Spaces least resistance is in a straight line over the surface of a mass this is why it is always pulling. It is trying to achive a straight line inertial flow. When a mass is traveling in a straight line at a constant speed space will open in front of it and close behind it at the same rate this is why in space it keeps going at the same speed unless it comes in contact with another masses space field. Space is like a ocean that surrounds all mass. But unlike an ocean the planets and solar systems and galaxies are coupled to each other through this field.
Planets orbit their stars because of the space coupling within the planets and their stars.
Solar systems are coupled to each other because they have a more dense space field with in them because of the combined coupling effect of all the planets. This is why they are able to be coupled to other solar systems. All the solar systems combined create the dense space field of our galaxy. Which is coupled to other galaxies. Also the reason clocks run faster in space than on earth is because space is not a dense outside of the earth.