Floating Ship Mirage

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tenchboy
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Floating Ship Mirage

Post by tenchboy » Fri Mar 05, 2021 12:56 pm

This from the BBC but no doubt available elsewhere.
I'm quite happy with the light-bending seeming to displace objects - it happens all the time; but why the floaty effect? Why are the lightwaves from the sea surrounding the ship not also bent and why are they not producing a 'halo' of sea around the ship?
Any ideas?

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Re: Floating Ship Mirage

Post by jaap » Fri Mar 05, 2021 1:21 pm

As far as I understand it, it is the other way around. The ship is actually approximately in the spot where you see it - it is just that the sea around it has a thin layer of cold air causing it to "reflect" the sky. So it is the light coming from the sea that is bent, not the light coming from the ship. The real horizon is actually much higher up than where you see it.

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Re: Floating Ship Mirage

Post by lpm » Fri Mar 05, 2021 1:42 pm

The sh.t BBC says it's a superior mirage, but this says it's actually an Inferior Mirage. It shows the way the light rays go, which is as Jaap describes.

https://www.animations.physics.unsw.edu ... olours.htm
What ever happened to that Trump guy, you know, the one who was president for a bit?

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Re: Floating Ship Mirage

Post by jaap » Fri Mar 05, 2021 2:12 pm

So it is actually a layer of warm air that is reflecting the sky. No doubt there is a very cold layer of air which is warmed on the underside by the sea, and it is that gradient that is making the sea disappear.
There might be a gradient above the cold air layer as well, so it is certainly possible that there is also a superior mirage happening to some extent, making the ship appear higher than it is, but the floating effect is not (just) that.

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Re: Floating Ship Mirage

Post by tenchboy » Fri Mar 05, 2021 4:00 pm

Ching! Yes it's an horizon shift! The ship is normal size for its position and being seen normally. Mirages act on stuff far away, like horizons and oases; the ship is too close to be shifted; if the ship was far away and being shifted it would be much smaller.
The light that would normally go up and over our heads from the distant horizon has gone up but come down again to our eye and so we see it in a higher position.
EPLS!
Thanks all.

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shpalman
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Re: Floating Ship Mirage

Post by shpalman » Fri Mar 05, 2021 4:13 pm

tenchboy wrote:
Fri Mar 05, 2021 4:00 pm
Ching! Yes it's an horizon shift! The ship is normal size for its position and being seen normally. Mirages act on stuff far away, like horizons and oases; the ship is too close to be shifted; if the ship was far away and being shifted it would be much smaller.
The light that would normally go up and over our heads from the distant horizon has gone up but come down again to our eye and so we see it in a higher position.
EPLS!
Thanks all.
Not that the light from the sky which would normally end up in the sea has been bent upwards* so that we see it as if it came from where the sea is?

* - by light travelling faster in the "warmer" air next to the sea, which isn't as cold as the air.
molto tricky

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Re: Floating Ship Mirage

Post by tenchboy » Fri Mar 05, 2021 5:29 pm

shpalman wrote:
Fri Mar 05, 2021 4:13 pm
tenchboy wrote:
Fri Mar 05, 2021 4:00 pm
Ching! Yes it's an horizon shift! The ship is normal size for its position and being seen normally. Mirages act on stuff far away, like horizons and oases; the ship is too close to be shifted; if the ship was far away and being shifted it would be much smaller.
The light that would normally go up and over our heads from the distant horizon has gone up but come down again to our eye and so we see it in a higher position.
EPLS!
Thanks all.
Not that the light from the sky which would normally end up in the sea has been bent upwards* so that we see it as if it came from where the sea is?

* - by light travelling faster in the "warmer" air next to the sea, which isn't as cold as the air.
Nice. Ta. I was just thinking as I was driving home, no, inverted. so down and bending up rather than up and bending down. Thanks for the correction shps.

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