Hackaday Links: April 14, 2024

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The Great American Eclipse v2.0 has come and gone, sadly without our traveling to the path of totality as planned; family stuff. We did get a report from friends in Texas that it was just as spectacular there as expected, with the bonus of seeing a solar flare off the southwest limb of the disk at totality. Many people reported seeing the same thing, which makes us a bit jealous — OK, a lot jealous. Of course, this presented an opportunity to the “Well, ackchyually” crowd to point out that there were no solar flares or coronal mass ejections at the time, so what people saw wasn’t an exquisitely timed and well-positioned solar flare but rather a well-timed and exquisitely positioned solar prominence. Glad we cleared that up. Either way, people in the path of totality saw the Sun belching out gigatons of plasma while we had to settle for 27% totality.

The eclipse also presented plenty of hacking opportunities for YouTubers in our community. Matthias Wandel went to great lengths on short notice to build a solar tracker for photographing the eclipse, while Gabe Emerson from “saveitforparts” threw his little radiotelescope rig in the car and drove down to totality to listen to the Sun during the eclipse. Jeff Geerling brought three generations along for his eclipse party, which resulted in some wonderful photographs and rubbing elbows with Destin from “Smarter Every Day.” Also interesting is this analysis of internet traffic during the eclipse by content delivery concern Cloudflare — or is that Cloudprominence? — which shows remarkable dips in internet use during totality. The dips tracked across the continent from Mexico to Canada and lined up perfectly with the Moon’s shadow.

In non-eclipse news, someone crunched the numbers on the forces involved when the MV Dali rammed into the Francis Scott Key Bridge in Baltimore, and — wow! Taking into account the mass of the loaded container ship and its change in speed during the collision, the vessel imparted something like 26 million pounds of force on the bridge. If our calculations are correct, that’s over 115 million newtons, which, as the article notes, is equivalent to 66 fully loaded semi trucks crashing into the bridge at highway speed all at once. No wonder it collapsed like it was made of toothpicks. Perhaps the most interesting thing we learned from this article was that there’s a standard reference value for the force exerted on a bridge abutment by a truck crash, and it’s 400,000 pounds.

Git is one of those things that’s so incredibly useful and so tightly integrated into our culture that it’s hard to remember what we did for source control before it came onto the scene. But source control goes way, way back, perhaps further than you realize, as this series of articles on source control systems documents. This article is the first of four parts and focuses primarily on SCCS and RCS. We were surprised to learn that source management only became a thing in the 70s when video terminals and magnetic mass storage became more ubiquitous. We’re looking forward to the second part, which covers the bad old days of CVS, SourceSafe, and ClearCase, which is where we first fell down the source control rabbit hole.

And finally, we wanted to share this fascinating video on the unlikely origins of the first desktop computer: the guidance computer of the Minuteman I ICBM. In 1962, computers filled entire rooms, but the Autonetics D-17B came in at a mere 28 kilos, a remarkable accomplishment in computer miniaturization. About 800 of the general-purpose digital computers were fielded, and when the Minuteman I gave way to other, more capable ICBMs, the decommissioned computers were distributed free of charge to universities and other institutions. The chief obstacle to putting one of these machines to work seems to have been coming up with a power supply, but once that was accomplished, a “Minuteman Computer Users Group” stood ready to help you get going.

10 thoughts on “Hackaday Links: April 14, 2024

  1. ” the vessel imparted something like 26 million pounds of force on the bridge.”
    For reference, the ship mass was 300 million pounds. The force exerted was less than ten percent of the mass of the ship.

    For the truck analogy: “…by a truck crash, and it’s 400,000 pounds.” A truck maximum GVW is typically 80,000 lbs. It’s a crappy, meaningless comparison.

    1. Not really…. The truck is assumed to be moving at highway speed (I can’t be sussed to look up the actual, but greater than 120Km/h or 33m/s), and have designed in force limiting structure designed to limit maximum acceleration to a survivable level. The ship was moving at roughly 9kt (roughly 4.6m/s, less than 15% of the truck speed, for a v^2 of about 2%) with a very different crush structure design intended for keeping the ship afloat rather than maximum acceleration.

      The comparison has little to do with the mass of the vehicle, or the relation of the mass tot he force at impact. The net force is what matters (and the net impulse, if the time of the force is low, but in neither of these cases is the time shorter than the expected time to failure under the force. In the other case, the impulse gives a measure of the expected damage)

      It is true that we generally do not expect 66 trucks to impact at the same time. but to give a reasonable impression of the impact, this is a pretty good measure.

      1. No, it’s not. The momentum of 140-ish kilotons of ship moving at 4.6 m/s is eight times that of 66 trucks traveling at highway speed.

        Even though it was moving at only a seventh of highway speed, there were 5000 truckloads of containers on that boat.

        “66 trucks” is not a reasonable comparison.

    2. It does seem low but it comes from a person with a PhD in Civil Engineering and who is a professor at RIT.

      I think the difference may hinge on the duration of the collision, an estimated 4 seconds for the ship as opposed to a near instantaneous duration for a truck.

    1. As seeing Newton weighted about 143 at the time, and Einstein weighted 175, I would say 94 million Ensteins. This is assuming 300 years old record and 80 years old record are both accurate.

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