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\f0\fs24 \cf0 A hundred years ago, most astronomers believed the universe consisted of a grand
disk, the Milky Way. They saw stars, like our own sun, moving around it amid giant regions
of dust and luminous gas. \ \
The overall size and shape of this "island universe" appeared static and unchanging.\
\ That view posed a challenge to Albert Einstein,
who sought to explore the role that gravity, a dynamic force, plays in the universe as
a whole. \ \
There is a now legendary story in which Einstein tried to show why the gravity of all the stars
and gas out there didn't simply cause the universe to collapse into a heap. \
\ He reasoned that there must be some repulsive
force that countered gravity and held the Universe up.\
\ He called this force the "cosmological constant."
Represented in his equations by the Greek letter Lambda, it's often referred to as a
fudge factor.\ \
In 1916, the idea seemed reasonable. The Dutch physicist Willem de Sitter solved Einstein's
equations with a cosmological constant, lending support to the idea of a static universe.\
\ Now enter the American astronomer, Vesto Slipher.
Working at the Lowell Observatory in Arizona, he examined a series of fuzzy patches in the
sky called spiral nebulae, what we know as galaxies. He found that their light was slightly
shifted in color.\ \
It's similar to the way a siren distorts, as an ambulance races past us. \
\ If an object is moving toward Earth, the wavelength
of its light is compressed, making it bluer. If it's moving away, the light gets stretched
out, making it redder. \ \
12 of the 15 nebulae that Slipher examined were red-shifted, a sign they are racing away
from us.\ \
Edwin Hubble, a young astronomer, went in for a closer look. Using the giant new ***
telescope in Southern California, he scoured the nebulae for a type of pulsating star,
called a Cepheid. The rate at which their light rises and falls is an indicator of their
intrinsic brightness. \ \
By measuring their apparent brightness, Hubble could calculate the distance to their host
galaxies.\ \
Combining distances with redshifts, he found that the farther away these spirals are, the
faster they are moving away from us. This relationship, called the Hubble Constant,
showed that the universe is not static, but expanding.\
\ Einstein acknowledged the breakthrough, and
admitted that his famous fudge factor was the greatest blunder of his career. \
\ }