he later stated that there was no way to test out each item and each way they interact with another item, as it was virtually impossible for them to accomplish this, using an example of an airplane being frozen, brought back in time, placing an old man on top of it, bringing it back to present time, and setting it on fire. much of the theory can be developed in this abstract and very general setting. his last paper, published the year of his death, examined the heat released from chemical reactions. this species grows to a maximum standard length of . 