Underlinings (#53)

On the K/T-missile and its impact:

In one of the greatest titled books ever, T. rex and the Crater of Doom, Walter Alvarez told the story of how he and his nobel prize-winning physicist father Luis revolutionised our understanding of the end of the dinosaurs. [Walter] … discovered that the boundary layer in rocks found at Gubbio in Italy contained ten times the normal levels of the metal iridium. […] … Luis had the insight that such a high concentration of the metal in one layer of rock meant it must have arrived in one huge asteroid impact. The team then confirmed another iridium spike in a Cretaceous-Paleogene boundary rock section at Stevns Klint in Denmark. […] They reasoned that the spikes implied there had been an asteroid impact so big that it threw enough dust (including tiny particles of iridium) into the atmosphere to black out the sun around the globe. This would have prevented plants from photosynthesising and, as was later suggested, caused global freezing for a short time, leading to the mass extinction of many species. They worked out that such an asteroid would have weighed at least 34 billion tonnes and measured around 7km in diameter, producing a crater around 100–200km across. […] … However, it still took a while to locate the Chicxulub crater because it had been completely covered by sediments deposited in the previous 66m years. And while half of it lies under dense tropical rainforest, the other half is beneath the Caribbean seabed. Hildebrand used evidence from boreholes made by Mexican oil company Pemex in the 1960s to prove the crater’s existence. Subsequent geophysical surveys that can scan below the surface have established the exact size and shape of the structure, which is roughly circular with three concentric rings, as you would expect from a massive impact.

Island Universes

Before we move on to what we don’t know about [cosmological] inflation, there are a few things we do know that are worth mentioning.
1. Inflation isn’t like a ball — which is a classical field — but is rather like a wave that spreads out over time, like a quantum field.
2. This means that, as time goes on and more-and-more space gets created due to inflation, certain regions, probabilistically, are going to be more likely to see inflation come to an end, while others will be more likely to see inflation continue.
3. The regions where inflation ends will give rise to a Big Bang and a Universe like ours, while the regions where it doesn’t will continue to inflate for longer.
4. As time goes on, because of the dynamics of expansion, no two regions where inflation ends will ever interact or collide; the regions where inflation doesn’t end will expand between them, pushing them apart.

(This only gets us to Tegmark Level 1.)

Fake Physics

Some exorbitant multiverse complications:

[Paul] Davies argued that in a multiverse, “‘fake universes’ would be even more likely to vastly outnumber real universes [than in our one universe without a multiverse], so that if we live in multiverse, we would be overwhelmingly more likely to be living in a simulated reality. But that would imply that the laws of physics in our universe are also overwhelmingly more likely to be simulations and therefore cannot be used to conclude that there is a multiverse! So there is an inconsistency at the heart of the multiverse concept.”

Let’s unpack the argument and lay it out. To Davies, “If you take seriously the possibility of a multiverse of all possible universes, including all possible variations, then there would have to be at least some of those universes where sentient civilizations would advance to the point where they would have sufficient computing power to simulate entire fake worlds (like in the ‘Matrix’ movies). Simulated universes are much cheaper to make than the real thing. So once you’ve got civilizations throughout the multiverse that can simulate universes,” Davies stressed, then this is what they will do, and do increasingly.

As a result, “the number of fake universes in a multiverse will proliferate greatly and very soon outnumber real ones.” [Is Our Universe a Fake?]

Fake universes, Davies said, “undermine all the arguments for a multiverse,” because arguments for a multiverse are based on the physics of this universe. “But if ours is a simulated universe, then our laws are simulated, too, which means that the whole of physics is a fake.” And if the whole of physics is a fake, Davies said, then the whole argument for a multiverse collapses. The reason is that while the multiverse argument proceeds from the physics humans have discovered in this universe, people cannot use this argument because it then leads, surprisingly, to the conclusion that this is a fake universe, with fake physics.

Cthelll Vortex

‘Planetary gyre, time-dependent eddies, torsional waves, and equatorial jets at the Earth’s core surface’, N Gillet, D Jault, C. C. Finlay (Submitted on 29 Feb 2016), abstract:

We report a calculation of time-dependent quasi-geostrophic core flows for 1940-2010. Inverting recursively for an ensemble of solutions, we evaluate the main source of uncertainties, namely the model errors arising from interactions between unresolved core surface motions and magnetic fields. Temporal correlations of these uncertainties are accounted for. The covariance matrix for the flow coefficients is also obtained recursively from the dispersion of an ensemble of solutions. Maps of the flow at the core surface show, upon a planetary-scale gyre, time-dependent large-scale eddies at mid-latitudes and vigorous azimuthal jets in the equatorial belt. The stationary part of the flow predominates on all the spatial scales that we can resolve. We retrieve torsional waves that explain the length-of-day changes at 4 to 9.5 years periods. These waves may be triggered by the nonlinear interaction between the magnetic field and sub-decadal non-zonal motions within the fluid outer core. Both the zonal and the more energetic non-zonal interannual motions were particularly intense close to the equator (below 10 degrees latitude) between 1995 and 2010. We revise down the amplitude of the decade fluctuations of the planetary scale circulation and find that electromagnetic core-mantle coupling is not the main mechanism for angular momentum exchanges on decadal time scales if mantle conductance is 3 10 8 S or lower.

(Via.)

Synthetic Cosmogenesis

… a toy version:

The universe begins with a single input, an arbitrary numerical seed — the phone number of one of the programmers. That number is mathematically mutated into more seeds by a cascading series of algorithms — a computerized pseudo-randomness generator. The seeds will determine the characteristics of each game element. Machines, of course, are incapable of true randomness, so the numbers produced appear random only because the processes that create them are too complex for the human mind to comprehend.

(Via.)

Solar Agitation

At 11:15 a.m., Sept. 27, I stirred vigorously, and my hitherto mask-like face began to shew signs of expression. Dr. Wilson remarked that the expression was not that of my secondary personality, but seemed much like that of my normal self. About 11:30 I muttered some very curious syllables — syllables which seemed unrelated to any human speech. I appeared, too, to struggle against something. Then, just after noon—the housekeeper and the maid having meanwhile returned — I began to mutter in English.
“… of the orthodox economists of that period, Jevons typifies the prevailing trend toward scientific correlation. His attempt to link the commercial cycle of prosperity and depression with the physical cycle of the solar spots forms perhaps the apex of …”

Motherboard continues the story, or a different one.