Necessity is the mother of invention. So all the invention or discovery is based on necessity. But if we find any invention which is not directly based on any real necessity then it should take some more importance. Among them we get N dimensional geometry,black hole,zero point energy and also time machine.But among the following list the time machine has a greater impact to the humanity, to the human mind .In all the ages man think of time machine.Actually if we can ready any device or gadget it could travel in past and future it will solve many problems.Even it will equalise all the inequality in the socity.It may fulfil all the lusting.But if we can make any time machine the journy will not be the reflection of H.G.Wells "Time Machine". After starting the machine the driver can control it the future direction but cant control it in the past after reaching its origin.If the driver can try to control it aftr reaching
its origin it may cause grand mother paradox.So the time itself would be the driver .So it is generated by mankind directly or indiectly,but the controller will be no man rather a natural power time.So it will be the greatest invention forever.