Measure to the Moon 2020 – a reflection

Back in 2020 Mayes Creative ran a bit of a bonkers project where I asked you all to take photographs of Venus and the Moon wherever you were in the world. We had lots of people take part and loved how enthusiastic everyone was about joining in. One of these was the late eminent astronomer Jay Passachoff who had written about the method that could be used to measure the distance from Earth to the Moon.

I had been fortunate to meet Jay and hear all about his travels to see solar eclipses at a Society for the History of Astronomy Conference in 2018 and have been saddened to hear of his passing this week. He was always very encouraging of grassroots astronomy.

So I feel blessed to have had his support with this fun socially interactive project. Here is how what we did to measure the distance to the moon and the results we obtained.

The idea was to re-enact the historical ‘Transit of Venus’ which astronomers travelled around the world in order to measure the distance to the Sun using parallax. We attempted the same thing but with the Moon and Venus using social media with people sending their images back to us digitally. Once all the images of the Moon and Venus were received we worked out how to get a distance to the Moon using similar historical techniques. This was done by photographing the position of the crescent of the Moon in relation to Venus, as this would change depending on where you were positioned on the Earth. Over the past 3 months, we had great responses from around the world which enabled us to measure the Moon’s distance. 

We wanted to report back on how close a result we got from our ‘Measure to the Moon’ parallax project. 

February – the first event/ trial run.

A tall building in a city

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We had a good response but mainly from the UK, the furthest image we had to use as a baseline for the Parallax was from Portugal, we saw this as a trial run. The resulting distance we calculated was 271,734km and the Moon was 360,461km away from Earth, so we were a whopping 24.6% out.

March – the second event.

A lit up city at night

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We had many images for the March attempt, including some from the Abu Dhabi Observatory and also the Philippines which really helped us get a better idea of the parallax shift. This resulted in a calculated distance of 340,014km, the Moon at that time was 357,122km away so just a 5.03% difference, which we thought was pretty amazing. 

April – the third/last event.

A picture containing black, sitting, laptop, dark

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The final attempt in April was marred by clouds here in the UK, although there were clear skies in the South-West. We did have a number of US observers taking part including members of Flagstaff and Jay Pasachoff in New York – making the project international. We got a resulting distance of 315,736km, the Moon at this date was 356,906km away, so we had a difference of 11.5% – pretty respectable.

So overall the March attempt had the closest result due to the number of photos we received from all over the world. There were lots of lessons learnt along the way, but we were pretty pleased with the results. We really enjoyed this and may run something similar in the Autumn involving Mars. 

We followed Ernie Wright’s methodology to make the measurements: 

A Mayes Creative intern wrote a short computer program which scale-plated all the images and came up with averages. Then made all the calculations with guidance from astronomer Carolyn Kennett.  

If you have enjoyed this maybe you would like to check out the following which eminent astronomer Jay Pasachoff shared with Mayes Creative.

Pasachoff, Jay. M., Gährken Bernd., and Schneider, Glenn., (2017), “Using the 2016 transit of Mercury to find the distance to the Sun,” The Physics Teacher 55, 3 (March), 137-141: cover illustration plus article:

Alan Stern et al., New Horizons team, from beyond Pluto:

Udo Backhaus, Germany, from the 2019 transit of Mercury:

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