Another physics question.

[Mike Sales]

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?

[simonineaston]

I won't be able to see it as my seat in the pub does not face the water...

[Jdsk]

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?

Thanks. Never seen that before.

Is it all in one tidal system... and is there any slack in the anchor line and can you pay it out?

Jonathan

[Mike Sales]

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?

Thanks. Never seen that before.

Is it all in one tidal system... and is there any slack in the anchor line and can you pay it out?

Jonathan

Both in the same tidal system tidal system, and the boat is assumed to be in exactly the same spot.

[Psamathe]

The trouble with tidal systems is that tidal range can be very variable over such a range. So the boat might easily experience a larger tidal range than the water e.g. mid way between the boat and lighthouse.

Ian

[Jdsk]

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?

Thanks. Never seen that before.

Is it all in one tidal system... and is there any slack in the anchor line and can you pay it out?

Both in the same tidal system tidal system, and the boat is assumed to be in exactly the same spot.

Thanks, and not limited in vertical movement by the anchor?

Jonathan

[Jdsk]

The trouble with tidal systems is that tidal range can be very variable over such a range. So the boat might easily experience a larger tidal range than the water e.g. mid way between the boat and lighthouse.

I didn't know the correct term for the surface all of the relevant water going up together...

Jonathan

[Mike Sales]

The trouble with tidal systems is that tidal range can be very variable over such a range. So the boat might easily experience a larger tidal range than the water e.g. mid way between the boat and lighthouse.

Ian

For the purposes of the question you can assume that the sea over the whole area is rising and falling by the same amount at the same time.

[Mike Sales]

Thanks. Never seen that before.

Is it all in one tidal system... and is there any slack in the anchor line and can you pay it out?

Both in the same tidal system tidal system, and the boat is assumed to be in exactly the same spot.

Thanks, and not limited in vertical movement by the anchor?

Jonathan

No limit in vertical movement.

[bikes4two]

Hmmm,
> this is not an 'educated' answer by any means, but I'd guess the view of the lighthouse lantern would disappear, or be reduced
> my thinking is that yes, the anchored boat would gain height as the tide rose, but the mass of the water between the boat and lantern would also rise.
< However, the lighthouse being 'attached' to terra firma wouldn't change height, thus my answer

[Mike Sales]

Hmmm,
> this is not an 'educated' answer by any means, but I'd guess the view of the lighthouse lantern would disappear, or be reduced
> my thinking is that yes, the anchored boat would gain height as the tide rose, but the mass of the water between the boat and lantern would also rise.
< However, the lighthouse being 'attached' to terra firma wouldn't change height, thus my answer

Correct, well thought and put.
A nautical almanac has "dipping tables".
These tabulate the distance to the horizon for various heights of eye, and for various heights of the light, or whatever.


http://www.sailtrain.co.uk/navigation/rising.htm
http://skysailtraining.co.uk/dipping_distance.htm

[Stevek76]

More of a geometry question to be fair

However, the lighthouse being 'attached' to terra firma wouldn't change height, thus my answer

Even if it was a lightboat and could rise in the same manner as the observer they would still lower in the horizon relative to each other.

Obviously assuming no sudden appearance of light distorting atmospheric effects.

[Mike Sales]

More of a geometry question to be fair

However, the lighthouse being 'attached' to terra firma wouldn't change height, thus my answer

Even if it was a lightboat and could rise in the same manner as the observer they would still lower in the horizon relative to each other.

Obviously assuming no sudden appearance of light distorting atmospheric effects.

The light on a lightship or buoy would remain at the same height above the sea, so its horizon would remain the same, just as the observer's would.

[Stevek76]

Yes, but the sphere they're sat on is expanding so they are getting further apart, assuming they are both rising vertically from their own perspectives, i.e. constant lat/long

[Mike Sales]

Yes, but the sphere they're sat on is expanding so they are getting further apart, assuming they are both rising vertically from their own perspectives, i.e. constant lat/long

I did consider that factor, but my feeling, with no calculation, is that the effect would be relatively infinitesimal.