I would say that it remains the rotation of the earth as it is affected by the newly created light. However, I would be willing to allow for flexibility due to God’s sovereignty over all time and all dimensions. Nonetheless, I’d expect the proportion to be upheld.
And do you also expect the expression “40 days and 40 nights” to mean EXACTLY 40 days and nights?
It is a common expression from that area and era meaning “for days and days”.
Similarly when the Bible speaks of the “four corners of the Earth” it is not suggesting that the Earth is rectangular.
And when the Bible says that God created the foundations of the Earth so that they would not be moved, it doesn’t mean that the Earth does not move.
A “morning” and an “evening” of a “day” before there was even a Sun for there to be either morning, evening or daylight; in no way necessitates a twelve hour span.
Concerning the evening/morning issue, I thought y'all might be interested in Gerald Schroeder's comments:
The Talmud (Chagiga, ch. 2), in trying to understand the subtleties of Torah, analyzes the word "choshech." When the word "choshech" appears in Genesis 1:2, the Talmud explains that it means black fire, black energy, a kind of energy that is so powerful you can't even see it. Two verses later, in Genesis 1:4, the Talmud explains that the same word - "choshech" - means darkness, i.e. the absence of light.
Other words as well are not to be understood by their common definitions. For example, "mayim" typically means water. But Maimonides says that in the original statements of creation, the word "mayim" may also mean the building blocks of the universe. Another example is Genesis 1:5, which says, "There is evening and morning, Day One." That is the first time that a day is quantified: evening and morning. Nachmanides discusses the meaning of evening and morning. Does it mean sunset and sunrise? It would certainly seem to.
But Nachmanides points out a problem with that. The text says "there was evening and morning Day One... evening and morning a second day... evening and morning a third day." Then on the fourth day, the sun is mentioned. Nachmanides says that any intelligent reader can see an obvious problem. How do we have a concept of evening and morning for the first three days if the sun is only mentioned on Day Four? We know that the author of the Bible - even if you think it was a bunch of Bedouins sitting around a campfire at night - one thing we know is that the author was smart. He or she or it produced a best-seller. For thousands of years! So you can't attribute the sun appearing only on Day Four to foolishness. There's a purpose for it on Day Four. And the purpose is that as time goes by and people understand more about the universe, you can dig deeper into the text.
Nachmanides says the text uses the words "Vayehi Erev" - but it doesn't mean "there was evening." He explains that the Hebrew letters Ayin, Resh, Bet - the root of "erev" - is chaos. Mixture, disorder. That's why evening is called "erev", because when the sun goes down, vision becomes blurry. The literal meaning is "there was disorder." The Torah's word for "morning" - "boker" - is the absolute opposite. When the sun rises, the world becomes "bikoret", orderly, able to be discerned. That's why the sun needn't be mentioned until Day Four. Because from erev to boker is a flow from disorder to order, from chaos to cosmos. That's something any scientist will testify never happens in an unguided system. Order never arises from disorder spontaneously. There must be a guide to the system. That's an unequivocal statement.
Order can not arise from disorder by random reactions. (In pure probability it can, but the numbers are so infinitesimally small that physics regards the probability as zero.) So you go to the Dead Sea and say, "I see these orderly salt crystals. You're telling me that G-d's there making each crystal?" No. That's not what I'm saying. But the salt crystals do not arise randomly. They arise because laws of nature that are part of the creation package force salt crystals to form. The laws of nature guide the development of the world. And there is a phenomenal amount of development that's encoded in the Six Days. But it's not included directly in the text. Otherwise you'd have creation every other sentence!
The Torah wants you to be amazed by this flow of order, starting from a chaotic plasma and ending up with a symphony of life. Day-by-day the world progresses to higher and higher levels. Order out of disorder. It's pure thermodynamics. And it's stated in terminology of 3000 years ago.