10. IE • An astronaut in a spacecraft moves past a field 100 m long (according to a person standing on the field) and parallel to the field’s length at a speed of 0.75c.

(a) Will the length of the field, according to the astronaut, be (1) longer than 100 m, (2) equal to 100 m, or (3) shorter than 100 m? Why?

(b) What is the length as measured by the astronaut?

(c) Which length is the proper length?