A pint’s a pound the world around. Traditional American mnemonic A pint of water’s a pound and a quarter. Traditional British mnemonic There’s something odd going on there, isn’t there? I learned that British mnemonic at primary school, and I can still vividly recall my first encounter with the American version—in a Robert Heinlein juvenile … Continue reading Pints And Pounds
OK, another mathematical one. This is the fourth in a series of posts about the orbits followed by the Apollo spacecraft as they travelled to and from the moon—something I suppose is getting a little more topical now that NASA has finally got underway with its planned return to the lunar surface. I started with … Continue reading Converting Apollo State Vectors To Orbits
In the following pages I shall try to trace the unpremeditated steps by which a few army officers, with no initial thirst for exploration, and no desire to do anything unusual except to see the country they were in came gradually to break away from this conventional city outlook towards things outside; and how, beginning … Continue reading Ralph Bagnold: Two Memoirs
A while ago I wrote a post entitled “How Apollo Got To The Moon”, which featured a few orbit graphics generated in Celestia, like the one above (which shows the orientation of Apollo 11’s departure orbit relative to the most intense region of the Van Allen Radiation Belt). I got a few enquiries about the data … Continue reading Finding Apollo Trajectory Data
Robert A.J. Matthews published this seminal bit of applied physics in 1995. The journal reference is European Journal of Physics 16(4): 172-6, and you can access the full paper at ResearchGate, here. For his efforts, he was awarded an Ig Nobel Prize in 1996.
Matthews was the first (but by no means the last) to use mathematical physics to explore the popular claim that “dropped toast always lands butter-side down”. The usual “explanation” invoked for this perceived rule is Murphy’s Law—“If anything can go wrong, it will”—but Matthews sought to show that there were sound physical principles underlying the phenomenon.
1. All planets move in elliptical orbits, with the sun at one focus.2. A line that connects a planet to the sun sweeps out equal areas in equal times.3. The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. Kepler’s Laws of Planetary Motion (formulated … Continue reading Keplerian Orbital Elements
If the alien cyborgs have constructed this miraculous planet-coring device with the precision I would expect of them, I predict we shall plunge entirely through the center and out to the other side. Gregory Benford Tides Of Light (1989) There’s an old puzzle in physics, to work out how long it would take a person … Continue reading Falling Through The Earth
I had a photograph of my own to illustrate this post, but it was a bit rubbish. I was inspired to write about helium when I discovered the wreckage of a mylar-foil helium balloon, like the one pictured above, tangled in a gorse bush on the slopes of Newtyle Hill. It’s the second foil balloon … Continue reading Helium
No matter how many times he considered it, Jophiel shivered with awe. It was obviously an artefact, a made thing two light years in diameter. A ring around a supermassive black hole. Stephen Baxter, Xeelee: Redemption (2018) I’ve written about rotating space habitats in the past, and I’ve written about relativistic starships, so I guess … Continue reading Relativistic Ringworlds
Thus, with all Einstein numbers of flight [velocity as a proportion of the speed of light] greater than 0.37 a major dark spot will surround the take-off star, and a minor dark spot the target star. Between the two limiting circles of these spots, all stars visible in the sky are coloured in all the … Continue reading The Myth Of The Starbow