Every week, the BBC Focus magazine solves some doubts of its readers. Below is a selection of their responses for the curious.
How does robotic surgery work?
The Da Vinci Robotic Surgery System (pictured) consists of a four-armed, spider-legged apparatus operated by a surgeon from a control panel in the operating room, a few feet away from the patient.
The surgeon uses it to control, for example, the tip of the scalpel with sub-millimeter accuracy.
The incisions can be made smaller than with conventional methods and there is less bleeding, reducing the recovery period for prostate surgeries from six to two weeks.
The movement is adjusted in such a way that when the surgeon moves the hand, the tip of the instrument is advanced only a fraction of that distance, allowing for more precise movements.
According to the manufacturer Intuitive Surgical, the tip of the instrument can move only 1 millimeter for every 3 millimeters of movement of the hand.
The doctor also uses a 3D visualization system along with a camera inside the patient, so that the procedure can be seen in the greatest detail.
Why do our eyes dry?
The eyes are covered with a thin film of fluid that makes the surface optically smooth.
The fluid is secreted by the cornea and lacrimal glands of the eye.
«Dry eye» syndrome, or keratoconjunctivitis sicca, occurs when you don’t produce enough tears or blink hard enough.
Blinking is important because tears cannot spread fast enough on their own to compensate for the rate of evaporation.
Driving a car, reading, or staring at a computer screen can decrease the rate of blinking.
Tear production declines with age, but it can also be affected by damage to the nerves of the cornea from contact lenses or eye surgery.
Which animal can perceive the highest frequency sound?
wax moth, melonella galleryhe can hear ultrasonic frequencies up to 300kHz (humans can’t hear anything above 20kHz).
The moth uses this ability to detect the ultrasonic calls of bats.
The highest frequency calls bats can make are 212kHz, so moths have a clear advantage.
What is the orbit of a planet that revolves around two suns?
There are many possible orbital shapes that planets can describe in binary systems. It depends on the mass of the two stars, their separation, the mass of the planet, the distance of each star, and whether it orbits only one of the stars or both.
Located far enough away, the planet will circle the two stars in an elliptical orbit.
If it is closer, the orbit can be forced to describe various shapes that slowly change orientation, like the patterns obtained with a spirograph.
There are even orbits shaped like a long sausage, flower petals, or that periodically cross the two stars.
Complex orbits like these can be rare, since many of them are inherently unstable and break easily.
Figure eight orbits are not possible.