The void between the Planck length and (the next thing) is interesting. It's area that shows our ignorance.
The most, or rather, one of the most, interesting things I took out of studying cosmology, was, one of the horizons.
Now, cosmology has many horizons, most people are familiar in a trivial way with the 360 degree one that defines earth from sky, and a few people more know about the event horizon which is usually used with black holes.
But there are many more horizons in physics, and I think the one he was talking about was the causality horizon, he, being the prof.
Where, if you take Hubble expansion to be true, which, from observation, seems to be true.... well it's the that pure space is expanding, and measurable. Measurable to the tune of 21 km per second per million light years.
Now, 21km/s is very fast! But spread over a million light years, well, maybe it's not so much. But anyway, it give you the building block, to imagine, ok what about 2 million light years... now its 52km/s. And three and four and so on million light years. Do the math and eventually you reach a distance where the expansion of space is faster than the speed of light.
Suddenly, you have a very easily calculable distance from Earth, which give us the size of not the "know" but the "knowable" universe. Discarding the cosmic background radiation and inflationary periods, we know there exists a bubble around the earth which defines everything we can know or experience, and perhaps more disturbingly, nonetheless, we know that there is more beyond that. It resonates of Goedel's theorem.
it's funny as i was commenting to my wife on the void between the planck length and the next big thing and how there's so little we know about the quantum world, little lone the universe.
zorro...we're not the centre of the universe, not even the centre our own galaxy (we rest on an outer spiral). our solar system rotates around the galaxy for 250 mill years or so, and our galaxy is part for a (super)cluster which are bound gravitationally as well. we're certainly not the centre of the universe. unless you're talking about ego.
like jeffus was commenting, it's about horizons. the authors are starting with common reference point for simplicity not implying we are at the centre, also technically they start the scale right of centre on the slide to show the scope of reducibility in size to the planck length, as jeffus comments there is so little we understand about this quantum reality and as we discover its mechanics a picture of the universe on a grand scale becomes clearer. they're making no comment on a centre of the universe, which quantum mechanically and cosmologically have a very different meaning or none, one could almost say the universe on a grand scale has multiple centres (groups of superclusters of galaxy gravitational bound), but technically there is no centre in our universe as there's no centre point for its expansion, it happens everywhere at once.
the aim of the graphic is to show you scalability, nothing more.
@ jme...you're welcome. this stuff fascinates me too.