Size of Things

An important aspect of the education of a physicist is to figure out the size of objects, usually through dimensional analysis. What  is the mass of that mountain overthere? How big is the Universe? What is the entropy stored in black holes in the Universe? So on and so forth.

Paul H. Frampton just estimated that the entropy of black holes make them very likely the DARK MATTER of the Universe, around one fourth  of everything that exists.

Here I estimate the highest energy of GRBs coming from far away in space and time, i.e. high z.

This is like the GKZ bound, on the highest energy cosmic rays, around 10²⁰ eV. Any more energy will make those particles collide with the cold photons of the CMB radiation, and they can only travel around 60 Mpc, i.e. a small z. Right here in a our cosmic neighborhood.

By the same token, very high energy gamma rays, now being measured by the FermiLAT combination in space cannot be very energetic if they come from afar.

So I suspect that LAGO, a cosmic ray collaboration measuring one or more TeV gamma rays on the surface of the Earth, will get only nearby sources gamma rays measured.

Here comes the crux of my point.

The farther these objects are, and the higher their energy is, the more likely is that they will probe the quantum gravity structure of spacetime.

I propose that the size of things is such that it will be hard to measure this quantum structure of spacetime. The farther the source of the GRB is, the more degraded it gets, and the closer in time the different "colors" will get to LAGO, and therefore the harder it will get to prove that we are seeing the planck length or time.