The Manx Missile Blasts Off Again!

Mark Cavendish won his second stage of this year's Tour de France.  Chris Froome maintains his hold on the yellow jersey.  As I expected, we were once again too slow.  Below is Cavendish's time compared to our prediction.

• Stage 13:  3h 40' 08" (actual), 4h 01' 57" (prediction), 21' 49" slow (9.91% error)

Despite 15 kph (9.3 mph) crosswinds with headwind components, Cavendish was able to achieve the average speed you see below.

• Stage 13:  13.10 m/s (47.15 kph or 29.30 mph)

Check out my post from yesterday.  Granted, only Stage 15 from last year's race was shorter than today's 173-km (107-mi) stage.  Still, no average speed from last year's flat stages comes close to what was seen today.  Last year's Stage 15 was 14.5 km (9.01 mi) shorter than today's stage, yet the winner's average speed in that stage was 43.18 kph (26.83 mph).  Even my super-low estimate of 3h 45' 00" at the end of yesterday's post would have been five minutes too slow.

All 181 cyclists beat our prediction today.  The last rider's time was 3h 53' 44", which gives an average speed of 44.41 kph (27.59 mph).  That would have been the third fastest average speed for last year's flat stages.  Put another way, today's last-place finisher had an average speed that would have won six of last year's flat stages.

To say we are flummoxed by the speeds we've seen in recent stages would be an understatement!  For those of you in France who are watching the race live, be sure to get out earlier than what the Tour de France website suggests on its time schedule.  Today's time schedule had 46.0 kph (28.6 mph) for its maximum estimated average speed.

Tomorrow's Stage 14 is of the medium-mountain variety.  The 191-km (119-mi) stage begins in the commune of Saint-Pourçain-sur-Sioule and ends to the southeast in the city of Lyon.  Along the way, cyclists will meet five category-4 climbs and two category-3 climbs.  Our prediction is given below.

• Stage 14:  4h 35' 15" (prediction)

If this were 2012, I would be quite confident with the above prediction.  Given how this year is going, I won't be surprised to see something close to 4h 20' 00".  I am not trying to play two predictions.  We are sticking with what is written above because we want to be fair to the model we created when this race started.  It is clear, however, that the jump in athletic performance and technology from last year to his year is greater than we anticipated.

Kittel wins his third stage!

German Marcel Kittel won his third stage of this year's Tour de France (recall he won Stages 1 and 10) by just barely beating out Mark Cavendish at the finish line.  Chris Froome still holds the yellow jersey.  Below is how Kittel's time compared to our prediction.

• Stage 12:  4h 49' 49" (actual), 5h 02' 54" (prediction), 13' 05" slow (4.51% error)

There is a clear theme with our modeling this year.  We simply do not have quite enough power output to match the winning times we are seeing.  All 182 cyclists beat our prediction today, and that was despite 20 kph (12 mph) crosswinds with predominately headwind components.  Check out the average speed below for Kittel's win.

• Stage 12:  12.54 m/s (45.13 kph or 28.04 mph)

You see the average speed above for today's 218-km (135-mi) flat stage.  Below is a table of last year's (2012 Tour de France) flat stages and the average speeds for the winners of those stages.

Stage	Length (km)	vave (kph)
1	198.0	39.82
2	207.5	41.92
4	214.5	40.40
5	196.5	41.88
6	207.5	44.95
13	217.0	43.69
15	158.5	43.18
18	222.5	45.38

I left out the ceremonial last stage.  Only Mark Cavendish's phenomenal ride in last year's Stage 18, a stage on which we were 7.10% slow, has an average speed in excess of today's average speed.  What is all the more remarkable about Cavendish's win in last year's Stage 18 is that that stage was 4.5 km (2.8 mi) longer than today's Stage 12.  Whether last year's flat stages were longer or shorter than today's stage, only last year's Stage 18 exceeds today's speed.

It should be obvious from the above table why we have been surprised by this year's race.  The technology that goes into the bikes and apparel, the teams' strategies, and the athletes' performances must have improved considerably since last year's race.  Every Tour de France is different and every stage is different.  Still, we are impressed with this year's speeds.

Tomorrow's Stage 13 is also flat.  It picks up where today's left off, in Tours, and sends riders 173 km (107 mi) southeast to the commune of Saint-Amand-Montrond, which is located right in the center of France.  Below is our prediction.

• Stage 13:  4h 01' 57" (prediction)

Will riders save a little for the daunting mountain stages in the Alps?  Or will they go all out to secure the best time position before the climbing begins?  There is a short category-4 climb in tomorrow's stage, but the route is mostly flat.  Given how fast cyclists have been this year, I won't be surprised to see a winning time closer to 3h 45' 00", but I'll stick with the prediction above.

Tony Martin Blows Away Time Trial!

We continue to be stunned by speeds at this year's Tour de France.  German Tony Martin won today's Stage 11, an individual time trial.  He was 12" faster than second-place finisher Chris Froome of Great Britain (Froome retains the yellow jersey) and 01' 01" faster than third-place finisher Thomas De Gendt of Belgium.  That is quite a gap between first place and third place!  Below is Martin's winning time compared to our prediction.

• Stage 11:  36' 29" (actual), 39' 23" (prediction), 02' 54" slow (7.95% error)

Below is Martin's average speed.

• Stage 11:  15.08 m/s (54.27 kph or 33.72 mph)

Let's try to put that average speed into perspective.  Today's time trial took place over 33.0 km (20.5 mi).  Last year's Stage 9 was an individual time trial over 41.5 km (25.8 mi).  Bradley Wiggins won that stage with an average speed of 13.46 m/s (48.44 kph or 30.10 mph).  When today's winner, Tony Martin, won Stage 20 in 2011, an individual time trial over 42.5 km (26.4 mi), his average speed was 12.75 m/s (45.90 kph or 28.52 mph).  Granted, those two time trials were over distances more than 25% longer than today's time trial, so we fully expect today's average speed to be greater than the two aforementioned time trials.

Well, what about Stage 4 in 2008, an individual time trial over 29.5 km (18.3 mi), about 89% the length of today's stage?  Stefan Schumacher won that stage with an average speed of 13.76 m/s (49.53 kph or 30.78 mph).  That stage was run in the French commune of Cholet, which sits at an elevation not much different from today's stage.  Winds with tailwind components switched to headwind components as today's action moved along.  Even with a tailwind, we are immensely impressed with Martin's ride!

Our predicted time was beaten by 37 cyclists; 145 came in slower than our prediction.  We thus predicted a time that about 20% of the cyclists beat.  Martin not only beat our prediction, he crushed it.  He and Froome also crushed the other 180 riders today.

Tomorrow's Stage 12 is about as flat as flat can be.  Starting in the northwest French commune of Fougères, the 218-km (135-mi) stage takes riders southeast to the city of Tours.  Below is our prediction.

• Stage 12:  5h 02' 54" (prediction)

The way stages have turned out so far, we certainly won't be surprised to see a cyclist cross the finish line in under five hours!

Headwinds Dominate Stage 10!

German Marcel Kittel just edged fellow countryman André Greipel at the finish line of a very windy Stage 10.  Below is a comparison between Kittel's time and our prediction.

• Stage 10:  4h 53' 25" (actual), 4h 34' 42" (prediction), 18' 43" fast (-6.38% error)

Had we not been following today's action and seen only the winning time, we would have been quite disappointed.  What we noticed while following the race is some wild wind.  There were crosswinds of 30 kph (19 mph) with headwind components dominating the entire stage.  We simply knew our prediction was going to be too fast if cyclists had to battle headwinds all day!

Below is a table showing what a small horizontal headwind can do to our prediction for Stage 10.

vhead (kph)	Prediction
1	4h 41' 17"
2	4h 48' 13"
3	4h 55' 30"
4	5h 03' 11"
5	5h 11' 16"

Note that what is assumed in making the above table is that riders feel a constant headwind of a given magnitude for the entire race, which is a gross oversimplification of reality.  What we noticed today were gusts of winds that reached 30 kph with directions mostly perpendicular to the riders' motion (i.e. crosswinds) with headwind components.  That means that cyclists felt only a small piece of the wind as a headwind on average.  There were times when the headwind was strong, and there were a few times late in the stage when the wind actually gave a tailwind component.  What the above table shows us is that the effect of today's wind was equivalent to riders feeling a constant headwind of about 3 kph.

Below is Kittel's average speed.

• Stage 10:  11.19 m/s (40.28 kph or 25.03 mph)

Stage 11 is an individual time trial.  Beginning in the northwest French commune of Avranches, the 33.0-km (20.5-mi) time trail ends on the tidal island of Mont Saint-Michel in the English Channel.  Riders should go all out with a flat stage to follow on the next day.  Below is our prediction.

• Stage 11:  39' 23" (prediction)

Look for top speeds tomorrow!

Stage 10 Prediction

The Tour de France is at rest today.  Tomorrow's action picks up with a flat Stage 10, which begins in the western French commune of Saint-Gildad-des-Bois and then heads due north for 197 km (122 mi) to the city of Saint-Malo on the English Channel.  There is one category-4 climb nearly three quarters of the way in, but it's a short climb and certainly nothing like what riders experienced in the Pyrenees.  Below is our prediction.

• Stage 10:  4h 34' 42" (prediction)

Six more stages greet cyclists before the next rest day.  Will cyclists use today's rest to gear up for tomorrow?  Or will they hold back a little for the next day's individual time trial?  We shall see!

Martin Takes a Grueling Stage 9!

Irishman Dan Martin made a late move to win today's five-climb mountain stage.  Below is Martin's time and a comparison with our prediction.

• Stage 9:  4h 43' 03" (actual), 4h 56' 40" (prediction), 13' 37" slow (4.81% error)

Though we did better than yesterday's bad prediction, and we are glad to be back under 5% off, we will have to examine our model's power outputs for the mountains stages.  The power outputs we use are based on physiological research and power outputs needed in previous races.  The athletes are simply doing a bit better than we thought.  We always hope for small errors, but the past two stages have given us an opportunity to learn something.  That's what makes doing science fun!

Below is Martin's average speed for his big win today.

• Stage 9:  9.922 m/s (35.72 kph or 22.19 mph)

That is a phenomenal average speed for such a grueling mountain stage!  A total of 57 riders beat our time with the bottom 16 of that group coming in only about two minutes under our time.  There were 125 riders who came in over our time, which means our prediction was beaten by about 31% of the riders.

Chris Froome retains the yellow jersey.  He now has a 01' 25" lead over second-place rider Alejandro Valverde, the Green Bullet from Spain.  Cyclists will have to fly due north for the next stage, which takes place in northwest France.  A day off tomorrow will get them ready for a flat stage on Tuesday.  Check back tomorrow to find out what we will predict for Stage 10.

Great stage for Froome ... bad stage for us ...

Chris Froome of the Sky Procycling Team, one of the world's best climbers in the mountains, won today's Stage 8.  He also took hold of the yellow jersey; he holds a 51" lead over Sky teammate Richie Porte of Australia.  Below is Froome's time and the comparison with our prediction.

• Stage 8:  5h 03' 18" (actual), 5h 30' 55" (prediction), 27' 37" slow (9.11% error)

When I began modeling the Tour de France in 2003 with Ben Hannas, we were happy that the majority of our predictions came in under 10%.  That's not true today.  Our prediction for this stage was just BAD -- no other way around it.  We'll have to look carefully at this stage and determine where the flaw in our model for this stage is lurking.  We note that 94 cyclists, which represent half the field, finished in a time greater than our prediction.  What our prediction pegged was the average Tour de France cyclist, not the day's best.

Froome's average speed is given below.

• Stage 8:  10.72 m/s (38.58 kph or 23.97 mph)

That's a great average considering the two big climbs cyclists traversed today.  Well done, Froomey!

Tomorrow's Stage 9 is a full-fledged mountain stage in the Pyrenees.  The commune of Saint-Girons is the starting point of the 168.5-km (104.7-mi) stage, which ends to the west in Bagnères-de-Bigorre.  Riders contend with a category-2 climb early on, and then face four category-1 climbs before the 30-km (19-mi) descent to the finish line.  A stage like this requires incredible athletes and well-planned strategy.  Below is our prediction.

• Stage 9:  4h 56' 40" (prediction)

We've been just a bit slow on each stage, until today when were much too slow.  We love our predictions for the first seven stages; we hope to take a mulligan on today.  Monday, 8 July is a rest day.  After tomorrow's stage, riders will need a day off!

The Terminator Takes Stage 7!

The Terminator, as 23-year-old Peter Sagan from Slovakia is known, won today's Stage 7 after a great downhill sprint to the finish.  Below is how our prediction fared against today's result.

• Stage 7:  4h 54' 12" (actual) 5h 00' 15" (prediction), 06' 03" slow (2.06% error)

We are thrilled to be just 2% off today's stage-winning time.  We are especially happy with our modeling given that cyclists enjoyed a tailwind of roughly 15 kph (9.3 mph) during most of their final 30-km (19-mi) descent toward the finish line.  Without that tailwind, we would have been much closer!  As I've noted all along, though easy to include if known, we can't predict local weather effects.

Below is Sagan's average speed for today.

• Stage 7:  11.64 m/s (41.91 kph or 26.04 mph)

South Africa's Daryl Impey retains the yellow jersey with a three-second lead over Edvaold Boasson Hagen of Norway.

The Tour de France hits the Pyrenees in tomorrow's Stage 8.  Beginning in the southern French commune of Castres, the 195-km (121-mi) stage has a category-4 climb early on and heads south from there.  The end of the stage features a brutal category-1 climb to the resort Ax 3 Domaines, which is at an elevation of 1375 m (4511 ft).  Before thinking that the end climb is what will challenge riders most, consider the climb to the 2001-m (6565-ft) peak of Col de Pailhères, which riders reach 29 km (18 mi) before the resort finish.  The climb to that peak is classified HC or hors catégorie, which means "beyond categorization."  You wouldn't know Stage 8 is a mountain stage two-thirds of the way in.  After that, the Pyrenees Mountains take over!  Below is our prediction.

• Stage 8:  5h 30' 55" (prediction)

If you can only watch part of tomorrow's stage, tune in to the final third.  Two monster climbs sandwiched between a sensational downhill will make for exciting viewing.

Gorilla and a Windy Stage 6

As I wrote yesterday was possible, weather played a role in today's stage win for German André Greipel, aka Gorilla.  Wind speeds were in the 30-50 kph (19-31 mph) range, often hitting cyclists from the side.  There were also portions of the race where headwinds were prevalent; other portions had tailwinds.  It had to be a lot of fun to be on a bicycle in southern France today!

Below is how our prediction fared against Greipel's winning time.

• Stage 6:  3h 59' 02" (actual), 4h 05' 47" (prediction), 06' 45" slow (2.82% error)

We'll definitely take an error under 3%!  I am happy to see riders sneak in under four hours.  With strong, changing winds and a crash not too far from the finish, the best of the best still finished a grueling stage in a few ticks less than four hours.  Below is Greipel's average speed.

• Stage 6:  12.31 m/s (44.30 kph or 27.53 mph)

History was made today as Daryl Impey now leads the overall time classification.  Impey took the yellow jersey from fellow Orica-GreenEDGE teammate Simon Gerrans, who now sits third in the standings.  Impey is not only the first South African to lead the Tour de France, he will be the first African to don the famed yellow jersey.

Tomorrow's Stage 7 is a 205.5-km (127.7-mi) medium-mountain stage that commences in Montepellier and finishes in the commune of Albi.  Riders continue west on their approach to the Pyrenees.  The stage features a category-4 climb near the end, a couple of category-3 climbs, and a category-2 climb near the halfway point.  Below is our prediction.

• Stage 7:  5h 00' 15" (prediction)

Save a little energy for Stage 8 when the race hits some monster climbs in the Pyrenees!

The Manx Missile and 11 Measly Seconds

Mark Cavendish, aka the Manx Missile, had a great sprint to the finish line in today's flat stage.  I yelped a bit at the finish when I saw today's winning time.  Below is the comparison between Cavendish's winning time and our prediction.

• Stage 5:  5h 31' 51" (actual), 5h 32' 02" (prediction), 0' 11" slow (0.06% error)

I am very pleased with our prediction!  We slightly underestimated power output and technological advances in yesterday's team time trial.  Today, we had a great feeling for how the long, flat stage would go.  Below is Cavendish's average speed.

• Stage 5:  11.48 m/s (41.31 kph or 25.67 mph)

That is an impressive average for such a long time on a bicycle.  Those Tour de France athletes are something special!

Tomorrow's Stage 6 is another flat stage.  It starts in Aix-en-Provence and takes riders due west nearly along the southern coast of France to Montpellier.  Shorter than today's stage, Stage 6 is 176.5 km (109.7 mi) long with one category-4 climb just over one third of the way in. Our prediction is given below.

• Stage 6:  4h 05' 47" (prediction)

Will weather play a role as riders are going to be close to the coast?  Will riders be thinking ahead to Stage 7 and its four category-ranked climbs? Or will someone have the best day of his life and come in under four hours?  Team Orica-GreenEDGE should be safe after tomorrow.  Simon Gerrans maintains the yellow jersey today, and will probably have it after tomorrow's stage.

Top speeds in Nice today!

The Australian Orica-GreenEDGE team dominated today's team time trial.  In time trials, cyclists wear special helmets and use modified bikes so as to reduce drag.  They further reduce air resistance in team time trials by employing the strategy of drafting, which is also used by race cars.  Tucking oneself right behind another cyclist reduces air drag.  The team time trials are fun to watch because of the tight linear formations used by the various teams.  It really is a coordinated thing of beauty as the cyclists take turns leading their teammates.

Below is how our prediction came out against today's result.

• Stage 4:  25' 56" (actual), 27' 33" (prediction), 01' 37" slow (6.23% error)

After nailing last year's two individual time trials to better than 1%, we had high hopes for this year's time trials.  The athletes once again surprised us!  We now know that our drag coefficient reduction and power increase were not quite enough.  We will never cease being amazed by the quality of the athletes and the technological advancements in equipment made by scientists and engineers.  Well done!

Team Orica-GreenEDGE's average speed is given below.

• Stage 4:  16.07 m/s (57.84 kph or 35.94 mph)

Wow, that's fast!  I've certainly never been on a bike moving anywhere close to that speed.  Again, kudos to the athletes and their teams for a phenomenal stage.

The Orica-GreenEDGE team put itself in great position today with team member Simon Gerrans now in possession of the yellow jersey.  Two Orica-GreenEDGE members are right behind Gerrans.  With sprinters looking to dominate the next two flat stages, Orica-GreenEDGE and its team of sprinters should keep the yellow jersey for another couple of stages.

Tomorrow's Stage 5 starts cyclists just southwest of Nice in the commune of Cagnes-sur-Mer.  Though designated a flat stage, riders will open the stage with a category-3 climb, and then meet three category-4 climbs throughout the rest of the 228.5-km (142.0-mi) stage.  The stage ends in the southern French city of Marseille.  Below is our prediction.

• Stage 5:  5h 32' 02" (prediction)

Look for an exciting downhill sprint to finish the stage.

Gerrans just edges Sagan!

A thrilling finish to today's Tour de France action saw Australia's Simon Gerrans sprint across the finish line a split second before Peter Sagan of Slovakia.  The decision to begin the 100th Tour de France with three stages in Corsica was phenomenal!  The first three stages were thrilling, to say the least.  Below is how our prediction fared against today's result.

• Stage 3:  3h 41' 24" (actual), 3h 44' 26" (prediction), 03' 02" slow (1.37% error)

We are pleased with our prediction!  As I wrote yesterday, "I won't be surprised if tomorrow's winner edges our time once again."  The athletes are impressing us this year!  Seeing the Tour de France unfold gives us the opportunity to appreciate how months of training and new technologies employed in equipment pay off.

Below is Gerrans's average speed for today.

• Stage 3:  10.95 m/s (39.43 kph or 24.50 mph)

Despite his 19th place finish today, Jan Bakelants retains the coveted yellow jersey with a one-second lead over Julien Simon of France.  Gerrans's big win today gets him classified third overall.

The Tour de France leaves beautiful Corsica and heads to France tomorrow.  Stage 4 is a team time trial in the southeastern city of Nice.  At just 25 km (15.5 mi) in length, expect riders to go all out!  The trip through Nice is almost entirely flat.  Below is our prediction.

• Stage 4:  0h 27' 33" (prediction)

Don't turn away from tomorrow's action -- it's going to be FAST!

Bakelants takes Stage 2!

Jan Bakelants of Belgium won today's Stage 2.  He also slips into the overall leader spot with a mere one-second lead over Great Britain's David Millar.  We were a bit slow with our prediction today.  Below is a comparison of the winning time with our prediction.

• Stage 2:  3h 43' 11" (actual), 3h 51' 28" (prediction), 08' 17" slow (3.71% error)

Given that cyclists were still crossing the finish line 17 minutes after Bakelants, our prediction hit the average cyclist today instead of today's elite cyclist.  An error under 4% isn't bad, but after such a successful first stage, anything worse looks bad by comparison.

Bakelants's average speed is given below.

• Stage 2:  11.65 m/s (41.94 kph or 20.06 mph)

Tomorrow's Stage 3 is another of the medium-mountain variety.  Picking up where Stage 2 left off in Ajaccio, cyclists have 145.5 km (90.4) to bike before arriving in the commune of Calvi.  After seeing the east side of Corsica in the first stage, the middle of the island today, riders will travel north along the island's western edge tomorrow.  A category-4 climb greats riders at the start, followed by two category-3 climbs just before the halfway point.  A category-2 climb awaits the athletes near the stage's end, the other side of which should make for an exciting sprint to the finish line.  Below is our prediction.

• Stage 3:  3h 44' 26" (prediction)

The first two stage winners have been a bit faster than we thought.  I won't be surprised if tomorrow's winner edges our time once again.  Enjoy the last day of the race on Corsica!

Less than 1% off Stage 1!

German Marcel Kittel took this year's first Tour de France stage win, which also happens to be Kittel's first ever stage win in cycling's greatest race.  A big crash marred the end of today's competition, knocking out favorites like the Manx Missle, Mark Cavendish.  A bit of serendipity helped Kittel escape the crash.  Below is the comparison between Kittel's winning time and our prediction.

• Stage 1:  4h 56' 52" (actual), 4h 59' 17" (prediction), 02' 25" slow (0.81% error)

I think we'll take that start for this year's race!  We were glad to see the winner come in under five hours.  About halfway through today's stage, my student, Brian Ramsey, contacted me and informed me of headwinds reaching 10 kph (6.2 mph).  I told him that we might be fast with our prediction if headwinds continued to dominate the action.  Instead, racers found themselves aided by tailwinds at the end of the race.  We were lucky to have the weather average out a bit for us.  We aren't good enough weather forecasters to include wind, rain, fog, and/or massive fluctuations in temperature and humidity in our model.  The inclusion of crashes is obviously something we can't do either.

Kittel's average speed is given below.

• Stage 1:  11.96 m/s (43.05 kph or 26.75 mph)

Tomorrow's Stage 2 picks up in Bastia and finishes 156 km (96.9 mi) away in the French commune of Ajaccio.  The medium-mountain stage takes riders southwest through the heart of Corsica.  Along the way are two category-3 climbs, followed by a category-2 climb to get to the 1163-m (3816-ft) peak at Col de Vizzavona.  A great downhill sprint on the other side of the mountain gets riders thinking about one final category-3 climb before a relatively flat finish.  Below is our prediction.

• Stage 2:  3h 51' 28" (prediction)

I hope the three big climbs don't tire riders out too much.  The best of the best should finish in under four hours.  A great downhill awaits the cyclists and we fans tomorrow!

Tour de France Time!

The 100th Tour de France is set to begin tomorrow (29 June) on the island nation of Corsica.  Instead of a short prologue stage, riders will encounter a full 213-km (132-mi) flat stage.  Beginning in the commune of Porto-Vecchio, Stage 1 takes cyclists north along the eastern edge of Corsica toward the finish at the commune of Bastia.  Testing the competitors early will be a category-4 climb as they reach the 45.5-km (28.3-mi) point.  Most of the rest of the stage is quite flat.

As I've done the past two years, I will post predictions for each stage's winning time.  Working with me again this year is Lynchburg College physics major Brian Ramsey.  Our goal, as always, is to predict the winning time, not the person who will win the stage.  The basic model we employ is described in Chapter 4 of my book (click here or on the image of my book's cover on the right side of the blog).  We have modified our model this year and we are anxious to see how well it does.  If it works well, we'll obviously be thrilled.  If not, we'll have to tweak a little here and there and, hopefully, learn a bit more about how the world works.  That's what's great about doing science -- learning something!

So, without further ado, here is our prediction for stage 1:

• Stage 1:  4h 59' 17" (prediction)

This prediction is a bit of a challenge to the athletes:  finish the first stage in less than five hours!  Will they hold back a little, knowing they've got 20 more stages?  Or will some bold rider set a fast pace?

Force Needed for Child Toss

Since posting a piece on tossing a child in a swimming pool, I've gotten several flattering comments and e-mails from family, friends, and colleagues.  The consensus seems to be that though child tossing will never appear in the Summer Olympics, it is highly recommended as something fun to do in a swimming pool.  A few people asked that I compute the force I needed to propel my younger daughter into the air.  That is the subject of this post.

The animated GIF below shows the portion of my vacation movie that involves my daughter being pushed upward (click on the image for a larger view).

The red data points show the position of my daughter's left shoulder, which is the same reference I used in my previous post.  My daughter's weight is 37 lbs (165 N), which corresponds to a mass of 1.15 slugs (16.8 kg).  What a terrible name for a mass unit!  Using Newton's second law, I came up with the force plot you see below (click on the image for a larger view).

The force I applied to propel my daughter is on the vertical axis; time is on the horizontal.  During the nearly half second it took to launch my daughter, my maximum force reached about 70 lbs (311 N).  During the strongest part of my push, I shoved my daughter with a force roughly twice her weight.

One must be cautious with force calculations that originate with position/time data, as mine do.  Acceleration requires two time derivatives of position, and those derivatives must be calculated numerically.  That is why you see a large force for the first datum and a nonzero force for the last datum.  If I wasn't trying to propel my daughter, my force should be her weight.  But the graph's first datum shows a force about twice her weight.  The reason is that the first couple of times are left off because they are needed to compute the first force datum shown in the graph.   The force calculations for the data away from the edges in the above plot should be good.

Okay, that's enough about child tossing from me.  With the 100th Tour de France starting on Saturday, I've got plenty of other physics goodies to keep me busy!

The Art of Child Tossing

I stayed up late last night watching the San Antonio Spurs blow a golden opportunity to win the NBA title over the Miami Heat.  Instead of analyzing anything from that game, the most constructive of which would concern coaching, I decided to analyze something much more fun -- child tossing.  No, I'm not about to describe some pernicious activity involving a defenseless and unwilling child.  The child tossing to which I refer is the stupendously fun activity of being asked by one's child to throw him or her into a swimming pool, and then gleefully obliging that child.  Writing this post will keep me from thinking about tonight's College World Series baseball game between my Hoosiers and the Beavers of Oregon State.

During my family's recent Florida vacation, we spent several hours in a swimming pool so as to avoid the oppressive heat.  My younger daughter kept asking me to throw her into the pool, and I couldn't turn her down.  She loved getting into a cannonball position and having me throw her as far as I could while I was standing in the pool.  Using a low-price digital camera's movie mode with a paltry 24 frames per second, my wife filmed me throwing my younger daughter into the water.  My older daughter meant to serve as a height reference, but was too far from the plane of my younger daughter's trajectory to be a good length standard (I ended up using my own head!).  The animated GIF below shows my child toss (click on the image for a larger view).

You can see a red trail connecting the data points (I marked my daughter's left shoulder).  I marked the movie frames using a wonderful free video analysis program from Open Source Physics called Tracker (click here to get it).

So, could I compete in a professional child tosser event?  Well, I launched my daughter at just over 5 mph (8 km/hr) at an angle of about 63 degrees from the horizontal.  After a flight time of nearly 0.6 s, my daughter hit the water at a speed of about 11 mph (18 km/hr).  She landed a horizontal distance of roughly 3.2 ft (0.98 m) from the point where I let go of her.  Her entry into the water was about 75 degrees from the horizontal.

Many more goodies may be gleaned from video analysis.  I could look at the small effect air resistance had on the trajectory.  I could examine the force I needed to exert to get my daughter into flight.  I could look at the splash dynamics.  Lots of wonderful physics toys with which to play!

Professional child tossing probably won't catch on, but it's a lot of fun in a swimming pool with kids who love to fly through the air!  That one may use a base-model digital camera and free software to turn fun in the pool into a first-year physics problem makes it all the more delightful.

A Closer Look at LeBron's Game 2 Block

The Miami Heat now find themselves in a one-game hole to the San Antonio Spurs in the NBA Finals.  Between the second and third games of the series, I examined LeBron James' monster Game 2 block of Tiago Splitter's dunk attempt with 8:21 left in the game.  The Heat had a 19-point lead at the time, so the block wasn't the difference maker.  It did, however, emphatically let the Spurs know that Game 2 would not be theirs.

Check out the photo below (click on the image for a larger view).

I analyzed the block frame by frame of the slow-motion video.  The red diamonds show the path of the ball during the block.  The ball starts on the lower right side of the red trail and traverses the red trail until the image you see.  One can really see the ball coming in, and then getting rejected!

I estimate that James took off from the court at about 9 mph (14.5 km/hr or 4 m/s) and reached the top of his leap in around 0.4 s.  The main part of the block too place in roughly 0.1 s, during which James needed an average force of nearly 14 pounds (62 N) to reject the ball.  Instantaneous forces were larger, but 14 pounds is roughly the average force James used to send Splitter's dunk attempt back.

Put simply, LeBron James had to leap to a height that put his hand above the rim, and at 0.4 s to get there, his timing had to be perfect.  Once there, James had to push laterally with a force comparable to what one has to exert to hold a bowling ball.  Not bad!

Shakehand beats penhold -- again!

Just like he did in London last summer (click here for my blog post on that match), China's Zhang Jike defeated fellow countryman Wang Hao in the finals of a major table tennis tournament, this time the 2013 World Table Tennis Championships in Paris.  What fascinates me about a match featuring Zhang and Wang is the contrast in playing styles.  Zhang uses a shakehand grip whereas Wang employs a penhold grip.  The shankehand grip is so named because one appears to be shaking hands with one's racket   The penhold grip is also well named because one appears to hold the handle of one's racket as one might hold a pen.  In such a grip, the racket appears "upside down" to many novice players.

What astounds me about Wang's play is that he is able to use the backside of his racket for his backhand.  As a less-than-stellar penhold player myself, I use a racket with no playing surface on the backside, which is fairly standard for a penhold player.  My backhand is by far weaker than my forehand, which is why Wang's style intrigues me.  His wrist appears rubbery to me as I watch him execute hard backhand smashes.  I can only dream of such backhand skill!

Despite Wang's backhand prowess, he had to settle for second behind Zhang, who has a backhand shot as good anybody playing today.  Zhang makes use of a slightly less spongy surface on his racket so as to ensure more translational kinetic energy transfer to the ball at the expense of a little rotational kinetic energy, meaning he loves to play fast.

Table tennis at the highest levels involves smashes hard enough to lead to air drag greater than five times the weight of the ball and a Magnus force, which is due to the ball's spin, greater than twice the ball's weight.  That's why you will see players sometimes playing well back of the table's edge -- the ball moves fast with lots of spin, meaning it curves quite a bit more than with gravity acting alone.

The women's final of the World Championships saw Li Xiaoxia, the gold medalist in London, defeat Liu Shiwen, both also from China.  Li and Liu each use a shakehand grip.

If you happen upon some table tennis while flipping channels on your television, watch for a little while and pay close attention to the way each player holds his or her racket.  Note, too, the type of surface on each side of each player's racket.

Celebrate reason today!

Today is the National Day of Reason in the US.  Started ten years ago, this day represents a push back against the National Day of Prayer.  The separation of church and state was an important part of our country's founding.  People are free to assemble and practice whatever religious beliefs they hold, and I would never want that freedom to disappear.  There are many people, however, who think it unconstitutional to use taxpayer money to fund a day of prayer.  As one of those people, I wish to add my voice to those who value reason and view it as a human being's greatest virtue.

To celebrate reason today, I will introduce my students to the beauty of Fourier analysis.  That we can untangle the complexity of bizarre wave patterns is something that always puts a chill on my spine.  Doing science well means setting aside a fear of being ignorant, asking questions, investigating the natural world, and then letting data and evidence take you to conclusions that may or may not make you happy.  Your opinion of the conclusions reached by good science has no effect on those conclusions.  Fourier's work survives nearly 183 years after he died because of the reason and brilliance he put into it.  If you ever do any type of signal processing, be sure to thank Joseph Fourier!

If you are interested in reading more about the National Day of Reason, click here.

The Path of a Home Run

As of Sunday, 28 April 2013, the longest home run hit in the Major Leagues so far was hit by Anthony Rizzo of the Chicago Cubs.  The left-hander hit a shot off righty Alexi Ogando of the Texas Rangers on a rainy day in Wrigley Field on the 18th of April in the bottom of the third inning with nobody out and a man on first.  Video of the home run may be found here.  Though the ball hit the back of the bleachers, an estimate of where the ball would have landed on the ground (really North Sheffield Avenue) has been made.  A great website that tracks all Major League home runs is Hit Tracker, which may be found here.  If one sorts all home runs by true distance, one finds that Rizzo's shot would have traveled 475 ft (145 m) horizontally.  Also provided are the launch speed off the bat, which was 115.0 mph (51.4 m/s = 185 km/hr), and the launch angle measured from the horizontal, which was 24.5 degrees.  The maximum height of 86 ft (26 m) is also given.

With all the great data provided, anyone can play with real home-run trajectories.  I describe how one may do this in an aerodynamics review article I wrote that just appeared online (click here to access the paper).  By choosing the appropriate drag and lift coefficients, I can fit a model trajectory to one that matches the data on the website.  I use constant aerodynamic coefficients as a first approximation, and I ignore the tiny difference between initial and final heights (about a meter, which is only about 0.7% the size of the horizontal range).  My model doesn't include wind or effects of rain, but it does give quite reasonable estimates of the sizes of the forces on the ball while in flight.

The buoyant force on the baseball was just under 0.2% of the ball's weight (my online article has a typo; the buoyant force I consider there should have been 0.15% of the ball's weight instead of 1.5%).  Clearly that force isn't a big player here!  The drag force is about 1.5 times the ball's weight just after the ball left Rizzo's bat.  If you solve a projectile motion problem with "ignore air resistance" in the problem statement, know you are not solving a realistic problem!  The initial lift force, which is due to the roughly 2000 rpm backspin the ball had when it left the bat (only around 500 rpm when the ball landed), was about 80% of the ball's weight.  Ignoring the effect of the ball's spin is also highly unrealistic!

The graph below shows three trajectories (click on the image for a larger size).

The dotted curve is what the trajectory would have looked like in vacuum.  That trajectory is nearly 41% too far.  If one includes drag, but not lift, one gets the dashed trajectory.  But that one is just over 17% too short.  The Goldilocks trajectory is the solid trajectory, which is my model of Rizzo's home run.  I missed the actual range by just 0.005% and the actual maximum height by 0.05%.  I could, of course, tweak my drag and lift coefficients to do even better, and I could include the slight difference in launch and landing heights, but pursuing this much further is silly because I don't know the true atmospheric conditions on that rainy day in Chicago.  The fun part is getting a trajectory that matches the real-world trajectory quite well and then studying the forces involved.

Sports and Terrorism

"I don't have a single American friend, I don't understand them."

-- Boston terror suspect, killed on 19 April 2013

For anyone having trouble understanding Americans, allow me to help you.  Nobody can help the person who authored the words quoted above, and it's doubtful anyone can help his younger brother, who is in custody right now.  I couldn't possibly speculate on the motives of those involved in what happened in Boston this past week.  People in various agencies will do their best to sort all that out.  What immediately stood out for me was the contrast between the scene at the conclusion of a marathon and the desire to end life.

I have never run a marathon, never come close to running anywhere near 26-plus miles (42-plus km) in a single day.  One of my cousins did it, and I was extremely proud of and amazed by what he did.  Imagine what it takes to run a marathon.  Weeks and weeks of training, disciplined diet, targeted exercises, and putting one's mind into the proper place to endure such a grueling task are all part of the preparation.  People who run marathons do so for a variety of reasons.  They may want to improve fitness, achieve a goal they thought unreachable, or maybe they hope to inspire someone else.  From what marathon runners have told me, crossing that finish line is a special moment.  Runners feel great about themselves and loved ones are inspired by what they've just witnessed.  The finish line of a marathon is a celebration.

On 15 April 2013, the finish line of the Boston Marathon turned from celebration to tragedy.  One of the great days in sports became a day during which people were killed and other people were maimed.  For anyone who doesn't understand Americans, or, more generally, people capable of courage and empathy, traits in the majority of human beings, regardless of nationality, look at what happened this past week.  Immediately after the bombs went off, people ran into the smoke to help people they had never met.  Nobody was asked what religion they belong to, what political party they support, or what sports team they support.  None of that mattered.  People simply helped their fellow creatures because those creatures were suffering.

Think about the medical professionals who tended to the wounded at the bombing scene, during ambulance transport, and at hospitals.  Many more health professionals have a lot of work ahead of them as they care for those physically and mentally scarred.  All will be helped and it won't matter what color the victims are, how the victims feel about various social issues, or what the victims' countries of origin happen to be.

Consider the images of the large number of law enforcement officers charged with keeping people safe and hunting down the suspects.  Those officers were made up of people of both sexes, all colors, numerous religious and nonreligious beliefs, political alliances, and so on.  A police officer is charged with protecting people, even people who may be as different from that officer as one can imagine.

Have those who don't understand us seen images from sporting events?  It was common to see baseball and basketball games with slogans like "We are all Boston" from shirts to big stadium screens.  As a passionate alumnus of both Vanderbilt University and Indiana University, I root for my Commodores and my Hoosiers.  I especially root for my teams when we play against bitter rivals like Tennessee and Purdue.  But if terrorism ever hits my rivals' campuses in Knoxville or West Lafayette, I'll feel solidarity with those who suffer and I'll want to help.  When people were murdered at Virginia Tech in 2007, I was warmed by the fact that not only did my own school help, but so did Virginia Tech's rival, the University of Virginia.  When tornadoes tore through Tuscaloosa in 2011, people from Auburn came to help, and there is no more bitter rivalry in sports than the one between Alabama and Auburn.

Nothing I write here is meant to suggest that all sports fans or all Americans are perfect people.  Many of my fellow creatures are quite capable of behaving badly toward one another.  There are roughly 45 murders per day in my country, a number embarrassingly too high by 45.  But most of us are able to put aside tribalism for solidarity when circumstances demand such a replacement.  We may feel more comfortable around those who look like ourselves or share common beliefs or root for the same sporting teams or vote for the same political parties.  It is natural to feel comfort in similarity and caution when facing differences.  A long, long time ago, it helped that our ancestors felt solidarity around each other and wary of lions and tigers, to give a cartoonish example.  In civilized 21st-century societies around the globe, people are enlightened enough to know that some differences among humans are trite and some differences help make societies stronger.  For those not lucky enough to have born into enlightened societies, know that there are many of us who feel solidarity with those seeking freedom.

Sport often brings out the best in people.  Athletes try to better themselves and inspire and entertain others.  The events in Boston gave us a vivid contrast between the best and worst of what human beings can do.  For those who don't understand America, I urge you to find a television and watch the Boston Marathon in 2014.  Bombs and the random taking of human life did not create the solidarity most Americans feel for people in need, they merely revealed what was already there.

Two Great Birthdays Today

On my drive to the gym this morning, I passed right by Poplar Forest, which was Thomas Jefferson's retreat home.  Just over a mile from my own home, Poplar Forest greets me during my drives to my place of work, Lynchburg College, as well as my trips to the gym.  Today's pass by Jefferson's second home got me thinking more about him because he was born on the 13th of April in 1743 (because Jefferson was born before the 1752 calendar adjustment, his birthday is sometimes given as 2 April 1743).  Can you even imagine what the world was like 270 years ago when Jefferson was born?  I consider myself fortunate to have been born in the 20th century in a country that Jefferson played such a pivotal role in founding.  Born out of the Philadelphia enlightenment of the latter half of the 18th century, my country has codified laws that protect our freedoms.  We are free to think what we want and pursue happiness.  Our founders, particularly Jefferson, saw the need to separate church and state, an idea integral to what makes my country great.

Another person I think about today is Christopher Hitchens, who was also born on the the 13th of April (in 1949).  One of my favorite modern writers, Hitchens moved me to think about politics and philosophy in so many new and different ways.  Though he died at the end of 2011, I continue to read his writings and listen to his speeches and debates (YouTube is a great resource!).  I am in awe reading and listening to Hitchens because I  know that it would take me the rest of my life to even be half as well read as he was.  I recently read Thomas Jefferson:  Author of America by Christopher Hitchens (get it here at Amazon).  I can't recommend it highly enough.

The two aforementioned polymaths certainly had their flaws, but one indelible character trait they shared was a lifelong commitment to learning.  I have found that I do better science when I exercise my mind in nonscientific arenas.  Studying history, philosophy, politics, and so forth have helped me think in better ways about how I approach problems in science.  Both Jefferson and Hitchens were well traveled.  I did not take my first real steps away from my own country until I was 30 years old.  Living in another country and visiting a half dozen other countries have opened my mind considerably.  I've also learned how people in other countries approach scientific problems, which has benefited me greatly in the past decade.  If you've never done so, I urge you to see how other people in countries foreign to your own live and do things -- it's well worth it!

Earning high school, college, and universities degrees are significant achievements.  But I've always thought that degrees are merely the keys that open doors to opportunities to learn even more.  Don't ever walk across a graduation stage and think that learning is finally over and you can relax.  Too much enjoyment of life awaits you if you choose to keep learning.

Great national title game!

Congratulations to the Louisville Cardinals for beating Michigan and winning the men's national title in college basketball.  A great game was played tonight, and it was tough seeing either team lose.  I've got friends and family from Michigan and they are certainly disappointed.  Don't hang your heads, Wolverines fans!  Your team had a fantastic year and is bound to be great for the next few seasons given how young its players are.  As an Indiana alumnus, I fear how good Michigan will continue to be.

For those itching for a little basketball science, check out The Physics of Basketball by John J Fontanella (click here for the Amazon page).  My publisher, The Johns Hopkins University Press, publishes Fontanella's book.  It's a fun read!

The Louisville women will try to match the men's team when they take on UConn tomorrow night.  UConn will be very tough to beat.  Can Louisville do it two nights in a row?

The morning after ... a great day!

After watching my Hoosiers play their worst game of the year last night in losing to Syracuse, I spent a mostly sleepless night wondering why my team couldn't hit the broad side of barn.  I got up early, kissed my younger daughter, and informed her that Indiana lost last night.  She was disappointed, but happy that the weekend is here.  Sports are great, and I live and die with my teams, but life is so much more than sports.  It doesn't feel that way after a terrible loss, but life really is great.  We get one shot at life and each day needs to be special.  If your day doesn't feel special by the time noon rolls around, do something about it.  Seriously, take charge and don't let Saturday get here without doing or thinking or playing in a special way.

What will make my day special?  Well, my daughter got me off to a fantastic start.  In less than half an hour, I get to talk to my introductory physics class about electromagnetic induction and Faraday's law -- my favorite topic of the semester!  If understanding how modern economies are maintained doesn't give you a chill on your back, you're not paying attention.  If seeing energy conservation in a little minus sign doesn't give you pause at the wonder of how the universe works, you're not trying hard enough.  The time and effort spent on learning about Faraday's discovery will be well worth it -- I promise.  Once Faraday realized that changing magnetic field lines through a coil induces a current in that coil, humanity was ready to undergo a revolution in thought and in how we live.

So, yes, last night's loss stung me.  But, today is a special day because I get to share the wonder of the universe with some great kids.

Parallel Blogs

My college was interested in having me put my blog posts on its blog site.  I will thus copy posts from here to my Lynchburg College Red Chair Blog site, which can be found by clicking here.  This blogspot site remains my primary blog site.

When one second feels like forever ...

My beloved Indiana Hoosiers basketball team faced a tough challenge yesterday.  We were to play a tenacious Michigan team on its home court with the Big Ten conference title on the line.  A loss, and we would tie with three other teams for the league crown, including Michigan.  A win, and we would have the title all to ourselves, something we've not had in 20 years.

As a myopic fan, my blood pressure rises and falls with each play.  Successes and failures are magnified to, admittedly, insane heights.  Any die-hard sports fan reading this knows exactly what I mean.  You know all the implications of winning and losing, and you know them well in advance of any game you watch.  If your team wins, you show up for work the next day with a big smile on your face, and you are dying to talk about your team's victory.  If your team loses, you get to work and feel like eyes are upon you.  Are there fans of the team that beat you who are anxious to "ask" you about the game?  Of course you want to talk about the loss, as if conversation can help you understand what happened.  This is all lunacy, but isn't is nice to have things in your life about which you feel so much passion?  After my family and my work, I'm thrilled being passionate about college basketball; I'm a true fanatic.

The game went back and forth.  We got up seven early; Michigan was up 11 with about five minutes left in the first half.  We cut that lead to three by halftime.  Both teams had bursts of excellence and seemingly longer stretches of futility.  The second half was a whirlwind of missed shots and mistakes by both teams.  There were also plenty of fantastic plays as each team kept claiming the lead.

Michigan was up five points with about 45 seconds left and I thought we had lost.  We had missed some shots and turned the ball over twice in the past minute and a half to get ourselves in a hole.  In that final 45 seconds, Michigan would not score again and Indiana's Cody Zeller would account for all six of IU's points.  We won by a single a point.  My kids and I were going bananas.

What made the game especially gut-wrenching for fans of both teams was the final possession by Michigan.  Click here to see our final basket and Michigan's attempt to win it.  Michigan's great point guard, Trey Burke, missed a tough shot near the basket.  Jordan Morgan was in perfect position for a tip-in, but the ball rolled on the rim for what seemed like an eternity, only to fall out of the hoop.

To understand what happened on the final play, I turned on the physics side of my head.  The image below shows the ball precariously perched on the rim after Morgan's tip-back (click on the image for a larger view).

"The Rock," as a basketball is sometimes called, is seen with the Michigan logo on it.  According to my timing, the ball rolled around the front of rim for a time of about one second.  A basketball has a diameter at least 9.39 in (23.85 cm) and at most 9.55 in (24.26 cm).  The black channels you see on the ball cannot be more than 1/4 in (0.635 cm) deep.  The metal ring that comprises the hoop is 18 in (45.74 cm) in diameter; the ring itself is about 5/8 in (1.59 cm) in diameter.

What forces did the "The Rock" feel while the IU/Michigan game was in doubt?  The ball's weight is between 20 ounces (5.56 N) and 22 ounces (6.12 N).  Taking an average weight and an average ball diameter, the buoyant force on the ball is about 1.5% of the ball's weight.  If the ball rolled on about 30% of the rim, the ball moved along 17 in (43 cm) of rim in roughly one second.  That results in an average speed of around 1.4 ft/s or 0.96 mph (1.6 km/hr).  Air resistance on the Michigan shot would have been small while the ball was on the rim, and it would have caused the ball to slow a little while rolling.  The normal force from the rim would have been comparable to the ball's weight.  Friction between ball and rim would have reduced both the rolling rate and the transnational speed of the ball, arresting the motion slightly to allow a gravitational torque to send the ball into the hoop.

What Michigan needed was a little more lever arm on the gravitational torque on the ball.  We are unstable if our center of gravity is outside our feet.  Had the line of the ball's weight vector been more in the hoop than through the rim or just outside it, Michigan would have won.  Of course, the torque created has to arrest motion that takes the ball out of the hoop.  Imagine a ball travelling fast over the hoop -- an air ball.  The ball's weight vector will pass through he hoop, but the ball won't go in because it would have been moving too fast over the hoop.

As passionate as I am about Indiana basketball, I never want to pour salt in an opponent's gaping wound created by a tough loss.  I've got good friends and even some family members who are fans of Michigan.  They are as sickened by the loss as I would be if the ball had gone in.  Agony and ecstasy came down to mere millimeters.  My team is lucky to have won.

Congrats to Australia!

Australia dominated West Indies to win the Women's Cricket World Cup.  The win marks the sixth overall for the Southern Stars.  Congratulations to Australia!

There is a great deal of fascinating physics in the sport of cricket.  A lot of research has focused on cricket ball aerodynamics.  My introduction to that line of research came in the form of well-written papers by Rabindra D Mehta of the NASA Ames Research Center in Moffett Field, California.  Mehta's classic 1985 paper "Aerodynamics of Sports Balls" in Annual Review of Fluid Mechanics (vol 17, pp 151-189) describes swing bowling.  His 2005 paper "An overview of cricket ball swing" in Sports Engineering (vol 8, pp 181-192) has cogent descriptions of reverse swing, a phenomenon achieved by fast (over 90 mph = 145 km/hr) bowlers or with balls that have been strategically scuffed.  Look up those papers if you want more details than what follows.

The side-to-side movement of a cricket ball boils down to getting an asymmetric deflection of air off the back side of the ball.  The rough seams usually help delay the separation of the boundary layer of air from the ball.  If you've ever thrown a Whiffle Ball, you know that the ball deflects toward the holes, ie the rougher part of the ball's surface.  Air moving over a cricket ball that has a seam predominately on one side and a smooth side on the other will make the ball move toward the seam side.  The reverse of that effect can happen if the ball is thrown very fast, fast enough that air flow over the entire ball is turbulent.  In that situation, the seams actually serve to help separate the boundary layer closer to the front of the ball compared to the smooth side.  That leads to reverse swing.

Cricket news doesn't make for much water-cooler chat in the US.  In countries like India, Australia, and England (just to name a few), sports fans care a great deal about cricket.  Though I played cricket only a few times while in graduate school, I enjoy following the World Cup for each gender.  I especially love all the great physics to be learned in studying cricket!

Enjoy Darwin Day!

Today marks the 204th anniversary of the birth of Charles Robert Darwin.  In the 74,510 days since Darwin's birth, our growing understanding of life has given us remarkable ways to view our place in the universe.  One aspect of that understanding that particularly fascinates me is our kinship with all living creatures.  What an exciting way to think about the natural world!

The scientific pursuit of truth involves the acquisition of data and evidence to support propositions.  We need not "believe" a scientific proposition.  If data and evidence don't exist to support a given proposition, that proposition won't be accepted as a description of nature.  Scientists go where the evidence takes us, and we do not fear overturning previously-held ideas.  We continually try to falsify claims; failure to do so for a particular claim leads us to the conclusion that that claim glimpses a truth in nature.  We accept what we find whether we like the results or not.  Removing confirmation bias and solipsism is not always easy, but good science requires it.  Galileo Galilei supposedly said "eppur si muove" prior to the Inquisition.  Most likely apocryphal, "and yet it moves," in reference to the Earth's motion around the sun, the remark is now used to get the point across that our beliefs are irrelevant when it comes to data and evidence acquired through scientific inquiry.

The evidence to support evolution is overwhelming.  It does not require "belief," even though people are often asked if they "believe" in evolution.  Denying evolution is tantamount to denying, for example, what we know about gravity.  A Gallup Poll published last year (click here for the story) reveals an embarrassing low percentage of US citizens who accept the scientific claims associated with evolution.  A 2006 article in Science showed public acceptance of evolution in the US to be next to last among the 34 countries surveyed (click here for the country chart).  The richest country in human history with the ability to provide public education to its citizens should be chagrined by its lack of scientific literacy, especially given that On the Origin of Species was published almost 154 years ago.

The good news is that days like today have meaning.  We celebrate the ideas that revolutionized our understanding of the natural world. With the ever-increasing advance of technology and the spread of information, we should be hopeful that scientific literacy will improve.  Darwin Day helps in this effort.  People like Congressman Rush Holt of New Jersey help, too.  A physicist, Holt led the effort to have today recognized as Darwin Day in the US.  Kudos to Dr Holt!

If you know very little about Darwin's ideas, there are many easy-to-read books out there.  I love The Greatest Show on Earth by Richard Dawkins (click here to get it).  Neil Shubin's Your Inner Fish (click here to get it) is also a wonderful read with a concluding chapter that you'll want to read twice (at least!).  Never feel ashamed if you are ignorant about something.  Knowing everything would mean never being able to experience the thrill of learning.

Have a great Darwin Day!