More concerned about her carbohydrate intake than her schoolwork, Miriam R. Asnes '02 worries that Passover observation has interfered with her preparation for the 105th annual Boston Marathon.

At noon today, Asnes and handfuls of other Harvard students will join 15,000 registered runners and a few thousand unofficial participants for one of the most famous and most challenging long runs.

One of the largest single-day sporting event after the Super Bowl, the Boston Marathon has a reputation for its unpredictable weather and 26.2 miles of hilly terrain. Registered runners have qualified by running other marathons with times of less than three hours and ten minutes for men and three hours and 40 minutes for women.

For each of the 26.2 miles ahead, these athletes will run at roughly a seven mile per hour clip, beginning their journey in the small town of Hopkinton and finishing in Copley Square.

Throughout the race, official runners will have their pace monitored by chips installed in their shoes. At the finish line, volunteers will meet them with a warm blanket and a bronze participant medal.

The Boston Marathon is a tremendously difficult course. Runners must brave the four hills of Newton during the most mentally trying portion for runners, miles 16 to 21.

The notorious Heartbreak Hill gets its name from the one-mile stretch where each year runners simply hit the wall and may actually stop running.

"Boston has a lot of hills," Kirkland House Allston Burr Senior Tutor Timothy C. Harte '90 said. "But with the uphill you need to go downhill. The pounding of the downhills are difficult to deal with."