There are things beyond science and its called Metaphysics. I hope you don't mind me talking about metaphysics here. Space in infinite. However, you will not understand infinity until and unless you experience infinity. True knowledge only comes through direct experience. Our forefathers already asked this question thousands of years ago and came up with the word Atma and Brahman. Atma and Brahman are same. Atma is the subtle consciousness within and we call the same Atma as Brahman because of it nature of expansiveness. However, Atma doesn't depend on Space and time for its existence. Space and time exist because of Brahman. For example, diamond doesn't intent to shine, but shining automatically happens because of its existence. Similarly, numerous universes exist because of this Atma alone. Atma is pure consciousness. Atma is undivided, immobile reality. Atma is one without a second. The drama of universe takes place in Atma. Atma is the canvas, Atma is the painter, and Atma is the color. And who is watching this painting called the Universe? Technically speaking, there is no such thing as universe of duality and universe where varieties of objects exist. When we see dream, mind itself appears as various objects, mind itself appears as the perceiver of dreams, and it is mind alone where all the drama of dreams are happening. When we wake up in the morning we realize that whatever we saw last night was fake, was unreal. How did we know that the dream we saw last night is unreal? It is because we wake up to a different finer reality which is more fascinating and more real than the dream world. However, you cannot say that the dream world was unreal. It was real for the dreamer for the time-being. Dream is not a dream but we call it dream to distinguish between our waking reality and sleeping reality. Dream is in fact waking reality in relation to dream itself because we are awake to a different reality. We only call it a dream in relation to our waking world. Consciousness is a funny thing. The moment your awareness shifts, your whole reality changes. Ordinary human beings only live through three states of consciousness: waking consciousness, dream consciousness, and deep sleep consciousness. Beyond this three states is Transcendental consciousness where universal law of Atma is revealed to you in its own glorious state. It is Sat-Chit-Ananda. It is existence, it is consciousness, and it is pure bliss. In it no duality of objects exist. It is neither existence, nor non-existence. It is immeasurable because it is infinite. Where does it exist? This question of 'where' doesn't even apply to Atma, because it doesn't depend on space. Since when does it exist? The question of 'when" also doesn't apply to Atma because it is timeless. If you see variates of objects in this universe, you are still living in waking state of consciousness which is the result of ignorance of Atma. Atma alone was, Atma alone is, and Atma alone will be. This is whole, that is whole, from whole comes the whole, when you divide whole from the whole, whole remains!