Medieval And Modernpeel/CPSP119D_101/content/Comets.pdf3 How to make a Comet Sun, or planets, warm...
Transcript of Medieval And Modernpeel/CPSP119D_101/content/Comets.pdf3 How to make a Comet Sun, or planets, warm...
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Medieval1
And Modern
Location?
Composition?
Temperature?
Shape?
Size?
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What?
Where is a comet located?
What is a comet made out of?
What does a comet mean?
Why?
Answers to the above is part of your world view
Answers to the above can change your world view
How?
Pure reasoning
Some observations & GEOMETRY (towards the end)
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As with anything medieval have to start with the Greeks and the Romans
Aristotle!!!
Comets are described
Not in De Caelo, which describes heavenly bodies (supraluna)
But in Meterological which describes terrestrial things (subluna)
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How to make a Comet
Sun, or planets, warm the Earth
This causes the evaporation of dry warm exhalations
These rose until came in contact with the fiery sphere (potential fire)
A comet is born
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A Comets motion is a result of being dragged about the Earth by the rotation of the fiery (celestial) sphere (Earth stays still.)
Comets foreshadow: Winds
Drought
Because those are the very conditions that give rise to comets!
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Comets are described
Not in Almagest, a scientific work of celestial motions
But in Tetrabibloswhich describes the astrological influence of celestial bodies on terrestrial matters
Why?
Why not a celestial body?
Why in astrology section?
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Stars
Regular motions, can set your clock by them
Point sources of light
Planets
Wander with respect to stars
But can predict their position
Confined to one belt in the sky
Point sources of light
Stars and Planets Don’t Change!!
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Comets are totally irregular
In timing
Can’t set your clock by them, move with respect to stars
Can’t predict when you can see one
In appearance
If have seen one then have just seen one, not all.
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Not point sources of light
Fuzzy patches of light, sometimes with tails
Change in appearance during passage
There are other fuzzy patches of light: The Milky Way
But it has a regular motion
Constant shape and brightness
Comets Change!!!!
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Stars and Planets Don’t Change!!
Comets Change!!!!
Does stuff on the Earth Change or not Change?
Therefore
Stuff in sky is NOT like stuff on Earth
Comets change like stuff on Earth
Comets must be on (close to) the Earth
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Because comets were unusual they were mysterious signs or portents of evil
Divided comets into 9/10 categories based upon shape/appearance
Though could not predict, could interpret Part of sky and the direction the tail pointed in showed where the threatened area was
Shape of comet suggested nature of evil Length of tail corresponded to duration of ill effects Position relative to Sun foretold how soon evil would strike
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Albert Magnus (1193–1280) Comets are: A coarse, terrestrial vapor
Gradually rose from the lowest part of the airy region to the upper part
When it touched the fiery sphere it ignited
Comets were: Signs of bad things
Not causes of bad things
I wonder who he read in school?
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The Karpos or Centiloquy Anonymous tract
Had these gems: If a comet moved from west to east, then a foreignenemy would invade the country
If comet was stationary, then the enemy was within the country (civil war?).
If a comet appeared in the sky after the meridian, then disease and death.
I wonder who the author read in school?
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Are comets the cause of the bad things? The Karpos implied they could cause the death of kings or change in rulers.
Or are they the result of evil as suggested byAndreas Celichus? “the thick smoke of human sins… gradually becoming so thick to form a comet…which at last is kindled… by the hot and fiery anger of God”
Or just signs as suggested byThomasAquinas? He listed comets among the 15 signs preceding second coming (end of the world) 15
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Ageidius Lessines (1230–1304)
Observed comets of 1264 in the morning and evening
Suggested that it was one comet
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Paolo dal Pozzo Toscanelli (1397–1482)
Physician and Astronomer
Observed 6 comets
Good news: concerned with accurate cometary positional data
Bad news: perhaps to improve his use of astrology in his medical practice (interesting use of Why?)
More bad news: his observations were apparently unknown until manuscript discovered in 1864
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A lot of these determinations were attempts to answer the question, “Are comets closer to the Earth than the Moon?” or “Supraluna or Subluna?”
Why was this important?
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How would you answer the question, are comets closer to the Earth than the Moon?
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Danish nobleman & astronomer (1546–1601) Observer par excellence
Well supported by the king Had at his disposal about 1% of the income of the Danish government
All of NASA < 1% in latest budget proposal
The man with the golden nose Lost tip of nose in a duel
Over who was the better mathematician
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Observer 1 Observer 2
1 2 3 4 5 6
Positioned observers at two different locations in Europe. Far enough that there was an observable parallax of the moon
They also observed the comet Saw no detectable parallax for the comet Therefore comet was further from the Earth than the Moon
Got a lower bound to the Earth–Comet distance Sometimes just a lower or upper limit is enough to make an impact
In this case the lower bound was enough to shake the Medieval world view
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Science now steadily marches onward!
Right?
Wrong!
A lot of fits and starts
Were some observations of comets parallax that were quite large and had to refute those
How far away is a rainbow?
Despite overturning one long held belief about comets, others remained in place.
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Comets’ role in the early Earth
May have brought water to Earth
May have brought carbon compounds from which life evolved.
Comets have heavily impacted Earth and the other planets
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Oort cloud
Begins past Pluto’s orbit
Extends halfway to nearest star
Divided into two
Outer Oort Cloud – Spherical
Inner Oort Cloud – Disk like
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Kuiper belt Around about Neptune’s orbit
Pluto best known member
Jupiter family Periods 5 to 10 < 200 years
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Nucleus
Inner core of comet
2 to 10 km across (1 to 6 miles)
Coma
Gas and dust cloud surround nucleus
10,000 to one million km across (6,000 to 6,000,000 miles)
It is the visible “head” of a comet
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Tail overall Starts to form about the orbit of Mars 1 million to 100 million km long (600,000 to 60 million miles)
Dust tail Small particles blown off nucleus Affected by gravity and radiation pressure
Ion tail Composed of charged gas molecules and fragments Affected by the solar wind
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Nucleus Dust Tail
Coma Ion Tail
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Comet Borrelly
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Comet Halley
Comet Wild 2
NASA/JPL
Comet Wild 2
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1 km
Comet Tempel 1
44Twenty-four hours before impact
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Ejecta plume formation with time
4 July 2005
Dirty snowball or snowy mudball? Equal volumes of ice and dirt
Dirt mass 2 to 5 Ice mass
Ice is 80% water ice
The following have been observed in comets:Water Methane Methanol Acetylene
Ammonia Silicates Carbon monoxide
Hydrogen Cyanide Carbon Dioxide
Ethane Misc. organics
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In the Oort cloud
7 K or –447 ºF
Inner solar system
Surface
Water ice sublimation regions about 200 K or –100 ºF
Black part about 350 K or 170 ºF
Core
Less than 200K (–100 ºF) or comet explodes
Maybe 70K (– 334 ºF)47
Pass within a few radii of the Sun
Look at observations made by SOHO Solar HeliosphericObserver
A satellite whose job is to watch the Sun
One family of comets accounts for about 90% of all SOHO sungrazers Formed from a monster original comet 120 km (75 miles) in diameter
Broke in two chunks 10,000 years
Fragmenting ever since
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Oral part Presentation time 15 minutes Everyone must speak
Accompanying write up 10‐12 pages in length Use a word processor, 12 point font type, Double spaced Paper copy & Electronic Copy Make sure answer What, Why and How! Who did what Honor pledge
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Remember part of your grade are your critiques of the other presentations!
As you do your research Be aware of potential bias in numbers (Columbus)
Check for internal consistency
Are numbers too good to be true?
Primary vs. Secondary sources
Multiple sources
Do the math yourself!
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Disclaimer: The standard is different in different fields. These are some general pointers. Slanted towards technical talks.
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What is the purpose of your talk? To inform
To persuade
What is the type of talk? Group or panel presentation
Informal meeting within your organization / group
What is their background? How much do they know already about the topic?
How much to they think they know about the topic?
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Know your time limits (15 min.) ‐ it affects how much you can present (PRACTICE YOUR TALK!!)
Make eye contact around the room Remember while slides behind you audience is in front of you
Always fun to see who is asleep, reading the newspaper, texting, doing Sudoku, homework, etc.
Try not to read your presentation (practice!) You can write yourself notes, though
Learn the standard in your field, it varies
Speak slowly, enunciate and project! (Do as I say, not as I do)
Relax, almost everyone hates it at first!
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Title and authors, date, affiliations
Overview/outline ‐ for talks > 30 mins.
Just summarize main topics for shorter talks
Details ‐main part of the talk
Summary ‐ restate your results
Conclusion or future work to be done
Graphics Figures are great! Much more easily interpreted by the audience than a table with the same information.
Make sure the figures do explain what they are showing, though– Don’t include TOO much information
– Label axes
– Color code points
– Error bars!
Don’t show pages of equation derivations (except in a class that requires them!) or big tables of unreadable numbers.
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Text
Make sure your text is readable far away
Can use fonts to emphasize points but a few readable fonts are better than Many (ditto for animations and
effects)
Color is good, but:
– Avoid colors that don’t show up well against the background
– Example: Yellow on any “blank” transparency, dark coloron dark background
Try to avoid very busy slides, i.e. lots of graphics and text
How many?
Good rule of thumb 1 slide per minute
Always have some you can add/delete
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The paper is NOT your talk notes Complete sentences
Complete paragraphs
NO BULLET POINTS
Electronic and paper copy
References Should be listed in paper at end
Should be cited in paper somehow Numbers
(First author, year published)
(Book Title)
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Proofread Done by someone who did not do most (all) of the writing
Read it aloud to the group by someone who did not do most (all) of the writing
Helps catch missing words and the dreaded spell check gaff, e.g. Alpha Century for Alpha Centauri,start for star, defiant for definite
Remember honour pledge and all must sign
List of who did what!