This blog post is a collaborative effort between journalist and author Jimmy Thomson and myself. It concerns the phenomenon that I have taken to calling USAs (Urban Solstice Alignments). Jimmy is the Sydney-based polymath who first brought this concept to my attention, leading to an earlier blog post I wrote on the topic, What would we do if the sun died?, which focused on the most famous USA in the USA (and indeed the world), Manhattanhenge. In this new post, we’ll focus on the logistics of finding and making sense of urban solstice alignments through both analogue and digital means. By searching for the phenomenon, will we destroy its magic?

How to find your own Manhattanhenge by Jimmy Thomson

I have been promising the Urban Prehistorian for more than a year to write something about how to discover your own Manhattanhenge in a town or city near you. Now, I should make it clear that I am neither a geographer, cartographer, astronomer nor a mathematician.  I’m a journalist, author and travel writer with all the lack of useful skills that implies.

Manhattanhenge is a phenomenon that occurs when the rising or setting sun appears between the high-rises of New York and shines directly down its East-West aligned streets. People travel to New York to see it, and it occurs on two days in both May and December, so it’s a big deal (to some).

But given that it’s just the rising sun appearing or the setting sun disappearing between buildings or even the sides of a steep valley, surely this must occur elsewhere. And it does, although possibly not as spectacularly as in New York or, indeed, Stonehenge. In fact, you may be able to find one near you and this is how to do it.

Firstly you will need to identify a long straight road that drops towards the horizon and has no obstructions (like buildings) at its farthest end.  To get the full effect, you the sun to appear on the horizon where the diffraction of light through the thick layers of the atmosphere has greatest effect.  Basically, we’re probably talking about somewhere over water or flat land.

You don’t want the street to be perfectly aligned East-to-West as that would only work close to the equator.  The best streets in NYC for viewing Manhattanhenge are on 118 degrees, which is  full 28 degrees south of East.

Then you will need Google Maps and two free online apps called SunEarthTools and another named Mapping and Distance Tools.  There are other online apps that will do what we want here and if you can find them and get them to work, go for it. Basically you want one app that will establish the compass direction of the road line, and another that will tell you exactly when the sun will rise at that point on the horizon.

So first we identify a likely location – a long straight road, dropping to the horizon, with high sides and no obstructions.  This is where Google Maps comes in handy as you can use the 3D satellite view to check for obstructions and the height of the buildings along the sides.

For the purposes of this exercise, I have chosen Hooker Boulevard running down to Mermaid Beach (the thin while line in the centre of this image above, from Google Maps), in Broadbeach in the Gold Coast area of Queensland, Australia.

Why there?  Because I know that whole area has a lot of high rises that go all the way down to the beach.  It ain’t Manhattan but a quick scan of Google maps confirms that the road is straight and runs roughly East.

The next thing is to use Mapping and Distance Tools to draw a line from where you might view the phenomenon to where the road runs out.

The display in the top left corner will give you the azimuth or compass direction that this line follows.

In this case the road runs straight down a line heading 79 degrees from North.

Then we move on to the SunEarth app where we can fiddle with the times and dates to find out exactly when the sun will rise on or near that point on the horizon.

This tells us that the sun will rise there at a few seconds before 6.04 am on April 16, this year.

Now, the sun doesn’t go straight up, it also travels north or south as it rises, so you might want to adjust by a day or so to get the best effect when the sun has fully risen. SunEarth will show the variations hour by hour. So there you go. 

Find some canyon, concrete or otherwise, pointing roughly East-South-East in the Northern hemisphere, or ENE south of the equator, and start working the map apps to find the optimum date, and you have your own Manhattanhenge.

This can work just as well for sunsets although obviously you change the principal direction from East to West.

This may now be factored into holiday planning as well as potential romantic first dates for geeks, especially if you go for sunsets.

Most importantly, you may also have acquired a new appreciation of how clever the Mayans, Egyptians, Druids (if indeed it was them) and all the ancient standing stone cultures were.

The ubiquity of USAs suggests this is all a big coincidence but that doesn’t invalidate the experience that some people have of this phenomenon by Kenny Brophy

In a recent study of the levels of entropy of urban networks, Geoff Boeing suggested that ‘networks such as streets, paths, and transit lines organize the human dynamics of complex urban systems. They shape travel behavior (sic), location decisions, and the texture of the urban fabric’ (2019, 1). However, what if another organisational factor was at play here – the sun?

The alignment of straight urban streets towards solstice sunrises and sunsets as discussed by Jimmy is a recognised international phenomenon. There are actually quite a few of these, almost all with the suffix -henge, making of course a conceptual connection with Stonehenge, a prehistoric monument in England that is commonly thought to have solar elements built into its architectural organisation. (Perhaps we should call this particular effect Stonehengehenge.) These events generally happen on a day or two each year, and sometimes draw crowds of early risers wearing sunglasses.

And so in North America, we have Manhattanhenge, in New York, but there is also Chicagohenge, Montrealhenge, Torontohenge, and Phillyhenge (Philadelphia). It is perhaps not surprising that the best-known examples of this phenomenon are in North America. Boeing’s study concludes that, ‘on average, US/Canadian study sites are far more grid-like than those elsewhere, exhibiting less entropy and circuity’. This is certainly the case for Manhattan, Philadelphia and Chicago. Boeing’s data shows why there is a Manhattenhenge but not a Bostonhenge.

Boeing 2019 Figure 3
Cities that have USAs are more likely to be organised high-entropy cites (bottom left) (Boeing 2019, Fig 7)

Furthermore, opportunities to witness such events seem to be increasing: the equivalent in Washington DC is called ‘DC Henge week‘ reflecting the inherently non-precise nature of aligning the sun and skyscrapers, and this can all work for sunsets as well as sunrises, doubling the equinox fun. These events are perfect for instagramers and tweeters, wonderfully hashtaggable.

Chicagohenge, seen from West Adams Street on March 12 2020 (photo: Tim Hara from Adler Planetarium webite)
Phillyhenge September 5th 2012 (from Hidden City wesbite)
Torontohenge (@serenevistas)

Further afield, there are USAs in Australia (Melbhenge) and has been made clear above, Jimmy has found one on the Gold Coast. There would seem potential for a Sydneyhenge but this one does not seem to have got much traction online. This might be a chance for Jimmy to get something started in that city, and often a -henge event can take on a momentum of its own once someone points it out and gives it a hashtag.

Melbhenge from twitter user @_jlrreyes (on Secret Melbourne website)

What is the value in the identification of such solar alignments? The phenomenon is often flagged up by city planetariums (planetaria?) as a tool to raise awareness of an interest in the skies in general, as is the case for New York and Chicago. Dr Rebecca Allen of the Centre for Astrophysics and Supercomputing in Melbourne has argued that, ‘Melbhenge is a great time to explore how our modern landscape reflects the efforts our ancestors made to track the motions of the heavens’ suggesting a deeper educational value akin to the aspirations behind the construction of the Sighthill stone circles in Glasgow by Duncan Lunan. There is a sense that these experiences are not so much educational as primal. Jackie Faherty, an American Museum of Natural History astronomer, has suggested that, ‘Daily life in the 2000s does not have the same connection to the solar system that daily life hundreds of years ago did. Moments where we get to see an interplay with the sun or the planets with our everyday experiences such as a city grid are a reflection of how the human experience is complemented with a connection to the bigger picture of the cosmos’ (USA Today). Maybe it just makes us feel small and insignificant, an effect cities already have on some people.

One of the most pressing questions I suppose that some of those who witness a -henge USA are surely, ‘are these deliberately built into the city design’? Or ‘is this just all a big coincidence’? One way to look at this could be around the statistical probability that in a large urban network there would not be at least one street that aligned towards a solar solstice event.

This is explored albeit perhaps not from the point of view of the latter sentence in a website called On solstices and city planning designed by Demeter Sztanko. Here is presented street plans of hundreds of cities and big urban areas across the world showing where solstice alignments occur. This data comes from some kind of algorithm that has been focused on Open Streetmap: Sztanko describes his work as ‘pure math’ (The Guardian). I suppose this shows that by looking hard enough and by asking the right questions, -henge events are commonplace and everywhere. One does not need to focus on one street in one city as Jimmy suggests when one could algorithm an entire country. I do not mean to downplay the complexity of this piece of work as it presumably needs to take into account the location of the city in relation to the equator as well as the street plan, but it does show how USAs happen accidentally, an unexpected (and more often than not un-noticed) outcome of building a city. This website also fails to demonstrate causality: just because a pattern is evident does not mean that it is significant or deliberate, something Sztanko acknowledges. ‘Unfortunately I don’t know whether these alignments are intentional or just happen to be such on statistical basis’.

I suppose the sheer quantity and banality of the data ultimately points towards this being a unexpected byproduct of urbanisation. To illustrate this, I used this website to explore a city close to where I live – Glasgow. There is indeed a Glasgowhenge. In fact, there are potentially many of them in the area, due to the northwest-southeast trend of many streets. Most of these are short stretches of road and one would have to carry out some fieldwork to establish if they have the correct criteria for working as a -henge event as set out by Jimmy earlier on. Some are interesting from a coincidence point of view, such as Kenmuirhill, Mount Vernon, which runs close to the location of a Bronze Age cemetery that was excavated in the 1920s by Ludovic Mann. A short stretch of Cochno Road, near the Cochno Stone, also fits the bill.

Screen grab from Solstices & City Planning website: Glasgow. Red lines = solstice aligned street sections

But there are essentially no possible solstice alignments in the city centre, the grid layout of much of the city north of the Clyde running in the wrong direction. Furthermore, in Boeing’s data, Glasgow is no Chicago when it comes to grids and entropy.

From Boeing 2019

Having said that, there is more than one type of Glaswegian prehistoric urban alignment if Harry Bell is to be believed, his network of aligned sites somewhat more free-form and not dependent on either street layout or the movement of the sun.

The map from Harry Bell’s Glasgow’s Secret Geometry: the City’s Oldest Mystery.

A combination of the high-level data at mapping level, followed by fieldwork at the right time of the year, would no doubt illuminate some fun experiences to be had some mornings or evenings in some cities around the world. This is probably enough to be getting on with.

USAs are derived from two different overlapping human urges – pareidolia (seeing patterns in things) and an obsession with the sun. In USAs this becomes entangled with our concepts of time and the calendar, and desire for urbanisation. In that sense if it is fascinating contemporary human phenomenon. What is remarkable about the song and dance, the branding, the crowds, the sunglasses, and the search for meaning is that in almost all cases this is meaningless in the sense that whatever we think we are experiencing was never intended to happen. This does not invalidate the experience of a USA but it does suggest that we are making this stuff up as we go along and reading our own meaning into the experience. As Boeing notes, cities can be ‘planned or unplanned, ordered and disordered’, and the same could be said about stone circles and henges.

There is nothing wrong with any of this, and searching for a -henge in the streets of you city, or on the screen of your laptop, is not in itself futil. Reading too much into whatever you find might well be, but then that is what makes us human, and connects us to the original henge builders from millennium ago.

Sources and acknowledgements: I must thank Jimmy Thomson for writing part of this blog post and encouraging me to think about USAs again. This blog post also makes reference to this academic paper:

Boeing, G 2019 Urban spatial order: street network orientation, configuration, and entropy. Applied Network Science 4: 67.

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