The other night my wife and I took an evening stroll and admired the Full Moon reflecting off the scattered clouds. The Sun had set from where we were, but here was a heavenly reminder that the Sun still shines. The thought was expanded when we noticed what looked like a brilliant star to the lower left of the Moon.
That was the planet Jupiter, the solar system’s biggest and a wonderful reflector of the sunlight streaming way past our Earth, past the orbit of Mars and past the main belts of the asteroids.
It seems quite obvious to us that the Sun will rise again; that has been our daily experience, unless of course you live or have visited above the Arctic Circle or below the Antarctic Circle, when it is the winter at the polar cap.
Long before Christopher Columbus and other explorers, there were observant people who realized the world is round. They ascertained that we live on a great rotating ball, and as we spin, the Sun appears to set westward and rise eastward.
When the Sun dips down and sinks below the horizon, and the twilight deepens into true night, we should have no great concern.
We have great faith that it will be back, and sure enough, in a few hours the stars begin to fade and dawn breaks the eastern sky; the great ball of light and heat we know as the Sun, appears once more.
The full Moon is around 246,000 miles further from the Sun than people on the other side of our planet who revel in the noon day sunshine.
Light travels at just over 186,000 miles per second; it takes around an average of 8 minutes and 20 seconds to span the average distance between the Sun and Earth of 93 million miles. It takes another 1.3 seconds to reach the full Moon.
The rugged face of the Moon reflects back some of the light (only 12% at most), and it takes another 1.3 seconds to reach our eyes.
Jupiter is about five times farther from the Sun than our world. At its closest, Jupiter is another 365 million miles from Earth.
Sunlight takes 43 minutes to reach Jupiter; when Jupiter is nearest to Earth, about 35 of those minutes are spent between Earth’s orbit and Jupiter.
The light bounces back off the banded clouds enshrouding the giant planet, and reaches our eyes another 35 or so minutes later when we’re on the same side of the Sun as Jupiter (as we are in the spring of 2019). Jupiter has an albedo of 52%; that’s how much light reflects back.
Light travel gives us the effect of a cosmic time machine; the very stars we see with unaided eyes (let alone a telescope) may be dozens to many thousands of light years away; it takes that long for their light to reach us, giving us a look back in time.
While the Moon and Jupiter (and other planets in our system) comforts us to know the Sun still shines when it is night, the moonlight is 2.6 seconds “old” (35 sec. x 2) and the sunlight we see from Jupiter at least a full 70 minutes (35 min. x 2) from the past!
Pluto is so remote that it takes around 5-1/2 hours for sunlight to reach it, and nearly that amount to come back to our telescopes (Pluto-shine is so dim it takes at least a 10” telescope to catch it)!
I say all this to give another measure of the vastness of even our solar system, let alone our galaxy and beyond. Yet we see the Moon, Jupiter’s bright point of light and that of several other planets when they are in view, as we stroll along. We have a portal to outer space from even our window, or just by stepping outside. All of this is free and ready for our looking, for all who have the gift of sight and heart to appreciate!
Jupiter currently rises in the southeast around the end of evening twilight and is highest in the south at around 2 or 3 a.m. It glows at magnitude -2.5, brighter than any night time star.
Last quarter Moon is on May 26.
Keep looking up!
-- Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at email@example.com. Please mention in what newspaper or web site you read this column.