Thursday, January 9, 2020


Before we look at what's up there, we need to understand how what's up there works. The same forces that operate down here drive what's up there. There's a problem though. An orbiting planet isn't the same thing as a mass whirling around on a string. For one thing, the string constrains the motion of a whirling object to a strict circle while gravity does not.

Frankly, it's hard to study orbital mechanics on Earth. Henry Cavendish finally nailed down the force of gravity, Newton's universal gravity constant, 71 years after Newton's death. He did it by suspending two very heavy objects at the opposite ends of a rod by a hanging, thin rod, and setting it oscillating. Then he did it again, setting a massive object near one of the hanging weights (the setup is called a torsion pendulum and its exquisitely sensitive.) The difference in the periods of oscillation gave him the information he needed to calculate the gravitation constant.

Other than that, have you ever tried to bring a planet into your bedroom?

Barring that, I have my gravity simulator (you saw it in the blog "Something about mass") and, although it isn't a perfect model of planetary orbits, it's surprisingly good.

First, let me point out that Newton learned more about mechanics by looking at the planets than by watching apples drop off a tree. As for the value of the acceleration of an object under the influence of gravity, Galileo had already done that work. Newton's first law of mechanics is actually Galileo's law of uniform motion. When Newton said, "If I have seen further, it is by standing on the shoulders of giants," he meant it quite literally. Newton was not a man given to bouts of humility.

Kepler's laws of orbital mechanics came before Newton. Newton's job was to tie it all together and figure out how the mechanics of planets was the same as the mechanics of an ox cart or that of a falling apple. So let's play with planets.

[Small ball around large ball]

The two balls are steel, so they're the same density. They don't orbit for long because they're close and exert more "gravity" and, more, because the model creates a lot more friction than the vacuum of space.

Newton deduced that the force of gravity between two masses increased with the product of the two masses and decreased with the square of the distances between them. He threw in a "universal gravitational constant" that makes the units and scaling work out. That's what Cavendish figured out years later.

The shape of the orbit is clearer when a smaller ball (BB) is used.

[Tiny ball orbiting around large ball]

Kepler worked out the shape of planetary orbits from the massive number of precise observations made by his mentor, Tycho Brahe. His first of three laws stated that planets move in elliptical orbits. Notice that, regardless how I start these balls rolling, they end up in elliptical orbits. That's not a result of the way the fabric is stretched. I tried to make sure that it was stretched evenly in the embroidery hoop.

For planets, as well as balls in the gravity simulator, the large ball is at one of the focuses of the small Ball's elliptical orbit.

Also, watch the way the ball speeds up in those tight turns. Kepler's second law states that the planets sweep out equal areas in equal times. That means that, when the planet is farther from the sun, it moves slower. 

His third law is harder to see on the simulator, but it says that, of two planets, the one orbiting further from the sun will have been a longer period (year) than the other.

[Balls of equal size]

When two balls of equal size are on the simulator, they orbit each other. Actually, that's true of all the orbits. It's just that, when the difference is large, it's hard to see the larger ball move. Even in space, planets and stars orbit around common centers. For instance, binary stars sling each other around a common center.

[Three balls of different density]

Here, I roll a small steel ball, an aluminum ball, and a wooden ball around the large steel ball. You probably could have guessed that the less dense wooden ball would orbit the longest. Also, notice that it's orbit is less elliptical.

[Tiny ball with different forces]

Here, I tried to roll the ball at different speeds (including, off the simulator). Notice the shapes of the paths. Even the ball's path at "escape velocity" is curved.

In fact, not all orbiting bodies take an elliptical orbit, but they do all follow conic curves. The Earth's orbit is almost, but not quite, circular. On the other hand, comets and other "space junk" may just graze the gravitational field of the sun on a hyperbolic curve, or loop around once on a parabolic path, and never return.


A collection of BBs make a nice little solar system. The really fascinating thing is when they are going in opposite directions.

[Two swarms]

Notice how they end up all going in the same direction! Ever wonder why all the planets orbit the sun in the same direction? Remember that, not only the sun is pulling them, but they are also pulling each other. It turns out that star systems are self-organizing.

The early history of Earth was violent. Collisions were common in the early solar system. In fact, our moon was probably the result of such a collision, a chunk knocked out of our planet by a traveling piece of space debris. Over time, such collisions became rarer. You've just seen one of the reasons why.

The gravity simulator is fun and offers a lot of possibilities for studying gravity and orbital mechanics. For instance, you could easily build a large version using a hula-hoop...or a trampoline! You might also check out different materials for the membrane. Plastic food wrap causes less friction.

Monday, January 6, 2020

Something about mass

I've had the delight of playing with a variety of balances from analytical balances that have to be protected from drafts and are precise to fractions of a milligram (that's a thousandth of a gram), to standard laboratory balances that will give you, oh, a few hundredths of a gram. And I've had several balances that came with various science kits. You won't find a statement if precision for those.

In one of my pharmacy labs, we had to synthesize aspirin and then purify it...because then we had to take it and, although the byproducts of aspirin are not horribly toxic (they didn't tell us that beforehand), they're not ideal snacks for happy-happy time. After taking our own aspirin, we measured the rate that it went through us. We were the people walking around campus with brown paper bags full of amber medicine bottles full of urine. Precision was important, but the laboratory scales gave us plenty for what we needed.

One of the most precise scales I've seen from a kit is the one from Penny Norman's Science Wiz Physics kit. Here, I use it to measure a gram of table salt.

[A gram of salt]

All this begs the question, "What is mass?"

I remember the stock answer from school, "mass is the amount of matter in a body," but I also remember the definition of matter, "Matter is that which has mass." That sounds a little too convenient...too circular. And what did they mean by "amount"?. Look at the picture at the top of this article. There's a gram of brass in the reference mass and a gram of table salt. It sure looks like there's more table salt (by volume) than there is brass.

I'm going to claim that the gram of table salt contains about 1x 10^22 molecules of sodium chloride and, to explain that, let me start close to the bottom.

Atoms are made of electrons, protons, and neutrons. Protons and neutrons are made of various other debris, notably quarks, but we don't need to go that far. A proton has a mass of 1.6726219 x 10^-24 grams. A neutron has a mass of 1.674927471 x 10^-24 grams. An electron has a mass of 9.10938 x 10^-28 grams. Electrons don't have enough mass to even consider, so let's forget them for the time being. The mass of the other two particles are so similar that we can just define an atomic mass unit as the mass of one proton or neutron. 

Table salt is impure sodium chloride and, to simplify things, let's ignore the impurities. What's the mass of a sodium atom? It has 11 protons and 12 neutrons so the mass of a sodium atom is 22.98976928 atomic mass units. Wait a second….but that's what my periodic table says. The fact is, the most common sodium atom has 11 protons and 12 neutrons, but there are other kinds of sodium atoms in nature that have more or less than 12 neutrons. It's the number of protons in an atom that makes it the element that it is. The number of neutrons can vary and you call the different kinds of sodium "isotopes" of sodium. If you take an average of the atomic masses of all the different isotopes of sodium according to their relative prominence in nature, you come up with 23.98976928 atomic mass units.

Avogadro's number is 6.0221409 x 10^23. That's the number of particles (atoms, molecules, etc.) in a mole of a substance and a mole is the number of grams that is the same as the number of atomic mass units of one particle. Since the atomic mass unit of sodium is about 24 and the atomic mass unit of chlorine is about 35.5, the atomic mass of sodium chloride (one sodium atom and one chlorine atom) is about 59.5. A mole of sodium chloride is 59.5 grams and a gram of sodium chloride is 1/59.5 mole. That means that you can divide Avogadro's number by 59.5 to find the (approximate) number of molecules of sodium chloride in a gram - 1x 10^22 molecules.

All of which gets us no closer to understanding what mass is. It has something to do with gravity. You find the mass of an object by comparing how hard gravity pulls on it to how hard gravity pulls on something else.

That "pull" is a problem, too. How does anything pull on anything? You might think you pull a wagon, but think again. Where do you apply pressure to the wagon...on the inside of the handle. You push against the inside of the wagon's handle. Can you really pull anything?

This bothered Isaac Newton all his life. He worked out all of how gravity works. He knew that mass is connected with gravity...somehow. By figuring out how planets have to interact to stay in their observable orbits, he knew that the force of attraction between bodies had to be the product of their masses divided by the square of the distance between them. A constant had to be thrown in to make the numbers work out but Newton never knew the value. Henry Cavendish came up with the value in 1798, 71 years after Newton's death.

What is gravity? The best Newton could do was "action at a distance". He was not amused.

Over the following years, there were all kinds of weird theories. One was that, as an object moved through some strange "ether" that filled the universe, it flowed around and would catch other objects up like things are pulled along in the wake of a fast moving boat. Imagine the dismay at the end of the 19th century and the beginning of the 20th when scientists had to accept that the universal ether does not exist.

At about the same time, Albert Einstein came along and figured out (part of) how it works. Here is mass and gravity according to Einstein.

[Gravity according to Einstein]

General and special relativity are weird...granted, but they are the most experimentally verified parts of physics, so there's little chance that that weirdness isn't a real part of our universe.

The gravity simulator above is a collection of Legos constructed to support an 11 inch embroidery hoop with a square of Lycra stretchy fabric clamped securely in it. The gooseneck assembly hanging over it holds my cell phone video camera.

Einstein's idea was that, instead of gravity being an attractive force between massive objects, any object with any mass distorts space around it and, then, other objects fall into the distortion just like the small ball bearing fell toward the large ball bearing.

The simulation isn't perfect. It suggests that mass distorts space into another spatial dimension. That isn't necessarily so.  It may just distort space into itself. The distortion is called a field, and there are other kinds of fields. If you set a magnet near one of these steel ball bearings, the magnet and the ball bearing will come together. 

This "action at a distance" of Newton can now be explained as a "falling together".

We're certainly going to be looking a lot in the future at these "falling togethers" and you'll see more of my gravity simulator very soon.

But the weirdness deepens. I've heard physicists express the conviction that, matter and energy are not the realities of our universe - the only things that are real are fields  So why do matter and energy seem so real to us and fields are so hard to wrap our brains around 

That has a lot to do with how our brains code the world around us. Brains are primarily interested in survival and the important things in our world related to survival are things like not being crushed in rock slides or falling off cliffs, building houses, finding food and water. To survive, we most need to be able to handle matter and energy. If fields are at the bottom of it all, that's interesting, but it's not what we need to pay attention to, so as humanity grew up, our brains learned to pay attention to survival things. 

We can measure fields, but we can't perceive them directly.

So, what is mass?

In 2012, physicists at the giant international particle accelerator at CERN confirmed the existence of a subatomic particle called the Higg's boson which is responsible for the attribute of matter called "mass". It creates a field in what we perceive as matter called the Higg's field, and that is what we recognize as mass.

This exercise in weirdness is as far as we are going to go in this blog. I try to crack open the world to show you how it works, but I'm a social psychologist that just happens to have a lot of other interests and I have my limits. Do physicists actually understand the weirdness they're dredging up? Maybe, maybe not, but all they do know makes the weirdness a necessary corollary. I've also heard physicists say that, if the universe was the way it seems to be, it wouldn't exist, so we have a ways to go.

It's only fair that I don't leave you thinking that there's no mystery in the universe...that everything is straight forward and that I can just open anything up and let you see inside.

But now, I'm going to back up to the part I can poke around in and start at the beginning...pretty much the world of Newton. Things will get quite weird enough.

As Jason Nesmith says, "Never give-up, never surrender!" (movie reference, there). Physics can be weird, but don't let that stop you. Amateur scientists make important discoveries and any swimmer will tell you - going out into the deep end is fun. The Teaching Company, MIT Opensourceware, local colleges and universities, many other resources are out there waiting for you...waiting to show you how deep you can go…..oooh, scary!

Thursday, December 12, 2019

Terminus: A and R Lines

On this trip, I checked out two terminuses, Denver Airport and Peoria. Peoria wasn't that difficult. It's where their rail lines, A and R, meet. A is a commuter rail running from Union Station to the Denver International Airport and the R line is a light rail that connects the A line in Peoria and Ridgegate south of Denver. The R line also parallels the H line from Bellevue Station to Florida station.

That's Peoria Station. It's in the middle of an industrial area. Access is by streets. I didn't see any trails, so I didn't spend any more time there than a wait for the R line on my return trip. 

I walked up to Arapahoe Station and took the E line to Union Station and drank a cold brew coffee at the Pigtrain Coffee Company. I normally don't drink black coffee. It usually just tastes bitter to me, but this concoction was Coffee amplified. It was delicious.

The primary attractions on the A line commuter rail are the big, comfortable trains, the University of Colorado Denver campus, and the airport. It leaves the hills of the South Platte Valley and travels across the high plains proper. I can see a trip back this way in the future for wildlife watching. The plains also afford some spectacular views of the Rockies from a distance 

[The High Plains]

[The epitome of "snowcapped mountain majesty"]

This photograph also shows a windbreak, or snow fence along a road. The plains can have some ferocious windstorms and blizzards. On a trip to Cincinnati a few years back, Coyote, and I encountered a blizzard on the way back. We were in Kansas not far from the Colorado border and would have liked to drive on home, but this thing was blowing tractor-trailers off the icy roads, so we decided to stop overnight. That also explained the gates that could be drawn across the Interstate highway to shut it down!

I usually do a "weird Denver" hike in October but this year's move to Centennial forced me to delay it until November. Although it's easy enough to find "weird" in Denver, I had the A line terminus on my list and the airport has more than its share of weird, so it was a natural choice.

Take, for instance, the sentinel statue, Big Blue Mustang" also known affectionately as "Blucifer". I was hoping to get a close-up of this bizarre piece of art with its fiery eyes and grotesquely veiny surface (is that hardening of the arteries?) but it is surrounded by traffic and not at all easy to get to. Luckily, there is no lack of photos of this famous nightmare (uh, night-stallion) on the Internet (just search for "Blucifer") and DIT has fully owned the horse.

[Blucifer poster]

The statue earned it's widespread notoriety by killing it's creator, artist Luis Jiminez, when a segment of the unfinished statue fell on his leg, severing an artery. It is rather unfortunate that this prolific and respected artist's life and works is so overshadowed by the circumstances of his death. You may want to check out his other works on the Internet.

The horse does fit the overall modernistic trend of the Denver International Airport. The roofs of the air and train terminals are replete with interesting curved surfaces. Here is the train station.

[A line terminal]

The huge "end-cap" looming over the terminal is the Westin Hotel, and integral part of the airport structure.

The roofs on theses structures are studies in architectural curves. The canopy over the rail station is a light mesh of steel girders that look to me like a hyperbolic surface. To see how that works, hold a sheet of paper out flat from your hand and try to support something, say, a pencil with it. You can't do it. Now give it a slight curve and try again. Just a slight curve will give the sheet much greater strength. 

The structure is also an arch, funneling stresses down to the two supports and into the ground.

Lightness and strength were prime considerations in the design of the airport. I read that early designs wouldn't stand up to the plains winds and had to be scrapped.

The escalator connecting the train terminal to the airport concourse is...large. If you're acrophobic, don't look up or down. Just keep your eyes straight and don't move around and you should be okay.

If you aren't bothered by heights, enjoy the art on the wall above you. I have left a lot out of this blog. I'm not trying to leave you some surprises. I could walk around the airport all day snapping photos and still cover only a fraction of what's there to see. For instance, if you visit DIT look for the gargoyles.

The terminal itself looks like a giant tent….because it is a giant tent. The roof is said to be designed to suggest Native American dwellings on the plains or snowcapped mountains. Regardless, it's made of Teflon coated fabric and held aloft by cables in much the same way that cables are strung on suspension bridges.

[The roof of the Denver International Airport]

Controversies abound at the airport and they're alright with that, as shown by the many Denfiles posters scattered around.


Of course, the big "weird" murals help. Where I see a celebration of world cultures in an International Airport, many see cosmic relevance. Maybe I lack imagination…

[Leo Tanguma - In Peace and Harmony with Nature]

It doesn't take a lot of moving around in Denver to realize that Denver likes art. The airport is no different. It's an art museum in its own right. Check out the arts section of their website.

The plazas offer stunning views of the mountains and plains.

[Big sky]

[Pike's Peak]

And it's an airport, so I have to show one of these.

At 33,531 acres, Denver International us the largest airport in North America and the second largest in the world. It is the fifth busiest in the United States. I could wander around there for a few days and not see everything, and I will probably return. My bird watcher friend claims that there are good birdwatching areas on the property.

For variety, I returned home on the R Lightrail which connects Peoria with the Parker area. The Florida area looks like a popular shopping spot and there are several trails. It will feature in a later terminus blog.

Airports can be interesting places. I remember a sort of natural history museum with a huge, stuffed grizzly bear in the Great Falls, Montana airport, and very fondly remember the La Compass restaurant in the New Orleans airport. As many layovers I've had, I've had to find the time-killing points of interest. Is there an airport near you? You might want to check it out.

Saturday, December 7, 2019

Walnut Hill

[Sunset over the Rockies]

Last week, we moved to a new neighborhood. This week I am exploring the area. True to form, Colorado is providing diversity.

[Snowy neighborhood]

Monday, it snowed while I explored the Southeastern corner of the Walnut Hill neighborhood. The area is nearly square, bordered by four busy streets, Quebec to the west, Arapahoe to the north, Yosemite to the east, and Dry Creek to the south. Our place is close to the center of this maze of streets and this first excursion let me find a short route out to Dry Creek Road.

[Dry Creek and Spruce]

Although the interior of Walnut Hill is hilly urban forest, the perimeter offers some broad vistas of the plains to the south and east, and the mountains to the west. The snow on Monday obscured most of that. On a clear day, you can see mesas between Denver and Colorado Springs and the solitary profile of Pike's Peak in the distance.

Most of Dry Creek Road is lined by walls on both sides in this area. Although the south side borders Willow Creek, a covenant neighborhood, Walnut Hill isn't a gated community, so I assume the walls are more to keep out street noises than to keep out intruders. The people here seem to be friendly and welcoming. There is a variety judging by the diversity of banners flying in the yards.

[The Good Shepherd Episcopal Church]

Churches display a wide variety of architectural styles. Over 40 years old (according to the website), Good Shepherd is a fairly recent addition to the diocese and the building reflects it with it's rough, shingle and brick facade and vertical lines. The congregation is outgoing and friendly.. 

[Walnut Hill Park]

This strip of greenway is a convenient east-west connector through the neighborhood, bypassing most of the traffic between Yosemite and Quebec. Little Dry Creek and the adjacent trail runs through it, providing me with an easy route to Yosemite, the Denver Tech Center, Arapahoe Lightrail Station, and Arapahoe Marketplace shopping center with it's bus stops. One bus runs straight west to the shops and government centers in Littleton.

[Cascade on Little Dry Creek]

Little Dry Creek is lined in several places with rock and there are several of these rock cascades along its course. They look better than the natural clay that blankets the Denver area and the sound of water running through rock is nice, but the primary purpose is erosion control. The clay is tough (try using a shovel on it) but soft and erodes easily...rock less so. 

As water flows downhill, it expends  energy by digging into the creek bed. An obvious character of this neighborhood is it's gradient from east to west. The creek is burning off a lot of energy here. The rock cascades are placed in areas of greater slope so the creek can drop energy on granite instead of clay.

One day later…

[Little Dry Creek]

it's spring again!

This is Colorado in the fall. We're right where the North American jet stream whips around like a hooked earthworm and it draws down brutally cold air from Canada one day and warm Pacific air from the west the next.

Weather is known to be a chaotic process, impossible to predict past a certain horizon. In South Alabama, where I lived before moving to Colorado, meteorologists could do quite well a week or so in advance. They do well to make accurate forecasts a day in advance here. Alabama's secret is that they watch us. We're where their weather comes from.


Of course, the ubiquitous ducks use all the waterways in this area. Lots of waterfowl do. 

We used to be on some major migration routes for birds moving between Canada and points south but, as climates have shifted to warmer temperatures, many of the birds have decided that Colorado is a pretty nice place to just stay year round.

[The Rockies from Arapahoe]

The east-west streets in this area, like Arapahoe and Dry Creek Road, provide some pretty impressive views of the mountains. The parking lots at Arapahoe Marketplace are at a considerable elevation over the South Platte River Valley and provide some particularly nice views of Mount Evans and the mountains around it.

Just the elevation between Quebec and Yosemite here is around 75 feet (that's my elevation gain when I'm packing groceries from the grocery store to home). At home, I'm 440 feet above the river according to the National Map on the United States Geological Survey website,

A walk around the northeast corner of the neighborhood provides a good grasp of it's topography.

[Uinta Street]

The view down Uinta Street makes it quite obvious that Walnut Hill is the steep side of the valley cut by Little Dry Creek. The broad contours are the result of millennia of rare floods. The steeper gouge that the creek flows through is the result of constant scouring through the soft, sticky clay.

The clay that covers the area is the residue of weathered volcanic ash. Although there isn't much volcanic activity in the area now, There most certainly has been in the distant past (not so distant in geological terms). The two Table Mountains in Golden, ancient volcanoes, make that abundantly clear. The uplift caused by the Pacific Plate slamming into the western edge of North America, the origin of the Rocky Mountains, was a dramatic event. What we see today, the cragginess, has a lot to do with erosion by runoff, wind, and glaciers moving through the area.

But Little Dry Creek has done an impressive amount of work over the years. The elevation profile of Walnut Hill Trail gives a good idea of the drop in elevation…141 feet from Yosemite east of Walnut Hill neighborhood to Quebec at the west border. The trail has grades of up to 16. Trail grades, like most slopes are measured as rise-over-run, so that would be a slope of 16 feet up for a foot along the trail.

This profile was recorded using the AllTrails app. Elevation measures using GPS can be as much as 47 feet off in this area but comparisons with other sources like Google Earth indicate better accuracy. This profile might be around 20 feet off. 

A south-to-north profile along Spruce Street gives an idea of the shape of the valley. 

The profile isn't a straight slope down to the creek, water on the Earth's surface doesn't flow straight and, consequently, over time, the course of a stream changes and the surfaces carved into the ground are complex. Also, notice on the map that my path wasn't straight. Spruce Street is interrupted as it runs through the Walnut Hill neighborhood.

Notice that the southern slope of the valley is a lot higher than the northern slope. Well, not really. The northern slope continues on the other side of Arapahoe Road.

When I returned home, this flicker was waiting for me in my backyard. 


Flickers are related to woodpeckers and sapsuckers. We have an abundance of all these in Colorado. Thanks to my birdwatcher friend for identifying this one.

These explorations happened in the space of a week and I help out in the Christ Church Episcopal Library on Wednesdays, which gave me an interlude. I took a train back to the old neighborhood. That gave me the opportunity to look around Village Center. The Lightrail Station features a long suspended walkway over Interstate 25. I'll have to revisit that when I write a blog on bridges. This one combines a walkway suspended by cables suspended by an arch.

[Bridge at Arapahoe at Village Center Station.]

I also checked out Tower 1 at Village Center, the twenty-two story building that can be seen from all the neighboring areas. The person at the information desk was informative. He explained that the tower was an office building built in 1987. The entire top floor is occupied by a law firm, so there's no public Access, but the view from the ground is nice.

[Tower One, Greenwood Village Center]

This odd little conical Hill is just at the boundary of the Lightrail Station. It's surrounded by … stuff - not particularly scenic stuff - but it's a pretty little conical Hill with a spiral walkway to the top.

[Conical Hill]

Two of the three highest peaks in the Front Range of the Rocky Mountains, Mount Evans and Pike's Peak, are visible from this area. The highest, Mount Elbert, is also the highest in Colorado, but it's a little too far west to be seen from here.

[Pike's Peak from Walnut Hill neighborhood]

And here's Mount Evans.

[Mount Evans from Walnut Hill neighborhood]

We also have our share of raptors. This young hawk scrutinize me from his perch in the western part of Walnut Hill Park.


I frequently stop in at the Mini Moo Tea Shop in the shops along Arapahoe. They let me take a picture of their "dog".

[Mini Moo's dog]

Dry Creek Road, at the southwest corner of Walnut Hill, has some spectacular views of the Front Range.

[Front Range]

The snow capped peak to the right is Mount Evans.

I extended my walk in the southwest corner of the neighborhood along Quebec at the western border of the next neighborhood - Willow Creek. It resembles Walnut Hill in that the main topography is a creek valley. 

[Willow Creek]

On my last excursion, I noticed that Walnut Hill Elementary School has added an "A" to their curriculum. "STEM" is now "STEAM". "STEM" stands for "science, technology, engineering, and mathematics". STEAM adds "arts". There is a move to change it to STREAM and add "Reading and wRiting". It looks like we're back to the three Rs.

Your neighborhood is an adventure. Explore it.

Monday, November 25, 2019

Astronomy references

I've collected a considerable library of references over the years. Many of them are stored on my phone. The first three below are great places for ideas for projects on any of the sciences.

Science Buddies

Aimed toward school kids developing science projects, the many ideas on this website are useful for any explorer of the sciences.

Science Notebook

I've mentioned this site before. One cool thing about it is their repository of manuals from old science kits, back when they were not lame.

MIT Opencourseware

All of MIT's course materials including many of the textbooks, lecture notes, lecture videos, and even a few lab guides.

Olcott, William (1907) A Field Book of the Stars (available in various forms at the Gutenberg Project site). 

A nice thing about old do-it-yourself books is that they were printed back when people had to use what they had at hand to do things. You won't find out anything about black holes but there is all kinds of observational information.

NASA Imagine the Universe Dictionary online at useful for figuring out what you're talking about and how to talk about it.

Astronomy Merit Badge Handbook

What do you need to know to prove you know the Stars? Ask the Boy Scouts! You can look at their merit badge guides at

Astronomy Wikibook

The Wikipedia offers textbooks on many topics including astronomy at


Astro-Tom provided a list of New General Catalog objects and their observational data at . It's an Excel spreadsheet so you'll need a spreadsheet app that's compatible with Excel. 

Binocular Astronomy

Tonkin, Stephen (2007) Binocular Astronomy, Springer-Verlag, London. A guide to exactly what I'll be doing in 2020 - low power astronomical observation.


Also from Astro-Tom (see BEST-NGC.XLS above for the link), a list of data for the brightest stars in the sky.

Cambridge Illustrated Dictionary of Astronomy

Mutton, Jacqueline (2007) Cambridge University Press. 

A beautifully Illustrated dictionary of astronomical terms and bodies.

Dictionary of Geophysics, Astrophysics, and Astronomy

Matzner, Richard A. Ed.(2001) CRC Press. Articles by 52 acknowledged experts in the field.

Geometry_of_science.xls ( among many useful Excel spreadsheets, this one has a section of the intensity of light on the planets.

HERSCH.xls ( another spreadsheet from Astro-Tom. It's the Herschel 400 listing.

Isaac Asimov's Guide to Earth and Space

Asimov, Isaac (1991) Fawcett Books
A lot of astronomical, physical, and geological information from the master of scientific popularization.

And more spreadsheets from Astro-Tom providing much observational data.













Your New Telescope: The Good, The Bad, and the Ugly

This is a page by Tom Koonce on the Astro-Tom website (

Physics - From Stargazers to Starships

Stern, David P.  And Alex A. Zaliznyak (2023) CK-12. 

This CK-12 textbook focuses on the physics of space, written at a beginner's level and in a very readable style. How did astronomy get started and how did it get to where it is today?

Schaum's Outline: Astronomy

Palen, Stacey (2002) Schaum's Outlines: Astronomy. McGraw Hill.

As always, Schaum's Outlines are great study resources, dense with information, examples and problems, worked and unworked.

Taki's 8.5 Magnitude Star Atlas

Toshimi Taki (2006) Can be downloaded from Taki's website with lots of other information here

MIT 12.409 Hands-On Astronomy

Star Date Online

This website is great for keeping up with what's going on I'm the sky and in astronomy.

A Simple Guide to Backyard Astronomy Using Binoculars or a Small Telescope

Beigel, Carol (2007) available at (accessed 10/17/19)

This is a nicely packaged reference for the amateur astronomer.

Night Sky - A Falcon Field Guide

Nigro, Nicholas (2012) Morris Book Publishing. 

All the Falcon Guides are fairly complete, portable, and inexpensive. Not a lot of technical information, but that's why all the other references.

Sky Watching. The Teaching Company
Alex Filippenko (2011)

I highly recommend the lecture series (buy it when it's on sale). It's beautiful and packed with information from someone who knows what they're talking about, but the course guide that comes with the videos should definitely go with you into the field.

A Visual Guide to the Universe
The Teaching Company
David M. Meyer (2014)

A gorgeous guide to the Universe through the lenses of our orbiting telescopes.

Understanding the Universe: An Introduction to Astronomy
The Teaching Company
Alex Filippenko (2007)

The astronomy course from the teaching company. It's a great start to you career in astronomy.

I'm all about getting out of the house to learn about the world, but the best place to start is in the library...yours or the one down the street. Get a preview before you hit the trail.

Friday, November 22, 2019

Astronomy tools

Again, I try to keep my equipment portable and inexpensive. You won't get clear, crisp photos of the crab nebula with my setup, but you might be surprised what you can do with it.

As always, my central and most expensive piece of equipment is my computer, currently a…..

Motorola Moto E5 Cruise phone

In preparation for excursions into astronomy next year, my phone is packed with camera and astronomy apps and I have loaded my SD card with astronomy field guides.

This phone has 16 gigabytes of internal memory and an added SD card with another 31 gigabytes, plenty for my purposes. It's moderately priced (between $100 and $200 dollar) and it even serves as a phone!

The camera gives nice results with 8 megapixel resolution plus video and will magnify to 8 times (though the result at 8x is grainy).

Camera hardware

I supplement my phone's camera with a fanny pack full of hardware that I've collected over time including phone clamps, assorted tripods from  desk-size to an eight foot tall tripod. I also have an assortment of standard quarter inch screws, nuts, and bolts that I can use to attach the phone-camera to hardware that isn't particularly for cameras, like Erector set parts and pipe clamps.

I've also collected microscopic, telescopic, fish-eye, etc. lenses and eyepiece adapters for my assorted binoculars, monoculars, and rifle scopes. All this "stuff" is inexpensive at places like American Science and Surplus, Home Science Tools, and numerous other suppliers that cater to the backyard scientist.

The a packrat.

Open Camera

Mark Harman

The camera in my Android phone isn't all purpose but camera apps are inexpensive or free and they all have their special features. The camera that came with my phone is great for point-and-click photography, but there aren't many bells and whistles. 

The Open Camera app allow quick series of shots and allows for time/date/location stamped photos. It also provides slow motion and Bluetooth shutter release capabilities.

Snail Camera

The Snail Camera app is very flexible with lots of color, contrast, etc. settings. Practically anything you can do with a DSLR camera except change lenses (but see the mention of my packrattery above.)

It even lets you take multiple and extended exposures. The timed exposure is important for astronomy because you will be trying to capture some dim images.

Note: astronomy requires a remote shutter release and stable mount. With telephotography, barely touching the camera will move it quite enough to lose the object you're photographing. The tripod should also have fine adjustments because aiming a phone camera with a telephoto lens is hard enough.

USB Camera app

Infinitegra Inc.

This app, plus a USB to microUSB plug converter lets me connect other cameras and webcams to my Android. This doesn't work with some smartphones (it requires the phone to be otg, On The Go, enabled) but it's had no problem with my Motorola. If you wonder if you're phone has the right software, there are free apps that you can download (if you have an Android phone, the Google Play store will have what you need) that will test for otg.

Heavens Above

Chris Peat and Jen's Tinz

This app will keep you up to date on things happening in the sky including satellites and their tricks, like Iridium flares.


My favorite astronomy app, the Stellarium is a planetarium you carry with you on your phone. There are also versions for laptops and desktop computers. It will orient you to where you should look in the sky and, like big planetariums, it's loaded with educational extras.

Night Sky Guide

Shiny Objects LLC

This is a no-frills table of observable objects and where to observe them, plus an observation log that you can save as a csv (comma separated values) file.


Sky map, calendar, astronomy news, image gallery, compass, and periscope all rolled into one package. (The periscope tells you where the sun, moon, and planets are right now, indoors or outside.)


Atmospheric conditions are important for skywatching. Pollution, dust or light, can create a beautiful sunset, but they can also wreck an astronomical outing. This app provides a summary of weather and predictions for your area.

That's a lot of apps but they will all fit on one phone and are all free or inexpensive. They are programmed for an Android phone but many have versions for other kinds of phones, tablets, and laptops. If not, there are probably similar products that you can find with a little Internet search.

That's my lineup, Track down yours and join me for a year of sky watching and physics.

If you find references or equipment that you just can't do without, add a comment to the blog to let us know about it.

Tuesday, November 19, 2019

Physics references

I've collected a considerable physics reference library over the years. Much of it is portable, either as ebooks or in my Kindle reader. Here's an annotated bibliography. Some items may no longer be available. Many are free downloads, but most of the books are fairly inexpensive and remember that your public library may have any or all of them.

Science Toys

This website by Simon Quellen Field is an excellent source of projects in several fields of science. They are generally inexpensive and use readily available parts, but some require considerable work and assembly time. They are all well explained.

Science Notebook

This website reminds me a lot of the Engineer's notebooks by Forrest Mim's. It's oriented toward children and beginning science explorers - much of the material is very basic, but one of the fascinating things is that they include a library of manuals from old science kits. See how they don't make science kits like they used to.

MIT Opencourseware

You get all the course materials the MIT students get (except the items they have to buy) often including textbooks, lecture notes, and recorded lectures. What you don't get are the credits.

BYU Optics Book

By Justin Peatross and Michael Ware. 

Get the latest edition at

This is the textbook used at Brigham Young University for Optics classes and it delves as far as you might want to go. Expect advanced math.

CK-12 Basic Physics

CK-12 People's Physics Book

CK-12 is an organization that makes quality textbook (kindergarten to high school level) available free. The books can be obtained from dealers like Amazon or in online, interactive format at the CK-12 website:

There are also several other CK-12 physics textbooks and other learning materials.

Common Equivalents Weight and Measures ( Santa Clara County provided a nice table of weights and measures. Another option is the Google unit converter. Just type "convert" one unit "to" another unit (for instance "convert inches to centimeters") into your browser search bar.

CRC Handbook of Chemistry and Physics

John Rumble, editor in chief

Published by CRC Press

Now in it's 99th edition, this monster tome is useful as a doorstop or weapon, and it also has every table imaginable that a normal person might want for scientific inquiry. New editions are sorta expensive but older editions can be found, especially in college bookstores or online for less than $20, and it's well worth every penny

Forrest Mims library. Remember the Engineer's Notebook series - those tiny paperback books sold at Radio Shack that were loaded with information for electronics hobbyists back in the 70s and 80s? They are still available here

And here

And at Amazon.

Although I will get around to electronics, it's really useful to be able to create your own equipment and these tiny, inexpensive books are just what you need.


Stands for "Free high school science textbook" and it's a Wikibook available here

Fundamental Optics

Published by CVI Melles Griot, this book is the reference of optical information. Find it at

Make:The Annotated Build It Yourself Science Laboratory

Raymond Barrett and Windell Oskay (2015) published by Maker Media, Inc.

Way back in the 60s Raymond Barrett produced an amazing book that wowed science enthusiasts by showing them how to build things like carbon arc furnaces and cloud chambers. Now you can get an annotated edition created by Windell Oskay. Double wow!

Mathematical Tools for Physics

James Nearing

Available at

This is an extensive university level textbook of mathematics for physicists.

Electrical Engineer's Portable Handbook

Robert B. Hickey

2nd edition (2004). McGraw Hill

Just what it said, it's a reference book for electrical engineers.

Mechanical Engineer's Handbook

Myer Kutz, editor

(2006) John Wiley and sons

Another reference tome, this time for mechanical engineers.

Nuclear Science Merit Badge Handbook

What do you need to know to qualify for a Boy Scout merit badge? Well, first, be a boy scout. Next, check out this site:

And, yes, there are requirements for various fields of physics, but they change, so keep up.


You might notice that I recommend several spreadsheets. If you have the software to read them they can be a lot of help. Several such phone apps are available. The spreadsheets might or might not be online at this writing so, do a search and, if you don't find the one I reference, there's probably an equivalent one somewhere.

Physics Study Guide (Wikipedia website) The Wikipedia offers this concise and extensive college level physics Study Guide at:

Physics Wikibooks. They also have a wide range of Wikibooks (free textbooks) here:

Schaum's Basic Electricity: Schaum's Outlines are all good - concise, complete, inexpensive, full of solved and unsolved problems, and written by acknowledged experts. What more could you want. A few more of the many titles in physics are….

Schaum's Easy Outlines: College Physics

Schaum's Electronic Devices and Circuits

Schaum's Outline of Optics

Schaum's Outlines: Thermodynamics for Engineers

Schaum's Outline of Theory and Problems of Basic Circuit Analysis

temperature_scales.xls I have one from

But similar spreadsheets are all over the Internet.

Turning the World Insideout (1990. Robert Ehrlich. Princeton University Press)

I keep this one with my field guides. The excellent demonstrations are inexpensive, mostly "simple" enough to be portable, and theoretically both deep and well written (understandable). This book is a treasure.

The next two items are user guides for two of my favorite science explorer apps, so see my blog on Physics Tools for more information. Both have great ideas for experiments and demonstrations in all the sciences.

Physics Toolbox Play User's Guide (by APD net and available at )

Getting Started with Google Science Journal. Check out the Google Science Journal website at .

Understanding the Quantum World

The Teaching Company

Erica Carlson

Particle Physics for Nonphysicists

The Teaching Company

Steven Pollock

Physics and Our Universe. 

The Teaching Company

Richard Wolfson

Understanding Modern Electronics

The Teaching Company

Richard Wolfson

And lots more. Frankly, all of the Teaching Company's courses are excellent. They won't get you to the practical level of an engineer, but you'll learn a lot. The presenters are experts in their fields, so the lectures provide very up to date information. Also, the sets are expensive but the Teaching Company places each of them on sale at least once a year so, with some patience, they're quite affordable. And many public libraries carry them.

Check out their website.

Physics can be fascinating and fun as a study or a hobby. Engineering is applied physics so, when you design and build something, you are using your knowledge and skills in physics. Check out the resources in your local library. See what you can find on the Internet. See if physics is for you, and join me next year for adventures in physics.