[Serious Discussion] Religion

[[SAE]Grim]

How could Mohammad know that the lowest land on earth is the dead sea area... the place where the romans have been defeated?

Nowhere did he say that the lowest land on earth is the dead sea area.

"It shatters the whole argument of the Muslims by informing us of certain varied readings in these verses of Suratu'r Rum. He tells us that some read (Arabic text appears here) instead of the usual (Arabic text appears here) and (Arabic text appears here) instead of (Arabic text appears here). The rendering will then be: 'The Byzantines have conquered in the nearest part of the land, and they shall be defeated in a small number of years'. If this be the correct reading, the whole story about Abu Bakr's bet with Ubai must be a fable"

Depends on how you "read" these verses. Specially about how many years it actually was.

"The explanation which Al Baizawi gives is, that the Byzantines became conquerors of 'the well-watered land of Syria' (Arabic text appears here) and that the passage predicted that the Muslims would soon overcome them. If this is the meaning, the Tradition which records the 'descent' of the verses about six years before the Hijrah must be wrong and the passage must belong to A.H. 6 at earliest."
"It is clear that, as the vowel points were not used when the Qur-an was first written down in Cufic letters, no one can be certain which of the two readings is right. "

"We have seen that there is so much uncertainty about (1) the date at which the verses were 'sent down', (2) the correct reading, and (3) the meaning, that it is quite impossible to show that the passage contains a prophecy which was fulfilled. Hence, it cannot be considered to be a proof of Muhammad's prophetic office."

So it's no real proof, just the way people read or translate the verses. This is done often, to translate a meaning into another so it fits with the story u want to tell.
Plus, people predict things all the time, and just because it happens doesnt mean God told you it first.