Perseid Meteors Marred? Blame It On the Moon

Plus, boost your chances of seeing a shooting star

August 9, 2019
Perseids

In this ten-second exposure, a meteor streaks across the sky above Washington, DC during the 2015 Perseids meteor shower.

NASA/Joel Kowsky

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This year, the great Perseid Meteor Shower (peaking August 12–13) will be marred by the sky-brightening mischief of a nearly full Moon. So we may as well amuse ourselves by making the Moon the scapegoat for other problems, too! Read on—plus, here’s a tip to boost your chances of seeing a “shooting star.”

Moon Myths

It’s not a weird idea to think that the Moon causes trouble for us down here on Earth. Folklore has long endowed the Moon with various powers, that are still widely embraced.

  • The word “lunatic” comes from the ancient belief that the Moon could cause mental illness.
  • Others thought crime increased near the full Moon.
  • Because the average menstrual cycle length is 29 days and the lunar cycle lasts 29.5 days, there was a belief that lunar phases influenced the menstrual cycle.
  • Many medical professionals in maternity wings will insist that births increase during the full Moon phase.

However, none of that is true…

  • The full Moon does not foster mental illness; this is confirmed by the utter lack of increased psychiatric hospital admissions during that time. (See article, “Can a Full Moon Affect Your Mood?)
  • And a Dade County (FL) study found no link to crime.
  • Year-long studies have not shown synchrony of lunar phases with the menstrual cycle. If a woman’s cycle happens to be on that sequence (and some are), it’s a coincidence.
  • While medical professionals often report that strange things happen on a full Moon, there is no significant difference in the frequency of births across the eight stages of the Moon.

But recent studies can let us replace those old myths with new lunar powers…

The Moon’s Influence on Tides and Weather

Ocean Tides

Of course, high tides and low tides are caused by the Moon. People have always noticed the Moon’s synchronicity with the timing of the five-foot average rise and fall of the oceans at shorelines around the world.

Tides have a significant effect on the weather, affecting the movement of ocean currents. In turn, this affects the weather through the amount of warming or cooling water moving through a given area.

Ground Surface Tides

The Moon doesn’t only affect ocean tide. The ground itself rises and falls. The Earth’s crust flexes in the direction of the tidal pull. Satellites which can measure the Earth’s topology confirm that the Moon affects the height of the land and puts stress on tectonic faults. Some scientists hypothesize that these shifts might affect earthquakes and even volcanoes.

Air Pressure

And in the 1990s, science confirmed the Moon’s ability to generate an atmospheric tide, a gaseous pulse that creates daily changes in air pressure. It also alters circulation patterns such as the subtropical high pressure belts. These may help explain amazing yet subtle links—recognized for the past half-century—between lunar phase and cloudiness, hurricane formation, and precipitation.

So, the Moon definitely influences the weather.

Lunar phase

Want another effect? At the time of full Moon, the temperature of the lower four miles of atmosphere increases by two hundredths of a degree Fahrenheit. That’s not enough to let you leave your jacket home on moonlit nights, but it does provide new theories to explain the link between weather and lunar phase.

Thunderstorm Activity

Other researchers think the statistical increase in thunderstorm activity observed around the full Moon may be caused by our planet’s magnetic tail undergoing moon-induced distortions. Other theorists suggest clouds are “seeded” by the Moon’s modulation of meteor dust. Studies from 2014 and 2016 confirm a one percent rainfall variation caused by the Moon’s phases and position.

Thermal Action

Back in 1995, University of Arizona investigators surmised that the Moon’s action may be primarily thermal, caused by infrared emission from its hot, 230ºF, sun-lit surface, aimed at us like an electric bathroom heater.

The ability of the Moon to reflect sunlight is minimal because the Moon is one of the least shiny objects in the known universe. It reflects just 10% of the sunlight that strikes it, which matches the reflectivity of an asphalt road. In other words, the Moon is no brighter than if its surface were entirely paved like an enormous mall parking lot. That’s why the full Moon is half a million times less bright than the Sun. It appears white only because of its contrast with the even-darker night sky behind it.

Boost Your Chances of Seeing the Perseids

So the Moon is this month’s scapegoat. A nearly full Moon washes out the Perseid meteors on the peak nights. Still, you could see a dozen or more meteors per hour, including the occasional very bright meteor, also called a fireball.

The best viewing this year will be on the mornings of August 11, 12, and 13. But the Moon will be “in the way” from August 9 through the peak, its brightness washing out most of the fainter Perseids.

To boost your chances of seeing a shooting star this week, here’s what you do:

  1. The bright Moon will set in the early hours (around 3 a.m) before dawn this week. So, you want to watch during the brief window after the Moon sets and before dawn. (Or, start watching when the Moon is low in the west.) Find out the time of your moonset on the Almanac Moon rise/set calculator.
  2. Find a spot away from bright lights and give your eyes a little time to adjust to the darkness. Try to avoid looking at your bright phone screen too. You’ll see more meteors that way.

For the best meteor watching, face toward the east and look up. The Perseids generally appear to radiate from a point here, a bit to the left of the Pleiades star cluster, but they can appear pretty much anywhere on the sky as long as it’s clear. See the Perseid Meteor Shower Guide for more detail.

If cloudy, then it’s not meteor showers but rain showers that we might blame on the Moon. It can’t win!

About This Blog

Welcome to “This Week’s Amazing Sky,” the Almanac’s hub for everything stargazing and astronomy. Bob Berman, longtime and famous astronomer for The Old Farmer’s Almanac, will help bring alive the wonders of our universe. From the beautiful stars and planets to magical auroras and eclipses, he covers everything under the Sun (and Moon)! Bob, the world’s mostly widely read astronomer, also has a new weekly podcast, Astounding Universe

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