The Colosseum had a retractable roof, operated by a crew of sailors, almost 2000 years before any modern stadium. It was called the velarium: an enormous awning of canvas and rope that could be drawn across the open top of the arena to shade fifty thousand spectators from the Roman sun. It was so large and so complex that ordinary labourers could not manage it. The Romans brought in sailors from the imperial fleet, men who spent their lives handling rigging and sail, and stationed them at the top of the structure to extend and retract the canvas as the day moved. A building that has stood, roofless to our eyes, for centuries was in fact designed to be covered. That is the pattern with the Colosseum: almost everything about it was way more advanced than it looks today... Construction began around 72 AD under the emperor Vespasian. Once completed, it was the largest amphitheater in the Roman world: an elliptical structure of stone, concrete, and travertine, 189 meters long, rising as high as a modern fifteen story building. It could hold around 50,000 people and the staircases allowed that entire crowd to enter and leave with a speed that modern stadium designers still study. Beneath the arena floor lay the hypogeum, a hidden labyrinth of tunnels, cells, and machinery. Animals and gladiators waited there in the dark. Numerous trap doors opened in the wooden floor above them, and through hidden lifts and ramps a lion, a leopard, or an armed man could rise into the daylight as if from nowhere, in front of tens of thousands of people. The Romans knew that they had built something that would outlast them so completely that the Colosseum became, for the people who came after, a measure of the world's own endurance. In the 8th century, an epigram attributed to the Venerable Bede offered a prophecy that has never lost its allure: "As long as the Colosseum stands, so shall Rome; when the Colosseum falls, Rome shall fall; when Rome falls, so falls the world." If you enjoyed this, I write a weekly newsletter read by over 50,000 people who love rediscovering the beauty of the past. You can join us here: If you'd like to support my work, a paid subscription is what makes it possible.

Bernhard Riemann’s 1854 breakthrough proved that geometry isn't just about flat planes: it’s about the intrinsic curvature of space itself. This image perfectly breaks down the three fundamental geometries that govern our universe: > Zero Curvature (Euclidean): The classic flat plane. Parallel lines never meet, and triangle angles sum exactly to 180°. > Positive Curvature (Elliptical): Think of a sphere. Lines eventually intersect, and triangles "bulge," exceeding 180°. > Negative Curvature (Hyperbolic): A saddle-like surface where lines diverge rapidly, and triangle angles sum to less than 180°. By treating these surfaces as "manifolds," Riemann provided the mathematical framework that Albert Einstein later used to describe the warping of spacetime in General Relativity.

2034 Earth–Venus–Mars opportunity looks promising. 10–15 on-orbit refueling operations may be needed to make a crewed ship full. Most can be done at an altitude of 180–200 km, made possible by Starship’s size. The final refueling may be performed at a higher altitude of ~2000 km, just below the Van Allen belt. Earth departure on 2034-08-21 from 2000 km orbit. A Trans-Venus Injection burn of ~3.7 km/s will place the ship on an Earth–Venus–Earth free-return trajectory. Venus flyby is expected on 2034-12-19, 120 days after departure. Two weeks before the encounter, if the mission proceeds as planned, a 25-m/s maneuver will shift the trajectory from Earth-return to Mars-bound. If not, the ship will free return to Earth in September 2035. The Venus gravity assist will send the ship into another Earth free-return trajectory, with Mars flyby around 2035-06-02. One week before reaching Mars, a system health check will determine whether to commit to Mars Orbit Insertion. If it’s GO, a small 10-m/s manuever will put the ship to less than 100 km altitude periapsis. Otherwise, a Mars flyby will lead to an Earth return in May 2036. The ship will enter the Martian atmosphere at about 9.4 km/s, performing an aerobrake to slow to 4.88 km/s and capture into a 100x140000 km, 7-day period high elliptical orbit. At apoapsis, a 50-m/s plane change will align the inclination with Mars’ equator, followed by additional aerobraking to remove about 650 m/s of velocity, placing the spacecraft in a 120x6128 km orbit. A 550-m/s burn at 6128 km altitude will then adjust the trajectory into Phobos orbit. The ship will stay at Phobos for about 7 days. The Mars–Phobos L1 point is only about two miles above Phobos’ surface, and Mars would dominate nearly half the sky, appearing about 80 times larger than the Moon from Earth. The ship will depart for Deimos afterward. Two burns totaling roughly 750 m/s will transfer the ship from Phobos to Deimos. And the ship will stay at Deimos for 7 days more. From Deimos, the ship will raise its apoapsis to form a 20000x140000 km altitude, 7-day orbit, requiring about 420 m/s of delta-v. At apogee, a 50-m/s burn will adjust inclination and lower periapsis to ~500 km for final Trans-Earth Injection. If time and propellant allow, the orbit can be aligned to a polar inclination for Mars ice-cap observations before departure. A Trans-Earth Injection burn at 500 km altitude, requiring 1.5–1.6 km/s of delta-v in early July 2035. If departure on the first days in July, Earth arrival is expected in December 2035. If missed that window, a March 2036 arrival may look more feasible. Nominal mission duration: 490 days, with 30 days in Mars orbit and 14 days at Phobos and Deimos. Two planets, two moons for 3.7+0.025+0.010+0.05+0.42+0.55+0.75+1.55=7.06 km/s Δv

Elliptic $120M Series D Round⚡️ 📑 About: @elliptic is a company that provides blockchain analytics and risk-management tools focused on digital assets. 🤝 Investors: One Peak (Lead), Nasdaq Ventures, @EvolutionEquity, @AlbionVC, @jpmorgan, and @deutschebank 🏷 Valuation: $670M

HashKey uses Elliptic's comprehensive blockchain intelligence suite to power their KYA and KYT screening processes. This critical infrastructure enables the Hashkey team to identify and assess high-risk virtual assets.

HashKey uses Elliptic's comprehensive blockchain intelligence suite to power their KYA and KYT screening processes. This critical infrastructure enables the Hashkey team to identify and assess high-risk virtual assets.