Galaxies How do we get such beautiful, ornate, and symmetrical shapes of galaxies — pinwheels, ovals, spirals, and central bars — when the same gravitational forces are at work as those that affect Earth and the Sun’s other planets?
Galaxies Besides computer simulations, what evidence do astronomers have to support the popular hypothesis that elliptical galaxies form from merging spirals?
Solar System I keep reading about Mars meteorites found on Earth. How do scientists know they came from Mars without samples of martian rocks to compare them?
