fabric of the heavens Hath left to their disputes, perhaps to move His laughter at their quaint opinions wide Hereafter, when they come to model heaven, And calculate the stars; how they will wield The mighty frame; how build, unbuild, contrive, To save the appearances; how gird the sphere With centric and eccentric scribbled o'er, Cycle and epicycle, orb in orb.

Milton’s Paradise Lost (1667)

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They get their name from an early grand one built for the Earl or Orrery in 1713

The Grand Orrery (before 1733)

6Inside Wright’s Grand Orrery, before 1733

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Orrery:

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David Rittenhouse Orrery 1767

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•The Seasons on the Earth •The Phases of the Moon •Lunar Eclipses •Tides •Solar Eclipses Harvard grads on seasons and lunar phases https://www.youtube.com/watch?v=p0wk4qG2mIg

https://www.learner.org/resources/series28.html

Let’s do a Misunderstanding Check

Seasons

There is a popular misconception that the seasons on the Earth are caused by varying distances of the Earth from the Sun on its elliptical orbit. This is not correct. One way to see that this reasoning may be in error is to note that the seasons are out of phase in the Northern and Southern hemispheres: when it is Summer in the North it is Winter in the South.

The primary cause of the seasons is the 23.5 degree of the Earth's rotation axis with respect to the plane of the ecliptic. This means that as the Earth goes around its orbit the Northern hemisphere is at various times oriented more toward and more away from the Sun, and likewise for the Southern hemisphere, as illustrated in the following figure.

The Seasons in the Northern Hemisphere

Thus, we experience Summer in the Northern Hemisphere when the Earth is on that part of its orbit where the N. Hemisphere is oriented more toward the Sun and therefore the Sun rises higher in the sky and is above the horizon longer, and the rays of the Sun strike the ground more directly. Likewise, in the N. Hemisphere Winter the hemisphere is oriented away from the Sun, the Sun only rises low in the sky, is above the horizon for a shorter period, and the rays of the Sun strike the ground more obliquely.

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• Sometimes, you can look down to astronomy! • The Barrington Crater in Arizona: a 50m nickel

iron meteor made this crater 1.2 kilometers across

Astrobleme: “Star Wound”, see at www.worldwidewords.org/weirdwords

On to Meteors

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Meteor showers

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Name Date Meteors/Hr Parent of Max at Max Quadrantids 4Jan 110 -Perseids 12Aug 68 Comet 1862 IIIOrionids 21Oct 30 Comet Halley Leonids 17Nov 10 Comet P/Tempel-Tuttle- Geminids 14Dec 58 3200 Phaethon

Parent comets of showers

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• Aristotle said that all things that changed had to be within the lunar sphere ▪ Therefore meteors had to be “atmospheric

phenomena” or just another aspect of weather

Meterology is weather?

21Diameter 1.186km, age 49,000 years

Attitude persisted w. Meteor craters

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• 17 km, 200 million years

Aorounga, Chad, Africa

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• 0.875km 300,000 years

Wolfe Creek Australia

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• 2.5km 5 +/- 0.3 Million years

Roter Kamm, SW Africa

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• 28 km, 38 =/- 4 Myr • Horseshoe island in the middle is part of the

central uplift

Mistastin Lake, Newfoundland and Labrador

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Others in Canada and Australia

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Larger craters (>2-4 km) have a complex structure

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• Northern Canada and Australia have the most?

• [Reason is something other than former British • Colonies that talk funny…]

Why are there more craters in some places that others?

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Chicxulub in the Yucatangravity and magnetic variations the dinokiller

Energy scale…

• Car moving at 75 mph 106 joules• 100 watt lightbulb burning for a day 107 joules• 747 cruising 3x1010 joules• Energy content of 747 fuel 1013 joules• 1 Ton TNT 4x109 joules• Hiroshima bomb 6 x 1012 joules• Biggest nukes 1016 joules• Arizona meteor crater event 1019 joules

– 50m nickel-iron -> 5 x 104 kg @ 30km/s

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Jupiter’s moon Calisto

Photo taken by Voyager 1 in 1979

Crater chains…

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Comet Shoemaker Levy 9 The String of Pearls Comet…

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Comet Shoemaker Levy 9 The String of Pearls Comet…

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This chain lies within the large lunar crater “Davy”

Crater chain on the Moon

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Chain on Ganymede

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SL9 collided with Jupiter July 16-22 1994

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• Early pioneer proposing meteor craters as impact craters (rather than thinking they were volcanic) Princeton PhD Thesis 1960

• Discovered SL9 -- the first object with to have it’s orbit followed to an impact with a planet

• First person to be buried on a solar system object other than the Earth (the moon) in 1999

Eugene Shoemaker (1928-1997)

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Crater chains on the Earth: Missouri

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• 17 km, 200 million years (Radar images)

Chain in Aorounga, Chad, Africa

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Coesite: a quartz that forms quickly under extremely high pressure, diamonds are also found

Materials near Craters…

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Iron Spherules rich in NickelMaterials near Craters…

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Rock Flour (not unique to meteor craters)

Materials near Craters…

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Shattercones, the points radiate outward from the direction of the shock

Materials near Craters…

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Earth Impact Database

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North American impacts

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European Impacts

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These are just several grams…

Fireballs!

The Rhyme of the Ancient Mariner

The upper air burst into life! And a hundred fire-flags sheen, To and fro they were hurried about! And to and fro, and in and out, The wan stars danced between

And the coming wind did roar more loud, And the sails did sigh like sedge; And the rain poured down from one black cloud; The Moon was at its edge

Types of Meteorites

• IronPrimarily iron/nickel“M” type asteroids

Stony IronMixtures of iron and stony

materials“S” type asteroids

Types of Meteorites

• ChondritesSimilar to the crust of the

terrestrial planetsMost meteorites..

Cabonaceous ChondriteSimilar to the Sun, less

“volatiles”“C type” asteroids

Martian rocks!

Achondrites!

Similar to Earth basaltMartian and lunar origin

Meteorite Statistics

Type Fall % Find % Fall Weight Find Weight Stony 95.0 79.8 15200 8300 Stony-Iron 1.0 1.6 525 8600 Iron 4.0 18.6 27000 435000

Finding meteorites: The Anarctic

1. Meteors are the main source of rocky material on the ice sheets

2. In places, the movement of the ice sheets tends to concentrate the accumulated load

Meteors from the Moon and Mars

• Impacts on both toss material into space (not much atmosphere), these can become meteorites on the earth

The object on the right came from Mars and was found in Anarctica and launched a controversy when some scientists claimed that it showed “microfossils, Next two slides zoom in on claimed features. The largest is 1/100th the diameter of a human hair! They found some organic molecules in the object as well. It landed in Anarctica 13,000 yr ago after becoming dislodged from Mars 16Myr ago

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Four kinds of Features• Carbonate globules. Carbonate is abundate in non-living

materials, but the “patterns” looked like ones that bacteria make

• Polycyclic aromatic hydrocarbons: Mars origin or Anarctic? Living on non-living?

• Magnetite globules: created by living and non-living chemical processes, on the earth, only living processes had been seen to create “teardrops” (no longer true)

• Microscopic fossils: “the worms”. No known fossils as small on the Earth (1996), but now some are known. But, there are things called “foolers” in earth rocks

Fantastic Debate!

• What are “signs of life”• How could the features come about if they

were/weren’t life• Formation of complex organic molecules

(mostly PAHs)

A Piece of Asteroid Vesta?

Object to the right was found in Australia, almost entirely pyroxene (created in lava flows on the earth) Jupiter slingshot!

Vesta (325 miles across) is the 3rd largest main belt object and the 4th asteroid discovered.

Other small asteroids around Vesta are loaded with pyroxene and likely “chips”

1.4 lbs 3.7 x 3.4 x 3.1 inches

A micrometeor trapped in “aerogel”

Track is .05 inches long

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Comet dust in aerogel

Aerogel is 99.8% “air”

Comet Wild detector on StarDust

• One side exposed to comet, the other side to general dust field

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Stars and the Celestial Sphere

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Constellations….

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The Big Dipper Is part of Ursa Major. It’s an “asterism” not a constellation

The most famous one isn’t!

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Within the Big Dipper, distances range from 53 light years to 360 light years

They are not physical groupings

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•After all, it’s Biology, psychology, philology, …

•Well, astrology is taken for something else

•So, Astronomy means “naming things in the sky”

•Being replaced by Astrophysics…

Why Astro”nomy"?

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Star names are a tribute to the power of Science and Astronomy in the Medieval Arab world

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Clustering• Are

constellations rational? E.g. can you separate the stars into constellations with an algorithm?

minimal spanning tree

• only a couple stars get placed in wrong group

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Solar and Sidereal Days

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Like a toy top, the spin axis of the Earth precesses Polaris is the “pole star” because the pole points

that way; for now! In 13,000 years, it will be Vega, in 26,000 years,

back to Polaris

The Precession of the Earth

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• All positions change, so any stated position needs to have “an epoch” attached, precision measurements require calculating the precession to the moment

The Celestial Equator changes as well

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With the precession, the orientation of the tilt changes altering when “spring” occurs

The Age of Aquarius

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The Sun is currently in Pisces at the Vernal Equinox, but it’s moving to Aquarius 150-300 yrs away..

The Age of Aquarius

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Horoscopes use the star signs fixed at the time of the Roman empire, about 2,000 years ago, since this is a little less than 1/12th of 26,000 yr precession, signs have shifted by about “one sign”

Star signs have changed by ~1 sign

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• 1672 Cassini in Paris and a colleague in French Guiana observed the angular difference between Mars and a star “nearing occulation”

• His value of 140,000,000 km is close to the modern value 149,597,870.691 km

• In contrast, the “ancient methods” gave numbers like 8,000,000 km (Tycho) or 24,000,000 (Kepler)

Measuring the parallax of Mars

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• Transits of Venus • Stellar occulations by the planets • Well, heck, now RADAR!

The most accurate methods use

Determine the distance using parallax

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• Tycho was a fabulous systematic observer • But, he rejected the Copernican model because

he couldn’t detect parallax (shades of Aristotle) --- the stars are so far away that it’s hard!

Tycho’s rejection of Copernicus…

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• Naked Eye Supernovae • “Guest Stars” • In another galaxy, can be as bright as the rest of

the galaxy

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July 4 1054AD, Chinese records show SN, 4 times brighter than Venus, near the moon as shown in Chaco Canyon

Creation of the Crab Nebulae

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Pulsar bubble in SN recorded by Chinese in 386AD

Chinese “guest stars”

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• 1572 Tycho

• 1604 Kepler

• 1987 SN in the LMC

• Contradicted Aristotle who said all changes must occur within the lunar sphere!

• Nominal SN rate is 1/75 years in a galaxy the size of the MW

Supernovae with the Naked Eye!

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• Year Date Con RA Dec mag Comment/SNR --------------------------------------------------------------------

185 AD Cen 14:43.1 -62:28 -2 (-6 mag acc. to Sky Catalog 2000) SNR: G135.4-2.3/RCW 86 393/396 Sco 17:14 -39.8 -3 3 radio sources candidates 1006 Apr 30 Lup 15:02.8 -41:57 -9+-1 SNR: PKS 1459-41 1054 Jul 4 Tau 05:34.5 +22:01 -6 M1 1181 Aug 6 Cas 02:05.6 +64:49 -1 3C 58 Chinese and Japanese 1572 Nov 6 Cas 00:25.3 +64:09 -4 Tycho 1604 Oct 9 Oph 17:30.6 -21:29 -3 Kepler 1680? 1667? Cas 23:23.4 +58:50 6? Cas A SN

About 9/10 more “questionable” ones

Good records of SN in the MW