Moon phases on other side of Earth

02 April, 2009

Photograph of Moon at Full phase
Source: Museum Victoria

Question: If it is a full moon in Australia, is it also a full moon on the other side of the world?

Answer: The phases of the Moon are the same all around the world. Any two places that can see the Moon at the same time will see the same phase.

Each Moon phase happens at a precise point in the Moon's orbit around the Earth, and hence at a precise moment in time. This is the same moment all over the world, but will be a different local time for every time zone in the world.

For example, the first full moon of the 21st century occurred at 8:24pm on 9 January 2001, Universal Time. In Melbourne this moment was 7:24am on 10 January 2001, Australian Eastern Summer Time.

Of course opposite sides of the world will not be able to see the Moon at the same time. Only one half of the world will be able to see the moon when it is precisely at one of the phases. For the example I gave above, that Full Moon was visible from the United Kingdom, but not from Australia. The Moon had set in the west around two hours before it became full. However since the appearance of the Moon’s phase does not change very quickly, the Moon would have looked very full when it set.

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Comments (12) popular | oldest | newest

We are studying Space in our classroom this term. After reading this article, here are some questions from our class. What Colour is the moon? Josh, Grade 2 How many different phases of the moon are there? Imogen, Grade 2 When you have a crescent moon, why can't you see the whole moon? Leila, Grade 1 How wide is the moon? Sam, Grade 2 How high up is the moon? Alycia, Grade 3 Does the moon have a moon of its own? Obi, Grade 3 Thanks, 1/2/3 Brunswick East Primary School

reply (2)

Hi Josh, Imogen, Leila, Sam, Alycia and Obi,

The colour of the Moon is very subtle: it has soft shades of grey, black and white, and regions of browns, blues and yellows. We generally say there are four phases of the Moon. New, First Quarter, Full, and Last Quarter. See the Moon Phases page of our website.

It is actually possible to see the whole Moon during the crescent moon phase. Sometimes there is so much light reflected from the Earth (Earthshine), that it lights up the part of the Moon that is not lit up by the Sun: we see the bright crescent Moon as well as the pale remainder of the Moon. As the Moon phase moves towards the Full moon, the Moon is so bright you can no longer see the arthshine on the Moon. The Moon has to be in the right position for the Earth to reflect the Sun's light onto the Moon's night side; this only happens just after the New Moon. This is called the Da Vinci Glow. You can find out more about it on the NASA website.

The diameter (width) of the moon is 3475.6 km (0.272 x that of Earth). The moon is (on average) 384 400 km from the Earth. The Moon does not have a moon of its own. You can learn more about The Moon on our website.

On behalf of my daughter: TV News stated that there was a "blue moon" in December.My calendar says that full moon actually occurred on the 1st January, 2010, not 31st December 2009, and the next full moon is to occur at the end of January, making it a "blue moon" in January. Which is correct?

Hi Melbourne Planetarium, Could you please confirm something for me? When I visted Australia a couple years ago, I really hoped to see a full moon and see that it was inverted from what I normally see in the United States. For example, on your website you have a beautiful full moon picture showing the "Sea of Crisis" in the 8 o'clock position where normally I see it in the 2 o'clock position. Unfortunately, conditions were such that I never got to see that. Is it correct that this the way the moon looks to you deep in the southern hemisphere where looks the opposite to me deep in the northern? Thanks very much.

Hi Wayne, yes, views of the Moon seen from one hemisphere compared to the other hemisphere are inverted. It’s due to the changed angle looking out from the spherical surface of the Earth. The same “upside down” effect is noticeable for constellations in the night sky too provided you are far enough north or south of the equator. Mid to high latitudes show this quite clearly.

Looking at the moon tonight we noticed a large star or bright plannet above it to the right. Can you please tell me what it is? This was at about 8.15 - 8.30 pm on Saturday 11th September 2010. We haven't noticed this before. Thank you for your help.

Hi Lynne the bright object next to the Moon last Saturday was Venus. Just below it was the planet Mars, which is slightly orange/red in colour and not very bright. There is also a bright star called Spica very near as well, but this is nowhere near as bright as Venus. You can find more info at Museum skynotes: http://museumvictoria.com.au/planetarium/discoverycentre/skynotes/

although we see full moon at same time worldwide - does the waxing and waning happen oppositely. In northern hemisphere after a full moon visible part becomes a c whereas in southern hemisphere visible part becomes a d?

Hello Lawrence - the waxing and waning does appear to happen in an opposite seqence here from the Sothern Hemisphere, but this is because the moon appears 'upside down' compared to what is seen in the Northern Hemisphere - I hope that answers your question!

While on a motorcycle tour through Lao, my friend and I stoped for the night at a town in the mountains called Phu Khon, this town is on the 19.5 paralell.We noticed the moon was in the first or last quater but the crescent was parallel to the horison like a smile, and orange in colour. We have not seen the moon in this position before, what were we seeing? Was this view because of our altitude, or could it be light reflection from Earth? This was on the 29th December 2011 at about 9:00pm. Can you shed some light for us? Cheers.

Hi Andrew, the direction the crescent shape of the Moon faces depends on a number of factors. Principally it depends on where on the Earth you are viewing the Moon. The view in the northern hemisphere is the opposite to that in the southern hemisphere, and on the equator it is halfway in between. The next important factor is whether it is a waxing or a waning moon, i.e. is it just after a new moon or just before a new moon. And lastly the time of the day or night you are looking at the moon.

So when you were near the equator on the 29^th December the crescent moon in the early evening would be waxing (just after a new moon) and would be halfway between facing left and right, just like a boat.The red/orange colour is due to atmospheric pollution, most likely due to volcanic ash or bush fire smoke.

We have just returned to the UK from a month in Australia and during the last few days in Brisbane we saw some very clear nights to look at the stars. It was only then that amongst the family we realised we had not seen the moon or any of its phases during the last couple of nights.Was this just bad looking or a specific reason?

Hello Terry,

There was a New Moon on Monday 23^rd so no Moon could be seen for a couple of days either side of that. Check out Skynotes for this information. http://museumvictoria.com.au/planetarium/discoverycentre/skynotes/

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