Hi mgs. I admit this discussion is becoming less trivial than I expected. I almost didn't want to get involved because of how stupid I thought it would be. And I apologize for my previous outbursts of incredulity. I appreciate your patience, and hope we continue in a similarly civil vein.
Actually, if the earth received the core of the earth at the K/T boundary, then the nuclear fission that began then would be a heat input.
The core is just that: the core. If there was no core prior to the K/T boundary, then what do you propose was there? Moreover, where do you get this idea that the Earth "received" a core at the K/T boundary?? Way too much surface older than that still survives intact today for there to have occurred something as catastrophic as this. I expect such an event would have wreaked havoc with the crust and the mantle. Where is the geological evidence of such a tremendous upheaval? Where did the previous core go? Such a gigantic impact would have thrown up a great deal of debris into orbit. We would have more than one moon, and the moon we have right now would be peppered with major craters and clearly identifiable (isotopically) Earth material dating back to the K/T boundary. None of that is the case. I believe there is evidence that the Earth had a magnetic field prior to the K/T boundary; magnetic field reversals are documented in ancient lava flows and I haven't heard of this form of fossilization having a cutoff at the K/T boundary.
Alternatively if nuclear fission is a much larger source of the earth heat than the radioactive decay, then it might not be significantly cooler than it was in the past.
?? Nuclear fission and radioactive decay are the same thing.
If greenhouse gas concentrations were higher than now, and there was equal water vapour, then an explosion soon would not be expected,
?? why?
but Vincent Courtillot claims that volcanism was a partial cause of the disappearance of the dinosaurs. I think it was the volcanism that created “the Deccan Traps”. Therefore perhaps catastrophic volcanism could be expected if we didn't act fast to reduce greenhouse gas emissions?
It is widely accepted now that the K/T boundary is defined by a massive impact of a mile-wide or larger asteroid. Such an impact would send powerful shockwaves through the entire planet which would manifest as massive earthquakes. They would be especially dramatic on the opposite side of the globe from the impact site, where concentric shockwaves would converge toward a point and constructively interfere. If the impact was indeed around the Yucatan peninsula in Mexico as is currently thought, then it wouldn't be surprising to find such convergence of shockwaves somewhere around India. It would naturally trigger massive volcanism.
While a global spike in volcanism would certainly not be conducive to dinosaur survival, the main effects leading to their extinction would stem from the impact itself. It would send massive tsunamis through the oceans, circling the planet multiple times and destroying all low-lying and coastal areas. The massive oceanic shockwave would wreak havoc with large aquatic organisms, whose large bodies and internal cavities would resonate with the repeated low-frequency shock fronts. The impact would throw a large amount of debris into parabolic suborbital trajectories; when this debris falls back down to Earth it will be in the form of molten rock, doing direct explosive damage and setting off massive fires all over the world. The impact itself, the secondary impacts, the fires and the volcanoes will throw up a great deal of dust and particulates into the atmosphere, resulting in a catastrophic multi-year global cooling. At the same time, the noxious gases from the volcanoes and the explosions vaporising rock would generate world-wide acid rains. At the same time, rampant oceanic volcanism would alter the chemistry of the oceans, making them potentially toxic to many lifeforms. On top of it all, there would have been massive disruptions in the food chain, devastating large creatures which needed to feed constantly in order to survive.
I totally agree that everyone thinks that if the earth gets hotter, more of the core becomes more mobile, but possibly the lighter parts of it first because less force is required to accelerate lighter materials to a certain degree.
That would be true, except the lighter parts are precisely the parts that
don't contain high percentage of fissile material. The parts that do contain it are heavier, and they heat up to the exclusion of the lighter parts. Rock, generally speaking, is a pretty good thermal insulator, so I expect convection to take place before heat transfer could equalize temperatures.
Indeed Herndon suggests that a good explanation for the variability of the geomagnetic field is that the lighter materials melt and leave the core, while the heavy ones only melt and heat up to the extent that the conglomerate.
That wouldn't explain such things as magnetic field reversals. At any rate, I don't believe anyone has a convincing account right now of how the geomagnetic field evolves. This doesn't mean there's no progress. For example:
http://www.psc.edu/science/Glatzmaier/glatzmaier.html
Repeatedly people, particularly Chalko and Herndon, have referred to the idea that the fissionable materials differentiates, when the core gets hotter, not to the idea that the fissionable materials are dispersed by convection.
Use common sense to figure out which is more likely. For example, imagine two immiscible liquids in a beaker, one heavy and one light. If you leave them alone, they'll eventually settle into two distinct layers, with the heavier liquid on the bottom. Now put a heat source under the beaker (which will warm up the heavier fluid first, simulating fission). You'll observe convection, with the fluids increasingly mixing up in a chaotic flow of currents. The more you heat it, the more chaos there will be. This is as opposed to increased differentiation, or order.
So I guess the key would be to compare your model of the core with Herndon’s to see which one makes more sense? I wouldn’t want to prefer your model just because it means we should forget about the issue. <b> What do you think?</b>
I suppose the best judge ought to be observation. As we observe our planet intact after 4 billion years, I'd say there's something wrong with Herndon's model.
I don’t know what properly aligned implosion charges are. If it is just an analogy that you use to help explain the last paragraph I discussed about differentiation as opposed to dilution, I guess it may not matter, but please correct me if I am wrong.
Briefly, the simplest nuclear bombs consist of a shell of Uranium or Plutonium, cut into chunks (for example, like slices of an orange), which are separated from each other. This configuration spaces out the fissile material, thus preventing it from being at a critical mass where a runaway fission reaction would occur. Around these dowels of fissile material are placed a number of high-explosive charges that are directional and pointed inward toward the center of the split shell. When precisely balanced as to strength and detonated in a precise sequence, these implosion charges jam the pieces together and symmetrically collapse them into a ball of fissile material which then has a sufficient critical mass and density to touch off a runaway chain reaction. A nuclear explosion follows.
If these implosion charges are misaligned or not fired off in the precise sequence, instead of collapsing the fissile material they will blow it apart and no nuclear explosion will occur. This demonstrates the tight balancing act that must be achieved to have a nuclear detonation. In the core, such a balancing act is impossible due to the chaotic currents and convection. There is nothing in the core that could precisely contain and concentrate fissile material into a critical mass sufficient for a nuclear explosion of the magnitude that would blow apart the Earth or even significantly increase volcanism at the surface (which is insulated from the core by thousands of kilometers of liquid and solid rock.)
“For a core to overheat, the amount of heat produced by the core should exceed the amount of heat transmitted to the planetary surface and emitted into space.
The problem with this is that it assumes the amount of heat emitted by the planetary surface is constant. If the core were to heat up, this heat would melt its way through the mantle and eventually the crust, heating up the surface and then getting radiated into space.
The higher the planetary surface temperature, however, the more heat radiated into space to cool the planetary interior (and the core). Hence, hotter planets may not necessarily have hotter cores.
That is very wrong. Consider two kettles full of boiling water. One is at room temperature. The other is red-hot. In which case does the water in the kettle cool faster?
The problem here is that our "crust" is a thermal insulator. On one hand it is good, because we do not have to walk on lava, but on the other we have to be very careful not to overheat the interior by putting more insulation (greenhouse gas pollution) for too long”.
This ignores the fact that our "crust" exists only because it is cool enough to be solid. If the core heats up too much, the crust will melt, thus eliminating some of the "insulation" while simultaneously removing some of the heat from the core. Naturally, the system balances out so that if the core were ever to just keep on heating up, it would eventually melt the entire crust through, returning the Earth to its original state as a ball of magma. If the core continued to heat up, this ball of magma would expand due to heat-driven expansion, much in the same way that red giant stars form. But any of this is impossible, as the Earth has ever less internal energy ever since it was formed, due to the ongoing nuclear decay.
Secondly I wonder why the planet has no magnetic field and has a deep crust. Is it that it has no molten rock? Why is that the case, if it is so hot? Perhaps, due to the pressure of the atmosphere, there is not much scope for the continuation of fission reactions and therefore the interior of Venus is not so hot?
The surface of Venus is hot not due to some internal heat from the core, but due to the greenhouse effect generated by its atmosphere.
Venus has no magnetic field to speak of primarily because it practically does not rotate. For earth, its rotation drives its internal dynamo. For Venus, one day lasts 243 Earth days. Not much of a dynamo to speak of.
Venus has a much thicker crust because it retains most of its primordial crust. Earth lost a lot of its surface crust in the impact that formed the Moon. The Moon is, in effect, the old crust of the Earth sent into orbit. That's why it has a relatively low density compared to Earth, and proportionately a much smaller core. For example, see here:
http://www.spacedaily.com/news/lunar-01d.html
The pressure of the atmosphere is insignificant when compared to the pressure from the overlying rock. For example, 3 meters of water are equivalent in pressure to 1 Earth atmosphere. Rock is usually heavier than water...
Consider that heavier elements might not be closer to the sun, since higher forces would be required to decellerate heavier objects?
They are closer to the Sun, for two reasons. First, when heavier particles orbit together with lighter particles, the lighter partiles tend to be kicked out while the heavier particles coalesce toward the center. Second, the emergent Sun sends out streams of radiation and solar wind that sweep out lighter particles before they do heavier ones. Thus you get the situation where the rocky planets are concentrated toward the sun, and the gas giants are on the periphery.
but there were suvivors