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We are but dust
The back pages Almost the last word How far through the galaxy can one person travel during their life?
Heated windshield It is a windy -20°C outside and I just saw a flock of ducks fly over. How do the birds stop their eyeballs freezing?
Richard Lucas Camberley, Surrey, UK There are a number of features that combine to protect the eyes of ducks – and most other animals – from freezing. The eyes themselves and the tears that cover them are quite salty and so won’t freeze until the temperature drops quite a long way. In addition, the eyes are mostly surrounded by nice warm flesh as well as bone with its good blood supply, both of which serve to maintain their temperature. And in many animals, ducks included, the eyes have a third eyelid, or nictitating membrane, that has its own blood supply and a gland that secretes tears high in lipids that confer extra protection. Mike Follows Sutton Coldfield, West Midlands, UK Birds’ eyes are recessed into their warm heads. And in cold surroundings, the body diverts blood to the brain and other vital organs. Besides, a flying bird will generate a lot of heat during flight. The fluid inside birds’ and other animals’ eyes, the aqueous and vitreous humours, provides a fair amount of heat capacity, so that it will tend to match the core body temperature. The corneal tissue at the front of the eye has high thermal conductivity so it doesn’t stray too far from body temperature even when the ambient temperature is extreme. For example, if the environment is at -11°C, the surface temperature of a human cornea only falls to 28.6°C. Birds flying in a group take it in 54 | New Scientist | 22 June 2019
CAVAN IMAGES/PLAINPICTURE
The Royal Society for the Protection of Birds, via Twitter Blood vessels provide the eyes with a continuous supply of blood, which ensures constant warmth and prevents them from freezing.
This week’s new questions Galactic traveller My wife told me I should get out more. I replied that I am just about to celebrate my 66th free trip around the sun. Can anyone tell me how far I have travelled in our galaxy during that time? Stephen Dowsett, London, UK Lucky dip Which gives me better odds of winning the lottery: buying one ticket a week or 52 tickets once a year? John Clark, Leeds, UK
turns to go at the front and, when they are slipstreaming, probably experience a reduced headwind and smaller windchill as a result. They will also blink to ensure their eyes don’t dry out, ensuring they stay covered in a film of salty fluid that acts like antifreeze. There is an example of human eyes failing to freeze in windy and extremely cold surroundings. On 10 June 1990, a window on the flight deck of a BAC-111 aircraft failed and the sudden decompression pulled the captain head first through the breach. A quick-thinking flight attendant, Nigel Ogden, grabbed his legs and saved his life. Ogden ended up with a frostbitten cornea, but his eyes didn’t freeze, although it would have been extremely cold. Tim Coxsen Glenden, Queensland, Australia They adopt the “safety squint” technique. Like when you use an angle grinder without eye protection…
We are but dust What is dust? What is it made of, and is it bad for human health?
Dee Dhamija London, UK Dust includes tiny particles of debris and dead skin. Its small size means it can be inhaled and potentially evoke an immune reaction. Such allergic reactions may be minor or major depending on the individual. Dust can also serve as a “fomite”, potentially carrying viruses and possibly passing on infections. Charles Harrison Health and safety adviser Willand, Devon, UK Household dust is mostly made up of human skin, microscopic
creatures and dead bugs. This may make your skin crawl, but doesn’t offer significant health risks for most people. However, other forms of dust can be very harmful indeed. Last year, tiny particles of sand, wood and asbestos contributed to 12,000 deaths from lung disease in the UK, according to the Health and Safety Executive. Many more deaths will have been caused by exposure outside the workplace, including to particulates produced by cars. Repeated, long-term exposure to high levels of dust of any form can harm your health. Normal household exposure will probably not cause you any problems, but working in a dusty environment may well do so. Excellent advice is available from the Health and Safety Executive or the US Occupational Safety and Health Administration. If dust in the air reaches a highenough level, it can also cause explosions – which are certainly harmful to health! Eva Kumar National Institute for Health and Welfare, Kuopio, Finland In a recent study I was involved in, we looked at levels of brominated and phosphorous flame retardants in dust in children’s bedrooms in Finland (Chemosphere, doi.org/c68h). We found several flame retardants, which are added to household and consumer products, but not at levels considered to be damaging to health. We also discovered that, in indoor environments, dust is a major contributor to human exposure to these flame retardants. ❚
Want to send us a question or answer?
Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms
Heated windshield It is a windy -20°C outside and I just saw a flock of ducks fly over. How do the birds stop their eyeballs freezing?
Richard Lucas Camberley, Surrey, UK There are a number of features that combine to protect the eyes of ducks – and most other animals – from freezing. The eyes themselves and the tears that cover them are quite salty and so won’t freeze until the temperature drops quite a long way. In addition, the eyes are mostly surrounded by nice warm flesh as well as bone with its good blood supply, both of which serve to maintain their temperature. And in many animals, ducks included, the eyes have a third eyelid, or nictitating membrane, that has its own blood supply and a gland that secretes tears high in lipids that confer extra protection. Mike Follows Sutton Coldfield, West Midlands, UK Birds’ eyes are recessed into their warm heads. And in cold surroundings, the body diverts blood to the brain and other vital organs. Besides, a flying bird will generate a lot of heat during flight. The fluid inside birds’ and other animals’ eyes, the aqueous and vitreous humours, provides a fair amount of heat capacity, so that it will tend to match the core body temperature. The corneal tissue at the front of the eye has high thermal conductivity so it doesn’t stray too far from body temperature even when the ambient temperature is extreme. For example, if the environment is at -11°C, the surface temperature of a human cornea only falls to 28.6°C. Birds flying in a group take it in 54 | New Scientist | 22 June 2019
CAVAN IMAGES/PLAINPICTURE
The Royal Society for the Protection of Birds, via Twitter Blood vessels provide the eyes with a continuous supply of blood, which ensures constant warmth and prevents them from freezing.
This week’s new questions Galactic traveller My wife told me I should get out more. I replied that I am just about to celebrate my 66th free trip around the sun. Can anyone tell me how far I have travelled in our galaxy during that time? Stephen Dowsett, London, UK Lucky dip Which gives me better odds of winning the lottery: buying one ticket a week or 52 tickets once a year? John Clark, Leeds, UK
turns to go at the front and, when they are slipstreaming, probably experience a reduced headwind and smaller windchill as a result. They will also blink to ensure their eyes don’t dry out, ensuring they stay covered in a film of salty fluid that acts like antifreeze. There is an example of human eyes failing to freeze in windy and extremely cold surroundings. On 10 June 1990, a window on the flight deck of a BAC-111 aircraft failed and the sudden decompression pulled the captain head first through the breach. A quick-thinking flight attendant, Nigel Ogden, grabbed his legs and saved his life. Ogden ended up with a frostbitten cornea, but his eyes didn’t freeze, although it would have been extremely cold. Tim Coxsen Glenden, Queensland, Australia They adopt the “safety squint” technique. Like when you use an angle grinder without eye protection…
We are but dust What is dust? What is it made of, and is it bad for human health?
Dee Dhamija London, UK Dust includes tiny particles of debris and dead skin. Its small size means it can be inhaled and potentially evoke an immune reaction. Such allergic reactions may be minor or major depending on the individual. Dust can also serve as a “fomite”, potentially carrying viruses and possibly passing on infections. Charles Harrison Health and safety adviser Willand, Devon, UK Household dust is mostly made up of human skin, microscopic
creatures and dead bugs. This may make your skin crawl, but doesn’t offer significant health risks for most people. However, other forms of dust can be very harmful indeed. Last year, tiny particles of sand, wood and asbestos contributed to 12,000 deaths from lung disease in the UK, according to the Health and Safety Executive. Many more deaths will have been caused by exposure outside the workplace, including to particulates produced by cars. Repeated, long-term exposure to high levels of dust of any form can harm your health. Normal household exposure will probably not cause you any problems, but working in a dusty environment may well do so. Excellent advice is available from the Health and Safety Executive or the US Occupational Safety and Health Administration. If dust in the air reaches a highenough level, it can also cause explosions – which are certainly harmful to health! Eva Kumar National Institute for Health and Welfare, Kuopio, Finland In a recent study I was involved in, we looked at levels of brominated and phosphorous flame retardants in dust in children’s bedrooms in Finland (Chemosphere, doi.org/c68h). We found several flame retardants, which are added to household and consumer products, but not at levels considered to be damaging to health. We also discovered that, in indoor environments, dust is a major contributor to human exposure to these flame retardants. ❚
Want to send us a question or answer?
Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms