BAN #123: Lunar rockrolling, Two time travel tales

June 17, 2019 Issue #123

[Saturn image credit: NASA / JPL / Space Science Institute / Gordan Ugarkovic]


Subscribers rock and roll.


Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a short description so you can grok it

The Moon seems unchanging, always there, always the same… well, except for the phases, but that’s just an apparent change, not a physical one. I mean that if you take a telescope and look at, say, Mare Imbrium one night and then wait ten years to look at it again, it’ll look pretty much the same.

But that’s not really true. Forces work slowly on the Moon, but they do work. Sunlight and micrometeorite impacts erodes features away, changing their reflectivity over millennia and eons, for example.

Geological changes happen on the Moon over vast timescales, too. If you’re a geologist, standing on the Moon would flood you with evidence of change. To someone like the rest of us, though, those changes aren’t as obvious.

But some are. One of my favorite things to see on the Moon is something that wouldn’t have occurred to me until I did see one: rolling boulders.

I don’t mean we see them actually rolling! But it’s pretty clear they did. Like, here:

[Credit: NASA/GSFC/Arizona State University]

Wow! I love this shot. It’s from the Lunar Reconnaissance Orbiter, and shows a whole bunch of rocks that have rolled downhill. And they don’t roll, they bounce! The rocks are irregular in shape, so a bump on the rock (or an irregular surface feature) can cause it to fly up off the surface briefly, aided by the low gravity. When that happens the trail the rock leaves in the dusty surface isn’t continuous, but dashed, broken.

The boulder at the top of the frame is huge, 32 meters in size. That’s longer than a tennis court! What a sight that must have been; you can see that the distance between points of impact along the trail are 50 meters or so. I wonder how high it got off the ground before slowly falling again, seemingly flowing in the 1/6th Earth gravity?

I saw this image on the Lunar Reconnaissance Orbiter Camera blog page, and as I have said many times before I cannot recommend it enough. The images are fantastic, and there’s always some cool science to learn there. It’s always fun to see what they put up there.



I recommend

Something I think you’ll like

I recently watched two time travel movies I really liked.

But first: Warning: Extremely minor spoilers for The History of Time Travel. If you want to be absolutely sure to remain spoiler free, I’ll say up here I liked this movie and you should watch it; click the link just below.

[This is spoiler space. Hey, I’ll insert a pretty picture of the galaxy M83 to put some distance to the spoilery stuff just to be sure.]

[Credit: SPECULOOS Team/E. Jehin/ESO, from this blog post.]

OK, so:

I was poking around on Amazon Prime video recently, just hoping to find some bit of low-grade indy scifi to amuse me, and almost skipped past The History of Time Travel. It’s a movie done in fake documentary style, and that’s a format that can achieve transcendent brilliance (This Is Spinal Tap), but more often becomes tedious in lesser hands than Rob Reiner.

Still. Why not. So I hit play.

I’m really glad I did. It’s actually quite clever, which is what I really like in a time travel story. It starts off a bit slowly — going into the backstory of the man whom we all know (in the context of the movie) invented time travel years ago. Heck, there’s a museum exhibit about him! So experts testify, his story unfolds… and I swear to you, I was thinking in my head “OK, I get it, and if this doesn’t get moving faster in the next minute or two I’ll stop watching” when the movie took a really solid left turn.

Now here’s the ironic bit: I can’t tell you what it is. It’s of course important to the story, but it’s also critical to the whole way the movie is laid out, and I can’t even hint at what it is without ruining the fun of experiencing it for yourself. I’ll admit I had a pretty decent 20 seconds of confusion when it hit. I thought I had missed something and was about to rewind when I realized what was what. And even after the twist, right when I was thinking again “OK, cute, I get it, but get on with this instead of just hammering the twist over and again” I suddenly figured out where the whole movie was heading and realized they got me again.

And that’s all I can say. Seriously.

I wish I could tell you more about it, since getting people to see something generally means revealing something about the plot. But nope. I can tell you I really liked it, and I recommend it, and of course YKMV* but I think this movie deserves a bigger audience than it’s had. So there you go.

I also just recently watched See You Yesterday, a time travel movie on Netflix produced by Spike Lee. I thought it was great, with some real gravitas as well as solid laughs. The science was a bit silly, but the science isn’t the point at all; it was only used as a vehicle so I didn’t sweat the details.

I will say that it was really cool to see two black kids, one a young woman, so dedicated in science and so obviously wickedly intelligent. Diversity on the screen matters, and it really helps kids especially to see role models like them in movies and TV shows. The stereotype of the middle-aged, white, balding, bearded scientist has to go. And yeah, I look in the mirror every day, and I still say that.

The social message, about cops killing black men, is hard-hitting and well done. Minor spoiler: I speak with outside experience, here, obviously, but the message of changing the specifics without being able to change the general outcome was stunning in this context, especially (no spoiler) the literal last few seconds of the movie. The struggle with racism — especially these devastating shootings — will continue for quite some time. But movies like this help shine a light on it, and it’s good to see.

* Your Kilometerage May Vary. C’mon folks, you know by now I’m all metric.


Et alia

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