[Originally published as the second part of Faulty Speculations on the Pre-Flood World: Part 1]
Continued from Part 1, and Part 2: We here examine additional assertions made by Troy, a young earth creationist who has made some highly unorthodox claims about conditions before the Genesis flood relating to the speed of earth’s rotation at creation.
Earth’s Spin Speed
Troy: I never said one earthquake or one event significantly slowed the spin of the earth. I am suggesting that many events and one catastrophic global flood changed the spin velocity of Earth.
Lisle: No combination of earthquakes, volcanoes, or a global flood will alter the rotation rate of the earth. This is due to a principle in physics called the conservation of angular momentum. Basically, any spinning object will continue to spin at the same rate with constant angular momentum unless acted upon by an external torque. Earthquakes, volcanoes, and the global flood are not external. Therefore, they cannot affect the angular momentum of earth.
The only way to slow the earth’s rotation is therefore to transfer some of its angular momentum to an external object.¹ Volcanoes, earthquakes, and floods are not external to earth and therefore no combination of them can slow earth’s rotation at all. The only significant external torque being applied to earth is tidal torquing due to earth’s moon. This causes the moon to move away from earth, which increases the moon’s (orbital) angular momentum and simultaneously decreases earth’s rotational angular momentum by the same amount. Thus, the total angular momentum of the earth-moon system is conserved.
Troy: Your ending logic does not connect because you are missing the catastrophic global flood.
Lisle: On the contrary, Troy’s logic does not connect because the global flood is not an external torque. It therefore cannot change the angular momentum of earth, and hence cannot slow earth’s rotation. Troy’s speculation violates the law of conservation of angular momentum.
Troy: Using a verse that is roughly 2,400 years after the global flood is equivalent to secularists using the Uniformitarian theory to support an old earth.
Lisle: Students of logic will recognize Troy’s error as the fallacy of false analogy – making a comparison between two things that are not really alike in any way relevant to the argument. When the Apostle Peter (writing under the inspiration of the Holy Spirit) writes about the global flood in 2 Peter 3:6, he is writing about 2,400 years after the global flood. Does this make his point any less valid? Does it make him “equivalent” to the very uniformitarianists that he is criticizing? Hardly.
Troy seems to be confusing uniformitarianism with uniformity.
The former is an unbiblical assumption that rates and conditions are comparable to today when there is good reason to think otherwise – such as historical records. So, a denial of the global flood would be an example of uniformitarianism because it denies what the Bible affirms. Conversely, uniformity is the biblical principle that God upholds His creation in a generally consistent way for our benefit. This continuity is what makes science possible. It means that – barring a supernatural miracle which would be temporary – the laws of physics and chemistry do not change over time.
This is what allows us to predict eclipses, and also to compute when eclipses occurred in the past.
God has promised us that certain things will be in the future as they were in the past – this includes seasons and also the day and night cycle (Genesis 8:22). Thus, we have biblical reasons to believe that the day-night cycle was basically the same before the flood as after; it is part of the continuity God imposes on His creation.
The Four (Six) Seasons
Troy: You wrote “The Lord created a tilted Earth because this produces seasons.” The four seasons did not begin until the global flood.
Lisle: What Scripture states that the four seasons did not begin until the global flood? Of course, there isn’t any. Again, Troy simply makes a bald assertion without any supporting evidence. That’s not exegesis. On the contrary, there is compelling biblical (and scientific) evidence that seasons existed before the flood as we will examine below.
Troy: This is a common mistake of only reading the English versions and not knowing what the Hebrew word “seasons” means on the fourth day. It is so mankind will know times for gatherings and festivals. Not winter, fall, and so forth.
Lisle: Here Troy makes another false assumption. He has assumed that the reason that informed biblical creationists believe in seasons before the flood is based on Genesis 1:14. It isn’t. It’s a shame he didn’t bother to research this. In any case, there are both scientific and biblical reasons to believe in seasons before the flood.
The first stems from a natural, exegetical reading of Genesis 8:22. The context of this verse is the end of the global flood. God has just promised to never again flood the entire earth. Hence, he promises, “While the earth remains, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.” The Hebrews divided the year into six seasons, rather than just the four we use today: seedtime (spring), summer, heat (the hottest part of our summer), harvest (autumn), winter, and cold (the coldest part of our winter).
So, God mentions these seasons in Genesis 8:22 as something that had already existed, along with the day & night cycle. He did not say, “I am now creating something new: seedtime, harvest….” Rather, after promising to never again flood the world, he promises that these cycles of nature will not cease.
The implication is that they did at least appear to cease during the flood year. After all, there was no seedtime or harvest during the flood year. If the ark had been carried near the polar regions at any point, even day and night may have been difficult to track, and may have seemed to cease (e.g. as within the arctic circle).
Notice that God mentions these seasons right along with the day and night cycle – something that existed from creation (Genesis 1:5, 14). The implication of Genesis 8:22 is that the day and night cycle and the seasons were apparently interrupted by the flood, and God is promising that He will never again do that. These things will continue just as they did before the flood.
Scientifically, we have every reason to believe that there were seasons before the flood. Fossils of pre-flood trees show quasi-annual growth rings just like trees today that are due primarily to the changing seasons. Furthermore, the tilt of the earth is held constant due to the conservation of angular momentum.² Again, only an outside torque can change this, and therefore the flood could not.
Furthermore, earth’s tilt is a design feature: it maximizes the habitability of earth. If the earth were tilted significantly more, then the seasons would become extreme, making life difficult. If the earth were tilted less, then the habitable latitudes would be reduced (the equator would be hotter and the poles much colder).
Troy seems to have accepted secular claims without recognizing that they are anti-biblical. Secularists believe that all the planets originally had a tilt of zero when the solar system supposedly first collapsed from a nebula 4.5 billion years ago. This is because of the principle of conservation of angular momentum; the sun and all the planets should rotate and orbit in the same plane if they formed from a collapsing nebula.
But most planets are tilted. Thus, secularists have invented rescuing devices in an attempt to save their secular model from what appears to be evidence to the contrary. Therefore, they claim that many of the planets were struck by some enormous planetary body in the past, causing the planet to be tilted. The energy of such an impact would destroy all life on earth, so secularists believe this happened before life evolved on earth. They also believe that a large, Mars-sized protoplanet struck the earth, and that such material formed the moon. As creationists, we reject such stories in light of recorded history.
Troy: Autumn and winter signify death and burial.
Lisle: Where does the Bible say that? Where does the Bible even hint at such a concept? Or is this Troy again reading into the text what is not there? Biblically, the autumn harvest was a time of gladness and celebration, when the people finally were able to enjoy the fruit of their labor (Isaiah 9:3; Exodus 34:22).
Troy: Two things that were not part of creation until sin and the global flood.
Lisle: No death or burial before the global flood? Troy’s reasoning here is simply terrible – it is both arbitrary and inconsistent. He asserts that autumn and winter signify death and burial, for which I can find no biblical evidence. He asserts that there was no death or burial before sin and the global flood. There was no death before sin, but there was certainly death before the flood. Cain killed Abel long before the flood. Then Troy arbitrarily asserts that there would not be things that (came to) symbolize death before the entrance of sin and the global flood. But in fact, the Scriptures sometimes use sleep as a symbol of death (John 11:11-13; 1 Corinthians 11:30, 15:51; Daniel 12:2). And sleep did exist before sin (Genesis 2:21).
Troy: Asteroids impacting the earth to commence the global flood and cause a 23 degree tilt would not vaporize the surface and destroy all life because the fountains of the deep and rain from the canopy dissipated the heat.
Lisle: What calculation did Troy do to establish his claim that the “fountains of the deep and rain from the canopy” were sufficient to dissipate all the heat produced by an impact capable of torquing the earth’s rotation axis by 23 degrees? Of course, there are none. It’s another bald assertion. So let’s actually do the math to see how much energy would be released by such an impact, and how much energy could be reasonably dissipated.
A solid sphere has a moment of inertia I = (2/5)Mr2, where M is the mass and r is the radius.³ The angular momentum is simply the moment of inertia multiplied by the angular velocity: L = Iω. So, the angular momentum of earth is about 7×1033 kg m2/s, in the direction of the north pole. To rotate this vector by 23 degrees, we would need to add an angular momentum vector of [L(cos(23) – 1), L(sin(23))] which has a magnitude of L √((cos(23)-1)2 + sin(23)2) = 0.399 L, which is 2.8×1033 kg m2/s. In other words, an asteroid would have to deliver about 40% of earth’s current angular momentum to tilt the axis by 23 degrees.
For maximum effectiveness, the asteroid would have to hit at a glancing angle, so r = earth’s radius (6.37×106 m). And the momentum of the asteroid would be 0.339 L / r, which works out to 4.4×1026 kg m/s. That is, the product of the mass and velocity of the asteroid must equal or exceed this value in order to tilt the earth by 23 degrees. How much energy would this deliver? The minimum energy would be delivered by a slower-moving asteroid, which must therefore be very large in order to have such momentum.4 The largest asteroid in our solar system (by far) is Ceres, which has a mass of 9.1×1020 kg. Hence, its velocity would be 490 km/s, and the energy (½mv2) of the collision would therefore be 1.1×1032 joules, roughly the equivalent of 2.5 million billion hydrogen bombs.
Troy claims (without any mathematical support) that water falling from a vapor canopy along with the fountains of the deep can somehow dissipate all that heat. First, water falling from an alleged canopy actually makes the problem worse because it increases the temperature. When an object falls, its gravitational potential energy is converted into kinetic energy, resulting in heat. So that’s not going to help dissipate heat.
However, water itself can absorb a great deal of thermal energy because it has a high specific heat. So, could the fountains of the great deep refer to spots where water is vaporized, carrying some heat with it? It’s certainly possible. But is the effect large enough to dissipate the energy produced by an asteroid that tilts earth by 23 degrees? Let’s do the math.
The average temperature on earth is around 61 degrees Fahrenheit or 16 degrees Celsius. Water has a specific heat of 4,184 Joules per kilogram per Kelvin. So, it takes 4,184 Joules to raise 1 kilogram of water by 1 degree Celsius (or Kelvin), and hence 351,456 Joules to raise 1 kg of water from 16 degrees Celsius to boiling point. The heat of vaporization of water is 2,260,000 Joules per kilogram. So, to both heat and vaporize 1 kg of water starting at 16 degrees Celsius would take 2,610,000 Joules. The earth has about 1.4×1021 kilograms of water. Hence, to heat and vaporize all water on earth takes 3.7×1027 Joules. But, recall, the minimum energy delivered by an asteroid capable of tilting the earth by 23 degrees is 1.1×1032 Joules, which is thirty thousand times greater than the energy needed to completely vaporize earth’s oceans.
So, any asteroid capable of tilting the earth by 23 degrees would not only completely vaporize earth’s oceans, but that vaporization would dissipate less than one hundredth of one percent of the heat energy. The oceans would need to be vaporized 30,000 times to dump all that energy. Since there was obviously water on earth’s surface during the global flood, we can be confident that the earth was not impacted by an asteroid that tilted it its rotation axis by 23 degrees.
Working the problem in the other direction, what is the maximum amount an asteroid impact (or multiple asteroid impacts) during the flood year could change earth’s tilt axis? Since the oceans did not vaporize, the energy of the impact must be 30,000 times less than the one necessary for a 23-degree change in tilt. The momentum goes as the square root of energy. Hence, the maximum possible change in earth’s tilt axis due to asteroid impacts at the time of the flood would be only 0.13 degrees.
It’s easy to make sweeping qualitative claims with no mathematical support. But when we do our homework, such claims do not stand up to scrutiny. In the next installment, we will look at further details of Troy’s claims and see if they stand up to mathematical scrutiny. In particular, we will look at the rotation of the earth over time, and how this is affected by lunar recession, as well as asteroid impacts.
To be continued
- For the physics students who may read this and ask, “What about a change in the earth’s moment of inertia?” A redistribution of earth’s mass in the radial direction could change the moment of inertia, resulting in a different rotation rate while keeping the angular momentum constant – like a skater who spins faster as she pulls her arms in. But (1), the nature of gravity is such that the denser objects would tend to move toward the core, while the less dense objects move away from the core due to buoyancy. So, this would reduce the moment of inertia, resulting in the earth spinning faster – not slower as Troy has conjectured. (2) The effect is likely to be very small since the flood mainly involved plate tectonics on the crust, and perhaps some of the upper mantle.
- Although the magnitude of earth’s tilt remains nearly constant at approximately 23 degrees relative to the ecliptic, the direction of that tilt slowly precesses due to tidal interaction with the moon. This process is cyclic, but less than one fourth of a cycle has occurred since creation.
- Specifically, this refers to a sphere of constant density. The earth’s density increases somewhat near the core. But the approximation is sufficient for our purposes.
- The kinetic energy of an object is half its mass multiplied by the square of its velocity. So, a less massive asteroid has higher kinetic energy than a more massive asteroid of the same momentum. Hence, smaller asteroids (faster) would deliver more kinetic energy than our computation here.