The existence of these alignments is proof in itself that they knew these things. If they had advanced knowledge this is how they would encode things and this is how they did it. If these alignment happened every once in a while we can consider it as a coincidence. But taking all things into account like the ancient Gods – patriarchical civlizers with strange morphologic features, the Dendera light bulbs, the Abydos helicopters etc., then the alignment with the external planets which is ideal for encoding large units of time shows us that the architects of these structures were around for centuries – see time travel or traveling at speeds close to that of light. They could visit the Earth just the right time to supervise the construction of the pyramids. If someone intend to prove a certain alternative theory wrong we must either:
1) proof it is incorrect in it’s calculations or in the data
2) site alternative explanations which fit the observational information better.

The fact is though that Egyptologists have not the foggiest ideas of why the pyramids were built where they were – their distribution in Saqara, Giza , Abu Rowash, so they come up with simplistic explanations that nobody really believes. They don’t know why the particular base lengths were chosen , and why they are not always integer. Thus they conclude that the AEs worked hard for tens of years to create the largest structures ever built they didn’t think of measuring out an integer value for all of them based on a predefined standard royal cubit. This means that they conclude that each pharaoh used his own special royal cubit measure. They also don’t know how the distances and angles between the pyramids were planned. The claim that the only thing they took into account was steady ground or proximity to resources – Nile etc. But if this was true then what about the Bent pyramid? Why didn’t they choose the right ground conditions there? Mistake? Anyone can believe anything.

I have a simple theory that explains the dimensions and positioning of all ancient Egyptian pyramids. This is the proof that can stand up to scientific scrutiny like statistical analysis.

>>The metre, too, was first used in 1797 AD.<<
I presented proof on this mb that a unit of measure with length equal to the meter measure was used in ancient Sumeria, Egypt, and Hellas. No one disputed it(with facts).

>>And, AFAIAC, the alphanumeric alphabet that you keep citing just looks like a meaningless collection of numbers and letters.<<
The ancient Greek letters had a particular arithmetic value thus words had also particular numerical – integer values. This is a fact. You can consider the word number correlations as coincidences but you cannot dispute their ancient existence. Here too these “coincidences” can be studied statistically. Science does not allow us to speak of coincidences when we can compute the probability of an event to occur or not to occur.

>>for instance, that no one knew of the existence of the planet Neptune until the 19th century AD;<<
You don’t have to dispute every point of this argument because we have two possibilities:
1) a local culture on Earth built these structures. Then if we find that they encoded info about Neptune we would have trouble explaining it since they couldn’t have known about it’s existence. This is where you are coming from. But as I stated before:
2) a very advanced either a) earthly cultured from a destroyed very ancient civilization or b) or alien civilization designed these structure. In this case we cannot claim that they didn’t know about Neptune. Chances are they flew right by it. If they came to Earth at 2466 BC when the GP was built from a direction center galaxy – Earth then they surely passed by Neptune and Uranus.

This all means that the only thing you can do is:
1) prove aligns did not visit Earth in the past
2) find errors in my theory or site another theory alternative or orthodox that explains things better without introducing external variables – fudging things.