Does Earth have two high-tide bulges on opposite sides? (2014) • Hacker News Board

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#51

Post by trillic » Fri, May 23, 2025, 3:57 AM UTC

CGMthrowaway wrote: post #13

srean wrote: post #6

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 speci…

Have you seen the SF bay model? https://www.youtube.com/watch?v=i70wkxmumAw

Check out current lab

Hyperlocal ocean modeling for science, defense, and recreational applications.

https://www.current-lab.com

Anecdotally works very well in Tidal harbors with multiple rivers.

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#52

Post by TomK32 » Fri, May 23, 2025, 5:24 AM UTC

srean wrote: post #6

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 speci…

The Battle of Clontarf on April 23rd 1014 springs to mind. While the high tide was of favour for the invading Vikings (who had already founded and still ruled Dublin) at 5:30 in the morn, the battle lasted all day and the next high tide at 17:55 cut off their way to a nearby wood and many killed or drowned as their were pushed against the tide. The times were calculated in 1860 by Samuel Haughton.

There is of course an In Our Time episode https://www.bbc.co.uk/programmes/m0029qh3

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#53

Post by ahazred8ta » Fri, May 23, 2025, 5:26 AM UTC

parpfish wrote: post #21

srean wrote: post #12

Earlier quoted context omitted.

His childhood was quite emotionally traumatic. I can imagine severe abandonment wounds given his situation. Not only would he have felt abandoned, when his mother quickly remarried after his father's death, he could actually see the distant steeple where her mother had to relocate after her marriage - source of affection and emotional connect just tantalizingly out of reach. That might explain his behaviour.

And to top it all off, that dang apple hit him on the head

Newton - "the sole mortal who could grapple, Since Adam, with a fall or with an apple." — Byron

A calculus fit to compute on, White light and a head to drop fruit on, A mind to absorb it, And soar into orbit — That's all that it takes to be Newton. — Gina Berkeley

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#54

Post by School-Cotton » Fri, May 23, 2025, 5:39 AM UTC

an0malous wrote: post #30

School-Cotton wrote: post #9

So, yet another thing I learned at school was bullshit. Pretty interesting to know!

What are the others? The Bernoulli principle is one.

“Serious companies will require you to comment every line of code”

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#55

Post by TomK32 » Fri, May 23, 2025, 5:45 AM UTC

dghlsakjg wrote: post #48

CommenterPerson wrote: post #44

Six months ago, I spent a week at the shore. It happened to be full moon. We were out walking late at night while the moon was high up, and had to slog through ankle deep water on the way back. It was like clockwork roughly 12 hours apart. Did read through stackexchange. It is indeed complicated. But the top response feels like paralysis by analysis. If we analyzed turbulent flow too much we would be unable to build…

Your clock was off. Tides advance ~30 minutes per day. But not exactly 30 minutes. Sometimes more. Sometimes less. Sometimes it doesn’t follow a semi diurnal pattern. Water can’t pass through landmasses, and that is a huge factor. If the earth had no landmasses, the tides would be entirely as you expect. However, if you look at a global visualization of tidal heights, you will see that a small landmass, NZ is a great…

And then there's the Solent which for Springs has a double high tide as the western end of the Solent is quite narrow and the tide racing around the Isle of White and in from the wider eastern side. https://www.nci.org.uk/solent-tides/

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#56

Post by kgwgk » Fri, May 23, 2025, 5:46 AM UTC

dghlsakjg wrote: post #48

CommenterPerson wrote: post #44

Six months ago, I spent a week at the shore. It happened to be full moon. We were out walking late at night while the moon was high up, and had to slog through ankle deep water on the way back. It was like clockwork roughly 12 hours apart. Did read through stackexchange. It is indeed complicated. But the top response feels like paralysis by analysis. If we analyzed turbulent flow too much we would be unable to build…

Your clock was off. Tides advance ~30 minutes per day. But not exactly 30 minutes. Sometimes more. Sometimes less. Sometimes it doesn’t follow a semi diurnal pattern. Water can’t pass through landmasses, and that is a huge factor. If the earth had no landmasses, the tides would be entirely as you expect. However, if you look at a global visualization of tidal heights, you will see that a small landmass, NZ is a great…

> Your clock was off. Tides advance ~30 minutes per day.

“roughly 12 hours”

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#57

Post by Sharlin » Fri, May 23, 2025, 6:14 AM UTC

antognini wrote: post #17

When I was in grad school in astronomy, one of my professors told me "many a promising young researcher has run their career aground on the rocky shores of tides." The mathematics involved in the theory of tides are formidable. Even in homogeneous, tidally locked systems things can get complicated very quickly. But tides are nevertheless very important. One two objects pass very close to each other, tidal effects are…

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#58

Post by dexwiz » Fri, May 23, 2025, 7:07 AM UTC

darkerside wrote: post #46

II2II wrote: post #38

Earlier quoted context omitted.

That would be akin to describing a computer as a complicated arrangement of switches that control each other through pulses of electricity to do useful stuff. While it may satisfy a bunch of people who aren't really interested in how computers work, and it may even inspire a few people who are intrigued by how such a simple notion could produce incredible results, it doesn't really explain how computers work.

But it is actually a bit more accurate than saying, electricity goes in and information comes out

Information and electricity go in and information and heat go out, to be pedantic about a simplification.

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#59

Post by grues-dinner » Fri, May 23, 2025, 8:24 AM UTC

rhdjsjebshjffn wrote: post #50

srean wrote: post #6

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 speci…

> You can well imagine how important predicting tides would have been for D-day landing. Is this intended to communicate positivity or negativity? Predicting tides was known to the ancients; it would be lovely to explore the hubris of the modern narrative. Edit: fundamentally, if hacker news has taught me anything, it's that "downvote = makes me feel bad and doesn't want to answer questions". The entire concept of de…

I think there are two ways to interpret that sentence: "it would have been important": one which implies tidal prediction was unavailable at D-day but would have been useful, and one that implies it was indeed available (subjunctive conditional or "the Anderson case", apparently, per Wikipedia)

I don't think anyone is claiming tide times were so unpredictable in 1945.

Re: Does Earth have two high-tide bulges on opposite sides? (2014)

#60

Post by krisoft » Fri, May 23, 2025, 8:43 AM UTC

rhdjsjebshjffn wrote: post #50

srean wrote: post #6

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 speci…

> You can well imagine how important predicting tides would have been for D-day landing. Is this intended to communicate positivity or negativity? Predicting tides was known to the ancients; it would be lovely to explore the hubris of the modern narrative. Edit: fundamentally, if hacker news has taught me anything, it's that "downvote = makes me feel bad and doesn't want to answer questions". The entire concept of de…

> Is this intended to communicate positivity or negativity?

It just says it was important to predict the tides. There is no positivity or negativity to it. Your question doesn’t make sense, hence the downvotes.

> Predicting tides was known to the ancients

Good. To which ancients? With what accuracy and how far into the future? What techniques did they use? Tell us more.

> it would be lovely to explore the hubris of the modern narrative.

Explore it then! Would love to read it. It is not like there is some conspiracy holding you back.