World Jump Day was a hoax global flash mob event scheduled for July 20, 2006 at 11:39.13 UTC, at which time the organization claimed to have 600 million people from the western hemisphere jump simultaneously. They claimed this would move the Earth out of its orbit, and into a new one, one that would not cause global warming. The site was an art installation by Torsten Lauschmann (claiming to be a Professor Hans Peter Niesward from the Institute for Gravitational Physics in Munich), and in no way serious. Still, it was probably the largest (and first?) worldwide flash mob project ever, although by including only the western hemisphere it can not claim to be truly worldwide.
Origins and Participation
According to DNS lookup information, the site http://www.worldjumpday.org
is hosted in UK, on http://uk2.net/
. Before that, it was registered to Torsten Lauschmann. Lauschman is a German artist currently living in Glasgow. His website, http://www.lauschmann.com
, links to the World Jump Day website and a tour where he travelled under the name "Slender Whiteman" (http://www.slenderwhiteman.com
This hoax has been put forth in the "media" before, as an item in the Weekly World News in 1993, according to this link http://www.subgenius.com/subg-digest/v4/0069.html
The counter for the site, measuring registered jumpers, was also fake. It seemed to go both up and down. For a point of reference, at 21:37 on 18th July 2006, it was at 598,196,296 but just 15 minutes later it had dropped to around 598,106,000.  Less than 12 hours before the event the site's counter read that there were 600,256,820 registered jumpers, almost 50% of all internet users.
Even if it were to be taken seriously, World Jump Day's claim was completely unscientific and was widely discredited. There are a number of reasons to reject the thesis:
* It is impossible to permanently change the Earth's orbit using the planet's own mass (which includes that of the world's population) unless such mass is ejected from the Earth at escape velocity (see Newton's third law of motion). The center of gravity of the system containing the earth and its population of humans will remain in the exact same orbit it was always in throughout the jump. However, for the very brief moment when the jumpers were in the air, the Earth's orbit would have been moved a tiny bit - only to be restored to its exact same location by the force of gravity acting between the jumpers and the planet while they were in the air.
* Even ejecting such mass from the Earth (or colliding to it from outer space), the resulting energy would be equivalent to only 2% of the energy released by a modern hydrogen bomb, shifting the Earth's orbit just a small fraction of the radius of a single atom .
* Since the Earth's orbit is elliptic, there are already great variations in its distance from the Sun (about 5,000,000 km) with no generally noticeable changes in temperature. Applying a brief force to the surface of the earth would not move its orbit further from the sun - it would merely change the shape of the ellipse - so at some times of year the earth would actually be closer to the sun whilst at others it would be further away.
* A simplistic way of showing that you cannot change the earth's orbit with more people jumping: If the population of the earth massed the same as the Earth without its population, and the population jumped upwards at 1 m/sec (which we will assume is less than escape velocity), Newton's third law would cause the earth to move down at 1m/sec. The gravity between the people and the earth would then suck the people and the earth together again at 1m/sec. They would then collide, and cancel each other's momentum, having no net effect, except possibly causing an earthquake, which would have no effect on the earth's orbit. This is an extreme example, but demonstrates the basic principles of why such a jump would not work.
The World Jump Day website gave the jump time as 11:39:13 GMT, but the countdown on the same site was (as of May 6 2006) counting down to 10:39:13 GMT. There seemed to have been a confusion between the GMT or UTC time and the UK legal time 11:39:13 which takes into account daylight savings time. Recently the countdown was adjusted to reach zero at 11:39:13 GMT.
* As of 11:47 GMT, the project seems to have failed and was in no way serious.
* At 11:20 GMT, the website server crashed; although it is now back online, the results of the jump will not be published for a few days, according to the website.