The Bussard ramjet won’t work as well as you think it could. A new study does the math on John Fishback’s contribution to the ramjet—gathering protons from the interstellar medium for the ramjet’s fusion drive via a magnetic scoop—and concludes that while it’s physically possible, there are substantial constraints: the cut-off speed is lower than expected, limiting the effects of time dilation, and the magnetic field would have to be something like 4,000 km wide and 150 million km long in order to work. In other words: for certain very preposterous values of physically possible. [Universe Today]
Category: Astronomy & Space
We marked the 50th anniversary of Apollo 11 last week, which means that the next step is to put all our moon-landing related nostalgia away until the next milestone anniversary, or until another of the remaining Apollo astronauts dies.1
If, on the other hand, all this attention has piqued your interest in the moon landings, the Apollo program, and the history of crewed spaceflight generally speaking, I have some suggestions as to what you should watch and read next. There are, of course, plenty of books and documentaries on this subject, but these will give you a general overview, with increasing levels of detail.
I have a bone to pick with news stories that declare, hyperbolically, whenever a location is in the midst of a deep freeze, that it’s “colder than Mars”—stories like this one from CTV News or this one from The Atlantic.
What exactly do they mean by “colder than Mars”? Mars is a planet—one that, like Earth, has an atmosphere, albeit thin, and weather and seasons. Mars can get as cold as –143°C (–226°F) and as warm as 35°C (95°F) in spots. Mars’s mean temperature is
It turns out that what reporters really mean is the current temperature at Gale Crater, as measured by the Rover Environmental Monitoring Station on the Curiosity rover. It also turns out that there’s a handy widget that gives the current conditions as measured by REMS. As I write this, the air temperature on Mars is –19°C and the ground temperature is –6°C (the difference is because the air is so thin).
Since it’s –19°C right now where I live, yes, Mars—or at least Gale Crater, which is not the same thing (again: apples to oranges)—is just as cold. But temperatures as high as 20°C (68°F) and as low as –127°C (–197°F) have been recorded at Gale Crater. It’s no trick for a Martian summer to be warmer than a Canadian winter, but even the daytime highs of a Martian winter can be warmer than a Canadian winter. Because the air is so thin, the Martian surface heats quickly when it’s sunny, and the temperature can swing as much as 100 degrees.2
I know that hyperbole is an essential part of talking about how goddamn cold it is out there (see also: using wind chill instead of temperature), but honestly, Mars isn’t a useful point of reference.
So I mentioned that I might try to get a photo of the solar eclipse, weather permitting? In the end, weather permitted — in fact, everything that could have prevented us from observing or photographing the eclipse failed to do so: clouds were intermittent until after the maximum, the tall trees around our house didn’t block our view, and we were even able to find all the gear we needed in time (some hadn’t been unpacked yet).
I used my usual method for photographing the sun: a digital SLR connected to my 5-inch Schmidt-Cassegrain telescope at prime focus, using a visual solar filter. It turned out well: despite the heat (atmospheric shimmer, you see), the filter (Mylar) and the need to focus manually, I managed more than a few clear shots. Above is a shot from the eclipse’s maximum extent (it was a partial eclipse here). I’ve uploaded a few other photos here.
You know, I think this is the first time I’ve done any solar observing or photography in more than five years. I’m glad I found an excuse to do it again.
I’m outside the path of totality for next week’s solar eclipse, but don’t feel bad for me: I’ve already had my total eclipse experience. I had just turned eight years old when the total solar eclipse of February 26, 1979 came to my home town of Winnipeg, Manitoba. In 2009, I remembered the event in a blog post:
Some people spend thousands of dollars to see a solar eclipse; I was lucky: the eclipse came to me. But to see it, I had to stay home from school that morning. My father’s recollection is that for some nonsensical reason or other, the schools were going to keep the kids inside during totality. Screw that, said my parents, who had three science degrees between them. So I saw the last few seconds of totality from my front porch.
Since then, video of CBC Manitoba’s coverage of the eclipse has been uploaded to YouTube (see above). I remember watching this. (Even weirder, the meteorologist showing the satellite image at the start of the coverage is a friend of the family.)
If you’re in the path of totality, enjoy the eclipse on Monday (weather permitting). As for me, I’m going to be all nostalgic about the one I already saw.
(I think I might try to get a photo of the partial eclipse—again, weather permitting. I do have the gear for solar photography.)
At The Map Room: Mapping the August 2017 Solar Eclipse.
On December 25 the American astronomer Vera Rubin, whose discovery that galaxies were rotating too fast given the mass of their constituent stars provided evidence for the theory of dark matter, died at the age of 88. Her obituaries note the challenges Rubin faced as a pioneering woman in an overwhelmingly male field: prevented from doing graduate work at Princeton, she got her Ph.D. at Georgetown in 1954; in 1965 she became the first woman allowed access to the Palomar Observatory. In the June 2016 issue of Astronomy, Sarah Scoles decried the fact that Rubin’s discovery was somehow insufficient for a Nobel Prize, which she will now never win.
Inasmuch as Rubin was a pioneer, she was not the first woman in astronomy, nor the first to obtain a Ph.D., nor the first to be responsible for a discovery that fundamentally reshapes our understanding of the cosmos—nor the first for whom recognition was unfairly delayed. Some of the women who came before her are the subject of Dava Sobel’s new book, The Glass Universe, coincidentally out this month from Viking.
As hobbies go, astrophotography has murderously high barriers to entry in terms of equipment costs and skill, and the money and time required to acquire each. Fortunately there’s an exception. Taking pictures of the Moon requires neither specialized equipment or skill: my first photo of the Moon was taken with an entry-level digital SLR and a telephoto zoom lens, and people have used smartphones to take decent photos of the Moon through the eyepiece of a telescope.
From that first shot I graduated to prime focus lunar photography, using adapters to connect my SLR to a telescope, making that telescope essentially a gigantic telephoto lens. Here’s an album of those prime focus photos.
But those aren’t the only ways to shoot the Moon, as Nicolas Dupont-Bloch demonstrates in his magisterial new book out this week from Cambridge University Press, which is coincidentally called Shoot the Moon: A Complete Guide to Lunar Imaging.