I thought heaven was supposed to be not a physical place but a state of being in which you are one with God.
That's a very new-age interpretation though, isn't it?
rumborak
Iraneaus in the 2nd century wrote of heaven as a material place, but this mindset was shaped against a backdrop of gnostism that was plaguing the Christian community at the time. It only took a few hundred years to make Iraneaus's idea of heaven heretical. So in answering your question, no, heaven as being in union with God is definitely not a new-age interpretation and goes back to the 5th century.
Not too sure what the above comic is supposed to suggest. Does the author mean that sin is categories in our mind? Not sure what philosophy he's getting that from. Besides the interpretation of heaven in the comic again would be considered wrong according to Catholic theology.