Can you tell me please how long the days in Torah/Genesis are, and the supporting evidence, reasons for your answer? Can you also refer me to a Hebrew scholar who can explain the use and the meaning of the word "day", or "yom" in the first book of the Torah? many thanks in advance!
It's important to stress that the Torah is not a history book, nor a science manual, and therefore when such information is purposely vague, that’s the real answer: we don’t really care how long the days were. If a certain generation has reason to think that the theory of evolution is true and that each day of creation maybe took millions of years, we can fit that into the Torah, and if science ever thinks that it can conclusively prove otherwise, we’ll be able to fit that into the text, as well. The Talmud teaches us that the real meaning of the story of creation can only be taught to individual selected adult students (Chagiga 11b), which infers that it’s clearly not simple and literal.
The term “yom” or day throughout the Tanach refers sometimes to the 24 hour unit (called in the Talmud (Brachot 3a) and in modern Hebrew: y’mama, from the same root as “yom”), and sometimes just to the light half (as opposed to the night), as is clear from both usages of the term in the fifth verse in the Torah: "And God called the light: ‘day’ (yom) and the darkness: ‘night’, and it was evening, and it was morning, (together=) one "day" (yom)." In short, you always must look at the context. Nevertheless, in the creation, it may be otherwise (for the sun and moon were only created on the 4th day, so obviously it’s may be understood differently). There are other contexts in the Tanach, as well, for example: “for 1,000 years is in Your eyes is like one day…” (T’hilim 90,4).
Many of the classic commentaries deal with this issue here, I suggest studying Rabbi Samson Raphael Hirsch and the Malbim who often deal with the literal meaning of the word and its usage throughout Tanach.
With Love of Israel,
Rav Ari Shvat