A Supermoon is a Full Moon which appears larger than usual in our skies. The Moon’s orbit is not perfectly circular, but is elliptical. This means that there is a point in its orbit that is closer to Earth than any other (called ‘Perigee’) and a point that is further (‘Apogee’). The orbit takes 27.3 days, so the Moon is at Perigee exactly once every 27.3 days. However, the cycle of phases takes a little longer (Because they are … Continue reading →
Dear Urban Astronomer I just read your article about “what is the speed of light.” I’m so surprised (and amazed) that light travels faster in a vacuum than in (atmosphere?) – does this mean that LIGHT is actual…”stuff” ? It might sound silly to you, but I find it quite hard to comprehend! Does this mean that light has a “mass”? It’s very cool, and opens up a whole new world of symbolic drama-movie themes. Jody … Continue reading →
Every now and then, when people learn that the Urban Astronomer is a Christian, some wag asks “So why should we take you seriously if you believe that the universe is six thousand years old?”. And I battle to answer, because where do you start with such a retarded question? See, the latest round of partisan thinking is “Almighty Skeptical Atheism” vs “Almighty Faith-based Literalist Christianity” (since, as the dominant religion in the West, Christianity is the obvious target for … Continue reading →
Escape velocity from the surface of the Earth is about 11.2 kilometers per second (or just over forty thousand km/h, or twenty five thousand mph), meaning that if you want an object to leave Earth and never fall back, you have to throw it at least that fast. How does that work? Well as you’ll remember from high school physics, Newton’s law of universal gravitation tells us that an object’s weight (The downward force applied by gravity) depends inversely on … Continue reading →
A few evenings ago, a small group of friends came to my house to watch the Geminids meteor shower. We put a lot of effort into preparing our for the experience by chopping down trees which obscured the view, stocking up on charcoal and meat for the braai, setting out comfortable garden chairs and inviting the right people. By all accounts, the shower exceeded the most optimistic predictions and would have been a marvellous show had we not been clouded … Continue reading →
