QQQ has huge tech exposure, but it is not a 'tech fund' in the pure sense either. The fund's arcane weighting rules further distance it from anything close to plain vanilla large-cap or pure-play tech coverage.
During the time when Earth was forming and was in a molten state, heavy materials like iron and nickel sank to the center of the Earth's mass and lighter materials floated to the surface of the mass. The very center of what we call the core, is solid in the middle because of the increased pressure in that region.
The Core's Gross Shape. We knew by the 1890s, from the way Earth responds to the gravity of the Sun and Moon, that the planet has a dense core, probably iron. In 1906 Richard Dixon Oldham found that earthquake waves move through the Earth's center much slower than they do through the mantle around itâbecause the center is liquid. In 1936 Inge Lehmann reported that something reflects seismic waves from within the core. It became clear that the core consists of a thick shell of liquid ironâthe outer coreâwith a smaller, solid inner core at its center. It's solid because at that depth the high pressure overcomes the effect of high temperature.