Thursday Throughput: When You Get Caught Between the Moon and Suez Canal
Photo by Dave Minogue from Toronto,Canada, Canada, CC BY-SA 2.0
[ThTh1] Astronomy is probably the eldest of the sciences. That’s because it was, for many millennia, an extremely practical science. Astronomy allowed the first measurements of the passage of time. It allowed ancient peoples to know when winter would end, when to plant crops, when to sew them. It allowed the first attempts at navigation by creating a fixed grid of stars sailors could orient themselves by.
This week, we got another great demonstration of the practical side of astronomy.
To get the giant container ship blocking the Suez Canal unstuck, engineers needed the stars to align. Actually, the sun, Earth and moon.
After several days trying to dislodge the Ever Given cargo ship, which had veered off course and embedded itself in the side of the canal, the salvage team pinned their hopes on this week’s full moon, when, beginning Sunday, water levels were set to rise a foot-and-a-half higher than normal high tides. That would make it easier to pull the 1,300-foot vessel out from the side of the canal without unloading a large number of the 18,000 or so containers it was carrying.
The rise and fall of tides are, to first order, determined by the moon. Just as the Earth exerts gravitational force on the Moon, the Moon exerts force upon the Earth. That force had a tidal effect. The force of gravity the Moon exerts on the side of the Earth facing the Moon is slightly stronger than the force exerted on the center of the Earth, which is stronger than the force on the side facing away from the Moon. This has little effect on the Earth itself. But it causes the water on the surface to slosh around. On the side facing the Moon, the Moon’s gravity pulls the water closer, causing a high tide. On the side facing away, the Moon’s gravity is lower and the lets the water drift away, causing another high tide. The balance is found by the water being lower between those two points — low tide.1
But that’s to first order. To second order, the Sun also exerts a tidal effect on the Earth. The Sun is much more massive than the Moon but is much further away, so it’s a lesser effect. The main way it shows up is when the Sun and Moon are aligned. If they are on opposite sides of the sky — which they are at full moon — their gravitational effects add up and the tides are strengthened into what is called a spring tide.
When the Sun and Moon’s gravity lines up, tides are stronger.
Practically, this meant that when high tide hit this week, the oceans were about seven feet higher than normal. This, added to the 60 feet the Egyptians had dredged around the ship, allowed it to break free.
The WSJ makes reference to a “supermoon”. The Moon doesn’t orbit the Earth in a perfect circle but in an ellipse. Its actual distance varies between 224,000 and 251,000 miles. This particular spring tide occurred within about a week of perigee. The moon was bit closer than normal, meaning its gravitational effect was a bit stronger. But that effect is small compared to the overall tidal effects.
Still, it’s good to see basic astronomy playing a role in this story.
[ThTh2] Yesterday, a claim circulated that Florida had understated the number of COVID deaths by 14,000. This claim is not true. What the study claims is that between March and September of 2020, there were 19,000 excess deaths in Florida. This is 5,000 more than the official COVID-19 death tally of 14,000 but it’s not clear that these deaths are COVID-related. National Review actually bothered to call the scientists involved who clarified this point and noted that Florida’s undercount is with the normal range that many states and countries have seen. There are rules about how a COVID-19 deaths gets counted and so not every death is counted. This is something that has been true since the pandemic started.
There is plenty to criticize about Florida’s COVID response. While caseloads are falling, positivity rates are starting to come up again. Then again, intrastate comparisons are hard (a subject Allahpundit gets into here). But the idea that they are hiding masses of COVID-19 corpses is not born out by this study. Quite the contrary, in fact.
[ThTh3] Speaking of COVID, 60 Minutes dropped a segment looking at the WHO’s investigation into the origins of COVID-19 and concluded that it was basically a joke. I tend to agree. We have no evidence that COVID-19 escaped from a lab in Wuhan. But China’s opacity on the subject is not helping.
[ThTh4] I’ve always disliked bottom trawling as a fishing method. Now it turns out it may be even worse than we thought.
[ThTh5] I find the antikythera mechanism endlessly fascinating. Our ancestors were ridiculously clever.
[ThTh6] Speaking of clever ancestors, ever wonder why amphorae have pointed bases? Wonder no more.
[ThTh7] And yet more from our clever ancestors.
[ThTh8] If you want a really technical explanation for the tension in cosmology that could blow a hole in our understanding of the universe, here you go.
[ThTh9] Noah Smith has a good post on why it’s a bad idea for experts to lie to the public, even when they think it’s for the public’s own good.
[ThTh10] I love me song long-baseline data.
Now that's what I call long baseline data!
Source: @Datagraver pic.twitter.com/JRZqfQel9R— Kevin Schawinski (@kevinschawinski) March 29, 2021
[ThTh11] Black holes are so cool.
Our first amazing, polarized images from the @ehtelescope M87 are out! Polarization helps us map the structure and the strengths of the magnetic field near the black hole horizon and shed light on questions like how jets form. Watch our cool animation https://t.co/lA9bAEA2HS pic.twitter.com/F4pH9KBlEX
— Feryal Ozel (@feryal_ozel) March 24, 2021
[ThTh12] I am amazed by how big the filters are for this telescope.
[ThTh13] We’re getting a bit closer to usable superconductor. The pressures required are still extreme but we’re gaining a huge amount of insight.
[ThTh14] Investigation continues into the supposed rash of blood clots connected with the AstroZeneca vaccine. I should emphasize that these incidents are still extremely rare, even if they are connected.
[ThTh2] I’ve been thinking recently that there’s something I’ve been calling the effective unprotected contact rate, and that no one has any idea how high it has actually been in the different parts of the country. Also that it is, to a considerable extent, independent of whether or not there was a mask mandate — eg, in some places there were “secret” large mask-free gatherings despite any mandate, and in some places people followed good protocols even though there was no mandate. I expect this will become a hot study topic for PhD candidates in epidemiology in coming years. They’ll start by trying to work backwards from the infection/death data to estimate what the actual contact rate had to be.Report
The SF Bay Area was generally excellent with mask compliance both indoors and outdoors. However, it was clear early on that a lot of people had very big pods (even if inadvertently) and were seeing friends and family. I know people who have not seen family for a year despite living close by and I know people who have seen family like the pandemic is non-existent even if otherwise trying to be good. I expect that even liberal cities like SF have had a fair number of indoor gatherings. Maybe not as big as before but existent none the less.Report
ThTh6: It’s amazing how much we’ve come to understand fluid mechanics without the underlying math. Just the intuitive understanding that comes from living in a fluid. It even plays into my work doing CFD. Being able to look at certain plots and images of the flow field can let me know if a completed simulation is garbage or not.Report
Dumb math question about ThTh14.
Like, let’s say that the AZ vaccine causes blood clots and it’s not a weird data thing like the Cancer Cluster Power Line thing that we had going on in the 90’s.
How many blood clots does it cause?
Let’s say that the vaccine protects against Covid about as well as Moderna or Pfizer or J&J.
And let’s say that the Covid kills some percentage of people who get it.
And let’s say that the AZ shot is available right now but Moderna or Pfizer or J&J won’t be available for at least X months.
Will waiting X months cause more deaths than the AZ shot?Report
Interesting question. Too many variables for an accurate answer but we can ballpark it.
Let’s say the odds of death from the AZ vaccine are one in a million (one in a hundred thousand of getting clot). That means vaccinating, say, the entire population of Germany would cause about 100 deaths. Let’s be really pessimistic and say a thousand if the odds are ten times that.
Right now, Germany is losing 200 people a day to the virus. So in a week, you’d be better off with the vaccine.Report
My intuition was to say that the AZ vaccine has less risk than the blood clots.
But I also know that I got the Moderna and, as such, it’s real easy for me to say “other people should just take the AZ shot!”
Thanks for doing the math.
It seems that withholding the shot from people (even as an option!) is costing lives.
That seems to be bad.Report
Some countries are doing it based on age since COVID is much more dangerous to those over 50. That’s … not entirely unreasonable. But there’s zero reason to delay giving it to at-risk populations.Report
ThTh3: Maybe this is my own conspiracy-theorist coming out, but I can’t help but call BS on just about everything Covid-related coming from official Chinese sources. I mean, China — where this whole thing started — went from thousands of reported daily cases in March to basically zero overnight.
But I never see this discussed. Is it just accepted wisdom that their numbers are bunk? Or did they achieve that through authoritarian means no other country would repeat? Or are they some miraculous Covid success story?
https://www.worldometers.info/coronavirus/country/china/
I mean, those charts just seem impossible.Report
There was a lot of really, really sketch stuff happening with regards to China/COVID.
Did you ever see this interview?
Anyway, there is a lot of money in doing what China wants and there is a lot of money to be lost if China gets ticked off. It’s hard to not keep that in mind when you hear stuff on NPR like this:
I mean, do you believe the guy?Report
That’s a much harder topic for me to really speak to. Where did the virus come from? Heck if I know! Does the “official” explanation make sense? Yea. Does the conspiracy? Yea.
But the basic numbers reporting? The official numbers make ZERO sense. So either A) I’m dumb and can’t understand why they’re right or B) they aren’t right.Report
Comment in perma-mod, it seems.Report
It was deep in the spam.
I have no idea why it was in the spam. Well, I have conspiracy theories about why it was… anyway, I dug it out.Report
This title is laugh out loud funny! Love itReport