Running the Boston Marathon is tough enough without having to jostle your way from Hopkinton to Copley Square. So race organizers this year turned to an expert in crowd science to help them manage the field of more than 32,000 as it travels the 26.2 miles (42.195 kilometers) through eight Massachusetts cities and towns. Marcel Altenburg is a lecturer at Manchester Metropolitan University in Britain. His specialty is helping mass events run smoothly. He said his main goal is protecting what makes the Boston Marathon special.