Lunar Eclipse 101 | National Geographic

Summary

A lunar eclipse occurs when the Earth blocks sunlight from reaching the Moon during a full moon, which happens every 29.5 days. Due to the Moon's tilted orbit, eclipses don't happen monthly. There are three types: total, partial, and penumbral. Total eclipses cast a reddish glow on the Moon due to Earth's atmospheric refraction. Lunar eclipses can be observed from the night side of Earth and are safe to view with the naked eye. As the Moon slowly moves away from Earth, future total lunar eclipses may become less frequent.

Takeaways

• 🌕 A lunar eclipse occurs when the Earth blocks some or all of the Sun's direct light from reaching the Moon.
• 🌒 Lunar eclipses only happen during a full moon, which occurs approximately every 29.5 days.
• 🌎 The Moon's orbit is tilted, preventing a lunar eclipse from happening every month.
• 🌗 There are two types of Earth's shadows: the larger penumbra and the smaller, darker umbra.
• 🌑 There are three types of lunar eclipses: total, partial, and penumbral.
• 🔴 A total lunar eclipse gives the Moon a sunset red color due to the refraction of red light by Earth's atmosphere.
• 🌑 A partial lunar eclipse happens when only part of the Moon passes into the Earth's umbral shadow.
• 🌘 A penumbral lunar eclipse is subtle and causes the Moon to appear slightly darker than normal.
• 🌌 Lunar eclipses can be observed from the entire nighttime half of the Earth and are safe to view with the naked eye.
• 🌙 The Moon is gradually moving away from Earth, and in the distant future, it may no longer be close enough for total lunar eclipses to occur.

Q & A

What is a lunar eclipse?

A lunar eclipse occurs when the Earth blocks some or all of the sun's direct light from reaching the moon.

Why does a lunar eclipse only happen during a full moon?

A lunar eclipse happens during a full moon because that's when the moon is on the opposite side of the Earth from the sun, allowing the Earth to cast a shadow on the moon.

Why don't we have a lunar eclipse every month?

We don't have a lunar eclipse every month because the moon's orbit is tilted a few degrees relative to the Earth, so the Earth, moon, and sun don't always align perfectly.

What are the two types of shadows the Earth casts on the moon during an eclipse?

The Earth casts two types of shadows on the moon during an eclipse: the penumbra, which is a larger shadow, and the umbra, which is a smaller, darker shadow.

What is the difference between a total lunar eclipse and a partial lunar eclipse?

In a total lunar eclipse, the moon falls entirely within the Earth's umbral shadow, while in a partial lunar eclipse, only part of the moon passes into the umbra.

Why does the moon appear red during a total lunar eclipse?

During a total lunar eclipse, the moon appears red because the Earth's atmosphere scatters shorter blue wavelengths of light and refracts longer red wavelengths toward the moon.

How does volcanic activity affect the color of the moon during a total lunar eclipse?

Volcanic activity can block out enough light to render the moon a darker red or even near black during a total lunar eclipse due to the ash in the atmosphere.

What is a penumbral lunar eclipse and why is it less noticeable?

A penumbral lunar eclipse occurs when the moon passes through the Earth's penumbral shadow, and it is less noticeable because the moon appears only slightly darker than normal.

How often can lunar eclipses occur in a year?

Lunar eclipses can occur up to three times a year.

Is it safe to look at the moon with the naked eye during a lunar eclipse?

Yes, it is safe to look at the moon with the naked eye during a lunar eclipse, unlike a solar eclipse.

Why will lunar eclipses eventually become impossible to witness?

Lunar eclipses will eventually become impossible to witness because the moon is inching away from the Earth each year, and billions of years from now, it will be too far away to fall completely within the Earth's umbral shadow.

Outlines

00:00

🌕 Understanding Lunar Eclipses

A lunar eclipse occurs when the Earth blocks the direct sunlight from reaching the Moon during a full moon, which happens every 29.5 days. The Moon's orbit is tilted, preventing perfect alignment with the Earth and Sun every month. During an eclipse, the Earth casts a penumbral and umbral shadow on the Moon. There are three types of lunar eclipses: total, partial, and penumbral. A total lunar eclipse, where the Moon enters the Earth's umbral shadow, turns the Moon red due to the scattering of shorter blue wavelengths and the refraction of longer red wavelengths by the Earth's atmosphere. The brightness of the red glow depends on atmospheric conditions, such as dust and clouds. A partial lunar eclipse occurs when only part of the Moon enters the umbra, while a penumbral lunar eclipse is subtle and may go unnoticed. Lunar eclipses can happen up to three times a year and are safe to observe with the naked eye. As the Moon gradually moves away from the Earth, future total lunar eclipses may no longer be visible.

Keywords

💡Lunar Eclipse

A lunar eclipse is a celestial event where the Earth comes between the Sun and the Moon, casting a shadow on the Moon and temporarily darkening it. In the video, this phenomenon is the central theme, explaining how it occurs when the Sun, Earth, and Moon align, but not every month due to the tilted orbit of the Moon.

💡Full Moon

A full moon is when the Moon is fully illuminated as viewed from Earth, which happens approximately every 29.5 days. The video mentions that a lunar eclipse can only occur during a full moon, as this is when the Moon is in the correct position relative to the Earth and Sun for the Earth's shadow to fall on it.

💡Penumbra

The penumbra is the lighter, outer part of Earth's shadow. In the context of the video, it is described as the larger shadow cast on the Moon during an eclipse. A total lunar eclipse occurs when the Moon passes through the umbra, but a penumbral lunar eclipse happens when the Moon only passes through the penumbra, causing a subtle darkening.

💡Umbra

The umbra is the darker, inner part of Earth's shadow. The video explains that during a total lunar eclipse, the Moon passes through the umbra, resulting in a dramatic reddening of the Moon as the only light that reaches it is refracted red light from Earth's atmosphere.

💡Total Lunar Eclipse

A total lunar eclipse is when the Earth, Moon, and Sun are perfectly aligned, and the Moon is entirely within the Earth's umbral shadow. The video describes this as the most striking type of lunar eclipse, where the Moon takes on a sunset red color due to the scattering and refracting of light by Earth's atmosphere.

💡Partial Lunar Eclipse

A partial lunar eclipse occurs when the alignment of the Earth, Moon, and Sun is not perfect, and only a portion of the Moon passes through the umbra. The video mentions that during this type of eclipse, the Moon appears darker on the side facing Earth, as it is partially obscured by Earth's shadow.

💡Penumbral Lunar Eclipse

A penumbral lunar eclipse is the least noticeable type of lunar eclipse, where the Moon passes through the Earth's penumbral shadow. The video script indicates that this event is so subtle that it often goes unnoticed, as the Moon appears only slightly darker than usual.

💡Earth's Atmosphere

The Earth's atmosphere plays a crucial role in the coloration of the Moon during a total lunar eclipse. The video explains that shorter blue wavelengths of light are scattered, while longer red wavelengths are refracted towards the Moon, giving it a red hue. The clarity of the atmosphere, such as after volcanic activity, can affect the brightness of this red glow.

💡Refraction

Refraction is the bending of light as it passes through different media, such as from a vacuum into Earth's atmosphere. In the video, refraction is key to the red appearance of the Moon during a total lunar eclipse, as it describes how red light is bent towards the Moon while other colors are scattered away.

💡Volcanic Activity

Volcanic activity is mentioned in the video as an example of how it can affect the appearance of a lunar eclipse. Ash and dust in the atmosphere from volcanic eruptions can block or scatter light differently, causing the Moon to appear darker or even near black during an eclipse.

💡Distance

The distances between the Sun, Moon, and Earth are essential for the occurrence of a total lunar eclipse. The video script highlights that it is only because of these specific distances that we can witness the total lunar eclipse, as the Earth's shadow must be large enough to cover the Moon.

Highlights

A lunar eclipse occurs when the Earth blocks some or all of the sun's direct light from reaching the Moon.

Lunar eclipses only happen during a full moon, which occurs once every 29.5 days.

The Moon's orbit is tilted, preventing perfect alignment with the Earth and Sun every month.

During a lunar eclipse, the Earth casts two types of shadows on the Moon: the penumbra and the umbra.

Total lunar eclipses occur when the Moon falls within the Earth's umbral shadow.

Total lunar eclipses are dramatic, turning the Moon a sunset red due to the refraction of red light by the Earth's atmosphere.

The brightness of the Moon's red color during a total eclipse depends on the amount of dust and clouds in the Earth's atmosphere.

Volcanic activity can affect the darkness of the Moon's red color during an eclipse.

A partial lunar eclipse happens when only part of the Moon passes into the Earth's umbra.

A penumbral lunar eclipse is subtle, causing the Moon to appear slightly darker than normal.

Lunar eclipses can occur up to three times a year and are visible from the entire nighttime half of the Earth.

It is safe to view a lunar eclipse with the naked eye, unlike a solar eclipse.

The distances of the Sun and Moon from the Earth allow us to witness total lunar eclipses.

The Moon is gradually moving away from the Earth, which will eventually prevent total lunar eclipses in the distant future.

Lunar eclipses are a unique event where we can see our planet's shadow cast upon the largest object in the night sky.

Transcripts

(bright music)

- [Narrator] A lunar eclipse happens when the earth blocks

some or all of the sun's direct light

from reaching the moon.

This cosmic event only takes place during a full moon,

which happens once every 29 and a half days,

or the length of one full orbit

of the moon around the earth.

So why don't we have an eclipse every month?

The moon's orbit is tilted a few degrees

in relation to the earth,

so the earth, moon, and sun don't always align.

When the earth does eclipse the sun,

it casts two types of shadows on the moon,

a larger shadow, known as the penumbra,

and a smaller, darker shadow, known as the umbra.

There are three types of lunar eclipses.

The first is a total lunar eclipse,

when the sun, moon, and earth are in perfect alignment

and the moon falls within the earth's umbral shadow.

Total lunar eclipses are the most striking

of the three types because they turn the moon a sunset red.

While shorter, blue wavelengths of light

are scattered outward by the earth's atmosphere,

longer, red wavelengths are refracted, or bent,

inward toward the moon, making it appear red.

The brightness of the moon's red glow

depends upon how much dust and clouds

are in the earth's atmosphere.

Following volcanic activity,

ash can block out enough light

to render the moon a darker red, or even near black.

A partial lunar eclipse, the second type,

occurs when the earth, moon, and sun

don't perfectly align, so only part

of the moon passes into earth's umbra.

Earth's shadow appears very dark

on the side of the moon facing earth.

Last, a penumbral lunar eclipse,

occurs when the moon passes

through earth's penumbral shadow.

The event is so subtle that most people don't even notice.

The moon will appear just slightly darker than normal.

Lunar eclipses occur up to three times a year

and can be observed from the entire

nighttime half of the earth.

Unlike during a solar eclipse, it's safe to look at the moon

with the naked eye during a lunar eclipse.

It is only because of the distances of the sun and moon

from the earth that we are able to witness

total lunar eclipses.

As the moon inches away from the earth each year,

one day, billions of years from now,

the moon will be too far away to fall completely

within earth's umbral shadow.

Until then, we can occasionally enjoy seeing

our own planet's shadow cast upon

the largest object in the night sky.