Tag Archives: Science

Ancient Astronomy

The Night Sky

Evidence indicates that people were interested in observing and understanding the sky and the celestial objects thousands of years ago. For example, the 4000 year old Stonehenge, in southern England was believed to be built to predict the positions of the sun and the moon.

Written records of astronomical observations left by the ancient Babylonians, Egyptians and the Chinese exist today. During 1300’s B.C., Chinese astronomers mapped the positions of the stars and recorded the eclipses. By about 700 B.C., the Babylonians were predicting when the planets would appear closest and farthest from the sun. The ancient Egyptians determined the beginning of springtime by the position of the brightest star in the sky, the Sirius.

Pythagoras, a Greek philosopher and scientist who lived about 500 B.C., reasoned that the earth was round. During the A.D, 100’s Claudius Ptolemy, a Greek astronomer who lived in Alexandria, Egypt published a work called the Almagest promoting the idea that the planets, the sun, moon and the stars all revolved around the earth.

Astronomers accepted Ptolemy’s geocentric (earth-centered) theory for over 1500 years until Nicolaus Copernicus’s revolutionary heliocentric (sun-centered) theory, that the earth and the other planets revolved around the sun, took hold. So began the Modern Astronomy.

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How Are Earthquakes Measured?

Earthquakes

An earthquake is an intense vibration of the earth’s surface. There are two primary ways to measure earthquakes: magnitude, and intensity. These factors also determine the extent of damage caused by the earthquake.

Magnitude

Magnitude is the most common way to measure the size of an earthquake. It is calculated on the Richter’s scale, which describes how powerful the quake was. Magnitude is measured using a machine called the seismometer. Seismometers allow us to detect and aptly record earthquakes by converting vibrations caused by seismic waves into electric signals.

There are two types of seismic waves that pass through the earth’s body:

P-Waves

These are longitudinal waves that shake the ground back and forth along the direction of travel of the wave. They travel the fastest.

S-Waves

These are traverse waves. Their motion is perpendicular to the direction of the wave. They are slower than p-waves.

The Richter Scale

Charles F. Richter invented the Richter scale in 1953 as a quantitative measure of an earthquake’s size. Until recently, earthquakes were measured using the Richter scale. However, new and improved scales have now upended the dated Richter scale.

When an earthquake occurs, its magnitude can be assigned a specific numerical value on the Richter scale. The magnitude is then measured using the logarithm of the amplitude of the largest seismic wave calibrated to a scale with a seismograph’s help. A Richter scale is typically numbered 1-10, although there is no upper limit.

Earthquakes between 1 and 2 on the scale are small and unnoticeable, while earthquakes measuring 7 or up can wreak significant havoc.

Intensity

An earthquake’s intensity measures the strength of the shaking caused by the earthquake. The intensity is usually highest at the epicenter and continues to subside as it moves away. Different tools are used to measure earthquakes’ intensity, including the Modified Mercalli Intensity scale and the European Macroseismic Scale (EMS).

With inherent flaws in the Richter scale, improvements have been made to record more accurate measurements of earthquakes, taking both magnitude and intensity into account.

Author: Amita Vadlamudi

Understanding SONAR

Submarine

In simple terms, Sonar refers to a system used to transmit sound waves underwater. It also receives the reflections of sound waves and uses that information to detect underwater depths or the existence of and/or the locations of the submerged objects. Sonar is an acronym for Sound Navigation and Ranging.

A Sonar device sends out sound waves at a steady frequency and then listens to the waves that return to the source. The data from the reflected sound waves is then relayed to operators through a display on a monitor or a loudspeaker.

Invented by Lewis Nixon in 1906, the importance of the technology grew as it came in handy for the detection of submarines during the First World War. Nixon is credited with inventing the first device to detect sound waves underwater, but the first device capable of detecting submarines was invented by Paul Langevin in 1915.

Initially, sonar systems relied on listening to sounds underwater without any sounds being sent out. Active sonar systems that send and receive sounds came forth by 1918 in both the U.S. and Britain. The need for detecting submarines created the perfect opportunity for further development of the technology, but it never came into use for the First World War.

During the Second World War, active sonar systems came into use, and it was also when the term Sonar was initially coined.

Primarily, there are two types of active sonar systems. Short-range active sonar systems emit pings or pulses of constantly changing frequency. The receiver of such sonar systems relies on differentiating between the sound emitted and sound received to process the gain and derive the information about the detection of distances.

Long-term active sonar systems rely on low-frequency pulses instead. They measure the time elapsed between the transmission and the detection of the low-frequency sound waves under water.

Passive sonar systems do not send out sounds, but they listen. Typically used for military applications, these sonar systems rely on a massive sonar database to accurately detect different classes of ships and maneuvers, based on the sound their movement makes.

While sonar systems are mainly used for military purposes, they have several other uses as well. Depth detection, diving safety, communications at sea and even commercial fishing nowadays rely on the technology due to its effectiveness in underwater detection.

Look for other technology related articles on this site by Amita Vadlamudi.

The Doppler Radar

A Radar sends out radio waves that reflect off of the targeted objects. The reflected radio waves return back to the radar and can be analyzed for the presence, direction, distance and speed of the targeted objects. Following the principles of a radar, the Doppler radar specifically detects the speed of an object.

Doppler radar detects the speed of an object based on the natural law of the radio waves. As the object gets closer to the source, the waves produced by an object will crowd closely together. As the object moves farther away from the source, the waves spread farther apart.

A Doppler radar system uses pulse timing techniques for measuring the range to a target. Initially used for the detection of fighter aircraft during the 60s, Doppler radar has widespread use in meteorological radars. It is used to predict the weather.

Doppler radars in weather detection systems can detect both precipitation and wind. The radar system emits a short pulse of radio waves. If the pulse strikes an object (raindrops, snowflakes, birds), the radar waves become scattered in all directions. At the same time, a small portion is reflected back towards the radar.

Computers analyze the strength of the returning signal, the time it took to travel to the object and return, and the frequency shift of the pulse. The computers convert the change in the reflected pulse of energy to determine the velocity of the object either toward or from the radar. The information about the movement of objects towards or away from the radar provides the measure of the wind speed.

Essentially, a Doppler radar system allows us to “see” the wind which enables the National Weather Service to detect different facets of the weather conditions. This feature comes in particularly handy to detect the formation of a tornado, which is why the National Weather Service can issue tornado warnings in advance.

Doppler radars are typically able to detect most precipitation within a 90-mile radius of the radar itself while it can detect snow or intense rainfall at a wider radius of 155 miles. They are not very likely to detect light snowfall or rainfall as accurately over a long distance.

A former Information Technology professional, Amita Vadlamudi currently spends time studying and researching into science and technology topics. This is one of Amita Vadlamudi’s many articles on tools and technologies used in the exploration of science.

Facts about Microscopes

Microscope

A microscope is an optical instrument that is used to produce enlarged images of very small objects. The most popular kind of microscope is an optical microscope that functions through a lens, forming images from the light. An acoustic microscope employs high-frequency ultrasound to form images. There is also an electron microscope which forms images from electronic beams. However, the most simple and basic type of microscope is an “optical microscope”. It comes with a single lens, magnifying glasses, and jeweler’s loupes.

Unlike a simple microscope having a single lens, a compound microscope has two lenses. The primary features of a compound microscope are the objective, used for holding the lens near the specimen, and the eyepiece that holds the lens near the observer. A modern compound microscope also comprises of a mirror which acts as a source of light, a focusing mechanism, and a surface where the object is placed to be examined. A compound microscope may also include a built-in camera for the purpose of microphotography.

During the 1st century AD, glass had been invented by the Romans. They observed that if one held a lens over an object, the object would look bigger. These lenses were referred to as “magnifiers” or “burning glasses”. Around the same time, Seneca discovered the magnification of objects by a globe of water. It wasn’t until 1600 that lenses were produced to be worn as spectacles. In the late 17th century, Antony Van Leeuwenhoek – a Dutch draper and scientist, became the first man to produce and use a real microscope. He made his own microscope which included a single convex glass lens and was hand-held by a metal holder.

Leeuwenhoek became more involved in Science and attempted various methods to improve the microscope. With his new and advanced microscope, he was able to see objects that no one else had encountered before. Owing to the invention of the microscope, scientists were able to see bacteria, yeast, blood cells, and many tiny insects that were difficult to detect otherwise. With the aid of microscopes, scientists and doctors were enabled to conduct more advanced and extensive research in the fields of science and medicine respectively.

Different microscopes are constructed for different applications. Hence, it is imperative that one invest in a microscope which suits their application. One will need a compound microscope, a high powered instrument, used for viewing small specimens like bacteria, germs, and water organisms. On the other hand, a stereo microscope is a low-powered microscope, used to view slightly visible specimens like insects, bugs, leaves, and rocks.

A Look into Telescope

The telescope is an optical instrument used to observe objects that are a significant distance away, especially those that are not seen directly by the naked human eye. It is a collection of lenses and/or mirrors that allows the user to see objects that are far away, by either increasing the brightness around the object or by magnifying the object. The telescopes are able to perform at different levels of the electromagnetic spectrum from the radio waves to gamma rays.

The first optical telescope, according to some sources, was made by the Dutch lens-grinder names Hand Lippershey in the year 1608. Around the same time Galileo developed the first ever astronomical telescope. It was a tube that contained two lenses of different focal length that had been aligned on one axis.

Using this telescope, and the different versions that followed after, Galileo performed the first telescopic observation of the sky. During this time he discovered the lunar mountains, Jupiter’s four moons, sunspots, and the stars of the Milky Way.

There are two basic types of telescopes: the refracting telescope and the reflecting telescope.

The refracting telescope uses two lenses to work the light to focus on the object which tends to appear bigger than it really is. Both the lenses are convex lenses which work by bending the light inwards. The biggest refracting telescope in the world is present in the Yerkes Observatory of the University of Chicago.

The reflecting telescopes do not use lenses. They use mirrors to focus the light on the object and then they reflect the image back to the user.

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