Having lighter materials in their cores has nothing to do with their mass or pressure. This is due to the outer Solar system being much more deficient in heavier elements, so there are primarily only lighter elements to work with. Also, due to their mass they can hold a much higher proportion of gases (in the astronomical sense) than smaller worlds, giving them an even greater proportion of light elements to heavy ones. However the densest materials would still collect at their centers.

Diamond is composed of carbon, a relatively light element. Diamond cores/planets would form only on planets composed largely of carbon.

That hypothesis is complete fantasy and based on nothing more than a fantasy. Plus if the core were lighter materials there would be no magnetic field

Yes, please ignore Jupiter who's Core is Hydrogen (the lightest element by a factor of 4) and has a magnetic field over 10 times the strength of Earth.

Metallic hydrogen is a state of hydrogen in which it behaves as electrical conductor. This state was predicted theoretically in 1935, but has not been reliably produced in the laboratory experiments due to the requirement of high pressures, on the order of hundreds of gigapascals. At these pressures, hydrogen might exist as a liquid rather than solid. Liquid metallic hydrogen is thought to be present in large amounts in the gravitationally compressed interiors of Jupiter, Saturn, and some of the newly discovered extrasolar planets.

Yes, please ignore Jupiter who's Core is Hydrogen

Perhaps not, likely the gravity would keep increasing until halfway where the effect of gravity would tamper off until the centre of the earth is reached.

BTW, I object to the post being moved to the conspiracy thread, the original reply was made in a gaming thread where I backed up a comment where gravity would be too great for large creatures. Hardly call this conspiracy.

Jupiter's core is not hydrogen (it might be, but most models indicate that it is actually rocky, and if it isn't it would be due interior processes having taken place after formation, which would be specific to very high mass planets and thus not applicable to Earth). You are thinking of the interior regions surrounding the core, which are liquid metallic hydrogen. It is because the hydrogen is in this special state that the magnetic field can exist.

Also, I would like to point out that the amount of mass added to the Earth by neutrino accretion is negligible, and is outclassed by many orders of magnitude by the amount of mass gained via collection of space dust and meteoroid debris (which if I remember correctly is something like 400 tons per day).

"BBC recently asked physicist and Cambridge University professor Dave Ansell to draw up a balance sheet of the mass that's coming in to the earth, and the mass going out to find out if the earth is gaining or losing mass. By far the biggest contributor to the world's mass is the 40,000 tonnes of dust that is falling from space to Earth every year. 'The Earth is acting like a giant vacuum cleaner powered by gravity in space, pulling in particles of dust,' says Dr. Chris Smith. Another factor increasing the earth's mass is global warming which adds about 160 tonnes a year because as the temperature of the Earth goes up, energy is added to the system, so the mass must go up. On the minus side, at the very center of the Earth, within the inner core, there exists a sphere of uranium five mile in diameter which acts as a natural nuclear reactor so these nuclear reactions cause a loss of mass of about 16 tonnes per year."

To the point: if you have actual evidence to support this "expanding Earth" hypothesis, present it.

On the minus side, at the very center of the Earth, within the inner core, there exists a sphere of uranium five mile in diameter which acts as a natural nuclear reactor so these nuclear reactions cause a loss of mass of about 16 tonnes per year.

I thought the establishment claims the earth is still cooling down from the frictional heat generated at it's creation.

I think the best evidence is the way the continents match together on a smaller globe.

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Perhaps not, likely the gravity would keep increasing until halfway where the effect of gravity would tamper off until the centre of the earth is reached.

Of course it would, no one disputes that. That does not change the fact that the force of gravity always pulls towards the center wherever you are, which is what causes differentiation in the first place.

Lastly, since nobody appears to have said it yet, what killed the dinosaurs (as well as about 75% of all species...) was an impact event with an asteroid. There is extremely compelling evidence supporting this, which includes the remnant of the impact crater (the Chicxulub Crater)

But my guess would be that it was probably both the asteroid and the volcano at the same time.