Having recently fielded some objections to the local flood interpretation, I'll be evenhanded and field an objection to the global flood interpretation. A staple objection to the global flood interpretation is that it poses a double whammy: where did all the extra water come from, and where did it go?
Of course, flood geologists have devised theories about that. In the past, I've mentioned that if God reversed the process in Gen 1:9 (orogeny), that would flood the earth. Now I'd like to suggest a different mechanism.
Suppose God gradually made the moon pass closer to the earth. Not only would that produce higher tides, but based on the inverse square law, it could generate supertides. And if, after that peaked, God made the moon recess, that would lower the tides. A single mechanism could account for both rising and lowering sea levels. You'd have the same amount of water throughout, but its distribution would vary depending on which part of the earth was facing the moon at any given time. Now let's consider some objections to my hypothetical:
1. Would the gravitational force of the moon be too destructive? Likewise, would altering the lunar orbit have any disruptive effects on the solar system overall? For instance, would a shift in the lunar orbit have any appreciable effect on Mars? If so, would a shift in the Martian orbit have an appreciable effect on the Venusian orbit?
I lack the expertise to address that question. However, from what I've read, conventional astronomy believes the moon used to be nearer to the earth. Yet that didn't have a cataclysmic effect on the earth or the solar system. Even if you reject conventional astronomy in that regard, I'm discussing the theoretical consequences of the moon drawing closer to the earth.
2. On my hypothetical, the whole globe would never be submerged all at once. Isn't that a problem?
Not really. In the course of a solar day, the whole globe would be submerged as the moon orbits the earth and the earth rotates on its axis. Every day, land masses would be inundated by the supertides. That cycle would continue day after day for the duration of the flood. A serial deluge rather than a simultaneous deluge.
I don't think the language of Genesis rules that out. Moreover, that would drown all the land animals. So that would have the same effect as a simultaneous deluge.
3. This epitomizes all that's wrong with creation science. Young-earthers postulate ad hoc theories to rationalize Scripture. There's no direct evidence for their theories. They are only propounded to prop up the Bible.
To that objection I'd say several things:
i) There is indeed a temptation in creation science to resort to ad hoc theories. However, that's hardly unique to creation science. The theory of evolution is riddled with stopgap explanations. Consider how Richard Dawkins conjectures evolutionary pathways. Nine parts interpolation to one part evidence. Likewise, evolutionary psychology is notorious for imaginative explanations to account for various adaptations. Or Richard Lewontin's brazen admission that "We take the side of science in spite of the patent absurdity of some of its constructs…in spite of the tolerance of the scientific community for unsubstantiated just-so stories."
ii) But let's consider a few comparisons. Take a homicide detective who reopens a cold case. Suppose all he has to go on is the police report and coroner's report. He develops a theory of the crime. He doesn't have direct access to the crime scene or the body. That's long gone. Rather, his evidence is documentary.
Likewise, some medical scientists diagnose famous men from the past. What was wrong with Isaac Newton, Jonathan Swift, John Ruskin, and Abraham Lincoln (to name a few)?
They don't have a living body to examine, or a dead body to autopsy. They can't take blood samples or scan the patient. All they have to go by are biographical reports describing the symptoms of the individual.
By the same token, historians use ancient astronomical notices to construct a chronology.
It isn't necessarily special pleading to devise a scientific hypothesis based on documentary evidence rather than direct evidence. That is, in fact, a common practice.
iii) If God wanted to produce a global flood, why use the moon? It isn't quite natural and it isn't quite supernatural.
But as a matter of fact, some miracles are preternatural rather than supernatural. Coincidence miracles are case in point. They don't circumvent the natural laws, yet they are more discriminating than natural laws. God employs a variety of causes.
iv) My hypothetical fails to explain the constancy and duration of the flood.
I disagree. According to the account, the flood waters gradually rise until they crest, remain at that level for a time, then recede.
And that's what would happen of God caused the moon to gradually pass closer to the earth, stay at that distance for a time, then gradually recess to its original position. The approaching moon would result in higher tides, while receding moon would result in lower tides.