The moon on Wednesday could still seem huge, but for a different
reason.
You'll probably hear the news on Wednesday, August 30, stating that we'll
get a chance to see a "supermoon" that night. It's a phrase, or more
precisely, a branding, that has only recently come into use. It was
initially used by an astrologer, who arbitrarily defined it as "a full moon
that occurs with the moon at or near (within 90% of) its closest approach to
Earth in a given orbit" rather than from astronomy.
In fact, the moon will reach perigee at noon ET on the fifth Wednesday of
August, when it will be 221,942 miles (357,181 km) from Earth, the closest
point in its orbit. And the moon will become formally full 9 hours, 36
minutes later. Despite the fact that a full moon only lasts for a little
period of time, that moment is unnoticeable to ordinary observation,
therefore for a day or two before and after, most people would refer to the
nearly full moon as being "full": It is difficult to determine if the shaded
strip is present or which side it is with the naked eye since it is so thin
and changes in apparent breadth so slowly.
In addition to being a "supermoon," this particular full moon will also be
the second to happen in August, with the previous having been on August 1.
The second full moon of August, which occurs on the 30th, will thus also be
referred to as a "Blue" moon. For what it's worth, we will thus see a "Super
Blue Moon."
However, the moon won't look blue unless there is an exceptional
atmospheric condition, such airborne dust, ash, or smoke; instead, it will
look its typical yellow-white self. Nevertheless, many people will probably
look forward to seeing this large late summer moon because of the
exaggeration in the mainstream media.
If you're hoping to see the full moon, our guide to the finest binoculars
could be able to point you in the direction of some great wide-angle lenses
for capturing more of the lunar surface. Alternatively, our guide to the
best telescopes can help you discover the equipment you need if you want to
get a closer look at the moon's characteristics.
Additionally, if you want to capture the moon or the night sky in general,
see our articles on the finest astrophotography equipment, including the
best astrophotography cameras and lenses.
For you, this deluge
However, there is a downside: As a result of the full moon almost occurring
at the same time as perigee on August 30, the range of tides will be
significantly wider than usual for many days around August 30. Low tides
will be abnormally low and high tides will run extremely high, maybe even
causing some coastal flooding.
A perigean spring tide is one of these extremely high tides; the term
spring is derived from the German springen, which means to "spring up," and
is not, as is sometimes believed, a reference to the spring season. Spring
tides happen each month when the moon is both full and new. The Earth forms
a line with the moon and the sun at these periods, combining their tidal
effects. (The sun produces somewhat less tidal force than the moon.) The
moon's first and final quarters, on the other hand, cause "neap tides,"
which occur when the sun and moon are in opposition to one another. The
tides are weak right now.
The inverse cube of an object's distance is how the tidal force fluctuates.
The moon is 14% closer on Wednesday at perigee than at apogee. The spring
tides on August 30 therefore had a 48 percent more tidal force than the
spring tides near apogee on August 16, which occurred two weeks
earlier.
Additionally, if a large storm or hurricane is offshore and it interacts
with the already high water levels, the results might result in choppy seas,
beach erosion, and serious floods.
While it should be noted that the typical Atlantic hurricane season peak
occurs less than two weeks later, on September 10, we can only pray that
such weather conditions do not materialize this year.
Branding for Supermoon has "watered down"
Astronomers have long referred to a full moon that occurs at perigee as a
"perigean full moon." a word with little to no publicity.
Now it seems that a full moon that occurs at the same time as perigee is
always referred to as a "supermoon." In reality, the moon becoming full
within hours of it reaching perigee is not truly such an uncommon
occurrence; some newscasters just refer to it as "rare" in an apparent
attempt to keep your attention.
In actuality, it happens about every 413 days or so on average.
The next Wednesday, this will not occur again until October 17, 2024.
However, the full moons of August 1 (approximately 11 and a half hours
before perigee) and September 29 (about 33 hours after perigee) are also
being referred to as supermoons, presumably because they are within 90% of
the moon's closest approach to Earth. Or, to put it another way, in the top
10% nearest full moons for a particular year.
As a result, we now often experience four "supermoons" rather than just
one. There may only be two some years, but there may be as many as five
other years.
But how "super" or "rare" is it exactly?
Expectations that are too high: larger?
While the moon on Wednesday will be the "largest full moon of 2023,"
according to the Observer's Handbook of the Royal Astronomical Society of
Canada (14% larger in apparent size compared to a full moon at apogee — its
furthest from Earth), the variation in the moon's distance is not
immediately noticeable to observers viewing the moon directly.
So, if you go outdoors on Wednesday night to gaze at the moon and hope to
see something remarkable, you probably won't. Before every "Supermoon,"
there are a ton of pictures uploaded to the internet showing really enormous
full moons that were all captured with telephoto lenses. These pictures all
give the impression that the moon will seem incredibly large in the
sky.
In fact, most people probably wouldn't notice any distinction between
Wednesday's full moon and any previous full moon if they were unaware of its
impending proximity. Similar to how the expression "emperor's new clothes"
has become an idiom regarding logical fallacies, however, once the
"supermoon" notion is offered, these same folks will walk outside, look up,
and claim that the moon does appear to be far larger than usual.
Brighter?
The brightness of the moon is another problem. According to websites, the
"supermoon" will be "30 percent brighter than other full moons." However, it
really amounts to a negligible rise of fewer than three tenths of a
magnitude, so Wednesday night's moonlight won't be very brilliant.
However, there are probably some people who believe they will see an
especially brilliant full moon that night. When the "supermoon" of 2013
occurred, a friend of mine predicted that it would appear "radically
brighter," "like with those 3-way light bulbs; I thought it was going to be
like turning the moonlight up a notch."
Instead, there was no noticeable difference in the moon's brightness from
prior nights.
The moon illusion might still be present on Wednesday, but for a different
cause.
The perigee moon might look large when it is near to the horizon. At that
point, reality and the well-known "moon illusion" come together to create a
truly breathtaking spectacle. When hovering close to trees, houses, and
other foreground objects, a low-hanging moon appears very huge for reasons
that neither astronomers nor psychologists entirely understand.
On Wednesday, the moon will be much closer than normal, which will only
help to accentuate this peculiar effect.
Therefore, a perigee moon may appear to be so close that you could
practically touch it when it is rising in the east at sunset or setting in
the west at daybreak. By first recording the timings for moonrise and
moonset for your location on this
U.S. Naval Observatory
webpage, you may verify this for yourself.
Do not ignore Saturn!
In the sky, a full moon is situated across from the sun. It turns out that
the planet Saturn will arrive at opposition to the sun, when it too is
opposite the sun in the sky, three days before the moon reaches this point
in the sky. Saturn will thus "photobomb" the moon on Wednesday night since
it is around 5.5 degrees to its upper right.
Naturally, Saturn will be located 814.6 million miles (1.31 billion km) or
73 light minutes from Earth, making it significantly further away than our
nearest neighbor. The ringed marvel will appear as a subdued yellow-white
"star." The well-known rings will be angled 9 degrees toward Earth and may
be seen via small spotting scopes with a minimum 25-power magnification or
powerful binoculars.
Thus, we at Space.com wish you everyone bright, moonlight skies, however
you choose to see Wednesday's full moon.
