The 13th century Venetians glass blowers are known to have produced reading stones made of solid glass that was put into hand-held, single lens-type frames made of horn or wood. These reading stones were similar to hand-held magnifying lenses of today.
The stronger the magnetic field, the larger the magnetosphere. Some 20,000 times stronger than Earth's magnetic field, Jupiter's magnetic field creates a magnetosphere so large it begins to avert the solar wind almost 3 million kilometers before it reaches Jupiter. The magnetosphere extends so far past Jupiter it sweeps the solar wind as far as the orbit of Saturn.
With a gigantic ball of solid metal as its core, all of Earth is magnetic. Scientists believe Earth's powerful magnetic field is controlled by the liquid outer core. Earth's magnetic field protects us from all sorts of charged particles floating around the solar system, including many of the Sun's harmful rays. Although it might be hard to imagine. scientists believe the metals in Earth's core are in