The Oort Cloud, theorized by Jan Oort in 1950, is a vast, icy structure beyond the Solar System, containing trillions of objects. It is divided into the sparse outer cloud and the denser, doughnut-shaped inner cloud. Evidence for its existence includes the orbits of long-period comets. Galactic tides and interactions with giant planets likely contributed to its formation and distribution of icy bodies.
Author: Steve Hurley
Hi I am Steve Hurley. Although I work in the IT industry. I studied for a PhD in astronomy in the 1980s. My real passion is explaining scientific concepts to a non-scientific audience. My blog (explainingscience.org) covers various scientific topics, but primarily astronomy. It is written in a style that it is easily understandable to the non scientist.
Publications and videos
For links to my books and videos please visit www.explainingscience.org
Venus the Morning Star
Anybody who has observed the eastern sky just before sunrise in the last few weeks will have noticed a brilliant white object - the planet Venus, also known as the morning star. It is brighter than any other planet and at its brightest ten times brighter than Sirius the brightest star. Its brightness has often… Continue reading Venus the Morning Star
The Lyrids 2025
The night of 22/23 April 2025 will be the peak of the Lyrids, one of the most famous prolific meteor showers. Meteors (also known as shooting stars) are bright streaks of light caused by small lumps of rock or metal called meteoroids hitting the Earth’s atmosphere at very high speed. As they pass through the atmosphere they get… Continue reading The Lyrids 2025
Hydrogen-Powered Vehicles: A Green Alternative?
Hydrogen vehicles use fuel cells to produce electricity, but their carbon footprint remains significant due to hydrogen production methods, primarily steam methane reforming. Additionally, while hydrogen can be produced greenly, green hydrogen is currently expensive and only makes up a small portion of global production. The only hydrogen car available in the UK is the Toyota Mirai, with limited refuelling infrastructure posing challenges for broader adoption.
Challenges of Electric Vehicle Battery Technology
Updated November 25 2025 In what is a departure from my usual topics of astronomy and space science, I've written a series of posts on the transition to electric vehicles. In this post I'll discuss the issues of the lifetime of EV batteries, their lower energy density compared to traditional hydrocarbon fuels and the secondhand… Continue reading Challenges of Electric Vehicle Battery Technology
Explaining Science 