Do we live in Middle-earth?

[Reginald Hill]

In response to Leto

As for the 'scientific proof' of parallel universes, in the way which was described above, citing the phenomena of gravity, etc...that is all very nice speculation, but no real evidence or 'proof'.

The idea of PUs is a theory. Theories are based on observations that are true until further observations prove them wrong (that's a little unclear I think). Theories can almost never be proven right because their is always the possibilty that it will change. That way any largely believed theory can turn out to be wrong. So until observations show that PUs don't exist (which may already have happened, I'm not up to date on any scientific discoveries) the theory stands.