Online reading assignment: cosmology (SLO campus)

Astronomy 210, spring semester 2013
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on evidence for the big bang, and models of the early big bang.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"The acceleration of the universe because I have a personal theory to the origin of existence that uses this as key evidence."

"The history of the big bang and how it developed was really cool because I didn't realize how freaking long it took just to form galaxies, stars, etc."

"Personally I found reading about the Hubble law interesting...how they tried to come up with a concept that explains the size and age of the universe...claiming almost all galaxies appear to be moving away from us."

"I think its interesting that astronomy is full of recently found information. it seems like a pretty new branch of science. There are new things discovered all the time. It must be pretty rad to have the best job security as an astronomer."

"That a lot of stars are dead now but we can still see their light."

"I thought it was interesting learning about the big bang, because I believe that God created Earth. But I am still curious and open about other people's theories."

"That the universe has no edges it is infinite and there is no center, this is just insane to try to imagine."

"I found it interesting because I wasn't aware that the big bang didn't occur at a single place, but filled the entire volume of the universe."

"Olbers' paradox is interesting to me because of how the night sky should apparently be incredibly bright! Of course he was wrong but for Olbers' time he had something there."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Olber's paradox."

"Differences between antimatter, dark matter, and matter. I've read the difference a dozen times but I can always hear it again. And the difference between an open, closed, and flat universe... I wonder if astronomer's are over-thinking things sometimes when the solution is sometimes apparent to even a child."

"It's a little hard for me to wrap my head around how the big bang 'occurred everywhere.'"

"'Edge in time, not space.'"

"I did not understand the 'wall of light.'"

"I was a little confused by the video."

"I'm still a little unsure what caused the big bang to happen."

"How are you looking back in time when you look at space at a great distance? Or is that just a metaphor?"

"Nothing at all."

Briefly explain how it is possible for you to see a star in tonight's sky that may have already died a long time ago.

"Since we're so far away from the star it takes years for the light to reach us."

Describe what will happen when a matter particle and an antimatter particle meet each other.

"They destroy each other and release photons in the form of gamma rays."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"If space/time is infinite, then why is our universe only 14 billion years old? Are we just really lucky to exist, or do we participate in an infinite universe cycle?" (Space (the size of the universe) is understood to be infinite, but time (the age of the universe) is finite.)

"What happens when there's more antimatter than matter?" (Then everything today would be made of antimatter rather than matter.)

"The big bang was probably the most fun part of this class to read about so far." (Cool. Cool cool cool.)

"Since Christianity does not teach the big bang theory, are most astronomers non-Christian or do those believers just have to have an open mind and accept the theories of the big bang?" (The big bang was originally proposed by a Catholic priest.)

"The Madonna Inn has good apple pie and coffee." (Damn straight.)

Online reading assignment: cosmology (NC campus)

Astronomy 210, spring semester 2013
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on evidence for the big bang, and models of the early big bang.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"The tale about the crocodile and the elephant's trunk was cool to read about, even though there is no evidence that it ever happened."

"I found Olbers' paradox very interesting because it would make sense that the night sky should be bright like daytime because of the astonishing amount of stars in our universe, one would think that the night sky would be so covered that it would be blinding."

"The video, it helped me understand why it is dark at night."

"I thought it was interesting that the universe doesn't have an edge. There really is no center to the universe or at least that is what the introductory chapter said. That is pretty cool to think about. The universe is so big, it is formless almost and doesn't really have boundaries."

"I think it's interesting how much we know and don't know about the big bang theory because we are so young as a planet and we're learning new things every day!"

"I find the big bang particularly interesting because it is how everything started. It is so mind blowing to me that everything started from nothing."

"The cosmic microwave background proving the big bang theory by detecting photons is interesting to me due to my faith in creationism."

"I found it interesting that because of finite speed of light, looking at objects further away from us allows us to see those objects farther in the past."

"If a proton and its antiproton 'evil twin' meet up with each other, they will be destroyed and converted back into energy which is the process of annihilation."

"Everything. Especially learning about how some protons were able to survive. This interests me for two reasons. First because it is mysterious. Why did they survive? Second because those surviving particles were the seeds to everything we know."

"How the edge of the universe is time instead of space."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I don't understand how they find an edge in time/space, and how scientists know they have run out of galaxies to see."

"Probably a lot of it."

"Time zero confuses me because I don't understand what was there, or here, before that. Do we know what it could have been?"

"The statement that says the universe in not infinite, but finite (in time)confuses me because I don't understand what it means."

"Distant galaxies appear to be younger, since I thought they would appear to be older."

"Hubble's law! I feel like I almost get it but am having a hard time wrapping my mind around the raisin bread model. Is it just that two galaxies that are close together move away less from one another during expansion? I get it when I think about distance but when I can't understand how the distance increases the rate of motion of galaxies moving away from each other."

"I'm still trying to understand the big bang. I always it started from a certain point, but now I read it really started from a state of high density and high temperature with no space between galaxies. I'm having a hard time understanding that."

"How the edge of the universe is time instead of space."

"Nothing at all."

Briefly explain how it is possible for you to see a star in tonight's sky that may have already died a long time ago.

"It is possible because of the finite speed of light, it takes a very long time for stars' light to travel to us."

Describe what will happen when a matter particle and an antimatter particle meet each other.

"Both particle and antiparticle disappear, leaving behind the energy they were made of. This is called 'annihilation.'"

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"How certain are you that they are right about the big bang?" (I am very certain that the science of the big bang is correct...so far.)

"There's a song called 'The Big Bang' by Rock Mafia but I'm not sure if it's related to astronomy." (Whether it is about the big bang or not, the video does feature Miley Cyrus...)

It's my observation that many of the flashcard questions do not actually have the answer in the text, but allude to the answers." (Yes, since they require more sophisticated thinking than reading comprehension--which is what you get to practice in many of the in-class activities.)

"Why is the universe expanding and cooling? Don't things normally expand with heat? Does expansion just mean more matter being created?" (Yes, if you add heat to a gas to increase its temperature, the gas will expand. But if you allow a gas to expand (without adding heat to it), the gas will cool off and drop in temperature. The expansion of the universe doesn't mean more matter is being created, but more space is being created, so the distances between galaxies are getting bigger.)

Online reading assignment: cosmology (SLO campus)

Astronomy 210, fall semester 2012
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on evidence for the big bang, and models of the early big bang.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"Universe expansion. Interesting and mystifying to ponder how the universe can expand if it already is everything."

"Heinrich Olbers' question was truly interesting--if there is actually an end to the universe--because I wonder the same thing everyday."

"The farther we look out in space, the farther back in time we are looking. So we can see Deneb which is 1,400 light years away, but what we are looking at is not as it is now, but 1,400 years ago. It sounds dumb, but I had really never thought about it before."

"The story of the elephant's trunk getting stretched by the crocodile."

"The way most science teachers explain it, to me it seems as though the big bang is a topic that is elaborated yet skimmed over quickly so a teacher can say they discussed it. When in all actuality, it is pretty complex, that deserves enough time to learn about it."

"It seems impossible that a big bang created everything so perfectly."

"The big bang and what made it happen. What made it happen?"

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"At this point, just about everything in class confuses me."

"How you could look 'back in time.'"

"None of this is fulfilling."

"Universe expansion. How is this possible? If the universe is everything it is really creepy to me that it is expanding outside of itself. Are we just a science experiment in a petri dish for some gigantic creatures that created us, and then how were they created? I don't think I like this section."

"I can't wrap my head around the fact that the universe doesn't have an edge. If the universe is expanding, then where is it expanding to?"

"If everything we are seeing in space is seen as it was in the past however many light years away it is, then how will we ever know what is happening right now?"

"How light could not survive with the scattering of photons back before recombination."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Do you have a cat?" (Yes, and she has her own Facebook page.)

"What triggered the creation of the universe in the first place? How were the particles of matter brought into existence?" (To quote Rolf-Dieter Heuer, the Director-General of CERN: 'There's a need for us, as naïve scientists, to discuss with philosophers and theologians the time before or around big bang.')

"Can we postpone Quiz 6 until the week after Thanksgiving? I would be very thankful." (The second midterm, which covers Quiz 6, is already scheduled for the week after Thanksgiving, so no, Quiz 6 has to be just before Thanksgiving.)

"There's gotta be aliens. It just wouldn't make sense for there not to be."

"How can we get a hold of the answers for the study guides that are posted on the website, when we study? I can only find one set and it only contains three answers." (I would be more than willing to discuss your responses to the archived quizzes/exams and flashcard questions during posted office hours or an arranged appointment, just before/after lecture, or via e-mail.)

"When is this assignment due? Can you please explain how to read your calendar again?" (Online reading assignments are open Thursday-Tuesday, and are posted just after the previous Wednesday's lecture, and are posted again (for redundancy) just before the following Wednesday's lecture.)

Online reading assignment: cosmology (NC campus)

Astronomy 210, fall semester 2012
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on evidence for the big bang, and models of the early big bang.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"Contemplating an edge to space. The 'edge' of space is actually just how far back time goes. The universe has no boundaries (but the observable universe does)."

"That telescopes are like time machines. We see what a star looks like in the past. I think its interesting because people constantly wonder what things would be like if they could go into the past with a time machine."

"Astronomers can detect radiation from the CMB and be able to explain what it is."

"Olbers' question about darkness in the sky was very interesting, and it was cool to see a literary genius such as Edgar Allen Poe easily answer this question several hundred years later."

"Well, it is interesting how much I am confused."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I did not find anything particularly confusing in this chapter."

"That the night sky is dark because the universe had a beginning."

"That there is no center in the universe. It seems like there would have to be a place where the big bang happened."

"How we can see a star that looked the way it did thousands of years ago."

"I don't get why a big bang would occur? What would have caused the big bang in the first place?"

"Why lithium won't be created again after the nucleosynthesis era ended."

"I find the big bang hard to understand because I believe something else."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Do you believe in God? Do you believe the big bang theory? How important is it for you to know how the universe began?" (Yes, yes, and very.)

"What is something you don't get about the big bang?" (How and why it started. To quote Rolf-Dieter Heuer, the Director-General of CERN: 'There's a need for us, as naïve scientists, to discuss with philosophers and theologians the time before or around big bang.')

"How can I get extra credit?" (There will be more extra credit opportunities later this semester online, and during review sessions.)

"I love this class! :)" (Awesome sauce.)

Presentation: early big bang

From the previous presentation, we thought about going backwards in time to determine the approximate age of the universe, and found that the space between everything approaches zero around 14 billion years ago--the big bang. (Video link: "The Big Bang.")

As with Brad Pitt's character aging backwards in The Curious Case of Benjamin Button (Warner Bros., 2008), we will go through the early stages of the big bang in reverse chronological order, at each step moving to the next older, hotter, and denser phase. Our current understanding of physics does not extend all the way back to time zero, so we are only going to cover four key events in the early stages of the big bang. You are later welcome to run these events forwards in time, as in your textbook.

So let's go back to the beginning!

This is a busy graphic, which we'll show again at the end of this presentation, but from right-to-left it shows key events in reverse chronological order, from now to 14 billion years ago; and from left-to-right these events in proper chronological order from 14 billion years ago to today.

First, the first stars.

Running the clock backwards from the present day--that is, looking out further and further away--we can see galaxies with less and less metallicity, and eventually a time/place where there were no galaxies. This is a time when the first-generation stars were born out of primeval hydrogen. (Video link: "WMAP’s Portrait of the Early Universe.")

Observations of these hyper-massive stars forming from raw hydrogen show them exciting the hydrogen atoms around them (as discussed in a previous presentation), creating gigantic emission nebulae. The process of exciting hydrogen electrons causes the electrons to be stripped off, ionizing the hydrogen.

Second, the first photons.

Looking further out away from the first-generation stars means looking further back in time, to before the the first-generation stars were born, where there is only hydrogen, and no stars--this is the dark age of the universe. (Video link: "WMAP’s Portrait of the Early Universe.")

Looking even further away and further back in time, we run into a figurative wall of light in every direction: this is the cosmic microwave background, and while this radiation is not the first photons ever created, it is the first and oldest photons that we are allowed to see. (Video link: "WMAP’s Portrait of the Early Universe.")

These intense photons are detectable today as a faint cosmic microwave background, which can be detected with special radio telescopes, and also televisions with old standard-definition rabbit ears--on an unused channel, a portion of the static "snow" that you can see is produced by the CMB signal.

So what would suddenly release this wall of photons, while making older photons that existed before this time be unobservable to us today?

This is a much hotter and denser universe than the dark ages, so hot that positively charged protons and negatively electrons are separated from each other, and are too energetic to be allowed to join up to make neutral atoms. Think of a mosh pit of protons and electrons constantly bashing into each other. Any photons in this hot, dense universe would be continuously kicked around and scattered, so light from this time and earlier could not have survived intact be observable today. (Video link: "Journey to the Centre of the Sun.")

But as the universe gradually cools and expands, protons and electrons calm down such that they can join up with each other, and as soon as they are allowed to do so, they all do so. This event where all protons and electrons suddenly form neutral atoms is recombination. Back to our mosh pit analogy, when the protons and electrons calm down, pairing off to slow dance with each other, then space on the floor drastically opens up. Photons at this point are now free to travel without being kicked around and scattered, and the cosmic microwave background are the first, oldest photons that started out from recombination. (Video link: "Journey to the Centre of the Sun.")

Third, the first fusion...even before the first-generation stars.

Going back in time even before recombination to a even hotter and denser time, the entire universe resembles the core of a star, where temperatures and pressures are high enough for protons to collide with each other and fuse. This is the nucleosynthesis phase of the early big bang.

For a brief time in this early universe, hydrogen fused into helium as in the cores of main-sequence stars, but can also fuse into deuterium (an unstable form of hydrogen) as well as lithium. What makes this early fusion in the universe unique is that deuterium and lithium cannot survive the high temperatures in the core of main-sequence stars--only helium survives--but the expansion and cooling of the universe shut off fusion such that deuterium and lithium from nucleosynthesis did survive to the present day. All the deuterium (found as "heavy water" in certain springs on Earth) and all the lithium (used in batteries for hybrid cars, computers and smartphones) that is found today can only have come from this early universe fusion.

Fourth, the first matter...stuff that makes up you, me, and the rest of the universe.

This is the farthest back in time we will go in our presentation, where the universe is intensely hot and dense. These are conditions we can reproduce using particle colliders today, and to investigate earlier times in the big bang merely requires building higher energy particle colliders (and money). The universe at this stage is so energetic that as in modern-day particle colliders, mass and energy are readily interchangeable--given enough confined energy, you can produce matter...and antimatter.

For this process of pair production, if energy creates a proton, it must also create the proton's "evil twin," an antiproton as well. Annihilation is the process where if a proton and its antiproton meet up with each other, they will be destroyed and converted back into energy. Everything that makes up matter has an antimatter "evil twin," and the very early universe continuously converted energy into equal amounts of matter and antimatter, and vice versa.

This presents a puzzle, as everything that we observe in the universe today is made of matter, but from pair production matter must be created with an equal amount of antimatter--so perhaps, somewhere else in the universe there is an equal amount of antimatter waiting to partner up with and subsequently annihilate us. Have you ever seen Seven Brides for Seven Brothers (MGM, 1954)?

What would happen if there was a sequel to this move...titled Seven Brides for Eight Brothers?

This is the hypothesis for why the universe is only made of matter today. Somehow instead of being produced in equal amounts, if there was slightly more matter than antimatter, then there would be something left over after all the antimatter produced is annihilated with an equal amount of matter. We today would then be the eighth unmatched brother, which makes us either fortunate or forlorn, depending on your perspective. In particle colliders equal amounts of matter and antimatter always seem to generated from pair production, but experiments being carried out today are searching for indications that there are certain processes that produce just a smidgen more matter than antimatter.

We've run the clock backwards, watching the first stars, first photons, first fusion, and first matter stages of the early big bang occur in reverse chronological order. We haven't gone all the way back to time zero, and there are some interesting events observed and conjecture that occurred even before these four stages that we will not cover in this course.

So concentrate on being able to describe what happened in each of these four stages, and the evidence that is either observed or recreated for each of these four stages.