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Hourglass figure
The back pages Almost the last word Why do wasps have such a narrow join between the thorax and abdomen?
Freewheeling I rapidly lose my balance if I try to ride my bike with no hands, but I can easily ride it when the tip of just one finger is lightly touching the handlebars. Is that finger providing significant support or do I just believe that I can’t ride a bike no‑handed?
Peter Peters Sherborne, Dorset, UK More active than the gyroscopic effect in keeping a bike upright is the so-called trail effect, in which the line of the steering axis – from the handlebars down the front forks to the ground – intersects the road ahead of the point where the tyre makes contact. But both effects are small and usually augmented by the rider applying a light torque to the handlebars. The third effect is shifting the position of the rider’s centre of mass. This is very effective when riding no-handed and has to be learned. Unless our rider has a physical difficulty, he can teach himself to ride no-handed in spite of any inhibition resulting from earlier failures. Peter McPherson Merriott, Somerset, UK I have often wondered why with some bikes I can ride no-handed 54 | New Scientist | 5 October 2019
What is the smallest body of water that is influenced by the moon’s gravitational pull?
This week’s new questions Hourglass figure Why do wasps have such a narrow waist? What could be the advantage of having such a narrow join between thorax and abdomen, which seems like a very weak point? Rosalind Coles, Clyro, Powys, UK Needing focus I wear spectacles to correct for myopia and astigmatism. Is it possible to create a program to adjust the image of a TV, mobile or PC monitor using my optical prescription such that I could view it without spectacles? Mike Daw, Cheltenham, Gloucestershire, UK
whereas on others, I have to quickly re-grasp the handlebars. I came to the conclusion that it is due to the front wheel not being able to function properly as a gyroscope if the bearings in the front fork are a bit tight. When riding with no hands and with well-fitted bearings, any slight tendency to lean from a vertical posture causes the front wheel to turn slightly in the direction of lean, thereby replicating what happens when you corner. But stiff bearings slightly resist that turn of the wheel and balance is lost. The questioner, with his single finger on the bars, is simply overcoming the reluctance of the stiff bearings to turn. Philip Taylor Buckland Dinham, Somerset, UK When a bicycle is travelling slowly, it needs greater steering correction to maintain balance, hence it tends to wobble at slow speed. The trick to riding no‑handed is to have sufficient
ANTAGAIN/GETTY IM AGES
Matt Chamings Barnstaple, Devon, UK When a bike is in motion it doesn’t just fall over because the spinning wheels act as gyroscopes, which maintain their orientation. The front wheel only turns, and potentially unbalances the bike, if the rider leans to one side. So riding a bike with no hands is easy as long as the rider stays fairly still. Pedalling shifts weight from side to side, so freewheeling is easier. Keeping one finger on the handlebar is comforting but not absolutely necessary. Possibly the rider becomes anxious when removing the finger and shifts weight by tensing up. So yes, unbalancing could be down to lack of belief or confidence.
Time and tide
grip on the saddle and pedals to be able to steer the bike, and so cause the front wheel to turn one way or the other. If not, one finger on the handlebar will enable you to microsteer and stay upright. Unicycles are balanced in the same way, by turning the single wheel via the saddle. Imagine trying to ride a bike with a non-steerable fixed front wheel. You would quickly crash down on one side or the other, it being impossible to balance such a machine. Hilary Johnson Malvern, Worcestershire, UK As well as physical or psychological support, the finger on the handlebars may be providing feedback to help the cyclist adjust their balance.
Chris Hughes Professor of sea level science, University of Liverpool, UK Every body of water is influenced, but the effect is much harder to see in smaller ones. The smallest body of water in which lunar tides have been measured is Loch Ness in the UK, which is 37 kilometres long. Here, the tides have an amplitude of about 1.5 millimetres. Tides result from the small differences in the moon’s gravitational attraction from place to place on Earth. In water, this results in differences in surface height up to about 0.8 mm for points 10 km apart. Ocean tides are much larger than this suggests because the pull oscillates about twice a day, close to the time it takes water to slosh naturally around ocean basins, producing a resonance effect that amplifies the rising of the water. In smaller basins such as the Mediterranean, or lakes, this effect is weaker. Another factor is that land is also pulled up by the moon, and these combined effects would give a tide of 0.45mm in Loch Ness. But the tide there is bigger than this because the weight of water in the surrounding seas plays a role. High tides push down on the UK coast and cause Loch Ness to tilt from end to end. Most of what is measured as a tide is the result of this tilt – the land moves more than the water. Disentangling these effects is very tricky, so it is hard to tell whether the moon affects a small body of water. ❚
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
Freewheeling I rapidly lose my balance if I try to ride my bike with no hands, but I can easily ride it when the tip of just one finger is lightly touching the handlebars. Is that finger providing significant support or do I just believe that I can’t ride a bike no‑handed?
Peter Peters Sherborne, Dorset, UK More active than the gyroscopic effect in keeping a bike upright is the so-called trail effect, in which the line of the steering axis – from the handlebars down the front forks to the ground – intersects the road ahead of the point where the tyre makes contact. But both effects are small and usually augmented by the rider applying a light torque to the handlebars. The third effect is shifting the position of the rider’s centre of mass. This is very effective when riding no-handed and has to be learned. Unless our rider has a physical difficulty, he can teach himself to ride no-handed in spite of any inhibition resulting from earlier failures. Peter McPherson Merriott, Somerset, UK I have often wondered why with some bikes I can ride no-handed 54 | New Scientist | 5 October 2019
What is the smallest body of water that is influenced by the moon’s gravitational pull?
This week’s new questions Hourglass figure Why do wasps have such a narrow waist? What could be the advantage of having such a narrow join between thorax and abdomen, which seems like a very weak point? Rosalind Coles, Clyro, Powys, UK Needing focus I wear spectacles to correct for myopia and astigmatism. Is it possible to create a program to adjust the image of a TV, mobile or PC monitor using my optical prescription such that I could view it without spectacles? Mike Daw, Cheltenham, Gloucestershire, UK
whereas on others, I have to quickly re-grasp the handlebars. I came to the conclusion that it is due to the front wheel not being able to function properly as a gyroscope if the bearings in the front fork are a bit tight. When riding with no hands and with well-fitted bearings, any slight tendency to lean from a vertical posture causes the front wheel to turn slightly in the direction of lean, thereby replicating what happens when you corner. But stiff bearings slightly resist that turn of the wheel and balance is lost. The questioner, with his single finger on the bars, is simply overcoming the reluctance of the stiff bearings to turn. Philip Taylor Buckland Dinham, Somerset, UK When a bicycle is travelling slowly, it needs greater steering correction to maintain balance, hence it tends to wobble at slow speed. The trick to riding no‑handed is to have sufficient
ANTAGAIN/GETTY IM AGES
Matt Chamings Barnstaple, Devon, UK When a bike is in motion it doesn’t just fall over because the spinning wheels act as gyroscopes, which maintain their orientation. The front wheel only turns, and potentially unbalances the bike, if the rider leans to one side. So riding a bike with no hands is easy as long as the rider stays fairly still. Pedalling shifts weight from side to side, so freewheeling is easier. Keeping one finger on the handlebar is comforting but not absolutely necessary. Possibly the rider becomes anxious when removing the finger and shifts weight by tensing up. So yes, unbalancing could be down to lack of belief or confidence.
Time and tide
grip on the saddle and pedals to be able to steer the bike, and so cause the front wheel to turn one way or the other. If not, one finger on the handlebar will enable you to microsteer and stay upright. Unicycles are balanced in the same way, by turning the single wheel via the saddle. Imagine trying to ride a bike with a non-steerable fixed front wheel. You would quickly crash down on one side or the other, it being impossible to balance such a machine. Hilary Johnson Malvern, Worcestershire, UK As well as physical or psychological support, the finger on the handlebars may be providing feedback to help the cyclist adjust their balance.
Chris Hughes Professor of sea level science, University of Liverpool, UK Every body of water is influenced, but the effect is much harder to see in smaller ones. The smallest body of water in which lunar tides have been measured is Loch Ness in the UK, which is 37 kilometres long. Here, the tides have an amplitude of about 1.5 millimetres. Tides result from the small differences in the moon’s gravitational attraction from place to place on Earth. In water, this results in differences in surface height up to about 0.8 mm for points 10 km apart. Ocean tides are much larger than this suggests because the pull oscillates about twice a day, close to the time it takes water to slosh naturally around ocean basins, producing a resonance effect that amplifies the rising of the water. In smaller basins such as the Mediterranean, or lakes, this effect is weaker. Another factor is that land is also pulled up by the moon, and these combined effects would give a tide of 0.45mm in Loch Ness. But the tide there is bigger than this because the weight of water in the surrounding seas plays a role. High tides push down on the UK coast and cause Loch Ness to tilt from end to end. Most of what is measured as a tide is the result of this tilt – the land moves more than the water. Disentangling these effects is very tricky, so it is hard to tell whether the moon affects a small body of water. ❚
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