How Are Rocks Formed?

A'a lava

As a terrestrial planet, Earth is divided into layers based on their chemical and rheological properties. And whereas its interior region – the inner and outer core – are mostly made up of iron and nickel, the mantle and crust are largely composed of silicate rock. The crust and upper mantle are collectively known as the lithosphere, from which the tectonic plates are composed.

It in the lithosphere that rocks are formed and reformed. And depending on the type of rock, the process through which they are created varies. In all, there are three types of rocks: igneous, sedimentary, and metamorphic. Each type of rock has a different origin. Therefore, the question, “How are rocks formed?” begs three distinct answers.

Continue reading “How Are Rocks Formed?”

How are Clouds Formed?

Atmospheric Pollution
Particulates from pollution mixing with clouds above the US (NASA)

[/caption]I bet some of you are fascinated with certain cloud formations. My eldest son once pointed to the sky, excited upon seeing a bunch of clouds taking shape of a menacing dragon. He was however disappointed after a few minutes when the dragon cloud slowly began to deform and fuse with the rest. So how are clouds formed?

First, water evaporates, rises, and fills up the atmosphere. The evaporated water, a.k.a. water vapor then clings to other numerous particles or dust found in the atmosphere. This dust comes from automobiles, fires, volcanoes, bacteria, and sea spray.

As water vapor rises, it cools. Now, the lower the temperature of air, its capacity to hold water vapor (also known as the saturation point of air) also drops.

Eventually, the rising water vapor condenses and forms the structure of the cloud. You can’t however see this structure unless it has its own color. Well, we know that clouds are either white or dark, and that’s why we’re able to see them.

Most clouds are white. That’s because water and ice particles that make up a cloud have just the right amount and sizes to scatter light in all possible wavelengths. When light of practically all wavelengths combine, the result is white light.

However, when too many water and ice particles build up, just like in a storm cloud, much of the scattered light is simply re-scattered into the cloud. In other words, too much particles prevent some of the light from escaping. Hence is the reason why storm clouds are dark.

Try slowly adding milk in water and notice how its color slowly shifts from white to dark as more milk is added.

I’m sure you’ve noticed that clouds easily form on mountains. How are clouds formed on mountains? When a wall of air and water vapor encounters a mountain side, it has nowhere else to go but up the slopes. Well, if you recall, rising water vapor cools and eventually condenses to form clouds.

Thus, mountains don’t have special particles that enhance cloud formation. Rather, it is the barriers that they so form that forces the water vapor to rise and hence develop into cloud structures. A cloud formed due to topographical features is called an orographic cloud.

We’ve got lots of articles about clouds here in Universe Today. For starters, here are two:
Cloud Types
Cirrus Clouds

Here are the links of two more articles from National Oceanic and Atmospheric Administration (NOAA):
Cloud Classifications and Characteristics
Western Region Technical Attachment
Here are two episodes at Astronomy Cast that you might want to check out as well:
Orbit of the Planets, Green Stars, and Oort Cloud Contamination
Sky Surveys

How Many Continents Are There?

The current tectonic plates.

[/caption]Not everyone on this planet is in agreement as with regards to the total number of continents. So how many continents are there then, according to the disagreeing parties?

Well, in Russia, Eastern Europe and Japan, the people there consider the continents of Europe and Asia as one, known as Eurasia. In other places in the world, North and South America are combined as one American continent while separating Europe and Asia instead. Thus, according to these two views, there should only be 6 continents.

There are even geographical views that prefer the presence of both a Eurasian as well as one American continent. These geographers therefore contend that there should only be 5 continents.

And if you thought that would be the lowest number, think again. There are others still who are more comfortable with a 4-continent view.

These people argue that, since Europe and Asia are actually part of one great land mass and that Asia and Africa are actually joined by an isthmus (Isthmus of Suez), as are the two Americas (being joined by the Isthmus of Panama), then there should be an Afro-Eurasian continent in addition to one American continent, Antarctica, and Australia.

But how many continents are there according to the more widely accepted view? In the most widely accepted view, there are 7 continents all in all: Asia, Africa, Europe, North America, South America, Antarctica, and Australia.

This model is preferred by the Chinese and majority of the English-speaking countries.

The final verdict as to how many continents are there might lean more on the larger numbers once the effects of global warming kick in. Once sea water levels rise, the separation between the two Americas as well as that between Africa and Asia will be more noticeable. Only the combined Europe and Asia model (a.k.a. 6-continent model) and the 7-continent model would remain.

Hundreds of millions of years from now, we really don’t know how many continents there would be. According to the continental drift theory, moving tectonic plates may rearrange the pieces of the puzzle that are the Earth’s continents.

What used to be one super continent, known as Pangaea has now been broken into 4, 5, 6, or 7 continents – depending on which side you’re more comfortable with. Therefore, its plausible, the Earth being round and all, that some of these continents will later on combine after drifting away for some time.

You can read more about plate tectonics here in Universe Today. Here are the links:

There’s more about it at USGS. Here are a couple of sources there:

Here are two episodes at Astronomy Cast that you might want to check out as well:

National Geographic

How Does Geothermal Energy Work

Geothermal Hotspots
Geothermal Hotspots

In order to understand why geothermal energy is considered an environment friendly alternative to fossil fuel, you must first be familiar with the basic workings of this technology. So how does geothermal energy work?

First of all, geothermal energy can be used in a variety of ways. There are those who utilize the heat directly for home heating (and even cooling) systems. Others use them in greenhouses, fish farms, and spas. Of course, I haven’t forgotten its most celebrated application – to produce electricity.

Thus, in answering the question, “How does geothermal energy work?”, one must first specify the specific application of the energy.

For those applications which utilize geothermal energy directly like those in fish farms, spas, and greenhouses, hot spring water is simply tapped from underneath the ground surface and redirected into these facilities.

The hot water may get its heat from magma that is able to creep upward and heat its surroundings, including the groundwater there. Magma doesn’t have to contribute heat directly though, as this melted mantle material can be found very deep underground and hence difficult to gain access to.

In some cases, where magma isn’t found in the direct vicinity, you can still obtain hot water by simply drilling deep in the ground. Always remember that the deeper you drill, the hotter the temperature gets.

Geothermal energy used to power household room heaters are extracted from the ground (not through water). During winter, ground underneath the surface is warmer than the temperature above. Heat is then extracted by using geothermal heat pumps. A typical geothermal heat pump extracts heat through a series of pipes containing either circulating water or an antifreeze solution, just like a refrigerator or an air conditioning unit.

Now for the last application mentioned earlier. How does geothermal energy work in the case of geothermal power plants?

Just like most power plants (e.g. hydro and wind power), energy is converted to electricity through the use of turbines. There are three ways of doing this.

One method directs hot steam drawn from underground into the turbine. Another draws extremely hot water from underneath, flashes it into steam, which is then directed to the turbine. The third method makes use of a heat exchanger to transfer heat from hot water drawn from underground unto a fluid (isobutane is commonly used) that is directed to the turbine.

In all three methods, the turbine is responsible for converting the kinetic energy of the directed fluid (which makes it turn) into electricity.

Universe Today has some interesting topics related to geothermal energy which you might be interested in. Here are two of them:
Geothermal Heat
Geothermal Heating

You can find more information about geothermal heat pumps from the US Department of Energy as well on the Energy Star website.

Tired eyes? Perhaps you’d like to listen to some Astronomy Cast episodes instead:
Volcanoes, Hot and Cold
Space Elevators


How Do Microwaves Work

How Do Microwaves Work
microwave oven

[/caption]Microwave ovens don’t operate in the same manner as conventional ovens. So how do microwaves work then? Microwave ovens take advantage of the behavior of water molecules when subjected to electromagnetic waves found in the microwave band.

To understand how this happens, we’ll have to comprehend the basic properties of water molecules and microwaves (the electromagnetic waves, not the oven).

The mickey mouse-shaped water molecule is actually a dipole. That is, one side is positively charged while the other is negative.

Microwaves used for cooking, on the other hand, are electromagnetic waves possessing frequencies around the 2.45 GHz range. Now, electromagnetic waves are waves made up of alternating electric and magnetic fields. For this discussion, we’re more concerned with the alternating electric fields because charged particles readily react when exposed to them.

That is, when a positively charged particle is exposed to an electric field, it experiences a force (due to the field) pointing in the direction of the field. By contrast, when a negatively charged particle is exposed to the same field, it experiences a force in the direction opposite to the field.

Now, since an electromagnetic wave (like the microwave) is made up of alternating electric fields, a charge exposed to it will experience forces regularly changing in direction. For water molecules, which are dipoles, the net effect would force the molecules into rotation. Again, since the fields are alternating, the rotation will change from clockwise to counterclockwise at regular time intervals.

The agitated water molecules would then possess heat energy that can rub off (much like friction) to nearby molecules. If the water molecules are well distributed in the body subjected to the microwave (like food, for example), then the entire body can heat up quickly – not to mention, uniformly.

Electromagnetic waves in the microwave range are most suitable for this purpose because the water molecules readily rotate when exposed to such frequencies.

Avoid putting in metal into the microwave oven while heating. The reason is because pointed portions of the metal can accumulate high voltages which can cause dielectric breakdown of the air inside the oven. Once this happens, some harmful gases can be produced.

Since microwave ovens normally don’t have heating elements, temperature can drop right away in the inner walls of the oven. So you’ll only need to worry about getting burned by the food and not the walls.

You can read more about electromagnetic waves here in Universe Today. Want to know about how the 25-year old mystery of X-ray emissions was solved? We’ve also written about how astronomers resolved Milky Way’s mysterious X-Ray glow

There’s more about it at NASA and Physics World. Here are a couple of sources there:
X-Ray Astronomy
X-ray Beams Thin Out

Here are two episodes at Astronomy Cast that you might want to check out as well:
X-Ray Astronomy
Optical Astronomy

Source: Wikipedia

Convex Mirror

Convex Lens

A convex mirror is a spherical reflecting surface (or any reflecting surface fashioned into a portion of a sphere) in which its bulging side faces the source of light. Automobile enthusiasts often call it a fish eye mirror while other physics texts refer to it as a diverging mirror.

The term “diverging mirror” is based on this mirror’s behavior of making rays diverge upon reflection. So when you direct a beam of light on a convex mirror, the mirror will allow the initially parallel rays that make up the beam to diverge after striking the reflective surface.

Since convex mirrors have wider fields of view than other reflective surfaces, such as plane mirrors or concave mirrors, they are commonly used in automobile side mirrors. Having a fish eye on your automobile will allow you to see more of your rear.

A convex mirror is also a good security device. Store owners, for instance, install a number of them inside their stores and orient them in such a way that a single security personnel can see large portions of the store even while monitoring from a single location. They are the large disk-like reflective surfaces that you see near the ceilings of grocery or convenience shops.

The same kind of security devices are installed on automated teller machines to give the person withdrawing a good view of what is happening behind him. Some cell phones are also equipped with these mirrors to aid users when performing a self portrait shot.

Unlike images formed by concave mirrors, an image formed by a convex mirror cannot be projected on a screen. Such an image is called a virtual image. If one is to visualize the location of such a virtual image, then the image is found behind the surface of the mirror.

The complete description of an image formed by a convex mirror is: virtual, diminished in size, and upright. When we say upright, we mean that if you position an arrow in front of this kind of reflecting surface, then the arrowhead of the reflection will point to the same direction as that of the object (the real arrow) itself.

Want to see an object that is both a convex and a concave mirror? Take out a metallic spoon – the inner side is a concave mirror while the outer side is a convex mirror. Notice how your reflection is diminished in size. You may compare that with your reflection on a typical wall-mounted mirror.

Want to read more about mirrors? Here are some articles from Universe Today featuring them:
Parabolic Mirror
Nano-Engineered Liquid Mirror Telescopes

There’s more from NASA

NASA’s Largest Space Telescope Mirror Will See Deeper Into Space
Mirror Production Begins on Webb Telescope

Here are episodes from Astronomy Cast you might be interested in. Lend us your ears!
Shooting Lasers at the Moon and Losing Contact with Rovers
The Moon Part I

Source: The Physics Classroom

Pyramids On Mars

D&M pyramid on mars. Credit: NASA

The Pyramids on Mars are hills or mountains on the surface of Mars that, from a low resolution image, have near-perfect symmetry resembling that of the Egyptian pyramids. These formations are found in the Martian region known as Cydonia, an albedo feature that gained celebrity-like attention in the 1970s.

Some of the images captured of the Martian surface by the Viking Missions in the 70’s showed a formation that closely resembled a humanoid face. E.T. aficionados immediately interpreted this as a structure built by intelligent lifeforms like ours. More photographs of the region (Cydonia) revealed pyramid-like structures.

One of them, the D&M pyramid had a near-perfect symmetry. Since the pyramids were located near the “Face on Mars”, speculations regarding its alien origins gained more followers. According to advocates of the theory, the Face on Mars may have been constructed by inhabitants of the nearby city a.k.a. the Pyramids on Mars.

They even pointed out the peculiar smoothness of the wide region beside the Pyramids on Mars, which may have been a vast body of water such as an ocean. The proximity of the ‘city’ to a large body of water is typical of most inhabitants who would naturally want to be near a huge source of natural resources and a medium for travel.

This fascinating theory or story later on subsided when much higher resolution photos from later expeditions, one in April 5, 1998 and another in April 8, 2001, revealed the Face on Mars as nothing more than a mesa, an elevated piece of land with a flat top and steep sides. Mesas can be found in the southwestern region of the US.

You can also find them in South Africa, Arabia, India, Australia, and of course, Spain. The term ‘mesa’ is actually derived from the Spanish word that means ‘table’. Mesas look pretty much like giant tables rising above a surrounding plain.

The sharper images showed that the top of the mesa did not resemble a face at all. As for the Pyramids on Mars, such geological formations can be found here on Earth. They’re usually formed through the action of ice in glaciation or frost weathering.

Some good examples of such formations here on Earth are Switzerland’s Matterhorn, USA’s Mount Thielsen, Scotland’s Buachaille Etive Mòr, and Canada’s Mount Assiniboine.

We have some related articles here that may interest you:

There’s more about it at NASA. Here are a couple of sources there:

Here are two episodes at Astronomy Cast that you might want to check out as well:

NASA: Unmasking the Face of Mars
NASA Mars Exploration

What is the Fastest Jet In The World?

If you’re thinking the X-15 still holds the record for the fastest jet in the world, think again. That title is now owned by NASA’s X-43A. The unmanned aircraft hit Mach 9.6 (nearly 10 times the speed of sound) on November 16, 2004 at an altitude of 33,223 meters over the Pacific Ocean.

Of course, if you’re talking about manned flights, the X-15 with its Mach 6.72 speed is still king of the hill.

Both the X-15 and the X-43A are experimental aircrafts, designed to test new technologies and are usually associated with record-breaking feats. The X-15, for example, was specially designed to reach altitudes and speeds never achieved before.

Pilots of these planes were considered astronauts since many X-15 flights exceeded 50-mile altitudes. Many of them practically reached what is known as the Karman line a.k.a. the ‘edge of space’. That’s about 100 km above sea level.

If you’re looking for an aircraft that’s actually been put to use outside gathering experimental data, then the record holder is the SR-71 “Blackbird”. The Blackbird used to cruise at Mach 3.2 and was used primarily for reconnaissance missions.

Anyway, back to the fastest jet in the world – whether manned or unmanned.

As mentioned earlier, the X-43A, like its reputable predecessor, the X-15, is an experimental aircraft. Specifically, the the X-43 was part of the NASA Hyper-X program, a 7-yr program that cost around $230M and was launched to explore other options for space access vehicles.

At the heart of the X-43 is the scramjet or Supersonic Combustion Ramjet. You can think of it as an upgraded version of the ramjet – the kind of engine used by the SR-71. The Supersonic Combustion Ramjet basically takes in oxygen, which is needed for combustion, directly from the atmosphere. In order to create thrust, rockets mix liquid oxygen with liquid fuel.

In the usual jet plane setup, a tank of liquid oxygen has to be carried as additional load. Take that tank away, and you get a smaller, lighter plane. The added benefits are so enormous that engineers who embarked on scramjet research predicted speeds that could go up to 15 times the speed of sound.

Although the current record held by the scramjet-powered X-43A only achieved a fraction of that, Mach 9.6 is still way above what other planes have achieved.

To give you an idea how fast the fastest jet in the world is, compared to others, imagine this: there are more than 30 jets that are faster than the speed of sound and yet almost all of them have top speeds either way below or only near Mach 3. Mach 9.6 is definitely way way faster than that.

We have some articles in Universe Today that are related to this one. Here are two of them:

Related articles brought to you by NASA, here are the links:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Source: NASA

Mount Krakatoa

Illustration of the Krakatoa eruption.

[/caption]Mount Krakatoa is a volcanic island found in Indonesia. Its most famous eruption in 1883 is one of the biggest in recorded history. You guessed it right; Krakatoa belongs to the Pacific Ring of Fire, the volatile horseshoe-shaped area bordering the Pacific Ocean.

Better known as Krakatau in Indonesia, its eruption in 1883 produced a series of tsunamis that smashed into 165 coastal villages in Java and Sumatra. 36,000 people perished when those giant waves hit. Most of those who were killed during the 1883 eruption, which lasted for two days (Aug 26 to 27), were actually victims of the tsunamis.

Some of the giant waves from that eruption, which rose up to 40 meters, managed to reach the southern part of the Arabian Peninsula, some 7,000 km away. When the 2004 Indian Ocean Tsunami (a.k.a. the 2004 Indonesian Tsunami) struck, it reminded the scientific community of the 1883 eruption because of the proximity of their points of origin.

The eruption also had a large impact on the global climate. On the average, temperature dropped by as much as 1.2ºC in the succeeding year. In the years that followed, global climates were very erratic, stabilizing only 4 years after.

Mount Krakatoa’s lava was known to be made of dacite or rhyolite. This explains the magnitude of its eruption. Generally speaking, volcanic eruptions are more explosive if their lava is composed of dacite or rhyolite. They are cooler and stickier than basalt, allowing them to accumulate pressure before being set free.

Although the 1883 eruption destroyed more than 60% of the volcanic island, a submarine eruption in 1927 produced a new island in its stead. This volcano is aptly called Anak Krakatau, which is Indonesian for “Child of Krakatoa”. Anak Krakatau’s radius is estimated to be 2 kilometers and rises up to a maximum height of 300 meters above sea level. Studies have shown in to be growing at a rate of 5 meters per year.

Before 1883, three volcanoes known as Rakata, Danan, and Perbuwatan combined to what then became Krakatoa island.

Mount Krakatoa is an example of a stratovolcano, a tall, conical volcano with multiple strata of solidified lava, tephra, as well as volcanic ash. These type of volcanoes typically have steep sides and usually erupt frequently & violently. Most of the popular eruptions have been made by stratovolcanoes. Other known stratovolcanoes are Mount St. Helens and Mount Pinatubo.

Indonesia is the country that holds the biggest number of active volcanoes, at 130. Iceland, another volcano-dotted country, holds about the same number (of volcanoes) but not all are as active as those in Indonesia.

We have some articles in Universe Today that are related to Mount Krakatoa. Here are two of them:

Mount Krakatoa articles brought to you by USGS. Here are the links:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:


How Long is a Light Year?

This visible-light image shows the galaxy dubbed UGC 3789, which is 160 million light-years from Earth. Credit: STScI

A light year is the distance light can travel in vacuum in one year’s time. This distance is equivalent to roughly 9,461,000,000,000 km or 5,878,000,000,000 miles. This is such a large distance. For comparison, consider the circumference of the Earth when measured at the equator: 40,075 km.

You can even throw in the center to center distance between the Earth and the Moon, 384,403 km, and that value would still pale in comparison to 1 light year. Pluto, at its farthest orbit distance from the Sun, is only about 7,400,000,000 km from the center of our Solar System.

Because of its great scale, the light year is one of the units of distance used for astronomical objects. For example, Andromeda Galaxy, which is the nearest spiral galaxy from the Milky Way, is approximately 2.5 million light years away. Alpha Centauri, the nearest star system from our own Solar System is only 4.37 light years away.

Imagine using miles or kilometers when describing the diameter of the Milky Way Galaxy, some 100,000 light years. Expressed in km or mi in expanded notation, that could occupy a lot of space on this page. Just look at the first paragraph, wherein we described 1 light year, to see what I mean. Of course, one may argue that we can still use scientific notation. But well, some people easily get daunted by the mere sight of exponents.

Although the light year has a more familiar ring to us, having perhaps heard about it quite often in sci-fi films or in magazines, it is not the most widely used unit of distance in astrometry, the branch of astronomy that deals with measurements and positions of celestial bodies. That assignment is given to the parsec. 1 parsec is approximately equal to 3.26 light years.

Another commonly used unit of distance is the astronomical unit or AU, wherein 1 AU is the average distance between the Earth and the Sun, and is roughly equivalent to 150,000,000 km. It is normally used when describing distances within the Milky Way.

Always remember that the ‘year’ we have been referring to here is not based in the internationally-accepted Gregorian Calendar. Instead, ‘year’ here refers to the Julian year. 1 Julian year is equivalent to 365.25 days or 31,557,600 seconds. The Julian calendar does not designate dates, hence is different from the Gregorian Calendar.

We have some related articles here in Universe Today. Here are the links:

Here are the links of two more articles from NASA:

Here are two episodes at Astronomy Cast that you might want to check out as well:

Source: NASA