empty -- 11/25/20
Today's selection -- from Our Universe by Jo Dunkley. Our solar system:
"The Solar System as a whole [is a] loosely defined collection of objects that are centred on our own star, the Sun. We know the Sun extremely well, of course, and the planets that orbit the Sun are also familiar to most people, at least by name. There are also asteroid rocks, comets, dwarf planets, and innumerable pieces of space debris that are drawn towards the Sun and orbit around it.
"Despite all this, the Solar System is astonishingly empty.
"It can be hard to get a good sense of this, as pictures on the pages of a book do not easily capture the true scale of things. A convenient way to imagine the sizes is to shrink the Earth to the size of a small peppercorn, a couple of millimetres across. With the Earth this small, the Sun becomes a basketball, one hundred times larger from side to side. If we now put the basketball -- Sun down and work out where Earth should be, we might expect it to be fairly nearby. But you would need to walk twenty-six large paces to reach the peppercorn -- Earth, the full length of a tennis court. In between the real Earth and the Sun there are just two tiny planets, Venus and Mercury. Mercury would be ten paces from the Sun in this model, and peppercorn-sized Venus nineteen.
"To reach our outer planetary neighbours starts to require some serious walking. Mars, a half-peppercorn-sized planet like Mercury, would be fourteen more paces past Earth. The largest planet, Jupiter, a large grape to Earth's peppercorn, would be almost 100 paces further. Jupiter is five times further from the Sun than Earth, or five tennis courts laid end to end. A little over another hundred paces on comes Saturn, an acorn, now ten times as far from the Sun as Earth. Uranus is twenty times and Neptune thirty times further than the Earth from the Sun. Tiny Neptune, like Uranus about the size of a raisin, is now almost half a mile away from our basketball-Sun, almost 800 paces and a roughly ten-minute walk. You could hold all those planets comfortably in your hand; the rest of the Solar System is almost entirely empty."
Take a tour through our solar system here -- https://solarsystem.nasa.gov/solar-system/our-solar-system/overview/