How do we know for sure that we live in three dimensions?

Sure, our surroundings certainly appear to exist in three dimensions, but any good Cartesian will tell you that the appearance of a material object alone is insufficient evidence of its true nature. So how do we go about proving that we aren't, in fact, deluded inhabitants of Abott's two-dimensional Flatland, or even the one-dimensional Lineland?

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The short answer is: a lot of ways, involving a lot of physics and a lot of mathematics. But that's kind of a cop out, right? So here's an almost-as-short answer by physicist-animator Henry Reich, who explains in just sixty seconds one way that physicists go about showing that we are, in fact, three dimensional beings caught up in a multi-dimensional existence.

The video is just one in the awesome ongoing series titled "One Minute Physics," which features animated crash courses on topics like quantum tunneling, special relativity, and the Heisenberg uncertainty principle, and is definitely worth checking out.

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[Spotted on New Scientist]

Image by gualtiero boffi/Shutterstock

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DISCUSSION

Corpore Metal

I share other commenters disappointment in this video. Because of things like tessellation, holographic mappings, fractals and so on, we can map any three dimensional phenomena to at least two dimensions or lower. Assuming things are actually discrete and digital, we could even just reduce it all to a huge one dimensional string of binary numbers that changes over time.

The expansion of a gas doesn't prove anything any more than any other evolving physical system that changes scale over time. The connection just isn't that strong.

But yes, we assume that all three dimensions and time itself being the forth as being real.

Which begs the question, why do we treat these as real but not the 5th as real? Our four dimension space-time expands. What does it expand into?

Well, we can also play games with tessellation and holographic mappings to avoid creating a fifth dimension that space-time distorts or expands into.

But we can do the same with our 3 dimensions too. So why do we arbitrarily decide our three our real but the fifth isn't?

Or higher dimensions for that matter! Since recent attempts to unify gravity with the rest of the Standard Model seem to require the creation of still higher dimensions (11 or 22).

Where's Dave Goldberg when you need him?