Sikh perspective on universe is that Universe exists inside of you. One projects what they want to experience physically outside in this illusion. This is written in bani as "Jo brahmande soi pinde" sabdh by Bhagat Pipa ji. It's also verified by Bhai Raghbir Singh Bir autobiography Bandginama. His meditations confirmed this revelation that Universe exist inside of us. It's like a hologram where each part contains the whole. Aliens exist or don't is it really important on path of Sikhi ?