Guide of the Perplexed I:67:
It is possible that the word va-yanah is derived either from yanah, a
verb of the class pe-yod, or nahoh, a verb of the class lamed-he,
and has this meaning :" he established" or" he governed" the
Universe in accordance with the properties it possessed on the
seventh day" : that is to say, while on each of the six days events took place contrary to the natural laws now in operation
throughout the Universe, on the seventh day the Universe was
merely upheld and left in the condition in which it continues to
exist.
Guide II:30:
The following point now claims our attention. The account of the
six days of creation contains, in reference to the creation of man,
the statement :" Male and female created he them" (i. 27), and
concludes with the words:" Thus the heavens and the earth were
finished, and all the host of them" (ii. 1), and yet the portion
which follows describes the creation of Eve from Adam, the tree
of life, and the tree of knowledge, the history of the serpent and
the events connected therewith, and all this as having taken place
after Adam had been placed in the Garden of Eden. All our Sages
agree that this took place on the sixth day, and that nothing new
was created after the close of the six days. None of the things mentioned above is therefore impossible, because the laws of
Nature were then not yet permanently fixed.
In the light of the Rambam’s statements above, the following [supplied by Rabbi Moshe Meiselman] is very interesting:
In 1939, Paul Dirac wrote, “At the beginning of time, the laws of Nature were probably very different from what they are now. Thus, we should consider the laws of nature as continually changing within the epoch, instead of holding uniformly throughout space-time.”[1]
[1] Dirac, Paul “The relationship between mathematics and physics” Proceedings of the Royal Society (Edinburgh) 59 122-129.