Super Blood Moon

The confluence of three celestial phenomena happen tomorrow evening:

• a full moon;
• a supermoon; and
• a total lunar eclipse.

The last supermoon eclipse occurred in 1982.

Celestial phenomena are predictable because we have studied and understand planetary movements in the solar system.

Nothing comes close to the precision with which physics enables you to understand the world around you. It's the laws of physics that allow us to say exactly what time the sun is going to rise. What time the eclipse is going to begin. What time the eclipse is going to end.
― Neil deGrasse Tyson

Blood Moon
source: Anne Dirkse

Full moon

Tomorrow's full moon will be both a harvest moon and a blood moon.

A harvest moon is the full moon that falls closest to the fall equinox, which was last Wednesday.

A blood moons describes the red-tinted moon observed during a lunar eclipse. During a lunar eclipse, sunlight directed around the edges of the Earth refracts through Earth's atmosphere filtering out all but red, giving the moon its blood red tint.

Supermoon

Tomorrow's full moon will be a supermoon, or the full moon in perigee.

The moon orbits Earth in an elliptical path meaning that the distance between Earth and moon varies over an orbital cycle, giving us supermoons and micromoons.

A supermoon compared to a micromoon
source: Friends of NASA

Supermoons occur when the moon's orbital path transports it to the closest point to Earth. Micromoons occur when the moon is at its farthest point from Earth. A supermoon is about 31,000 miles closer to the Earth than a micromoon.

The closer proximity of a supermoon makes it appear 14% larger and 30% brighter.

The stronger gravitational pull of the supermoon causes wider variation in high and low tide levels.

Lunar Eclipse

Tomorrow's full moon will undergo a total eclipse.

Tomorrow night, the Earth will line up between the sun and the moon. The moon will gradually move into the shadow of the earth until it falls into darkness (i.e, a total eclipse).

Lunar eclipse
source: Luca

Under clear skies, tomorrow's lunar eclipse should be visible from longitudes stretching from the eastern Pacific to western Asia, including the Americans, Europe, and Africa.

Three things cannot be long hidden: the sun, the moon, and the truth.
― Gautama Buddha

The next supermoon eclipse occurs in 2033.

REFERENCES

• Rare supermoon eclipse comes Sunday, Jareen Imam, CNN, 25 September 2015.
• Super Blood Moon eclipse on night of September 27-28, Bruce McClure, EarthSky.
• Supermoon, GrokEarth, 12 July 2014.

Supermoon

Supermoons occur tonight July 12^th, and again on August 10^th and September 10^th of 2014.

Show Don't Tell

Oft quoted writing advice from Anton Chekhov to his brother has been paraphrased as:

“Don't tell me the moon is shining; show me the glint of light on broken glass.”

Chekhov advised his brother, an aspiring writer, to "show, don't tell" which has become a guiding principle of writing. Show don't tell might be extended to scientific phenomena like the supermoon.

Elliptical Orbit

The moon orbits the earth in an elliptical path. Unlike a hypothetical circular path where the moon would always be equidistant from the earth, the moon's elliptical path means the distance between the earth and the moon varies over an orbital cycle.

The supermoon, or a full moon at perigee, is a phenomenon that occurs when the moon's orbital path transports it to its closest point to the Earth. The terms perigee and apogee describe the shortest and longest distance between the earth and the moon.

Full Moon at Perigee

A full moon at perigee would, by comparison, appear about 12-14% larger than the full moon at apogee because it is closer. If you held a ball at arm's length then brought it to your nose, the same ball would appear larger. Similarly, the full moon at perigee might appear larger, but only if we have a reference to compare it to ― like side-by-side images of full moons at perigee and apogee.

It's not what you look at that matters, it's what you see.
― Henry David Thoreau

Apparent Size Difference by Observers of the Full Moon at Perigee and Apogee

Super Moons and Natural Disasters

The moon has less gravitational pull when it is at apogee (farthest from earth) than when it is at perigee (closest to earth). The gravitational pull of the moon influences tides. The stronger gravitational pull of a moon at perigee leads to higher variation in the high and low tide levels.

Despite these gravitational variations, science hasn't established a definitive correlation between a full moon at perigee and its attendant gravitational pull, and the occurrence of natural disasters like earthquakes, floods, and volcanic eruptions.

"I think you'd be hard pressed to see a difference in tectonic activity during different lunar phases."
― William Burton, USGS Research Geologist

Lunar phases seem to have no discernible influence on seismic activity, weather patterns, or volcanic activity.

"This idea of blaming natural disasters on the phases of the moon goes way back to the Greeks. It has been around for hundreds and hundreds of years."
― Malcom Johnston, USGS Scientist Emeritus

Nearly Full Moon at Perigee
image by Cindy Gipple

Three things cannot be long hidden: the sun, the moon, and the truth.
― Guatama Buddha

REFERENCES

• A trio of Super Moons is gracing our summer skies, by Scott Sutherland, The Weather Channel, 11 July, 2014.
• Apogee and Perigee of the Moon, MoonConnection.com.
• Don’t Tell Me the Moon Is Shining; Show Me the Glint of Light on Broken Glass, Quote Investigator.
• No Link Between 'Super Moon' and Earthquakes, by Rachel Rice, Discovery, 27 November 2012.
• ScienceCasts: A Summer of Super Moons, Science at NASA, 8 July 2014.
• Supermoon, Wikipedia.
• Supermoon rising over Earth this weekend, RT.com, 11 July, 2014.