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visible to any creatures inhabiting our galaxy. The galaxies included in this view are M77 located uppred

In the past, astronomers have theorized the expansion of the universe would slow and reverse, compressing all matter back in a "Big Crunch." Others said the expansion would continue forever and we would see the stars in all the galaxies age and die, leaving Earth in darkness.

Image: Seen from the outskirts of our own Milky Way Galaxy, at lower left in this artist rendering, seven billion years from now the Universe will appear frozen in time as we look out onto space. Only the light from the local group of galaxies will remain visible to any creatures inhabiting our galaxy. The galaxies included in this view are M77 located upper left, M33 upper center, M74 lower left of M33, M31 lower right center, and NGC 147, lower right. Click image to enlarge.

But now, a calculation by Professor Abraham Loeb, a theoretical astrophysicist at the Harvard-Smithsonian Center for Astrophysics, paints a different picture regarding the fate of the universe, and it looks quite lonely. As the universe ages and expands, fewer and fewer galaxies will be visible from Earth. Even weirder, as we watch the galaxies fade, their appearance will freeze in time. They will never grow older or change. They will only grow dimmer as they recede from us.

These results are the consequence of Einstein's general theory of relativity, combined with current knowledge of the parameters of the universe. Studies of distant exploding stars have shown that the expansion of the universe, rather than slowing down from the inexorable pull of gravity, instead is speeding up under the influence of a vacuum energy dubbed "the cosmological constant." Eventually, distant galaxies will simply be moving too fast to see.

Over the next 100 billion years, this accelerating force will shrink the cosmic horizon, reducing the number of visible galaxies to only about a thousand members of the local Virgo Cluster and surrounding areas. As distant galaxies cross the horizon, their image will be frozen. The light they emit after the moment of horizon crossing will never be able to reach us.

"This process is analogous to what you see if you watch a light source fall into a black hole," states Loeb. "As an object crosses the black hole's event horizon, its image seems to freeze and fade away because you can't see the light it emits after that point."

Similarly, distant galaxies will freeze into an unchanging vista. New stars being born or old stars dying will not be visible. The galactic snapshots will simply fade away to invisibility.

This has grim consequences for study of the universe. Not only will the number of visible galaxies shrink away, but the evolution of these galaxies later in their history will be invisible as well. The amount of information available about the distant universe is finite. For example, light from the most distant quasar yet seen, left that quasar when the universe was only a billion years old. The universe is now estimated to be 14 billion years old.

Loeb's calculations show that in the next several billion years, it will freeze at an age of six billion years and stop changing. Its frozen image will only grow fainter as the universe expands.
Source: Harvard-Smithsonian Center for Astrophysics

Image: Seen from the outskirts of our own Milky Way Galaxy, at lower left in this artist rendering, seven billion years from now the Universe will appear frozen in time as we look out onto space. Only the light from the local group of galaxies will remain visible to any creatures inhabiting our galaxy. The galaxies included in this view are M77 located uppred