The Astronomy Book

268

MOST OF THE

UNIVERSE IS

MISSING

ARK MATTERD

I

saac Newton’s universal law

of gravitation is adequate for

making calculations to launch

a satellite into orbit, land a crew on

the moon, and send a spacecraft

on a grand tour of the planets.

Newton’s clear mathematics works

well enough for most things on

the solar system scale, but not

on grander scales of the universe,

where Einstein’s relativistic theory

of gravity is needed (pp.146–53).

Nevertheless, Newton’s law of

gravitation was all that was required

to reveal one of the biggest—and

as yet unsolved—mysteries of

astronomy: dark matter. In 1980,

American astronomer Vera Rubin

presented clear evidence that dark

IN CONTEXT

KEY ASTRONOMER

Vera Rubin (1928–)

BEFORE

1925 Bertil Lindblad

calculates the likely

shape of the Milky Way.

1932 Jan Oort finds that

the rotational speeds of the

Milky Way galaxy do not

match the presumed mass.

1933 Fritz Zwicky suggests

that a majority of the

universe is made up of

dark, invisible matter.

AFTER

1999 It is discovered that

dark energy is accelerating

the expansion of the universe.

2016 The LIGO experiment

detects gravitational waves,

which offer a new method to

map the distribution of dark

matter across the universe.