Another physics question.

[rjb]

It's all getting a bit foggy and the foghorns are now sounding. Time to pull the duvet over my head.

[Stevek76]

I mean strictly speaking they're not on an expanding sphere but a rotating, morphing ovoid of sorts. The radius will be a little lower at high tide because they're on a pointier bit which means the horizon will also be a little shorter as a result.

Also likely very small

[Mike Sales]

I mean strictly speaking they're not on an expanding sphere but a rotating, morphing ovoid of sorts. The radius will be a little lower at high tide because they're on a pointier bit which means the horizon will also be a little shorter as a result.

Also likely very small

A factor which had not occured to me!
In my defence I was thinking as a practical sailor who would likely be unable to detect such small differences.

[Psamathe]

If you are including "small" factors in the calculation, depending on where on the Earth's surface the lighthouse and observer are and the bearing between the two, high tide will be at a (slightly) different time for lighthouse than for observer.

Ian

[wirral_cyclist]

High tide is full sun and the lighthouse, lantern and all is lost in the glare?

[Cowsham]

High tide is full sun and the lighthouse, lantern and all is lost in the glare?

I thought it would be off for energy saving

[Cowsham]

I thought of a practical physics question that a cyclist should know the answer to.

How far do you need to fall to have an impact speed of 25 MPH (or 40 Kph) ?

ie when traveling at 25MPH on your bike if you fall off hitting the ground what height of a fall is that equivalent to?

The answer is scary. Little wonder I broke so many ribs.

[DaveBeck]

There is a small spit of land between my moored boat and St Mawes Castle in the Carrick Roads, Falmouth.

At low tide I can't see the castle, but as the tide comes in and we move further away from the seabed (whilst the castle doesn't as it is fixed relative to the seabed) the top of the castle becomes visible. It's the equivalent of the boat and I standing on a 15 foot ladder.

[Cowsham]

There is a small spit of land between my moored boat and St Mawes Castle in the Carrick Roads, Falmouth.

At low tide I can't see the castle, but as the tide comes in and we move further away from the seabed (whilst the castle doesn't as it is fixed relative to the seabed) the top of the castle becomes visible. It's the equivalent of the boat and I standing on a 15 foot ladder.

Don't fall !

[RickH]

High tide is full sun and the lighthouse, lantern and all is lost in the glare?

High tide is mostly from lunar gravity & happens roughly twice a day.

[661-Pete]

Assuming that the change in the sea surface's curvature is negligible, the geometry will stay the same. But the lighthouse, being attached to terra firma, will stand lower above the waterline. If it was only just visible at low tide, it will not be visible at high tide.

[DaveReading]

Clearly if the light was sitting just on the horizon at low tide, then when the tide came in the light would be submerged and probably go out.

[661-Pete]

You are on an anchored boat at low tide.
The lantern of a lighthouse is just visible, sitting on the horizon.
At high water, with the boat in the same place, what will happen to your view of the light?

Just occurred to me: if the boat is anchored, and the line is taut at low tide, then the boat will submerge as the tide comes in... ....and if you can't swim....

Sounds a bit like bad seamanship to me - and I'm not even a seafarer.

On the other hand, why not pose this question on one of the Flat Earth Society forums and see what they say? Good for a laugh! Another question: what causes tides on the Flat Earth.....?

[Mike Sales]

Just occurred to me: if the boat is anchored, and the line is taut at low tide, then the boat will submerge as the tide comes in... ....and if you can't swim....

Sounds a bit like bad seamanship to me - and I'm not even a seafarer.

The question of the amount of anchor cable to let out, known as scope, is one studied by boaters.
The rule of thumb is three times the depth at HW of chain, and five times the depth of rope
One saying, to encourage laying out plenty of cable, is that it is no use in the locker.
The first and easiest remedy to a dragging anchor is to let out more cable.
Looking around at the sea when out on it, it seems to me to be obvious that the sea's surface is convex.
Ships may have their upper works visible, but their hull below the horizon. When they come closer, or you climb the mast, more and more of the hull appears.

[Mick F]

Anchors are on the the end of cables, not called ropes.
Cables are generally heavy chains, and it's the gravity of the chains on the sea bottom that secure the ship.
The anchor is there to "anchor" the end of the chain and it's designed to slip and drag a bit.

Hauling it back in, the ship is pulled forwards by the capstan(s) until the cable is lifting out the anchor. The whole thing is hauled up until the anchor is seated in the bow and the ship proceeds.