Interactive lab lets you close Philly streets and watch the graph Laplacian spectrum shift
prof_g · x · 2026-10-30
A neat interactive site called "Philly Under Construction" applies spectral graph theory to Philadelphia's real street network — 371 intersections and 591 roads.
You can put streets "under construction" (close Market, keep only Walnut open, cut all six river crossings) and watch how the graph Laplacian eigenvalues respond: algebraic connectivity λ₂ drops, and eigenvalues hit zero as the graph splits into disconnected components.
A spectral layout view repositions each intersection using eigenvectors φ₂ and φ₃ as coordinates, making it visually obvious which roads hold the city together. A genuinely intuitive demo of abstract linear algebra.
More from Fun
- Spies targeting Jensen, Sam, Dario and Elon would be 'weird' not to happen, says dev — rickasaurus · 2026-10-30
- Hugging Face employee's mom gets 🤗 emoji nails to support open source — pcuenq · 2026-10-30
- 'Girls only want one thing': an $496,639 8x NVIDIA B300 deep learning server — Kyrannio · 2026-10-30
- Aella clarifies: an Anthropic employee attended her events, sparking AI-circle drama — astralmatrix · 2026-10-30
- Starlink helps rescue Swedish sailor stranded off South Africa's coast — elonmusk · 2026-10-30
- Photographer Alex Hyner turns sky photos into stained-glass digital collages — mimi10v3 · 2026-10-30