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2017 September 6

Wilder Ranch

Filed under: Uncategorized — gasstationwithoutpumps @ 11:27
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Yesterday, my son and I took a bike ride through Wilder Ranch State Park and UCSC.  We had a fun, though somewhat warm ride.  The weather was unseasonably hot over Labor Day weekend, hitting an all-time high for Santa Cruz of 108°F.  We were promised cooler weather on Tuesday, but the temperature was well over 80°F at noon.  We waited until 1:30, when the temperature finally dropped below 80°F before leaving the house.

We headed out on the paved bike path to Wilder Ranch, up Engelman’s Loop  and Long Meadow Trail to the Chinquapin Trailhead, then across Empire Grade to UCSC property, down past the Painted Barrels (there are actually two sets of barrels—Google doesn’t map the more northerly set, which were just after we entered the woods again from Marshall Field).  On the way down from campus, we stopped at the overlook above Pogonip Park and at the UCSC farm stand, where I bought some apples, cauliflower, and flowers.  The farm stand seems to have less produce this year than in previous years—I don’t know whether this is because the farm is producing fewer varieties or that they have better marketing outlets elsewhere.

Because we were doing the ride mid-week, we saw only a few other bike riders—maybe 5 or 6 on the paved path out to Wilder Ranch, one couple on the trails in the park, a pack of middle schoolers with adult guides on the UCSC trails, and a few bike commuters on the UCSC roads.  I suspect that the Wilder Ranch trails are more populated on weekends.

A map of our route. It was 13 miles (21 km) with 1178 feet (360m) of climbing.

I used Google Maps to make a route map of the route we took, which was harder than I expected.  At first I just dragged around intermediate points using Google directions, but Google kept throwing out the route.  Then my son pointed out that I could use the “+” button in directions to grow the route incrementally, though that required  couple of tries to work also, as there is a small limit on the number of points you can add, so I had to be very choosy about which points I added.

The weather was really a bit too warm for strenuous exercise, but we had cloud cover for much of the ride, so it wasn’t as bad as it could have been (certainly not as bad as last weekend would have been).  Today might have been a better choice, as the hot weather seems to have ended and we’re back to more normal temperature swings.

Neither of us have mountain bikes—my son rides a commuter bike with narrow road tires, and I have my Vanguard long-wheelbase recumbent.  The loose gravel, deep dust, and ruts of the trails in Wilder Ranch were a little difficult for us to handle, though mountain-bike enthusiasts would have found them tame.  I had to get off and walk my bike on a few steep hills, because I fell below my minimum balance speed and couldn’t start again on the loose gravel.  I only fell once—trying to get out of a rut on a steep uphill and falling below minimum balance speed.

It would have been good to do more bike riding this summer with my son—he’s headed back to UCSB in just over 2 weeks, and we’re making a trip to Boulder to see my Dad next week, so I doubt that we’ll have time to schedule another bike ride.


2012 June 8

Reporting bugs in books and web sites

Filed under: home school — gasstationwithoutpumps @ 08:07
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Yesterday, while working problems in Chapter 12 of Matter and Interactions (about entropy and temperature),my son and I each found a bug.  The one I found was in the book, the one he found was in Wolfram Alpha.  I reported both of them to the respective sources.

Here is the exchange with Bruce Sherwood, one of the authors of Matter and Interactions.  Last night I wrote

I was doing the entropy calculations for 12.P.40 and decided to see if the number of states values were consistent.  I found that they were consistent with having 170 oscillators, which made the choice of 100 atoms seem strange to me.  What arrangement of atoms gives only 170 degrees of freedom for 100 atoms?

In just over an hour, Prof. Sherwood responded

Thanks! It’s clearly an error. And I note that with 170/3 = about 57 atoms, the per-atom heat capacity is about 2.8e-23 J/K, still less than the classical 3k_B limit, as is expected for the low temperature (about 113 K).

The simplest way to “fix” this would seem to be to say in part (c) that there are 57 atoms in this nanoparticle. Would you agree? You might be the only person in the world who has gone to the trouble to check whether the “100 atoms” made sense, though I would like to think we did a reality check on this in making up the problem but made a mistake.

While I’m pleased by how quickly he responds to my comments and that I apparently worked the problem correctly (all  this quantum mechanics is new to me), I’m a little disturbed by the assumption that I’m the only one checking my physics homework problems for consistency.  (Though since no one else has previously reported the problem to Prof. Sherwood, his assumption may well be correct.)

The problem my son found was in doing 12.P.48, which gives a mechanics problem that involves forces, rotating objects, and a brake.  The problem ends with a computation of how much the iron masses heat up as a result of the energy dissipated by the brake.  We  both used the 3 k_B high-temperature approximation of the atomic specific heat of Fe, getting a molar specific heat of about 25 J/(K mol), which should be fairly universal for simple solids at high temperature.  He looked up the specific heat of iron on Wolfram Alpha (his go-to source for numeric and mathematical information) and found that they had the molar specific heat as 251 J/(K mol).  He came to me for help, because he couldn’t find an error in his computation.  I suggested looking at some other references on the web.  They all had values around 25 J/(K mol), so I reported the apparent data entry error to Wolfram Alpha, suggesting that they should have done consistency checks on their molar specific heats.  I’m amazed that we seem to be the first ones to have caught this error—has no one ever used this entry in Wolfram Alpha’s database? Does no one do consistency checks on the data they find on the web? (I know that consistency checks on data entry are often done, but things slip through even well-designed data screens.)

So far all we have from Wolfram Alpha is the robomessage:

We appreciate your feedback regarding Wolfram|Alpha. The issue you reported has been passed along to our development team for review. Thank you for helping us improve Wolfram|Alpha.

But we can hardly expect commercial companies to work the sorts of hours that professors do, nor to admit to errors without piles of internal bureaucracy.

Of course, Wolfram Alpha is not the first web source whose information I’ve attempted to correct.  I have frequently sent Google Maps corrections on the bicycle routing information in Santa Cruz.  They usually respond in between 2 weeks and 2 months, and usually agree that I’m correct and claim to have fixed the problem.  About half the time they have fixed the problem, but one remains persistent—they keep sending bicyclists up the downhill-only leg of the bike path on the UCSC campus, though they have twice claimed to have fixed the problem.  The bike path is on a steep hill and is divided like a freeway, with the uphill path going around the hill and the downhill path going over the top and straight down.  Because the path is fairly narrow and downhill speeds exceed  35 mph, it is extremely dangerous to be routing bikes or pedestrians up the downhill path. The path is dangerous enough for downhill riders (I lost my spleen in a solo crash coming down that path in March 2000) without oncoming traffic.

I suspect that Google Maps has a database representation problem, lacking the ability to code a route as both one-way and bikes-only, so the fix may require more development work than the QA staff is authorized to do—that’s why I always check to see if it has really been fixed as they claim.  Their repeated reporting of the problem as fixed when it clearly is not indicates a serious management problem among Google Maps QA staff, who probably are evaluated on how many problems they clear, with no check for whether the problems are really resolved properly.

2012 January 19

UCSC the only UC with Google virtual tour

Filed under: Uncategorized — gasstationwithoutpumps @ 17:36
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According to Google’s Street View University Partners – Maps Help, the only University of California campus that currently has a virtual tour is UCSC.

The “virtual tour” is not a tour so far as I can tell, but heavy Street View coverage of the campus.  The coverage of UCSC campus is adequate, including major roads and the bike paths, but not including many of service roads and footpaths that a real tour would cover.  It would be good for Google to hire a student to walk a number of the paths (particularly some of the single-track trails in the woods, which are not properly mapped) with a geotagging street-view camera, to capture the campus more thoroughly.

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