Theories developed by scientists like Newton and Einstein have always been challenged by researchers. We cannot say that these theories are always false since their accuracy has been proved many times. Now NASA is funding the development of lasers that can be deployed on the Moon to check for the subtle deviations from the standard theory of gravity.
NASA had installed three laser reflectors on the surface of Moon during the Apollo missions. These have been used to measure the exact distance between the Earth and the Moon, moreover the Soviet Union had also attached a reflector to a robotic lunar lander launched by them.
To know the distance between Earth and Moon scientists bounce laser light from Earth to the Moon and then wait from it to be reflected from the Moon and reach back to Earth. The time taken in the transit tells about the distance from the Moon.
This approach is not as easy as it seems to be, the biggest problem in this approach is that lasers lose their strength on the distance from Earth to Moon and they are further weakened on the way back. When the laser is received at Earth it is so feeble that only three observatories on Earth have the equipment to trace it.
Moreover, since the Moon is controlled solely by the gravity of Earth these measurements can also find the variations in the standard theory of Gravity and Einstein’s general theory of relativity. Some theories particularly the String Theory shows some deviations form Einstein’s theory of relativity. Other theories also say that the Gravitational Constant (G) is not actually is constant and it varies with time. These changes are too small to be easily detected but measuring the accurate distance between Earth and Moon can give a precise description of that.
Till now we are not able to get the precise distance since the reflected light is too weak for that. To sort out this problem NASA is funding the development of better quality devices that give a better signal than the currently employed devices. Slava Turyshev of NASA’s Jet Propulsion Laboratory in California wants to put a more sophisticated device on the Moon. There proposed model is a laser transponder, this device will detect an incoming laser signal from the Earth and instead of just simply reflecting this incoming laser it will fire a new laser in the direction from which the incoming laser arrives. This means that there will be less power loss and the signal received on Earth will not be as weak as it is with the current technology. Better signal also means that it can be detected by more observatories on Earth. They also hope to develop a suitcase sized transponder that can easily be carried to the Moon along with the next manned mission.
NASA also wants to replace the current reflectors since they have suffered degradation during their thirty years service time. Cosmic dust has accumulated on their surfaces, which has decreased their output.
Via: Newscientist
