Page 44 - Astronomy - October 2017 USA

ASKASTR0 Astronomy’s experts from around the globe answer your cosmic questions.

THE HIDDEN

EARTH

Q: IF ANOTHER PLANET EXISTED THAT WAS
PRECISELY OUR SIZE AND IN OUR EXACT
ORBIT, BUT PLACED BEHIND THE SUN,
WOULD WE HAVE THE MEANS TO DETECT
ITS EXISTENCE? Gary Pyke, McEwen, Tennessee

A: The first person we know to These disparities would
have proposed such a “counter show themselves in the
Earth” was Philolaus, a Greek motions of comets, and in
philosopher who lived in the spectacular ways. Comets
fifth century b.c. In the days appear large, but the actual
before English mathematician bodies are no more than a few
Isaac Newton introduced his miles in diameter. The gravita-
theory of gravitation, a few tional influence of another
other notable philosophers body as massive as Earth Earth is the only planet in its orbit. There can be no other body hidden
brought forth similar ideas. would throw their orbits — from our view on the opposite side of the Sun — the law of gravitation
Today, however, we know that that astronomers calculate with would quickly make such an object known to us. NASA/GSFC/NOAA/USGS
such a world could not remain such precision — into chaos.
undetected for many reasons. So, a counter-Earth would where we could view it directly. with light pillars, they also can
Let’s examine just two of them. affect the motions of all nearby And all the while Mercury, originate with the Moon or
The gravitational influence objects, but the reverse also is Mars, and even Jupiter would even bright terrestrial lights.
of another Earth in that part of true. Let’s take Venus as an be adding their not insignifi- Tiny six-sided ice crystals
the solar system would have a example. It approaches Earth cant influences. slowly falling through the
wide-reaching effect on all as close as 25 million miles Michael E. Bakich atmosphere create the effect.
nearby objects: Mercury, every 584 days. Logically, Senior Editor As they fall, the crystals align
Venus, us, the Moon, Mars, Venus would also approach the themselves parallel to the hori-
and beyond. Over time, astron- counter-Earth that closely. zon, in effect simulating a
omers would be able to detect Venus has about 80 percent of Q: ONE WINTER MORNING colossal mirror made of bil-
the tiny variations in position Earth’s mass, so after even a AS I WAS DRIVING TO lions of individual pieces.
and, using the law of gravita- few dozen passes, Venus’ gravi- WORK, I LOOKED TO THE Wind moving the crystals
tion, quickly calculate the tational influence would move EAST, AND THE SUN WAS causes the reflected light to
source of the problem. the hidden world to a position ABOUT 20° ABOVE THE stretch into a column.
HORIZON. A SOLID BRIGHT You saw the pillar below the
COLUMN OF LIGHT CAME Sun. But pillars also occur that
STRAIGHT DOWN FROM IT are above it or the Moon.
TO THE HORIZON. WHAT Indeed, either of these celestial
CAUSES THIS, WHAT IS IT objects can be below the hori-
CALLED, AND IS THIS zon while still creating pillars.
RELATED TO ANY ARCHAEO- And pillars formed by earth-
LOGICAL FINDS SUCH AS bound lights (which sit on the
THE OBELISKS OF EGYPT? horizon) are always seen above
John Dally the lights.
Colorado Springs, Colorado Indeed, some Egyptologists
believe that Sun pillars were
A: What you saw was an opti- the inspiration for the great
cal effect called a Sun pillar, obelisks created by that culture
also sometimes called a light in the same way that crepuscu-
This Sun pillar was captured about 20 miles (35 kilometers) from Lisbon,
Portugal, on April 26, 2010. The photographer was struck by the pillar’s pillar. And although the Sun is lar rays inspired them to con-
usually the object associated struct the pyramids. For more
height and its white color. MIGUEL CLARO

44 ASTRONOMY • OCTOBER 2017