Alaphilippe is Last Out and Fastest!

Julian Alaphilippe was the last rider released in today's individual time trial.  The yellow jersey wearer had the opportunity to win a stage on the 100th anniversary of the yellow jersey.  Thomas De Gendt spent much of the time trial in the hot seat.  But Geraint Thomas came in 22" quicker, and then all eyes turned to Alaphilippe.  The Frenchman gave it his all during the final kilometer and came in 14" quicker than Thomas.  Check out Alaphilippe's exertion at the finish line (click on image for a larger view).

We had our best prediction today.

• Stage 13:  35' 00" (actual), 34' 52" (prediction), 00' 08" fast (-0.39% error)

I'm most definitely happy with that!  Check out Alaphilippe's average speed.

• Stage 13:  12.95 m/s (46.63 kph or 28.97 mph)

That's pretty fast!  Look at Alaphilippe's great form on the bike near the end of the stage, where he kicked it up a notch and took control (click on image for a larger view).

You can see the speed there, which is 54 kph (34 mph).

Time trials are so much fun to watch, especially for a physicist.  The tailor-made skin suits are crafted to exactly fit each rider.  The goal, of course, is to reduce air drag.  Several riders didn't push very hard today, likely wanting to save energy for what's awaiting them in the next two stages before the second and final rest day.  Who else but Peter Sagan would be popping a wheelie on the stage? (click on image for a larger view)

He definitely gave fans something to smile about!

There were some unfortunate crashes during the time trial.  Stefan Küng crashed early in the route.  Maximilian Schachmann crashed and barely made it across the finish line.  I was so anxious to see what time Wout van Aert would get.  I was hoping he could sneak in under 35'.  But he had an awful crash with just over 1 km left in his ride (click on image for a larger view).

Tomorrow's Stage 14 looks to be a grueling mountain stage.  Beginning in the commune of Tarbes, riders will meet a category-1 climb in the middle of the stage.  They'll ride across the 1474-m (4836-ft) peak of Col du Soulor in the Pyrenees.  The 117.5-km (73.01-mi) stage ends with an Hors catégorie climb to the 2115-m (6939-ft) peak of Col du Tourmalet.  Our prediction is given below.

• Stage 14:  3h 19' 37" (prediction)

I can't wait to see that climb to the finish line!

Simon Yates Takes a FAST Stage 12!

Brit Simon Yates out-sprinted Pello Bilbao of Spain and Austrian Gregor Mühlberger to win a very fast Stage 12.  It was a lot of fun watching the three of them help each other on the rapid descent off La Hourquette d'Ancizan.  They alternated lead position and helped draft each other.  That kept the pursuers at bay.  Check out Yates coming in just ahead of Bilbao and Mühlberger (click on image for a larger view).

Bilbao is on the right; Mühlberger is on the left.  I was stunned that the winning time came in under five hours.  Our prediction wasn't great.

• Stage 12:  4h 57' 53" (actual), 5h 23' 17" (prediction), 25' 24" slow (8.53% error)

We were nearly perfect on the first mountain stage, which was the grueling Stage 6 with its category-1 climb finish.  That stage was 49 km (30 mi) shorter than today's stage, but the top cyclists today output 13% more power today than during Stage 6.  Were they holding back on Stage 6, going crazy today, or is there a better explanation?  This really has been a fascinating year for modeling the Tour de France!  Yates's average speed is given below.

• Stage 12:  11.72 m/s (42.20 kph or 26.22 mph)

I love watching the mountain stages.  Check out Tim Wellens crossing the top of Col de Peyresourde (click on image for a larger view).

A little later, Simon Yates and his two finishing companions were first atop La Hourquette d'Ancizan (click on image for a larger view).

On the first big descent, speeds reached over 90 kph (56 mph).  I just can't imagine going that fast on a bicycle.  And of course scenery was spectacular in the Pyrenees.  Check out one of the valleys on the final descent (click on image for a larger view).

The Tour de France is quite an advertisement for visiting France!

Tomorrow's Stage 13 is an individual time trial.  The 27.2-km (16.9-mi) route begins and ends in Pau.  Riders will loop south and then back north during their rides.  Our prediction is given below.

• Stage 13:  34' 52" (prediction)

Will there be a shakeup in the general classification tomorrow?

Ewan Out-Sprints Groenewegen for Stage 11 Win!

Though the stage wasn't quite as fast as I thought it could be, Stage 11 gave fans yet another great day of Tour de France racing.  Aussie Caleb Ewan just barely finished ahead of Dylan Groenewegen for the stage win (click on image for a larger view).

I was a split second early with my screen capture, but you can see Ewan in read and white leaning just ahead of Groenewegen in yellow and black.  See how our predication fared.

• Stage 11:  3h 51' 26" (actual), 3h 39' 54" (prediction), 11' 32" fast (-4.98% error)

I thought we'd be a bit closer, but racing in the first half of the stage was slower than I anticipated.  But check out Ewan's average speed.

• Stage 11:  12.03 m/s (43.30 kph or 26.90 mph)

Not too shabby!  I suspect the cyclists will be somewhat rested for tomorrow's Stage 12, which is a 209.5-km (130.2-mi) long mountain stage.  Picking up in Toulouse, where Stage 11 ended, cyclists will travel southwest into the Pyrenees.  Category-1 climbs up Col de Peyresourde and La Hourquette d'Ancizan will highlight the stage.  The stage ends with what could be a ferocious downhill sprint into Bagnères-de-Bigorre.  Our prediction is given below.

• Stage 12:  5h 23' 17" (prediction)

I'm anxious to see the world's best cyclists climb those two mountains tomorrow.  Will there be a shakeup in the general classification?

Stage 11 Prediction

Tour de France riders are resting today.  Tomorrow's Stage 11 is an interesting stage.  It begins in Albi, where riders are resting.  The 167-km (104-mi) flat stage will take the cyclists around a loop to the west, followed by a stretch to the south, and then west again.  There are several little climbs, but nothing like what cyclists will face the next day in Stage 12.  The stage finishes in Toulouse, which is where Stage 12 commences.

What makes tomorrow's stage so interesting is that team strategies will, like they often do, dictate the pace of the race.  Will the stage be short enough that several riders will break away and try to get a stage win?  Will Stage 12's mountain climbs worry those competing for the general classification enough that they'll ride Stage 11 at a leisurely pace?  We certainly don't know the teams' strategies!  Our model has the stage at a fairly fast pace.

• Stage 12:  3h 39' 54" (prediction)

Stage 7 so crushed me that I'm worried that I'll be watching a stage and wondering why the cyclists aren't doing anything more than looking at the scenery.  And then thoughts of Stage 3 enter my mind, which makes me worried about watching a stage with my jaw agape at just how fast the riders are going.  I'll take the second scenario because I like watching fast racing.  The physics is easy.  Anticipating what teams choose to do is much more difficult.  I can't wait to see the Tour de France back in action tomorrow!

Wout van Aert Out-Sprints Everyone!

Despite not having help from teammates at the very end of today's stage, Belgian cyclist Wout van Aert just edged Italitan Elia Viviani for the win.  Viviani was denied his second win of this year's Tour de France as van Aert got a third win for Belgium.  Check out how close the finish was (click on image for a larger view).

That's van Aert in the yellow and black, just ahead of Viviani in blue.  Racing was very fast today, and I could tell halfway into the stage that our prediction would be a bit slow.  Several riders got caught behind the lead group of sprinters that emerged from the peloton.  Giulio Ciccone fell all the way from 2nd and only 23" behind to 10th place in the general classification,  02' 32" behind Julian Alaphilippe.  Thibaut Pinot went from 3rd and just 53" behind to 11th and 02' 33" behind.  Pinot will be among many cyclists who will be kicking themselves this evening.

We might want to kick ourselves for not upping our power a bit on a stage prior to a rest day.  Still, I wasn't expecting cycling to be quite so fast.

• Stage 10:  4h 49" 39" (actual), 5h 10' 40" (prediction), 21' 01" slow (7.26% error)

Look at van Aert's average speed.

• Stage 10:  12.52 m/s (45.05 kph or 28.00 mph)

That average speed was 2 kph faster than the fastest imagined by the race organizers.  I confess that predicting stage-winning times is much harder this year.  My students and I have enjoyed years with half the stages predicted to better than 3%.  This year, we've predicted half of the first 10 stages to better than 4.6%.  But we've really missed on a couple stages.  We had Stages 3 and 4 completely flipped, and we never imagined such a slow Stage 7, even after a grueling Stage 6.  The fact that predicting is getting more challenging motivates me to continuing learning.  Life as a scientist is never dull!

Cyclists will enjoy a rest day in Albi tomorrow.  Stage 11 will be pick up there on Tuesday.  I'll post our prediction for Stage 11 during tomorrow's rest day.

Impey Makes South Africa Proud!

South African cyclist Daryl Impey held off a furious challenge from Belgian Tiesj Benoot in the final sprint to the finish to take Stage 9.  It was a great stage to watch if you love attacks and pursuits, but not so much if you expected the famous sprinters to get out of the peloton and compete for the stage win.  The gap established by the leaders and pursuers was large enough that the peloton was happy to enjoy a leisurely ride to the stage end.  Check out Impey crossing the finish line (click on image for a larger view).

Our model did quite well today.  But as I noted in yesterday's post, I was rooting for the lead riders to sneak in under 4 hours.

• Stage 09:  4h 03' 12" (actual), 3h 56' 42" (prediction), 06' 30" fast (-2.67% error)

Given that the main sprinters were not a factor in the stage win, I'm more than happy with our error.  The peloton, including Julian Alaphilippe, came in more than 16 minutes later.  Alaphilippe keeps the yellow jersey for France on Bastille Day.  Some of the bigger sprinters, like Peter Sagan, came in more than 5 minutes after the peloton.  Check out Impey's average speed below.

• Stage 09:  11.68 m/s (42.06 kph or 26.14 mph)

It was a tad slower than our model predicted, but impressive nonetheless.

Tomorrow's 217.5-km (135.1-mi) Stage 10 is listed as flat, but with a category-4 climb and three category-3 climbs, it could very well have been classified as a light hilly stage.  The commune of Saint-Flour hosts the start of the stage, and then riders travel southwest to Albi.  They'll be making their way to the Pyrenees.  Our prediction is given below.

• Stage 10:  5h 10' 40" (prediction)

Cyclists will stay in Albi after the stage ends.  Tuesday will be the first rest day.  Will cyclists go all out, knowing that they'll be able to rest on the following day?  Will I be rooting for the lead cyclists to not sneak in under 5 hours?!?

An Inspiring Ride by Thomas De Gendt!

There is neither a rider nor a team that I'm rooting for in this year's Tour de France.  But there are stages like today's Stage 8 when it's impossible for me to stay neutral.  Thomas De Gendt was awe inspiring today.  The 32-year-old Belgian broke away early in the race.  He and Italian cyclist Alessandro De Marchi cooperated for much of the race, and when De Marchi nearly crashed and nearly took out De Gendt (click on image for a larger view),

cooperation continued after De Marchi caught up with De Gendt inside of 60 km (37 mi) left in the stage.  But on the final category-3 climb, De Marchi could no longer stay with De Gendt.  I caught the screen capture below when I saw De Gendt look back, perhaps thinking he was going to have to win it alone (click on image for a larger view).

I was then pulling hard for De Gendt to make it to the finish line without being caught.  And he didn't disappoint!  Check him out full of joy as he's won the stage (click on image for a larger view).

You can see Thibaut Pinot and Julian Alaphilippe, who came in second and third, respectively, in the background after they valiantly tried to catch De Gendt.  I was hoping De Gendt would sneak in under 5 hours, but I was nearly yelping with how good our prediction turn out.

• Stage 08:  5h 00' 17" (actual), 4h 55' 42" (prediction), 04' 35" fast (-1.53% error)

After yesterday's disastrous prediction, I would have been happy with 5% today.  But I'm thrilled our model performed much better than 5%.  Our model has had lots of ups and downs so far.  The yellow jersey has had some back and forth, too.  Alaphilippe wrested the yellow jersey from Giulio Ciccone, who now sits 23" behind Alaphilippe.  Pinot is 53" back in third place.  Can a French rider take the Tour de France for the first time since Bernard Hinault won in 1985?

Check out De Gendt's impressive average speed below.

• Stage 08:  11.10 m/s (39.96 kph or 24.83 mph)

Tomorrow's 170.5-km (105.9-mi) hilly stage picks up where today's stage ended, in Saint-Étienne.  Riders won't have to any more traveling today!  One category-1 climb and two category-3 climbs greet riders on their way to the commune of Brioude.  They will mostly go west, but a little south, too.  Our prediction is given below.

• Stage 09:  3h 56' 42" (prediction)

I'll probably do tomorrow what I did this morning, and that's hope a rider gets in under the closest hour mark.

It's Groenewegen by a Nose!

Dylan Groenewegen has definitely put his Stage-1 crash behind him.  He looked great on the final sprint, just edging ahead of Caleb Ewan.  Check out how close the finish was (click on image for a larger view).

That's Groenewegen on the right in yellow and black; Ewan is on the left in red and white.  Peter Sagan is in the middle; he came in third.

And now we come to our prediction.  I began watching the stage early this morning, hoping our prediction would be as good as yesterday's.  But then the racing turned out to be very pedestrian, sluggish, in fact.  Narrow roads squeezed the peloton in many places, but the riders simply looked content to take it easy on today's longest stage.  As the stage went on, I realized we were in for a terrible prediction today.

• Stage 07:  6h 02' 44" (actual), 5h 21' 48" (prediction), 40' 56" fast (-11.28% error)

This is, by far, our worst prediction of the race.  And it came after nearly being perfect yesterday!  Such are the vicissitudes of predicting the Tour de France.  Check out Groenewegen's average speed.

• Stage 07:  10.57 m/s (38.04 kph or 23.64 mph)

That's 2 kph slower than what race organizers thought would be the slowest average speed.  I'm sure fans on the sides of the roads were anxiously awaiting the peloton to come by, albeit later than they expected.  Did yesterday's grueling Stage 6 zap the riders' legs?  Most likely so.  We need to do better in the future anticipating such drop-off in performance after especially difficult stages.

Tomorrow's Stage 8 commences in Mâcon and takes riders 200 km (124 mi) south to Saint-Étienne.  The hilly stage has two category-3 climbs and five category-2 climbs.  Our prediction is given below.

• Stage 08:  4h 55' 42" (prediction)

We have the correct physics in our model, but we need to do better anticipating strategies.  We nailed it yesterday, but then botched it today.  What will tomorrow bring?

Teuns Conquers Final Brutal Climb!

Belgian Dylan Teuns outlasted Italian Giulio Ciccone on the 24% grade over the final 100 m in today's Stage 6.  I sat in my air-conditioned office watching the stage this morning.  Never more accomplished on a bicycle than a few leisurely 20-km rides, I was in awe watching the world's best do what only a tiny fraction of the world's population could do.  Check out Teuns crossing the finish line as the gradient "softened" to 21% (click on image for a larger view).

You can see Ciccone about to come in second.  He'll take it because Julian Alaphilippe struggled mightily over the last few meters and barely crossed the finish line in sixth place.  That cost Alaphilippe the yellow jersey; he's 6 seconds behind in second place.  We'll see Giulio Ciccone in yellow tomorrow.  Check out Teuns's winning time and how it compares with our prediction.

• Stage 06:  4h 29' 03" (actual), 4h 24' 40" (prediction), 04' 23" fast (-1.63% error)

I'm ecstatic that our model did so well today!  We would have had to trim less than 1% off our model cyclist's power output to exactly match the winning time.  Below is Teuns's average speed.

• Stage 06:  9.94 m/s (35.79 kph or 22.24 mph)

That average speed is a typical sprinter's speed in a 100-m dash.  Going up the final climb, cyclists could only manage a third of that speed.

Tomorrow's 203-km (143-mi) flat stage is the race's longest.  Cyclists begin in Belfort, which is very near the border with Switzerland.  They'll travel southwest to the commune of Chalon-sur-Saône.  Our prediction is given below.

• Stage 07:  5h 21' 48" (prediction)

It would be great to see our prediction come in under 2% again!

Sagan EXPLODES to Stage 5 Win!

I love watching Peter Sagan on a bicycle!  Peter the Great absolutely exploded inside 200 m to the finish line and won Stage 5.  No second place for Sagan today!  Check him out going across the line (click on image for a larger view).

He then went into Hulk mode, perhaps letting the cycling world know that the green jersey is his and his alone (click on image for a larger view).

Today's hilly stage had some impressive climbing.  Check out Xandro Meurisse after he was the first to reach the top of Côte des Cinq Châteaux (click on image for a larger view).

His was hitting a speed of 20 kph (12 mph) on a 10% part of the climb.  Wow!

We did a lot better today with our prediction, as you'll see below.

• Stage 05:  4h 02' 33" (actual), 4h 13' 41" (prediction), 11' 08' slow (4.59% error)

I still want that error under 3%, but I'll definitely take today's error after the past two stages.  Racing conditions were perfect today.  The European heat wave is gone, temperatures were in the 21°C - 25°C (70°F - 77°F) range, and climbs where crosswinds could have been a problem had lovely trees around the riders.  Racing was just a tad faster than we thought it would be.  Sagan's average speed is given below.

• Stage 05:  12.06 m/s (43.41 kph or 26.98 mph)

Tomorrow's 160.5-km (99.7-mi) Stage 6 is the year's first mountain stage, and it looks to be a fun ride.  The stage begins in Mulhouse, very near the French borders with Germany and Switzerland.  Riders will have a mostly category-1 climb to near the peak of Grand Ballon.  They'll reach a stage-high altitude of 1336 m (4380 ft).  A category-1 climb to near the peak of Ballon d'Alsace occurs just past halfway into the stage.  What I'm anxious to watch is the final category-1 climb to the finish at La Planche des Belles Filles, right in the Vosges Mountains.  Climbers will be on full display tomorrow!  Our prediction is given below.

• Stage 06:  4h 24' 40" (prediction)

Will we be a bit slow again?  The cyclists impress me this year!

GREAT Sprint by Viviani in Stage 4!

I got to watch today's stage, and I wasn't disappointed.  Elia Viviani made Italy proud with a stupendous sprint in the last few meters to just take today's stage win.  Check out Viviani crossing the finish line (click on image for a larger view).

Viviani is on the right in blue, just ahead of Alexander Kristoff in the center in white and Peter Sagan on the left in green.  Viviani is 11 kg (24 lb) lighter than Kristoff and Sagan.  Did that help?  I don't know, but Viviani did a great job sneaking out of a slipstream near that wall on the right and charging toward the finish line at just the right time.

Now we come to our prediction.  It's wasn't great, but I'm fascinated nonetheless.  While watching the stage, there were comments about crosswinds and sluggish cycling.  I thus knew our prediction would be too fast as I watch the race unfold.  But it turns out that we had yesterday's stage and today's stage exactly backwards.  The slower pace we expected in yesterday's stage showed up today.  The high speed we thought would pervade today's stage was on display yesterday.  We missed today's stage by the exact same time that we missed yesterday's stage, but in the opposite direction!

• Stage 04:  5h 09' 20" (actual), 4h 42' 50" (prediction), 26' 30" fast (-8.57% error)

What's funny is that we have exactly matched the sum of yesterday's winning time and today's winning time, but that's little consolation for two less-than-stellar predictions.  Viviani's average speed is given below.

• Stage 04:  11.50 m/s (41.41 kph or 25.73 mph)

Tomorrow's Stage 5 is a 175.5-km (109.0-mi) hilly stage that begins in the commune of Saint-Dié-des-Vosges and ends in Colmar.  The stage has a couple of category-3 and a couple of category-2 climbs, but the finish looks to be very fast.  Our prediction is given below.

• Stage 05:  4h 13' 41" (prediction)

I hope we get back on track tomorrow!

Alaphilippe Wins FAST Stage 3!

I wish I could describe what happened during today's third stage of the Tour de France.  But I wasn't able to watch it.  I bought the gold pass from NBC to watch the entire race, but the website was inaccessible from my office.  I'm not even able to access a replay, several hours after the stage ended.  There will be no screen captures in this post.  I'll have to get to a comparison between our prediction and the actual result, and then get to our prediction for tomorrow's stage.

Julian Alaphilippe won a very fast stage today, and in the process of doing so, secured the yellow jersey for France for at least tomorrow's stage.  Our prediction wasn't great.

• Stage 03:  4h 40' 29" (actual), 5h 06' 59" (prediction), 26' 30" slow (9.45% error)

The days of being happy to get a prediction error less than 10% are long gone.  We clearly missed something today.  After reading a few summaries of the stage, we learned that there were some rather strong tailwinds.  If someone watched the stage, please let me know if it looked as if winds helped riders.  I'm anxious to learn of other reasons, too.  Alaphilippe's average speed was certainly greater than what we thought on a fairly flat, but hilly near the end, stage.

• Stage 03:  12.78 m/s (45.99 kph or 28.58 mph)

Given how long the stage was, I'm shocked at that average speed.  It's 3 kph greater than even what the Tour de France's website thought might be an upper limit for the average speed.

Tomorrow's Stage 04 is classified as flat, though there are a couple of category-4 climbs in the latter half of the stage.  We thought tomorrow's stage would be faster than today's stage.  The 213.5-km (132.7-mi) stage commences in Reims.   Riders will head mostly east where they'll finish the stage in Nancy.  Our prediction is given below.

• Stage 04:  4h 42' 50" (prediction)

Are the cyclists outputting more power than we expected?  Are they and their bikes more aerodynamic than what we've ascertained from recent publications?  I don't know, and that's what makes this so much fun.  It's time to learn something!

An Amazing Ride by Team Jumbo-Visma!

While watching the Tour de France live, the sports fan in me is always shouting louder than the physicist looking for a perfect prediction.  Team Ineos was finished with a time of 29' 17", and was watching team after team come in, trying to beat that time.  Our prediction was set to be just over 1% off.  But then came the last team, Team Jumbo-Visma, led by yesterday's winner, Mike Teunissen, donned in the yellow jersey.  I was on the edge of my office chair as they were about to start (click on image for a larger view).

The team's eight riders knew what time they had to beat, and they definitely proved the adage that last is not least.

In a team time trial, four of the team's riders must cross the finish line.  The team's time is in fact determined by the time when the fourth rider finishes.  I was anxious to see how Dylan Groenewegen looked after yesterday's crash.  He was unfortunately still showing the effects of the crash as he fell off the team's pace with about 17 km (11 mi) left.  But his mates kept up a torrid pace.  It was great watching the way the team members interchanged the tough lead position.  In the screen capture below, Steven Kruijswijk has just moved to the back (click on image for a larger view).

So much great physics in that image!  The closed back wheels help reduce drag by streamlining the wake of air separating off the bikes and riders.  Cyclists are crouched and helmets are tapered at the back.  The cyclist in front works hardest because there is no drafting for the leader.  By taking turns at the front, team members alternate who expends the most energy.  Athletes, trainers, nutritionists, engineers, physicists, and research and development teams in companies all work to creep ever closer to the limits constrained by the laws of physics.

By the time Team Jumbo-Visma was within a couple of kilometers of the finish line, I was rooting for them to sneak under 29 minutes.  Our prediction was going to be worse if they did, but so what?!?  They pulled it off, as you see below (click on image for a larger view).

Four need to finish, but it's always good to have at least five head for the finish, just in case one rider has a problem.  Check out how our prediction fared.

• Stage 02:  28' 57" (actual), 29' 41" (prediction), 00' 44" slow (2.53% error)

I'll most definitely take that error!  The team's average speed was incredible.

• Stage 02:  15.89 m/s (57.20 kph or 35.54 mph)

Try to imagine biking that speed with at least one other cyclist right in front of you and one other cyclist right behind you.  It's much harder than it looks!

Tomorrow's third stage commences in the western Belgian city of Binche.  Riders will leave Belgium and enter the French commune of Jeumont after about 12 km (7.5 mi) of cycling.  The 215-km (134-mi) hilly stage ends in the French commune of Épernay.  A category-4 climb and three category-3 climbs greet riders near the end of the stage, perhaps hinting at more serious climbs to come in later stages.  Our prediction is given below.

• Stage 03:  5h 06' 59" (prediction)

Can Team Jumbo-Visma make it three in a row???

Teunissen Sprints to First Stage Win!

Dutch rider Mike Teunissen sneaked up through the sprinters, drafted at the right moment, and then burst past Peter Sagan (who else would come in second?!?) to win this year's first stage.  This was a huge surprise for Teunissen, who earned his first grand tour stage win.  Check out how close the finish was (click on image for a larger view).

You can see Teunissen on the right, just edging Sagan at the finish line.  I tried getting a screen shot while watching live, but I couldn't tell who won (click on image for a larger view).

I actually thought Sagan had won, but then saw the replay, where I got the first screen capture above.  You can see the winning time in the upper left of my screen shot.  Teunissen will get a 10-second time bonus for the win, and he'll be donned in yellow tomorrow.  That means Sagan will be wearing Teunissen's green jersey.  Check out how Teunissen's time compares to our prediction.

• Stage 01:  4h 22' 47" (actual), 4h 32' 00" (prediction), 09' 13" slow (3.51% error)

It was a beautiful day for racing, and speeds in Brussels near the finish hit 78 kph (48 mph), so racing was just a tad faster than we thought.  I'll still take the relatively small error!  Teunissen's average speed is given below.

• Stage 01:  12.34 m/s (44.41 kph or 27.59 mph)

There were a couple of crashes that hopefully won't have big implications for the rest of the Tour de France.  Teunissen's Team Jumbo-Visma mate Dylan Groenewegen crashed with just about 1.5 km left in the stage.  I got a screen capture of the crash (click on image for a larger view).

I think that's Groenewegen lying face down with the yellow and black jersey.  Inside of 20 km left was a crash that scarred Swiss cyclist Jakob Fuglsang (click on image for a larger view).

The screen capture below shows some of the damage to Fuglsang, who may have been cut by his sunglasses (click on image for a larger view).

The Tour de France will be much better with Fuglsang and Groenewegen healthy and competing in top form.  I hope they're okay!

I have never been to Brussels.  Watching the Tour de France begin there makes me want to visit the Belgium capital!  Check out the peloton entering the city (click on image for a larger view).

Looks amazing!  Cyclist will stay in Brussels for tomorrow's 27.6-km (17.1-mi) team time trial.  I love watching team time trials.  Team strategies will be on full display as riders swap drafting positions.  Lots of great physics!  Below is our prediction for the second stage.

• Stage 02:  29' 41" (prediction)

I hope our prediction is a little better than today's, but a record-setting time could have us too slow again.  We shall see!

It's Tour de France Time!

On the eve of the world's most famous bicycle race, I am once again geared up to post my research team's predictions for the Tour de France's stage-winning times.   We model elite cycling using published values of cyclist power output, air drag, tire/road friction, terrain data, and, of course, the laws of physics that constrain us all.  This year's race looks to dazzle those of us who love watching battles in the high mountains.

Stage 1 commences in the Belgian capital of Brussels.  The 194.5-km (120.9-mi) flat stage takes riders west, then south of Brussels, before returning north back into Brussels.  Our prediction for the first stage's winning time is given below.

• Stage 01:  4h 32' 00" (prediction)

My research students here at the University of Lynchburg are Carl Pilat, who worked with me last summer, and Noah Baumgartner, who joined my research team this summer.

As I sports physicist, I want to understand how elite athletes are able to do what they do.  I also want to understand the equipment and playing surfaces they use.  Modeling the Tour de France is about taking something extremely complicated and simplifying it enough that one begins to understand it on a fundamental level.  Sticking our necks out and posting stage-winning times is merely our way of spicing up what we do.  We can never fully know weather conditions, and we're not privy to the various strategies employed by the cycling teams.  And we certainly can't know ahead of time if there will be crashes, delays, protests by fans, interference by fans, cows roaming onto the road, and so on.  Those aren't excuses for bad predictions, just the reality of trying to model something so complex.  We love it when a prediction is nearly spot on, and when our predictions don't fare so well, we are given an opportunity to learn something.  That's one reason why being a scientist is such a delight!

Ready for the Women's World Cup?!?

The Women's World Cup begins on Friday, 7 June.  I'm excited to see the world's best go for glory in France!  My country will compete in Group F with Chile, Sweden, and Thailand.  The ball the players will use is the adidas Conext 19.  The panel design is exactly the same as the Telstar 18 ball that was used in the Men's World Cup last summer in Russia.  The color scheme, however, is quite different.  The color scheme pays homage to the ball that helped host France win the Men's World Cup in 1998.  That was the adidas Tricolore.

My colleagues at the University of Tsukuba in Japan, Takeshi Asai and Sungchan Hong, have been great collaborators for me.  We've published a few papers on soccer ball aerodynamics, including papers on the balls used in the past three men's Worlds Cup.  They sent me wind-tunnel data for the Conext 19.  The data look very similar to what we published for Telstar 18 (click here for our paper).  The graph below shows the drag coefficient as a function of ball speed (air speed in the wind tunnel).

I've labeled the so-called "critical speed" in green.  That's the speed at which air flow around the ball transitions from laminar below the critical speed to turbulent above the critical speed.  The critical speed above is at a great speed!  Most of the high-speed corner and free kicks will take place at speeds above that critical speed.  That means the players will deal with a ball in flight whose drag coefficient won't change much.

For balls hit with little to no spin, knuckling effects will play a role.  The graph below shows side and lift coefficients for the Conext 19.

Even though the ball wasn't spinning in my colleagues' wind tunnel, the boundary layer of air still separates asymmetrically off the back of the ball.  That's due to the fact that the seam pattern does not preserve spherical symmetry.  Air might separate off the ball near a seam on one side, but near a panel on the other side.  The large fluctuations at small speeds won't be noticed much by players because the side and lift forces are large compared to the ball's weight at those speeds.  For high speeds, kicked balls with little to no spin will wobble a little.  Lateral deflections could reach 6% of the ball's horizontal range on hard kicked balls.

My colleagues have wonderful facilities for testing soccer balls.  They sent me a video that I posted last year when media were contacting me about the Telstar 18 ball.  I'll show the video again below.

Ain't physics grand?!?  Now bring on the Women's World Cup!

Cover for my new book is out!

My second book, The Physics of Krav Maga, is due out this November.  It will be available just in time for holiday shopping!  😃  I now know what the cover looks like.

I wish I could say I am on the front cover, but my body isn't quite cut like the body on one of those guys!  Click here for my book's Amazon page; click here for my book's page with my publisher (Johns Hopkins University Press).  I look forward to the fall season when my book is released.  It will be fun talking about all the great physics in Krav Maga!

Super Bowl LIII Physics

I've heard many say that Super Bowl LIII wasn't very exciting.  Well ... a defensive battle can be just as exciting as an offensive shootout.  A tied Super Bowl more than halfway into the 4th quarter is exciting, no matter what the score is.  The New England Patriots beat the Los Angeles Rams, 13-3.  As much fun as I had watching the game, I had a tiny bit more fun looking at all the wonderful physics in the game.  I was only able to grab some screen captures, so the images I have below aren't the best quality.  But I'll make a few physics observations from last night's game.

The very first play of the game had me thinking about center of mass.  Sony Michel (#26) ran for 13 yards.  What made his run is that after he took a hit near the line of scrimmage, he managed to keep his center of mass over his base.  Check out the screen capture of his run (click on image for a larger view).

Knowing how to keep his center of mass from getting past his shoes, Michel was able to maintain his balance and pick up the game's first 1st down.

The Rams were feeling good a few plays later when they picked off Tom Brady (#12).  Check out the ball in the air after the tip (click on image for a larger view).

An "impulse" is needed to change an object's momentum.  The physics way of thinking of impulse is to imagine the force on an object multiplied by a collision time.  The football received an impulse from Rams cornerback Nickell Robey-Coleman (#23) that redirected the ball's momentum upward.  That allowed Corey Littleton (#58) to make the pick.

Super Bowl MVP Julian Edelman (#11) likely saved himself from sustaining a concussion early in the 3rd quarter.  When Rams free satety Lamarcus Joyner (#20) laid a hard hit on him, Edelman just managed to tuck his head, which prevented a helmet-to-helmet collision.  Check out how close Edelman came to perhaps not competing in much of the rest of the game (click on image for a larger view).

If you click on the above image, you'll see Edelman's helmet just under Joyner's helmet.  Part of good practice involves learning how to get hit, and staying in one piece.

When I saw Rams quarterback Jared Goff (#16) get hit near the end of the 3rd quarter, I was reminded again about how forces add.  Check out Goff getting smashed (click on image for a larger view).

He was getting sandwiched by three Patriots!  Although he was ultimately pushed backwards, Goff experienced a brief moment of no net force.  If the three Patriots exerted forces that add -- as vectors -- to zero, Goff would have had no net force on him.  Of course, getting squashed in a Death Star trash compacter still hurts, even if one's center of mass isn't going anywhere!

At the very end of the 3rd quarter, I saw Sony Michel get hit by Rams defensive tackle Michael Brockers (#90), and like the first play of the game, a run by Michel had me thinking about center of mass.  Check out the hit (click on image for a larger view).

See #90 of the Rams?  He's hitting Michel right at Michel's center of mass!  That didn't cause Michel to rotate for a tackle.  Instead, Michel bounced off Brockers for a 19-yard gain.  The action is incredibly fast on the gridiron, but good fundamentals mean the difference between getting stopped for a 5-yard gain and picking up 19 yards.

Early in the 4th quarter, I saw Jared Goff get hit by Patriots cornerback Jonathan Jones (#31).  But it was only a flash because Jones came flying from the right side of the action and tagged Goff hard just before the Rams quarterback got out of bounds (click on image for a larger view).

The reason Jones looks like a blur in the above image is that he was moving over 15 mph when he closed on Goff.  That was a cornerback who didn't want the opposing quarterback to get back to the line of scrimmage!

Many commentators have lauded the throw Brady made to tight end Rob Gronkowski (#87) that put the Patriots in position to win the game.  I grabbed the screen capture below (click on image for a larger view).

That ball traveled 33 yards in the air and took 1.93 seconds to go from Brady's hand to Gronk's hands.  But look at the tiny window Brady had to make that completion!  Two Rams defenders are behind Gronk, screening him from Brady's sight.  One of those Rams defender is blanketed on Gronk.  A third Rams defender is closing in on the play.  That throw won the Patriots the Super Bowl.  There is a reason Tom Brady is the GOAT!

The Patriots finished off the Rams with a field goal by Stephen Gostkowski (#3) with just over a minute left in the game.  Look how close the ball came to hitting the left upright (click on image for a larger view).

You can just see the ball about a quarter of the way down along the inside of the left upright.  The Coriolis effect didn't make the difference in the kick, but it was pushing the ball in the right direction.  In the northern hemisphere, projectiles, like footballs, get a tiny push to right.  But because the ball was only in the air 2.3 seconds before it crossed the plane of the uprights, the Coriolis push was less than a quarter of an inch.  But if you're not a Patriots fan, it stinks knowing that even Earth was trying to help that kick!

A nerd like me loves watching sports.  But what makes the experience even more fun is seeing the sports world through the eyes of a physicist.