Tom made reference to a map of gravity anomalies as evidence for creation of matter.
Not necessarily so Tom.
If one looks at the earth as a system that is powered internally by a combination of atomic energy from long lived isotopes and a small amount of tidal heating which is converting spin to heat, both of which are slowly running down, then the earth will be very slowly shrinking (due to cooling, as the process dynamics slowly change).
However, that effect is so small that it is overwhelmed by plate effects. The plates are heavier than the liquid they are on, and so where they have broken at the margins they are dipping down and dragging the ocean ridges apart. The shrinkage, combined with the compression of the plates going down, force up an excess of material at the spreading zones (and anywhere else where there are weaknesses it can squeeze through), thus creating the “gravity anomaly”. No anomaly at all really, just greater attraction from a greater amount of mass.
[And when you think about that process, and the mantle being a liquid, it is liquid in the same sense that glass is a liquid. If you go to a very old building (500 year old church for example) that has some of the original glass in it, then you will find that the glass is much thinner at the top than at the bottom – it does flow, just very slowly. Last time the earth grew significantly seems likely to have been about 4 billion years ago when something about the size of Mars collided with it – probably initiating plate tectonics.]
Why would you think the earth is expanding, other than from the small amount of meteoric material collecting on the surface?
[followed by Ted, where’s your evidence that the matter we call Earth, including all the water no doubt, crashed together (crashed together) to form a planet with a practically infinitely complex biosphere?]
Vast evidence sets, Ockham’s razor – the general progression of science over the last few centuries.
I don’t deal in any sort of absolute truth, just probabilities on balance of evidence and hypothesis.
Where did you get the idea that the earth’s magnetism comes from fixed magnetic alignment?
Best models use dynamo like components – and it is complex – as many things are – Wikipedia earth’s magnetic field
Your objection is overly simplistic and based upon false assumptions.
Metals can be charge carriers when molten, and charge going in loops creates magnetic fields.
And I have seen meteors hit the earth.
And I have used a very sensitive magnetometer to measure very small changes in the magnetic field over very small times, that is perfectly consistent with magnetic field being created by charge carrying particles.
And yes, I was in the first undergraduate class devoted to the teaching of plate tectonics, and it is a very complex topic, with many sets of evidence from many aspects of geology, including geochemistry, geomophology, paleomagnetic studies, etc and provides an explanatory framework for many different things. It is a huge field.
[followed by So what’s with all the continents fitting together?]
That is a repeating process.
Anything that sticks up, gets worn down.
Watch a river in full flood – it is brown, it is carrying a lot of rock within it – not clear.
Certainly, there was an original crust, and some small fragments of it still remain, and it seems most likely that the original crust was mostly fractured by the collision with a Mars sized planetoid, and that probably initiated the sort of plate tectonics that we have (which we don’t see on any other planet).
The process we have is that stuff gets washed away, and deposited off shore. The plates collide and push up stuff. And there are several different sorts of volcanism at plate boundaries that enters the mix, and some of that involves hot water across pressure gradients that delivers complex chemistry and mineral deposition at particular parts of those gradients, etc. And some sorts of volcanoes are particularly violent (like Toba or Yellowstone or Taupo).
So there are all sorts of different things happening, at different time scales. And every few hundred million years, all the continental material tends to end up in one lump, then it gets torn apart and away the pieces go again.
And biology happens in that process.
Yes the sea floor regions are young, and constantly being renewed at the centers, and subducted at the edges (at least in the Pacific, and that will start in the Atlantic when the Pacific closes, but that is many millions of years away). Part of New Zealand will end up close to the USA – but I live 5 miles on the south side of that boundary, so I’m on the bit going the other way. Which is why we had the 7.8 quake here 2 years ago, with all of its ongoing implications for our lives.
It is a fascinating subject.
The mechanisms, the techniques for aging minerals, particularly the radioisotope stuff, the global impacts of large collisions (like the Chicxulub event – which has evidence on the surface not far from here, in a small valley called Dee Stream – where the KT boundary layer is exposed in a limestone formation).
Taupo has not gone off while humans lived here, but it did go off in AD186, and the Chinese recorded that they heard it. That is a big bang!
China is a long way away.
The dynamics of that explosion were fascinating to study – the physics of it, as well as the geochemistry behind the physics.
Vast evidence sets, if one takes the time to engage meaningfully with them.
Having grown up in this place, right on a plate boundary, does make it immediate for me, in a way that probably isn’t real for people who live on older more stable landscapes.
I now live beside the youngest and fastest growing mountains on the planet. Fascinating, both geologically and biologically.
It’s one of my many geeky things.
[followed by So what’s with all the continents fitting together?]
They fit together because that is what they do every couple of hundred million years.
The bits crash together, get twisted, distorted, raised up into mountains, lifted up by the light remelted materials underneath (remelted from the stuff on top of the subducting plates). Get reformed into new crustal material – then get split up again.
It is a really complex set of processes.
So of course the continents fit together – it is what they do.
Continents crash together, periodically – just as India is crashing into Asia pushing up the Himalayas right now.
Every few hundred million years they all end up in one place.
Then the drag from subduction pulls things apart, into new shapes (just as we see now in the opening of the great rift valley in Africa).
The continents all fit because that was how they were torn apart last time.
Yes – of course they were torn apart to give the shapes we see now. That is what I said.
Note that they were torn apart on a globe near enough to the same size as the one we are on now – no significant amounts of added matter – just a bunch of lighter material floating on top of vast moving sheets of stuff. All happening with spherical geometry, causing lots of cracks as things bend and fold down.
Lots of other complicating geochemistry happening also.
Over the life of the planet – lots of repetitions of crashing together, then tearing apart again. Hence the complex geology we observe.
Again Tom, from my perspective, the notion of a “preferred centre” does not comprehend what the big bang is about.
The is no preferred centre in big bang, there is only expansion of space itself, change of curvature. That does not imply any preferred centre – it can still be entirely relativistic.
As I state repeatedly in most of my writing, from my perspective, understanding is rarely if ever an “either or” sort of thing, it is mostly (if not always) a “both and” sort of thing.
Particularity and distributed vibrational both seem to be essential aspects of this reality we find ourselves in (as do many other far more complex constructs).
And it gets even more complex.
If you search the space of all possible computational and relational systems, then it seems possible to find instances in reality of systems that effectively approximate whatever level of system one is investigating.
It really does in fact seem to be that complex.
Thus science is not “Pursuit of Truth”, but rather something more modest – the instantiation of contextually useful approximations.
From my experience, it seems to be the case, that whatever one is investigating (internal or external) one can find instances of any level of complexity one can imagine – and I have been explicitly imagining multidimensional complexity for over 5 decades, so have experimented with some reasonably complex structures, far beyond my ability to communicate in detail in any reasonable time (decades).
[followed byIs your “expanding space” finite or infinite? If finite, then you necessarily infer a preferred centre. If infinite, no Big Bang. Which way do you want it?]
No – not necessarily so.
What you are displaying is linear 3D thinking.
You are not thinking in terms of curved space.
With a highly curved space, there is no centre, but any direction you go you end up back where you started. So the volume is finite, but there is no preferred centre. Every place is centre with respect to its own frame.
But that does require thinking relativistically, in terms of curved space-time.
When space is highly curved, it doesn’t take long for a particle to return to where it started.
As the curvature reduces, the time taken to go back to start increases. Currently it appears to be a significant multiple of the age of the universe, thus leaving us with a limit of the segment of the universe we can actually observe and interact with, as that being within the “light cone” of the age of the universe.
We are constantly interacting with the unknown, in terms of cosmic background radiation that we could not possibly have had any knowledge of prior to the actual interaction. One of the many unpredictable aspects of reality.
It is not a “common sense” idea.
Relativity is not “common sense”.
Quantum mechanics even less so.
If you get into modelling things, then the interesting things always happen in the phase transition matrices.
I strongly suspect that any phases transition matrix is simply a heuristic when compared to what reality actually does (whatever that actually is). But every model needs phase transition matrices, so we gotta put them in.
But that is precisely what the “big bang” is all about.
The initial conditions of the universe were (seem very likely to have been) a bubble of space-time that was very small, contained a lot of very hot stuff (matter), and was very curved.
As it inflated (as the curvature of space reduced), it got to a point where communication across all space was no longer possible, and differences could be forever isolated from each other (as the space between them was inflating faster than the speed of light).
It is not an easy or common-sense notion to deal with.
And it is kinda possible to imagine in sketch form if you think of 3D space as the surface of a balloon being blown up. The curvature is decreasing on the surface, and the path between any two separate points is getting longer.
Our brains have evolved to deal with 3D space, and don’t easily deal with higher dimensional structures.