How can we know how old fossils are?

[Anomalocaris]

Thnk about this, water they say causes decay of rocks, well how do we know that there weren't great floods that altered how old we think those rocks are? We also don't know for a fact the atmospheric conditions throuhgout history, so even though we can determine how rocks age in the present in our lifetime, we can know that something turns into something over 10 years persea, how can we know it changed to this degree over millions and millions of years not knowing the atmospher? Also if rain causes rock decay and water does, then that alters how old we think it is, in another words, if the water makes it older than it isn't really older. Does this make you think maybe science isn't all that accurate and those supposed evolutionary bones may not be old at all but different creatures just popping up around the same time? How can geology explain this?

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Does rock decay and weathering disprove rock dating and other forms b/c it's decaying from atmosphere and not natural and how can we know which is which?

You brought up some valid points.  There's nothing wrong with asking how scientists do things. If they have something other than divine revelation to back them up, they will welcome questions.

I may be wrong, but you seem to be proffering Noah's flood as an explanation for the apparent aged look of the rocks of the earth.  I'm no scientist, but I know they dom more than just look at a rock and decide that it looks old. Water may account for  wear and tear. However, it has nil effect on the decay of carbon 14  atomsin rocks that scientists use to date them. Your argument would hold water (pun excusable) if scientists were just looking at how old rock looks. Carbon 14 are carbon that have 14 neutrons.  

You must have at least a rudimentary understanding of carbon dating before you decide scientists don't know what they're talking about.

Actually, carbon 14 has 8 neutrons.   All carbon atoms have 6 protons.   It is the presence of exactly 6 positively charged protons in the nucleus that is responsible for defining the electron configuration of the neutral carbon atom and from that the chemical properties of carbon atom.   It is those specific chemical properties that make carbon carbon.

Different varieties of carbon atoms all have essentially the same chemical property, but their atomic nuclei have different masses.   All atomic nuclei consist of some mixture of positively charge protons and neutral neutrons of very similar mass. All carbons have 6 protons, but those with mass 14 (ie carbon 14) have 14-6=8 neutrons, while the much more common (and non-radioactive) carbon 12 have 12-6=6 neutrons.

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Rifht. It's used for dating the fossils (organic marerial) in rock? The next question is what is meant by decay? I'd think this is different from the physical wear and tear of water on rocks. I think I'll leave t hat question to those who know more than I do.

There is no organic material in dinosaur fossils. They've been replaced by minerals.

Intriguingly, that does not appear to always be true.   Organic material has been recovered from Cambrian marine fossils preserved in very fine grained sedimentary rocks.   Many of the fossils of soft bodied animal forms, as well as some hard shelled arthropods, were preserved as impressions in very fine grained marine sedimentary rocks.  Many of these fossils have dark colored discoloration around them.  It has been shown these discoloration are actually a very thin layer of carbon from the original soft tissues of the animals that oozed out of as the animal’s body was compacted by the sedimentary process.

So organic material definitely can and do survive fossilization.   But much more stunning is fact that actual original soft tissue appeared to have survived inside some fossilized dinosaur bones.    Some tyrannosaur femurs were found to have only fossilized part of the way through the bone.  The interior of the bone was not only not mineralized, there were even what appeared to be extremely well preserved soft bone marrow tissue as well as blood vessels with blood cells inside in vasculated parts of the bone.  Unfortunately this was only recognized part of the way through the conservation process, by which time the conservation process, while preserving the texture and form of the soft tissue remains, destroyed any possibility of DNA recovery. 

However, there was never any possibility of carbon 14 dating because the dinosaur bones were simply too old for any meaningful analysis of carbon 14 to decay daughter element analysis.