estimates
Science does not claim to provide absolute truths, that is religeon.
Assuming you are referring to absolute proof, it is because absolute proof is scientifically impossible. It is always possible, however unlikely, that all collected data is coincidental, and that the complete opposite of what is expected may happen.
A banana cannot be used.
I don't think scientists have proof and I don't think scientists believe the world will end in 2012. 2012 if the end of the Mayan 5000 year calander.
evidence
yes, with satellites that is how they get proof
Scientists are skeptical about the Loch Ness monster because there is no solid proof that the monster exists. They will do nothing about it until there is some proof.
Absolutely. The mathematics on EinsteinElectricity.com are absolute proof.
There is really no absolute proof that Bigfoot even exists.
In a criminal case, the burden of proof must meet the standard of "beyond a reasonable doubt" to establish the guilt of the defendant.
It was at Versailles, and still is
No, scientists have not found any evidence or proof that mermaids exist. The concept of mermaids is largely based on folklore and mythology, rather than scientific observation or documentation.