Lunar eclipse vs solar eclipse: the difference between the 2 events

The
moon is seen as it begins a total lunar eclipse that will turn
the moon red over Buenos Aires April 15, 2014.
REUTERS/Marcos Brindicci

• A total lunar eclipse, or blood moon, will
  happen overnight on July 27.
• The eclipse is slated to last nearly 1 hour 43 minutes
  — the longest in about a century.
• Total lunar eclipses and total
  solar eclipses are essentially the reverse of one another;
  the difference is the relative positions of the Earth, sun, and
  moon.

A majority of Earth is in for an astronomical treat on Friday:
the longest total lunar eclipse, also known as a blood
moon, in
a century.

At 17:14 Universal Time that night (3:37 p.m. ET), the Earth will
slip directly between the sun and moon, casting an
orange-red shadow on the full moon. From the moon’s vantage
point, the Earth would appear to be surrounded by a
25,000-mile-around
ring of fire.

This event is not to be confused with a total solar
eclipse like the
one that was visible across a swath of the continental US last
summer. 

Total lunar eclipses and total solar eclipses are essentially the
reverse of one another. However, their appearances are very
different.

Here’s what happens during each type of eclipse

During a total solar eclipse, the moon passes between Earth and
the sun, casting a small, dark shadow on our planet. For those
watching on Earth, the moon appears to cover the sun, with a ring
of the sun’s light surrounding the moon. Looking directly at that
light requires special glasses to protect the eyes from the sun’s
brightness.

If you saw the most recent solar eclipse (full or partial),
you’ll remember that the circle of light looks colorless. That’s
because the moon has no atmosphere. Atmospheres, similar to glass
lenses, can refract sunlight.

During a lunar eclipse, however, the Earth passes between the
moon and the sun, casting its shadow — known as the umbra —
onto the moon. During this event, it’s not dangerous
to look up at the moon. 

A
diagram of the Earth, moon, and sun during a total lunar eclipse
or “blood moon.”
Shayanne Gal/Business
Insider

Unlike the moon, Earth is surrounded by a blanket of air, which
refracts the sun’s light in a way that makes the moon appear
orange-red. That’s why lunar eclipses are also called blood
moons.

By volume, about 80% of Earth’s atmosphere is made of nitrogen
gas, or N₂, and most of the rest is oxygen gas, or
O₂. Together, these gases take white sunlight — a mix
of all colors of the spectrum — and scatter around blue and purple
colors. Human eyes are much more sensitive to blues than
purples, which is why the sky looks blue and the
sun yellow to us during daylight hours.

During a sunset or sunrise, sunlight reaching our eyes has passed
through a lot more atmospheric gas, and this effectively filters
out the blues and makes the light appear orange or even red.

A similar thing happens during a lunar eclipse. Earth’s
atmosphere bends and focuses the sun’s light into a glowing,
cone-shaped shadow — the umbra.

The red color is never quite the same from one lunar eclipse to
the next due to natural and human activities that affect Earth’s
atmosphere.

“Pollution and dust in the lower atmosphere tends to subdue the
color of the rising or setting sun, whereas fine smoke particles
or tiny aerosols lofted to high altitudes during a major volcanic
eruption can deepen the color to an intense shade of red,”
David Diner, a planetary scientist at
NASA’s Jet Propulsion Laboratory, wrote in a blog post in 2010.

Where and when to see the total lunar eclipse

If the weather cooperates, most of eastern Africa, the Middle
East, and central Asia should see the full and total lunar
eclipse on Friday. Scientists in Antarctica should also have a
great view.

Europe, eastern Asia, Australia, Indonesia, and other regions
will enjoy a partial lunar eclipse, where the moon passes partly
through Earth’s shadow.

North America will be out of luck, though, since the moon will be
below the horizon.
People there can watch on one of several live webcasts.

A
map of locations where the total lunar eclipse of July 27 and 28,
2018, will be visible.

Fred
Espenak/NASA Goddard Space Flight Center

The partial eclipse begins when the moon first touches the
penumbra or outer shadow of Earth. According to NASA, that should happen at
17:14 Universal Time on July 27.

The total eclipse — when the moon is fully inside the red-hued
umbra of Earth — starts at 19:30 UT and ends at 21:13 UT. That’s
a full 1 hour 43 minutes, which is just four minutes shy of the
longest total lunar eclipse possible, according to
EarthSky.

The partial eclipse will resume immediately afterward, as the
moon passes out of Earth’s shadow, and the whole event will be
over at 23:28 UT (early on July 28, depending on where you live).

The next time a total lunar eclipse will last this long will be
in the year 2123.