I didn't know they already had machine learning and model fitting algorithms in the 1800s, but here we are...
Intuitively you would think that the tide is being formed because the Moon is "lifting up" the water at the point closest to the Moon. But this contribution is actually very miniscule to the tidal effect. Instead the bulk of the tides are produced about 45 degrees away where the tidal force is parallel to the Earth's surface. This has the effect of dragging the water closer to the tidal bulge.
Basically, a summation of sinusoids.
For me, the worst are posts about scale and things I won't need, like "You don't need kafka" or "your data isn't actually big data" or "don't horizontally scale, just get a bigger server"
I get that I am not the target audience and there are people for whom those statements are true, but I am running Kafka clusters with data from 10s of thousands of servers, I absolutely can't move that to a single machine.
I wish they would phrase it as "Tides are weirder than most people think", although that probably doesn't drive as much engagement.
It is language quirk, but you can probably use LLM to replace HN headlines like this. Pretty cheap and one will no longer have visceral reaction that one does not wish.
Any talk of tide prediction should always mention xtide:
I've used it with great accuracy in a number of locations around the world.
Another one of those free software packages that's been meticulously maintained by one person for decades...
the water of an incoming tide doesn't feel "i'm being dragged uphill", it feels "hey, the earth is moving underneath me". it's all in freefall all the time.
you don't feel like you are rotating at 1000 mph (1600 kph) but you do feel your weight against the surface of the earth. same with the water, except it feels itself being squeezed by everything around it like you only feel that in the entrance to a crowded venue.
so, the water on the side toward the moon and the water on the side away from the moon would mostly perceive the earth as dropping away or coming closer (if they could perceive anything at all) where they are is always their point of reference
Title: The Most Powerful Computers You've Never Heard Of
In particular, I could understand how two satellites connected by a cable would result in the cable being stretched. But I still find it hard to wrap my mind around the fact that we get a high tide where the Earth's gravity and the Moon's add (the far side of the Earth from the Moon), but we also get a high tide on the opposite side, where the Moon's gravitational pull is subtracted from the Earth's. The centrifugal force is (I think) a much better explanation. (I realize physicists don't consider that a force, but...)
So yes, tides really are weirder than I think.
(The other facts in the article were actually familiar, e.g. the fact that the tides in Hawaii are quite small, because it's not far from an amphidromic point.)
The near part of Earth experiences more gravity from the Moon, the far part less. The Earth moves in the center so the water bulges on the ends. Important part is that the Earth pulls things out their natural orbits.
With circular orbits, gravity and centrifugal force are balanced so could be considered difference on centrifugal force. But that isn't true for all orbits.
And when they're the "most lined up" you get the "King Tide."
(92 comments)
Also https://content.teachastronomy.com/taweb/images/textbook/hrt...
Inlining my comment that I had posted there:
The problem of predicting tides was so important that it attracted many Physics and Maths heavy weights. You can well imagine how important predicting tides would have been for D-day landing. One related fascinating historical artifact is the special purpose analogue computer designed by Lord Kelvin in the 1860s based on Fourier series, harmonic analysis. Think difference engine in it's cogs and cams glory, but special purpose.
https://en.m.wikipedia.org/wiki/Tide-predicting_machine
Possibly one of the first examples of Machine learning, with Machine in capital 'M'. It incorporated recent tidal observations to update it's prediction.
Note that sinusoids are universal approximators for a large class of functions, an honour that is by no means restricted to deep neural nets.
George Darwin (Charles Darwin's son) was a significant contributor in the design and upgrade of the machine.
https://en.m.wikipedia.org/wiki/George_Darwin
Other recognizable names who worked on tide prediction problem were Thomas Young (of double slit experiment fame) and Sir George Airy (of Airy disk fame).
there are one ot two other places on the planet that are close, and from the charts in the article, spots with NO tide, which when I think about,is very wierd indeed
"Q: I live outside of the U.S. and my location is no longer supported. What happened?
A: Many data were purged after a legal threat from the U.K. Hydrographic Office (UKHO) in January 2001. I ended maintenance of the non-U.S. data that replaced them for different reasons in early 2012."
I wonder how much money the Hydrographic Office saved by not allowing this data to be distributed?
https://physics.stackexchange.com/questions/121830/does-eart...
Water -- Ground -- Water
Now let's add a Moon with gravitational pull. The pull stretches the system, because gravity is stronger the closer you are to the Moon.
Water ---- Ground ---- Water -//- Moon
The water is farther away from the ground on both sides now, since both sides stretched.
it's very magical though discovering the beauty of it.
All the rest is swept away, and you have stretches of coastline with tides over one meter, and others with nearly zero, just because of landmass distribution ...
If you moved Miami Beach to the French Atlantic coast, things would get interesting.
Why are the syzygy tidal coefficients equal when the quadrature tidal coefficients are at opposite extremes? Why are the syzygy coefficients at opposite extremes when the others are equal? Who can explain this using the laws of universal gravitation?
Her point is that you can't.
Earlier in that interview she says: I was put in touch with the Institut de Physique du Globe [2]. In April 1953, I met with Professor Coulomb [3], who was the director at the time, and asked him about the ionic variations that might occur during the lunar phases. His formal response was that there were none. However, I had already been observing them for some time. I must say that in 1953 I had already begun to observe the phenomenon of the tides. Being told that, apart from a minimum of atmospheric ionization at 4 a.m., there is nothing else that can have an impact on the biological, human, or other levels, I said: but there is the phenomenon of the tides! And that's when I got this response, which marked a break with the scientific community for me:
The phenomenon of the tides is a phenomenon that is beyond us. We waste our time when we take an interest in phenomena that are beyond us. If you don't want to waste yours, focus on other things.
Jeanne Rousseau demonstrated through observation that tidal phenomena are not solely gravitational but primarily electromagnetic. One can read more about this in English in this paper [4].
[1] https://youtu.be/ytWerrYTBLs
[2] https://en.wikipedia.org/wiki/Institut_de_Physique_du_Globe_...
[3] https://en.wikipedia.org/wiki/Jean_Coulomb
[4] https://www.researchgate.net/publication/384443419_Cosmic_Re...
The physics of tides is largely well-understood, and the moon and sun provide the primary forcing. Accurate tide tables are regularly computed the world over, with measurements regularly made. Without even looking at measurements, the shipping industry demands accurate tide forecasts for navigating efficiently. The claim that "tidal phenomena are... primarily electromagnetic" requires some serious evidence to back it up, with calculates to boot, rather than invoking mysticism that tides are "beyond us". Many things are beyond our current scientific understanding, and that is humbling, but tides are quite well understood.
I don't have the scientific knowledge to assess all this. I'm not even sure how to understand properly the questions Jeanne Rousseau asks saying newtonian physics can't answer. What I hear however are competent people observing small variation in the properties of water and living systems that seems to be related to cosmic phenomenon, including moon phases. Variations we can also find in the atmosphere/ionosphere with more recent measurements of their ionic polarities. Adding to that are all the new discoveries that link weather phenomenon to electromagnetic influences from the sun, with water significantly influencing the electromagnetic properties of the atmosphere. Finally more people question the true molecular structure of water, as H2O seems to be a crude simplification over a dynamic mixture of isotopes and ions.
Overall the tidal theory is not a done deal, we only have approximate models, and this topic can be discussed for years to come. That's probably why she was told the tides is a phenomenon that is beyond us.
It took most of this summer to get my tide clock to predict accurately, using NOAA harmonic constituents data crammed into an Arduino, a GPS module, and published formulas.
Take a look:
The truth of the matter is that the Arabic and muslim are the master of the sea during this so called "dark ages" time, and many advancement has been made from navigation gear of the Arabic astrolobe to the Idrisi map.
In tide prediction Al-Kindi for example, has notable work on tides in his seminal book Treatise on the Efficient Cause of the Flow and Ebb back in 9th CE [1],[2].
[1]al-Kindi:
https://en.wikipedia.org/wiki/Al-Kindi
[2] Al-Kindi:
