Blood moon

First, let’s look at what an eclipse is. As everyone knows, you have the moon going around the earth once a month with the sun on the outside. Each month when the moon gets between earth and the sun it's called new moon and it is in the sky during the day, but when the moon gets on the dead opposite side of the earth to the sun two weeks later it is called full moon, the next which is on 8 October.

The full moon is always a night moon because that is the only time you would see it. New moon is a day moon. Most of the time the moon isn’t exactly in line with either the sun at new moon, or exactly opposite the earth in full moon. But when it is exactly in line, also called a node, one thing blocks out the other for a short while and we call it an eclipse. The origin of ‘eclipse’ is ‘leikw’ meaning  “to leave”, and is the same root as for ‘relinquish’.

The only reason we can ever see a full moon is because it has the sun's light shining past the earth onto it - the moon hasn't got a special lighting system of its own. That's like us standing beside the road and seeing what a car's headlights are shining on. But when the full moon is exactly in line with the earth and sun, like us standing in front of a headlight, the moon gets hidden by the earth and we call it ‘lunar’ eclipse, the next which is on 8 October.

The other situation is solar eclipse when a new moon blocks the sun during the day. So an eclipse will never occur on a quarter moon. We have thus far been describing total eclipses. There are also partial eclipses, which is when there's not a complete block-out and this depends on where you're viewing it from.

How often do eclipses occur?  Every year sees at least four eclipses (two solar and two lunar), somewhere on Earth, so lunar eclipses occur twice per year. At the rate of one every 173 days, there are two eclipse seasons per year. An eclipse season lasts for 37 days; and as the moon takes 29 days to complete an orbit, we're guaranteed one solar and one lunar eclipse every eclipse season. But lunar eclipses are not always total.

At the moment we have four total lunar eclipses in a row, each one six months apart. This phenomenon is called a ‘blood moon’. The last blood moon situation of four lunar eclipses in a row was 46 years ago in 1967-68, before that 1949, and before that in the 1400s.  For the current four full moon total eclipses in a row, the first was 14-15 April, then 8 October, the next is 4 April 2015, and then 28 September 2015. But then the next total lunar eclipse won't be until 31 January 2018.

The blood moon publicity is due largely to Christian pastor John Hagee who wrote a book in 2013 called Blood Moons. Most astronomers hadn't heard about them before. According to some it reflects on a biblical prophesy and links to the second coming of Christ. To an astronomer it's just four lunar total eclipses in a row without partial eclipses in between.

As for interpreting the bible, one does not wish to offend, but we might bear in mind that there are thousands of manuscripts of the bible in existence including 5,000 Greek versions, 8,000 Latin versions and a thousand manuscripts in other languages. Plus there were books left out and translations have changed over the years. It is said that the King James version, which is the most widely used nowadays, is the most slang version, so perhaps it is least close to the original.

The reason why the moon may be red is that we're viewing it low in the horizon so the light of it has to go through the thickness of earth's atmosphere. It's exactly the same reason a sunset is red. For the 8^th of October at the time of the eclipse the moon will be low, only halfway between horizon and zenith, and you will be able see it above the northeast in NZ.  That's because it rises at 7.15pm in the east and its highest point will be at 1am.

After a partial stage at around 10.15pm the total eclipse gets going around 11.30pm and the moon is closest to the centre of its shadow at midnight. Because the sky is typically clear on a full moon night, especially so around midnight, all should get a good view of the event  

There is also a link to the current cluster of earthquakes. We had a perigee on Monday when the moon came closest to the earth for the month, and earthquakes usually increase around perigees, which was the case for all the biggest Christchurch earthquakes in 2011. Earthquakes also increase in number and intensity around full moons, and quite often perigees and full moons are close to each other which again raises the chance of seismic activity.

For example for the 1931 Napier earthquake, full moon and perigee were on the same day, on 22 February 2011 both were within 3 days, on 20 March 2011 both were on the same day, and on 13 June 2011 perigee and full moon were within 3 days either side. If the full moon is in eclipse earthquakes again increase because the moon is at point blank range, not off a bit to the side, meaning more gravitational strain is put on earth’s electromagnetic field, inducing more stress inside the earth.

So as for the moon and blood, it is certainly a full moon, an eclipse and it may be red like a sunset. But the rest is imagination.