The young Earth vs. the speed of light
This week I’d like to discuss the Young Earth Creationists and the reason that astronomy and mathematics thoroughly refutes their claim that the Earth was created as is barely more than 6,000 years ago.
The Young Earth premise seems to be based on some literal interpretations of ancient scriptures. For example the commentary on Genesis by Ibn Ezra around the tenth century a.d., though most modern Jewish scholars dismiss such a literal reading of ancient texts. The modern Young Earth Creationism seems to be rooted in writings by the Archbishop Ussher who published the Ussher Chronology in which he dated the Earth from the night preceding October 23, 4004 BC . This of course is in close agreement with many other scholars such as even great minds like sir Issac Newton and Johannes Kepler who placed the beginning of Earth at circa 4000 b.c. and 3992 b.c. respectively among others throughout history.
It wasn’t until the time of William Thomson, a.k.a the first Baron of Kelvin, (Lord Kelvin), who remained an extremely devout Christian throughout his life, that the Earth’s age became generally accepted as ancient. In 1897, Lord Kelvin calculated the age of the planet based on his knowledge of thermodynamics. i.e. the assumption that the planet was molten in the beginning and given the known mass of it and the known rate of cooling, that put the age of the Earth between 20-400 MILLION years. A huge range as you might notice but absolutely correct….except again his knowledge was incomplete. He had no concept of radioactive decay and how that and tidal forces would keep the interior of the Earth molten to this day.
James Hutton, (1726-1797), who is considered the father of modern geology got no respect during his time yet his research and his careful observations ushered in the era in which we look to the record preserved in the rocks for answers and we would forever after talk about the age of the earth in BILLIONS of years.
Newton and Kepler and even Ussher can be forgiven because their knowledge was seriously limited and astronomy was in it’s infancy and geology wasn’t more than the collecting of curious rocks. Lord Kelvin was guilty of not reading about the work of his countryman and focusing instead on his field to the exclusion of others. In fairness to him, it should be pointed out that in Lord Kelvin’s time, modern geology was still disputed by many religious scholars along with Darwinism. There is no such excuse today. The age of the planet is not an opinion and is not open for debate beyond the range of a few tens of millions of years. Radiometric dating is far too precise to allow for any debate on the fact that the planet is at the minimum, ten and a half times as old as Kelvin’s upper estimate but we’re here to talk about astronomy.
If we are to accept archbishop Ussher’s chronology of the Earth, that would put the upper age of the planet at 6,014 years old, next October 23rd. That would mean that the furthest object visible in telescopes would be 6,014 light years away or less. We know this because the speed of light has been measured over and over with a high degree of accuracy and that it is consistent and FINITE. The speed of light that is traveling in a vacuum is 299,792,458 m/s, (meters per second), with a relative measurement uncertainty of four parts per billion. Therefore we see Proxima Centauri, the closest star to our own solar system as it was 4.2 years ago, as it is 4.2 light years away, a light year being the distance it takes a light to travel in a year.
How do we know how far away Proxima Centauri is? Several ways but the one I want to focus on is called stellar parallax. Parallax is the phenomenon of closer objects seeming to move against a more distant background depending on your point of view. Hold a finger about a foot away from your face. Close one eye and then the other. Flip back and forth between eyes and your finger appears to move against a more distant background. We can do the same thing from the Earth with nearby stars. The orbit of the Earth is a rough circle that is about 185 million miles, or 297 million kilometers in diameter. The difference between the views of distant objects from opposite points in the Earth’s orbit around the sun is called the annual parallax. This gives us the definition of a parsec, which is 1 arc second of movement against the background stars per annual parallax. This works out to be 3.26 light years. Now the only limiting factor is how accurately can such things be measured.
Pretty accurately as it turns out. Friedrich Wilhelm Bessel made the first successful parallax measurement of the distance to another star when he measured the distance to 61 Cygni at 10.4 light years way back in 1838. Turns out that the actual value for the distance is more like 11.4 light years but his heliometer was a pretty crude device. This is also the first time an accurate scientific measurement of the distance to another star was made. Bessel was limited by the quality of his instruments but we have much better devices today, both here on Earth and in orbit. Hipparcos was launched in 1989 and can detect parallax of stars as far away as 1,600 light years and next year the Gaia mission will allow measurements of 10 microarc seconds, pushing that distance back to ten of thousands of light years.
WTF does any of this have to do with age of the Earth you ask? And well you should because so far this seems like a study in digression. yet it’s very relevant. As we KNOW the speed of light and we KNOW the distance to nearby stars and we KNOW their luminosity and we KNOW how much that luminosity decreases with a given distance, all we have to do is find a star type with a KNOWN distance and a KNOWN luminosity and then we can extrapolate the distance to similar stars with incredible accuracy. This is called a standard candle and can then be used to measure distances into the billions of light years. This is how we have determined the universe is about 13.73 BILLION years old. Ergo the Earth and the universe cannot be younger than that or the light from these very distant stars which we can measure very accurately would not have reached us yet.
So we would see the Orion Nebula but not the Carina Nebula. The Andromeda Galaxy? We would have no idea it exists. Heck, we wouldn’t even see the center of OUR OWN galaxy if the young Earth proponents were correct, since that lies over 26,000 light years away. We would be existing at the center of a bubble of stars barely 6,000 light years across and every year that passes, we would have more and more stars come into our field of view and astronomy would be more a science of naming, than a science of measuring. The only thing you have to do to refute young Earth creationism is to go outside away from the city on a clear night. The evidence is clear and irrefutable. Just look up.