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
I studied physics because it explained things that I was interested in. It allowed me to look around and see the mechanisms making our everyday world tick. Best of all, it let me work some of them out for myself. Even though I’m a professional physicist now, lots of the things I’ve worked out for … Continue reading Helen Czerski: Storm In A Teacup
This series of posts is about what the sky would look like to an observer travelling at close to the speed of light. In Part 1, I described the effects of light aberration on the apparent position of the stars; in Part 2, I introduced the effects of Doppler shift on the frequency of the … Continue reading The Celestial View From A Relativistic Starship: Part 4
This is the third of a series of posts about what the sky would look like for the passengers aboard an interstellar spacecraft moving at a significant fraction of the speed of light, like the Bussard interstellar ramjet above. In the first post, I wrote about light aberration, which will cause the apparent direction of … Continue reading The Celestial View From A Relativistic Starship: Part 3