Terminus: Boulder

It was a nice day to take a walk.

This terminus hike was different in that it wasn't a train terminal. There is a fleet of buses that run regularly from Union Station in Denver to Downtown Boulder Station in Boulder. Designated FF1 through FF7, they make different stops on the way. FF2 is the express, so I took it out. "FF" stands for "Flatirons Flier" named after the huge outcrop of iron laden sandstone that looms over Boulder.

[Flatirons from downtown Boulder]

Unlike the commuter buses that run in Denver, the Flatiron Fliers are comfy cross country buses. I almost expect a steward to come out on the way and offer little cups of soda and peanuts. It's a long ride, but a nice one through the mesa country north of Denver.

The Fliers run through the first area I lived in when I moved to Colorado, Broomfield. Looking back through the blogs, you can find past hikes I took near Superior, Colorado and Flatiron Junction.

Downtown Boulder looks a little "small town" but the city is home to a very big school, the University of Colorado, and it's a major Colorado tourist destination. Situated at the mouth of Boulder Canyon, it's a gateway to the Rockies known for its shopping and nightlife.

Watch the traffic - it's also known for reckless drivers.

From the bus station, I walked down to the little bandshell amphitheater located on Boulder Creek. Boulder Creek Trail parallels the creek through town and into the canyon. It's well traveled by students, tourists, and resident joggers, but not such that it's not a corridor for wildlife. The town loves its animals. It's the first place in the US to give pets the status of personhood.

Boulder Creek Trail is a nice walk, ending at the west end in Eben G. Fine Park. Eben Givens Fine was a community builder who moved to Boulder from Missouri in 1886 and took a job as a pharmacist in a local drug store.

[Boulder Public Library from Boulder Creek]

[Boulder Creek]

[Boulder Creek at Eben Fine Park]

A tunnel under Canyon Road connects Eben Fine Park with Settlers and Red Rocks Park. "Red Rocks" may sound like plagiarism. After all, Red Rocks Park is near Morrison, but, in fact, it's the same Red Rocks, known also as the Fountain Formation, that pops up in places along the Front Range from Wyoming to New Mexico. The red rock is arkose conglomerate and the "red" is mostly iron rich feldspar that was recrystallized under pressure from stuff washed out of the mountains after the uplift that formed the Rockies. [Correction. It was debris from the Ancestral Rockies. ]

(By the way, if you're curious, the word "plagiarism" is from the Latin word "plagiarius" which means "kidnapping".)

[Red Rocks at Red Rocks Park in Boulder]

I returned to the bus station along Pearl Street, especially known for its shops, restaurants and nightlife.

[Pearl Street]

Since I was in no hurry to get back home (I needed a rest and the hike was short - it was just a little after noon when I left Boulder.) I took the first Flatirons Flier to leave, the FF1, which stops at pretty much every stop along the route. 

Meanwhile...

Obituaries are a thing.

America is an odd culture. We avoid the topic of death like a plague yet the Internet is packed with discussions of people who read the newspapers (and Internet) obituaries everyday of their lives and why they do it. A cursory examination of Google Scholar did not turn up any studies, nor could I find any data, on people who read obituaries.

There are many citations on Google Scholar about obituaries, though...how to read them, how to write them, how and why to research them, what they tell us about the people they discuss, what they tell us about society in general.

It's interesting reading. You might take some days to study obituaries.

Why am I talking about them? 

Well, it's a lead in to my excuse for my absence from this blog for a couple of months.

First, a very close friend died. Learning can be…somber, but it's always potentially edifying. I learned that, as you get older and old friends die off, it gets easier to shrug it off. Bereavement is about loss, not pity for the deceased. After you loose enough, you get used to it and life teaches you that everything isn't necessarily about us. The world goes on.

When you know you are dying, you can either say, "I'm dying," or "I'm going to live until I die." Mike showed that it is entirely possible to do the latter with all the determination of a 20-something with nothing but life ahead of them. Another person I knew who "died well" was my father. You can learn a lot from folks like that.

A week later, I went to church and couldn't sing. The next day, my annual episode of bronchitis was in full swing. I have learned to expect it every year. Some truths are just nasty. So, for a month, I sat around hacking my brains out and wearing myself down.

A close friend and college math professor was scheduled to attend a mathematics conference in town and I had said that I would go with him. It was the week after my hacking cough had let up and I was flat worn out but I keep my word, and I really did want to go since I'm an amateur mathematician and it would give me something to blog about. I had the opportunity to go as his guest, which meant a 95% discount. On my pension, it was an offer I could not refuse.

Of course, it was mostly sitting through lectures and strolling around math art exhibits and vendors (I bought gifts for folks). There was a surprising lot about my own, not so deep interests - math education and statistics. So, at least I enjoyed further abrading my life force. And I got some close-ups of the big blue bear.

At least, between bear and horse, the more personable one is the more accessible.

Finally, I'm on the mend and I've even knocked out another terminal hike (that leaves three to go) and that will be the subject of my next blog.

I recommend not avoiding mental adventures like community lectures and conferences because you think they will be boring. It's all mindset. Things that you expect to be boring usually are.

Shake out the obituary section of a newspaper. Look at some obits online. Do they have a consistent structure? Do you know an obituary reader? If so, why do they enjoy reading obituaries? What do obituaries tell us about our attitudes toward death? What do obituaries tell us about our attitudes toward life?

Orbits

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.

[Swarms]

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.

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!

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.

[Controversies]

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.

https://www.flydenver.com/about/art_culture/program

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.

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.

[Ducks]

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, https://viewer.nationalmap.gov/advanced-viewer

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. 

[Flicker]

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.

[Hawk]

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.