Guide to Space Archives

August 24, 2011December 24, 2015 by Matt Williams

Beaufort Scale

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The high seas. Tankers, fishing trawlers and naval craft watch the horizon with eager anticipation. The wind is high and the waves are rising. The ship’s anemometer (wind speed detector) reads sixty-five kilometers per hour. The perfect storm is coming! Back on land, people are observing much of the same. The high winds are picking up debris, throwing it around and causing much damage. The waves are high and crashing all along the coast and even further inland. Power lines are destroyed, trees uprooted, and houses looking out to sea pelted by seawater and hard rain. In the aftermath of all this, this storm would been classified as 12 on the Beaufort Scale. Alternately known as the Beaufort Wind Force Scale, this is an empirical measure that relates wind speed to observed conditions at sea or on land.

Officially devised in 1805 by an Irish-born Royal Navy Officer named Sir Francis Beaufort (apparently while serving on the HMS Woolwich), this scale has a long and complicated history. It began with Daniel Defoe, the English novelist who, after witnessing of the Great Storm of 1703, suggested that a scale of winds be developed based on 11 points and used words common to the English language. By the early 19th century, there was renewed demand for such a scale, as naval officers were hard pressed to make accurate weather observations that weren’t tainted by partiality. Beaufort’s scale was therefore the first standardized scale to be introduced, and has gone through a number of variations since.

The initial scale of thirteen classes (zero to twelve) did not reference wind speed but related to qualitative wind conditions based on the effects it had on the sails of a British man-of-war. At zero, all the sails would be up; at six, half of the sails would have been taken down; and at twelve, all sails would have to be stowed away. In the late 1830’s, the scale was made standard for all Royal Navy vessels and used for all ship’s logs. In the 1850’s it was adapted to non-naval use, with scale numbers corresponding to cup anemometer rotations. By 1916, to accommodate the growth of steam power, the descriptions were changed to how the sea, not the sails, behaved and extended to land observations. It was extended once again in 1946 when Forces 13 to 17 were added, but only for special cases such as tropical cyclones.

Today, many countries have abandoned the scale and use the metric-based units m/s or km/h instead, but the severe weather warnings given to public are still approximately the same as when using the Beaufort scale. For example, wind speeds on the 1946 Beaufort scale are based on the empirical formula: v = 0.836 B3/2 m/s, where v is the equivalent wind speed at 10 meters above the sea surface and B is the Beaufort scale number. Oftentimes, hurricane force winds are described using the Beaufort scales 12 through 16 in conjunction with the Saffir-Simpson Hurricane Scale, by which actual hurricanes are measured.

We have written a few related articles for Universe Today. Here’s an article about, and here’s an article about the F5 tornado. Also, here are some extreme weather pictures.

If you’d like more info on the Beaufort Scale, check out this Wikipedia entry about the Beaufort Scale. Also, check out the NOAA Beaufort Wind Scale.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:
http://en.wikipedia.org/wiki/Anemometer
http://en.wikipedia.org/wiki/Beaufort_scale
http://www.tc.gc.ca/eng/marinesafety/tp-tp10038-80-wi-beaufort-scale-324.htm
http://weather.mailasail.com/Franks-Weather/Historical-And-Contemporay-Versions-Of-Beaufort-Scales

August 21, 2011October 1, 2016 by Matt Williams

What is Galactic Cannibalism?

Seattle, January, 2003. Two prestigious astronomers: Puragra GuhaThakurta of UCSC and David Reitzel of UCLA present some new findings to the American Astronomical Society that would seem to indicate that large spiral galaxies grow by gobbling up smaller satellite galaxies. Their evidence, a faint trail of stars in the nearby Andromeda galaxy that are thought to be a vast trail of debris left over from an ancient merger of Andromeda with another, smaller galaxy. This process, known as Galactic Cannibalism is a process whereby a large galaxy, through tidal gravitational interactions with a companion galaxy, merges with that companion, resulting in a larger galaxy.

The most common result of this process is an irregular galaxy of one form or another, although elliptical galaxies may also result. Several examples of this have been observed with the help of the Hubble telescope, which include the Whirlpool Galaxy, the Mice Galaxies, and the Antennae Galaxies, all of which appear to be in one phase or another of merging and cannibalising. However, this process is not to be confused with Galactic Collision which is a similar process where galaxies collide, but retain much of their original shape. In these cases, a smaller degree of momentum or a considerable discrepancy in the size of the two galaxies is responsible. In the former case, the galaxies cease moving after merging because they have no more momentum to spare; in the latter, the larger galaxies shape overtakes the smaller one and their appears to be little in the way of change.

All of this is consistent with the most current, hierarchical models of galaxy formation used by NASA, other space agencies and astronomers. In this model, galaxies are believed to grow by ingesting smaller, dwarf galaxies and the minihalos of dark matter that envelop them. In the process, some of these dwarf galaxies are shredded by the gravitational tidal forces when they travel too close to the center of the “host” galaxy’s enormous halo. This, in turn, leaves streams of stars behind, relics of the original event and one of the main pieces of evidence for this theory. It has also been suggested that galactic cannibalism is currently occurring between the Milky Way and the Large and Small Magellanic Clouds that exist beyond its borders. Streams of gravitationally-attracted hydrogen arcing from these dwarf galaxies to the Milky Way is taken as evidence for this theory.

As interesting as all of these finds are, they don’t exactly bode well for those of us who call the Milky Way galaxy, or any other galaxy for that matter, home! Given our proximity to the Andromeda Galaxy and its size – the largest galaxy of the Local Group, boasting over a trillion stars to our measly half a trillion – it is likely that our galaxy will someday collide with it. Given the sheer scale of the tidal gravitational forces involved, this process could prove disastrous for any and all life forms and planets that are currently occupy it!

We have written many articles about galactic cannibalism for Universe Today. Here’s an article about ancient galaxies feeding on gas, and here’s an article about an article, Galactic Ghosts Haunt Their Killers.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We’ve also recorded an episode of Astronomy Cast about galaxies. Listen here, Episode 97: Galaxies.

Sources:
http://en.wikipedia.org/wiki/Interacting_galaxy
http://en.wikipedia.org/wiki/Andromeda_Galaxy
http://www1.ucsc.edu/currents/02-03/01-13/debris.html
http://blogs.physicstoday.org/update/2009/10/galactic-cannibalism.html
http://news.discovery.com/space/hubble-spiesz-aftermath-of-galactic-cannibalism.html

July 16, 2011July 24, 2020 by Matt Williams

What are Active Optics?

For astronomers and physicists alike, the depths of space are a treasure trove that may provide us with the answers to some of the most profound questions of existence. Where we come from, how we came to be, how it all began, etc. However, observing deep space presents its share of challenges, not the least of which is visual accuracy.

In this case, scientists use what is known as Active Optics in order to compensate for external influences. The technique was first developed during the 1980s and relied on actively shaping a telescope’s mirrors to prevent deformation. This is necessary with telescopes that are in excess of 8 meters in diameter and have segmented mirrors.

Definition:

The name Active Optics refers to a system that keeps a mirror (usually the primary) in its optimal shape against all environmental factors. The technique corrects for distortion factors, such as gravity (at different telescope inclinations), wind, temperature changes, telescope axis deformation, and others.

The twin Keck telescopes shooting their laser guide stars into the heart of the Milky Way on a beautifully clear night on the summit on Mauna Kea. Credit: keckobservatory.org/Ethan Tweedie — *The twin Keck telescopes shooting their laser guide stars into the heart of the Milky Way on a beautifully clear night on the summit on Mauna Kea. Credit: keckobservatory.org/Ethan*

Adaptive Optics actively shapes a telescope’s mirrors to prevent deformation due to external influences (like wind, temperature, and mechanical stress) while keeping the telescope actively still and in its optimal shape. The technique has allowed for the construction of 8-meter telescopes and those with segmented mirrors.

Use in Astronomy:

Historically, a telescope’s mirrors have had to be very thick to hold their shape and to ensure accurate observations as they searched across the sky. However, this soon became unfeasible as the size and weight requirements became impractical. New generations of telescopes built since the 1980s have relied on very thin mirrors instead.

But since these were too thin to keep themselves in the correct shape, two methods were introduced to compensate. One was the use of actuators which would hold the mirrors rigid and in an optimal shape, the other was the use of small, segmented mirrors which would prevent most of the gravitational distortion that occur in large, thick mirrors.

This technique is used by the largest telescopes that have been built in the last decade. This includes the Keck Telescopes (Hawaii), the Nordic Optical Telescope (Canary Islands), the New Technology Telescope (Chile), and the Telescopio Nazionale Galileo (Canary Islands), among others.

*The New Technology Telescope (NTT) pioneered the Active Optics. Credit: ESO/C.Madsen. Bacon*

Other Applications:

In addition to astronomy, Active Optics is used for a number of other purposes as well. These include laser set-ups, where lenses and mirrors are used to steer the course of a focused beam. Interferometers, devices which are used to emit interfering electromagnetic waves, also relies on Active Optics.

These interferometers are used for the purposes of astronomy, quantum mechanics, nuclear physics, fiber optics, and other fields of scientific research. Active optics are also being investigated for use in X-ray imaging, where actively deformable grazing incidence mirrors would be employed.

Adaptive Optics:

Active Optics are not to be confused with Adaptive Optics, a technique that operates on a much shorter timescale to compensate for atmospheric effects. The influences that active optics compensate for (temperature, gravity) are intrinsically slower and have a larger amplitude in aberration.

*Artist’s impression of the European Extremly Large Telescope deploying lasers for adaptive optics. Credit: ESO/L. Calçada/N. Risinger*

On the other hand, Adaptive Optics corrects for atmospheric distortions that affect the image. These corrections need to be much faster, but also have smaller amplitude. Because of this, adaptive optics uses smaller corrective mirrors (often the second, third or fourth mirror in a telescope).

We have written many articles about optics for Universe Today. Here’s The Photon Sieve Could Revolutionize Optics, What did Galileo Invent?, What did Isaac Newton Invent?, What are the Biggest Telescopes in the World?

We’ve also recorded an entire episode of Astronomy Cast all about Adaptive Optics. Listen here, Episode 89: Adaptive Optics, Episode 133: Optical Astronomy, and Episode 380: The Limits of Optics.

Sources:

July 4, 2011December 24, 2015 by Matt Williams

Absorption of Light

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Those who can remember sitting through elementary science class might recall learning that with all matter, light is absorbed and converted into energy. In the case of plants, this process is known as photosynthesis. However, they are by no means the only species or objects that do this. In truth, all objects, living or inorganic are capable of absorbing light. In all cases, absorption depends on the electromagnetic frequency of the light being transmitted (i.e. the color) and the nature of the atoms of the object. If they are complementary, light will be absorbed; if they are not, then the light will be reflected or transmitted. In most cases, these processes occur simultaneously and to varying degrees, since light is usually transmitted at various frequencies. Therefore most objects will selectively absorb light while also transmitting and/or reflecting some of it. Wherever absorption occurs, heat energy is generated.

As already noted, absorption depends upon the state of an objects electrons. All electrons are known to vibrate at specific frequencies, what is commonly known as their natural frequency. When light, in the form of photons, interacts with an atom with the same natural frequency, the electrons of that atom will become excited and set into a natural vibrational motion. During this vibration, the electrons of the atom interact with neighboring atoms in such a way as to convert this vibrational energy into thermal energy. Subsequently, the light energy is not to be seen again, hence why absorption is differentiated from reflection and transmission. And since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies of visible light.

By relying on this method, physicists are able to determine the properties and material composition of an object by seeing which frequencies of light it is able to absorb. Whereas some materials are opaque to some wavelengths of light, they transparent to others. Wood, for example, is opaque to all forms of visible light. Glass and water, on the other hand, are opaque to ultraviolet light, but transparent to visible light.

Ultimately, absorption of electromagnetic radiation requires the generation of the opposite field, in other words, the field which has the opposite coefficient in the same mode. A good demonstration of this is color. If a material or matter absorbs light of certain wavelengths (or colors) of the spectrum, an observer will not see these colors in the reflected light. On the other hand if certain wavelengths of colors are reflected from the material, an observer will see them and see the material in those colors. For example, the leaves of green plants contain a pigment called chlorophyll, which absorbs the blue and red colors of the spectrum and reflects the green. Leaves therefore appear green, whereas reflected light often appears to the naked eye to be refracted into several colors of the spectrum (i.e. a rainbow effect).

We have written many articles about the absorption of light for Universe Today. Here’s an article about absorption spectra, and here’s an article about absorption spectroscopy.

If you’d like more info on light absorption, check out an article about Light Absorption, Reflection, and Transmission. Also, here’s an article about reflection and absorption of light.

We’ve also recorded an entire episode of Astronomy Cast all about Energy Levels and Spectra. Listen here, Episode 139: Energy Levels and Spectra.

Sources:
http://en.wikipedia.org/wiki/Absorption_%28electromagnetic_radiation%29
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/ligabs.html
http://www.physicsclassroom.com/class/light/u12l2c.cfm
http://www.andor.com/learning/light/?docid=333
http://www.chemicool.com/definition/absorption_of_light.html
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/photosyn.html#c1

July 4, 2011October 18, 2016 by Matt Williams

What is Absolute Space?

The explosion in the sciences that took place in the 17th and 18th centuries revolutionized not only the way we think of our world, but of time and space itself. Much of this is owed to individuals like Sir Isaac Newton, a man whose theories came to form the basis of modern physics. Though much of his theories would later come to be challenged with the discovery of relativity and quantum mechanics, they were nonetheless extremely influential because they gave later generations a framework. It is to him, for example, that we are indebted for the notions of Absolute Time and Absolute Space, and how the two were thought to be separate aspects of objective reality.
In his magnum opus, PhilosophiæNaturalis Principia Mathematica (Mathematical Principles for Natural Philosophy), Newton laid the groundwork for the concept of Absolute Space thusly:

“Absolute space, in its own nature, without regard to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces; which our senses determine by its position to bodies: and which is vulgarly taken for immovable space … Absolute motion is the translation of a body from one absolute place into another: and relative motion, the translation from one relative place into another.”

In other words, Absolute Space is the study of space as an absolute, unmoving reference point for what inertial systems (i.e. planets and other objects) exist within it. Thus, every object has an absolute state of motion relative to absolute space, so that an object must be either in a state of absolute rest, or moving at some absolute speed.

These views were controversial even in Newton’s own time. However, it was with the advent of modern physics and the Theory of Special Relativity, that much of the basis for Newtonian physics would come to be shattered. In essence, special relativity proposed that time and space are not independent realities but different expressions of the same thing. In this model, time and motion are dependent on the observer and there is no fixed point of reference, only relative forms of motion which are determined by comparing them to other points of reference.

However, it would be fair to say that it was Newton’s own definitions of space and time as independent phenomena that allowed for the development of physics as we know it today. By giving physicists clear definitions to work with and challenge, later generations of scientists like Einstein were able to express clearly how space was not absolute since it itself was always in motion, and how one could not divorce space from time.

We have written many articles about absolute space for Universe Today. Here’s an article about what is space, and here’s an article about how cold space is.

If you’d like more info on absolute space, check out an article about Isaac Newton’s “Absolute Space”. Also, here’s an article about Absolute Time and Space.

We’ve also recorded an entire episode of Astronomy Cast all about Space Elevators. Listen here, Episode 144: Space Elevators.

Sources:
http://en.wikipedia.org/wiki/Absolute_time_and_space
http://en.wikipedia.org/wiki/Sir_Isaac_Newton
http://plato.stanford.edu/entries/newton-stm/
http://en.wikipedia.org/wiki/Special_relativity
http://novan.com/spcenrgy.htm

July 4, 2011April 26, 2016 by Matt Williams

What is Absolute Pressure?

When it comes to measurements, the everyday kind that deal with things like air pressure, tire pressure, blood pressure, etc., there is no such thing as an absolute accuracy. And yet, as with most things, scientists are able to come up with a relatively accurate way of gauging these things by measuring them relative to other things. When it comes to air pressure (say for example, inside a tire), this takes the form of measuring it relative to ambient air temperature, or a perfect vacuum. The latter case, where zero pressure is referred against a total vacuum, is known as Absolute Pressure. The name may seem slightly ironic, but since the comparison is against an environment in which there is no air pressure to speak of.

In the larger context of pressure measurement, Absolute Pressure is part of the “zero reference” trinity. This includes Absolute Pressure (AP), Gauge Pressure, and Differential Pressure. As already noted, AP is zero referenced against a perfect vacuum. This is the method of choice when measuring quantities where absolute values must be determined. Gauge Pressure, on the other hand, is referenced against ambient air pressure, and is used for conventional purposes such as measuring tire and blood pressure. Differential Pressure is quite simply the difference between the two points.

Cases where AP are used include atmospheric pressures readings: where one is trying to determine air pressure (expressed in units of atm’s, where one is equal to 101,325 Pa), Mean Sea Level pressure (the air pressure at sea level; on average: 101.325 kPa), or the boiling point of water (which varies based on elevation and differences in air pressure). Another instance of AP being the method of choice is with the measurement of deep vacuum pressures (aka. outer space) where absolute readings are needed since scientists are dealing with a near-total vacuum. Altimeter pressure is another instance, where air pressure is used to determine the altitude of an aircraft and absolute values are needed to ensure both accuracy and safety.

To produce an absolute pressure sensor, manufacturer will seal a high vacuum behind the sensing diaphragm. If the connection of an absolute pressure transmitter is open to the air, it will read the actual barometric pressure (which is roughly 14.7 PSI). This is different from most gauges, such as those used to measure tire pressure, in that such gauges are calibrated to take into account ambient air pressure (i.e. registering 14.7 PSI as zero).

We have written many articles about absolute pressure for Universe Today. Here’s an article about Boyle’s Law, and here’s an article about air density.

If you’d like more info on absolute pressure, check out an article about pressure from Wikipedia. Also, here’s another article from Engineering Toolbox.

We’ve also recorded an entire episode of Astronomy Cast all about Temperature. Listen here, Episode 204: Temperature.

Sources:
http://en.wikipedia.org/wiki/Pressure_measurement
http://www.pumpworld.com/absolute%20pressure.htm
http://www.sensorsone.co.uk/pressure-measurement-glossary/absolute-pressure.html
http://en.wikipedia.org/wiki/Atmospheric_pressure
http://en.wikipedia.org/wiki/Altimeter

June 8, 2011April 26, 2016 by Tega Jessa

Galaxy Shapes

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Science revealed to us that universe as we know it, is composed of billions of galaxies like our own Milky Way. When you consider how many stars are just in our own galaxy you can get just a small idea how big our universe really is. Despite this astronomers have made great strides in learning more about the galaxies and their different characteristics. One aspect that was defined early was their shapes. Thanks to the work of famous astronomer Edwin Hubble we know that just about any galaxy in the universe will have one of 4 different shapes, spiral, elliptical, lenticular, and irregular.

Spiral galaxies are one of the most familiar galaxy shapes. In fact when most people think of a galaxy, this type of galaxy shape is the first to come to mind. This is because the Milky Way is a prime example of a spiral galaxy. A spiral galaxy looks like a pinwheel. It is basically the nucleus with its different “arms” spiraling outwards. Spiral galaxies can be tight or loose to varying degrees. One important fact about spiral galaxies is that young stars are formed in the outer arms while older stars are found near the center.

The next two types of galaxies are elliptical and lenticular shaped galaxies. These types are the kinds that are the most similar. First they have few or no dust lanes and are largely composed of older mature stars. These types seldom have star forming areas. Of the four galaxy shapes this is the most cohesive and organized.

The final galaxy shape is the irregular galaxy shape. Irregulars have an indeterminate shape. These galaxies are often small and don’t have enough gravitational force to organize into a more regular form. The Hubble telescope has taken images of famous irregular galaxies like the Magellanic Clouds. Irregular galaxies can also be large galaxies that have undergone a major gravitational disturbance.

As you now see the four basic galaxy shapes seem to cover just about every type of galaxy out there. Like any classification of shape there are also subcategories. An interesting observation recently made about the shape of galaxies is the role that their formation plays in determining their shape. It is now thought that galaxies get their shape as they naturally develop, merge with other galaxies or disrupt each other’s path. This is another great mystery as we don’t currently have the technology to plot out the complete paths of galaxies in the universe.

We have written many articles about galaxy shapes for Universe Today. Here’s an article about irregular galaxy, and here’s an article about spiral galaxy.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We’ve also recorded an episode of Astronomy Cast about galaxies. Listen here, Episode 97: Galaxies.

Source:
http://www.oneminuteastronomer.com/OMALibrary/galaxy-shapes.html

June 6, 2011December 24, 2015 by Tega Jessa

How High Do Planes Fly

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Have you ever asked how high do planes fly? The answer is easy to understand when you remember how flight for aircraft works. The first thing to know is that air is a fluid just like water. So it works under the same rules. Any object that moves in a fluid is under the influence of four forces, drag, lift, weight, and thrust. The net total has to be positive so that the influence of thrust and lift keeps a plane in the air. Thrust and lift depend on the density of the air. So it is easier to achieve the ideal lift and thrust at higher elevations than lower elevations. So how high a plane flies is not fixed except for the limit of the vacuum of space of where the atmosphere becomes too thin for aerodynamics to work.

Lift and thrust are the main forces that make flight possible. As long as they are greater than weight or drag, plane will fly. Thrust is the forward acceleration produced by a plane’s engine. The less dense the air the more thrust a plane must produce to create the needed lift. The full explanation is pretty complicated but the best way to put is that every plane has a maximum condition it achieves to fly. This maximum is the best possible combination of density, speed, and lift to fly the plane. That is why the height a plane can fly can vary so much. It depends on the needs of the plane.

A good example is commercial turbo jets. Turbo jets fly below the speed of sound. The also weigh a lot. In order to reach optimal flight conditions and fly at speeds convenient enough to make air travel profitable, most commercial planes fly at 30,000 feet. This is high enough that a plane has the least amount of drag and can reach the top speed its engines can produce safely. Supersonic craft like fighter jets and spy planes can fly much higher. This is because they design of the plane makes it easier for the plane to resist drag and produce greater thrust to compensate for the thinner air.

So we see that how high a plane can fly is determined by its use, the drag, the lift, thrust, and weight. We also know that a planes absolute limit will be where air becomes too thin to act like a fluid which is the uppermost level of the atmosphere. Right now scientist are looking to take advantage of this upper level of the atmosphere to help planes fly even faster. However there are still barriers such as friction and engine design.

We have written many articles about airplanes for Universe Today. Here’s an article about the largest airplane, and here’s an article about pictures of airplanes.

If you’d like more info on airplanes, check out these articles from How Stuff Works. Here’s an article about How Airplanes Fly.

We’ve also recorded an entire episode of Astronomy Cast all GPS Navigation. Listen here, Episode 212: GPS Navigation.

Sources:
NASA
How Stuff Works

April 17, 2011December 24, 2015 by Tega Jessa

Solar Disruption Theory

Why Do Planets Orbit the Sun — The Solar System

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Solar disruption theory was one of several theories that emerged before the 18th century concerning the formation of the solar system. Solar disruption theory states that the collision of the sun with another stars caused debris to be ejected from its mass and these debris eventually became the planets. This theory was later discarded for the nebula theory of solar system formation. However there are some scientists that propose that it has some merit.

The big question up until the 18th century was how the solar system was born. There were many explanations for why this happen but many were really only conjecture given the tools available to astronomers at the time. The real question was what would be a probable origin under the known laws of physics. The advent of classical mechanics came to prove the nebular theory as the likely theory for the creation of the solar system. The reason was that most other theories could not explain how the planets formed without giving in to the Sun’s gravity and falling in.

A new argument has emerged for a different form of solar disruption theory in this version it answers the idea in a more roundabout way that answers an interesting question. We know that the formation of the solar system itself was volatile but did the Sun and its planets really form in relative isolation from other star emerging in the Nebula? This new theory that emerged in 2004 supposed proposed that the influence of other stars may have influenced the formation of planets in the solar system.

In the meanwhile the main theory stands. We know in the nebular theory that stars are formed from spinning nebulas of gases and cosmic dust. Over time the masses clump together to the point where the mass reaches the level needed for gravity to initiate fusion. The planets are formed from the clumps of debris in the nebular disk that did not fall into the Sun and that they eventually ended up colliding with each other forming planets. Any theory that suggests interference from the gravity fields of other star systems has not been tested yet. It may have merit but we don’t have the technology to test theories on such large scales.

We have written many articles about solar disruption theory for Universe Today. Here are some interesting facts about the Solar System, and here’s an article about the model of the Solar System.

If you’d like more info on the Solar System, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

We’ve also recorded a series of episodes of Astronomy Cast about every planet in the Solar System. Start here, Episode 49: Mercury.

Reference:
http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/solarsysform.htm

April 3, 2011October 11, 2016 by Tega Jessa

What is a Warm Front?

[/caption]A warm front is the transition zone that marks where a warm air mass starts replacing a cold air mass. Warm fronts tend to move from southwest to southeast. Normally the air behind a warm front is warmer than the air in front of it. Normally when a warm front passes through an area the air will get warmer and more humid. Warm fronts signal significant changes in the weather. Here are some of the weather signs that appear as a warm front passes over a region.

First before the warm front arrives the pressure in area start to steadily decrease and temperatures remain cool. The winds tend to blow south to southeast in the northern hemisphere and north to northeast in the southern hemisphere. The precipitation is normally rain, sleet, or snow. Common cloud types that appear would various types of stratus, cumulus, and nimbus clouds. The dew point also rises steadily

While the front is passing through a region temperatures start to warm rapidly. The atmospheric pressure in the area that was dropping starts to level off. The winds become variable and precipitation turns into a light drizzle. Clouds are mostly stratus type clouds formations. The dew point then starts to level off.

After the warm front passes conditions completely reverse. The atmospheric pressure rises slightly before falling. The temperatures are warmer then they level off. The winds in the northern hemisphere blow south-southwest in the northern hemisphere and north-northwest in the southern hemisphere. Cloudy conditions start to clear with only cumulonimbus and stratus clouds. The dew point rises then levels off.

Knowing about how warm fronts work gives a better understanding of how pressure systems interact with geography to create weather. Looking at warm fronts we learn that they are the transition zone between warm humid air masses and cool, dry air masses. We know that these masses interact in a cycle of rising and falling air that alters the pressure of atmosphere causing changes in weather.

We have written many articles about warm front for Universe Today. Here’s an article about cyclones, and here’s an article about cloud formations.

If you’d like more info on warm front, check out NOAA National Weather Service. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Reference:
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/af/frnts/wfrnt/def.rxml