Dinosaurs may not be as ancient as we think

Because the rate at which unstable isotopic elements decay & break down into simpler ones is well know. This is why isotopes are sometimes called nature's clocks.

By measuring the amounts of undecayed isotopic material & measuring the amount of the material created from the decay, a ratio can be found. Given the known half-life of the isotope, this ratio can be used to calculate the time that's passed since the isotope was first formed.

That's the best I can do from my imperfect knowledge of the subject & if you want to know more, you'll have to do some reading.

Ok, I understand that. 

Sometimes, you have 6 different ways to date a rock, with the decay rates of different isotopes not only being different, but being related to fundamental constants in different ways. When they agree to within around 1% (as they do) you can be sure you have a valid method of dating rocks.

Only evolution deniers refer to this. Literally no scientist would ever rely on C-14 in connection with evolution that has taken place outside of the last 50,000 years, which is pretty much all of evolution. Ignoring all scientific discussion gives you an incorrect impression.

@varelse1 is correct.  The setting depicted in Job is the patriarchal period in Genesis (time of Abraham, etc.) after Noah

None.  Leviathan and Behemoth were mythical "chaos creatures/monsters" in Ancient Near East (ANE) literature including the book of Job (where "chaos" is the unordered, primeval state of the "cosmos" in ancient understanding).  Trying to read modern terms back into the biblical text results in misinterpretations (specifically, anachronisms) and is hermeneutically unsound.  Behemoth and Leviathan would not have been understood as dinosaurs.  More important for understanding the book of Job is to understand the lesson that is trying to be taught by the reference made to Leviathan and Behemoth.  Job is compared to Behemoth and told he should emulate Behemoth and that the manner in which he thinks about Leviathan (NOT dinosaurs) is the same manner of respect and way he should think about Yawheh.  Asking what dinosaur it could be is asking the wrong question and missing the point and message of Job.

None of this pertains to dinosaurs or evolution but it does provide an answer to your question.

For more info see, How to Read Job by Old Testament and Ancient Near East expert John H Walton

Just for the sake of argument, what would you ( they ) understand Behemoth to be?

With a 'tail that sways like a cedar,' as i recall, cedars are a very stout type tree. Not easily swayed,so it must be speaking of an unusually large animal,reptile prehistoric dinosaur (!) or not so prehistoric!

And Jeremiah 10:1-5 MUST be talking about Christmas trees, right?  What else could it be? .  That's the problem with anachronism (reading 'out of time') and reading through a modern lens worldview.  It's the completely wrong context.  

It's not completely clear what Behemoth is (it's more clear what Leviathan is), but they certainly wouldn't have understood it to be a dinosaur, which were only discovered a few hundred years ago.  

Second, it's a poetic description, not a scientific description.  And it says it 'sways like a cedar'.  It doesn't say it's tail is as large as a cedar.  I don't know why people keep missing that.  That could simply be a description of any sized tail that's motion reminded of the motion of swaying trees in the wind.

Third, the description in Job 40 can't be harmonized with any known dinosaur anyway.  Job 40 says about Behemoth:

"Under the lotus plants it lies,
    hidden among the reeds in the marsh.
22 The lotuses conceal it in their shadow;
    the poplars by the stream surround it.
23 A raging river does not alarm it;
    it is secure, though the Jordan should surge against its mouth."

We know of no dinosaurs that lived in the Jordan River among the lotus and poplars!

Leviathan is more clearly understood.  Leviathan was believed to be a chaos creature in the ANE mythos.  

In Isaiah 27 we're told that in the future Day of the Lord:  

"In that day, the LORD will punish with his sword-- his fierce, great and powerful sword-- Leviathan the gliding serpent, Leviathan the coiling serpent; he will slay the monster of the sea"

Does it really make sense that in the future God is going to bring judgment against a dinosaur?

Because cedars were the most common trees in Job's area?  The point is it's a poetic simile.  It's a figure of speech, not a precise identification or description.  

If Leviathan is a dinosaur too and Job 41 is a literal description are we then to believe that dinosaurs had smoke coming out their nostrils and could breathe fire?

Acacia trees were also common.So why not say 'it's tail sways like that of an acacia tree?' The point being when the bible offers a precise description ( from the photos i've seen of cedars, they are a reasonably large tree) i can't help but believe the Lord is trying to get our attention and convey a specific message, something unusual, something big. Along the lines of my question to you on 'rachaph' ( Gen c 1 v 2). Are you aware that is the only place in the entire OT that translation of the word 'moved' is used? The word(s) move and moved are used approximately 59 times in the OT, yet 'rachaph ' is used only once.... Very much like a 'Truly truly I say unto you'.. from Jesus in the NT.

But let's see what else he says about behemoth

His bones are like tubes of bronze-large, perhaps unusually large in size and strength to support such an animal / creature.

Limbs like rods of iron - again strong legs maybe even considerable diameter to support a massive body size.

A very muscle toned belly ( Strongs gives 'body' as another translation for belly ) so i think it's fair to say this was strong, muscular type animal / creature typical of most larger animals we see in nature today.

And yet it was a herbifore -it didn't eat meat.

Strongs gives hippopotamus or elephant as 'possibly ' being behemoth. I don't think either pass the grade if for any other reason neither has a tail described in Job. We also know it is not an ox, and probably does not belong to the bovine family. If this indeed the case this animal /  creature is probably extinct, it is no longer living. What other type animal of this size could it be... that is or isn't extinct?

For me, the real clincher is he was made along with Job a direct reference back to Gen ch 1.Behemoth ( more likely his grandparents perhaps a few greats could be included ) was probably one of the 'creatures' that came forth from the ground ( v 24). The Hebrew for 'made' here is 'asah' - to make or bring forth, so Behemoth was an actual living creature / animal. ( #6213 S-CC)

Earlier this morning i briefly researched dinosaurs in Israel and found one they call 'ostrich' type.The Hebrew Univ has it's footprints -  found in 1962 Beit Zayit -  and are on display.

It's a two legged dinosaur with a reasonably large tail.It's prints would be similar to our index,middle and ring fingers spread about an inch a part. Unfortunately these sites are literally in Israel and require a fee for the full story so am limited on information.

So, being a scientist with seemingly having access to information i'm not ( thanks for sharing CIBI, not aware of it before ) unless you can come up with some animal / creature the size Job describes that is now extinct or living in some deep dense jungle, i'm not so sure this can easily be dismissed.

The dinosaur interpretation can be dismissed because it's anachronistic and also because dinosaurs are extinct and also because no known dinosaurs ever lived in the Jordan River among the lotus and poplars and once again because this is poetry that employs poetic similes that cannot be taken as precise descriptions anymore than Leviathan can be understood as a fire breathing dinosaur and also because we have no evidence that dinosaurs and humans ever lived together much less in 2300 BC and we have no evidence that dinosaurs were even alive 2300 BC around the time of the patriarchs when Job lived and we have no evidence that they even knew about dinosaurs---the original readers of Job would not have understood Behemoth to be something they didn't know about and only we know about, again that's why it can't be dinosaurs because that's an anachronistic misreading of the text.

 And the dino footprints discovered West of Jerusalem you refer to are one of the few known dino evidence in the Middle East.  The footprints are also in Cretaceous rocks >66 million years old.  You also can't determine tail size directly from footprints but can only estimate it along with height of the dino and as you said it's ostrich like in size and the only reconstruction I've seen does not have a cedar-sized tail.  But more importantly IF someone in patriarchal times around 2300 BC discovered such footprints of a dino that had long been extinct over 66 million years ago there is NO possible way that they could come up with the description of Behemoth in Job 40 from a set of footprints that to them would look like the footprints of a large bird, not a marsh-dwelling beast.  

It never hurts to keep digging.  In fact, it's always a good idea.

Really, my apologies.I've deleted it...but will keep on digging!

???  You lost me.  Did you say something offensive or derogatory?  I honestly must have missed that.  I wasn't offended by anything you said. 

No, nothing offensive or derogatory towards you. more so for challenging you ( last paragraph ) as i did in #91.

Not sure why i was feeling so impressed with myself.....

https://www.nationalgeographic.co.uk/history-and-civilisation/2021/06/these-historic-underwater-beasts-inspired-fear-superstition-and-scientific-searches?utm_source=pocket-newtab

Perhaps the biblical Leviathan is amongst the lot.....Who knows, only the shadow knows......

Again, probably not other than in a mythic or metaphorical way.  Leviathan is more akin to our mythic Godzilla from the mythos of our culture--a fire-breathing monster that cannot be tamed that emerges from the depths of the sea and causes chaos and wreaks havoc.

https://getpocket.com/explore/item/the-brontosaurus-is-back?utm_source=pocket-newtab

Behemoth has finally been revealed.

It's not just this particular ancient text. Recently it has been discovered that the famous "72 virgins" in the Quran was the result of the mistranslation of an ancient word for raisin similar to one for virgin. A Freudian slip?