August's two supermoons: What are they and how can they affect your sleep and mood?

One is what's known as a blue moon - and where the famous saying comes from.

A supermoon rises above Liverpool. (Getty Images)
A supermoon rises above Liverpool. (Getty Images)

You may notice the full moon appears larger and brighter on two evenings this August - that's because what's known as a supermoon is due twice this month.

The natural phenomenon - which can make the moon appear 14% bigger and 30% brighter - usually only happens a few times a year, however there will be four supermoons happening a year between 2020 and 2025, according to the Natural History Museum.

While the UK already had its first supermoon of the year in July, August brings with it a further two - culminating with a rare blue moon.

The first will take place on Tuesday 1 August, with the second blue moon happening at the end of the month, on Thursday 31 August. The latter is known as a blue moon because it's the second supermoon in the same calendar month.

According to NASA, a blue moon only occurs once every two to three years, hence the saying "once in a blue moon".

While you can expect these supermoons to be full and bright, the most spectacular full moons only occur a few times a century - and you've got another decade to wait for the next.

The last time this happened was in November 2016, when the moon was the closest it had been to earth since January 1948. The next time it will be that close will be 25 November, 2034, but the closest full moon this century will occur on 6 December, 1952.

Read more on this month's supermoons

The Full Buck supermoon rises over St Mary's Lighthouse in Whitley Bay, on the North East coast of England. The July supermoon is arriving to its closest point to Earth at 224,895 miles (361,934km) - around 13,959 miles (22,466km) closer than usual. It appears 5.8 per cent bigger and 12.8 per cent brighter than an ordinary full moon. Picture date: Sunday July 2, 2023. (Photo by Owen Humphreys/PA Images via Getty Images)
The supermoon rises over St Mary's Lighthouse in Whitley Bay, on the North East coast of England on 2 July. (Getty Images) (Owen Humphreys - PA Images via Getty Images)

What is a supermoon?

A supermoon occurs when that month’s full moon is closer to the Earth than usual, and therefore appears to be a bigger and brighter full moon.

During the moon’s orbit of Earth, it can be anywhere between 360,000 to 400,000 kilometres away. When it’s at its furthest point away from Earth, it can be called a ‘micro moon’.

A supermoon, which only occurs a few times each year, casts around 30% more light than a regular full moon due to more of the sun’s rays reflecting off its surface. A supermoon can also appear larger when rising or setting on the horizon because we have objects like trees and mountains to compare it to.

2023 supermoon dates

There will be four supermoons in 2023. These fall on:

  • 3 July

  • 1 August

  • 31 August

  • 29 September

How to see a supermoon

The supermoon on 1 August will reach its peak at 7.31pm and the full moon on 31 August will reach its peak at 2.35am. The only way you will see it is if there are clear skies. It should be easy to see by looking up at the sky, but you can make your way to a higher vantage point with less light pollution if you want a clearer view.

How a supermoon affects health

While the moon affects the Earth’s tides, it’s also been said to have an effect on our moon and sleeping patterns - but how much truth is there to these claims?

A small-scale study from 2013 looked at the impact of a full moon on human sleep cycles and it found that, during the time of a full moon, deep sleep decreased by 30%, it took participants five minutes longer to fall asleep and total sleep duration decreased by 20 minutes.

A separate study from the US Department of Justice that was published in 1978 found that the moon’s "gravitational influence brings about social tension, disharmony and bizarre results".

NEW YORK, UNITED STATES - JULY 3: Supermoon also known as 'Buck Moon' sets over the Statue of Liberty in New York City, United States on July 3, 2023. (Photo by Lokman Vural Elibol/Anadolu Agency via Getty Images)
The Buck supermoon in New York City on 3 July. (Getty Images) (Anadolu Agency via Getty Images)

A third study from 2011, published in the World Journal of Surgery, found that 40% of medical staff believe that lunar phases can affect human behaviour.

"The concept of a supermoon affecting one's mood or behaviour is largely based on anecdotal evidence, popular beliefs, old wives tales rather than scientific research," Liberty Mills, an Integrative Health and Nutrition Professional, says.

"While some people claim to experience heightened emotions or changes in mood during a supermoon, there is no actual scientific consensus or solid peer reviewed research or published papers supporting these claims."

Mills adds that there is limited scientific research examining the impact of a supermoon on sleep patterns.

"Sleep disturbances can be influenced by various factors such as stress, environmental conditions, and personal health," she continues. "While some individuals may report difficulty sleeping during a supermoon, it is likely attributed to other factors rather than the celestial event itself.

"In terms of health effects, there is currently no scientific backing for any direct impact of supermoons on human health. The gravitational pull of the moon does have an effect on Earth's tides, but its influence on human physiology is negligible. It is worth mentioning that some studies have explored potential links between lunar cycles and certain medical conditions such as epilepsy or psychiatric disorders, but the results have been inconclusive and require further investigation."

Watch: First supermoon of the year shines over London