A lot of modern physics is considering ideas that consider time, space and matter to be subject to perception. A simplified tenant being that humanity percieves time like a river - flowing from past to future - but the truth may actually be that time is more like a lake with all events occuring simultaneously ad humanity chooses which events to percieve.

The universe does not cease to exist if no one is there to observe it. It merely ceases to exist in the same way as it was percieved by that being. We build pictures of the universe inside our heads based on signals recieved by the senses. We all know that the apple is red/green because we were taught that the particular complex of sensory signals (reflected wavelengths of light) we receive when we look at the apple relate to that colour.

And to answer the question asked at the start: Surely everyone knows the answer to this. Truth is beauty and beauty is truth