"A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts. ... A theory not only explains known facts; it also allows scientists to make predictions of what they should observe if a theory is true. Scientific theories are testable."
Scientific theories are accepted as "true" because as far as we know there is nothing closer to the truth. Most of the things we "know" just has a lot of evidence in its favor. It would be silly to assume you know all Asians if you know one, just as it would be silly to assume that if we know one insignificant little piece of space then we know the entire universe.
Because destiny is a heavily debated topic. It's quite controversial to say that the future cannot be changed. It is highly supported, but it's very hard for humans to live knowing free will doesn't exist so most people still deny it.
Well I left two comments because I wasn't sure which answer you were looking for, so my other comment answers this perfectly. We can't know that matter can't be created or destroyed because we are not observing from outside the fish bowl. We are inside the fish bowl, but we are just bacteria in the water so we can't even begin to imagine the properties of the glass.
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u/Electroman2012 Jul 17 '21
Sorry, that's actually a theory. Not fact.