Week of Nov. 10-16, 2019
Nothing in the heavens appears as it is. It really is quite an illusion we experience nightly.
When folks learn the immense distances of the stars and how long their light requires to reach Earth, they wonder if astronomers are bothered that stars and galaxies do not appear as they are now but only as they were long ago.
The answer is a simple, "No, we're not." In fact, the greater the distances — and, therefore, the further back into time — that we can peer, the happier we are, because this enables us to see how the stars, galaxy and universe appeared in the distant past. If all we could see were light from today, we'd never learn how things have evolved over time.
Geologists and paleontologists use this technique frequently. The deeper into a canyon they go, for example, the older the sediment layers they find and, from these, they can learn about the history of our planet and its diverse, ever-changing life forms.
So, in a sense, the heavens are a great backyard time machine, and traveling to distant eras is as easy as stepping outdoors and looking up. And over the next few weeks, we'll have a great opportunity to begin our journey through time and space with one of the most famous of all nighttime star groupings: the Summer Triangle.
The Summer Triangle (so-called because it first appears in the eastern sky during early evenings of summer) is outlined by three bright stars: Vega, Deneb and Altair. Though these three stars appear roughly the same brightness, they are not the same distance from us. In fact, they're separated by tremendous distances. This is because they are different types of stars.
Altair lies about 100 trillion miles (nearly 17 light-years) from us. In other words, its light has been traveling through space for 17 years. This means that its photons of light that strike our eyes tonight have been traveling through space since the year 2002.
Vega, on the other hand, lies nearly 50% farther away than Altair — at a distance of about 147 trillion miles (25 light-years). And Deneb lies some 8,200 trillion miles (around 1,400 light-years) away — so far that we see it as it appeared in the seventh century. The light that leaves that star tonight won't arrive here until the 35th century!
Just as the light of these stars takes time to reach Earth, light from our world takes time to reach them. Imagine, for example, if astronomers living on a world orbiting Vega had telescopes powerful enough to observe activity on our planet; they would see us as we were in 1994.
They might be watching right now as the Winter Olympics take place in Lillehammer, Norway, or as O.J. Simpson makes his slow-speed getaway on a Los Angeles freeway. And they would surely be scratching their little green heads over such unusual characters as Ren & Stimpy, Forrest Gump and Al Bundy.
The next time you gaze skyward on a clear dark night, think about all the amazing events that have taken place on our planet during these long journeys of starlight.
Visit Dennis Mammana at facebook.com/DennisMammana. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.