The Oral Torah:

Since the Written Torah is ambiguous and difficult to understand, there had to have been more information given in Sinai. (Exodus 12 : 2) "This month shall be to you the head of the months; to you it shall be the first of the months of the year." To which months is this referring? Is it referring to Egyptian months (where the Jews were living at the time) or Chaldean months (from where our father Avraham originated)? Solar months or lunar months? Without an oral tradition, there is no way to know to what this verse is referring. (Exodus 16 : 29) "See that the Lord has given you the Sabbath. Therefore, on the sixth day, He gives you bread for two days. Let each man remain in his place; let no man leave his place on the seventh day." To what place is this referring? Does it mean his home, his property if he has more than one home, his neighborhood, his city, or something else? (Exodus 20 : 10) "but the seventh day is a Sabbath to the Lord, your God; you shall perform no labor, neither you, your son, your daughter, your manservant, your maidservant, your beast, nor your stranger who is in your cities." What exactly is labor, and what is not? Without the Oral Torah it would be impossible to know. (Deuteronomy 12 : 21) "If the place the Lord, your God, chooses to put His Name there, will be distant from you, you may slaughter of your cattle and of your sheep, which the Lord has given you, as I have commanded you"" but nowhere in the Written Torah were they commanded to slaughter the animal. (Exodus 24 : 12) "And the Lord said to Moses, "Come up to Me to the mountain and remain there, and I will give you the stone tablets, the Law (Torah) and the commandments, which I have written to instruct them."" This implies that more than the Torah was given in Sinai. (Zechariah 8 : 19) "So said the Lord of Hosts: The fast of the fourth [month], the fast of the fifth [month], the fast of the seventh [month], and the fast of the tenth [month] shall be for the house of Judah for joy and happiness and for happy holidays-but love truth and peace." Nowhere in the Tanakh is there a commandment to fast on those months. These passages show that more information had to have been in given in Sinai. There is also the argument that the Oral Torah contains information that, at the time, could only have been known through divine revelation. (Talmud, Rosh Hashanah 25a) "Our Rabbis taught: Once the heavens were covered with clouds and the likeness of the moon was seen on the twenty-ninth of the month. The public were minded to declare New Moon, and the Beit din wanted to sanctify it, but Rabban Gamliel said to them: I have it on the authority of the house of my father's father that the renewal of the moon takes place after not less than twenty-nine days and a half and two-thirds of an hour and seventy-three parts. (Rambam, Mishneh Torah, Kiddush HaChodesh, chapter 6) "Day and night are constantly considered a twenty-four hour composite, [on the average:] twelve [hours] of daylight and twelve [hours] of night. An hour can be divided into 1080 units. This number was chosen because it can be divided in half, into fourths, eighths, thirds, sixths, ninths, and tenths. Each of these fractions contains many of these units." If you do the math, you will see that according to the Oral Torah, the minimum number of days in the lunar cycle is 29.53059 days, which is only 1 or 2 thousandths of a second off from modern estimates.