Such asteroids would rapidly have adopted orbits that cut across those of the inner planets, including Earth.

ECONOMIST: Asteroid impacts

Chen Ningning built an early fortune in the steel business but now most of her fortune lies in publicly traded Inner Mongolia Baotou Steel Rare-Earth Group, where she is an investor (not an executive).

FORBES: How China's Self-Made Women Billionaires Earned Their Fortunes

Early of the Lawrence Livermore National Laboratory, California, proposed siting a vast, 2000 km-wide glass deflecting panel at the "inner Lagrange point" between the Earth and the sun, the latter diverting the sun's rays away from the Earth's atmosphere.

CNN: The shield of Ra: Could solar reflection save the planet?

And the hole's outer edge is roughly where rocky planets, like the inner planets of this solar system (including the earth), are expected to be.

ECONOMIST: Dusty genesis

From the beginning until the end of his series of talks he conveyed an inner certainty that America was the most interesting country on earth, and many Britons who had never thought so before were persuaded to agree with him.

BBC: Magazine

The inner belt normally extends from about 1, 000 miles above Earth to 8, 000 miles.

MSN: Twin satellites will study radiation around Earth

The inner core, made of very pure, solid iron, rotates along with the outer core, dragging the Earth's magnetic field with them.

BBC: Earth's wobbles reveal deep secrets

Without it such a galaxy's outer parts would spin more slowly than the inner ones (just as the outer planets of the solar system move around the sun more slowly than the earth does).

ECONOMIST: The galactic gourmand