No, the Age of the Universe is not a guess, we can see that via the Speed of Light.
The Age of Man can not be known by Scientists, because they have NO IDEA when God placed His Spirit into mankind or Adam. So, an Animal like man, with no Intellect, is NOT a Human Being with the impartation from God via His spirit giving Us an immortal spirit or soul.
We can know the Age of men because God tells us, and we can see when all the snoop dogs (Record Keepers, LOL) or records started being kept. All started about 6000 or so years ago, men just didn't suddenly gain intellect, God just suddenly imparted His spirit into clay creatures made of dirt. (us human beings then came into being 6000 or so years ago, and then God RESTED from His CREATION).
We have no idea...
We don't know... you are stating things as fact which no one else will.
Because of the basic rules of science is correlation is not causation.
Then on top of this there is a time dilation effect as you move off into deep space. Basically, time stops as you leave this solar system. And they have no idea as to how this time dilation has an effect upon waves. Which would be crucial for any sort of time accounting.
So basically they have thrown up their hands and said "We Don't Know".
And then we have the Leverite calendar. It's around 5,600-5,800.
But if you read the Bible it was started at the Exodus...aka Passover. Which the Israelites had already been in Egypt for 480 years by that point.
How much time before then did mankind run about?
The Bible doesn't really say. Those "begat" lists are not saying anything about that...they say something completely different. And they are not something that is going to be capable of structuring a timeline over. That's not what they are for. But our translation traditions keep us from understanding what they do say.
So I'd dare say that we had been running around for several thousand years before the flood, a few thousand after the flood...and a good bit of time before Abraham took his journey West. Possibly Abraham talked to Shem...but scripture doesn't say that either.
PHD Michael Schneider is a calendar historian for Levitical calendars. (An acquaintance of mine). Written several books on the subject. Arguments with him were always fun and interesting...and always loud but respectful.
But he takes his calendars seriously. And even he tells me that we really don't have a clue. We know the biblical record but the "wiggle room" inside the Hebrew is enough to drive a tractor trailer parade 5 wide through.
(Meaning give or take a few dozen thousand years at any given point pre-flood or post flood)
Even though Mike and I argued all the time...we actually liked each other...and I know Mike's credentials and sincerity...a stranger on the internet? His are going to be suspect from inception and ongoing.