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Gambler's fallacy
The back pages Almost the last word Are the odds in online gambling personalised for each competitor?
Shrinking gravity
Oliver Knott (age 12) Olney, Buckinghamshire, UK When rocks are taken uphill, they gain gravitational potential energy from whatever brought them up. When they fall down, this becomes kinetic energy, which is released as heat or used to break the rocks when they reach the bottom. The energy doesn’t come from gravity, it comes from whatever brought the rocks up. So gravity doesn’t diminish over time. Robert Willis Nanaimo, British Columbia, Canada Rocks build up potential energy, usually over eons, as the ground is pushed up by tectonic movements. This transfers some of a tectonic plate’s kinetic energy into potential energy in the now-higher rocks. At some point, probably due to erosion, they fall back down, quickly converting their potential energy back to kinetic energy. This is then transferred back to the underlying tectonic plate as the rock hits the ground. The plate stores the “new” potential energy until the next upheaval, when it starts again. Spencer Weart Hastings-on-Hudson, New York, US To convince yourself gravity doesn’t diminish over time, try this. Take something heavy in your hand and move it up and down with your eyes closed, while imagining it is attached to the floor by a spring that you are stretching and relaxing. The “spring” is the gravitational field. When you raise the rock, you put some energy into the field. When you lower it, the field gives back the energy. This doesn’t change 54 | New Scientist | 7 December 2019
FENG YU/ALAMY STOCK PHOTO
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?
This week’s new question Gambler’s fallacy When using an online casino, how can I tell whether prizes are awarded by chance, albeit with the odds stacked against me, or by an AI that knows how frequently and by how much I, personally, have to be baited to maximise the casino’s revenue? Dave Neale, Truro, Cornwall, UK
the strength of the spring that pulls on other rocks or on you. Mark J. Bridger Oxford, UK The question bears on the accelerating expansion of the cosmos caused by dark energy. Because things are moving apart, the gravitational potential energy in the universe should be increasing. Yet kinetic energy is also increasing, seeming to break the overall energy conservation principle. An alternative is that the accelerating expansion is itself a kind of “falling”, a motion caused by gravity. That might suggest the existence of a greater gravitational universe outside our own.
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?
Richard Swifte Darmstadt, Germany The human retina is sensitive to the ultraviolet (UV) spectrum down to about 300 nanometres,
but the lens of the eye filters it out. This adaptation perhaps arose to protect the retina from the more damaging UV. It also avoids the increased blurry effect of having too wide a spectral range, since different wavelengths focus at different distances from the lens. Artificial lenses are designed to block UV. But people born without a lens, or who have a lens removed and not replaced, sometimes report seeing ultraviolet as a whitish-violet light. One example is the Impressionist painter Claude Monet, who developed bad cataracts in later life and eventually had his left eye’s lens removed. His subsequent works heavily feature bluish colours, often thought to be the result of him seeing UV. Brian Horton West Launceston, Tasmania, Australia Normal colour vision ranges
from wavelengths of around 380 nanometres (violet) to 750 nanometres (red). Most people can’t easily see light shorter than 380 nanometres because the lens of the eye absorbs it. If the lens is missing or removed, often due to cataracts, light below the violet range isn’t blocked and can be detected down to around 310 nanometres. Without the lens to focus light, these people are far-sighted and need corrective lenses to focus at short distances. Insects can see ultraviolet light, and some other animals have vision in this range too. Bob Butler Llangoed, Anglesey, UK Some years ago, after being admitted to hospital with sepsis, I developed uveitis, an eye inflammation that could have caused permanent loss of vision. The lens of my right eye was removed and replaced with an artificial one. The new lens meant I could see better through this eye than I ever had before. On leaving hospital, I decided I deserved a pint of bitter. Standing at the bar of my local pub, I noticed that their device for detecting counterfeit banknotes was emitting very bright bluish light. I mentioned this to the barman, who looked at me with a very quizzical expression but made no comment. I then realised that he couldn’t see the light: it was visible through my right eye alone. It seems that the natural lens in the eye has a filtering effect as a protection against ultraviolet light. I owe the staff of the emergency eye clinic my thanks not only for saving my eyesight, but also for my ability to see UV light. ❚
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
Shrinking gravity
Oliver Knott (age 12) Olney, Buckinghamshire, UK When rocks are taken uphill, they gain gravitational potential energy from whatever brought them up. When they fall down, this becomes kinetic energy, which is released as heat or used to break the rocks when they reach the bottom. The energy doesn’t come from gravity, it comes from whatever brought the rocks up. So gravity doesn’t diminish over time. Robert Willis Nanaimo, British Columbia, Canada Rocks build up potential energy, usually over eons, as the ground is pushed up by tectonic movements. This transfers some of a tectonic plate’s kinetic energy into potential energy in the now-higher rocks. At some point, probably due to erosion, they fall back down, quickly converting their potential energy back to kinetic energy. This is then transferred back to the underlying tectonic plate as the rock hits the ground. The plate stores the “new” potential energy until the next upheaval, when it starts again. Spencer Weart Hastings-on-Hudson, New York, US To convince yourself gravity doesn’t diminish over time, try this. Take something heavy in your hand and move it up and down with your eyes closed, while imagining it is attached to the floor by a spring that you are stretching and relaxing. The “spring” is the gravitational field. When you raise the rock, you put some energy into the field. When you lower it, the field gives back the energy. This doesn’t change 54 | New Scientist | 7 December 2019
FENG YU/ALAMY STOCK PHOTO
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?
This week’s new question Gambler’s fallacy When using an online casino, how can I tell whether prizes are awarded by chance, albeit with the odds stacked against me, or by an AI that knows how frequently and by how much I, personally, have to be baited to maximise the casino’s revenue? Dave Neale, Truro, Cornwall, UK
the strength of the spring that pulls on other rocks or on you. Mark J. Bridger Oxford, UK The question bears on the accelerating expansion of the cosmos caused by dark energy. Because things are moving apart, the gravitational potential energy in the universe should be increasing. Yet kinetic energy is also increasing, seeming to break the overall energy conservation principle. An alternative is that the accelerating expansion is itself a kind of “falling”, a motion caused by gravity. That might suggest the existence of a greater gravitational universe outside our own.
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?
Richard Swifte Darmstadt, Germany The human retina is sensitive to the ultraviolet (UV) spectrum down to about 300 nanometres,
but the lens of the eye filters it out. This adaptation perhaps arose to protect the retina from the more damaging UV. It also avoids the increased blurry effect of having too wide a spectral range, since different wavelengths focus at different distances from the lens. Artificial lenses are designed to block UV. But people born without a lens, or who have a lens removed and not replaced, sometimes report seeing ultraviolet as a whitish-violet light. One example is the Impressionist painter Claude Monet, who developed bad cataracts in later life and eventually had his left eye’s lens removed. His subsequent works heavily feature bluish colours, often thought to be the result of him seeing UV. Brian Horton West Launceston, Tasmania, Australia Normal colour vision ranges
from wavelengths of around 380 nanometres (violet) to 750 nanometres (red). Most people can’t easily see light shorter than 380 nanometres because the lens of the eye absorbs it. If the lens is missing or removed, often due to cataracts, light below the violet range isn’t blocked and can be detected down to around 310 nanometres. Without the lens to focus light, these people are far-sighted and need corrective lenses to focus at short distances. Insects can see ultraviolet light, and some other animals have vision in this range too. Bob Butler Llangoed, Anglesey, UK Some years ago, after being admitted to hospital with sepsis, I developed uveitis, an eye inflammation that could have caused permanent loss of vision. The lens of my right eye was removed and replaced with an artificial one. The new lens meant I could see better through this eye than I ever had before. On leaving hospital, I decided I deserved a pint of bitter. Standing at the bar of my local pub, I noticed that their device for detecting counterfeit banknotes was emitting very bright bluish light. I mentioned this to the barman, who looked at me with a very quizzical expression but made no comment. I then realised that he couldn’t see the light: it was visible through my right eye alone. It seems that the natural lens in the eye has a filtering effect as a protection against ultraviolet light. I owe the staff of the emergency eye clinic my thanks not only for saving my eyesight, but also for my ability to see UV light. ❚
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