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hepsilon-delta

@hepsilon-delta.bsky.social

201 followers 175 following 16 posts

Mathematician at University of Aberdeen. Collector of houseplants, yo-yos, hobbies. Recently taking photos.

Posts Replies Media

hepsilon-delta @hepsilon-delta.bsky.social · 8h

📷 Pentax 17 🎞️ HP5+ 🧪 Gulabi #filmphotography

Black and white photograph of a bedside table between two beds. On the bedside table you can see a lamp, a cuddly cat toy (the Sprigatito in fact) and some smaller items.

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hepsilon-delta @hepsilon-delta.bsky.social · 05/10/2026

📷 Pentax 17 🎞️ FP4+ 🧪 Gulabi 📍 Duinrell #filmphotography

Black and white photograph of a theme park aeroplane ride. You can see the long boom that the planes are attached to, and several of the planes in the foreground.

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hepsilon-delta @hepsilon-delta.bsky.social · 04/10/2026

📷 Pentax 17 🎞️ FP4+ 🧪 Gulabi 📍 Duinrell #filmphotography

Black and white photo of a log flume, with a huge splash at the point where the cart has just met the water.

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hepsilon-delta @hepsilon-delta.bsky.social · 02/10/2026

📷 Pentax 17 🎞️ FP4+ 🧪 Gulabi 📍 Duinrell #filmphotography

Black and white photo of a theme park ride. The ride swings two rows of riders up and down while also turning them upside down. The photo is taken at a point when the riders are up high and facing down. There are people in the foreground, some watching or photographing the riders.

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hepsilon-delta @hepsilon-delta.bsky.social · 02/10/2026

📷 Pentax 17 🎞️ FP4+ 🧪 Gulabi 📍 Duinrell #filmphotography

Black and white photo of woodland and then suburbia stretching to the horizon. We are looking down at a mobile phone mast and a pair of curving bobsled tracks.

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hepsilon-delta @hepsilon-delta.bsky.social · 01/10/2026

📷 Pentax 17 🎞️ FP4+ 🧪 Gulabi 📍 Duinrell #filmphotography

Black and white photograph of a theme park aeroplane ride. In the foreground is a railing and part of a building, and further back you can see part of the ride itself.

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hepsilon-delta @hepsilon-delta.bsky.social · 01/10/2026

📷 Pentax 17 🎞️ FP4+ 🧪 Gulabi 📍 Duinrell #filmphotography

A black and white photograph of two diagonal ramps, one behind the other.

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hepsilon-delta @hepsilon-delta.bsky.social · 30/09/2026

📷 Pentax 17 🎞️ Portra 160 🧪 Gulabi 📍 Duinrell #filmphotography

Photograph of a rollercoaster track surrounded by trees. A cart full of riders is ascending a vertical section of the track.

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hepsilon-delta @hepsilon-delta.bsky.social · 02/09/2026

📷 Pentax 17 🎞️ HP5+ 🧪 Gulabi 📍 Duinrell #filmphotography

A theme park. You can see an aeroplane ride swing through the air, and a water slide snaking in from the left. Some people are sitting on rocks closer to the viewer.

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hepsilon-delta @hepsilon-delta.bsky.social · 01/09/2026

📷 Pentax 17 🎞️ HP5+ 🧪 Gulabi 📍 Duinrell #filmphotography

Three ducks on a path with a hedge and cabin in the background. One of them looks like it’s addressing someone or something out of shot to the right.

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hepsilon-delta @hepsilon-delta.bsky.social · 31/08/2026

📷 Pentax 17 🎞️ Portra 400 🧪 Gulabi 📍 Duinrell #filmphotography

A swimming pool complex. It has a tower with water slides descending from it, and a flag flying from the top of the tower. There are bushes and a tree in the foreground. You can see the shadow of someone going down one of the slides.

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hepsilon-delta @hepsilon-delta.bsky.social · 29/08/2026

📷 Pentax 17 🎞️ Portra 400 🧪 Gulabi 📍 Duinrell #filmphotography

A theme park ride that spins and swings at the same time, and which is styled as if it’s old-timey and wooden. This image shows the base of the “barrel” that the riders sit in when the whole thing’s swinging far to the left.

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hepsilon-delta @hepsilon-delta.bsky.social · 10/12/2024

Getting mathematical: there are examples matching tetrahedron, cube, octahedron and dodecahedron, but not the icosahedron. But the first ball here shows that the makers are close to being able to “dualise”, so it’s plausible to me that they may have known the icosahedron-type arrangement.

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hepsilon-delta @hepsilon-delta.bsky.social · 10/12/2024

The large discs on the ball in the first image match the faces of a cube; the knobs on the ball in the second image might match those of a dodecahedron.

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hepsilon-delta @hepsilon-delta.bsky.social · 10/12/2024

Carved stone balls are uniquely Scottish artefacts from the late Neolithic (3000-2500 BCE). The decorations, often raised or inscribed knobs or discs, are in some cases configured in the same way as faces or vertices of polyhedra.

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hepsilon-delta @hepsilon-delta.bsky.social · 10/12/2024

Visiting Oxford for a viva, and there’s time to look at some carved stone balls in the Ashmolean museum.

Scottish Neolithic carved stone ball. (Ashmolean museum AN1927.2727 or AN1927.2730) Carved from red stone, about the size of a tennis ball, and decorated with 6 large raised discs (arranged like the faces of a cube) and 8 raised triangles (arranged like the vertices of the cube).

Scottish Neolithic carved stone ball. (Ashmolean museum AN1927.2727 or AN1927.2730) Carved from pale stone, a bit smaller than a tennis ball, and decorated with raised knobs (possibly 12 of them arranged like the faces of a dodecahedron).

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