On Wed, Aug 7, 2019 at 11:40 PM Bruno Marchal <[email protected]> wrote:
> On 7 Aug 2019, at 15:08, Bruce Kellett <[email protected]> wrote: > > What exactly is the difference between something that it is impossible in > principle to detect and something that does not exist? > > > It is like the difference between the human existence and the human non > existence, for an alien situated in a very far away galaxy. The fact that > this alien cannot detect us does not make the human disappearing. > You got that the wrong way round. It is like the supposition that aliens exist in some remote galaxy where we cannot detect them. Their existence or non-existence is irrelevant to us, so there is no difference between their non-detectability and their non-existence. We are not asking what the aliens think about our existence -- our existence is a given for us. > It is like the other side of the moon before we built rocket. > The far side of the moon was always observable in principle. Rockets did not change that. > It is like taking our theory at fave value, instead of eliminating some > terms in the equation by sheer coquetry. > Taking any theory at face value is a mistake. We have to test all the theory's consequences. And if we find some consequences to be untestable (causally disconnected from us, for example), then those consequences remain speculative and not to be relied on as true -- they can be eliminated from our consideration until such time as direct evidence is obtained. Physics is about the observable, not the unobservable. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLQGersUa96pv7u0M%3DqwnQe1FufOHEiON_CzT5ZvRudyLQ%40mail.gmail.com.
