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.

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.

- 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.

- 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. **


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.