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Super seers
The back pages Almost the last word Since its force gives energy to falling rocks, why doesn’t gravity diminish over time?
In the ink
Guy Cox Sydney, New South Wales, Australia There are two reasons for this. One is that our eyes are much less sensitive to blue light – peak sensitivity is in the yellow-green region of the spectrum, so if all markers were of equal intensity, the yellow and green ones would always seem brighter to us. Sensitivity falls in the red region, too, so red markers can never match the brightness of yellows and greens either. The second reason is inherent in the way these markers work. They seem so bright because they contain fluorescent dyes that absorb short-wavelength light and re-emit it at their specific colour. Blue is at the short end of the visible spectrum, so a blue fluorescent pigment can only be excited by ultraviolet light, which is usually in short supply indoors. Yellow-green dyes can be excited by blue light and UV, so they are excited more efficiently. Red-emitting dyes can be excited by green light as well and this helps to compensate for the eye’s lower sensitivity to their colour. Eric Kvaalen Les Essarts-le-Roi, France Our eyes are more sensitive to light in the middle of the spectrum, which means orange, yellow and green. For longer wavelengths (red) or shorter wavelengths (blue), the sensitivity drops off, falling to zero for infrared and ultraviolet. Pink is a mixture of red and white, which makes it more luminous than just red. One can also make a mixture of blue and white, which will also be fairly luminous. Some languages, such as Russian and Hebrew, have a different word for this blue/white mixture, just as we have different words for pink and red. 54 | New Scientist | 19 October 2019
IMAGEBROKER/ALAMY STOCK PHOTO
Why do blue highlighter markers never seem to have the high luminosity of pink, yellow, orange and light green highlighters?
This week’s new questions Shrinking gravity The first law of thermodynamics is the conservation of energy. The first law of geology is that rocks fall downhill. Falling rocks gain energy. The energy must come from gravity. So why doesn’t gravity get less every day? Anthony Woodward, Portland, Oregon, US Super seers I have heard that it is possible for some people to see ultraviolet light. Is this true, and if so, how is it possible? Kevin Burton, Buenos Aires, Argentina
Good consumers Which is better for the environment, online shopping or traditional high street shopping?
Brian Horton West Launceston, Tasmania, Australia In terms of packaging and shipping, it is more efficient for a shop to bring large quantities of goods from a factory or depot to your local area than for everyone to buy those goods online and have them delivered individually to their homes from the factory or the depot. Therefore, if the items you want are readily available from local shops, then in environmental terms, it is better to buy them locally. For anything else, buying online would be more efficient. We can probably ignore the environmental cost of driving to the shops to buy goods, since this is roughly equivalent to the cost of the final stage of delivery to your house when you buy online.
Simon Dales Oxford, UK I would say the best options are to drive to an out-of-town store to do your weekly grocery shop, ideally when driving back from somewhere else. Then go to a local store for perishables. And for most of the rest, walk, cycle or use public transport. Hillary Shaw Newport, Shropshire, UK There are factors other than emissions used in transporting goods to consider. Online searches themselves use energy. Car owners who shop online may drive elsewhere in the time freed up from shopping. But trip-linking may mean going to the shops is done in conjunction with, say, work journeys, and then there is no gain by going online.
With set delivery slots, a vehicle bringing goods ordered online may not take the shortest route, and with frequent stop-starting its fuel use may be higher than that of consumers driving to a shop. The distance from factory to online delivery depot may also be long. Socially, traditional high street shopping wins hands down: you retain more employment, meet more people, keep town centres viable and enjoy experiences outside the home. If only the roads weren’t so clogged and the parking so expensive. Ali El Idrissi San Francisco, California, US Rather than just choose between online or high street shopping, society needs to transition to sustainable consumption and organise new ways to provide everyday products and services. The consumerist culture associated with shopping – both on- and offline – has huge negative impacts on our health and our environment. Humanity currently uses resources each year equal to those of 1.7 planets. If nothing changes, this will be two planets by 2030. A study in the Journal of Industrial Ecology calculated that, in 2007, household consumption, including shopping, contributed to more than 60 per cent of carbon emissions. This is unsustainable. There is nothing wrong with consumption per se. It is part of our lives, reflects our journey and carries our memories. The problem is the excess that happens when consumption itself becomes the goal. ❚ For more on this subject, see “The last-mile revolution”, New Scientist, 7 September, p 42 – Ed
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
In the ink
Guy Cox Sydney, New South Wales, Australia There are two reasons for this. One is that our eyes are much less sensitive to blue light – peak sensitivity is in the yellow-green region of the spectrum, so if all markers were of equal intensity, the yellow and green ones would always seem brighter to us. Sensitivity falls in the red region, too, so red markers can never match the brightness of yellows and greens either. The second reason is inherent in the way these markers work. They seem so bright because they contain fluorescent dyes that absorb short-wavelength light and re-emit it at their specific colour. Blue is at the short end of the visible spectrum, so a blue fluorescent pigment can only be excited by ultraviolet light, which is usually in short supply indoors. Yellow-green dyes can be excited by blue light and UV, so they are excited more efficiently. Red-emitting dyes can be excited by green light as well and this helps to compensate for the eye’s lower sensitivity to their colour. Eric Kvaalen Les Essarts-le-Roi, France Our eyes are more sensitive to light in the middle of the spectrum, which means orange, yellow and green. For longer wavelengths (red) or shorter wavelengths (blue), the sensitivity drops off, falling to zero for infrared and ultraviolet. Pink is a mixture of red and white, which makes it more luminous than just red. One can also make a mixture of blue and white, which will also be fairly luminous. Some languages, such as Russian and Hebrew, have a different word for this blue/white mixture, just as we have different words for pink and red. 54 | New Scientist | 19 October 2019
IMAGEBROKER/ALAMY STOCK PHOTO
Why do blue highlighter markers never seem to have the high luminosity of pink, yellow, orange and light green highlighters?
This week’s new questions Shrinking gravity The first law of thermodynamics is the conservation of energy. The first law of geology is that rocks fall downhill. Falling rocks gain energy. The energy must come from gravity. So why doesn’t gravity get less every day? Anthony Woodward, Portland, Oregon, US Super seers I have heard that it is possible for some people to see ultraviolet light. Is this true, and if so, how is it possible? Kevin Burton, Buenos Aires, Argentina
Good consumers Which is better for the environment, online shopping or traditional high street shopping?
Brian Horton West Launceston, Tasmania, Australia In terms of packaging and shipping, it is more efficient for a shop to bring large quantities of goods from a factory or depot to your local area than for everyone to buy those goods online and have them delivered individually to their homes from the factory or the depot. Therefore, if the items you want are readily available from local shops, then in environmental terms, it is better to buy them locally. For anything else, buying online would be more efficient. We can probably ignore the environmental cost of driving to the shops to buy goods, since this is roughly equivalent to the cost of the final stage of delivery to your house when you buy online.
Simon Dales Oxford, UK I would say the best options are to drive to an out-of-town store to do your weekly grocery shop, ideally when driving back from somewhere else. Then go to a local store for perishables. And for most of the rest, walk, cycle or use public transport. Hillary Shaw Newport, Shropshire, UK There are factors other than emissions used in transporting goods to consider. Online searches themselves use energy. Car owners who shop online may drive elsewhere in the time freed up from shopping. But trip-linking may mean going to the shops is done in conjunction with, say, work journeys, and then there is no gain by going online.
With set delivery slots, a vehicle bringing goods ordered online may not take the shortest route, and with frequent stop-starting its fuel use may be higher than that of consumers driving to a shop. The distance from factory to online delivery depot may also be long. Socially, traditional high street shopping wins hands down: you retain more employment, meet more people, keep town centres viable and enjoy experiences outside the home. If only the roads weren’t so clogged and the parking so expensive. Ali El Idrissi San Francisco, California, US Rather than just choose between online or high street shopping, society needs to transition to sustainable consumption and organise new ways to provide everyday products and services. The consumerist culture associated with shopping – both on- and offline – has huge negative impacts on our health and our environment. Humanity currently uses resources each year equal to those of 1.7 planets. If nothing changes, this will be two planets by 2030. A study in the Journal of Industrial Ecology calculated that, in 2007, household consumption, including shopping, contributed to more than 60 per cent of carbon emissions. This is unsustainable. There is nothing wrong with consumption per se. It is part of our lives, reflects our journey and carries our memories. The problem is the excess that happens when consumption itself becomes the goal. ❚ For more on this subject, see “The last-mile revolution”, New Scientist, 7 September, p 42 – Ed
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