The above-water photos Saletan cites are not as clear as the below-water ones published in Sports Illustrated (<link>). In the fifth photo of the series, you can clearly see the fingers on Phelps' hright and being significantly bent, while to me it looks as if Cavic is still about a centimeter away with his right hand, and it's a little hard to see on his left hand (the sixth photo is a zoom picture of Cavic's hands), but I think it still hasn't touched. Of course, one has to be careful because on a forceful finish like Phelps had the fingers will bend more than on a slow, gliding finish, but as best as I can tell it still looks like Phelps won.

Also, bear in mind that in this event, the swimmers' speeds were about 2.0 meters per second, so a 0.01 second difference in time would corresponds to about a 2 cm difference in distance at the finish. (This is just a ballpark estimate using a 100 m distance swum in about 50 seconds; in reality there are accelerations at the start and turn that affect the estimate of the swimming speed, and obviously the actual arm speed at the finish can vary by a lot depending on the type of finish.) I don't believe that Saletan can distinguish that difference with his eyes from any shot other than the underwater slow motion. In the same vein as his Human Nature articles I would say that his eyes (or rather, brain) deceived him by making a projection forward in time and space based on the previous time history of the swim, whereas in reality his eyes and brain were not good enough to resolve the difference at the actual moment of finish.

One interesting point about the race, given the asymmetrical touch by Phelps (his left fingers are bent "long" before his right ones) -- in butterfly, one must touch the wall simultaneously with both hands in order to avoid disqualification. Given that no one will ever touch the wall with both hands exactly simultaneously, how close in time do the hands have to touch in order to avoid disqualification? The timer pad does not record this (as far as I know). What if Phelps touched with one hand, then Cavic touched with both his hands, and then Phelps touched with his other hand, all wihtin about 0.01 second? Should that count as a tie?

Also, what are the actual rules of swimming? Is the official time linked to the time the sensor registers the touch, or can it be overuled by photo evidence showing that one swimmer's fingers touched before another's but did not trigger the sensor? It's possible that the photo evidence is taken just in case there is a timer malfunction and the timer data cannot be used officially. After all, the high-speed photo evidence is not used to resolve ties that were recorded within 0.01 second.

Finally, pages and pages of journalistic ink have been spilled over the Phelps-Cavic finish, but no one comments about the Lauterstein-Crocker finish in the same race where Crocker lost the bronze medal by 0.01 second. Let's look at that one in slow motion too, so we can get used to seeing what a 0.01 finish looks like. How about the Steffen-Torres finish in the 50 m freestyle where Torres lost the gold by 0.01 second after Steffen came from behind? How about the Lezak-Filho tie (within 0.01 second) for bronze in the 100 me freestyle? I'll bet that there are at least a few other close races out there where the eyes play tricks on you when viewing in real time from over the water. No matter how many times I see that Phelps-Cavic race in real time from the side, I always think Cavic won. But the timing result and the slow motion underwater photopgraphy convinced me otherwise -- I would have said Cavic beat Phelps by at least 10 cm and maybe more based on the real-time footage, but obviously the race was a lot closer than that.

Sorry, I missed the paragraph in Saletan's article that quoted the FINA officials -- apparently the official time is off of the sensor trigger. I don't understand what Saletan's problem is. The rules say you have to trigger the sensor, so if a swimmer finishes in a way that guarantees a slow trigger, then that's the swimmer's fault. They know the rules. If a pole vaulter clears the bar but touches it hard enough to make it fall, the pole vaulter loses. No one whines (I hope) that the pole vaulter really should have won because he or she actually jumped the highest. The pole vaulter didn't have a clean clearance, and if Cavic lost solely because of the sensor pressure threshold (and I don't think he did), then it's because he didn't have a clean finish.

One more comment -- I imagine most swimmers start their race off of the "beep" rather than off of the strobe or the motion of other swimmers. Given that the speed of sound is 343 m/s (or 3.43 m per 0.01 s), and that the path difference between the starter and the swimmer may differ by a few meters from swimmer to swimmer, that could make a difference on the order of 0.01 second in time. Should we correct swimmer's times for path difference? Same for track runners. I would say that again, it's all part of the game, just like some lanes are more desirable than others.

Saletan:

It does look to me like the best way of settling it is that blown-up underwater photo, combined with digital analysis of the lateral stripe on the wall. If you can identify the respective altitudes of Cavic's hand and the stripe, you can mathematically ascertain whether his finger is touching.

It's a little difficult because you can't get complete perspective from the photo. It would be different if the perspective were exactly from below or to the side and you could see a gap between the fingers and the wall, or if you could see a good shadow of the fingers on the wall. It really looks to me, however, that Cavic hasn't finished yet (by about 1 cm) in the photo where Phelps' fingers are bent against the wall.

Saletan:

It does look to me like the best way of settling it is that blown-up underwater photo, combined with digital analysis of the lateral stripe on the wall. If you can identify the respective altitudes of Cavic's hand and the stripe, you can mathematically ascertain whether his finger is touching.

I don't know if anyone on this thread has ever used a swimming lane touchpad before, but this whole conversation seems a little over played. These are the same pads that 8 year old swimmers touch with plenty of force to register as 'finished,' I doubt an Olympian in his 20's who is putting in the 3rd (or 2nd if you want to go with Mr. Saletan) fastest 100 m butterfly time is unable to register enough force press the pad together once he gets to the wall.

Other clear indications of the non controversy status of this finish: the swimming world only gets this type of attention every 4 years and would love to be able to extend it, yet I haven't read a single article arguing this same premise. Not even by any of the prominent Serbian coaches out there. And the Serbian team removed its protest of the results almost immediately after seeing the si photos.

arbitrary:

I wasn't a great swimmer, but I swam in college and was in competitive swimming for 15 years. You use the flash as well...that's why there is constant announcements at any sizable meet not to use flash photography at the start.

I know they have a flash -- I just suspected that most swimmers start off the beep.

Saletan:

It does look to me like the best way of settling it is that blown-up underwater photo, combined with digital analysis of the lateral stripe on the wall. If you can identify the respective altitudes of Cavic's hand and the stripe, you can mathematically ascertain whether his finger is touching.

By the way, I'm not convinced that this method would actually be more accurate at determining whose fingertips touched first than the touchpads. Even in a glide I would think that those touchpads trigger pretty quickly.

I also agree with the other posters -- recording wins off of touchpad triggers seems to be as good as method as any, as long as everyone knows the rules and the touchpads are properly calibrated against each other.

arbitrary:

I don't know if anyone on this thread has ever used a swimming lane touchpad before, but this whole conversation seems a little over played. These are the same pads that 8 year old swimmers touch with plenty of force to register as 'finished,' I doubt an Olympian in his 20's who is putting in the 3rd (or 2nd if you want to go with Mr. Saletan) fastest 100 m butterfly time is unable to register enough force press the pad together once he gets to the wall.

Saletan's point, as I understood it, was not whether or not the swimmer finishes hard enough to register (obviously Cavic did this), but how long it takes to register after different types of finishes. I would guess, however, that even a gliding touch would register in less than 0.01 seconds.

Ketone:

arbitrary:

I don't know if anyone on this thread has ever used a swimming lane touchpad before, but this whole conversation seems a little over played. These are the same pads that 8 year old swimmers touch with plenty of force to register as 'finished,' I doubt an Olympian in his 20's who is putting in the 3rd (or 2nd if you want to go with Mr. Saletan) fastest 100 m butterfly time is unable to register enough force press the pad together once he gets to the wall.

Saletan's point, as I understood it, was not whether or not the swimmer finishes hard enough to register (obviously Cavic did this), but how long it takes to register after different types of finishes. I would guess, however, that even a gliding touch would register in less than 0.01 seconds.

The pad is about 2 inches thick....the distance between the conductive surfaces inside the pad is perhaps a quarter of an inch. The distance would take someone moving at the speed of Phelps or Cavic about .003 second to traverse.

The touchpad is electronic--it sees no difference between a gliding touch and a powerful touch such as Phelps used. As long as the threshold for touch pressure is reached, all touchpads will respond with the exact same accuracy. A touchpad does not "record more slowly." It either stops the time or it doesn't (I've swum in more than one meet where a judge has to reach down and slap the pad after the race because the swimmer failed to touch it hard enough and that lane's clock was still running). Cavic's time stopped, indicating that he sustained enough force in his finish to have his time accurately recorded. So, even if the touchpads were .001 seconds behind the actual touch, the same .001 seconds get added to Phelp's time that they were to Cavic's.

Rapunzal:

The touchpad is electronic--it sees no difference between a gliding touch and a powerful touch such as Phelps used. As long as the threshold for touch pressure is reached, all touchpads will respond with the exact same accuracy. A touchpad does not "record more slowly." It either stops the time or it doesn't (I've swum in more than one meet where a judge has to reach down and slap the pad after the race because the swimmer failed to touch it hard enough and that lane's clock was still running). Cavic's time stopped, indicating that he sustained enough force in his finish to have his time accurately recorded. So, even if the touchpads were .001 seconds behind the actual touch, the same .001 seconds get added to Phelp's time that they were to Cavic's.

Not that I want to get in the position of defending Saletan, but this makes no sense from a physics perspective. The pads work by the swimmer pushing one surface in contact with another, and that process obviously takes some non-zero amount of time, given that the force exerted on the pad is not infinite. It will take longer to trigger a sensor with a higher pressure threshold than a lower one, given the same amount of force in the touch. Of course, the end result is that the sensor either gets triggered or not triggered, but if it is triggered, the delay between the actual physical touch and the trigger will probably not be perceptible to the swimmer. This delay depends on the force profile of the touch. On top of that, there will be an electronics delay that will hopefully be uniform from swimmer to swimmer.

So, the real question is what is the length of the delay, which arbitrary has estimated in the previous post, and more specifically, what is the difference between delays when triggering a sensor with a gliding touch versus a forceful touch. The answer, I suspect, is far less than 0.01 second.

The problem with Saletan is that he wrote a whole article about the effects of the delay without understanding exactly how long the delay was. In his mind, Cavic won because his eyes told him so, and so he went looking for explanations. Since he knew there was a delay between touch and sensor trigger, and since he's a contrarian, he suggested that delay as a possible explanation -- without having any understanding of whether that would be a significant effect. The irony is that he started out not believing in the Phelps win because of what his eyes told him, but the time difference he proposes due to the touch trigger delay would almost certainly be smaller than his eyes can perceive. He didn't look first at the more simple explanation -- that his eyes deceived him. His eyes told him that Cavic won, but unfortunately the eyes are only good enough to resolve a difference of a few hundredths of a second at best in an overwater television shot. So, the difference he proposes would have to be on the order of at least a couple hundredths of a second, which is hard for me to believe.