Jerry Coffey, Author at Universe Today

August 24, 2010December 24, 2015 by Jerry Coffey

First Quarter Moon

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The first quarter moon is actually the third phase of the moon each cycle. In the Northern Hemisphere during this phase, the right hand 50% of the moon is visible during the afternoon and the early part of the night. In the Southern Hemisphere the left hand 50% of the moon can be seen. This lunar phase follows the new moon and the waxing crescent.

A lunar phase is the appearance of an illuminated portion of the moon as seen by an observer. For this article the observer is always on Earth. The lunar phases vary in a definite cycle as the moon orbits the Earth. The phases change based on the changing relative positions of the Earth, moon, and Sun. Half of the moon’s surface is always illuminated by the Sun, but the portion of the illuminated hemisphere that is visible to an observer can vary from 100%(full moon) to 0%(new moon). The only exception is during a lunar eclipse. The boundary between the light and dark portions of the moon is called the terminator.

There are 8 moon phases. These phases are: new moon, waxing crescent, first quarter moon, waxing gibbous, full moon, waning gibbous, last quarter moon, and waning crescent. The phases progress in the same manner each month. Earlier, it was mentioned that the lunar phase depends on the position of the Earth, moon, and Sun. During the new moon the Earth and Sun are on the opposite side of the moon. During the full moon the Earth and Sun are on the same sides of the Moon. The occasions when the Earth, Sun, and moon are in a straight line(new and full moon) are called syzygies.

When the moon passes between Earth and the Sun during a new moon, you might think that its shadow would cause a solar eclipse. On the other hand, you might think that during a full moon the Earth’s shadow would cause a lunar eclipse. The plane of the moon’s orbit around the Earth is tilted by about five degrees compared to the plane of Earth’s orbit around the Sun(called the ecliptic plane). This tilt prevents monthly eclipses. An eclipse can only occur when the moon is either new or full, but it also has to be positioned near the intersection of the Earth’s orbital plane about the Sun and the Moon’s orbit plane about the Earth, so there are between four and seven eclipses in a calendar year.

The first quarter moon is only one of eight lunar phases. You should research them all for a better understanding of the Earth/Moon system.

We have written many articles about the phases of the moon for Universe Today. Here’s an article about the 8 phases of the moon, and here’s an article about the moon phases for 2010.

If you’d like more info on the Moon, check out NASA’s Solar System Exploration Guide on the Moon, and here’s a link to NASA’s Lunar and Planetary Science page.

We’ve also recorded an entire episode of Astronomy Cast all about the Moon. Listen here, Episode 113: The Moon, Part 1.

References:
http://spaceplace.nasa.gov/en/kids/phonedrmarc/2004_march.shtml
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question3.html

June 16, 2010December 24, 2015 by Jerry Coffey

What Type of Planet is Mars?

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“What type of planet is Mars?” is a question that many readers ask. Mars is one of the four terrestrial planets. Mercury, Venus, and Earth are the other three. All of the terrestrial planets are made up of rock and metals. The remaining planets are classified as the outer gas giants.

All of the terrestrial planets have the same basic structure: core, mantle, crust; although each layer differs in thickness depending on the planet. Mercury has an average density of 5.43 g/cm³. Earth is the only planet more dense than Mercury. Mercury most likely has a liquid core that is mostly an iron-nickel alloy. The core accounts for as much as three-fourths of the planet’s radius. There are no numbers available for how thick the mantle and core are. Venus has a crust that extends 10-30 km below the surface. After that, the mantle reaches to a depth of some 3,000 km. The planetary core is a liquid iron-nickel alloy. Average planet density is 5.240 g/cm³.

Even though we live on Earth, not everyone is aware of its density and the depth of the various layers of our home world. The crust thickness averages 30 km for land masses and 5 kilometers for seabeds. The mantle extends on to an additional depth of 2,900 km. The core begins at a depth of around 5,100 km and is in two distinct parts: the outer core of liquid iron-nickel alloy and the inner core which is a solid alloy of iron-nickel. Average planet density is 5.520 g/cm³. The final terrestrial planet is Mars. Mars is roughly one-half the diameter of Earth, which leads scientists to speculate that the core has cooled and solidified. The depth of the crust and mantle are not known for sure, but the average planet density is 3.930 g/cm³. While there are only four terrestrial planets in our Solar System, here is a report on how NASA is trying to find more in other star systems.

Since we are talking specifically about Mars, we will talk about the composition of the planet’s surface material. There are hundreds of volcanoes on the surface of Mars. Several are regarded as the tallest mountains in the Solar System. Without plate tectonics, these volcanoes erupted for millions of years. Those massive eruptions explain why the entire surface is covered in basalt that is high in iron content. The iron content in the basalt has interacted with the Martian atmosphere and oxidized. The iron oxide explains why the entire Martian surface is coated in a reddish dust.

Answering ”what type of planet is Mars” took us on a little bit of a tangent. Hopefully, it is a tangent that will inspire you to find out more about the Red Planet.

We have written many articles about Mars for Universe Today. Here’s an article about the gravity on Mars, and here’s an article about the size of Mars.

If you’d like more info on Mars, check out Hubblesite’s News Releases about Mars, and here’s a link to the NASA Mars Exploration home page.

We’ve also recorded an episode of Astronomy Cast all about Mars. Listen here, Episode 52: Mars.

Source:
NASA

June 1, 2010December 24, 2015 by Jerry Coffey

Is Mars Bigger Than Earth?

Mars Compared to Earth. Image credit: NASA/JPL

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Occasionally, a reader asks ”is Mars bigger than Earth?”. No, Mars is about one half of the size of Earth. Below is a comparison chart so the you can get an idea of how much smaller Mars is than Earth

	Earth	Mars
Diameter	12,742 km	6,792 km
Surface Area	510,072,000 km²	144,798,500km²
Volume	1.08321×10¹²km³	1.6318×10¹¹km³
Mass	5.9736×10²⁴kg	6.4185×10²³kg

The diameter of Mars is about 53% of Earth’s and the surface area is close to 38% of Earth’s. When you put the numbers into a percentage, the surface area really seems small, but it is equal to all of the dry land on Earth. Scientists have found evidence of ancient liquid water on Mars. That means there were rivers and, possibly, oceans on the Red Planet. Imagine how small the available living space would have been then. Couple that with Mars having several of the tallest mountains and the deepest canyon in the Solar System and you realize exactly how little usable surface there really is on the planet.

Mars is the number one planet that scientists will mention when they are talking about terraforming. Transforming Mars would take centuries. Christopher McKay of NASA Ames Research Center believes that the key steps would be, first, releasing greenhouse gases to thicken the Martian atmosphere. This will help the planet retain heat from the Sun while filtering its radiation. The increased temperature would vaporize some of the carbon dioxide trapped in and on the planet’s surface. The CO₂ will increase the greenhouse effect, warming the planet even more. The temperature could increase by as much as 70 degrees on the Celsius scale. The increased temperature will melt the subsurface water ice on Mars, creating rain, rivers, and lakes. The water vapor from this release would also increase the atmospheric pressure to a level equivalent to what is seen at high elevations here on Earth. After all of these steps, the air would still be 90% carbon dioxide or higher. This is when plant life would be introduced to convert some of that carbon dioxide into oxygen. While humans could occupy the planet as the plants are being introduced, it would be several centuries before they would be able to remove their oxygen masks.

The answer to ”is Mars bigger than Earth” is no. The planet may be minute compared to Earth, but it is seen as a world full of potential by scientists. It is the most studied planet other than Earth, so be sure to look around for more information on the Red Planet.

We’ve written many articles about Mars for Universe Today. Here’s an article with some interesting facts about Mars, and here’s the distance from Earth to Mars.

If you’d like more info on Mars, check out Hubblesite’s News Releases about Mars, and here’s a link to the NASA Mars Exploration home page.

We’ve also recorded an episode of Astronomy Cast all about Mars. Listen here, Episode 52: Mars.

Sources:
http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
http://quest.nasa.gov/mars/background/terra2.html

March 26, 2010April 26, 2016 by Jerry Coffey

Earth Surface

[/caption]Most of the Earth surface, about 70%, is covered with water. The remaining 30% is made up of the seven continental landmasses. Underneath the water that fills the oceans, and the dirt and plants that cover the continents, the Earth’s surface layer is made of rock. This outer layer formed a hard, rocky crust as lava cooled about 4.5 billion years ago. This crust is broken into many large plates(tectonic plates) that move slowly relative to each other. The mountain ranges around the world formed when two plates collided and their edges are forced up. Many other surface features are the result of the movement of these tectonic plates. The plates move anywhere from 25 to 100 mm per year. About 250 million years ago most of the land was connected together.

The rocky layer under the soil of the Earth is called the crust. This comprises the continents and ocean basins. The crust has a variable thickness, being 35-70 km thick on the continents and 5-10 km thick in the ocean basins. The crust is composed mainly of alumino-silicates. The entire crust occupies just 1% of the Earth’s volume. The temperature of the crust increases as you go deeper into the Earth. It starts out cool, but can get up to 400 degrees C at the boundary between the crust and the mantle.

The tectonic plates are actually floating on the molten asthenosphere which is the lower mantle of the Earth. Earthquakes, volcanoes, mountains, and oceanic trench formation occur along plate boundaries. The plates are in constant motion. The reason that tectonic plates are able to move is the Earth’s lithosphere has a higher strength and lower density than the underlying asthenosphere. Their movement is dictated by heat dissipation from the Earth’s mantle. Lateral density variations in the mantle result in convection, which is transferred into plate motion through some combination of frictional drag, downward suction at the subduction zones, and variations in topography and density of the crust that result in differences in gravitational forces.

The Earth’s surface may seemed fixed and permanent to us, but underneath our feet there is constant motion and changes that we may not notice until there is an earthquake or a volcanic eruption. Here on Universe Today we have a great article with interesting facts about Earth. Astronomy Cast offers a good episode about plate tectonics. Here is the NASA webpage about Earth

References:
NASA Earth Observatory
NASA: Continents in Collision
NASA: Structure of the Earth

March 22, 2010December 24, 2015 by Jerry Coffey

Does The Sun Move?

The center of our Milky Way galaxy. Image credit: NASA.

[/caption]Does the Sun Move? What an interesting question. We mainly talk about everything in the solar system orbiting the Sun and celestial objects outside the solar system being in relation to the Sun. The answer to the question is : Yes. The Sun and the entire solar system orbits around the center of the Milky Way galaxy. The average velocity of the solar system is 828,000 km/hr. At that rate it will take about 230 million years to make one complete orbit around the galaxy.

You can check out these amazing books for more information about the Sun.

The Milky Way is a spiral galaxy. It is believed that it consists of a central bulge, 4 major arms, and several shorter arm segments. The Sun and the rest of our solar system is located near the Orion arm, between two major arms, Perseus and Sagittarius. The diameter of the Milky Way is about 100,000 light years and the Sun is located about 28,000 light-years from the Galactic Center. It has been suggested fairly recently that ours is actually a barred spiral galaxy. That means that instead of a bulge of gas and stars at the center, there is probably a bar of stars crossing the central bulge.

Everything in the known universe rotates on an axis and orbits something else in space. The Sun is no exception. Here is the NASA webpage about the sun’s movements through space. Astronomy Cast offers two good episodes: one is about the mysteries of the solar system and the other is about solar system movements.

February 22, 2010December 24, 2015 by Jerry Coffey

Atom Structure

[/caption]We know that atoms are parts of an element that can not naturally be broken down any further. What is the atom structure, though? The concept that atoms existed was first written about in ancient India in the 6th century B.C. The theory stayed just that, a theory, until the late 19th century. As microscopes and spectrometers developed, scientists were better able to develop their theories and finally observe the small scale structure of elements.

Atoms are made up of three particles: protons, electrons, and neutrons. Electrons are the smallest and lightest of the the three particles and they have a negative charge. The protons are much heavier and larger than electrons. Protons have a positive electrical charge. Neutrons are as large and massive as protons, but do not have an electrical charge at all. Every atom contains these particles in varying numbers. To understand exactly how small an atom is, you have to know that a single hydrogen atom is 5 x 10^-8mm in diameter. It would take at least 60 million hydrogen atoms to fill the space of any one of the letters on this page.

The simplest atom is that of hydrogen: 1 electron and one proton. In every stable, neutrally charged atom there is the exact same number of protons as electrons. These particles work together like two magnets with the opposite electrical charges attracting each other. The reason that they do not crash together is that the electron is constantly revolving around the nucleus(usually a proton/neutron combination, but hydrogen, uniquely, does not contain any neutrons). The centrifugal force of the electron keeps it in place at a constant distance from the nucleus. Actually, representing the electron as spinning around the nucleus is somewhat misleading. Electrons act like waves. That is how they are seen on a spectrometer. It is just easier to think of them as spinning around.

Atoms can have an electrical charge, positive or negative. This happens when an atom gains or loses electrons. The number of protons never changes in an atom. More electrons means a negative charge and fewer means a positive charge. Once an atom has an electrical charge it is called an ion. In an ion the atomic number and atomic mass do not change from the original. If an atom were to gain or lose neutrons it becomes an isotope. Remember the hydrogen atom I mentioned earlier. It did not have a neutron attached to its proton. If it gains a neutron it become an isotope called deuterium. Since the atomic mass is the total of the number of protons and neutrons, an isotope would have a different atomic mass, but the same atomic number as the original atom.

Alright, that is a very basic rendition of atom structure. The University of Colorado has an interesting website to help you understand more complex versions of atoms. Here on Universe Today we have a great article about the many theorized models of the atom. We discussed ions. Astronomy Cast offers a good episode about interstellar travel using ion propulsion.

Sources:
Wikipedia
GSU Hyperphysics

February 19, 2010December 24, 2015 by Jerry Coffey

Atom Model

[/caption]The most widely accepted atom model is that of Niels Bohr. Bohr’s model was first introduced in 1913. This model of the atom depicts a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus much like the planets travel around the Sun, but the electrostatic forces product attraction instead of gravity. The model’s key success was in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen. It is, basically, a modification of the Rutherford model used for quantum physics purposes.

The Bohr model was an improvement on older atomic models, but it too has been rendered obsolete by ongoing scientific research. Although considered to be obsolete, it is still taught as an introduction to quantum mechanics and in early secondary school science classes. Once students are advanced enough in their comprehension, they are introduced to the more accurate valence shell atom. At some time in the future this model of the atom may be proven to be too rigid in its scope.

The Bohr model built on the Rutherford theory. Rutherford proposed that electrons orbited the nucleus much like a planet around the Sun. The drawback to the theory was that based on his theory, electrons would be emitting(losing) their charge and spiral into the nucleus, making all atoms unstable. Bohr proposed several changes to that model: electrons can only travel in special orbits at a certain set of distances from the nucleus with specific energies, electrons do not continuously lose energy as they travel. They can only gain and lose energy by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation with a frequency determined by the energy difference of the levels according to the Planck relation, and that the frequency of the radiation emitted at an orbit is the reciprocal of the classical orbit period. This model is restricted in a few ways, but does allow for classical mechanics to explain many things while having an allowance for quantum rules.

The Bohr model begins to run into problems with heavier atoms. Other shortcomings of the model are:gives an incorrect value for the ground state orbital angular momentum, fails to explain much of the spectra of larger atoms, and the model also violates the uncertainty principle because it considers electrons to have known orbits and definite a radius. These two things can not be directly known at the same time.

Here is a good ink about the Bohr atom model. Here on Universe Today we have a couple of great articles on the topic: one is about the Bohr model and the other is about Dr. Bohr himself. Astronomy Cast offers a good episode about how molecules behave in space.

February 17, 2010December 24, 2015 by Jerry Coffey

Atom Diagram

[/caption]The image on the left is a basic atom diagram. This one shows the protons, neutrons, and electrons of a carbon atom. Each is in a group of six. That makes the atom very stable. There have been many atomic models over the years, but this type of model is now widely considered a sound basic version. Atomic diagrams were developed to explain the interaction of the elements of the Earth and space long before atoms could be observed. Nowadays, scientists can see particles that are smaller than an atom. These sub-atomic particles are the basis of particle physics.

Scientists have used atomic diagrams to explain the workings of the world for centuries. The ancient Greeks and, before them, the Chinese and Babylonians believed that there were forces that could not be seen that allowed certain metals to be combined and worked to man’s advantage. They did not know it, but that was simply heated metals exchanging subatomic particles to become a new metal.

Basic chemistry explains the atom best. It states that the fundamental building block of matter is the atom. An atom consists of three main parts: protons, neutrons, and electrons. Protons have a positive electrical charge. Neutrons have no electrical charge. Electrons have a negative electrical charge. Protons and neutrons are found together in what is called the nucleus of the atom. Electrons circle around nucleus. Chemical reactions involve interactions between the electrons of one atom and the electrons of another atom. Atoms which have different amounts of electrons and protons have a positive or negative electrical charge and are called ions. When atoms bond together, they can make larger building blocks of matter called molecules. If science did not have the atom modeled out, it would never have understood this exchange of electrons and we could still be stuck in the Dark Ages.

Earlier, I mentioned that there had been many atom models developed. Some of them are the Bohr model, the cubic model, the plum pudding model, the Saturnian model, and the Rutherford model.
Each of these models improved on the other and propelled science closer to a perfect atomic model. The Bohr and Rutherford models were developed for quantum mechanics and used for astronomical applications. As a matter of fact, an improvement on the Bohr model, called the Bohr-Summerfield model, is responsible for some of the many things we now know about quantum mechanics.

The atom diagram is under constant revision as science uncovers more information about sub-atomic particles. Follow this link to get information about the Bohr model and its enhancements. Here on Universe Today we have two great articles: one about the proton and the other about electrons. Astronomy Cast offers a good episode about matter from stars.

Sources:
Wikipedia
Chemistry Help

February 17, 2010December 24, 2015 by Jerry Coffey

Atom Definition

[/caption]The atom definition is: A unit of matter, the smallest unit of an element, having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by a system of electrons. The entire structure has an approximate diameter of 10^-8 centimeters and characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons. Essentially, it is the smallest possible part of an element that still remains the element.

Under normal circumstances an atom can be broken down into any smaller particles, but we humans, have devised ways to break the atom apart. That is the entire basis of the atom bomb, particle colliders, and quarks. It takes high speed, high energy smashing of particles to break an atom. A particle collider does that and helps us understand some of the theories in particle physics. The results of an atom bomb are widely known. Quarks are extremely small particles that do not exist alone. They must group to form the protons, electron, and neutrons normally found in a single atom of an element. They have only been found as a result of a particle collider and in theory.

An atom itself is made up of three tiny kinds of particles called subatomic particles: protons, neutrons, and electrons. The protons and the neutrons make up the center of the atom called the nucleus and the electrons fly around above the nucleus in a small cloud. The electrons carry a negative charge and the protons carry a positive charge. In a normal (neutral) atom the number of protons and the number of electrons are equal. Often, but not always, the number of neutrons is the same, too. The opposing forces(negative and positive) attract and repel each other in the right way so as to keep the atom together. The universe could be looked at as one large atom. Everything in space attracts and repels just right so as to keep the whole together.

One type of theoretical ion propulsion spacecraft would have to take advantage of this atomic attraction and repulsion to operate. It takes advantage of magnetism and electricity to push a ship through space. Electricity, generated by the ship’s solar panels, gives a positive electrical charge to atoms inside the chamber. They are pulled by magnetism towards the back of the ship and then pushed by magnetic repulsion out of the ship. This steady stream of atoms going out of the spacecraft gives it the thrust it needs to go forward through space. NASA has tested other types of ion propulsion and found them lacking.

Here is another atom definition. Here on Universe Today we have a great article about atoms. Astronomy Cast has a good question and answer episode about interstellar travel, including a NASA link about ion propulsion.

Source:
Wikipedia

February 7, 2010December 24, 2015 by Jerry Coffey

What Is The Atmosphere?

[/caption]What is the atmosphere? It is only the thing that keeps you from being burned to death every day, helps to bring the rain that our plants need to survive, no to mention it holds the oxygen that you need to breath. Essentially, the atmosphere is is a collection of gases that makes the Earth habitable.

The atmosphere consists of 78% nitrogen, 21% oxygen, 1% water vapor, and a minute amount of other trace gases like argon, and carbon monoxide. All of these gases combine to absorb ultraviolet radiation from the Sun and warm the planet’s surface through heat retention. The mass of the atmosphere is around 5×10¹⁸kg. 75% of the atmospheric mass is within 11 km of the surface. While the atmosphere becomes thinner the higher you go, there is no clear line demarcating the atmosphere from space; however, the Karman line , at 100 km, is often regarded as the boundary between atmosphere and outer space. The effects of reentry can be felt at 120 km.

Over the vast history of Earth there have been three different atmospheres or one that has evolved in three major stages. The first atmosphere came into being as a result of a major rainfall over the entire planet that caused the build up of a major ocean. The second atmosphere began to develop around 2.7 billion years ago. The presence oxygen began to appear apparently from being released by photosynthesizing algae. The third atmosphere came into play when the planet began to stretch its legs, so to speak. Plate tectonics began constantly rearranging the continents about 3.5 billion years ago and helped to shape long-term climate evolution by allowing the transfer of carbon dioxide to large land-based carbonate stores. Free oxygen did not exist until about 1.7 billion years ago and this can be seen with the development of the red beds and the end of the banded iron formations. This signifies a shift from a reducing atmosphere to an oxidizing atmosphere. Oxygen showed major ups and downs until reaching a steady state of more than 15%.

The Earth’s atmosphere performs a couple of cool optical tricks. The blue color of the sky is due to Rayleigh scattering which means as light moves through the atmosphere, most of the longer wavelengths pass straight through. Very little of the red, orange and yellow light is affected by the air; however, much of the shorter wavelength light(blue) is absorbed by the gas molecules. The absorbed blue light is then radiated in every direction. So, no matter where you look, you see the scattered blue light. The atmosphere is also responsible for the aurora borealis. Auroras are caused by the bombardment of solar electrons on oxygen and nitrogen atoms in the atmosphere. The electrons literally excite the oxygen and nitrogen atoms high in the atmosphere to create the beautiful light show we know as an aurora.

The atmosphere is divided into 5 major zones. The troposphere begins at the surface and extends to between 7 km at the poles and 17 km at the equator, with some variation due to weather. The stratosphere extends to about 51 km. The mesosphere extends to about 85 km. Most meteors burn up in this zone of the atmosphere. The thermosphere extends up to between 320 and 380 km. This is where the International Space Station orbits. The temperature here can rise to 1,500 °C. The exosphere is the last bastion of the atmosphere. Here the particles are so far apart that they can travel hundreds of km without colliding with one another. The exosphere is mainly composed of hydrogen and helium.

Check out the NASA page about the Earth’s atmosphere. Here on Universe Today we have a great article about an alternative idea about the atmosphere’s origin. Astronomy Cast offers a good episode about atmospheres around the Universe.