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.

-jM

A&D