Question: How many days would there be in a week if telescopes had been available thousands of years ago?

Aside from clock units (hours, minutes, seconds) the week time unit appears not to have been based on astronomical observations made by ancient humans thousands of years ago. A biblical explanation taken on faith says God made the Earth and everything connected with it in six days - and then rested on the seventh day. This explanation requires no analysis and little thought. It is accepted obediently on faith, that if the Bible says so, it must be so and is not subject to challenge. But blind faith is never accepted in science where ideas are routinely reviewed, challenged and sometimes overturned by curious and challenging peers in science or philosophy or other areas.

The month time unit was originally based on the moon's phase-change period of 30 days separating one full moon phase from another. The month used to be called a moonth, but this was too bovine an expression for finicky humans, so moonth became month. It actually takes 30 days for the moon to orbit once (roughly) around the Earth.

The day time unit was and still is based on how long it takes the Earth to rotate once about its axis as measured by the sun, from one 12 o'clock noon to the next noon. The 24-hour day conceivably could have originated from the number 24 being one that could be divided by many other numbers for purposes of dividing work shifts 'round the clock on individual, social, or community projects. These are 12 two-hour shifts, eight three-hour shifts, six four-hour shifts, four six-hour shifts, three eight-hour ones, and two 12-hour shifts.

The year time unit derived from the 365 1/4-day period it took for each constellation (star pattern) to reappear in the same part of the celestial sky as they seemed to move in orbit around the Earth. However, we now know that this phenomenon is due to the Earth advancing slightly more than one degree every day as it orbits the sun - giving us a 365 1/4-day year.

If we ignore rotation (the Earth spinning about its axis - an imaginary line connecting the North and South Poles and running through the Earth's center), it is the Earth's actually taking 365 1/4 days to orbit the sun once, which gives the illusion of the constellations circling the Earth. The constellation doesn't move, but the Earth does.

In truth, the week also has an astronomical explanation. Its seven days were originally based on naked-eye (non-telescopic) observations by ancient humans of seven bright objects in the sky that seemed to move through the constellations throughout the year, as though visiting one after another. These seven appeared to have special magical powers that stars in the constellations lacked.

The constellations were thought to be bears, dolphins, humans, Kings, Queens, dragons and other fanciful forms. The seven star-like objects that seemed to pass through or near the constellations were thought to be the most important and powerful gods and goddesses - who each must be honored more often on special days than the lesser gods. The magnificent seven were the sun and the moon and the five planets visible to the naked eye without a telescope: Mercury, Venus, Mars, Jupiter and Saturn. These were to be honored and prayed to on seven successive days which repeated continually one after another.

Sunday was obviously the sun's day, and Monday was the moon's day. Tuesday (Mardi in French) was Mars' day to receive special worship, and Wednesday (note how it is spelled vs. how it's pronounced) comes from Wodin's day in some Scandinavian languages), but in Spanish and French, Wednesday was Miercoles and Mercredi respectively - named for the god and planet Mercury. Thursday (Thor's day in some Scandinavian languages) was Jovedi or Jove's (Jupiter) day in Italian.

Friday was Fria's (Scandinavian) day which was Viernes in Spanish (Venus' day), and Saturday naturally is named in honor of the planet Saturn, an earlier race of gods.

The number seven is considered lucky in dice. There are seven different notes in a musical octave, which begins and ends with DOE. The number seven in the film Seven Wives for Seven Brothers was also derived from the seven bright celestial objects moving through the constellations.

Finally, the answer to the question asked at the beginning on how many days would a week have if telescopes had been invented millenia ago? The answer is 10. Uranus, Neptune and Pluto were not discovered until 1786, 1846, and 1930 respectively. History and science are to me more interesting than fiction; but fiction is more remunerative.