Timing is everything, especially at the 2012 Summer Olympics where even a millisecond could mean the difference between victory and defeat. Linda Milor, an electrical engineer at Georgia Institute of Technology, explains why Olympic timekeeping technology must be able to measure an athlete's performance with both accuracy and precision. ʺScience of the Summer Olympicsʺ is a 10-part video series produced in partnership with the National Science Foundation.

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LIAM McHUGH, reporting: In 1996 it was Gail Devers in the women's 100-meter sprint. In 2008 it was Michael Phelps in the men's 100-meter butterfly. Two different races, two different sports, both won by less time than it takes to blink.

Announcer: One one-hundredth of a second! The look on his face tells it all!

McHUGH: At the 2012 Summer Olympics in London, timed events will be measured to one one-thousandth of a second - one millisecond - and that requires a high-tech timekeeping system built with cameras, lasers, computers and very accurate clocks.

LINDA MILOR (Georgia Institute of Technology): Right now, we are working with clocks that do calculations faster and faster and faster than we ever did before. And the accuracy of today's timing circuitry is a thousandth of a second. So it's one hundred times more accurate than a stopwatch.

McHUGH: Linda Milor is a professor of electrical engineering at Georgia Institute of Technology and has been funded by the National Science Foundation. Milor says that to be reliable, a timekeeping system must implement two key engineering principles: accuracy and precision. For accuracy, think of a clock that is close to the true, or real, time it took a runner to go from start to finish. For precision, think of the same clock, except now it's off by a few milliseconds. The times it registers are inaccurate, but it's always off by the same few milliseconds.

MILOR: Precision means that you get the same measurement all the time, over and over again, as you make the measurements.

McHUGH: For a clock to be both precise and accurate, it must give measurements that are very close to the actual time and also give those measurements again and again.

MILOR: It's incredibly important, because the level of accuracy that's required is in the hundredths to thousandths of seconds. Those levels of measurements require a very, very high level of precision and a very, very high level of accuracy.

McHUGH: To make timekeeping more accurate and precise, engineers use technology to remove the possibility of error. In track events, an electronic pistol starts the race. Speakers behind the starting blocks allow each runner to hear the gun at the same time. When the trigger is pulled, the system sends an electronic pulse to the timing device, which starts the timer and calculates the response time of each athlete, using sensors that are built into the blocks. If a runner applies pressure in under 100 milliseconds, faster than any human can react, the system signals a “false start”— meaning the runner was anticipating the sound rather than reacting to the sound – and the race is stopped. 

Announcer: Another false start.

McHUGH: At the finish line, runners interrupt a laser beam, and their time is recorded, while a high-tech camera records more than 2,000 digital images per second. Almost immediately, the images are put together by the computer into a composite of all the athletes, along with a scale indicating the elapsed race time. The space on the image represents the time between the runners as they crossed the finish line, giving judges a picture of the finish.

MILOR: So these cameras allow us to get an image and show the result much more quickly than we used to in the past.

McHUGH: In swimming events, the start blocks also measure reaction times. But at the finish, the athletes stop their own timer by touching pressure-sensitive pads that cover the end of each lane.

MILOR: Essentially, it's a mechanical problem that has to convert to electrical problem, which is challenging.

McHUGH: High-definition video cameras above and below the water also record the finish …

Announcer: Here comes Lezak! Unbelievable at the end! He’s done it!

McHUGH: …taking 100 pictures per second from different angles for judges to examine in a close contest. For longer races, like marathons and road cycling, where dozens of athletes compete at the same time, radio frequency identification, or RFID, is used to time the athletes from start to finish.

MILOR: They're the next generation of the barcode that you have in the supermarket for all your items.

McHUGH: These small electronic transponders, or tags, are attached to the athlete's bike frame or shoe. The tags transmit the athlete's identification to antennas set up along the course to track each athlete's performance in real time during the race.

MILOR: The detector will then identify which tag it saw. And because we have very fast electronics, it can do many different tags, almost at the same time.

McHUGH: With more than 3,000 athletes in 300 events at the 2012 Games in London, it will take timekeeping technology that is both accurate and precise to place the right athletes on the medal stands.