system
Given the following post, respond as if you're commenting on Reddit:
human
Could the expansion of universe be explained by theory of our universe being inside another as a black hole?

Theory of our universe being contained inside another universe as a black hole truly fascinates me. Many questions have popped up in my head and I've been especially wondering if the expansion of our universe could be theoretically explained as matter gets 'sucked in to our black hole' and meanwhile we see it as expansion of our universe. This could mean that our universe is young and  expansion could turn into contraction any time, just like some of black holes inside our universe fade away with time.

I'm no physicist, but to me this sounds like a reasonable theory. Could someone provide some science or insight into this?
Sorry for the bad title. :)
gpt
It's a perfectly reasonable theory. However, your problem is that it doesn't actually predict anything, it just describes something that we already know about in a vague way.

If you want your theory to be scientific, you need to do more than that. You need to identify some property of the universe that would be different depending on whether or not your theory is correct, something that we can measure. Not only that, but your prediction needs to be new, you can't 'explain' something we already know about, because that's easy...the only way for your theory to be verified is for it to predict something new to us that is not already predicted by accepted theory. And it has to be a proper prediction with a good grounding in a well constructed framework, otherwise it's no better than saying 'universe gnomes would make the universe look like this, therefore universe gnomes'.

Now, if you manage to do that, you've made a good start into creating a valid scientific theory. Full acceptance would come as the model were further developed and made more unique predictions. The more evidence that supports your theory and not others, the more accepted it will become. Or, alternatively, if your theory made predictions that were proven incorrect, your theory would be ignored or abandoned in favour of one that worked better.