109,226 reputation
4166295
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 9 months
seen 38 mins ago

Semi retired old time computer nerd who started programming on a Commodore Pet.

Since I'm also active in the Physics forum I should add that I started as a theoretical chemist, moved into solid state photochemistry and finally worked in industry as a colloid scientist. I only became a full time computer nerd in 1997.


Oct
20
comment Bubble pressure ascending?
Do you think the pressure inside the bubble will be greater than, less than or equal to the pressure of the water around the bubble?
Oct
20
comment How to feed a small black hole against 1 TW Hawking radiation pressure?
Oops, I missed a factor of $1.602 \times 10^{19}$ :-)
Oct
20
comment About time measurements
No, there's no suggestion that time isn't continuous. The illusion is that it flows. We wouldn't say that distance flows; it just is. The same argument applies to time. Do some Googling for block universe for more on this idea.
Oct
20
comment About time measurements
The interval between two timelike separated points certainly isn't an illusion. The illusion is the human perception that time flows.
Oct
20
comment How quickly was the Earth rotating 250 million years ago?
@DavidHammen: agreed - my reply was intended mostly to point out the error in the orginal question. The exact value for the rate of change of day length doesn't really matter, and I don't think a change of 2.3 vs 1.7 ms/century affects the conclusion that the Earth wasn't created in 4004BC.
Oct
19
comment Why can't we reach the ends of rainbow?
Rainbows are circles so they have no ends. They look semicircular because we can usually only see part of them.
Oct
19
comment What prevented the early universe to become a black hole before inflation?
My comments to that question address the classical GR theory not LQG.
Oct
19
comment What prevented the early universe to become a black hole before inflation?
I wonder if it's worth writing another blog type question and answer on this topic ...
Oct
19
comment What prevented the early universe to become a black hole before inflation?
Oops, drat! Try this link.
Oct
19
comment Metal with the biggest positive and negative charge per atom (ion)
Metal ions form the basis of charge storage (in electrical double layers) in supercapacitors. However I think these mostly use monovalent ions like Na$^+$.
Oct
19
comment Metal with the biggest positive and negative charge per atom (ion)
This is really a chemistry question. In the physical world we can make arbitrarily highly charged ions e.g. gold nuclei, Au$^{79+}$, are made at the RHIC.
Oct
19
comment Loop quantum gravity- is the critical density sufficient to form a 'black hole'?
Yes. If you want to understand this I'm afraid you'll have to get stuck in and learn about the FLRW metric. Without knowing your background I'm not sure what to recommend as a starting point. The Wikipedia article is not suitable for beginners. Incidentally your other question also stems from misunderstanding the FLRW metric.
Oct
19
comment Loop quantum gravity- is the critical density sufficient to form a 'black hole'?
A finite, i.e. closed, Friedmann universe is homogeneous and isotropic just like flat and open Friedmann universes. In the real universe at the current time the matter distribution is obviously not isotropic and locally black holes and their associated horizons can form. However if you look at the CMB (that dates from the recombination era) the universe was homogeneous to about one part in $10^5$. Because inhomogeneities grow with time we expect that near the Big Bang any conceivable universes would be almost exactly homogeneous.
Oct
19
comment Loop quantum gravity- is the critical density sufficient to form a 'black hole'?
The universe is described by the FLRW metric. This has a singularity at $t = 0$ (and for closed universes also at the recollapse time) however it has no horizons. A black hole is described by the Schwarzschild metric. This has a singularity at $r = 0$ and a horizon at $r = 2GM/c^2$.
Oct
19
comment Loop quantum gravity- is the critical density sufficient to form a 'black hole'?
No, because the matter distribution in the universe is (approximately) homogeneous so the gravitational potential is the same everywhere. There is simply no concept of a Schwarzschild radius in these circumstances.
Oct
19
comment Can a Storm make the day longer/shorter?
You need to estimate the angular momentum of the jet stream and compare it with the angular momentum of the Earth. I haven't done the calculation, but I'd be surprised if the effect was measurable.
Oct
19
comment Loop quantum gravity- is the critical density sufficient to form a 'black hole'?
The universe is not described by the Schwarzschild metric so it has no Schwarzschild radius.
Oct
18
comment While finding escape velocity, does human mass counts as the mass of Earth?
@FranciscoPresencia: the mass change due to absorption or emission of radiation is negligible.
Oct
18
comment Building blocks of particles in different theories
No. The concept is specific to quantum fields. The motion of planets is described by a classical field and this is completely different.
Oct
18
comment Building blocks of particles in different theories
You'll have to clarify what excitation at the macro-scale means.