Into the Impossible With Brian Keating The Dark Energy Mystery: What We Learned at the Royal Observatory Edinburgh
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Apr 3, 2026 Marcos Pellejero, a cosmologist working on large-scale structure, simulations, and DESI analyses. He tours the Royal Observatory, explains baryon acoustic oscillations as a cosmic ruler, dives into N-body simulations and machine-learning emulators, and discusses whether DESI hints that dark energy may not be constant.
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Cathedral For Starlight And Human Computers
- The Royal Observatory was designed as a cathedral for starlight with human 'computers' measuring photographic plates by hand.
- Marcos Pellejero describes people (often women) who combed plates and how the building's pier isolates the telescope for vibration-free observations.
Dome Engineering And The Royal Astronomer's Lift
- The old dome is more ornamental than functional and includes a separated pier sunk into the hill to avoid building vibration.
- Marcos shows how the dome rotates with wheels and even an electric lift was built so the Royal Astronomer wouldn't climb ladders.
BAO As A 150 Megaparsec Cosmic Ruler
- Baryon acoustic oscillations (BAO) are a faint preferred scale in galaxy clustering left from early-universe sound waves, acting as a cosmic ruler.
- Brian Keating and Marcos explain BAO appear as a ~150 megaparsec preference in galaxy separations used to measure expansion history.
