HOW DO TRACTOR BEAMS WORK?

How do tractor beams work?

•Up until recently, tractor beams (beams of light that tow objects) existed only in the world of science fiction.

•While large-scale tractor beams that can tow space ships are still machines of the future, microscopic tractor beams are here today.

•The idea at first seams to defy physics. Shoot light at an object and the light's momentum should push the object away from the light source according to the law of conservation of momentum; not pull it closer like a tractor dragging its cargo.

•But what if you managed to create a situation where upon striking the object, the light gains forward momentum instead of losing it.

•In that case, the law of conservation of momentum tells us that the object will lose momentum in the forward direction, even to the point of going backwards, towards the light source.

•So there is a way to make a tractor beam without violating any physics, if you can get the light to gain forward momentum upon interacting with the object.

•You need to the light to slingshot past the object instead of bouncing off of it. The most effective method to accomplish this feat at this point in time is to use solenoidal light beams.

•A solenoidal shape is like a wire wrapped in circles into a helix that forms a hollow cylinder. But in this case, there are no wires. The light itself, traveling through the air, is formed into this hollow, spiraling shape.

•San-Hyuk Lee of UC Berkeley and his collaborators have experimentally verified that the solenoidal light shape indeed draws objects – in their case, microscopic glass spheres – towards the light source.

•They have therefore successfully created a real tractor beam.

•You can think of the spiral-shaped light beam as a screw that twists the object up the beam.

•Only microscopic objects have been tractor-beamed so far because light carries so little momentum.

•In order to tow large objects, you would need very strong light beams. So strong, in fact, that damage of the object may become a problem. Research is ongoing.

Comments

HOW CAN WE MOTIVATE OURSELVES MORE EFFECTIVELY THROUGH REINFORCEMENT?

•We'd all like to be more effective in reaching our goals, and according to behaviorists, the way to improve our effectiveness is by rewarding ourselves for the little steps that take us closer and closer to those desirable outcomes. •First, find something you really like to do or something you'd like to have that can, realistically, serve as a reward. •Then, take the goal that you are hoping to achieve that, realistically, you could achieve but just haven't succeeded at yet. •Next, work backward from that goal to your present state. •Arrange to give yourself those desired rewards as you inch closer from where you are now to the desired end point. •As you start to make progress, only give yourself a reward when you've moved forward from where you are now. •For example, if you'd like to cut back on your television watching and instead read more often, reward yourself by allowing yourself to watch television only when you've read for 20 minu...

WHY DO WE SLEEP AND DREAM?

•We spend about one-third of our lives sleeping. •Why do we invest so much time in sleep? •The most straight forward answer is that, sleep is restorative, and it replenishes the body's energy stores. •However, intense neural activity during rapid eye movement (REM) sleep, the stage in which most dreams occur, suggests there may be more to the story. •One theory, which by far has the largest body of evidence, is that sleep plays a critical role in learning and consolidating memories. •It is probably why infants and toddlers need up to 14 hours of sleep a day, with half of it spent in REM sleep. •In adults, dreams may also play a role in brain plasticity and learning, which is why sleep-deprived adults perform worse in memory tests and tasks.

Inside an MRI scanner

When doctors need the highest quality images possible they turn to MRI scanners, but how do they work? MRI scan ,MRI test, MRI use in medical field, constitutent of MRI machine. Doctors often plan treatments based on imaging. X-rays, ultrasound and CT scans provide useful pictures, but when the highest quality images are needed, they turn to MRI scanners. While CT scanners use x-rays and therefore expose the patient to radiation, magnetic resonance imaging (MRI) uses powerful magnets and is virtually risk free. MRI scans are obtained for many medical conditions, although since they are expensive and complicated to interpret, they certainly aren’t as easy as taking a chest x-ray. Examples for which they are used include planning surgery for rectal cancers, assessing bones for infection (osteomyelitis), looking at the bile ducts in detail for trapped gallstones, assessing ligamental damage in the knee joints and assessing the spinal cord for infections, tumours or...

Knowledge N Fact4u

Search This Blog