Observing with Street Lights

Observing with Street Lights
Dark sky sites not always necessary to see the Milky Way (This image was taken ouside of a B&B in Julian, CA)

Wednesday, April 5, 2017

Climate change and ecosystems with Dr Nyssa Silbiger at Our Cosmos Meetup; Supernova light curves, time dilation and expanding or static universes? Dava Sobel talks about "The Glass Universe" at Chapman University; Resident Astronomer wins blue rhino

Greetings from Palmia Observatory

This week I attended a couple of meetings brought to my attention by Our Cosmos Meetup group and if you are interested in exploring scientific fields with public events you should consider joining up and getting announcements for many upcoming, usually free, events. The first event this week for me was a lecture by Dr. Nyssa Silbiger, UCI postdoc, on "Climate change effects on ecosystems.  The lecture was held at the Peter and Mary Muth Interpretive Center located on the back bay in Newport Beach.

It's a beautiful location with walking paths across the mud flats and water with lots of flowers and interpretive displays.  I had sailed several times in Newport harbor and dined at the restaurants there but had never been to the back bay before.  Check out the scenic photo below (courtesy of Our Cosmos leader, Patricia.)

View from Peter and Mary Muth Interpretive Center at Newport Back Bay (Source: Patricia at Our-Cosmos Meetup.com)

Now, I first got interested in climate science while trying to understand how astronomers can measure and predict the temperature of planets and exoplanets.  This exercise of course is just physics applied to the heat balance between radiation received by the planet from its star and the radiation reflected and absorbed by the planet.  If the incoming radiation doesn't match the outgoing radiation then the planet's temperature will change.  To figure out by how much the change will be is quite complicated and a major effect on outgoing radiation is caused by greenhouse gases which cause the outgoing radiation to match the incoming radiation by raising the surface and atmosphere temperature so that the higher infrared radiation is just the right balancing amount.

Now, Dr. Silbiger made a summary of her current research project which has been to examine and monitor the water pH in various seashore type locations such as in tide pools and near coral deposits and determine the effects on the organisms living there. She did a great job of explaining the complexity of the ocean system and the various disciplines necessary to understand what is really going on.  Her research is to better understand how sensitive the biology of the ocean is to changes in ocean pH, which is mostly determined by the amount of absorbed CO2.  Likewise the amount of CO2 in the oceans is a function of the amount of CO2 in the atmosphere and how much carbon enters the oceans through rivers and weathering and how much is removed and added by biological activity The water pH becomes lower (more acidic) with the more dissolved CO2.  Biological organisms living in the sea are quite sensitive to ocean pH.  Since organisms both produce and consume CO2, both biology and physics considerations are necessary to understand how pH changes.  Respiration decreases pH and photosynthesis increases pH.  She found that tide pools have variations of pH of up to 2 units and this is mostly determined by the organisms and their biological demand on CO2.  Near coral reefs the variation is much less and determined more by the physics. Part of her discussion was to consider ways in which we might harness the natural variability in pH production by types of organisms to mitigate the effects of the oceans becoming more acidic.  The research goes on.

Dr Nyssa Silbiger, UCI postdoc, leads presentation and discussion of Climate Change Effects on Ecosystems
 (Photo Source: Courtesy Patricia at Our Cosmos group on Meetup.com)

If you are interested in following up more on the science of climate change you might want to look at some of the myths associated with climate change and what the science really is, I can recommend a website that I have watched for a while now at:

www.skepticalscience.com/

Anyway, it was a fun and informative time.  Thanks and good to see everyone there especially, Patricia, Sandy, Gabriele, Scott, Yasmin, Wendell and lastly, Trying to Write a Physics Book, Cris, as I had an extended first conversation with him.  He mentioned he was studying the time dilation of supernova light curves and possible implications for a static universe, as opposed to the accepted expanding universe.

Whoa, now this is pretty neat stuff!  The expanding universe is the widely accepted view by most astrophysicist, so I was interested right away, but first of all I had to get some understanding of how supernova light curves are tied up with time dilation.  I had not ever heard about this before.

Ok, ok, now I see what time dilation and supernova light curves are all about.  Let me see if I can give my interpretation if you are not familiar with the concept.  First recall that supernovas occur, fortunately for us, at very far distances from us and at distances where appreciable red shifts are observed.  The red shifts are due to the expansion of the universe and are calculated by comparing the wavelength of light emitted by the supernova to the wavelength of light received here on Earth.  The relationship between red shift and these wavelengths is represented by the formula z + 1 = observed wavelength here on Earth divided by wavelength of light emitted at the supernova. So if the measured red shift is, say,  z = 1, then the received wavelength is just 2 times the emitted wavelength, which since the wavelength is longer we say the radiation is red shifted.

Now, just as wavelengths are affected by the universe expansion, the timing and frequency of signals received is also affected in the same fashion.  For the same z = 1, the timing of events on that distant object will also be stretched by a factor of 2.  This is where the comparison of light curve duration for supernovas comes into the picture.  Suppose that supernovas of the same class and type that are observed to be nearby take about, say, 20 seconds for the light intensity to increase to maximum and then fall back to a more normal intensity.  That same type of supernova located at z = 1 would have a measured light curve time of 40 seconds for the same type of rising and falling back to normal light intensity.  This effect is called time dilation and has actually been observed.  Check out the plot below which shows the width factor, that is how much longer the light curve gets stretched or dilated,  as a function of the red shift.


Time Dilation and Light Curves (Source: Goldhaber and Supernova Cosmology Project)
Time Dilation and Supernova Light curves (Source: Goldhaber and the Supernova Cosmology Project)

So, we see that supernova light curve time dilation effects are offered as one of many types of evidence demonstrating the expansion of the universe and arguing against the "tired light" hypothesis and even the "static universe" hypothesis.  Now, this is just where Cris' story comes back into the picture because he is studying some other authors who say that the data used in these types of analysis have not used the correct filters and compensations for some of the known noise sources that can contaminate the data and give wrong results.  Ok, this is where it gets more difficult to understand and it is going to take much more study to  get into all of those details.  A major part of the paper referenced above is spent on describing all of the tests and compensations applied to get a good statistical sample of data for this analysis.  I am not swayed by one of the papers that Cris provided, by an author in Australia, that claims the analysis was not done correctly.  When I compare the depth of analysis used in just these two papers, the original paper by Goldhaber and team, for example, spends a lot of pages going over all of the analysis and data correction applied to get the results shown.  The skeptic, Crawford, who presents no new observational data, in his paper, which is not as detailed and it is hard to imagine that the team made up of Nobel prize winners, has made the mistake outlined in his paper.  Crawford argues that if the right corrections are made the data then the data will show the universe to be static, not expanding as currently accepted. Anyway, this presentation and criticism of papers is how science works and the more correct interpretation comes forward.  For me, it is going to take a lot more work to understand all of the corrections that the experts say must be applied to the light curves.  I have a hard enough time just to measure the light curve of a variable or eclipsing binary as readers of this blog will already know.  Anyway, thank you Cris for alerting me to this topic and I look forward to seeing your book!

Now the other event, brought to my attention by Our Cosmos, was the lecture by Dava Sobel, author of many books including "Longitude", Galileo's Daughter" and the recently released "The Glass Universe", which details the women "computers" at Harvard Observatory, who, over a century ago, determined the period luminosity relation for variable stars, now often called Leavitt's Law, after Henrietta Leavitt.

She began her lecture with a discussion of old and ancient maps that showed the various stages of understanding the heavens and how there were many gaps in maps of the sky from the southern hemisphere.  Magellan in his travels in the southern hemisphere noticed two large "clouds" in the night sky, which are now named the Large and Small Magellanic Clouds, which are now recognized as satellite galaxies of the Milky Way and are really large collections of gas, dust, stars and globular clusters.  With a declination around -69 degrees, they are not visible in the northern hemisphere.  (Make a note to myself and observatory staff and put seeing these objects, quite bright at magnitude 0.9, on our bucket list!)

She told the story of Henry Draper, a doctor, who became so enamored of the night sky and became an amateur astronomer and had big dreams of using the just discovered spectroscopic examination of stars and recognized that this new technique was going to change everything.  So, he and his wife, dropped everything and began this great adventure of measuring and cataloging the spectra of stars.  But just as he was getting started, he died, and his wife used the inheritance to continue on by funding the Harvard Observatory.  By 1890 they had collected over 10,000 spectra and expanded their survey to include the southern hemisphere by building an observatory in Arequipa, Peru.  Using this large catalog, Edward Pickering and the women "computers" developed the period luminosity relation as described earlier.

It was an enjoyable lecture and well appreciated. I asked Dava if Henrietta Levitt, who at time when women were not allowed on the observatory observing floor, had ever been able to see through the telescope, especially given how significant here discovery was.  She said that one of the other "computers", Annie Jump Canon, for sure did, because she was on the observing team that went to Peru and she observed at night and rode horse during the daytime.  Good job! I've noticed by the attendance at professional meetings for engineering, physics and astronomy, that the astronomy groups today have the highest percentage of women compared to the other groups.  That is progress! Finally, it was good to see some of our regular science squad, Patricia, Scott, Sandy, Dr. Arnold.   Most of the audience were Chapman students who were art or film majors who were there as a class assignment.  Their instructor handed out survey forms and skipped right by me.  Hey, I'm a student too!  Ok, ok, maybe a senior student and physicist wannabe and I don't need to fill out the survey or take the quiz!

Conference room filling up to hear author Dava Sobel at Chapman University "Visual Thinker" lecture series


Finally, after this long week of observational mishaps and meetings, Resident Astronomer Peggy and I escaped to our old favorite Keno's Restaurant for brunch and Bloody Marys.  Um, Um Good!  Anyway, I wanted to see if my "skill" with the giant claw amusement toy, so popular with really young kids and a few old folks too, was still there or not.  Yes, I managed to scoop out this blue rhino, which I gave to Resident Astronomer Peggy.  Nice; it's just one of the little things I can do to be appreciative!  She seemed to like the gift!


Retired Resident Astronomer retains "Giant Claw" skills and gives blue rhino win  to Resident Astronomer Peggy


I still plan to go after comet 41P sometime, but, Until next time,
Resident Astronomer George



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