The Milky Way, the galaxy to which we belong, was formed around 13.6 billion years ago. Inside this galaxy, about 4 billion years ago, our solar system arose from a whirlwind of gas and dust, similar in appearance to a hurricane. The centre of this whirlwind became denser and denser until the sun was formed. The rest of the gas and dust formed the planets and other celestial bodies in our solar system.
Eight principal planets orbit around the sun, with their respective moons or satellites: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune; Pluto which was classified as a planet until 2006 was demoted because of its small size, which is about the size of our moon. Of these eight planets, the four closest to the sun (Mercury, Venus, Earth and Mars) are telluric or terrestrial, that is, they are composed of rocks and silicates, while the remaining four and larger planets are gaseous.
Mercury – In mythology Mercury means the messenger of gods. It is the planet closest to the sun hence its high temperatures, although part of it is dark and cold. Its surface is covered with craters. Galileo Galilei was the first scientist to observe it, in 1610. It is not the hottest planet in the solar system because, unlike Venus, it doesn’t have an atmosphere and therefore it readily dispels the heat it receives from the sun.
Venus – The god of love in mythology, Venus is the second planet in the solar system, and similar to Earth in size. However, it has no water nor any form of life. Its surface temperature can rise to 484 C, and is the hottest planet in our solar system.
Earth – Coinciding with our theme of tri-dimensionality of what is real, our planet Earth is indeed the third planet in our solar system, that is, it is in the best place for the appearance and sustenance of life – not too close to the sun like Venus and not too far away like Mars, even though these two other planets have almost the same dimension as Earth.
Mars – God of war in mythology, with low temperatures, Mars has two poles like those of Earth that can be seen during the Martian winters. This planet is well researched by space probes, which try to detect presence of life or to study the possibility of creating conditions conducive to life on the planet.
Jupiter – God of gods and father of other gods in mythology, it is formed by the same types of gas that make up the sun – hydrogen and helium. Jupiter is a giant gaseous planet, the largest in the solar system. If it was any bigger, it would be classified as a star, that is, it would burn like the sun.
Saturn – God of agriculture in mythology, it is the second largest planet after Jupiter. It is also gaseous, and has as its principal characteristic the rings that surround it, formed by particles of dust and ice.
Uranus – God of heavens in mythology, it is a planet that is so tilted on its axis that it undergoes its rapid rotation practically on its side. Contrary to the poles of the Earth, the poles of this planet face the sun. It has an atmosphere composed of hydrogen, helium and methane.
Neptune – God of sea in mythology, it is a large gaseous planet, and the farthest from the sun. It has some thick rings and some thin rings around it.
The Sun
I am the vine, you are the branches. Those who abide in me and I in them bear much fruit, because apart from me you can do nothing. (John 15:5)
Diameter: 1.4 million kilometers
Mass: 330 thousand times greater than the mass of planet Earth
Temperature: 15, 000, 000 Celsius at its core
The distance between the Sun and the Earth is approximately 150 million kilometers. Light takes about 8 minutes and 20 seconds to travel from the sun to us. The sun is a star of medium size and luminosity, there are billions of stars in our Milky Way galaxy that are much bigger than our sun.
The sun is composed primarily of hydrogen (74.9 %) and helium (23.8 %), its light and heat make it possible for living beings to survive on Earth. It is a nuclear fusion reactor: temperature and pressure at the sun’s core are such that hydrogen atoms fuse together to form helium atoms. This process releases a tremendous amount of energy which radiates to the sun’s surface, escaping into space as electromagnetic radiation of light and heat.
By its force of gravity, the sun pulls all the planets in the solar system to orbit around it. The law of gravity dictates that the body of the greatest mass attracts the bodies of lesser mass; for this reason all planets revolve around the sun from which they receive light and heat. Fortunately for life on Earth, our atmospheric layer blocks the sun’s x-rays, most of the harmful ultraviolet rays, and absorbs most of the infrared radiation. Were it not for this absorption, particularly of the x-rays and ultraviolet rays, the sun, the source of life, would have been the source of death…
Around every 11 years, the sun goes through a period of extreme turmoil, sending storms of charged particles to Earth resulting in our climate getting warmer and increased interference with magnetic instruments on the surface of the Earth. In addition to these electric discharges influencing the electronic systems on our planet, these waves of energy create the well-known Aurora Borealis and Australis, where the air shines in the regions near the magnetic poles of the Earth, generating in the sky a spectacle of lights and colours.
A solar cycle lasts an average of 11 years, and happens because there is a flip of the sun’s poles – north becomes south and south becomes north, and vice versa every 11 years. This flipping correlates with the minimums of sunspot activities, and decreased solar storms hitting the Earth, in other words, expected cooler climate. Interesting enough, we are at the end of solar cycle 24 and solar cycle 25 is expected to start sometimes in 2019.
The sun shines because it converts its hydrogen center into helium. This process creates the energy that nourishes us, but it also causes the sun to lose mass, that is, to become smaller and smaller. Every second that passes, the sun converts 600 million tons of matter into energy. Four and half billion years have already passed since this process started and the sun still have enough hydrogen to continue burning for another 5 billion years. After that the hydrogen will run out and our sun will die. Up until now the sun has already converted an amount of hydrogen comparable to 100 times the mass of Earth into helium and energy.
Contrary to logic, the sun is apparently not dying bits by bits, producing less and less energy. The more hydrogen that is converted into helium, the more the sun’s core shrinks, causing the outer layers of the sun to come closer to the center under a stronger gravitational force. This causes more pressure on the core, accelerating hydrogen fusion and increasing energy production, which leads to an increase of 1% in brightness every 100 million years. In the past 4.5 billion years, corresponding to the age of the sun, this energy has already increased by about 30%.
Consequently, within 1 billion years, the sun will be 10% brighter than it is now. This increase in luminosity will lead to an increase in heat and energy that the Earth and its atmosphere will have to absorb, causing in turn an increase in the greenhouse effect that little by little will convert our planet into what Venus is like today: the hottest planet in the solar system with temperature of about 500 C.
In 3.5 billion years, the sun will be 40% brighter than it is today. Under these conditions, the oceans will boil and water vapour will be lost to outer space, transforming our planet into a hot and dry planet like the present day Venus. At that time, it will not have temperatures higher than Venus, for the simple reason that Earth is further away from the sun.
When all the hydrogen in the sun’s core is used up, the inert helium ash, the result of the hydrogen fusion, will end up collapsing under its own weight. This will cause the sun’s core to become denser and hotter, causing the sun to grow in size and enter into its red giant phase.
In this phase of the sun’s evolution, the orbits of Mercury and Venus will be absorbed, two thirds of our sky will be occupied by the sun which will gradually encompass our planet. When it reaches this phase, the sun will still have 120 million years of active life. Finally, the accumulated helium will ignite violently and in the next 100 million years, it will burn the helium that resulted from hydrogen fusion.
The size of the sun will become ever larger until it turns into a white dwarf. In this state, it can still survive for another trillions of years to finally turn into a black hole.
The Moon
Equatorial Diameter: 3,474.8 km
Volume: 22,000,000,000 km³
Mass: 73,500,000,000,000,000,000 kg
The moon is the Earth’s only natural satellite and the fifth largest one in our solar system. It is also the largest in comparison to its corresponding planet. There are several theories to explain its formation. The one that gains most followers states that the moon came about from an impact of a celestial body the size of Mars against the Earth in the area now occupied by the Pacific Ocean.
The visible or the near side of the moon is characterized by large flat dark patches as viewed from Earth while the far side or the dark side of the moon, because it faces away from Earth, is rugged and has many craters formed possible from impacts with other celestial bodies. There is no atmosphere on the moon to protect any living beings from solar radiation; in other word, there are no gases at its surface like that found in the atmosphere of either Earth or Venus.
In addition to a lack of atmosphere, the moon also does not have water, which explains why it is devoid of wind (air) or hydraulic erosion (water). The average temperature on the moon is 106 C. In its revolution around the Earth, it goes through a phase cycle, depending on its position in relation to the Earth and the Sun. During this cycle, its appearance seems to change gradually from not being visible to being fully visible when viewed from points on Earth. The full cycle, that is, the lunar month lasts approximately 29.5 days.
The New Moon
The new moon occurs when the visible side of the moon does not receive any sunlight because these two celestial bodies have their axes pointed in the same direction. In this phase, the moon is in the sky during the day, rising at approximately 6:00 am and setting at 6:00 pm, like the sun. It is only at this phase that solar eclipse can be observed.
The First Quarter
During the subsequent days, the moon will move more and more to the east of the sun, and therefore the visible face will become more and more illuminated from the westward leading edge, until about one week later when we reach the first quarter phase, with 50% of the moon illuminated.
The Full Moon
During this phase 100% of the moon can be seen. The moon is in the sky all night, rising approximately at 6:00 pm when the sun goes down, and sets at sunrise, at approximately 6:00 am. The moon and the sun as seen from the Earth are in the opposite direction, separated by approximately 180 ° or 12 hours. It is only during this phase that lunar eclipse can be observed.
The Third Quarter
During the subsequent days after a full moon, portion of its illuminated face begins to become smaller and smaller, as the moon moves more and more west of the sun. The lunar disc will lose as the days go by a larger piece of its westward border. Until about seven days later, when the illuminated portion has been reduced to 50% and the moon is at its third quarter.
The moon is about 90 ° west of the sun, and is seen from the Earth as a semi-circle with the rounded part pointing to the east. It rises at midnight and sets at midday. In the days that follow, the moon continues to wane, until reaching the day zero of a new cycle.
The Hidden Side of the Moon
This is the side of the moon that we never see, the side that faces away from the Earth, the hidden side or the far side. The full rotation of the moon on its axis and its complete orbit around the Earth take the same amount of time to complete because the moon is gravitationally locked to the Earth, this results in the moon always showing the same side to Earth while the other side is not visible from our planet: the hidden face of the moon.
Applying to the moon the same logic of what we know of Earth – in the sense that the Earth’s rotational movement defines the day and its orbit around the sun defines the year –with the moon, the time it takes the moon to complete a full rotation on its axis is the same amount of time it takes for the moon to complete its orbit around the Earth; what is a day for the moon is the same as one year, and one year equals one day. Both the day and the year is equivalent to 27.3 earthly days.
It is therefore not true what many people think to explain why the moon always shows the same face to us because it does not rotate on its axis like the Earth; it does have this rotational motion, but it is synchronized with that of the Earth, so that we end up seeing the same side of the moon.
The Effect on the Earth’s Axis
The gravitational force of the moon keeps the Earth in a stable equilibrium with a tilt on its axis of rotation of 23 degrees. This tilt stays unchanged; without the moon’s gravity locking the Earth, the latter would rotate in a less stable and more variable fashion.
The Earth is like a spinning top that spins on itself: as the top loses speed, it tilts and gyrates with its top axis drawing wider and wider circles. The moon, however, makes these circles not vary in size and to remain constant. This makes the seasons occur with regularity each year. Otherwise, there would a frequent disruption of the climate, the poles would change position and the climate would be extreme and unpredictable.
The Effects of Tides
Tides are changes in the sea level caused by the gravitational interference of the moon and the sun (the latter to a lesser degree due to its increased distance) on the Earth’s gravitational field.
Due to the rotation of the Earth and the rotation of the moon, these elevations propagate across the surface of the Earth, causing high tides every 12 hours and 25 minutes, and low tides between high tides. Tides also occur in the earth’s crust, raising the floor as much as 10 centimeters during a high tide.
The effect of the tides is reciprocated between the Earth and the moon. Because the Earth has a greater mass than the moon, it exerts a much greater tidal force on the moon. It is very likely that the synchronization between the periods of rotation and revolution of the moon occurred due to this tidal locking effect.
Unknown to many people, this implies that the interaction between these two co-orbiting celestial bodies causes the speed of the Earth’s rotation to decrease at a rate of 2 seconds every 100,000 years, or increasing the length of one day by 0.0016 second every century, and consequently the distance between the Earth and moon increases at a rate of 4 centimeters per year because of the conservation of angular momentum. This means that without the moon, the days on Earth would be shorter. It is the attraction that the moon exerts on the oceans that causes the Earth to rotate more slowly than it would otherwise.
The Apparent Size of the Moon and the Sun in the Sky
The diameter of the sun is around 1,400,000 km while the diameter of the moon is about 3,500 km. Therefore the sun’s diameter is around 400 times that of the moon. But the sun is also about 400 times farther from us than the moon. This amazing coincidence results in the fact that both the sun and the moon as seen from the Earth have the same apparent size. This is why the eclipse of the sun is possible, that is, it is possible for the moon to cover the sun completely as seen from the Earth because the moon being 400 times smaller than the sun also happens to be 400 times closer to the Earth than the sun.
The Earth
Earth is the third closest planet to the sun, it is the densest and the fifth largest of the eight planets in the solar system.
Equatorial Diameter: 12,756 km
Polar Diameter: 12,713 km
Volume: 1,083,000,000,000 km³
Mass: 6,000,000,000,000,000,000,000,000 kg
The Three Motions of the Earth
All the planets in the solar system with the exception of Earth have two motions: a spinning motion on its axis and an orbiting motion around the mother star, the sun. The duration of these movements varies according to their mass, the satellites that orbit around them, and their distance from the sun. Based on Earth’s time, Neptune, for example, has a day of 166 hours and a year that lasts over a century and a half. Meanwhile, Mercury completes its orbit round the sun in 88 days and therefore has a year much shorter than ours. However, it takes Mercury practically two months to spin once around its axis, in other words, one day on Mercury lasts about two months. In Venus, one day is practically the same as one year.
Earth like the other planets in the solar system is continuously in motion. However, unlike the other planets, Earth undergoes three types of motions. The orbiting movement around the sun, which determines the duration of a year; the spinning movement on its axis which takes 24 hours or one day to make one full turn, and the oscillation movement on its axis that causes the Earth to vary its angle as it revolves around the sun, giving rise to the seasons and the most varied climates.
The Atmosphere of the Telluric or Terrestrial Planets
Mercury – There is no atmosphere in Mercury.
Venus – It has a very dense atmosphere made up mostly of carbon dioxide (96%), nitrogen (3%), and traces of water and sulfur gas, with even smaller percentages of argon, xenon, neon, and helium. The atmospheric mass of Venus is over 90 times greater than Earth's, resulting in Venus having the strongest greenhouse effect than any other planets in our solar system. Beyond this thick layer near Venus’ surface, there are thick clouds made up mostly of sulfur dioxide and sulfuric acid, which gives Venus its yellowish appearance. This nebulous structure is so thick and persistent that the sun and other stars cannot be seen from Venus; furthermore, the sulfur in the clouds is highly reflective of visible light so that during the day the yellowing light is dimmer than that of an overcast day on Earth with the surface temperature rising to more than 460 C.
Mars – Without the extreme temperatures and crushing pressures, Mars have a force of gravity lower than Earth’s and an average temperature similar to that of Antarctica, at -50 C. Mars’ atmosphere much like that of Venus is made up mostly of carbon dioxide (95.3%), nitrogen (2.7%), argon (1.7%) with traces of water. The remaining planets, being gaseous, do not differ much from one another in terms of mass and atmosphere, except for the rings around Saturn.
The Evolution of Earth’s Atmosphere
Earth formed from cosmic dust composed of silicates that began to agglomerate 4.6 billion years ago until reaching its actual size, about 150 million years ago. At that time, Earth was a rocky ball of fire and lava, and had no atmosphere. When it began to cool down, a solid crust formed which occasionally liquefied because of the intense and continuous volcanic activities.
The gases that the volcanoes released formed the Earth’s primitive atmosphere which was composed of 40% nitrogen, 30% carbon dioxide, 25% water vapour, 5% methane, with traces of ammonia. As it rose, the water vapour in the atmosphere condensed and fell in the form of rain. However, as it fell onto the burning ground, it evaporated again, this cyclical process continued for 100 million years, but led to the significant cooling down of the earth’s ground temperature.
When the land temperature reached below 100 º C, the boiling point of water, water started to accumulate in the lowest points of the planet’s surface. The greenhouse effect diminished and allowed the atmosphere to become more permeable to solar radiation, particularly the ultraviolet radiation. Furthermore, approximately 80% of the carbon dioxide present in the primitive atmosphere was fixed in the silicates of the earth’s crust, giving rise to limestone and thus reducing its presence in the atmosphere.
As the consequence of this action from the ultraviolet rays and the electrical discharges of lightning on the primitive atmosphere, as well as the heat from the volcanoes, organic matter was formed and accumulated in the primitive oceans. The first bacteria and blue-green algae – cyanobacteria – appeared with the ability to initiate photosynthetic activity: the absorption of carbon dioxide to form carbohydrates releasing the first molecules of oxygen (which took place about 2.4 billion years ago).
This continuous process progressively enriched the earth’s atmosphere for 1.5 million years, allowing the appearance of more complex oceanic organisms that used oxygen in respiration. Furthermore, the oxygen released from the water into the atmosphere upon being bombarded by the sun’s ultraviolet radiation formed ozone which gradually filtered out the dangerous rays of the sun allowing living beings, which until then only existed in the oceans, to colonize the land environment.
Two hundred million years ago, the Earth’s atmosphere reached its present composition:
Nitrogen 78.08 % -- The most abundant component of air and also the most important for life. Nitrogen is a key component in the molecules of amino acids, proteins, DNA and RNA. The latter two are the genetic materials that contain information that determines the hereditary characteristics that are passed down to offspring.
Oxygen 20.95% -- This gas appears in the atmosphere in a proportion of about 21%. Oxygen gas (O2) is indispensable for cellular respiration: when breathed in, it is carried to all the cells in the body via blood, and reacts with glucose (C6H12O6), producing water (H2O), carbon dioxide (CO2) and the energy required to carry out all bodily activities.
Plants produce oxygen during photosynthesis (a mechanism that is virtually the opposite of cellular respiration), releasing it into the atmosphere. In addition, oxygen is also the main oxidizer, that is, it “feeds” the process of combustion.
As we know it, life on our planet is linked to the appearance of oxygen and vice versa. Oxygen and life are entrapped in the egg and chick logic, one depending on the other not knowing which one came first.
Carbon dioxide 0.035% -- This gas is one of the by-products of cellular respiration, which is released into the environment. Plants use carbon dioxide in the process of photosynthesis, producing from it their reserve of carbohydrates.
One of the causes of the greenhouse effect is the excess of this gas in the atmosphere due to the burning of fossil fuels – fuels formed by the decomposition of organic matter (oil, coal and natural gas).
Water vapour – Arising from the evaporation of the waters in the oceans, rivers and lakes by the action of the solar heat. Its amount in the atmospheric air varies according to the temperature, the region of the planet, the season of the year, among other factors. Some phenomenon important to life are due to water vapour: the formation of clouds, rain and snow.
Life is not only composed of organic matter but also of inorganic matter such as water, oxygen, mineral salts such as sodium chloride, and metals such as iron. These inorganic elements facilitate chemical reactions of the organic compounds that are responsible for life. In an analogous way, life only occurs on Earth but it would not be possible without the facilitation of the Sun and the Moon.
So we come to the conclusion that the macro system responsible for life is Trinitarian, or tridimensional, since it is the close interaction between three celestial bodies -- the Sun, the Moon and the Earth --- that makes life possible and sustains it on our planet.
Fr. Jorge Amaro, IMC
