Application of em waves

APPLICATION OF EM WAVES IN EXTRA TERRESTRIAL SEARCH

Abstract This term paper contains information about electromagnetic waves, their formation and properties. It contains application of em waves and its application in extra terrestrial life and a research on extra terrestrial life

Keywords-Electromagnetic Waves(em waves), Extra Terrestrial life(ets), Application(app),Search For Extra Terrestrial Intelligence(SETI), Electric Field(E), Magnetic Field(B).

I. Introduction

This term paper is a research on electromagnetic waves and their applications especially its application in extra terrestrial search. We have already studied about em waves and its applications but its application in extra terrestrial search is really very interesting. To search on extra terrestrial life an intelligence committee is formed by NASA named as SETI i.e Search For Extra Terrestrial Intelligence which is leaded by Dr Seti.

II ELECTROMAGNETIC WAVES

Electromagnetic waves are formed when an electric field couples with a magnetic field . The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave. James Clerk Maxwell and Heinrich Hertz are two scientists who studied how electromagnetic waves are formed and how fast they travel.

III CREATING AN EM WAVE

We've already learned how moving charges (currents) produce magnetic fields. A constant current produces a constant magnetic field, while a changing current produces a changing field. We can go the other way, and use a magnetic field to produce a current, as long as the magnetic field is changing. This is what induced emf is all about. A steadily-changing magnetic field can induce a constant voltage, while an oscillating magnetic field can induce an oscillating voltage.

Focus on these two facts:

A. An oscillating electric field generates an oscillating magnetic field.

B. An oscillating magnetic field generates an oscillating electric field

Those two points are key to understanding electromagnetic waves.

An electromagnetic wave (such as a radio wave) propagates outwards from the source (an antenna, perhaps) at the speed of light. What this means in practice is that the source has created oscillating electric and magnetic fields, perpendicular to each other, that travel away from the source. The E and B fields, along with being perpendicular to each other, are perpendicular to the direction the wave travels, meaning that an electromagnetic wave is a transverse wave. The energy of the wave is stored in the electric and magnetic fields.

IV Properties of EM Waves

Something interesting about light, and electromagnetic waves in general, is that no medium is required for the wave to travel through. Other waves, such as sound waves, can not travel through a vacuum. An electromagnetic wave is perfectly happy to do that.

An electromagnetic wave, although it carries no mass, does carry energy. It also has momentum, and can exert pressure (known as radiation pressure). The reason tails of comets point away from the Sun is the radiation pressure exerted on the tail by the light (and other forms of radiation) from the Sun.

The energy carried by an electromagnetic wave is proportional to the frequency of the wave. The wavelength and frequency of the wave are connected via the speed of light:

Electromagnetic waves are split into different categories based on their frequency (or, equivalently, on their wavelength). In other words, we split up the electromagnetic spectrum based on frequency. Visible light, for example, ranges from violet to red. Violet light has a wavelength of 400 nm, and a frequency of 7.5 x 1014 Hz. Red light has a wavelength of 700 nm, and a frequency of 4.3 x 1014 Hz. Any electromagnetic wave with a frequency (or wavelength) between those extremes can be seen by humans.

Visible light makes up a very small part of the full electromagnetic spectrum. Electromagnetic waves that are of higher energy than visible light (higher frequency, shorter wavelength) include ultraviolet light, X-rays, and gamma rays. Lower energy waves (lower frequency, longer wavelength) include infrared light, microwaves, and radio and television waves.

V APPLICATION OF EM WAVES

  • Used in satellite communication
  • Used in broadcasting technology
  • Used in optical fibre communication
  • Used in mobile communication
  • Used in RADAR
  • Used in GPS
  • Used in Bird migration
  • Used in microwave communication
  • Used in IR communication
  • Used in infrared imaging
  • Used in Bluetooth communication
  • Used in microwave communication
  • Used in extra terrestrial search

VI SEARCH FOR EXTRA TERRESTRIAL LIFE- SETI

Mankind has long wondered if we are alone in the Universe. Since about 1960, a number of research projects have attempted to detect such other forms of intelligent life.

Whether or not alien life exists, those projects are certain to fail.

The projects that have been pursued in SETI (the Search for Extra-Terrestrial Intelligence) are based on several assumptions that are certainly wrong.

It might be true that there is extra-terrestrial intelligent life, and it may also be true that we could some day find a way to detect it, and we may someday even find a way to communicate with them. To accomplish these things, attitudes and experiments must be very different from present efforts.

All existing efforts are based extensively on egocentric assumptions. We on earth generally use modulated radio waves to transmit information from one point to another. This is an extremely inefficient approach! Enormous amounts of radiant energy are needed to transmit signals that carry rather minimal amounts of information. Even now, our technicians are aware of much more effective and efficient ways of transferring information from one place to another. Over the upcoming centuries and millennia, it is certain that our scientists will discover far better methods of communication that we cannot even imagine now. Such extremely advanced communication methods would certainly be used by advanced life forms in the Universe. They would be foolish indeed if they choose to use primitive methods like ours.

We, on earth, only discovered the existence of radio waves about one hundred years ago. For all the thousands of years of previous human societies, we were completely ignorant of the existence of the many forms of electromagnetic radiation that always surround us.

Less than one hundred years ago, we discovered how to create radio waves. Soon afterward, we discovered how to "modulate" those waves with lower frequency electrical signals that carried the information of sounds, and later pictures. This technology only came into existence during the lives of some people who are still living! In other words, our knowledge and experience in creating and detecting such waves are extremely primitive!

Even though we have accomplished a lot during this century, with radio and television and many similar technologies now surrounding our lives, we have only the most minimal understanding and experience in such fields. Come back to me in ten thousand years, and I will acknowledge that you then pretty much understand the subject! This present human arrogance regarding the belief that ALL is already known about electromagnetic radiation is one of the central incorrect assumptions involved in the SETI efforts.

A second incorrect assumption involves something called "bandwidth". This is related to the amount of information that can be transferred by known methods of modulating radio waves. Using modulated radio waves is a very crude method of transmitting information signals. For example, a modulated light signal can carry over ten billion times as much information as an FM radio signal, and our technology already has learned most of that technology, in our first hundred years of being capable of creating modulated signals.

A third assumption that is almost certain to be wrong is that signal makers would be creating and radiating truly phenomenal amounts of energy fairly indiscriminately as to direction.

Even our primitive hundred-year-old technology has already discovered extremely narrow beam radiation methods such as Lasers and Masers. A precisely directed Laser beam could transmit a message to a specific destination while using less than one-billionth of the radiative energy of conventional radio signals.

If the earth had a colony on a planet in the Alpha Centauri system, four light-years away, consider the possibilities. Would we radiate trillions of watts of radio signal to send our indiscriminately aimed messages, or would we use a few thousands of watts of extremely directed laser signal exactly in that direction? Would we tolerate that low band-width of 10 MHz when we knew that information "conversations" would always take 8.6 years? Doesn't it seem obvious that we would already be using laser narrow modulated light beams to maximize the information transmitted and minimize the power needed?

And this is just after our first hundred years of learning about creating and transmitting electromagnetic signals. Imagine what technology we might be using a thousand years from now? Ten thousand years from now? A million?

However, all of the ongoing SETI projects have assumed that the signals that we should listen for are simple modulated radio signals. It is the equivalent to if we would have teams of reconnaissance personnel watching the horizons for smoke signals, in the hopes of learning what neighboring enemies might be doing. A couple hundred years ago, that would have been worthwhile, but it is probably true than most enemies in the modern world have developed more advanced communications methods. Our personnel that would be now watching for smoke signals would certainly be wasting their time. Not because it wouldn't still work, but because far better methods are available

VII WHY EM WAVES??

Electromagnetic waves (radio waves, light waves, etc.) they argue are the obvious choice. Only these, traveling at the speed of light, can cross the fantastic distances involved without dispersing and in anything resembling a practical amount of time. This leads to the next crucial question: at what frequency will the aliens transmit their signal?

The most rational frequencies for communication between the stars, Morrison and Cocconi argued, were between 1 and 10,000 MHz. Those are the frequencies in which the planetary atmosphere interferes the least with electromagnetic signals, and where radiation noise from our galaxy is also at a minimum. Several years later it was discovered that those were also frequencies in which there was little interference from Cosmic Background Radiation, but this was not known in 1959.

VIII WHY NOT USE LIGHT??

In a conference a question was asked to Dr SETI by a person and the response by doctor was amazing

To Dr. SETI:

Why does SETI use radio signals instead of light signals to search/communicate? To me, light is the most obvious source for navigation, communication, and other purposes. Does our species have different sciences from the extraterrestrials?

The Doctor Responds:

That is an excellent question, Mark. Before I answer it directly, let's clarify some terminology.

When you say "light" you probably mean visible light, electromagnetic radiation at wavelengths to which our human eyes are sensitive. But, to the physicist, "light" includes all electromagnetic waves (since they all travel at the same speed, and follow the same laws of nature). Most such "light" is invisible to our human eyes. We see only a very narrow sliver of the spectrum, extending from red to violet (in terms of wavelength, that's 750 to 400 nm; expressed as frequencies, we see 400 to 750 THz). Of course, we have no way of knowing the range to which alien eyes are adapted, if indeed they have eyes at all.

A number of different types of electromagnetic radiation are included in the category of light to which our human eyes are not sensitive. Radio waves, microwaves, X-rays, gamma rays, infra-red and ultra-violet rays are all light that is "invisible" to our eyes (but not to our instruments). And all can travel through interstellar space.

So, which is best for the SETI enterprise? Those "colors" of light that technology can generate at high power levels, which travel relatively unimpeded through the interstellar medium (and through planetary atmospheres), and for which little or no natural interference exists. A difficult but vital task for SETI scientists is to select the regions of the electromagnetic spectrum in which to concentrate their efforts.

"Searching for Interstellar Communications" was the very first modern SETI article, published in Nature magazine in 1959. In it, Professors Phil Morrison and Giuseppi Cocconi contemplated that very question. Their research at the time was focused on gamma rays, so that's where they started. The two scholars quickly realized that another form of light, in the microwave part of the radio spectrum, was much more likely to succeed. We on Earth could already generate prodigious amounts of microwave radiation. We already had very sensitive microwave receivers (our early radio telescopes). The sky was quiet at these frequencies. And we were already studying the Universe in the microwaves, in search of natural astrophysical phenomena, so it made sense to search the same space for artificial signals as well. We still do much of our SETI research in the part of the invisible light spectrum that Cocconi and Morrison suggested.

But, we don't stop there. Today, we have technology to generate visible and infra-red light at very high power levels indeed (using lasers, something that hadn't even been invented yet when SETI science was born). And, we have sensitive receivers for detecting laser flashes. So, we now practice optical SETI, looking for what you call "light." In other words, we are following your worthy suggestion!

Are there other kinds of "light" we should be exploiting in the SETI enterprise, perhaps as yet undiscovered on Earth? Probably. Prof. Morrison used to talk about "zeta waves," mysterious communications media that we have not yet discovered on Earth, but that extraterrestrial species exploit. You can be sure that, once we discover them, we will certainly start conducting zeta wave SETI! Until then, we use what we have.

IX CONCLUSION

EM Waves are very much useful in extra terrestrial search. Humans have been sending the radio waves at the speed of light for nearly one hundred years now. Altough the goal has been seldom interstellar communication, radio waves is especially appropriate to that task because em waves don't require any travelling medium and because radio waves penetrate very efficiently through gas and dust clouds.Humans have been sending radio waves into space aX REFRENCES

[1] http://physics.bu.edu/~duffy/py106/EMWaves.html

[2] http://mb-soft.com/public/seti.html

[3] http://www.humantruth.info/aliens.html

is especially appropriate to that task because electromagnetic waves generally require no travel media, and because radio waves penetrate very efficiently through gas and dust

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