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Comment by danbruc | Hacker News Reader

That is, they mistakenly believe that infinity actually exists. Like, in the real world.

Well, for all we know, they universe might be infinite and contain an infinite number of galaxies, stars, atoms, ...

The universe most certainly is not infinite by any measure and does not contain infinitudes.

You seem very sure for such a wild claim. The observable universe is finite, as for the whole universe, we have no idea (unless you know something that I don't).

But we have at least measured the curvature of the observable universe and within experimental error the result is that it is flat. Which in turn would imply an infinite universe if this flatness is exact and general, i.e. not something exceptional in the observable universe.

There are manifolds that are flat and compact (i.e., not "infinite"). For example, flat tori.

Good point. How did I never realize that?

The measurable universe is not infinite. There's a limit to how far we can look back due to the speed of light, but the universe is expanding faster than the speed of light.

The _observable_ universe is finite. The rest of it – that's an open question.

There's a point in the very distant future where someone in our local group will observe nothing in the beyond. Kind of makes you wonder what we might have missed.

Do we know that for certain? We think space is still continuous right? So there's an infinity between any two points.

Even with all the plank-length stuff, they're not snapped to a plank grid right?

I'm genuinely asking: my level of knowledge is YouTube.

Yes actually, particle motion is quantized on the planck scale, that is, snapped to the grid. That's why it's called quantum physics. Modern theories even have it that there are no particles, rather, excitations of various quantum fields.

So what we consider a discrete photon particle with a location (x,y) would actually not be an individual particle and would be more like:

  electromagnetic_field[y][x] = "excited"

in a big (presumably infinite) grid.

Quantum fields are mathematical tools, they are not what the universe is made out of.

Aren't infinitudes accurate descriptors of any probability-based phenomenon? As far as I'm aware probability is not quantized.

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