It appears strange but true that astronauts can walk in the space. This is so because in ordinary walking, we rest our feet on the surface of the Earth and the force of Earth’s gravity pulls us towards it. But when there is nothing in the empty space — neither any surface to walk on nor any gravitational force to pull the feet down on to the ground — how does an astronaut walk in the space? Space walking by astronauts is quite different from the normal walking. To walk in the space, the astronauts take the help of hand rockets which provide them the force to move. The hand rockets follow the principle of rocket propulsion. In rockets, the ejection of gas with a great force from the backside pushes the rocket forward with an equal thrust. This working principle is based on Newton’s third law of motion which states, ‘To every action there is always an equal and opposite reaction’. Similarly in hand rockets when the engine is powered, the exhaust thrust pushes the rocket in the opposite direction and the astronaut walks along with this force as he carries the hand rocket with him. In fact, it is not ‘walking’ in the strict sense, as there is no surface in the space to rest the feet but rather ‘floating’—to express more accurately. But why do the astronauts walk in the space? Apart from experimental reasons, sometimes they are required to shift from one spacecraft to another or need to carry out a repairing work on the outer surface of the craft. During such operations, they use the specially designed hand rockets and the direction of the exhaust outlet is pointed opposite to the desired direction of walking. The first spacewalk was made in March 1965 by a Soviet astronaut, A. Leonov, who stayed outside the aircraft for 24 minutes. Another important walk was made in 1973 when the American satellite skylab was to be repaired for a damage in the heat shield that made the craft dangerously hot. Indo-American astronaut Sunita Williams ran in Baston Marathon on April 15, 2007 at over 18000 miles per hour. She completed the 26.2 mile marathon strapped on her treadmill aboard the international space station in 4 hours and 24 minutes.