What is a lunar eclipse? The next in 2021 will be the longest partial eclipse of the century

A partial lunar eclipse is expected to take place next week between November 18 and November 19, resulting in a visual experience for millions of people around the world with clear skies at night.

Lunar eclipses themselves are not very rare – they occur at least twice a year – but the next one is to be the longest partial lunar eclipse of the century, lasting almost 3.5 hours from start to finish, according to NASA’s eclipse website.

What is a lunar eclipse?

All planets and moons in the solar system are constantly moving around in certain orbits.

A lunar eclipse occurs when the Earth gets in the way of the sun’s light and prevents it from reaching the moon. This can happen completely when the moon comes completely into the Earth’s shadow, or partially.

For observers, this causes the moon’s light to fade during the night as it slides into the darkness that the Earth casts.

Lunar eclipses can also make the moon look red or orange.

This is because even though the Earth blocks the light of the sun, some of this light still reaches the moon after passing around the edge of the Earth and through our atmosphere.

When sunlight passes through our atmosphere at a certain angle, it tends to look red. This is why sunrises and sunsets also look orange.

Lunar eclipses last a maximum of a few hours. They can be seen by all who live on the nocturnal half of the Earth and who have a clear sky.

When is the next one?

The next lunar eclipse will be a partial one, and it will take place overnight between November 18 and November 19.

The time at which this happens will be different depending on where humans are on the planet.

For people living on the U.S. East Coast, for example, the eclipse will begin just after noon. 2 local time on November 19 and reach its maximum around noon. 4, informs NASA.

In the UK, it starts just after noon. 7 local time on November 19 according to TimeAndDate and reaches its maximum just after noon. 9 – which will not be visible.

People living elsewhere should check their local time zones.

People in some other places may find that unfortunately the moon will not be visible at the time of the eclipse due to clouds, or simply because it is daytime.

For people who miss it, there will be a full lunar eclipse between May 15 and 16, 2022, and another between November 7 and 18 that year, according to TimeAndDate.

Partial lunar eclipse
A partial lunar eclipse seen from Israel in August 2017. There are usually a few lunar eclipses each year.
Jack Guez / AFP / Getty

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