David Suzuki: A Force of Nature

Here's a film that I recommend: A documentary based on David Suzuki's 75th birthday lecture.
https://www.youtube.com/watch?v=5ji7-pbELoM

 

The RCA 1P21 and a Hubble image of Proxima Centauri

A couple of interesting images:

1. This first one is the RCA 1P21 Photomultiplier tube, the work horse of stellar photometry before photodiodes and CCDs.

2. An image of the star Proxima Centauri (Alpha Centauri C), the closest star to our own Sun at 4.243 LY (1.3009 pc) with a parallax of 768.7 mas. (Hubble Space Telescope image).

John Coltrane

Now for some music from John Coltrane.
1. A Love Surpreme (full album) 1964
This was in a very real sense Coltrane's spiritual/religious statement. (Released in 1965)

https://www.youtube.com/watch?v=p3L-gL4XmjM

2. "Stellar Regions" from the album Stellar Regions (1967)

https://www.youtube.com/watch?v=1QiVRmvkwYM

A bit of thoughtful theology and philosophy from John Shelby Spong and Thomas Merton

4. And now a couple of authors that may give you a bit wider view of Christianity and its possibilities:

John Shelby Spong

One of his books:

Thomas Merton (pictured here back in the 60s with the Dalai Lama)

And one of his very beautiful books:

Vatican Observatory

3. Here's the website for the Vatican Observatory and their research program (including stuff about Brother Guy who has become a bit of a celebrity).

 http://www.vaticanobservatory.org/

 

 

 

 

A short Bio of Georges Lemaitre

2. Here's a short little documentary from ESA, the European Space Agency, about physicist, cosmologist and ordained Catholic priest, Father Georges Lemaitre, the originator of what we now call Big Bang cosmology.

https://www.youtube.com/watch?v=RL6ndOAOEeE

 

 

 

 

What follows above: A prelude to some future statement(s) on the question of religion.

As a prelude to some statement of "my position" on the matter of world view, specifically on the matter of religion, let me list some links and books in a series posts. Here is the first.

1. Theologian and philosopher Thomas Berry: Trailer and teaser for the film "Thomas Berry: The Great Story" from Bullfrog Films.  

https://www.youtube.com/watch?v=-cCCKo5rxE0

OR

https://www.youtube.com/watch?v=wPpg_UkGDsU


Here's is link to the Thomas Berry Foundation:

http://www.thomasberry.org/

 

Four Poets That Matter: A January 6 Reading in Youngstown, Ohio

Four Poets That Matter

A Reading by:

Karen Schubert

Robert Miltner

Karen Kotrba

Molly Fuller

Sunday

January 6th, 2013.

7pm until late

Lemon Grove cafe

110 West Federal Plaza

Youngstown, Ohio 44503 

 Phone (330) 744-7683

 "It's time to matter"

       - Robert Hunter
EVENT ON facebook: https://www.facebook.com/events/185800641559269

DOWNLOAD fliers here: Download 8 x 10 printable flier here: http://docs.com/PUQV of the event.
2 per sheet version can be downloaded here as PDF file: http://docs.com/PUQW

Power Output of the Sun

CALCULATING THE POWER OUTPUT OF THE SUN

ÓDecember 2000, Douglas A. Fowler

INTRODUCTION

Work, energy, and power

     What follows is a very brief review of the most basic definitions of work and power.  This is not intended to be complete and you are encouraged to read up on this in a good introductory physics text, for example, Giancoli (1998).

     If you exert a constant force F over some distance d, the work that you do, w, is defined by the dot product of the force vector and the displacement vector:

                    w = F×d

It can be shown that this formula is equivalent to

                    w = Fdcosq

or simply

                    w = Fd

when the force vector and displacement are parallel and in the same direction, i.e., cosq = 1.  Hence, in the SI system, work is given in units of newton×meters, N×m; 1 N×m is called a joule, J, i.e., 1 N×m = 1 J.  Work on some object results in changes in the energy of that object:

                    w = DKE + DPE + Q

where DKE is the change in the object’s kinetic energy, DPE is the change in its potential energy, and Q is the energy lost to dissapative forces like friction.  This is a version of what is often called the work-energy theorem.  From it follows the simple definition of energy that one often hears: energy is the capacity to do work, and work results in changes in energy.  

     Power is defined as the time rate of change of energy production or consumption.  In the language of calculus this is written as

P = dE/dt

                

where P is power, E is energy, and t is time.  Algebraically, this is approximated as

P = (change in E)/(change in t)

                

The symbols DE stands for the ‘change in energy’, that is the amount of energy produced or consumed by some process; Dt stands for the time interval over which this occurs.  The units of power are watts, symbolized as W; 1 J/s = 1 W.  We must be careful with the terms ‘produced’ and ‘consumed’; we should really say transformed.   For example, a 100 W light bulb transforms the energy supplied to the filament by an electric current into radiant energy (with a spectrum corresponding to a blackbody at the same temperature as the bulb’s filament).  100 W means that this transformation happens at a rate of 100 J/s.

     Now, you could lift a 1 kg mass through a height of 1 m, and do this in one second.  1 kg weighs 9.8 N at the surface of the Earth. You then must lift with an upward force equal to 9.8 N.  (We, of course, are completely aware of lifting with just a little more than this 9.8 N to get the mass into motion, but this can be neglected when compared to the work done throughout the rest of the lift.)  As a lifting machine you would be operating with a power output of 9.8 N×m/s, that is 9.8 J/s or 9.8 W.  A kilogram weighs about 2.2 pounds in the English system.  So lifting this weight to a height of 1 m (a distance that is just under 1 yard plus 3 and 3/8 inches) once each second is equivalent to 9.8 W. If you wanted to lift weights to generate the electricity needed to light the 100-watt bulb, you would have to raise a weight of 22.4 pounds up 1 meter once each second for as many seconds as you wanted the light to stay on!

The Solar constant

     The amount of solar power intercepted by the Earth has been determined to be 1370 watts per square meter. (Fix, 2001).  Abell, Morrison, and Wolff (1991) briefly discuss how measurements can be made from which to determine this value, called the solar constant. Another way to describe the solar constant is as follows: an area of 1 square meter placed at the distance the Earth is from the Sun, 1 astronomical unit (1 AU), and facing normal to Sun’s rays, will intercept 1370 W.  Letting f stand for the solar constant, we can write

                    f = 1370 W/m²

Observing the Sun

     We will make observations of the Sun by direct viewing through a filter attached to a telescope.  As the saying goes, DO NOT TRY THIS AT HOME, without the proper equipment.  You are encouraged to read Jeff Medkeff’s article (1999) “A Beginner’s Guide to Solar Observing” in the June, 1999 issue of  Sky and Telescope.   We use a circular, full-apeture glass filter mounted over the front corrector plate of an 8-inch Celestron^â Schmidt-Cassegrain telescope.  The filter itself consist of a glass plate machined flat, with its front surface coated with evaporated metals.  This produces a highly reflective surface, allowing only 0.00001 of the incoming sunlight to pass through the filter and into the telescope.  The filter is placed over the front corrector plate so that no unfiltered sunlight enters the telescope and cooks any of its optics. For a description of this kind of filter, see Chou (1998) or MacRobert (1999). 

Sunspots

     The first thing you will notice are sunspots. This will not be our focus here, and the interested reader is encouraged to look up this topic in any of the astronomy texts listed in the references.  

Limb darkening

     The visible layer of the Sun, what we think of as its surface, is called the photosphere.  

The gaseous photosphere is less than 500 kilometers thick (Seeds, 2000) and may be as little as only 200 kilometers in thickness (Fix, 1999).  This is much less than 1/10 of 1 percent of the Sun’s radius.

     

     Photons are emitted by the atoms of the hot gasses in the photosphere.  A photon can travel only so far through these gasses before it is absorbed by another atom.  The average length of this distance is called the mean free path by physicists.  Let’s represent this mean free path as a distance d.  When we look at the center of the Sun’s image, we are seeing photons emitted from a depth d, that is, we can see to a depth d straight into the solar photosphere.  But when we look farther to the edge of the Sun (called the Sun’s limb), that same distance d, now at a shallow oblique angle, allows us to look only to a far lesser depth than when we looked toward the center of the Sun’s disk.  We see light from this shallower depth where the gasses are cooler.  The cooler gasses emit photons at a longer wavelength causing the limb of the Sun to look not nearly as bright as the central part of its image.  This is called limb darkening.  Abell, Morrison, and Wolff (1991) give a good description, with diagrams, of limb darkening.

     For our purposes, we want to see whether the limb darkening is uniform in all directions outward and across the Sun’s image when viewed through a telescope. This will give us some clue as to whether we can assume that the Sun radiates its energy evenly in all directions out into space. Make these observations and see what you think.             

THE PROBLEM

     Using the solar constant, along with your assumption about whether the Sun radiates uniformly in all directions, calculate the total power output of the Sun. To set up this calculation, ask yourself how much solar power passes through 1 square meter at the Earth’s distance from the Sun. Then ask how much power would be intercepted by 1 square meter placed at this same distance but in a direction directly outward from the Sun’s north pole. Another clue will come from the idea of the Dyson sphere.

    

The Dyson Sphere

     A clue as to how to approach this problem can be found in the speculative concept

of a Dyson sphere. In the late 1950’s and throughout the 1960’s, physicist Freeman Dyson took an active part in discussions concerning the possibility of detecting extraterrestrial intelligence. Dyson (1959, 1966) argued that members of a technically advanced civilization, faced with the Malthusian social and economic pressures resulting from the overpopulation of their homeworld, might literally take apart the other planets of their solar system and use these materials to construct a sphere that would completely enclose their sun. Such a sphere, constructed with a radius equal to the semi-major axis of the orbit of this civilization’s home planet, would then be able to collect the entire energy output of the central sun. Further discussion of this idea can be found in Dyson (1979), Niven (1974), Sagan (1973), and Sullivan (1966). Lemarchand (1992) provides a good more recent overview of the problems of detecting extraterrestrial civilizations (if they even exist!).

     Science fiction writer Larry Niven (1970, 1974) based his novel Ringworld in part on Dyson’s ideas. Niven envisioned a somewhat less ambitious civilization building a wide circular band centered on the sun, rather than a full sphere. This band would again be constructed with a radius equal to the semi-major axis of the orbit of the civilization’s home planet. This ‘ringworld’ would be essentially a wide equatorial slice of a Dyson sphere.      

Mass equivalence

     Once we know the total power output of the Sun, we can calculate the rate at which mass is converted to energy by the nuclear reactions at Sun’s core. For this we use Einstein’s famous equation, perhaps the only equation that most lay readers know from its status as a cultural icon:

                    E = mc²

Here we let E stand for the energy produced by the Sun in 1 second. The amount of mass converted to this energy is given by m. The speed of light in a vacuum is represented by c. Einstein showed in 1905 that lightspeed squared is essentially a conversion factor between units of mass and equivalent units of energy: mass and energy can be converted back and forth between one another with the restriction that the total mass/energy in any physical process remains the same. Interested readers are encouraged to consult Einstein (1961) or any good physics text covering modern physics such as those listed in the references: Beiser (1987), Bernstein, Fishbane, and Gasiorowicz (2000), Giancoli (1998), Tipler and Llewellyn (1999), and Weidner and Sells (1980).     

DISCUSSION and FURTHER CALCULATIONS

The proton-proton chain

     The Sun’s energy is produced deep in the solar core where temperatures reach 15 million Kelvins (K) and the pressure is great enough to compress hot ionized gas to a density of nearly 150 g/cm³ (Fraknoi, Morrison, and Wolff, 1997) - about 150 times that of water or 13 times the density of lead. The ionized gas itself is essentially a gas of free protons, electrons, and helium nuclei. The high density greatly increases the odds that two protons collide; the high temperature means that these particles are moving fast enough so that when they do collide, they can get close enough for the short-range, attractive  strong-nuclear force to overcome the electrostatic repulsion between the two positively-charged protons. We can represent the resulting process, called the proton-proton chain, in three steps, described below.    

     In the first step, two protons (¹H) collide and interact to form a nucleus of deuterium or heavy hydrogen (²H), a positron (e⁺), and a neutrino (n). In the second step, a deuterium nucleus collides and interacts with another proton to produce a helium-3 nucleus (³He). In the process, one or more gamma-ray photons (g) are released.

Lastly, two helium-3 nuclei collide and interact to produce a single stable helium-4 nucleus (⁴He) along with a couple of leftover protons. Since the last step requires the input of two helium-3 nuclei, we must run the second step twice. But to run this second step twice, we need two deuteriums which requires that we also run the first step twice. This is symbolized below by writing both the first and second steps in parentheses with the notation 2 ´ in front.   

                    2 ´ ( ¹H + ¹H ® ²H + e⁺ + n)

                    2 ´ ( ¹H + ²H ® ³He + g)

                              ³He + ³He ® ⁴He + ¹H + ¹H

Running the first and second steps twice requires the net input of six protons. But two protons are returned with the completion of the third step. The net result of this process can then be written as:

                    4¹H ® ⁴He

which tells us that four hydrogen nuclei are fused to make one stable helium nucleus. 

In stars with masses like that of the Sun or smaller, essentially all of their energy is produced by this nuclear reaction, the proton-proton chain.   

    

Mass defect

     The conversion of mass into energy becomes evident through what is called the mass defect. If we take the at-rest mass of four neutral hydrogen-1 atoms (Weidner and Sells, 1980), we have a total, in atomic mass units (u), given by:

                    4(1.007825u) = 4.031300u

A single neutral helium-4 atom has a rest mass of 4.002603u (Weidner and Sells, 1980).

The difference between the two is called the mass defect:

                    4.031300u - 4.002603u = 0.028697u

This 0.028697 atomic mass units represents the mass converted to energy each time the proton-proton chain runs its course. We could use this fact to find the number of helium-4 atoms produced each second by the nuclear reactions in the core of the Sun.

                   

The lifetime of the Sun

When we have a reasonable estimate of the amount of mass converted by the Sun into energy each second, it seems reasonable to ask how long the sun can last. Not all of the Sun’s mass is available for nuclear fusion; only the portion of the Sun’s material that is under enough pressure and at a high enough temperature is subject to fusion. Seeds (2000) gives the minimum temperature for hydrogen fusion at about 10 million K. Only about 34 % of the Sun’s mass, contained within 20 % of its radius, is at a temperature of 10 million K or higher (Seeds, 2000). We also know that the composition of the solar gasses is 71 % hydrogen (Fix, 2001), but it has been estimated that at the core, only 34 % of the core mass is hydrogen (Fix, 2001).  If we assume the Sun fuses hydrogen into helium at a constant rate over the rest of its lifetime, how much longer will the sun last? Note that this assumption is probably far too simple: about 5 billion years ago, when the Sun began its main sequence life, the Sun’s power output was only about 70 % of what it is now, so we know that the Sun’s power output is steadily increasing.        

REFERENCES

Abell, G. O., Morrison, D., & Wolff, S. C. (1991). Exploration of the universe (6th ed.).

     Philadelphia: Saunders College Publishing.

Beiser, A. (1987). Concepts of modern physics (4th ed.). New York: McGraw-Hill.

Bernstein, J, Fishbane, P. M., & Gasiorowicz, S. (2000). Modern physics, Upper Saddle

     River, NJ: Prentice Hall.

Chou, B. W. (1998). Solar filter safety, Sky and telescope, vol. 95, no. 2, p. 36-40,

     June, 1998. Also On-Line at http://www.skypub.com/sights/eclipses/solar/safety.html,

     Contacted 12/20/00.

Dyson, F. J. (1959). Search for artificial stellar sources of infrared radiation, Science,

     vol. 131, p. 1667-1668.

Dyson, F. J. (1966). The search for extraterrestrial technology, in Perspectives in modern

     physics (essays in honor of Hans Bethe), R. E. Marshack (Ed.), New York: John

     Wiley and Sons.

Dyson, F. J. Disturbing the universe, New York: Harper & Row. 

Einstein, A. (1961). Relativity: the special and general theories, New York: Crow     

     Publishers.

Fix, J. D. (2001). Astronomy: journey to the cosmic frontier (2nd ed., updated). Boston:

     McGraw Hill.

Fraknoi, A., Morrison, D., & Wolff, S. (1997). Voyages through the universe. Fort

     Worth, TX: Saunders College Publishing.

Giancoli, D. C. (1998). Physics: principles with applications (5th ed.). Upper Saddle

     River, NJ: Prentice Hall.  

Lemarchand, G. A. (1992). “Detectability of extraterrestrial technological activities,” On-

     Line at http://www.coseti.org/lemarch1.htm, Contacted 12/21/00.  

MacRobert, A. M. (1999). “Solar filters: which is best?,” Sky and telescope, vol. 98, no.

     1, p. 63-67, July, 1999. Also On-Line at http://www.skypub.com/resources/

     testreports/accessories/9907tp_filters.html, Contacted 12/20/00.

Medkeff, J. (1999). “A beginner’s guide to solar observing,” Sky and telescope, vol. 97,

     no. 6, June 1999. 

Niven, L. (1970). Ringworld. New York: Ballantine Books.

Niven, L. (1974). “Bigger than worlds” in A hole in space. London: Futura Publications.

Niven, L. (1990). Author’s introduction to “From Ringworld” in N-space, New York:

     Tom Doherty Associates. 

Sagan, C. (1973). The cosmic connection. New York: Dell Publishing.

Seeds, M. A. (2000). Horizons: exploring the universe (6th ed.). Pacific Grove, CA:

     Brooks/Cole.

Sullivan, W. (1966). We are not alone, New York: McGraw-Hill.

Tipler, P. A. & Llewellyn, R. A. (1999). Modern physics (3rd ed.). New York: W. H.

     Freeman.

Weidner, R. T. & Sells, R. L. (1980). Elementary modern physics (3rd ed.). Boston: Allyn

     and Bacon.

Syllabus for AST 101, Astronomy Lab, Fall 2011

ASTRONOMY 101 Observational Astronomy E041                                                  Fall  2011

Instructor: Douglas Fowler                                                                               Office: Room 1075

Class meets Mondays, 7:00pm – 9:30pm, Rm. 1069                                Office Phone: 832-2851

Course Number 1862                         Office Hours: M,W, F 11:00am-11:50am, Th 11-11:50am

The class runs from September 12^th through December 12^th.  There is no final.

Text: Pasachoff, Jay M., A Field Guide to Stars and Planets (4^th ed.) (in the Peterson Field Guides series), Boston: Houghton Mifflin, 2006. 

Other requirements:

A Notebook dedicated to Astronomy Lab – The notebook will be the major part of your grade!

A Calculator (one that you know how to use) 

           

Lab Groups: Students will work in groups of three or four. Each student will present written laboratory notes at the conclusion of each class.  For some (not many) of the experiments (to be announced by the instructor), the group will submit a lab report. Each member of the group will participate in collecting and analyzing the experimental data. Each member of the group is expected to participate in writing the group reports! These must be done on a word processor and adhere to a uniform format.  

Note: In reality, we will do very few of these, but I put this here for the purpose of showing you what should be kept in mind when doing anything scientific.

Lab reports:  

When required, these should follow the following outline:          

   1.      The title of the experiment, the date it was performed, and the names of the captain and other members of the lab group. This can be on a separate title page or on the top of the first page of the report.

   2.      A brief introduction that addresses the following: WHAT is to be measured, HOW it is to be measured, and for what PURPOSE it is being measured (i.e. what is to be accomplished/learned from this experiment).

   3.      Data. This should include an organized presentation (usually tables) of all appropriate data (including units!) and an indication of the precision of each measurement.

   4.      Data analysis.  This should include graphs, sample calculations, and responses to any questions posed in the lab manual.  Pay attention to significant figures!

   5.      Error analysis.  List and discuss, quantitatively whenever possible, sources of error.

   6.      Conclusions.  A brief summary of what you did, what you found and what you learned.

   7.            A list of citations in the form of a bibliography.

   8.            The “original” or “raw” data sheet must be appended as the last page of the report.

 

Note: This next item is really, really important for any of our work.  Always cite your sources! The core of the in-lab work material for this course will be looking up and using a wide variety of maps, charts, books, websites and so on.  Reference everything! 

Citations: Any reference to the lab manual or other books should be cited properly in the text and included in the bibliography. For example, you might write something like: “Cochran (2005) describes an apparatus for determining the moment of inertia for a rotating system.” Or, “The moment of inertia of the rotating system can be determined from the following equation (Cochran, 2005):” In the bibliography you would then list something like this (depending on what style guide you use):

          Cochran, W. The physics lab manual II (3^rd revised edition), Youngstown, OH:        

                    Youngstown State University, 1995, 2005.

Note: ANYTHING that you look up for this class must be cited with complete bibliographic data.

Grading:

You grade will be based on:

(1) laboratory notes and participation Note: Attendance will count and be checked each lab. 

(2) any handed-in lab reports and/or assignments

(3) your notebook/journal near the end of the course. Notes will be checked at the conclusion of each lab.

(4) rare, but possible quizzes or exams.

We will simply accumulate points based on the various assignments to given in class. This also means that must show up to class. I will not take attendance, but if you routinely skip class I cannot be the one responsible for your work or grade. Grades will be assigned on the following percentage scale:

A	90-100 %
B+	86-89 %
B	80-85 %
C+	76-79 %
C	70-75 %
D+	66-69 %
D	60-65 %
F	0-59 %

NOTE: I do not do email everyday, but you can feel free to email me at:

douglas.fowler@uwc.edu

but do not expect me to write back to you with complete details of what we covered in a given

class. Laboratory work requires that you be there in person.

Last thoughts: 

“Well,” said Stuart, “a misspelled word is an abomination in the sight of everyone. I consider it a very fine thing to spell words correctly and I strongly urge everyone of you to buy a Webster’s Collegiate Dictionary and consult it whenever you are in the slightest doubt.”

                                                                                                         From Stuart Little, by E, B, White

Recommended: The Elements of Style, William Strunk, Jr. and E. B. White

And what is good, Phaedrus, and what is not good –need we ask anyone to tell us these things?”

                            

                                     Socrates talking with Phaedrus in Plato’s Symposium,

                                     as quoted by Robert  M. Pirsig in Zen and the Art of Motorcycle Maintenance,

                                     an excellent discussion of what might be meant by quality in, among other

                                     things, good technical work.

Notebook/Journal/Observing Log

A major part of your grade will be based on the notebook that you keep for this class.  It will be well-organized, neat, dated, etc.  Entries will be built around:

1. Real-sky observations we make in the lab on clear nights.

2. Real-sky observations that you will make outside of class on your own.

3. Indoor work that we do in the lab.

4. Any additional thoughts or writing that you wish to do that is built around astronomy or anything related to astronomy. Creative writing is acceptable here. 

From time to time I will post things related to this class on my blog:

www.thepurpletwilight.blogspot.com