Space is formless. Time is form. Air, Ether, planets all can be considered as space. Avatara or Incarnations are representations of time. Now we are living within the boundaries of Time. Various forms, avatars, human beings, animal systems WITH life, are measured by Time. Paramatma is space. We cannot see Paramatma, similarly, we cannot see space. Space is only experienced in Dhyana or meditation. The only planet or form we can refer to is called Time.
If we have to talk in human terms we can simply say form and formless. What is limitless is Space (Akasha). The entire Brahmanda exists, but cannot be perceived by our eyes. There are so many stars, but we cannot see. It is that far away in space.
When you have to go to Ontikoppal (a small town near Mysore), you can go by car, or by bus or walk to the place. It will take you some time to get there. But we can think of Ontikoppal while still sitting here. But your mind travels there! Time is associated with body. To reach the place it takes time. Another name for Time is Karma. This is called Karma Siddhantha (philosophy).
Space has no form as it has no Karma. Who is the one without any Karma? Only the supreme Almighty, Paramatma, is without Karma! But He will also take upon Karma, when He takes form. To merge in Space, we must give up all Karma. Rama said, “I’m going to Sarayu River and will go to Vaikuntha then.” Why did He have to mention Sarayu River? He took form and incarnated in Time and when Time was up, He gave up His form and merged in space. Just to go to Mars, it takes so many months. Can the life withstand that region? Aids to support and protect life are used, oxygen is needed and they make them a robot. A human being who survives in this atmosphere, cannot survive there. That form will not sustain. He merges in time. Time is body. Space is Liberation. It is impossible for Me to simplify this any further!
The movie Interstellar has attempted to explain this principle. It is a spiritual documentary.
(Q&A Session, 04/10/2015)