Guide to Space Archives

October 24, 2010December 24, 2015 by Matt Williams

Cosmology

Planck Time — The Universe. So far, no duplicates found@

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Ever wonder why we are here, how and why the universe that we inhabit came to be, and what our place is in it? If so, than in addition to philosophy, religion, and esotericism, you might be interested in the field of Cosmology. This is, in the strictest sense, the study of the universe in its totality, as it is today, and what humanity’s place is in it. Although a relatively recent invention from a purely scientific point of view, it has a long history which embraces several fields over the course of many thousand years and countless cultures.

In western science, the earliest recorded examples of cosmology are to be found in ancient Babylon (circa 1900 – 1200 BCE), and India (1500 -1200 BCE). In the former case, the creation myth recovered in the EnûmaEliš held that the world existed in a “plurality of heavens and earths” that were round in shape and revolved around the “cult place of the deity”. This account bears a strong resemblance to the Biblical account of creation as found in Genesis. In the latter case, Brahman priests espoused a theory in which the universe was timeless, cycling between expansion and total collapse, and coexisted with an infinite number of other universes, mirroring modern cosmology.

The next great contribution came from the Greeks and Arabs. The Greeks were the first to stumble onto the concept of a universe that was made up of two elements: tiny seeds (known as atoms) and void. They also suggested, and gravitated between, both a geocentric and heliocentric model. The Arabs further elaborated on this while in Europe, scholars stuck with a model that was a combination of classical theory and Biblical canon, reflecting the state of knowledge in medieval Europe. This remained in effect until Copernicus and Galileo came onto the scene, reintroducing the west to a heliocentric universe while scientists like Kepler and Sir Isaac Newton refined it with their discovery of elliptical orbits and gravity.

The 20th century was a boon for cosmology. Beginning with Einstein, scientists now believed in an infinitely expanding universe based on the rules of relativity. Edwin Hubble then demonstrated the scale of the universe by proving that “spiral nebulae” observed in the night sky were actually other galaxies. By showing how they were red-shifted, he also demonstrated that they were moving away, proving that the universe really was expanding. This in turn, led to the Big Bang theory which put a starting point to the universe and a possible end (echoes of the Braham expansion/collapse model).

Today, the field of cosmology is thriving thanks to ongoing research, debate and continuous discovery, thanks in no small part to ongoing efforts to explore the known universe.

We have written many articles about cosmology for Universe Today. Here’s an article about the galaxy, and here are some interesting facts about stars.

If you’d like more info on cosmology, the best place to look is NASA’s Official Website. I also recommend you check out the website for the Hubble Space Telescope.

We’ve recorded many episodes of Astronomy Cast, including one about Hubble. Check it out, Episode 88: The Hubble Space Telescope.

Sources:
http://en.wikipedia.org/wiki/Cosmology#cite_note-5
http://en.wikipedia.org/wiki/En%C3%BBma_Eli%C5%A1
http://en.wikipedia.org/wiki/Timeline_of_cosmology
http://www.newscientist.com/article/dn9988-instant-expert-cosmology.html
http://en.wikipedia.org/wiki/Geocentric_model
http://en.wikipedia.org/wiki/Heliocentrism
http://en.wikipedia.org/wiki/Red_shift

October 20, 2010December 24, 2015 by Matt Williams

First Law of Thermodynamics

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Ever wonder how heat really works? Well, not too long ago, scientists, looking to make their steam engines more efficient, sought to do just that. Their efforts to understand the interrelationship between energy conversion, heat and mechanical work (and subsequently the larger variables of temperature, volume and pressure) came to be known as thermodynamics, taken from the Greek word “thermo” (meaning “heat”) and “dynamis” (meaning force). Like most fields of scientific study, thermodynamics is governed by a series of laws that were realized thanks to ongoing observations and experiments. The first law of thermodynamics, arguably the most important, is an expression of the principle of conservation of energy.

Consistent with this principle, the first law expresses that energy can be transformed (i.e. changed from one form to another), but cannot be created or destroyed. It is usually formulated by stating that the change in the internal energy (ie. the total energy) contained within a system is equal to the amount of heat supplied to that system, minus the amount of work performed by the system on its surroundings. Work and heat are due to processes which add or subtract energy, while internal energy is a particular form of energy associated with the system – a property of the system, whereas work done and heat supplied are not. A significant result of this distinction is that a given internal energy change can be achieved by many combinations of heat and work.

This law was first expressed by Rudolf Clausius in 1850 when he said: “There is a state function E, called ‘energy’, whose differential equals the work exchanged with the surroundings during an adiabatic process.” However, it was Germain Hess (via Hess’s Law), and later by Julius Robert von Mayer who first formulated the law, however informally. It can be expressed through the simple equation E2 – E1 = Q – W, whereas E represents the change in internal energy, Q represents the heat transfer, and W, the work done. Another common expression of this law, found in science textbooks, is ?U=Q+W, where ? represents change and U, heat.

An important concept in thermodynamics is the “thermodynamic system”, a precisely defined region of the universe under study. Everything in the universe except the system is known as the surroundings, and is separated from the system by a boundary which may be notional or real, but which by convention delimits a finite volume. Exchanges of work, heat, or matter between the system and the surroundings take place across this boundary. Thermodynamics deals only with the large scale response of a system which we can observe and measure in experiments (such as steam engines, for which the study was first developed).

We have written many articles about the First Law of Thermodynamics for Universe Today. Here’s an article about entropy, and here’s an article about Hooke’s Law.

If you’d like more info on the First Law of Thermodynamics, check out NASA’s Glenn Research Center, and here’s a link to Hyperphysics.

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

Sources:
http://en.wikipedia.org/wiki/First_law_of_thermodynamics
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/firlaw.html
http://en.wikipedia.org/wiki/Internal_energy
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo1.html
http://en.wikipedia.org/wiki/Thermodynamics
http://en.wikipedia.org/wiki/Laws_of_thermodynamics

October 20, 2010December 11, 2016 by Matt Williams

What are Earthquake Fault Lines?

False-color composite image of the Port-au-Prince, Haiti region, taken Jan. 27, 2010 by NASA’s UAVSAR airborne radar. The city is denoted by the yellow arrow; the black arrow points to the fault responsible for the Jan. 12 earthquake. Image credit: NASA

Every so often, in different regions of the world, the Earth feels the need to release energy in the form of seismic waves. These waves cause a great deal of hazards as the energy is transferred through the tectonic plates and into the Earth’s crust. For those living in an area directly above where two tectonic plates meet, the experience can be quite harrowing!

This area is known as a fault, or a fracture or discontinuity in a volume of rock, across which there is significant displacement. Along the line where the Earth and the fault plane meet, is what is known as a fault line. Understanding where they lie is crucial to our understanding of Earth’s geology, not to mention earthquake preparedness programs.

Definition:

In geology, a fault is a fracture or discontinuity in the planet’s surface, along which movement and displacement takes place. On Earth, they are the result of activity with plate tectonics, the largest of which takes place at the plate boundaries. Energy released by the rapid movement on active faults is what causes most earthquakes in the world today.

The Earth's Tectonic Plates. Credit: msnucleus.org — The Earth’s Tectonic Plates. Credit: msnucleus.org

Since faults do not usually consist of a single, clean fracture, geologists use the term “fault zone” when referring to the area where complex deformation is associated with the fault plane. The two sides of a non-vertical fault are known as the “hanging wall” and “footwall”.

By definition, the hanging wall occurs above the fault and the footwall occurs below the fault. This terminology comes from mining. Basically, when working a tabular ore body, the miner stood with the footwall under his feet and with the hanging wall hanging above him. This terminology has endured for geological engineers and surveyors.

Mechanisms:

The composition of Earth’s tectonic plates means that they cannot glide past each other easily along fault lines, and instead produce incredible amounts of friction. On occasion, the movement stops, causing stress to build up in rocks until it reaches a threshold. At this point, the accumulated stress is released along the fault line in the form of an earthquake.

When it comes to fault lines and the role they have in earthquakes, three important factors come into play. These are known as the “slip”, “heave” and “throw”. Slip refers to the relative movement of geological features present on either side of the fault plane; in other words, the relative motion of the rock on each side of the fault with respect to the other side.

Transform Plate Boundary — *Tectonic Plate Boundaries. Credit:*

Heave refers to the measurement of the horizontal/vertical separation, while throw is used to measure the horizontal separation. Slip is the most important characteristic, in that it helps geologists to classify faults.

Types of Faults:

There are three categories or fault types. The first is what is known as a “dip-slip fault”, where the relative movement (or slip) is almost vertical. A perfect example of this is the San Andreas fault, which was responsible for the massive 1906 San Francisco Earthquake.

Second, there are “strike-slip faults”, in which case the slip is approximately horizontal. These are generally found in mid-ocean ridges, such as the Mid-Atlantic Ridge – a 16,000 km long submerged mountain chain occupying the center of the Atlantic Ocean.

Lastly, there are oblique-slip faults which are a combination of the previous two, where both vertical and horizontal slips occur. Nearly all faults will have some component of both dip-slip and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant.

*Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com*

Impacts of Fault Lines:

For people living in active fault zones, earthquakes are a regular hazard and can play havoc with infrastructure, and can lead to injuries and death. As such, structural engineers must ensure that safeguards are taken when building along fault zones, and factor in the level of fault activity in the region.

This is especially true when building crucial infrastructure, such as pipelines, power plants, damns, hospitals and schools. In coastal regions, engineers must also address whether tectonic activity can lead to tsunami hazards.

For example, in California, new construction is prohibited on or near faults that have been active since the Holocene epoch (the last 11,700 years) or even the Pleistocene epoch (in the past 2.6 million years). Similar safeguards play a role in new construction projects in locations along the Pacific Rim of fire, where many urban centers exist (particularly in Japan).

Various techniques are used to gauge when the last time fault activity took place, such as studying soil and mineral samples, organic and radiocarbon dating.

We have written many articles about the earthquake for Universe Today. Here’s What Causes Earthquakes?, What is an Earthquake?, Plate Boundaries, Famous Earthquakes, and What is the Pacific Ring of Fire?

If you’d like more info on earthquakes, check out the U.S. Geological Survey Website. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded related episodes of Astronomy Cast about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.

Sources:

October 17, 2010April 26, 2016 by Matt Williams

Destructive Interference

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Sound travels in waves, which function much the same as ocean waves do. One wave cycle is a complete wave, consisting of both the up half (crest) and down half (trough). Waves also have a certain amplitude which is the measure of how strong the wave is; the higher the amplitude, the higher the crests and deeper the troughs. Waves don’t usually reflect when they strike other waves. Instead, they combine. If the amplitudes of two waves have the same sign (either both positive or both negative), they will add together to form a wave with a larger amplitude. This is called constructive interference. If the two amplitudes have opposite signs, they will subtract to form a combined wave with lower amplitude. This is what is called Destructive Interference, which is a subfield of the larger study in physics known as wave propagation.

An interesting example of this is the loudspeaker. When music is played on the loudspeaker, sound waves emanate from the front and back of the speaker. Since they are out of phase, they diffract into the entire region around the speaker. The two waves interfere destructively and cancel each other, particularly at very low frequencies. But when the speaker is held up behind baffle, which in this case consists of a wooden sheet with a circular hole cut in it, the sounds can no longer diffract and mix while they are out of phase, and as a consequence the intensity increases enormously. This is why loudspeakers are often mounted in boxes, so that the sound from the back cannot interfere with the sound from the front.

Scientists and engineers use destructive interference for a number of applications to levels reduce of ambient sound and noise. One example of this is the modern electronic automobile muffler. This device senses the sound propagating down the exhaust pipe and creates a matching sound with opposite phase. These two sounds interfere destructively, muffling the noise of the engine. Another example is in industrial noise control. This involves sensing the ambient sound in a workplace, electronically reproducing a sound with the opposite phase, and then introducing that sound into the environment so that it interferes destructively with the ambient sound to reduce the overall sound level.

For a hands-on demonstration of how destructive interference works, click on this link.

We have written many articles about destructive interference for Universe Today. Here’s an article about constructive waves, and here’s an article about the Casimir Effect.

If you’d like more info on destructive interference, check out Running Interference, and here’s a link to NASA Science page about Interference.

We’ve also recorded an entire episode of Astronomy Cast all about the Wave Particle Duality. Listen here, Episode 83: Wave Particle Duality.

Sources:
http://en.wikipedia.org/wiki/Interference_%28wave_propagation%29
http://en.wikipedia.org/wiki/Loudspeaker_enclosure
http://en.wikipedia.org/wiki/Sound_baffle
http://www.windows2universe.org/earth/Atmosphere/tornado/beat.html
http://library.thinkquest.org/19537/Physics5.html
http://zonalandeducation.com/mstm/physics/waves/interference/destructiveInterference/InterferenceExplanation3.html

October 17, 2010April 26, 2016 by Matt Williams

Desertification

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The Sahelian-drought, that began in 1968 and took place in sub-Saharan Africa, was responsible for the deaths of between 100,000 to 250,000 people, the displacement of millions more and the collapse of the agricultural base for several African nations. In North America during the 1930’s, parts of the Canadian Prairies and the “Great Planes” in the US turned to dust as a result of drought and poor farming practices. This “Dust Bowl” forced countless farmers to abandon their farms and way of life and made a fragile economic situation even worse. In both cases, a combination of factors led to the process known as Desertification. This is defined as the persistent degradation of dryland ecosystems due to natural and man-made factors, and it is a complex process.

Desertification can be caused by climactic variances, but the chief cause is human activity. It is principally caused by overgrazing, overdrafting of groundwater and diversion of water from rivers for human consumption and industrial use. Add to that overcultivation of land which exhausts the soil and deforestation which removes trees that anchor the soil to the land, and you have a very serious problem! Today, desertification is devouring more than 20,000 square miles of land worldwide every year. In North America, 74% of the land in North America is affected by desertification while in the Mediterranean, water shortages and poor harvests during the droughts of the early 1990s exposed the acute vulnerability of the Mediterranean region to climatic extremes.

In Africa, this presents a serious problem where more than 2.4 million acres of land, which constitutes 73% of its drylands, are affected by desertification. Increased population and livestock pressure on marginal lands have accelerated this problem. In some areas, where nomads still roam, forced migration causes these people to move to new areas and place stress on new lands which are less arid and hence more vulnerable to overgrazing and drought. Given the existing problems of overpopulation, starvation, and the fact that imports are not a readily available option, this phenomenon is likely to lead to greater waves of starvation and displacement in the near future.

Against this backdrop, the prospect of a major climate change brought about by human activities is a source of growing concern. Increased global mean temperatures will mean more droughts, higher rates of erosion, and a diminished supply land water; which will seriously undermine efforts to combat drought and keep the world’s deserts from spreading further. The effects will be felt all over the world but will hit the equatorial regions of the world especially hard, regions like Sub-Saharan Africa, the Mediterranean, Central and South America, where food shortages are already a problem and are having serious social, economic and political consequences.

We have written many articles about desertification for Universe Today. Here’s an article about the largest desert on Earth, and here’s an article about the Atacama Desert.

If you’d like more info on desertification, check out Visible Earth Homepage. 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.

Sources:
http://en.wikipedia.org/wiki/Desertification
http://www.greenfacts.org/en/desertification/index.htm
http://archive.greenpeace.org/climate/science/reports/desertification.html
http://pubs.usgs.gov/gip/deserts/desertification/
http://didyouknow.org/deserts/
http://en.wikipedia.org/wiki/Overdrafting

October 15, 2010December 19, 2016 by Tega Jessa

Why is the Earth Tilted?

Winter Solstice — Earth as viewed from the cabin of the Apollo 11 spacecraft. Credit: NASA

Have you ever wondered why the Earth is tilted instead of just perpendicular with its plane of orbit? Scientists have taken a crack at answering that question. The main consensus is that it has to do with Earth’s formation along with the rest of the planets in the Solar system. This time in cosmic history is still a mystery to us but we do have some ideas about what went on. We know that the birth of the Sun created a new source of gravity in the young Solar System. The tidal forces between the young sun and the rest of the nebula the Sun was born from created further instability in the gases and dust left in the nebula. This allowed for the steady formation of the planets.

After millions of years passed enough matter collided to gain mass and its own gravity and become small versions of planets called planetessimals and protoplanets. These pre-planets collided to create even larger planets. This set the stage for how the Earth approached its final form. It looks like it probably collided with a another proto-planet and in the process it was tilted.

All the same the Earth’s tilt is very important. It is perfectly positioned so that it gives us the seasons and on top of that the seasons are near perfectly calibrated for life. When compared with other planets Earth’s tilt allows for season that are not too extreme in temperature but are pretty well balanced. At the same if it had stay in the “perfect” position one side of the Earth would be too hot at time and then too cold.

We have written many articles about the Earth’s tilt for Universe Today. Here’s an article about why Earth has seasons, and here’s an article about the Earth’s axis.

If you’d like more info on Earth, 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.

October 15, 2010April 26, 2016 by Tega Jessa

Why is the Center of the Earth Hot

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It interesting that we have explored further into space than we have explored the depths of the Earth. The main reason for that is the pressure and the heat. We know through seismography that temperatures in the inner parts of the Earth actually exceed the surface temperature of the Sun! That is pretty hot. So why is the center of the Earth Hot. The answer comes from a lot different sources. The first is heat left over from the formation of the Earth. The next source is gravitational pressure put on core by tidal forces and the rotation of the Earth. The last known source of heat is the radioactive decay of elements in the inner part of the Earth.

The Earth is pretty old at 4 billion years old and there are still things we don’t completely understand about its formation. We do know that gravity played a role pulling in more matter and compressing it to form the Earth. When you have matter colliding at high velocities like it did in the early stages of the Solar System’s development all that kinetic energy has to go somewhere. In the case of Earth that energy was turned into heat. This heat is the initial source for the temperatures in the Earth’s interior.

The next source of heat is gravitational pressure. The Earth is under immense pressure due to the tidal forces exerted by the Sun, the Moon, and the other planets in the Solar System. When you include the fact that it is also rotating the Earth’s core is under immense pressure. This pressure basically keeps the core hot in the same way as a pressure cooker. It also helps to minimize the heat it loses.

The last and most important source of heat is nuclear fission of heavly elements in the Earth’s interior. In short the Earth has a nuclear engine inside it. It is thank to the continous nuclear fission of elements in the Earth’s interior that replaces the heat the Earth loses keeping it nice and hot. This fission process occurs in the form of radioactive decay. It also creates the convection currents in the mantle that drive plate tectonics.

We have written many articles about the Earth’s core for Universe Today. Here’s an article about the Earth’s outer core, and here are some interesting facts about the Earth.

If you’d like more info on Earth, 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.

Sources:
http://helios.gsfc.nasa.gov/qa_earth.html#hot
http://www.physorg.com/news62952904.html
http://www.ccmr.cornell.edu/education/ask/index.html?quid=215

October 15, 2010January 7, 2016 by Tega Jessa

Why Can We See the Moon During the Day?

We all know the basics of the Diurnal Cycle – day and night, sunrise and sunset. And we are all aware that during the day, the Sun is the most luminous object in the sky, to the point that it completely obscures the stars. And at night, the Moon (when it is visible) is the most luminous object, sometimes to the point that it can make gazing at the Milky Way and Deep-Sky Objects more difficult.

This dichotomy of night and day, darkness and light, are why the Moon and the Sun were often worshiped together by ancient cultures. But at times, the Moon is visible even in the daytime. We’ve all seen it, hanging low in the sky, a pale impression against a background of blue? But just what accounts for this? How is it that we can see the brightest object in the night sky when the Sun is still beaming overhead?

Continue reading “Why Can We See the Moon During the Day?”

October 15, 2010December 24, 2015 by Tega Jessa

Where is Uranium Located

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Uranium is a silvery white metal and is number 92 on the table of periodic elements. It is a well-known element because of its radioactive properties which are used in nuclear reactor powered by nuclear fission. We know that this element is very sought after as source of power by many countries wanting to shift from oil and fossil fuel based economies. So where is Uranium located and how do miners harvest it?

To understand how it is found we need to learn about how it was discovered. Uranium was first discovered by German chemist martin Heinrich Klaproth in 1749 when he was heat treating Minerals. He named the new mineral produced Uranium. The first pure sample of Uranium metal was produced in 1841 by Eugène-Melchior Péligot an analytical chemist who was heat treating Uranium tetrachloride. Demand for Uranium outside its more mundane uses as a window dye was initiated by the discovery of its fissile nuclear properties by Enrico Fermi. Mr. Fermi would go on to lead the Manhattan Project in 1942 that lead to the creation of nuclear weapons and reactors. When the energy it produced was realized the demand for Uranium immediately increased.

So where is Uranium located? In space Uranium is formed naturally occurring in supernovas. However since we can’t even travel to the nearest star it is just a minor fact. On Earth Uranium is surprisingly plentiful for a heavy metal. In fact estimate place the Earth’s supply of Uranium at 30 times that of Silver. This is because Uranium can be found in topsoil anywhere on the planet as well as in the mantle. Scientist even theorize that the natural decay of Uranium and other radioactive elements is what heats the Earth’s core and mantle causing convection currents in the magma and creating plate tectonics.

Uranium can be found as part of a lot of different minerals such as uranite. The element rarely occurs in its pure form. Even then the more fissile kinds of isotopes aren’t plentiful in nature. Uranium ore is the main source of uranium even though with the discovery of how wide spread it is in the Earth’s crust and scientist are looking for inexpensive ways to process it from the soil. In the meanwhile Uranium ore can be found in mines in Canada, Russia, and in Sub-Saharan Africa.

We have written many articles about Uranium for Universe Today. Here’s an article about the lunar Uranium, and here’s an article about nuclear fission.

If you’d like more info on Uranium, check out Wikipedia, and here’s a link to the Encyclopedia of Earth.

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

Sources:
Wikipedia
Encyclopedia of Earth
World Nuclear Association

October 15, 2010December 24, 2015 by Tega Jessa

Where is the Ozone Layer Located

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The Ozone Layer is the portion of the atmosphere that contains high levels of the oxygen molecule ozone. This molecule plays an important role acting as a natural UV shield for the Earth. You may wonder where is the ozone layer located to play such a vital role so effectively. The Ozone layer is actually located in the stratosphere in a region that is 10 to 50 km above the Earth.

So why is the Ozone layer so important? As mention before the secret lies in oxygen molecules. Normal oxygen in its natural molecular state is made up of only two atoms. However this changes when oxygen in the thermosphere is exposed the Sun’s ultraviolet rays. The rays separate oxygen molecules the free oxygen joins with the remaining two atom oxygen molecules to create ozone. This process might seem simple but it helps to screen out 99.5 percent of the ultraviolet radiation that the Sun sends towards earth. The times that the ozone layer didn’t screen out this type of radiation at such levels life was almost wiped out according to the geologic record.

You might think that this is an exaggeration until you observe the biological damage UV rays can do. We have already seen the harm caused when people don’t take the proper precautions when going to the beach. The least harm comes in the form of sun burn. People overexposed to the UV rays that do make it to earth have their skin damaged by the UV energy that penetrates their skin. However it gets more serious the longer a person is exposed to UV rays. The reason is because the damage gets to the cellular level causing cancers and genetic damage. Essentially it’s like being exposed to a nuclear reactor in melt down. The high energy radiation over time would accumulate harm in living tissue until it killed the organism exposed to it.

Despite its importance industry produced and released chemicals into the air that interfered with the ozone cycle. The main problem chemical CFC’s prevented oxygen molecules from complete the bonding process that is important for the completion of the ozone cycle this caused a major depletion of ozone in key areas of the Earth’s atmosphere. This is huge when the natural concentration of ozone was already quite low. This just goes to show the delicate balance that was upset. Fortunately nations upon hearing the harm caused started bans on CFC’s while industry tried to find alternatives to use in products. The result started to show with ozone depletion actually slowing down and reversing with scientist predicting recovery within the next century.

We have written many articles about the ozone layer for Universe Today. Here’s an article about the depletion of the ozone layer, and here’s an article about the ozone layer.

If you’d like more info on Earth, 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.