when it comes to cosmology, bringing parallel universe in from the area of thought experiments and wild imagination is not scientific, but religious.
Damn, I was hoping someone would fall for that one
Space isn't exactly "stretching", otherwise I would stretch with it and wouldn't notice anything. Right?
Glowcat: there's millions of uses for 0 beyond counting apples. And how is "something" not a lack of "nothing"? Wordplay, I know, but without the symmetry of opposites words become useless. If there's no darkness, how can we be sure that light exists, et cetera.
More like... you can never observe its effects. You can never perform any kind of test to see if it's there. You cannot make any predictions based on it.
Any of those or all three? Because I can come up with something for each test, that would fail the other two:
1. God (I have experienced it's effects, but can't reproduce it and therefore can't predict it)
2. Virtual particles (virtual photon to electron-positron pair and back, for instance, can be tested for existence but it's observable effects are so minimal as to be non-existant, and the split/join can't be predicted). I cheat a little here but 1 and 2 are too intertwined to find something really exclusive.
3. Math (can't be "observed", can't test "if it's there" (since it's not "anywhere"), yet you can use it to make predictions)