What is a blood moon? Here’s why the moon turns red during a lunar eclipse

The UK is set to experience a “blood moon” next month as our lunar neighbour turns a deep coppery shade of red.

It’s a fairly common phenomenon that happens roughly twice a year – but has always had mysterious connotations.

Plenty of conspiracy theorists have seized on blood moons as evidence of the coming apocalypse.

The hypothesis was originally made famous by Christian ministers John Hagee and Mark Biltz who said an ongoing “tetrad” – four consecutive blood moons which began in April 2014 with six full moons in between – was the indicator of the end of earth as described in the Acts 2:20 and Revelations 6:12.

Suffice to say, we’re all still here.

In fact, there’s a very scientific reason for why the moon turns red during a lunar eclipse.

What is a blood moon?


A lunar eclipse occurs when the moon passes in the shadow of Earth. This is an area known as the umbra, where light from the Sun is blocked by our planet.

When the light refracts differently in the atmosphere and hits the moon, it makes it appear red. During a total eclipse, the entire moon is in shadow and it appears ‘blood red’.

But when it skirts the shadow, known as a partial or penumbral eclipse, the effect is less dramatic.

What do the scientists say?

“The moon’s orbit around our planet is tilted so it usually falls above or below the shadow of the Earth,” explains NASA.

“About twice each year, a full moon lines up perfectly with the Earth and sun such that Earth’s shadow totally blocks the sun’s light, which would normally reflect off the moon.”

“The moon will lose its brightness and take on an eerie, fainter-than-normal glow from the scant sunlight that makes its way through Earth’s atmosphere,” the space agency said.

“Often cast in a reddish hue because of the way the atmosphere bends the light, totally eclipsed Moons are sometimes called ‘blood moons.’”

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Blood moon

How long do blood moons last for?


The length of a lunar eclipse relies on a number of factors – but they usually do not last for more than a couple of hours.

For example, the lunar eclipse taking place on July 27, 2018, is predicted to be one of the longest ones this century at roughly one hour and 43 minutes.

There are a couple of reasons for this. Firstly, it’s happening at the same time as the moon’s apogee – when it’s at its furthest point away from Earth.

Secondly, it will be passing directly into the darkest region of the Earth’s shadow.

The average lunar eclipse lasts for just about an hour. And we’re talking about the part of the eclipse called “totality”, where the entire face of the moon is in shadow.

There are also pre-eclipse and post-eclipse phases (just like with a solar eclipse) that can often bring the total time of a blood moon up to around five hours.

When is the next blood moon?

Now that’s what we call a blood moon! Thanks to Emily Perkins for this

The next blood moon lunar eclipse visible in the UK will take place on the night of July 27 and the early hours of July 28 to get the best view. It shouldn’t matter where you are in the UK – if you can get to an open space with a clear view of the sky, you should be able to see it.

As always, make sure you’re as far away from light pollution as possible.

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