Pi Day. That time of the year has come full circle.

Written by Jasper on March 13, 2011 · View Comments

In honor of our favorite con­stant, I’ve pre­pared a lit­tle poem.

Ahem.

You must have heard about 3.14…
In many cir­cles she’s all the rage.
She’s the greek char­ac­ter that we all adore,
whose irra­tional nature takes cen­ter stage.

Defined by divi­sion, as opposed to sum,
(a fact that is known through­out the land).
But don’t count on her with your fin­gers and thumbs,
she flaunts more dig­its than you have on your hand.

Men fight to reveal her dec­i­mal places,
– around 2.5 tril­lion is the cur­rent amount.
A com­plex atti­tude is not what she embraces,
but, she’s a real num­ber, and that’s what counts.

I hes­i­tate to sound slightly cliche,
but she’s a hero unhonored and unsung.
And after all, it’s true what they say:
two Pi is greater than one.

yes…

 

Categories: Fun - Tags: , , ,

Science is a life skill | Technobabble

Written by Jasper on February 21, 2011 · View Comments

Peo­ple like me keep telling oth­ers to be skep­ti­cal and think crit­i­cally about fac­tual claims over­heard on the inter­net, mass media and even from friends and rel­a­tives. And I actu­ally think peo­ple are start­ing to catch on. Prob­a­bly thanks to the num­ber of “not quite true” adver­tise­ment mes­sages peo­ple get exposed to on a daily basis. But how can one actu­ally be skep­ti­cal about impor­tant fac­tual claims when even rig­or­ous sci­en­tific results are so dizzy­ingly incom­pre­hen­si­ble? How can you tell the dif­fer­ence? How can you be con­fi­dent in your per­cep­tion of the facts? Some­times — at least to me — it feels like you’d need a Ph.D. in sev­eral fields of sci­ence to sat­isfy your skep­ti­cism of all the claims fly­ing around!

Let’s start on a light note, with a video…

YouTube Preview Image

This is a video put together by one of my favorite sci­en­tific youtu­bers. Although I’m unsure of his name, he calles his youtube chan­nel C0nc0rdance.

While to most peo­ple — espe­cially those with a sci­en­tific back­ground — this video may be painfully funny, I hope that at least some detect a rather fright­en­ing ele­ment illus­trated in this video. Let me elaborate…

As a sci­en­tist (and espe­cially as a physi­cist), when I look at this video, I under­stand most of the words that fall out of these people’s mouths — yes, even in the Star Trek scenes. And to me, the sen­tences sound no more sen­si­cal than: “Pork pie scis­sors affect the banana glands which embi­gens the heal­ing power of home­opa­thy”. Hav­ing a knowl­edge of the mean­ing of these words allows me to eas­ily dif­fer­en­ti­ate between tech­nob­a­b­ble and a log­i­cal expla­na­tion. I’m sure those of you who have a cer­tain knowl­edge of sci­en­tific terms also sym­pa­thize with that position.

But let’s imag­ine that I hadn’t done a degree in physics. Imag­ine I hadn’t kept up to date with cur­rent dis­cov­er­ies in sci­ence. How would I be able to tell what was sci­ence, and what was non-science (or nonsense)?

I doubt many of my read­ers find it dif­fi­cult to pin the tail to the crack­pot claims in that video… but per­haps there are some. To those of you I say, don’t be too hard on your­self. Some­times, crack­pot claims are much more sub­tle and harder to spot.

Let’s con­tinue with a harder example…

Con­sider the fol­low­ing two abstracts. The first was accepted in the APS Physics Jour­nal (1990), and the sec­ond was accepted in the World Multi-Conference on Sys­temics, Cyber­net­ics and Infor­mat­ics (2005).

The Chern-Simons Lagrangian has been stud­ied pre­vi­ously in (2+1)-dimensional space­time, where it is both gauge and Lorentz invari­ant. In 3+1 dimen­sions, this term cou­ples the dual elec­tro­mag­netic ten­sor to an exter­nal four-vector. If we take this four-vector to be fixed, the term is gauge invari­ant but not Lorentz invari­ant. In this paper, we exam­ine both the the­o­ret­i­cal con­se­quences of such a mod­i­fi­ca­tion and obser­va­tional lim­its we can put on its mag­ni­tude. The Chern-Simons term would rotate the plane of polar­iza­tion of radi­a­tion from dis­tant galax­ies, an effect which is not observed. From the obser­va­tions we deduce that the mag­ni­tude of the vec­tor is <1.7×10-42h0 GeV, where h0 is the Hub­ble con­stant in units of 100 km sec-1 Mpc-1.

And…

Many physi­cists would agree that, had it not been for con­ges­tion con­trol, the eval­u­a­tion of web browsers might never have occurred. In fact, few hack­ers world­wide would dis­agree with the essen­tial unification of voice-over-IP and pub­licpri­vate key pair. In order to solve this rid­dle, we confirm that SMPs can be made sto­chas­tic, cacheable, and interposable.

What if I were to tell you that one of these arti­cles is seri­ous research and one was, in fact, ran­domly gen­er­ated tech­nob­a­b­ble? Can you tell which is which?

The first abstract is from a physics arti­cle writ­ten by dis­tin­guished the­o­ret­i­cal physi­cist and blog­ger, Sean Car­roll. This is def­i­nitely seri­ous sci­en­tific research. The sec­ond abstract is ran­domly gen­er­ated. Seri­ously. It fooled some peo­ple well enough to get accepted into the WMSCI in 2005. You can read the full arti­cle here, and even make your own ran­domly gen­er­ated tech­nob­a­b­ble arti­cle here.

At a cer­tain point, the dif­fer­ence between tech­nob­a­b­ble and respectable sci­ence becomes dif­fi­cult to tell apart. Some ridicu­lous claims, in the right con­text, can become tempt­ingly believ­able. On the other side of the coin, even claims from dis­tin­guished sci­en­tists are some­times encoded in sci­en­tific lingo so much that even sci­en­tists in the same field find them dif­fi­cult to understand.

…it’s impos­si­ble to know every­thing, you say? (Well… not you, of course ;) ) It’s futile to try to dis­sect all of the things peo­ple say out there. I’m going to let the sci­en­tists do their thing and I’ll do mine. It’s not like it’s going to affect my life.

I hear you. For a while, I was dis­cour­aged by that thought and there may be truth in it to a cer­tain extent. But, a defeatist approach to sci­en­tific knowl­edge won’t help you. And, the real­ity of the sit­u­a­tion is prob­a­bly closer to this:

Even a small aware­ness of sci­en­tific facts and meth­ods will present you with a huge advan­tage when it comes to siphon­ing out false claims and crack­pots from the jum­ble infor­ma­tion we jug­gle with on a daily basis.

If you think that a knowl­edge of sci­ence is sep­a­rate from “real life”, I would invite you to con­sider this. Exhibit A: Con­ser­va­pe­dia. A wealth of com­pletely false claims. Many of these claims, although rooted in false sci­en­tific claims, per­me­ate into the polit­i­cal arena. As peo­ple who live in a demo­c­ra­tic soci­ety, it mat­ters what we deduce to be fact or fiction.

But what’s to say that wikipedia is any more accu­rate? This is where sci­ence comes in. Not only is sci­ence a col­lec­tion of knowl­edge, it’s also a process. A way to fil­ter out fact from fiction.

Sci­ence is a life skill. Like cook­ing, or coop­er­at­ing with oth­ers, or read­ing a map. It’s not just a pro­fes­sion, it’s not just for nerds, it’s not just a divider (but it can be). Sci­ence is a world view… a use­ful one that cuts through a lot of harm­ful and mis­lead­ing bull. It doesn’t just affect sci­en­tists, it affects our soci­ety, pol­i­tics, our health …

I think I’m going to make this a bit of a series. In future posts we’ll look into what sci­ence really is, con­fir­ma­tion bias, and other neat things.

Categories: Public Knowledge of Science - Tags: , , ,

Improving Your Cognitive Toolkit

Written by Jasper on January 25, 2011 · View Comments
peo­ple find strangers more lik­able when they form their first impres­sions while hold­ing a cup of warm coffee…

I always love talk­ing to new peo­ple about what they do. Not only because it makes for inter­est­ing con­ver­sa­tion, but also because I like to hoard skills. I love the nitty-gritty. I love gen­eral con­cepts. And usu­ally, dif­fer­ent peo­ple with dif­fer­ent back­grounds have some very inter­est­ing bits of knowledge.

This is why I found this link so inter­est­ing (scroll down quite a bit). It is a list of 164 responses to a spe­cific question:

What sci­en­tific con­cept would improve everybody’s cog­ni­tive toolkit?

It’s essen­tially a col­lec­tion of ideas, con­cepts, and “did you know?“s that a large assort­ment of “big thinkers” find inter­est­ing or useful.

For me: gold.

I haven’t fin­ished brows­ing through all of the con­tri­bu­tions, but two have caught my eye so far.

The first is Adam Alter’s tour through the sub­con­scious influ­ences seem­ingly mun­dane things have on our thoughts, feel­ings and opinions.

[…] while we’re focus­ing on the busi­ness of daily life, our brains are pro­cess­ing mul­ti­tudes of infor­ma­tion below the sur­face of con­scious aware­ness. Mean­while, this periph­eral infor­ma­tion sub­tly shapes our thoughts, feel­ings and actions, and crafts some of our most crit­i­cal life out­comes. […]

[…] recent stud­ies have shown that peo­ple find strangers more lik­able when they form their first impres­sions while hold­ing a cup of warm coffee.

[…] peo­ple think more cre­atively when they’re exposed to the Apple Com­put­ers logo, or when they wit­ness the illu­mi­na­tion of an incan­des­cent light bulb […]

The sec­ond is a sim­i­lar self-deception described by Robert Sapol­sky. One that is best dealt with by adopt­ing a sci­en­tific mind­set. This is the idea that peo­ple tend to bias their opin­ions towards anec­do­tal evi­dence (sto­ries) rather than objec­tive data (ex: statistics).

[…] Every good jour­nal­ist knows its power — start an arti­cle with sta­tis­tics about fore­clo­sure rates or fea­ture a fam­ily vic­tim­ized by some bank? No brainer. […]

[…] But anec­do­tal­ism is poten­tially a domain of dis­tor­tion as well. Absorb the lessons of sci­ence and cut sat­u­rated fats from your diet, or cite the uncle of the spouse of a friend who eats noth­ing but pork rinds and is still pump­ing iron at age 110? Depend on one of the foun­da­tions of the 20th century’s exten­sion of life span and vac­ci­nate your child, or obsess over a National Enquirer-esque hor­ror story of one vac­ci­na­tion dis­as­ter and don’t immunize? […]

A good story is a pow­er­ful thing and is prob­a­bly much more intu­itive to peo­ple than sci­en­tific data. But a gen­eral under­stand­ing of sci­ence — what it is, how it’s done and why you can trust it — is also a pow­er­ful thing and it’s a great tool for gain­ing per­spec­tive. The prob­lem is the lat­ter takes time to acquire.

Categories: Academia, Public Knowledge of Science, Random Links

Do you like Quantum Pie with your Morning Coffee?

Written by Jasper on January 18, 2011 · View Comments

New Blog Alert!

Excit­ing news for those of you who like quirky physics blogs. One of my good friends, a Ph.D. in physics and fel­low swing dancer, has started a deli­cious new blog called Quan­tum Pie. Find it at: quantumpie.com.

He’s lined up a series of great posts focus­ing on the magic of quan­tum mechan­ics. He’s hon­ing his video mak­ing skills and is pro­duc­ing some great videos like this one. We’ll be cross-posting even­tu­ally and we have ten­ta­tive plans to do a video series together that uses dance to help explain physics (or at least to catch atten­tion). The series will be called Two to Tan­gle (pun on quan­tum entan­gle­ment). The first of our swing dance video series starts with his Dance your Ph.D sub­mis­sion which he chore­o­graphed, but also star­ring yours truely.

Most of you prob­a­bly don’t know that I’m a swing dancer, so here’s proof. Sit down, relax, have some pie and a cof­fee and enjoy some physi­cists try to explain a PhD with a dance called the Lindy Hop.

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Categories: Fun, Quantum Mechanics, Random Links, Videos - Tags: , , ,

Blog Carnival — The Giant’s Shoulders #31

Written by Jasper on January 16, 2011 · View Comments

Come one, come all to the thirty first edi­tion of The Giant’s Shoul­ders Blog Car­ni­val! A monthly event of epic sci­en­tific pro­por­tions. Step right up, ladies and gen­tle­men. Don’t be shy. Our fea­tured carnies will give you a glimpse into the his­tory of sci­ence by pre­sent­ing clas­sic sci­en­tific lit­er­a­ture and pro­vid­ing help­ful con­text for the casual reader. Come one, come all. A fan­tas­tic spec­ta­cle awaits…

Speak­ing of spec­ta­cles, put on yours, and look through the lens of time with these two optics articles…

First up is Kirsten Walsh, who sheds some light on Newton’s first opti­cal paper in her post: Newton’s ‘Cru­cial Exper­i­ment’ – Early Mod­ern Exper­i­men­tal Phi­los­o­phy from the blog Early Mod­ern Exper­i­men­tal Phi­los­o­phy.

Now, if there’s one blog­ger that knows how to tell a story, it’s Jen­nifer Ouel­lette. She has reimag­ined the story of Ibn al-Haytham, who some con­sider to be the father of mod­ern optics. The Scholar and the Caliph is posted at physicsworld.com.

For some more light read­ing, we have two arti­cles per­tain­ing to the hotspot of light itself; the sun…

Christie Thony has spot­ted the spotty his­tory of the dis­cov­ery of sun spots. If you have a spot of curios­ity, The Ren­nais­sance Math­e­mati­cus is the spot for you, check out the arti­cle: Spot­ting the Spots.

Dr. Sky­Scull writes an illu­mi­nat­ing arti­cle on the dis­cov­ery of the con­nec­tion between radioac­tiv­ity and solar radi­a­tion: The first glim­mer of a nuclear Sun: radium and solar energy (1903) posted at Skulls in the Stars.

If the last two arti­cles have left you with a bit of heat stroke, plunge into the ice-cold sub­ject of glac­ier research with David Bres­san. Here David will tell you the chill­ing story of how Glac­ier research came to be. Guest Blog: The dis­cov­ery of the ruins of ice: The birth of Glac­ier research is posted at Sci­en­tific Amer­i­can.

Cold not your style? You pre­fer some­thing with a bit more energy? Behold, Stephen at Rec­i­p­ro­cal Space has writ­ten an ener­getic post about the man behind the SI unit: Joule in an arti­cle titled: Joule’s Jewel.

Speak­ing of hot things… Alun tells us the secret to a good date… a car­bon date, that is. Check it out: Archae­ol­o­gists prove the secret to a suc­cess­ful date is know­ing what is on the menu posted at Alun­Salt: Ancient Sci­ence and the Sci­ence of Ancient Things.

Expect the unex­pected at a blog car­ni­val, ladies and gen­tle­men… and in sci­ence also…

Michal Meyer takes a step back, and gives us a win­dow into the nature of sci­en­tific dis­cov­ery and the detours it some­times takes. Dis­cov­ery is posted at Peri­odic Tabloid.

Fun for the entire fam­ily! Some­thing for the chil­dren, per­haps? Alice takes a look at early records of sci­en­tific lit­er­a­ture for chil­dren in A bit of Vic­to­ri­ana posted at through the look­ing glass.

William Eamon presents an iconic time in the devel­op­ment of sci­ence in The Iconog­ra­phy of Sci­en­tific Dis­cov­ery in the Renais­sance (Part I) posted at The Offi­cial Web­site of Author William Eamon.

A sep­a­rate but equal intro­duc­tion is deserved by Romeo Vitelli who recounts the aca­d­e­mic life of Mamie Phipps who’s sci­en­tific research trans­formed her into a civil rights icon. The “Sep­a­rate But Equal” War is posted at Prov­i­den­tia.

Stand back, ladies and gen­tle­men! The next topic is not for the faint of heart, for it has been known to send some into the depths of utter madness…

Alexi Baker talks about the darker side of lon­gi­tude in Lon­gi­tude and Lunacy posted at Board of Lon­gi­tude.

Creepy crawlies and things that go bump in the night…

Adrian Thysse’s arti­cle will leave you bug-eyed with an intox­i­cat­ing tale about How to sub­due an ant posted at The Bug Whis­perer.

Brian Switek dives into the Ori­gin of Species and speaks about the, so called, “miss­ing links”. Break­ing our link to the ‘March of Progress’ can be found on the sci­en­tific amer­i­can blog.

What would a car­ni­val be with­out a freak show? David Bres­san digs down into past lit­er­a­ture and unearths some inter­est­ing spec­i­mens in The great­est show on Earth posted at His­tory of geol­ogy.

We laughed, we cried, we were left bug-eyed, and now it’s time to pack up and move on. No place is home for a car­ni­val, but the Giant’s Shoul­ders still needs a place to stay next month. If you would like to host the next blog car­ni­val, leave a com­ment on the Giant’s Shoul­ders site. Thank you guests, orga­niz­ers and carnies.

It’s time for Morn­ing Cof­fee Physics to get back to its reg­u­lar sched­uled blog­ging, start­ing with another cup of coffee.

Categories: Academia, Public Knowledge of Science, Random Links - Tags: , ,

Welcome to the new MCP

Written by Jasper on January 14, 2011 · View Comments

A poet once said:

the whole uni­verse is in a glass of wine.

I think wine can eas­ily be replaced by cof­fee, don’t you?

Morn­ing Cof­fee Physics is my way of try­ing to share what I see some morn­ings when I look at the steam­ing hot cup of cof­fee in front of me. There are things about the world you can’t see with your eyes.

But we can mea­sure them. We can infer them. And we can be sure of them.

These some­times unsee­able things are dis­cov­ered by the process of sci­ence. And  sci­en­tific knowl­edge goes beyond mere tech­no­log­i­cal appli­ca­tion. This knowl­edge lets you see the invis­i­ble things about the world with your mind.

Some­times after dis­cov­er­ing these things you may ask your­self, “why didn’t any­one tell me this before?” I know I did. I some­times became giddy from this new knowl­edge. I wanted to share it with the world. I want you to see what I see when I look at a cup of coffee.

The great physi­cist, Richard Feyn­man, put it very eloquently…

A poet once said, “The whole uni­verse is in a glass of wine.” We will
prob­a­bly never know in what sense he meant that, for poets do not write to
be under­stood. But it is true that if we look at a glass of wine closely
enough we see the entire uni­verse. There are the things of physics: the
twist­ing liq­uid which evap­o­rates depend­ing on the wind and weather, the
reflec­tions in the glass, and our imag­i­na­tion adds the atoms. The glass is
a dis­til­la­tion of the earth’s rocks, and in its com­po­si­tion we see the
secrets of the universe’s age, and the evo­lu­tion of stars. What strange
array of chem­i­cals are in the wine? How did they come to be? There are the
fer­ments, the enzymes, the sub­strates, and the prod­ucts. There in wine is
found the great gen­er­al­iza­tion: all life is fer­men­ta­tion. Nobody can
dis­cover the chem­istry of wine with­out dis­cov­er­ing, as did Louis Pas­teur, the
cause of much dis­ease. How vivid is the claret, press­ing its exis­tence into
the con­scious­ness that watches it! If our small minds, for some
con­ve­nience, divide this glass of wine, this uni­verse, into parts –
physics, biol­ogy, geol­ogy, astron­omy, psy­chol­ogy, and so on — remem­ber that
nature does not know it! So let us put it all back together, not for­get­ting
ulti­mately what it is for. Let it give us one more final plea­sure: drink it
and for­get it all!

- Richard P. Feyn­man, The Feyn­man Lec­tures on Physics, v. 1, p. 3–10

Have fun, explore, you’ll hear from me again very soon.

Categories: Uncategorized - Tags: ,

Krauss and an Overview of Cosmology

Written by Jasper on October 23, 2009 · View Comments

I’ll write a more inter­est­ing post soon, but for now, I present Lawrence Krauss. Here he gives, what I’ve decided to be, the best one hour overview of cos­mol­ogy I’ve ever seen. (via richarddawkins.net)

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What do you all think about his sug­ges­tion that get­ting a uni­verse from noth­ing is natural?

Categories: Cosmology, General Relativity, Philosophy, Videos - Tags: ,

Blog Action Day 2009: Holimictic Lakes and Their Current Issues

Written by Jasper on October 15, 2009 · View Comments

So, in case you don’t know by now, it’s Blog Action Day 2009… ( or at least, it will be for another half hour. I’m a bit behind the times.)

Blog Action Day is an annual event held every Octo­ber 15 that unites the world’s blog­gers in post­ing about the same issue on the same day with the aim of spark­ing dis­cus­sion around an issue of global impor­tance. Blog Action Day 2009 will be one of the largest-ever social change events on the web.

The topic of choice for this year is: Cli­mate Change. Yes, that scary thing.

I puz­zled a while try­ing to think of some­thing physicsy to tell you about cli­mate change. I could tell you that same story about how CO2 in the atmos­phere traps heat caus­ing an increase in aver­age global tem­per­a­tures. I could tell you that this is exactly the rea­son why the planet Venus (with a CO2 rich atmos­phere), although it is fur­ther than the sun from Mer­cury, is hot­ter by a long shot. But I decided against repeat­ing those same old sto­ries, because I fig­ure you’ve prob­a­bly heard them many times and are prob­a­bly get­ting numb. Instead I’m going to go out­side my com­fort zone and plunge into the depths of Lim­nol­ogy and tell you about some cur­rent issues involv­ing cli­mate change in the con­vec­tive cur­rents of holim­ic­tic lakes.

…what’s a holim­ic­tic lake, you ask?

Good ques­tion. I’m not much for fancy names; I pre­fer con­cepts. So, let’s start with the basics. Firstly, you must have heard that hot air rises. But why does it do that? Well, air that is hot­ter than the air sur­round­ing it is also less dense than that air. This means that a vol­ume of hot air weighs less than the same vol­ume of colder air. The colder air will be pulled towards the earth more than hot air and so hot­ter air will be pushed out of the way (upwards) by colder air.

The same is true for water, but only to a cer­tain degree; 4°C to be exact. Water, unlike air, is dens­est at 4°C, so in a tub of 5°C water, a 7°C blob of water will tend to rise to the top. On the other hand, in a tub of 1°C water, a 3°C blob of water will tend to sink because even though it’s warmer it is more dense.

Now, con­sider a lake in the four sea­sons. Dur­ing the Sum­mer the lake water is gen­er­ally above 4°C, so the sun will warm the top lay­ers of the lake and that water (being warmer and less dense) will stay on top and the cooler water will stay deeper down.

When Fall comes around the top part of the lake will be cooled. Even­tu­ally that top part of the lake will cool to the same tem­per­a­ture as the bot­tom part. Winds can cause some tur­bu­lence and the bot­tom parts and top parts of the lake will get mixed up.

When Win­ter comes along the top part of the lake will be colder than the bot­tom part which can hap­pen when the lake is lower than 4°C. The top layer of the lake may freeze over and the lake will again get sep­a­rated into lay­ers of dif­fer­ent tem­per­a­ture — this is called strat­i­fi­ca­tion.

The lake gets mixed up again when Spring comes around. The top of the lake will be heated again and when the lake water at the top reaches 4°C it will sink to the bot­tom and mix up the lake.
StratificationA lake that under­goes this kind of mix­ing is called a holim­ic­tic lake and if it does it twice a year (as described above) it’s called a dim­ic­tic lake.

…what does this have to do with cli­mate change, you ask?

Well, nutri­ents from the lakebed seep into the lower parts of the lake while it’s strat­i­fied (Sum­mer and Win­ter for a dim­ic­tic lake). When the lake mixes, these nutri­ents get mixed into the whole lake. If you are aquatic life which has adapted to depend on those nutri­ents, this mix­ing is a very good thing. With­out it, many species of fish would not be able to sur­vive in that lake.

Cli­mate change threat­ens to put a damper on that mix­ing process for some lakes. As aver­age global tem­per­a­tures increase, unusu­ally warm Win­ters become more likely. What would hap­pen to a dim­ic­tic lake dur­ing one of these unusu­ally warm Win­ters? Well, the lake won’t cool very much dur­ing the Fall, and might even stay above that 4°C mark. This would cause less mix­ing dur­ing the Fall. To make mat­ters worse, because of the warm Win­ter, there will be less mix­ing dur­ing the Spring as well. To make mat­ters worse still, those salts that are dis­solved in the deep parts of the lake make those deep lay­ers more dense. Less mix­ing dur­ing a cer­tain Fall or Spring means more salts stay built up in the deep lay­ers of the lake mak­ing it even more dif­fi­cult to mix the upper and lower lay­ers in future sea­sons. This is a run­away process and it can lead to a nutri­ent defi­cient lake, and very unhappy fish.

The take away mes­sage? Cli­mate change isn’t just about things get­ting warmer and sweat­ing more dur­ing the sum­mer. Cli­mate change is a direct threat to whole ecosys­tems. By tip­ping ecosys­tems out of bal­ance it endan­gers many species of ani­mals, includ­ing the ani­mals caus­ing the tip­ping (us). It’s high time that you start sweat­ing over this sit­u­a­tion. Please think about ways to cut your green­house gas emis­sions. If you need some sug­ges­tions, here are two good ones.

Categories: Thermodynamics - Tags: , ,

Running in the Rain

Written by Jasper on October 6, 2009 · View Comments

So, I’ve never heard this myth before, but a friend asked me about it a while ago. The myth states that run­ning in the rain will make you wet­ter when you arrive at your des­ti­na­tion than if you had walked. This was on my mind recently because it was actu­ally a bonus ques­tion in the physics lab I’m TAing for this year.

Appar­ently Myth­busters showed that run­ning is a bet­ter option for stay­ing dry, but only after they cor­rected for a false result they’d obtained in a pre­vi­ous show. So how could you fig­ure this out with­out going through the has­sle (or fun) of run­ning through some rain yourself?

Well, what we could do is set up an ide­al­ized sit­u­a­tion. Imag­ine there are 5000 drops of rain falling in every cubic meter above you. Let’s say they fall at 5 m/s straight down­wards. To sim­plify things even fur­ther, let’s sup­pose we ignore the struc­ture of our bod­ies and just con­sider a blocky per­son to have a set width, depth and height. Let’s make up a name for this per­son; Sponge Bob Square Pants (Bob for short). So, let’s say Bob is 0.25m thick, 0.5m wide, and 1m tall.

If Bob stands in the rain, all of the rain will hit his head. The num­ber of drops hit­ting him per sec­ond is equal to the den­sity of the rain times his width times his height thick­ness times the veloc­ity of the rain in the down­wards direction;

If he moves (walks or runs) this amount won’t change because the down­ward veloc­ity of the rain won’t change with respect to him. But, on the other hand, if Bob walks or runs in the rain, the rain will have a hor­i­zon­tal veloc­ity with respect to him, so the rain will start to hit him in the front. We can find the num­ber of drops hit­ting his front by the same method.

I’ve just called Bob’s walking/running speed V. I’ll leave it like that and plug in his speed at the end. If Bob needs to run to his house which is 20m away, a total num­ber of drops of rain will hit him in front and back for the trip which we can cal­cu­late. We just need to mul­ti­ply the above results by the time it takes him to get there and then add them together. That’s just the dis­tance to his house divided by his walking/running speed.

But here some­thing funny hap­pens. For the rain hit­ting his front:

Hey! It doesn’t depend on how fast he runs! So it really comes down to the rain hit­ting his head:

The faster he runs, the less time it takes him to get home. So to min­i­mize the num­ber of rain drops hit­ting his head, the faster he needs to run.

… but hey! I’m not the same shape as Sponge Bob, and rain doesn’t always fall straight down, you say?

Well, for those of you who want a more com­plex analy­sis, here’s a link to an online running-in-the-rain-wetness cal­cu­la­tor. Check it out, it’s fun!

Categories: Classical Mechanics - Tags: , , ,

The Physicist’s Toolbox: Thought Experiments

Written by Jasper on September 30, 2009 · View Comments

So maybe you’re a non-physicist, who won­ders how physi­cists think. Maybe you aren’t really sure how those crazy physi­cists come up with all of these equa­tions and the­o­ries seem­ingly from thin air. Maybe you’re get­ting a bit bored of F=ma posts. Well, I’m going to try my best to give you a bit of an inside look at some of the con­cep­tual tools com­monly used by physi­cists in a lit­tle series called: The Physicist’s Toolbox.

This week: Thought Experiments

When some­one men­tions the term “thought exper­i­ment”, the first per­son that prob­a­bly comes to mind is Ein­stein and his day­dream about try­ing to chase a beam of light — an image of which even non-physicists will be famil­iar. This is because thought exper­i­ments tend to be very mem­o­rable and acces­si­ble because they usu­ally involve sim­ple math or no math at all. Despite their math­e­mat­i­cal sim­plic­ity, how­ever, they still man­age to shed light on puz­zling aspects of nature.

Physics is an empir­i­cal sci­ence which means that you can do all the think­ing and the­o­ris­ing you want, but at the end of the day, if it doesn’t match the real world exper­i­men­tal results, it’s wrong. This fact might make the term “thought exper­i­ment” seem like a bit of an oxy­moron. It’s true, a thought exper­i­ment won’t serve to prove any­thing in the same way a real exper­i­ment would, but it still has tremen­dous value. Thought exper­i­ments serve to col­lect one’s thoughts and attempt to make cer­tain con­cepts in physics more intu­itive. Occa­sion­ally they can shed new light on how the world works.

Here’s a really neat exam­ple. Remem­ber Galileo? Remem­ber the story of him drop­ping a can­non ball and a mus­ket ball from the lean­ing tower to show that they fell at the same rate? Well, it’s unlikely that Galileo actu­ally did this. It’s more likely that this was a well crafted thought exper­i­ment. Imag­ine start­ing with the assump­tion that heav­ier objects fall faster. What hap­pens now if you attach a lighter object to a heavy object? The light object would want to fall slower than the heavy one, and would almost act like a para­chute for the heavy one. But if you con­sider the com­pound object, it is heav­ier than both objects alone. So shouldn’t it fall faster? This thought exper­i­ment demon­strates that the assump­tion that heav­ier objects fall faster leads to a con­tra­dic­tion. An obvi­ous res­o­lu­tion to the con­tra­dic­tion is to declare that all objects, regard­less of their weight, fall at the same rate. If one did this exper­i­ment in real life would prob­a­bly not see the objects fall at the same rate because of air fric­tion. The power of the thought exper­i­ment is in its sim­plic­ity. It serves to demon­strate how nature should behave under cer­tain assump­tions and sig­nals that some­thing more is needed to be under­stood if nature doesn’t behave like this.

A hypothetical supercannon shooting cannon balls at greater and greater force demonstrates how orbit is possible.Newton’s can­non ball is another great exam­ple of an enlight­en­ing thought exper­i­ment. Really, just the sim­ple pic­ture of a few tra­jec­to­ries of a can­non ball being shot with greater and greater force demon­strates how things like the moon can orbit the earth. Good thought exper­i­ments like this tend to give the thinker an “aha!” moment; that moment of realization.

I’ve blogged about a few thought exper­i­ments here on Morn­ing Cof­fee Physics. Some fun ones include Einstein’s ele­va­tor exper­i­ment, and the Rope and Wood rid­dle.

Traingular Block Chain Thought ExperimentThere’s one more thought exper­i­ment I really like. Imag­ine plac­ing a chain (con­stant mass per unit length) on an obtuse tri­an­gu­lar block. On one side, there is less chain, but a steeper slope. On the other side, there is more of the chain, but the slope is not too steep. Which way will the chain slide?

Sure, you could work out the forces and angles and all that jazz. But there is a very sim­ple way to see the answer. Think about it for a few seconds.

…

Done? Okay.

Triangular Block Chain Thought ExperimentJust con­nect another chain below and let it hang off of the ends of the pre­vi­ous chain, like so. Have you felt that “aha!” moment yet?

The hang­ing chain is sym­met­ric so it should pull on each side of the top chain equally, which can­cels its effect out. But if the top chain slid to one side or the other, for every link that fell off the block, another would replace it on the other side (com­ing from the hang­ing chain). Mean­ing the two (now linked) chains would spon­ta­neously spin around the block! This is a ridicu­lous notion and a vio­la­tion of the laws of con­ser­va­tion of energy. There­fore, the chain in the pre­vi­ous pic­ture must remain at rest. No math necessary!

Any­one else have a favorite thought experiment?

___

A great ref­er­ence: Brown, J. R., “Thought Exper­i­ments”.

Categories: Physicist's Toolbox - Tags: , , ,

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