BASE (also B.A.S.E.) jumping is a sport in which people jump from stationary objects with the use of a parachute.It is an acronym for building, antenna, span and Earth – the four categories of objects that can serve as platforms for a jump. Those who make at least one jump from each of these four categories are awarded BASE numbers.

The term was coined by Carl Boenish, a filmmaker, his wife and friends.

The sport is evolved from skydiving although the jumps are made from a significantly lower altitude. In addition, the jumps occur close to the platform from which the jump is made.

As a result of the lower altitude, BASE jumps involve slower airspeeds than skydiving so terminal velocity is not always obtained by the jumper. For example, a jumper falls at around 55m/s (190km/h, 12 mph) from an altitude of 600m (2,000 feet) with a minimum 300m (1,000 feet) freefall.

The jumper is around 10.9 seconds from the ground and most of these jumps are made from less than 600m. To compare this to skydiving, a skydiver parachutes for around 3 minutes after deploying his parachute while a BASE jump from 150m (500 feet) is only a 10-15 second parachute ride since the jumper is only about 5.6 seconds from the ground when remaining in free fall. Bridge Day takes place annual on the third Saturday in October with permission granted for BASE jumps to take place the New River Gorge Bridge in Fayetteville, West Virginia. The deck of this bridge stands at 297m (876 feet) above the river’s surface. Approximately 450 BASE jumpers and 200,000 viewers attend this event each year. Weather permitting, over 1,100 jumps can take place in the six hour window in which this bridge is legally opened for jumps. Skydivers who are novice BASE jumpers typically jump from this fixed object alone.

Another type of jump is the jump from tall structures while attached to an elastic cord of bungee jumping. The jump is usually made from a fixed object although. It is also possible to be done from helicopters or similar objects that are able to hover while the jump is made. Many jumpers still use the factory-made braided shock elastic cord that has been used since bungee jumping was first popularized. The cord is made of numerous pieces of latex that are encased in a thick cover for added strength and durability. The latex is often pre-stressed when this cover is applied as this ensure that the cord is resistant to extension when it is at it’s full, extended length and under pressure. This also serves to provide a sharper bounce when the cord retraces and makes the cord significantly more durable. South-hemisphere operators like A.J. Hackett use cords that are not braided and have visible strands of latex as they can be made at home and provide a lengthened and softer bounce in contrast to the sharper bounce. Since 1980, there are been several million jumps that have been successful and the safety records of operators is the results of strict standards and guidelines for operating jumps. These include confirming fittings and calculations for every single jump that is made as no two jumps are the same. However, accidents do occur in bungee jumping just like in any sport and there have been some injuries and deaths. Fatalities are usually the result of cords that are too long; it is essential that the cord can be shorter than the height of the platform as room is needed for its extension in the jump.  Tension is required in the cord, which increases as the rope stretches. With the downward acceleration and weight of the jumper, the cord eventually reaches a point where the tension of the cord is greater than that of the jumper’s combined weight and acceleration. This is what enables the cord to retract and cause the “bounce” that brings the jumper upward and away from harm.