Originally Posted by Dannon Oneironaut
If we cannot detect dark matter, and we can only infer its existence, that might mean that we have the whole thing wrong. The idea of dark matter seems to be the substantialist fallacy of something that doesn't exist, but is it? Now I have no idea what I am talking about because I am not a scientist, only a philosopher, but I have heard that the existence of dark matter is inferred to explain why some parts of the universe expand more rapidly than others. ? Knowing that the universe is expanding from all points, it is conceivable that we have the geometry slightly wrong. The singularity might be not be the big bang which we also infer from the fact that the universe is expanding. What else is a zero-dimensional singularity which can be the cause of this?
No. You can find an explanation for what dark matter is in this thread. Basically it's about galaxies spinning faster than it seems like they should be able to without flying apart. Hidden matter means extra gravity to counteract this effect.
But the Big Bang is kind of like the opposite of a black hole. It expands, it is an expanding singularity, which expands into all dimensions, maybe like a fractal. But how can something that is infinitely small expand? How can something that is infinitely big expand or come out of something infinitely small?
For one thing, we don't know the universe came out of a single point. We can see back to a few nanoseconds after when it was a lot smaller, but not back to the beginning.
Also, in any case, it wouldn't have been a 'single point'. The expansion of the universe would be better named a rarefication of the universe. We don't know how big the universe is. It may in fact be, and in this context it's more helpful to think of it so, infinite. So expansion doesn't mean it's getting 'bigger'; just that it's becoming more stretched out.
The second and probably more philosophically important point: why not? Science has repeatedly shown human imagination to be severely limited. Principles which are true in the small bubble we inhabit are actually totally false on a universal scale. Why shouldn't a point be able to expand into nothing? Think of the function f(t) = [0, t]. At time t = 0, f(t) = {0}, a 'single point'. But at literally any time after that, no matter how tiny, say t = a > 0, f(t) = [0, a], which means every single point between 0 and a - of which there are infinite. Why can't the universe behave like such a function? You can't raise any philosophically valid objections. If that's the way stuff works, that's that. Same with everything.
Well, the only thing I can think of as infinitely big is the Universe. The only thing I can think of that is infinitely small that makes the universe possible is...... The Present Moment. This present moment is infinitely small, it is a singularity. You can always divide the moment in half. Yet this moment is the whole Universe. It is kind of an intersection between dimensions or something. Now, if only I was not only a philosopher, but a scientist as well I would know what I am talking about. But I think there is some truth to this, as the only things I cannot deny are that the Universe exists and that the present moment exists.
Funny... the thing that you just said is undeniable is actually false. The entire concept of 'the universe at a single time' is an illusion - we only think it's true because it's a very good approximation to our experience on the scale that we, as brains inside squishy little animals, live. We've evolved on that scale, and so our entire mentality is based on that being true. It helps us survive. But it's only an approximation, and on larger scales, it's totally false. This is called the 'Relativity of Simultaneity'. It's one of the consequences of Einstein's Theory of Special relativity from 1905. What for you are two simultaneous events, may, for your friend, completely literally, not have occurred at the same time. Neither of you is wrong. It just seems contradictory because of your false assumption that there is this thing called 'the present'.
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