makes sense but is it easy to figure out how old the supernova is? or what state it is in?
Therefore, when observing a type Ia SN, if it is possible to determine what its peak magnitude was, then its distance can be calculated.
this is what i mean. how is it possible to figure out the peak magnitude?
"what if the universe already plays tricks like that on us now?"
I think this can't be the case, because we see the microwave background, which is 14 billion light years away, and the universe is 14 billion years old. So there can't be anything invisible to us that was visible before, because it was never possible to look beyond the microwave background.
i mean in general. not specific to the age or something. ...what if something else has happened already that distorts the observation of the universe's true nature?
