So, this is the obvious one. The ark measures 300 cubits by 50 cubits, by 30 cubits (Genesis 6:15). A cubit is not the most precise measurement. Many ancient cultures used them, each with their own version of how long it was. Most used a human measurement, somewhere between the length of the forearm measure from the elbow to the tips of the fingers, or from the elbow to the wrist. The Biblical cubit is generally thought to be roughly 18 inches. The Egyptian cubit is longer, but not by much, and since this is a biblical story, we’ll stick with 18 inches (mostly because it makes the math easier. This puts the ark at around 450 feet by 75 feet, by 45 feet.
Now, this is an amazingly small size for a boat by modern standards. The RMS Titanic clocks in at 882 feet by 92 feet by 113 feet (the height to the top of the smoke stacks is 175 feet, but we want usable area). This makes the Titanic easily twice as large as Noah’s ark, but the Titanic could only carry 2200 passengers. While some of the room is lost to suites and dining areas, people take up far less room than most animals.
So how can Noah’s ark have carried two of every animal on the planet? Simple. It couldn’t. The math simply does not add up. It can’t be done. Moreover, the decks would have a maximum height of 12 feet (to accommodate overhead timbers), which does not accommodate larger animals such as elephants, to say nothing of the poor giraffes. Moreover, there are thousands of species of animals that must be accounted for. Even if we exclude animals from Australia and other exotic regions, there are thousands. Not one thousand or even two thousand, but several thousand. There simply isn’t room on the ark.
We also have to complicate the issue. Animals require food. Lots of it. The Titanic’s voyage was only to last a week to get from Ireland to New York City. It would have certainly had extra food and storage space, but not a lot of it. Noah, meanwhile, had to survive the 40 days of the initial flood. After 150 days, the flood waters receded, and on the 17th day of the 7th month (approximately 237 days), the flood had receded enough for Noah to find dry land. In all that time, Noah would have had to feed the animals. He was commanded, specifically, to take all the necessary food for them, too.
The amount of food required for the animals would exceed even the largest cruise ships, such as the Oasis of the Seas. A US aircraft carrier typically carries enough supplies and equipment for 5000 sailors to last 70 days, to say nothing of the 227 days Noah’s family would need, nor is there enough time for them to feed all of the animals. There are only 8 people on the ark, not enough to tend to the thousands of animals.
On the more disgusting side of things, he would also have to dispose of the waste from all of those animals, which would be patently impossible. Again, the issue of manpower and the volume of produced waste would become an issue. Modern waste disposal is not a feature of Noah’s ark.
With all of these logistics throwing off the story, many people would immediately conclude the story can’t be true, but there is something else to be discussed, the animals themselves.