Category Archives: Curiosities of Nature

The zero meridian, or something like it

CIMG1443This weekend I took my parents to visit the Greenwich Meridian – or did I?

The marked meridian on the site of Greenwich Observatory, where tourists line up to pose for silly pictures with one foot in the East and one foot in the West, has claimed to be zero degrees longtidude since 1884, but if you check your smart phone GPS on that spot, you’re NOT at exactly 0.000 degrees.

According to GPS, the zero meridian appears to be in a park adjacent to the observatory, and not in the section behind the fence that charges admission so you can “visit the meridian”.

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What’s going on here?

Earlier this month, an article by Stephen Malys and others in the Journal of Geodesy revealed the reason behind the discrepancy. The technology used in the 19th century to determine the location of the zero meridian was subject to local distortions from the Earth’s gravity and shape of the local terrain. GPS technology uses measurements from satellites, which aren’t affected in the same way as technology located on Earth.

Screen Shot 2015-08-31 at 21.00.00

The dotted line is the much photographed meridian established in 1884. The solid line is where the GPS says it should be.

So the meridian really is in the wrong place. What does that mean for maps or for time? Well, the Ordnance Maps used in the UK were already using a slightly different zero meridian as reference point, because they were established before the 1884 meridian convention. And the effect of the new meridian location on Greenwich Mean Time, which determines Universal Time, is unnoticably small, so nothing much has changed.

Except, for a shorter line and a cheaper visit, you could technically skip the museum and the crowd of tourists and find the true GPS meridian about a hundred meters to the East of the Observatory in Greenwich Park. It’s probably not as fun a place for a family visit, though.

Aerial photo is Figure 1 from the article by Malys et al. (CC-BY). Photos taken from the ground are by me and by the man who was behind us in line at the almost-but-not-quite meridian line. I previously wrote about the history of the Greenwich Observatory on this site.

Science for the People: Coffee Table Science

sftpThis week, Science for the People meets the authors of three big books that use stunning images to tell intriguing stories about the history of science. We’ll discuss evolution and the building of the fossil record with invertebrate palaeontologist Paul Taylor, author of A History of Life in 100 Fossils. Archivist Julie Halls shares stories of unheralded ingenuity from her book Inventions that Didn’t Change the World. We will also learn about attempts to map the world in three dimensions from independent conservator Sylvia Sumira, author of Globes: 400 Years of Exploration, Navigation, and Power.

*Josh provides research help to Science for the People and is, therefore, completely biased.

Science for the People: Animal Weapons

sftpThis week, Science for the People is talking about weapons: both the ones that evolve in nature, and those created by humanity. We’ll talk about the arms races that spur the development of horns and claws, warships and nuclear weapons, with Doug Emlen, Professor in the Division of Biological Sciences at the University of Montana, and author of Animal Weapons: The Evolution of Battle.

*Josh provides research help to Science for the People and is, therefore, completely biased.

There is No Dark Side

dscovrepicmoontransitfullAccording to NASA, this shot of the far side of the Moon was captured by the Deep Space Climate Observer Satellite as it orbited a million miles above Earth. The “dark side” of the Moon is only figuratively “dark”.

I also feel like the realization that the “dark side” of the Moon has become progressively less mysterious since humanity’s first imaging of it in 1959 kind of ruins the conceit of isolation in Moon for me.

HT: David Grinspoon

And on your right is the planet Pluto…

According to NASA, the New Horizons spacecraft made its closest approach (about 7800 miles) to Pluto right now (7:49AM ET, 14 July 2015) after traveling three billion miles. If you want a travel post, that certainly fits the bill.