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God Likes Big Numbers!
(Subtitle – All you ever wanted to know about astrophysics but were afraid to ask!)

Genesis 22:17 – God promises Abraham that his descendants will be as numerous as the stars in the sky and the sands on the seashore.
If you were Abraham, which of the two examples would give you a better estimation of the number of the descendants?  In Abraham’s time, there were no telescopes so he could not have known how many stars are in the sky but it is known today that there are about 5000 stars that can be seen by the naked eye and all of those are in our own galaxy. But, Abraham would probably have concluded that the number of sand grains on the seashore would be a far greater number even so.
 
Let’s do a little calculation of the number of sand grains assuming that the earth’s entire surface is seashore and that the sand is 1 meter thick.  Let’s also assume that a sand grain can be approximated by a little cube 1/100 of a centimeter on a side.  How many grains would there be on Earth compared to the number of stars are in the sky today?  The answer is astounding—for every cubic centimeter of sand on Earth, there are 100 stars !
We’ll come back to this example of God and his creation later after we gain some basic current knowledge of astrophysics as given below.
 
What is a star?
A star is a large sphere of gas (mostly hydrogen) that creates energy by the fusion of hydrogen into helium, in the same fashion as a man-made hydrogen bomb. It is estimated that our sun converts 700 million tons of hydrogen into 695 million tons of helium each second to sustain its energy output.
 
What is a binary star?
A binary consists of two stars orbiting each other around a common center of mass.  Many of the stars we see in the sky are not individual stars but rather binaries that are so close to one another and so far away that they appear as one.
 
What do stars do besides creating light?
 Stars are factories that create all of the known elements during their lifetimes. The sequence of element formation is hydrogen to helium to carbon to oxygen to magnesium to silicon to iron. (The fact that the element formation ends with iron will come up later in this discussion.)
 
How long does a star live?
Oddly enough, large stars usually live shorter lives (millions of years) than smaller stars which can live for billions of years.
 
What is the expected lifetime of our star, the sun?
The sun’s lifetime is estimated at 9 billion years, and it is approximately halfway through its lifetime so it should live another 4.5 billion years.
 
Is our sun one of the largest stars?
No, our sun is a rather small star compared to others. It is about 800,000 miles in diameter which is 100 times the diameter of earth.  But the largest star known (VY Canis Majoris) is about one billion miles in diameter which is more than 1000 times larger in diameter than our sun.
 
What will happen to our sun when it reaches the end of its life?
Our sun is the type of star that will end its life by becoming a “red giant” which will expand and engulf the planets around it. Therefore, the earth will eventually be engulfed by the sun and be vaporized. The sun will then shrink into a white dwarf star about the size of earth and continue glowing even longer (billions of years).
 
What will happen to people on earth when our sun becomes a red giant?
In order to survive in that distant future, people of earth will have to migrate to other planets farther from the sun in our solar system. The most likely first choice is Mars provided that humans could have previously prepared it for life.  For example, its atmosphere now is mostly carbon dioxide and would have to be converted to oxygen for people to breathe.  This could be done by planting trees on Mars since trees take in carbon dioxide and give off oxygen just as they do on earth. This would have to be done well in advance of human settlement.  However, a settlement on Mars would eventually also be engulfed by the expanding sun so humans would have to migrate even further out, perhaps to one of the moons of Jupiter when those became habitable.
 
Where did the planets of our solar system come from?
The planets are leftover material from the formation of our sun.  The four inner planets (Mercury, Venus, Earth, and Mars) are rocky in nature while the four outer planets (Jupiter, Saturn, Neptune, and Uranus) are called gaseous planets and have no solid surface.
 
What happened to Pluto?  Isn’t that the ninth planet?
Pluto used to be called the ninth planet.  However, many other celestial bodies have been discovered  beyond the distance of Pluto from the sun (2 billion miles).  Pluto was therefore demoted from planet status since there are others like it that are unnamed and not considered planets.
 
What is a planet ?
A planet is a spherical body that orbits a star.
 
What is a “rogue” planet?
A rogue planet is a planet that once orbited a star but was ejected from its orbit by gravitational forces and now wanders through interplanetary space.  It is estimated that there as many rogue planets in our galaxy as there are stars.
 
If our sun is making elements in its interior, where did all the elements on earth, including the elements in our bodies, come from?
The elements on earth and in our bodies were part of the large cloud that condensed and formed our sun and planets 4.5 billion years ago. The elements in that cloud were made in previous generations of stars that existed long ago.  Therefore, the elements in our bodies were made in stars that existed and exploded more than 4.5 billion years ago.
 
What is a galaxy?
A galaxy is a grouping of a large number of stars, usually billions in number. The galaxy in which we live is called the Milky Way galaxy and consists of some 200 billion stars in a flat spiral shape. On a clear night with no moonlight, our galaxy can be seen as a luminous white band across the sky.  The whiteness comes from the merged light of billions of stars so far away that they cannot be seen individually.
 
How big is our galaxy?
The Milky Way galaxy is about 100,000 light years across.
 
What is a light year?
A light year is the distance that light travels in a year. Since light travels at a speed of 186,000 miles per second, a light year is equal to about 6 trillion miles. (6,000,000,000,000)
 
 How many galaxies are there in the universe?
It is estimated that there are 200 billion galaxies in the “known” universe. To give you a rough idea of how many that is – suppose you go out at night and hold your thumb up at arm’s length and stare at your thumbnail.  No matter where you point your thumb, there will be about 3 million galaxies hidden behind your thumbnail!  But then, the “known” universe is only the part we have been able to see with current technology.  Other galaxies may exist beyond the distance that we can see with current telescopes.
 
Is our galaxy the largest galaxy?
No, there are galaxies that contain more stars than our Milky Way galaxy.  For example, the Andromeda galaxy is a similar but larger spiral galaxy and contains perhaps a trillion stars.
 
Do different galaxies ever collide?
Yes, there is evidence that galaxies collide from time to time, usually creating a larger galaxy, typically of an elliptical shape.  Our galaxy is on a collision course with the Andromeda galaxy which is approaching ours at a speed of 300,000 miles per hour.  However, because of the distance to Andromeda, this collision won’t happen for about 2 billion years.
 
When did the universe begin?
Scientists tell us that the universe began in a “Big Bang” about 13.7 billion years ago.
 
Are there any other civilizations in the universe besides us?
Scientists have looked for but have found no signals from other worlds.  But, if such a civilization existed on the other side of our own galaxy, it would take tens of thousands of years for their radio/TV signals to reach us and even then they would be very weak.  Since we have had radio for about 100 years, our signals have only spread out about 100 light years from earth.  Therefore, only the planets of stars within 100 light years of earth could have possibly heard our signals and realize that we exist.
 
But what are the odds of another planet like Earth with living beings somewhere in the universe? Such a planet would have to be within the habitable region around a star, such that it is not too hot nor too cold, and to have liquid water for life as we know it.
Since there are about 200 billion galaxies in the universe, each with about 200 billion stars, there are many, many stars in the universe!  If an Earthlike planet were to be found only once in every billion of these stars, there would still be 200 in our own galaxy or 40 trillion in the known universe!  It, therefore, seems very likely that there are habitable planets like Earth in our universe. (Note:  An edition of Popular Mechanics magazine had a new estimate of planets in our own galaxy – 11 billion Earth size worlds!)
 
Have planets actually been found around other stars?
Yes, approximately 2000 other planets have already been found around nearby stars and new ones are being discovered by astronomers at a rate of one per week!  However, these have been large planets (which are easier to detect) and many are very close to their parent stars which is not a habitable environment as we know it.
 
What does the term “supernova” mean?
A supernova means an exploding star. Such a star puts out a tremendous amount of light during its explosion. For example, a supernova detected in 1987 gave out more light in one second than our sun will give out in its entire lifetime of 9 billion years!
 
What is a “black hole”?
A black hole is a massive star (10-15 times the mass of our sun) that has collapsed at the end of its life.  It is a very dense object, comparable to the mass of the Earth compressed into the size of a golf ball!   It is so dense that even light cannot escape it, hence it cannot be seen in a telescope. There are two types of black holes.  One is called a stellar mass black hole that results from the collapse of a large star as described above. The other type is a supermassive black hole that contains millions of times the mass of our sun.  These are usually found at the center of galaxies.  The supermassive black hole at the center of our Milky Way galaxy is estimated to have a mass of 4 million suns. The supermassive black hole at the center of the Andromeda galaxy is estimated to have a mass of 140 million suns. The supermassive black hole at the center of the M87 galaxy is estimated to have a mass of 4 billion suns. The largest known black hole is the one in the galaxy known as NGC4889 and has a mass of 20 billion suns!
 
What is a neutron star?
A neutron star, like a stellar mass black hole, is a collapsed star but not as dense or massive as a black hole. One teaspoon full of neutron star material would weigh 100 million tons! Neutron stars can be small (e.g. 10 miles in diameter) and can rotate very fast.  One such star in the Orion nebula rotates 30 times per second.
 
What is a pulsar?
A pulsar is a neutron star that can be formed during a supernova explosion.  They were discovered when a pulsing or blinking light was seen in space and the pulsing light was first thought to be a signal from another civilization.  The pulsing can be of various rates, from a few times per second to hundreds of times per second.  Scientists finally figured out that this was caused by radiation streaming from the poles of a spinning neutron star, when the poles happened to line up in our direction.  In other words, it was like a lighthouse where you only see the beam when it happens to point at you although it is pointing elsewhere when you don’t see it.  Neutron stars are typically about 10 miles in diameter but they can spin at tremendous speed, even hundreds of rotations per second.  Their rotation speed determines the “pulsing” rate that is seen.  Like black holes, neutron stars attract matter from their surroundings and when this matter falls onto the surface of the neutron star at a non-normal angle, the matter causes the rotation speed to increase.
 
What is a quasar?
A quasar is a super massive black hole that is sucking matter into itself by its tremendous gravity and        causing that matter to emit radiation in the process. Since the matter falls into the black hole at a varying rate, the radiation seen can also vary with time.  The black hole is said to be “feeding” as it engulfs matter and emits bursts of radiation.
 
Where did the earth’s moon come from?
Scientists have pondered over the origin of the moon for many years but recently they agree that, early in its formation, the earth was struck by another object about half the size of earth. The result of that collision was that much debris was scattered into orbit around the earth.  This debris eventually coalesced into a spherical object we now call our moon.  This was actually a good thing for earth because it stabilized the earth’s spin.  The moon keeps the earth from wobbling as it goes around the sun and allows us to have predictable seasons of the year.  The moon is also a boon for surfers because it causes the tides whose waves break on our beaches!
 
So what does all this astrophysics knowledge have to do with GOD?
 Scientists say that our universe was created in the Big Bang 13.7 billion years ago.  But our solar system was created only 4.5 billion years ago.  So it is natural to ask “What was God doing from 13.7 billion years ago until 4.5 billion years ago?”  Was God waiting 9.2 billion years before creating the Earth and its creatures?  Or, is it more likely that God would have created other civilizations in our galaxy or other galaxies during that lapse of time? Some estimate of the answer can be had from the Drake equation.
 
Drake Equation
In 1961, astronomer Frank Drake proposed a method of estimating the number of civilizations in our galaxy that could be detectable from Earth. He wrote it as an equation, but it may be more useful to think of it as a series of questions: How many stars are in our galaxy?  What fraction of them have planets? How many planets does each such star have? What fraction of those planets can support life, and of those, how many planets actually give rise to life? What fraction of those living planets give rise to intelligent beings? And of all those planets with intelligent beings, what fraction will produce radio transmissions that would allow us to detect them, and how long would they continue to transmit them? These questions can be answered by inserting terms into the Drake equation which is:
N = R fp ne fl fi fc L
N is the number of civilizations in our galaxy that use detectable communications.
R  = the average rate of new star formation per year in our galaxy (latest estimate = 7 per year)
fp is the fraction of those stars that form planets.  The best estimate from current knowledge is 1.0, that is, all new stars form planets.
ne is the average number of planets each such star possesses, which are capable of supporting life. The best estimate from current knowledge is 3.
fl is the fraction of those planets where life actually occurs.  The best estimate from current knowledge is 0.1.
 fi is the fraction of life-bearing planets where intelligence arises.  The best estimate from current knowledge is 0.1.
fc is the fraction of intelligent life-bearing planets where intelligent beings develop the ability to communicate beyond their own world. The best estimate from current knowledge is 1.0.
L is the length of time, in years, that such communications remain detectable. The best estimate from current knowledge is 10,000.
 
Using this equation and using the estimates shown, it is estimated that there are 2100 civilizations in our galaxy alone that could possible communicate with us.
 
Note: You can make your own calculations with the Drake equation at the website:
 
If God has indeed created other civilizations, is it likely that they would need a redeemer like Jesus on Earth?
Since God is a master creator and has created intelligent life capable of loving Him in return, it seems likely that those civilizations, like ours, would fall into sin if given free will.  Therefore, it may be that Jesus continues an eternal job of visiting and offering redemption in countless other civilizations just as he did on Earth. Although this is conjecture, it is certainly food for thought. And, if true, it would reflect the awesome creativity of almighty God!
 

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