Gravitational Fields
A gravitational field is a force that pulls things with a smaller mass towards something with a larger mass. The larger an objects mass is the stronger the gravitational field is. Small objects have a weak gravitational field and large objects have a strong gravitational field. Smaller objects are more attracted to a gravitational field then larger ones. The strength of the gravitational field is also affected by proximity, the closer something is the more it is affected by a gravitational field.
The scale for a gravitational field is very large. Even the largest man made objects do not have a strong enough gravitational field to pull an object towards it. The smallest object that can keep an object on it is Deimos, the smallest of Mars' moons. A person could jump off it if you ran at 12.5mph and if it was large enough to run on. Deimos is 8 miles across, in comparison the Earth is 3,959 miles across and Earth's moon is 1,079 miles across. Even Pluto, which is no longer considered a planet is 738.4 miles. the largest man made object is the Three Gorges Dam in China, which is a mile and a half, not even close to the size required to pull an object towards it.