Things you always wanted to know the answer to [Vol. 2]
Discussion
NoNeed said:
Why do we have seagulls in Birmingham?
There's no such bird as a seagull. There's common gulls, Pacific gulls etc. They are commonly called seagulls as traditionally they are sea birds.But like any animal, they adapt their behaviour to the changing environment. If Birmingham has richer pickings than the coast, that's where they'll go.
Willy Nilly said:
Silent1 said:
rubbish dumps mainly, they're a nightmare when ploughing as well as it's not uncommon to have a hundred or more flying around the tractor.
Put a dead one on your roof, they'll leave you alone then 
I'm a keen swimmer. When I was a kid, I wore goggles. These gave me clear vision under water and had no effect on my vision out of the water. As I've got older, my eyesight has got worse. I'm now shortsighted, so I have prescription goggles, -3 on each eye. These give me perfect vision out of the water, same as my glasses, but underwater, everything is blurred. If I wear non prescription goggles, my vision underwater isn't perfect like when I was a kid, but far better than with prescription goggles. Why?
Dr Jekyll said:
Is it my imagination or are cement mixer trucks much rarer than they used to be? I saw one on Friday and it occurred to me I don't remember seeing one for years.
Fewer trucks because there are fewer reinforced concrete construction projects such as motorway bridges, multistorey car parks etc.TwigtheWonderkid said:
I'm a keen swimmer. When I was a kid, I wore goggles. These gave me clear vision under water and had no effect on my vision out of the water. As I've got older, my eyesight has got worse. I'm now shortsighted, so I have prescription goggles, -3 on each eye. These give me perfect vision out of the water, same as my glasses, but underwater, everything is blurred. If I wear non prescription goggles, my vision underwater isn't perfect like when I was a kid, but far better than with prescription goggles. Why?
different refractive index underwaterATTAK Z said:
Dr Jekyll said:
Is it my imagination or are cement mixer trucks much rarer than they used to be? I saw one on Friday and it occurred to me I don't remember seeing one for years.
Fewer trucks because there are fewer reinforced concrete construction projects such as motorway bridges, multistorey car parks etc.TwigtheWonderkid said:
I'm a keen swimmer. When I was a kid, I wore goggles. These gave me clear vision under water and had no effect on my vision out of the water. As I've got older, my eyesight has got worse. I'm now shortsighted, so I have prescription goggles, -3 on each eye. These give me perfect vision out of the water, same as my glasses, but underwater, everything is blurred. If I wear non prescription goggles, my vision underwater isn't perfect like when I was a kid, but far better than with prescription goggles. Why?
I've no idea but thanks for reminding me of Billy Connolly's prescription windscreen story.http://www.youtube.com/watch?v=pwFcGXpMmYw
Dr Jekyll said:
Andy why do goggles (or masks) allow clearer vision underwater than if your eyes get wet? (I know it's to do with refraction, but specifically.)
You have spent all your life interpreting light as refracted by the eyeball:air interface. Under water that doesn't happen. Fish out of water would have the opposite problem. Amongst others.grumbledoak said:
You have spent all your life interpreting light as refracted by the eyeball:air interface. Under water that doesn't happen. Fish out of water would have the opposite problem. Amongst others.
Perhaps that's how life on land got started. Some fish struggled out of the sea and couldn't see to find their way back. Just as well of course, otherwise evolution would have taken a different turn and we'd all be living in the sea now and struggling to use PH without water getting into our laptops.ATTAK Z said:
TwigtheWonderkid said:
I'm a keen swimmer. When I was a kid, I wore goggles. These gave me clear vision under water and had no effect on my vision out of the water. As I've got older, my eyesight has got worse. I'm now shortsighted, so I have prescription goggles, -3 on each eye. These give me perfect vision out of the water, same as my glasses, but underwater, everything is blurred. If I wear non prescription goggles, my vision underwater isn't perfect like when I was a kid, but far better than with prescription goggles. Why?
different refractive index underwaterI would think that the different refractive index of water means that the light isn't focused accurately onto the retina.
Perhaps the prescription goggles need to be your prescription but adjusted to take account of this.
Maybe standard goggles apply some correction but insufficient but the effect is that the images are focused nearer to accurately on the retina than the prescription.
Please note this is a speculative answer hence the maybe and perhaps.
Interested to know the answer. Question is there a difference between duration under water?
Perhaps the prescription goggles need to be your prescription but adjusted to take account of this.
Maybe standard goggles apply some correction but insufficient but the effect is that the images are focused nearer to accurately on the retina than the prescription.
Please note this is a speculative answer hence the maybe and perhaps.
Interested to know the answer. Question is there a difference between duration under water?
Wonders of google this link suggests they need to be different.
http://www.drrajod.com/eyeglasses-and-contacts/spe...
http://www.drrajod.com/eyeglasses-and-contacts/spe...
TwigtheWonderkid said:
NoNeed said:
Why do we have seagulls in Birmingham?
There's no such bird as a seagull. There's common gulls, Pacific gulls etc. They are commonly called seagulls as traditionally they are sea birds.But like any animal, they adapt their behaviour to the changing environment. If Birmingham has richer pickings than the coast, that's where they'll go.
Seagulls are the blight of coastal councils when it comes to rubbish bags. One council (Hastings IIRC) tried a novel solution. Many of the houses in part of the town didn't have room for a wheeled or tub bin so had to but black sacks out for their rubbish, recycling going in pick sacks. The minute they went out, the gulls would tear them open but leave the pink recycling sacks alone.
Someone had the idea of swapping the bags around so rubbish went in the pink bag and recycling in the black one. After a few weeks, the gulls realised that there was nothing eat in the black bags and knew that there was nothing in the pick ones either and this the problem was solved.
FiF said:
Wonders of google this link suggests they need to be different.
http://www.drrajod.com/eyeglasses-and-contacts/spe...
That's really strange. If you don't need glasses on land you don't need them underwater, but if you do need them on land you need different ones underwater.http://www.drrajod.com/eyeglasses-and-contacts/spe...
Dr Jekyll said:
That's really strange. If you don't need glasses on land you don't need them underwater, but if you do need them on land you need different ones underwater.
It's because they are trying to flog you custom goggles/masks - the lenses in these are further from your eye than your glasses' lenses. You can try it by holding your glasses/binoculars/telescope three inches in front of you.It's cheaper to wear contacts and ordinary goggles/masks.
grumbledoak said:
It's cheaper to wear contacts and ordinary goggles/masks.
...and better when you get out of the water as you can still see when you take your mask off. I used to have a prescription diving mask, it was a right pain having to keep it on to see properly when not underwater. Nowadays I use daily disposable contacts and a plain mask with some spare contacts with me in case the ones I have float off which they never have so far.Gassing Station | The Lounge | Top of Page | What's New | My Stuff