It's Damn Big

The spring evening is crisp and cool and pitch-black. Stars fill the sky in a glittering tapestry that goes unnoticed by the occupants of a car speeding down the rural highway, far from city lights and traffic. Dimly at first, the headlights reveal a steep hill ahead. Without losing speed, the automobile hurtles upward and reaches the crest, and for an instant, the headlamps shine into the blackness like two ghostly fingers. That instant marks freedom for at least one photon of light which avoids bumping into dust motes or being absorbed by molecules of air on its way up from the Earth's surface. Less than two seconds later, it passes the Moon. One minute after that, Earth and Moon diminish to star-like points. Within an hour, they fade into the starry backdrop. One month away from Earth, the photon is so remote that all the planets are invisible and the Sun dwindles to a star, although still far brighter than any other. In two years, the Sun is reduced to a bright but not extraordinary star.

Over the next 50 years, the Sun slowly fades until it is dimmer than the faintest stars visible to the unaided eye. Yet the sky still appears basically as it does from Earth and has the same overall proportion of bright and dim stars. But by the hundreth year of travel, a distinct thinning out of stars becomes apparent ahead. The photon is moving out of the Milky Way Galaxy.

After cruising in its arrow-straight trajectory for 2,000 years, the photon is completely outside and well above the spiral arm of the galaxy where our solar system resides. From this vantage point, only a handful of stars speckles the sky. But the view back toward the galaxy reveals an impressive panorama: the sweeping curves of the spiral arms and, beyond them, the bulging galactic nucleus.

Continuing its voyage for another 22,000 years, the photon nears a mammoth swarm of stars, the Hercules Cluster, a million suns congregated in a rough sphere about 75 light-years across. This is one of more than 150 globular clusters that orbit the Milky Way Galaxy like satellites.

The photon races onward, but the scenery becomes less inspiring with each millenium as the Milky Way fades to a tiny puff in the blackness. Only one additional galaxy, Andromeda, is easily visible; other galaxies appear as mere smudges. After 10 million years, both the Milky Way and Andromeda are lost to view. Millions more years will pass before chance encounters with other galaxies break the monotony of the void. And the journey has just begun.

People, nothing inspires my writing more than the magic that is Cosmology......