HOW OLD IS THIS WORLD In contrast, the universe seems to be about 13.8 billion years old. Scientists reached that number by measuring the age of the oldest stars and the speed of expansion of the universe. They also measured the details by observing Doppler changes in light from galaxies, almost all of which are moving away from us and from each other. The farther away the galaxies are, the faster they are traveling. Gravity is expected to slow down the galaxies from each other, but instead they are increasing rapidly and scientists do not know why. In the distant future, galaxies will be so far away that their light will not be visible from the earth.
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