ASTROBIOLOGY CLASS NEWS


Due to the COVID-19 virus pandemic, all lectures for this class will be on-line only and accessable via Blackboard.
For this class, you will be able to view the class lectures, recorded from last spring, via Blackboard. Written homework will be uploaded via Blackboard, and the exams will be administered via Blackboard. See the Blackboard announcements for this class for more details.
Some COVID-19 links:
SDSU Coronavirus (COVID-19) Academic Continuity Preparation
SDSU: The Coronavirus (COVID-19)
San Diego County Government Home: Coronavirus Disease 2019
Center for Disease Control and Prevention (US CDC): Coronavirus Disease COVID-19


+ Astrobiology Magazine is a superb on-line astrobiology news magazine.
For the written homework, you may use these sites as well:
NASA's "Exoplanet Exploration News" and also "Astrobiology at NASA" Life in the Universe: News & Discoveries.
Here is another good astrobiology site: + NASA's Astrobiology Portal
+ A nice "zoom" on the Universe: "Powers of Ten" from "Molecular Expressions".
+ Another, very nice up-to-date "zoom" on the Universe: Scale of the Universe 2 by Cary and Michael Huang. You drag the scroll bar to zoom in/out, and you can click on the different objects to get more info.
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FINAL EXAM: Monday May 11, 10:30-12:30

Here is the final version of the Final Exam Study Guide and Instructions.

As we head into the finals, the stress levels can be high. If you, or a friend, are feeling way over-stressed, maybe talking with a counselor can help: SDSU Counseling Services

The course is now over (except for the final exam!). Thanks to all who contributed to the success of the course this semester via your good questions in class, sending me links to interesting websites and videos, and our discussions during office hours. If you enjoyed this course, let your friends know about it. I teach this course every spring semester.
Best wishes, and good luck with the rest of your SDSU activities and post-graduation careers.
- Prof. Welsh


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May 6:
- To help you study for the final exam, here are the answers to Homework #3 Multiple Choice Questions
- Here again is the DRAFT version of the Final Exam Study Guide . It is about 95% on-target for this semester, but final tweaks will be made by May 8th, once I finish working on the final exam questions.
- The homework will be graded as soon as possible and the scores posted on Blackboard. HW#2 has not yet been fully graded.

May 5:
- A "big picture" review/summary of the course:
The Big Picture
- Reminder: Final Exam is Monday May 11 at **10:30 am**.
- Repeat link: What is astrobiology?
- Here is the final set of Teach Yourself excercises and problems to help you to prepare for the final exam: Teach Yourself.
- Released last spring: the United Nation's Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services summary statement: Nature's Dangerous Decline Unprecedented; Species Extinction Rates Accelerating "Nature is declining globally at rates unprecedented in human history - and the rate of species extinctions is accelerating, with grave impacts on people around the world."


tardigrade
May 1:
* Revised version of Final Exam Instructions and Study Guide. Please read the instructions carefully and note that you will need Zoom *video and audio* to take the final exam.
+ Lecture notes on: The Rare Earth Hypothesis & Some Critical Thinking Topics
- A brief written explanation of The Drake Equation from Drake himself, who works at the SETI Institute.
- A TED video about the Drake Equation: Calculating the odds of intelligent alien life, a TED video by Jill Tarter of the SETI Institute.
- Another TED video: A needle in countless haystacks: Finding habitable worlds by Ariel Anbar.
- Take a few mintues and check out the NASA Exoplanet Exploration website. It is a nice review of some of what we've learned in this course, espcially the "Alien Safari" section.

Apr 27:
- A (partial) summary of the Kepler Mission: Kepler has Taught us the Rocky Planets are Common
- Here again is a short video on how astronomers discover extrasolar planets. In particular, the bit about the Doppler effect is pretty good:
NBC Learn Science Behind the News: Extrasolar Planets
- Here is link to SDSU's NewsCenter that highlights some of our work on exoplanets
- For those of you who want an local "insider's" thoughts about the Kepler Mission project, you can check out this article from a few years ago on SDSUniverse: "Searching for Other Earths: The SDSU-NASA connection". And some of you might enjoy this 2010 article in SDSU's 360 Magazine "Welcome to the Galaxy", with some footage shot in the Astrobiology class of 2010 spring semester. (And here's the same video "Welcome to the Galaxy" on YouTube).
- Here is an "old" article from the Astrobiology News archives about circumbinary planets: Kepler Finds Two-star Planetary Systems Are Common that you might find interesting... I did!
Speaking of circumbinary planets, here's a much more recent article from last spring: SDSU Researchers Discover New Planet in the Daily Aztec newspaper.
Not recent enough? Here's one from this semester: NASA's TESS Mission Uncovers Its 1st World With Two Stars
* Beta version of a *DRAFT* Final Exam Study Guide from last year

Apr 20:
Please join us on Wed and Friday this week at 11am for a live guest lecture by Earl Towson, speaking to us about the latest discoveries on Mars. Zoom Meeting info and password will be sent via Blackboard.
+ For HW #3, make sure your answer connects together your image to astrobiology, and in particular, the biology part. Ask yourself this question: "How does this relate to biology?" If you can't answer that, then you probably have chosen a bad image to use. Think of NASA's Astrobiology Roadmap, and how your image is connected with those goals and questions.
* The extra credit assignment from the video clip from The Day the Earth Stood Still shown at the ends of the discussion of the icy moons is due with the Homework #3 (attach at the end). You can find more information in the
Teach Yourself #9. As usual for a scholarly work, to earn credit you must have proper references. Length should be about a page.

Apr 15+:
We are covering Mars and the icy moons this week and next, but are all the lecture notes for the rest of the semester, except for the last class, so that you have these in hand when watching the on-line lectures.
+ The Rare Earth Hypothesis & Some Critical Thinking Topics
+ The Drake Equation and SETI
+ Exoplanets Please be sure to update these notes in particular to reflect the many recent discoveries: its an indication of how fast this field of science is moving. I have left these notes as they were, just so that we can really see how far we have come - it is astonishing!
+ Here again are the lecture notes on: Doppler extrasolar planets.

- Lecture notes on the Icy Moons
Recent news about Enceladus:
Astro Update: All That Life Needs on Enceladus
NASA Missions Provide New Insights Into Ocean World. In particular, the Cassini Mission has found that in addition to water vapor, there is evidence for hydrogen gas, carbon dioxide, methane, and ammonia in the plumes. The hydrogen is particularly significant in that it suggests a reducing chemistry and a source of chemical free energy that could be used by life.
Some older articles about Enceladus:
- How Friendly is Enceladus's Ocean to Life?
- NASA's Cassini Discovers Potential Liquid Water on Enceladus
- Searching for Life in the Depths of Enceladus
- A Hot Start on Enceladus: "Deep inside Enceladus, our model indicates we've got an organic brew, a heat source and liquid water, all key ingredients for life... we probably have evidence for a place that might be hospitable to life."
- An old but good article about why "Jupiter's moon Europa should be NASA's next target"
Astro Update: Water plumes and the search for life on Europa
- A short 2 minute video about the Ingredients for Life at Enceladus

Very Special Offer: Here is a opportunity for a student with sufficient time to devote to this project to earn a significant amount of extra credit. Partial credit can be earned for effort. "Successful" means your proposal is submitted to NASA/JPL and you share the motivation and results in class. See the article in Astrobiology Magazine published on 2010 Jan 29 called Pick a Pixel on Mars. The idea is for you to actually determine what part of Mars will be photographed and examined with the high-resolution imaging camera called "HiRISE". HiRISE is part of the MRO mission, a NASA satellite currently in orbit around Mars. Originally called "Pick a pixel", it is now called "HiWish". See me for details once you get started on this. And yes, I have had TWO students who were successful with this - both had high-res images taken of Mars at the exact coordinates they specified! One was a cliff region, the other an icy crater. Very cool!

- Exam #2 results: average was 43.2/50, median was 44; class average grade was a B+. Here is the detailed score-to-grade conversion curve:
A >= 46
A- > 44
B+ > 42
B >= 38
B- = 36
C+ = 34
C >= 30
C- = 28
D+ = 27
D >= 25
D- = 24

April 11+:
- Meteorite Action! is a website showing photos & videos of meteors (this link was found by a former student - thanks!). The website is not being updated anymore, but it still has nice content.
- What is "Apophis"? It is a NEO and ``...in 2004, Apophis was briefly estimated to have a 2.7% chance of impacting the Earth in 2029...''
- From NASA's NEO Program website: Near-Earth Object Testimony before the U.S. House of Representatives Subcommittee on Space and Aeronautics. In particular, see the link to the Apophis' 2029 and 2036 threat.
- Diverting Dangerous Asteroids from Astrobiology Magazine.

+ Lecture notes on: Mars, Part 1
+ Lecture notes on: Mars, Part 2
- Here are some old, but good, articles about water on Mars (from Astrobiology Magazine):
+ + Opportunity Finds Beachfront Property on Mars The rocks ... "were not just altered and modified by water; they were actually formed in water, perhaps a shallow salty sea, ..."
+ + Martian Salty Sea "...some rocks on Mars probably formed as deposits at the bottom of a body of gently flowing saltwater."
+ + Here is a more recent summary from The Atlantic 2,000 Days on Mars with the Curiosity Rover



April 8:
+ Here is the final version of the Study guide for Exam #2.

April 5:
- Here are the answers to HW #2 multiple choice questinos to help you prepare for the exam coming up on the Friday after spring break.
- Exam #2 will be on-line and time restricted - the exam will take place at the regularly scheduled class time (11 am on Friday). If you can't make this time, please let me know in advance. The exam will be open-book, open-notes, etc. The exam will be administered through Blackboard. More info will be posted later.
- Lecture notes on: Jovian Planets, Meteors & Comets
- Lecture notes on: Chicxulub & the K-T extinction.
- After talking about the Earth's core-mantle-crust structure, a student from a few years asked, "What is the deepest we've ever drilled into the crust?" Here is the Wikipedia article on the Kola Superdeep Borehole, a USSR project to drill into and study the Earth's crust. In 1989 the geologists bored 12.3 km (7.6 mi); this is the deepest humans have reached below the surface. This was a very good question. Please keep asking questions - that's how we learn!

March 27 - for over spring break:
+ Please watch the PBS documentary Your Inner Fish (Episode 1) by Neil Shubin. You can get this in high-def from the PBS website, though you have to do so in 16 short segments (argh!). Luckily there are other options, like the resource available at the Howard Hughes Medical Institute BioInteractive site Episode 1: Your Inner Fish. At this hhmi website, click on Play Episode 1. Alternately, perhaps you can find the full 55-min video on the web somewhere (possibly from "Dailymotion").
- The Solar System, and hence the Earth, is known to be about 4.54 billion years old. This is based on the age of meteorites and rocks from the Moon. But how do we know the age of these rocks? We use a technique called "radioactive dating". (No, this isn't about your ex-boyfriend/girlfriend ...). The textbook discusses this on pages 111-115. Also, see the Teach Yourself #6 notes for more about radioactivity.
- Exam #2 on Friday April 10. Here a DRAFT preliminary version of Study Guide #2.
+ Thinking about viruses again.... Are viruses alive? Are they the Fourth Domain of Life on Earth? Here is more information about viruses, from Astrobiology Magazine.

Mar 26-27:
+ As a reminder, if you want (or need) alternates to Astrobiology Magazine for Written Homework #2, use the links to sites listed near the top of this webpage.
+ Lecture notes (for after spring break): The Earth's interior and The Earth's atmosphere
+ Speaking about viruses....
-- Giant Viruses Shake Up the Tree of Life, a nice article from Astrobiology Magazine.
-- A not-too-old (2008) news on viruses and their possible association with the "RNA World" hypothesis: "Seeing Life in Viruses" from Astrobiology Magazine.

+ Astro Update: How Old Is Life On Earth?
+ World's Oldest Fossils Unearthed

- For a bit more on the Surveyor 3 & Apollo 12 Missions see these two webpages: Man and Machine on the Moon and also see:
Footpads and Footprints: Humans and Machine Meet on the Moon

Mar 20:
- From NPR Science Friday: Behold the Mighty Water Bear:

- Interested in knowing more about the complex and wonderful biology of water bears? Check out this report from one of your classmates: The Amazing Tardigrade
- And here's a YouTube video about Tardigrades: Adorable Extremophiles suggested by one of your classmates.

Mar 18
- Written Homework #2 is now due on Friday March 27th.
- Hint for answering Part 3 of the homework: - the article must have been published after Feb 16.
- must list the title and date published
- must list the full web address (the URL)
- must list the author, if there is one
- no spelling errors and no grammar errors
- write clear, unambiguous sentences
- answer the usual "who, what, where, when, and why?" questions
- provide sufficient detail; do not be vague and do not be overly terse
- keep your own personal opinions and thoughts separate from those of the author; that's why we have two separate paragraphs.

Mar 14: PART 3
- Please note the typo and correction for Written HW #2: Only news articles published after Feb 16, 2020 are allowed.
- For Written Homework #2, for the Astrobiology Magazine questions, you can also use this website for the homework: "Astrobiology at NASA" Life in the Universe: News & Discoveries
From the good old Astrobiology Magazine archives:
- - Looking Back 3.8 Billion Years into the Root of the Tree of Life.
- - Thriving in Battery Acid and Toxic Metals
- A nice historical perspective on the discovery of the domain archaea: "30 Rings on the Tree of Life" from Astrobiology Magazine.

Mar 14: PART 2
- Lecture notes: Comments on the Origin of Life on Earth
- NOTE: The genetic code the table in the textbook Fig 5.17 (on page 180) is non-standard! It lists the DNA codons, not the RNA codons. Be very careful using this table.
- Please be sure to understand how the genetic code works. If you are not 100% confident, please ask. For example, if you had the genetic code in front of you and I asked, "What are the RNA codons for arginine?", could you answer this question correcly? Would you get *all six* codons?
- From Astrobiology Magaine: "Despite its impressive biological resume, phosphorus is relatively inaccessible as elements go. To understand how phosphorus obtained its prominent role, scientists are modeling the early geochemical environment on Earth and in space." Life's First Taste of Phosphorus

Mar 14: PART 1
- : Due to the COVID-19 virus, and out of an abundance of caution, SDSU will be switching to on-line only lecture classes effective March 16.
- Lecture Notes on: The Tree of Life
- How Life Shatters Chemistry's Mirror (Astrobiology Magazine), an article on the handedness of biomolecules. Besides being cutting-edge news, it contains good review material for this course.
- Regarding the organic material in meteorites that may have been the source of the building blocks of life: Meteorites a Rich Source for Primordial Soup.
- The dispute about a claim of a discovery of a form of life that uses arsenic instead of phosphorous seems to be over: no substitution of arsenic for phosphorous. (Recall that phosphorous is the "P" in CHONPS.) "Arsenic Life" Needs Phosphorus After All
- And Happy Pie Day (March 14th = 3.14)

Mar 11:
- : Due to the COVID-19 virus, and out of an abundance of caution, SDSU will be switching to on-line only lecture classes. For this class, you will be able to view the class lecures, recorded from last spring, via Blackboard.

Mar 9:
- Lecture Notes on: Organic Molecules: The Molecules of Life.
- Lecture Notes on: The Tree of Life
- Why Silicon Aliens Would Rather Eat Our Cities Than Us from Astrobiology Magazine.
- And yet.... some exciting research about combining carbon and silicon: Possibility of Silicon-Based Life Grows.
- Reminder: If you find a mistake in the textbook that I don't already know about, I will award you an extra credit point. Like most textbooks, their are misteaks. (sic)
- Here's a link to the opening sequence from the film "Contact" based on the novel by Carl Sagan. If any part is puzzling, please ask.
- Unfortunately we did not get the extra credit bonus point had everyone properly filled out scantrons - sigh. (Extra credit to anyone who can come up with a really good way to solve this problem!)
- Exam #1 Results: mean score = 39.7 / 40.0, median=39, mode=42. Approximate score-to-grade conversion (details were given in class):
... A = 44-50
... B = 37-43
... C = 30-36
... D = 23-29. The grades are based on a curve, but the curve was very similar to curves from previous semesters.

Mar 6
- Lecture Notes on: Organic Molecules: The Molecules of Life.
- An old, but interesting website: What Have We Done For You Lately? NASA Connections to Everyday Life. A more up-to-date brochure Spinoff (2015), documents some of the most recent technological advanced that NASA has made and how they affect all our lives in health & medicine, safety, transportation, energy, etc.
- This July will be the 51th anniversary of the historic Apollo 11 Moon landing! Read more about it at NASA's Apollo 11 site.
- Note that NASA's old "PlanetQuest" website is now called Exoplanet Exploration

Mar 5
- Fill out the basic info on your scantron form: see instructions below. Be sure to fill in Exam 001, not 002 as it shows on the image.
figure of a correctly filled-in scantron form
There are 50 multiple choice questions; you need a ParSCORE Student Enrollment scantron form (the big pink one), #2 pencils, eraser. No iPads, cell phones, netbooks, etc., allowed. (No calculators are allowed.)
- Be sure to fill out your ParSCORE form correctly! You will lose points on your exam for not filling out the information properly (1 point per error). Common errors include:
. + putting an extra zero in front of your Red ID
. + putting a blank in front of your Red ID (leave the last column blank)
. + filling in wrong digits on your Red ID.
. + not filling in TEST FORM A
. + not filling in EXAM # 001
*** Please fill in your scantron information BEFORE the exam. ***
- If everyone fills in the scantron info correctly, I will award the class an extra credit point on the exam!
- Final Version of Studyguide Hints for the first midterm. There have been no changes since the earlier draft version.
- Here are the exact instructions for the exam:
INSTRUCTIONS:
Completely fill out the ParSCORE Enrollment scantron form. Be sure to include your Red ID on the back as well as the front, and don't add a leading zero to your Red ID -- leave the 10th block blank. Leave the phone number and `code' part blank. On the back, fill in `Test Form A' and Exam # 001. You will lose 1 point for each error on the form!
Use a #2 pencil only. Darken completely, and erase thoroughly if you change your answer. Be careful not to darken two answers.
There are 50 questions. Choose the best answer --- the questions are not designed to be tricky. You may leave anytime you are finished, but please be considerate and be quiet if you finish early. If you are confused by any question on the exam, please raise your hand to get help. It is too late to ask for clarification after you hand in your scantron. ** You may keep your exams to help you study for the final. **
But if you don't want your exam, drop it off and I will recycle it.


Mar 2:
- Exam Information: 50 multiple choice questions; you need a ParSCORE Student Enrollment scantron form (the big pink one), #2 pencils, eraser.
- Be sure to fill out your ParSCORE form correctly! If you have mistakes, you may lose points on your exam (1 point per error). Common errors include:
. + putting an extra zero in front of your Red ID
. + putting a blank in front of your Red ID (leave the last column blank)
. + filling in wrong digits on your Red ID.
. + filling in two answers bubbles because of sloppiness
. + not erasing an answer fully
Be smart: Fill out your scantron form BEFORE the exam.
Calculators not allowed, but slide rules are allowed.
+ Here is a revised updated version of the Draft Studyguide Hints.
- To help you prepare for the exam next week, here are the Solutions for HW#1.
- Note: A bare helium nucleus moving at high speed is often called an "alpha particle", and it is a dangerous form of particle radiation that arises from radioactivity. Radioactivity come from nuclear fission which is the breaking apart of a nucleus - it is the opposite of fusion. Now that you know what an "alpha particle" is, why is the creation of carbon called the "triple-alpha process"? (teach yourself hints)
- A former student suggested we watch this superb YouTube video of Neil deGrasse Tyson talking about UFOs, and I wholeheartedly agree. Its both funny and full of good science nuggets related to what we are covering in class. (If the above link fails or is slow, try this link for the exact same interview ).
+ Lecture notes on: Venus.

Feb 26:
- Lecture notes on: Star & Planet Formation; The Solar System
- (For completeness: The lecture notes on AGN, though we won't cover this topic this year.)
- "More than ever, we'll need to constantly keep in mind that memory, like liberty, is a fragile thing." - Dr. Elizabeth Loftus, as quoted in New Scientist Magazine's story "Elizabeth Loftus forecasts the future" (18 November 2006). For more on the profound work of Dr. Loftus see the ``Critical Thinking, etc.'' section of our class web pages for links to (i) a Scientific American article "Creating False Memories", and (ii) a really fascinating and enfuriating pair of articles titled, "Who Abused Jane Doe? The Hazards of the Single Case History" printed in the Skeptical Inquirer. You can also visit Dr. Loftus' website.
- Special Offer #2: If you read the "Creating False Memories" article by Dr. Loftus published in Scientific American, you can earn extra credit. Turn in a brief summary of the article and your thoughts on what you read. The whole thing should be no more than 2 pages - keep it short and to the point. (Suggestion: Write 3 paragraphs total, 2 on the article and 1 on your opinion.) The minimum extra credit is you will earn is one exam point, the maximum is three points. This is supposed to be a relatively quick assignment so the offer expires Monday March 2. But if you are really hardcore and like learning about this, you can earn up to five points (that's up to 10% of the exam, since the exam is worth 50 points!) by doing more. Look at Dr. Loftus' website, and read more than just the one Scientific American article. In particular, the articles "Our changeable memories: legal and practical implications", and "Make-believe memories" are quite good. The article "Who Abused Jane Doe? The Hazards of the Single Case History" is particularly distressing. Be careful with this one. You can get to Dr. Loftus' website from a link on our class webpage "Critical Thinking, Pseudoscience, Aliens, UFOs, etc.".

Feb 22:
- Lecture Notes on Stellar Evolution
- If you are presenting your research at the SDSU Student Research Symposium and it conflicts with our class, please let me know.
- For those that want some help with any astronomy in this course, there is an Astronomy Help Room, offering free tutoring. It is located in the Physics-Astronomy (PA) building, Room 215-A.
Astronomy Help Room schedule
- Special Offer #1 ("Actors needed for extra credit") is closed.
- *DRAFT* Beta Version 0.1 from last year's class Draft Studyguide Hints for the first midterm exam (Fri March 6). This is NOT the final version; some of the information in here is from a few semesters ago, and it needs to be updated. It is just a guide to get you started. The revised version will be posted later.

Feb 20:
- Special Offer #1 ("Actors needed for extra credit") is still open.
- Here's my cosmological thought of the day:
"Don't think of empty space as nothing;
Think of it as something with nothing in it."

For example, consider time. You can certainly measure it. And you have an intuition of what it is. But try to define it. One thing is for sure: it is something; it is not nothing. Well, that's about as good an explanation that I can offer. The notion of space stretching is not a trivial concept, so don't fret if it doesn't make sense immediately. For some, it will never make sense, and for those people I offer the following thought. Here is a very rough adaptation of a relevant section from Lao Tzu's Tao Te Ching, Book 11 (this not at all an exact translation, but I think it gets the point across):
"Consider the teacup:
It is not the sides of the cup that give its usefulness,
But rather the empty space they create."


Feb 18:
- Teach Yourself (#3): This problem will help you understand the relation between Hubble's law and the age of the Universe:
Suppose the Hubble constant H0 = 750 km/s per Mpc. How old would the Universe be? Do you think this is ok? (Here are hints for the problem.)
- Special Offer - Extra Credit: For those of you who are theater majors, or actors, or wannabe actors, or who just like to talk, I have a job for you. I need two students to act out a very short dialog between two friends. This 1-minute dialog will be in presented in class. I will provide the "script" ahead of time and all you have to do is slowly read it. The first two students who respond to this Special Offer will be asked to perform the dialog and will earn extra credit worth 1 exam point. No acting skill is necessary. (I used to have TA's help me with this, and boy, they definitely could NOT act!) Send email to me if you are interested and I will send you the dialog.

Feb 15:
- Lecture Notes on The Scientific Method and Critical Thinking
- And now, for a detailed view of the Doppler effect....

- Here is a short video on some of the ways astronomers discover extrasolar planets, with an explanation of the Doppler effect:
NBC Learn Science Behind the News: Extrasolar Planets


Feb 14:
- Happy Valentines Day from Mars!
Click on the image to get to NASA's Mars Global Surveyor "Mars Orbiter Camera" website.
multiple images of heart-shaped craters on Mars taken with the MGS
spacecraft
- Who was this guy Bruno that's quoted on the class web page? Read the Giordano Bruno biography from the Galileo Project.
- Teach Yourself (#2): Try working out this problem - it will help you understand the Doppler effect:
The observed wavelength of the H-alpha line in a star is 653.450 nm. The true wavelength of the H-alpha line (measured at rest in the lab) is 656.255 nm. What is the radial velocity of the star? (Here are hints on how to do the Teach Yourself problems.)

Feb 10:
** Because of on-going problems with the Astrobiology Magazine website, for Written Homework Assignment #1, you may choose articles from the following NASA Astrobiology news sites:
** Exoplanet Exploration News and also
** Life in the Universe: News & Discoveries.
- Lecture notes on: Cosmology & the big bang. Remember, all class notes are copyrighted.
- To help clarify Written Homework #1:
(i) You must answer all questions. The length of the homework should be about 2-3 typed pages. The font size or spacing does not matter. It takes some time to write concisely, so don't rush (or leave this to the last minute). Suggestion: write out your answers in full, then go back and edit your answers to shorten them if they exceed 3 pages.
(ii) For the multiple choice questions, you can just write down the letter for the answer, you don't need to write out the entire question. But you can if you want.
(iii) For the problems that require some math, work it out first, then type up the answer when you are finished. For full credit, explain every step that is not just trivial arithmetic. Also, think about the units of your answer. If someone asks, "How long does it take to drive to Los Angeles?" you would not say, "About 11,000 seconds". So always provide an answer in units that make sense.
(iv) For the Astrobiology Magazine question, make sure you give the title and date of the article. Include the URL (i.e. the web address) as well. Put these at the start of your answer, not in a bibliography. Your answer for this part should be about a page in length; no more than two pages please. Answer both parts of the question (in order) and keep them separate - do not mix your opinions with those of authors of the article. Proofread your writing; use a spelling checker. And here's a helpful technique for any writing you do: Read your answer out loud. Does it sound okay? If it sounds awkward or hard to understand, then it probably is not written well and needs work.

Feb 6:
- I need to cancel my office hours on Monday February 10th. To help compensate, I can make extra office hours available on Tues-Thurs (by appointment).
- Lecture Notes on: Doppler extrasolar planets.
- Helpful notes on Wien's Law kindly provided by former astrobio student E. Ross (with some help editing by Prof. Welsh).

Feb 5:
- Please study Chapter 3 - many questions on Exam 1 will come from this chapter. I recommend you read it at least twice. Also try answering all the multiple choice questions. This will help you learn the material and do well on the exams. General suggestion: read many of the questions at the end of the chapter first, then go and read the chapter. This technique helps you learn faster and focus on the most important parts of the chapter. If you have any trouble, just ask for help.
- Here is a 10-minute You Tube video on atomic energy levels to help you undertand the relationship between energy levels and spectral lines.
- An intersting article from Astrobiology Magazine NASA's TESS Mission Uncovers its 1st World with Two Star
- A more home-grown nees story Astronomers Pinpoint Two New Double-Star Planetary Systems

Jan 31:
- Lecture notes on: Spectroscopy.
- Check out the "Powers of Ten" and the "Scale of the Universe 2" web pages (links at the top of this page). They are good tools for helping you grasp the size scales of things in the universe.

Jan 29:
- Lecture notes on: Electromagnetic Radiation.
- If you find an error in the textbook, notes, lectures, or web pages, please notify me and you may earn extra credit. The more important/significant the error, the more likely you are to earn extra credit. Please review the extra credit policy on our class Information and Policy webpage (and repeated below). In general, I don't award extra credit for spelling errors or typos and definitely not for updates/revisions to the Lecture Notes. But any major errors, like an incorrect date for an exam on the syllabus, would certainly earn you extra credit. Also, excellent questions (especially ones that help other students and show that you are really thinking) may earn extra credit.

Jan 27:
- The Where are the Voyager spacecraft? real-time odometer (from NASA/JPL).
- The
Voyager Golden Record Messages From Earth
- Lecture notes:
Parallax, Galaxies, & Large Scale Structure of the Universe.
- Teach Yourself (#1): Try working out this problem - it will help you understand the size and scale of the solar system: What is the minimum amount of time it would take to send a command to a robotic spacecraft on the surface of Europa? (Europa is a moon of Jupiter.) (Here are hints and more "Teach Yourself" problems.)
- SDSU Astronomers Discover Two New Tatooine Planets

Jan 24:
- Lecture notes: Stars, Vastness of Space, Clusters and Nebulae
- Please review the Safety Policies for this Class, and the SDSU Emergency Preparedness website: SDSU Emergency Preparedness.
- For those who want or need a review of some mathematics, please read Appendix C of the textbook.

Jan 22:
- Lecture notes: You should be able to read the class lecture notes (in PDF format) with almost any OS platform (linux/unix, Microsoft Windows, Apple/Mac, Android, etc.). For example, here are notes on the metric SI system and reference temperatures, lengths, and velocities.
- Lecture notes: What is astrobiology?
** NOTE: All class notes are copyrighted. **

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On-line Class Notes Policy:
The on-line class notes are available to augment classroom learning - their sole purpose is to prevent frantic writing of notes and allow students to spend time listening, thinking and comprehending the lecture. They are not intended to be, nor do they function as, a substitute for attending the lectures. For maximum value, you should: (i) read the homework assignments first (especially the textbook & web page reading assignments which cover material well before we discuss the topic in class); and (ii) bring the notes to the lecture so you can add comments, sketches of figures, and material not in the notes. Treating the on-line notes as a substitute for attending class is inappropriate at best and detrimental at worst.
The on-line notes will NOT be available all semester - they are posted several days before the lecture, then removed a few days after the lecture - no exceptions. This is for the students' benefit. So please keep up with the class.

Reminder: The lecture notes, along with all other class material, are copyrighted.

Please don't confuse the terms "hypothesis" and "theory". As used in science, a theory is a very strong term and only a handful of ideas in all of science qualify as a theory. A hypothesis is an educated guess or explanation, and implies insufficient evidence or comprehension for a more concrete understanding. A theory is a well-tested, well-established hypothesis, able to make far-ranging predictions and connections with other theories, and usually with an elegant mathematical or physical mechanism for its operation. A theory is much stronger than a hypothesis. It has been rigorously tested by many independent people. When speaking in technical terms, don't use the word "theory" when you simply mean speculation or conjecture or idea or educated guess (all of which are synonymous with hypothesis). In science-speak, we don't come up with theories, we come up with hypotheses. But that's not the way the word "theory" is used in common conversation. Keep this in mind so you don't get confused when you hear someone say, "It's only a theory." That theory may encompass the sum total of all of human experience and knowledge! A better way to think of the word theory is to equate it with the word "law". That is closer to the meaning that scientists intend when they call something a theory.

Last major update on 2020 Jan 20. Updates occur frequently.