Don’t Try to Predict Physics (or Much of Anything Else) Without a Model

Don Warrington Mathematics 1 Comment

A salutary note at the end of Rutherford Aris’ Mathematical Modelling Techniques:

When a model is being used as a simulation an obvious comparison can be made between its predictions and the results of the experiment. We are favourably impressed with the model if the agreement is good and if it has not been purchased at the price of too many empirical constant adjusted to fit the data. If the parameters are determined independently and fed into the final model as fixed constant not to be further adjusted, then we can have a fair degree of confidence in the data and in the model. Both model and data have their own integrity the former in the relevance and clarity of its hypotheses and the rigour and appropriateness of its development, the latter in the carefulness of the experimenter and the accuracy of the results. But these virtues do not only inhere in the possessors they also gain validity from the other…Thus the attitude of never believing an experiment until its confirmed by theory has as much to be said for it as that which never believes a theory before its confirmation by experiment. (emphasis mine)

In the comparison of theory with experiment an array of statistical tools is available and should be used. One danger that is easy to overlook is the existence of hidden constancies that will give spurious values…The classic correlation between the intelligence of the children and the drunkenness of the parents which so confounded temperance societies years ago–until it was discovered that all the data came from schools in the east end of London–is another illustration of a data base too narrow to test a model.

As someone who works in the earth sciences, the indiscriminate use of statistics and purely empirical relationships is maddening, and that has spread to many other disciplines as well. The computer power we have at our disposal these days makes it too tempting to simply reduce “big data” and let us “tell us” what’s going on, but this can be a serious mistake without some kind of hypothesis–right or wrong–about what we are looking at.

Chauvenet’s Criterion

Don Warrington Video Fluid Mechanics, Mathematics 1 Comment

In the pressure gauge testing lab experiment, one of the requirements is that the “outliers” in the data are determined and excised from the analysis. One way of doing that is to apply Chauvenet’s Criterion. Below is a video of how that’s done and who Chauvenet was.

Note: he butchers the pronunciation of Chauvenet, sorry.

The Yellow Flag of Quarantine

Don Warrington Yachting Leave a comment

Ships have used flags for signalling for centuries. One of the more obscure flags is the Quarantine Flag, the purely yellow flag shown above. It’s a specialised flag like the better-known diver’s flag. Its use has changed over the years; a brief summary of that use comes from here:

There is no signal in the International Code of Signals for ‘quarantine’ (indeed the word ‘quarantine’ does not appear in the code). Today ships signal either ‘ My vessel is “healthy” and I request free pratique’ with a single Q (Quebec) flag or ‘I require health clearance’ with the double signal QQ (Quebec Quebec). Either is correct for a vessel yet to be cleared for pratique (pratique is permission to do business at a port, granted to a ship that has met quarantine or other health regulations). The Q (Quebec) flag is square in shape and pure yellow. Continuing to fly either of these signals indicates a vessel is yet to receive clearance (and is thus effectively in quarantine). Once the local authorities have determined that the ship’s health problems have been resolved and removed a quarantine order, the ship may strike the signal and raise the national ensign for the port they are entering.

In the days of COVID-19, this flag should be getting a workout. So if your vessel (or house, etc.) is under quarantine (like some of the people taking this course) you should strike whatever flag you might be flying and hoist this one.

The Joys of Bitter Lemon

Don Warrington The Palm Beach Experience 4 Comments

I grew up in a family of serious drinkers, which goes back a long way, as my grandfather’s involvement in this should attest.  That meant that we had a stocked bar in the house (it wasn’t a “wet bar” in the sense that it had a sink, but it was stocked all the same.)  At the same time I was an accomplished snacker, and an opportunistic one at that.  Maraschino cherries and stuffed green olives that were ostensibly intended for my mother’s gin martinis (this was before the vodka ones became de rigeur) ended up going “down the hatch” of the youngest inhabitant of the house, save the cat.

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A drawing from the archives of Vulcan Iron Works, which combined the engineering activities of the employees on the job with their activities after hours. It’s worth noting that the first office Vulcan had in West Palm Beach was adjacent to a bar.

To wash all of this down, I turned to yet another thing that was stocked in the bar: Schweppes’ Bitter Lemon and, sometimes, Bitter Orange.  Bitter Lemon/Orange was basically tonic water (which includes quinine) with the suitable citrus drink. It was stiff stuff for the “Pepsi Generation” but I drank it anyway and liked it.

In recent times I’ve always wondered what happened to these interesting soft drinks.  Research on the internet showed that Schweppes certainly still makes them but doesn’t distribute them in the US; inhabitants of the UK, Singapore and Australia still were able to enjoy this, but evidently Americans’ obsession with things being sweet killed it in this country.

The advent of COVID-19 and the fracas over hydroxychloroquine–and its relationship to quinine, which the British used to dampen the effects of malaria–got me thinking again about this stuff.  Why not?  So my wife and I got to mixing things and, with some help from my country club, got things rolling there and at home.

There are elaborate recipes out there to make it, some involving things like lavender, others adding sugar or other sweeteners.  For me the latter kills the whole appeal, and in any case most tonic water we get here (we usually get it at Publix, from its Florida roots the drinkers’ choice for grocery stores) is sweetened, as it comes in either regular or diet forms.  With orange I’ve been ordering 3:1 tonic water:orange juice; with lemon concentrate you don’t even need that much.  It’s definitely a face slapper but that’s the appeal, especially for someone who listed his favourite coffee as Sumatra.

It’s also possible to use other fruit drinks.  We actually started with cranberry juice, which isn’t bad, and we’ve also tried lime juice, and that’s in some ways better than lemon.  We have a friend from Guatemala who’s going to try apple juice, and that should be interesting.

And what of COVID?  I think the whole stink over hydroxychloroquine is proof as to how unscientific (and corrupt) our culture has become.  Setting aside the mercenary power of Big Pharma, everything in this debate–masks, face shields, social distancing, you name it–has been presented as “preventing” the spread of COVID-19.  But, as I explain to my Foundations students, finding that kind of deterministic absolute is impossible.  We’ve always “played the odds” with what we do in the material world.  (The other side is different.)  My wife and I have done our part with the masks, social distancing and “hiding out” (the appropriate TN term for sheltering in place,) and it’s paid off.  But things we can do to help things along, some nutritional, some like this–can’t hurt and may make the difference.

In any case I’m having a blast in these troubled times.  Cheers!

On His Level

Don Warrington Uncategorized 1 Comment

buffdor1

Buff. Behind him is the sliding glass door where he met disaster.

Readers of this blog have seen the antics of our Applehead Siamese Cat, Buff, who in his day braved both photographers and the high seas.  Shortly after we left Palm Beach for Boynton Beach he taught us yet another important life lesson, and as usual he did it the hard way.

Florida living has some unique benefits.  One of those is those screened in porches (screened to keep the mosquitoes out) with access from the house through sliding glass doors.  The climate makes sitting out on them a delight.  We didn’t have them in our house in Palm Beach but we certainly did in Boynton Beach.

We bought the house new, so my mother (recovering from back surgery) had to decorate it.  One of the things you do with sliding glass doors is to purchase these “peel and stick” appliqués and put them about eye level so people won’t run into the door.  (The alternative is to keep the door so dirty no one can miss them, but…)  She did this, but she didn’t take into account everyone in the house.

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Looking back through the same door. An appliqué can barely be seen on the left edge of the photo.

Buff had the delightful habit of running through the house, making a thundering herd kind of noise (this is amazing for animals known for their stealth.)  His vision, as is common with Applehead Siamese cats, wasn’t the best, so he didn’t always know where he was going.  One night we were sitting around listening to the thundering herd when we heard an unsatisfying thump on the sliding glass door.  It seems that Buff, not seeing or caring about the door, had careened into it.  He staggered away; he wasn’t himself for several days thereafter.

This incident made its point, so my mother got yet another set of appliqués and put them towards the bottom of the door so Buff could see them before he had another wreck.

In communicating a message to someone, it’s important to deliver it in a way that they can understand and benefit from it.  It’s called sometimes “getting down on their level.”  That’s what we had to do for poor Buff; appliqués placed high up didn’t do him much good.

When God wanted to redeem people from their sins and make them into the children he intended them to be in the first place, he himself — he did not send someone or something else — came down to be on our level, in Jesus Christ his Son:

Though the divine nature was his from the beginning, yet he did not look upon equality with God as above all things to be clung to, But impoverished himself by taking the nature of a servant and becoming like men; He appeared among us as a man, and still further humbled himself by submitting even to death–to death on a cross! (Phil 2:6-8)

Jesus, in the days of his earthly life, offered prayers and supplications, with earnest cries and with tears, to him who was able to save him from death; and he was heard because of his devout submission. (Hebrews 5:7)

Some religions tell us that it was not worthy that God come down and live with us, as his Son or otherwise.  But the truth remains: the best way to make an alliance between God and people is for God himself to come down on our level, where we could not only behold his glory (John 1:14) but that he could both share and transcend our condition and make a way for us from this life into eternity.

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All New Testament quotations taken from the Positive Infinity New Testament.