Posted on by Jerry Coffey

What Is Solar Energy

Morning Sun

What is solar energy? Solar energy is the radiant energy produced by the Sun. It is both light and heat. It, along with secondary solar-powered resources such as wind and wave power, account for the majority of the renewable energy on Earth.

The Earth receives 174 petawatts(PW) of solar radiation at the upper atmosphere. 30% of that is reflected back to space and the rest is absorbed by clouds, oceans and land masses. Land surfaces, oceans, and atmosphere absorb solar radiation, which increases their temperature. Warm air containing evaporated water from the oceans rises, causing convection. When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds and causes rain. The latent heat of water condensation increases convection, producing wind. Energy absorbed by the oceans and land masses keeps the surface at an average temperature of 14°C. Green plants convert solar energy into chemical energy through photosynthesis. Our food supply is completely dependent on solar energy. After plants die, they decay in the Earth, so solar energy can be said to provide the biomass that has created the fossil fuels that we are dependent on.

Humans harness solar energy in many different ways: space heating and cooling, the production of potable water by distillation, disinfection, lighting, hot water, and cooking. The applications for solar energy are only limited by human ingenuity. Solar technologies are characterized as either passive or active depending on the way the energy is captured, converted, and distributed. Active solar techniques use photovoltaic panels and solar thermal collectors to harness the energy. Passive techniques include orienting a building to the Sun, selecting materials with thermal mass properties, and using materials with light dispersing properties.

Our current dependence on fossil fuels is slowly being replaced by alternative energies. Some are fuels that may eventually become useless, but solar energy will never be obsolete, controlled by foreign powers, or run out. Even when the Sun uses up its hydrogen, it will produce useable energy until it explodes. The challenge facing humans is to capture that energy instead of taking the easiest way out by using fossil fuels.

We have written many articles about Solar Energy for Universe Today. Here’s an article about harvesting solar power from space, and here’s an article about the energy from the sun.

If you’d like more info on the Sun, check out NASA’s Solar System Exploration Guide on the Sun, and here’s a link to the SOHO mission homepage, which has the latest images from the Sun.

We’ve also recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.

Sources:
Wikipedia
Wise Geek

Posted on by Jerry Coffey

What Is Pangaea?

Continents might be necessary for life, especially complex life. This image shows super-continent Pangaea during the Permian period (300 - 250 million years ago). Credit: NAU Geology/Ron Blakey

So, you are curious about what is Pangaea? It was the supercontinent that existed 250 million years ago during the Paleozoic and Mesozoic eras. During the ensuing millenia, plate tectonics slowly moved each continent to its current position on the planet. Each continent is still slowly moving across the face of our world.

The breaking up and formation of supercontinents appears to have happened several times over Earth’s history with Pangaea being one among many. The next-to-last one, Pannotia, formed about 600 million years ago during the Proterozoic eon. Pannotia included large amounts of land near the poles and only a relatively small strip near the equator connecting the polar masses.

60 million years after its formation Pannotia broke up, giving rise to the continents of Laurentia, Baltica, and Gondwana. Laurentia would eventually become a large portion of North America, the microcontinent of Avalonia(a small portion of Gondwana) would become the northeastern United States, Nova Scotia, and England. All of these came together at the end of the Ordovician.

While this was happening, Gondwana drifted slowly towards the South Pole. These were the early steps in the formation of Pangaea. The next step was the collision of Gondwana with the other land mass. Southern Europe broke free of Gondwana. By late Silurian time, North and South China rifted away from Gondwana and started to head northward across the shrinking Proto-Tethys Ocean.

Movement continued slowly until the land masses drifted until their current positions. The list of oceans and microcontinents is too long to include in this article. We have many articles about this full process here on Universe Today. The evidence for Pangaea lies in the fossil records from the period. It includes the presence of similar and identical species on continents that are now great distances apart.

Additional evidence for Pangaea is found in the geology of adjacent continents, including matching geological trends between the eastern coast of South America and western Africa. The polar ice cap of the Carboniferous Period covered the southern end of Pangaea. Glacial deposits of the same age and structure are found on many separate continents which would have been together in the continent of Pangaea.

We know that the existence of supercontinents has been proven. We know that they have existed at different times in the Earth’s history. Also, we know that the tectonic plates are still moving. Is it possible that there will be another supercontinent someday in the distant future.

We have written many articles about Pangaea for Universe Today. Here’s an article about the Continental Drift Theory, and here’s an article about the continental plates.

If you’d like more info on Pangaea, check out the Pangaea Interactive Map Game. And here’s a link to NASA’s Continents in Collision: Pangaea Ultima.

We’ve also recorded an episode of Astronomy Cast all about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.

Sources:
http://en.wikipedia.org/wiki/Pangaea
http://pubs.usgs.gov/gip/dynamic/historical.html
http://library.thinkquest.org/17701/high/pangaea/

Posted on by Jerry Coffey

What Is Mechanical Energy

Millennium Force roller coaster Credit: Cedar Point
Millennium Force roller coaster Credit: Cedar Point

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The straight forward answer to ‘what is mechanical energy’ is that it is the sum of energy in a mechanical system. This energy includes both kinetic energy(energy of motion) and potential energy(stored energy).

Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position. A few examples are: a moving car possesses mechanical energy due to its motion(kinetic energy) and a barbell lifted high above a weightlifter’s head possesses mechanical energy due to its vertical position above the ground(potential energy).

Kinetic energy is the energy of motion. An object that has motion, vertical or horizontal motion, has kinetic energy. There are many forms of kinetic energy: vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another).

Potential energy is the energy stored in a body or in a system due to its position in a force field or its configuration. The standard unit of measure for energy and work is the joule. The term “potential energy” has been used since the 19th century.

Because of the different components of mechanical energy, it exists in every system in the universe. From a baseball being thrown to a brick falling off of a ledge, mechanical energy surrounds us. Defining what is mechanical energy is easy, but finding examples of it are even easier.

We have written many articles about mechanical energy for Universe Today. Here’s an article about how generators work, and here’s an article about what is energy.

If you’d like more info on Mechanical Energy, check out a Discussion on Energy, and here’s a link to an article about Momentum.

We’ve also recorded an entire episode of Astronomy Cast all about Gravity. Listen here, Episode 102: Gravity.

Posted on by Jerry Coffey

What Is Lithosphere

Inner Earth
Inner Earth

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Every rocky planet has a lithosphere, but what is lithosphere? It is the rigid outermost shell of a rocky planet. Here on Earth the lithosphere contains the crust and upper mantle. The Earth has two types of lithosphere: oceanic and continental. The lithosphere is broken up into tectonic plates.

Oceanic lithosphere consists mainly of mafic(rich in magnesium and iron) crust and ultramafic(over 90% mafic) mantle and is denser than continental lithosphere. It thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle. It was less dense than the asthenosphere for tens of millions of years, but after this becomes increasingly denser. The gravitational instability of mature oceanic lithosphere has the effect that when tectonic plates come together, oceanic lithosphere invariably sinks underneath the overriding lithosphere. New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones, so oceanic lithosphere is much younger than its continental counterpart. The oldest oceanic lithosphere is about 170 million years old compared to parts of the continental lithosphere which are billions of years old.

The continental lithosphere is also called the continental crust. It is the layer of igneous, sedimentary rock that forms the continents and the continental shelves. This layer consists mostly of granitic rock. Continental crust is also less dense than oceanic crust although it is considerably thicker(25 to 70 km versus 7-10 km). About 40% of the Earth’s surface is now covered by continental crust, but continental crust makes up about 70% of the volume of Earth’s crust. Most scientists believe that there was no continental crust originally on the Earth, but the continental crust ultimately derived from the fractional differentiation of oceanic crust over the eons. This process was primarily a result of volcanism and subduction.

We may not walk directly the lithosphere, but it shapes every topographical feature the we see. The movement of the tectonic plates has presented many different shapes for our planet over the eons and will continue to change our geography until our planet ceases to exist.

We have written many articles about the lithosphere for Universe Today. Here’s an article about the lithosphere, and here’s an article about the tectonic plates.

If you’d like more info on the Earth’s lithosphere, check out NASA’s Solar System Exploration Guide on Earth. 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.

Posted on by Jerry Coffey

What Is Light Energy

Lighting Up the Night
Lighting Up the Night

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Just asking ‘what is light energy’ opens you up to a flood of other questions trying to narrow down the context that you are asking the question in. In photometry, luminous energy is the perceived energy of light. It can also be defined as the electromagnetic radiation of visible light. Since light itself is energy, then another definition is relevant: light is nature’s way of transferring energy through space.

The speed of light is about 300,000 km/s. To put that in perspective, when you watch the sun set, it has actually been 10 minutes since that light left the Sun. Light energy is measured with two main sets of units: radiometry measures light power at all wavelengths and photometry measures light with wavelength weighted with respect to a standardized model of human brightness perception. Photometry is useful when measuring light intended for human use. The photometry units are different from most units because they take into account how the human eye responds to light. Based on this, two light sources which produce the same intensity of visible light do not necessarily appear equally bright.

Light exerts a physical pressure on objects in its path. This is explained by the particle nature of light in which photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by the speed of light. The effect of light pressure is negligible for everyday objects. For example, you can lift a coin with laser pointers, but it would take 1 billion of them to do it. Light pressure can cause asteroids to spin faster by working on them like wind pushing a windmill. That is why some scientist are researching solar sails to propel intersteller flight.

Light is all around us. It has the ability to tan or burn our skins, it can be harnessed to melt metals, or heat our food. Light energy posed a huge challenge for scientist up to the 1950’s. Hopefully, in the future, we will be able to use light energy and solar wind to travel among the stars.

We have written many articles about light energy for Universe Today. Here’s an article about the prescription for light pollution, and here’s an article about where visible light come from.

If you’d like more info on Light Energy, check out NASA’s Page on Atoms and Light Energy. And here’s a link to an article about How Photovoltaics Work.

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

Sources:
Johns Hopkins University
Wikipedia

Posted on by Jerry Coffey

What Is Atomic Mass

Faraday's Constant

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The answer to ‘what is atomic mass’ is this: the total mass of the protons, neutrons, and electrons in a single atom when it is at rest. This is not to be associated or mistaken for atomic weight. Atomic mass is measured by mass spectrometry. You can figure the molecular mass of an compound by adding the atomic mass of its atoms.

Until the 1960’s chemists and physicists used different atomic mass scales. Chemists used a scale that showed that the natural mixture of oxygen isotopes had an atomic mass 16. Physicists assigned 16 to the atomic mass of the most common oxygen isotope. Problems and inconsistencies arose because oxygen 17 and oxygen 18 are also present in natural oxygen. This created two different tables of atomic mass. A unified scale based on carbon-12 is used to meet the physicists’ need to base the scale on a pure isotope and is numerically close to the chemists’ scale.

Standard atomic weight is the average relative atomic mass of an element in the crust of Earth and its atmosphere. This is what is included in standard periodic tables. Atomic weight is being phased out slowly and being replaced by relative atomic mass. This shift in wording dates back to the 1960’s. It has been the source of much debate largely surrounding the adoption of the unified atomic mass unit and the realization that ‘weight’ can be an inappropriate term. Atomic weight is different from atomic mass in that it refers to the most abundant isotope in an element and atomic mass directly addresses a single atom or isotope.

Atomic mass and standard atomic weight can be so close, in elements with a single dominant isotope, that there is little difference when considering bulk calculations. Large variations can occur in elements with many common isotopes. Both have their place in science today. With advances in our knowledge, even these terms may become obsolete in the future.

We have written many articles about atomic mass for Universe Today. Here’s an article about the atomic nucleus, and here’s an article about the atomic models.

If you’d like more info on the Atomic Mass, check out NASA’s Article on Analyzing Tiny Samples, and here’s a link to NASA’s Article about Atoms, Elements, and Isotopes.

We’ve also recorded an entire episode of Astronomy Cast all about the Atom. Listen here, Episode 164: Inside the Atom.

Sources:
Wikipedia
Windows to Universe
NDT Resource Center

Posted on by Jerry Coffey

What Is Atmospheric Pressure

Thermosphere
The Moon viewed from Earth's thermosphere. Credit: NASA

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Just answering the question ‘what is atmospheric pressure?’ is not enough to give a full understanding of its importance. By definition atmospheric pressure is ‘force per unit area exerted against a surface by the weight of air above that surface’. Atmospheric pressure is closely related to the hydrostatic pressure caused by the weight of air above the measurement point. The term standard atmosphere is used to express the pressure in a system(hydraulics and pneumatics) and is equal to 101.325 kPa. Other equivalent units are 760 mmHg and 1013.25 millibars.

Mean sea level pressure (MSLP) is the pressure at sea level. This is the pressure normally given in weather reports. When home barometers are set to match local weather reports, they will measure pressure reduced to sea level, not your local atmospheric pressure. The reduction to sea level means that the normal range of fluctuations in pressure are the same for everyone.

Atmospheric pressure is important in altimeter settings for flight. A altimeter can be set for QNH or QFE. Both are a method of reducing atmospheric pressure to sea level, but they differ slightly. QNH will get the altimeter to show elevation at the airfield and altitude above the air field. QFE will set the altimeter to read zero for reference when at a particular airfield. QNH is transmitted around the world in millibars, except in the United States and Canada . These two countries use inches (or hundredths of an inch) of mercury.

Atmospheric pressure is often measured with a mercury barometer; however, since mercury is not a substance that humans commonly come in contact with, water often provides a more intuitive way to visualize the pressure of one atmosphere. One atmosphere is the amount of pressure that can lift water approximately 10.3m. A diver who is 10.3m underwater experiences a pressure of about 2 atmospheres (1of air plus 1of water). Low pressures like natural gas lines can be expressed in inches of water(w.c). A typical home gas appliance is rated for a maximum of 14 w.c.(about 0.034 atmosphere).

You can see that understanding ‘what is atmospheric pressure’ is just the tip of the iceberg. Once you have the definition in mind, it really comes together when you see the wide variety of applications.

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

If you’d like more info on the Atmospheric Pressure, check out NASA’s Discussion Video on Atmospheric Pressure, and here’s a link to How Atmospheric Pressure Affects the Weather?

We’ve also recorded an entire episode of Astronomy Cast all about the Atmospheric Pressure. Listen here, Episode 151: Atmospheres.

Posted on by Jerry Coffey

What Is An Electron

Faraday's Constant

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What is an electron? Easily put, an electron is a subatomic particle that carries a negative electric charge. There are no known components, so it is believed to be an elementary particle(basic building block of the universe). The mass of an electron is 1/1836 of its proton. Electrons have an antiparticle called a positron. Positrons are identical to electrons except that all of its properties are the exact opposite. When electrons and positrons collide, they can be destroyed and will produce a pair (or more) of gamma ray photons. Electrons have gravitational, electromagnetic, and weak interactions.

In 1913, Niels Bohr postulated that electrons resided in quantized energy states, with the energy determined by the spin(angular momentum)of the electron’s orbits and that the electrons could move between these orbits by the emission or absorption of photons. These orbits explained the spectral lines of the hydrogen atom. The Bohr model failed to account for the relative intensities of the spectral lines and it was unsuccessful in explaining the spectra of more complex atom. Gilbert Lewis proposed in 1916 that a ‘covalent bond’ between two atoms is maintained by a pair of shared electrons. In 1919, Irving Langmuir improved on Lewis’ static model and suggested that all electrons were distributed in successive “concentric(nearly) spherical shells, all of equal thickness”. The shells were divided into a number of cells containing one pair of electrons. This model was able to qualitatively explain the chemical properties of all elements in the periodic table.

The invariant mass of an electron is 9.109×10-31 or 5.489×10-4 of the atomic mass unit. According to Einstein’s principle of mass-energy equivalence, this mass corresponds to a rest energy of .511MeV. Electrons have an electric charge of -1.602×10 coulomb. This a standard unit of charge for subatomic particles. The electron charge is identical to the charge of a proton. In addition to spin, the electron has an intrinsic magnetic moment along its spin axis. It is approximately equal to one Bohr magneton. The orientation of the spin with respect to the momentum of the electron defines the property of elementary particles known as helicity. Observing a single electron shows the upper limit of the particle’s radius is 10-22 meters. Some elementary particles decay into less massive particles. But an electron is thought to be stable on the grounds that it is the least massive particle with non-zero electric charge.

Understanding what is an electron is to begin to understand the basic building blocks of the universe. A very elementary understanding, but a building block to great scientific thought.

We have written many articles about the electron for Universe Today. Here’s an article about the Electron Cloud Model, and here’s an article about the charge of electron.

If you’d like more info on the Electron, check out the History of the Electron Page, and here’s a link to the article about Killer Electrons.

We’ve also recorded an entire episode of Astronomy Cast all about the Composition of the Atom. Listen here, Episode 164: Inside the Atom.

Posted on by Jerry Coffey

What Is A Continent

Map of Earth
Map of Earth

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You know that there are 7 continents(6 if you were taught geography in Europe) right now, but do you really know the definition of what is a continent? There are many different, and confusing definitions of what a continent is. The most widely accepted one says that a continent is defined as a large, continuous, discrete mass of land, ideally separated by an expanse of water. This definition somewhat confuses things. Many of the current continents are not discrete landmasses separated by water. The word large leads to arbitrary classification: Greenland, with a surface area of 2,166,086 km2 is considered the world’s largest island, but Australia with a land mass of 7,617,930 km2 is a continent. The qualification that each be a continuous landmass is disregarded because of the inclusion of the continental shelf and oceanic islands and is contradicted by classifying North and South America and Asia and Africa as continents, without a natural separation by water. This idea continues if the land mass of Europe and Asia is considered as two continents. Also, the Earth’s major landmasses are surrounded by one, continuous World ocean that has been divided into a number of principal ‘oceans’ by the land masses themselves and various other geographic criteria.

The number of continents has changed throughout the evolution of the Earth. Plate tectonics and continental drift have forced changes on continental composition. The planet began with one single land mass(the Mesezoic Era). This continent was not suddenly there. It was the result of partially solidified magma being smashed together by plate tectonics and continental drift. Those forces remain at work today.

To further confuse things, different parts of the world teach different versions of the continents. The seven-continent model is usually taught in China and most English speaking countries. A six continent model combining Europe and Asia is preferred by the geographic community, the former parts of the USSR, and Japan. Another six continent model combining North and South America is taught in Latin America and most of Europe.
The answer to ‘what is a continent’ is more by convention than strict definition. Hopefully, this will help to clear some of the confusion that you had before you started reading this article.

We have written many articles about the continents for Universe Today. Here’s an article about the biggest continent, and here’s an article about the continental drift theory.

If you’d like more info on Earth’s continents, check out NASA’s Solar System Exploration Guide on Earth. 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.

Source: Wikipedia

Posted on by Jerry Coffey

Is There Life On Other Planets

Temperature of Mars
What is the Temperature of Mars? Image credit: NASA/JPL

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Is there life on other planets? That has been a question raised from the early beginnings of science fiction. The notion was scoffed at as pure mind play for dreamers and the occasional grifter selling rides to the Moon. At least it was until we were able to reach into space and discover new facts and gather new intel.

The possibility of life on Mars(outside sci-fi books) had been proposed as early as the 1950’s, but there was no real way to prove or disprove the theory until the launch of Mariner 4 in 1965. The spacecraft was able to return the first photographs of the planet’s surface. The news was all bad for those who had hoped for signs of life on the planet. The surface was too extreme and desolate for any type of known life form. The Voyager probes found radiolabeled carbon dioxide, but no organic molecules. Those results give mixed signals and are inconclusive at best. The results have been used to support the possibility of a microorganism named Gillevinia straata.

The Phoenix lander touched down on the Martian surface in May of 2008. The lander dug a trench on the area of the northern pole. No bacteria was found but the samples did contain bound water and carbon dioxide. The most positive evidence of life in the Martian past are meteorites from the planet. 34 exist and 3 show signs of microscopic fossilized bacteria.

Another viable possibility for life on other planets would be those similar to Gliese 581c. These planets are within the habitable zone(for human life) of their main sequence star. These planets appear to have a temperature that would allow liquid water and atmosphere’s that seem spectroscopically close to Earth’s. The information that is needed would detail the greenhouse effect on these planets. If that was available, we would be able to determine suitability for human life.

All of our efforts to answer the question ‘Is there life on other planets?’ are based on finding life that is similar to that on Earth. That is a typically arrogant line of research. Where is it written that the Earth type of life form is pervasive?

We have written many articles about the possibility of life on other planets for Universe Today. Here’s an article about the life on other planets, and here’s an article about life on Mars.

If you’d like more info on the search for life on other planets, check out the NASA Astrobiology Institute Homepage, and here’s a link to NASA Planet Quest: Finding Life.

We’ve also recorded an entire episode of Astronomy Cast all about the Future of Astronomy. Listen here, Episode 188: The Future of Astronomy.