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 Energy conversion from coal is done?

Single generator sets of over 600 MW are now used in the UK, though there are many smaller generators in use. A 600 MW generator can supplythe average needs of over 1 million UK households. Three or four such generators are typically installed in a single large coal-fired station which isoften sited close to a coal mine, away from the city dwellers who consume the electricity. Such generators are usually driven by a compound arrangement of highpressure, intermediate-pressure and low-pressure turbines, increasing in size as the pressure decreases. Modern turbines rotate in a speed range from 1500 to 3500 r.p.m., usually 3000 r.p.m. for the UK’s 50 Hz system. For large coal-fired plant the steam pressure could be 25 megapascals (MPa) with steam temperatures of 500–600 °C to improve the thermodynamic efficiency. In nuclear reactors, which operate under less demanding conditions, the steam is superheated to about 5 MPa and 300 °C. Modern water tube boilers are complex and have ...

20 Interesting science fact (PART 2)

1/ Astronauts cannot belch - there is no gravity to separate liquid from gas in their stomachs. 2/ The air at the summit of Mount Everest, 29,029 feet is only a third as thick as the air at sea level. 3/ One million, million, million, million, millionth of a second after the Big Bang the Universe was the size of a ...pea. 4/ DNA was first discovered in 1869 by Swiss Friedrich Mieschler. 5/ The molecular structure of DNA was first determined by Watson and Crick in 1953. 6/ The first synthetic human chromosome was constructed by US scientists in 1997. 7/ The thermometer was invented in 1607 by Galileo. 8/ Englishman Roger Bacon invented the magnifying glass in 1250. 9/ Alfred Nobel invented dynamite in 1866. 10/ Wilhelm Rontgen won the first Nobel Prize for physics for discovering X-rays in 1895. 11/ The tallest tree ever was an Australian eucalyptus - In 1872 it was measured at 435 feet tall. 12/ Christian Barnard performed the first heart transplant i...

Why swiss Bank is Famous for Black Money?

Hello everyone, here we are going to talk about Swiss Bank. When a person hear the name of this bank the only thing that come to our mind is Black Money. When any kind Fraud occur we hear the name of Swiss Bank and Government also tell that he is going to bring all the black money from Swiss Bank. Swiss Bank is located in Switzerland and was established in 1872 as Basler bankverein. According to Switzerland banking law bank officials cannot disclose the name of account holder name unless and until Swiss court order them. Swiss court give the order only when there is a criminal charge on account holder name for example money laundering, fraud etc. The account in Swiss Bank are secretive account. Anyone who open a bank account in Swiss Bank he has to complete his KYC as normal bank do. But they never reveal the identity and address of account holders name. The account is in coded digits. In bank statement the account holder name is also not disclosed to any one. Here Swi...

Knowledge N Fact4u

Search This Blog