Giant Impacts not Periodic

[CraigS]

An interesting article by Phil Plait on recent study which poses the question:
"Does the impact rate for asteroids and comets vary periodically with time?"

Plait says:

And now it looks like my thoughts are being supported: a new study finds no such pattern in the ages of craters, and concludes all the periods found previously are probably due to errors in the analyses.

The difference is that the author, {of the study above}, Coryn Bailer-Jones, used Bayesian statistical methods. This is different than standard statistics, and is less prone to bias due to uncertainties in age and size of craters. In using standard statistics, clusters in crater ages can always be found, but it’s hard to know if that’s just a random clump or has an actual physical cause — like flipping a coin 10 times and having it come up heads 5 times in a row. It’s unlikely, but how do you know if it’s coincidence or not? Bayesian methods circumvent that issue.

Interesting also is Bailer-Jones words about Bayesian inference (similar to what was outlined in our thread about Speigel's paper about the probability of abiogenesis).

Bailer Jones says ..

Bayesian inference is not a cure-all for statistical problems. It has some subtleties of its own, notably concerning the proper choice of prior probabilities. For this particular task, that is, the analysis of time series data with different uncertainties (and, in some cases, upper age limits for a crater only), it is a highly suitable tool that allows well-founded statements about the different hypotheses under discussion.

Periodic variation in the cratering rate is strongly disfavoured in all data sets, and there is no evidence for a periodicity added to an underlying general trend. This result is found to be quite robust to the specific assumptions about the priors.

Oh … and yes .. the conclusions:

i) We’re not bombarded every 60 million years (or whatever)... it was simply an artifact of the way the math was being done.

ii) huge craters, ones bigger than 35 km (21 miles) across — in other words, more likely to cause extinction-level events — there is no trend in the rate of impacts over the past 400 million years.

iii) for craters of all sizes (not just big ones), there is a trend of increasing rate over the past 250 million years. Are we getting hit more by smaller objects now than we were in the past? … Not necessarily .. there are other possibilities ....

Interesting !

Cheers

[renormalised (Carl)]

This post has less to do with impact cratering than it has to do with your belief about Bayesian statistics (and, ultimately, chaos theory).

Craig, I'm getting sick and tired of these posts of yours lately that are out to look for nothing but controversy. All you're doing is pushing your own little barrow here about a theory (or methods) that have become a bee under your bonnet. Instead of looking for articles to use to push your pet ideas, find some we can all enjoy reading without them degrading into pointless arguments. These debates are becoming tiresome and annoying. That's all I'm going to say on this matter.

[xelasnave]

Carl dont let it upset you....and to hold your resolve not to say more on the matter would be perhaps a good approach if it continues to annoy you...

Thanks Craig its new to me and presumably others.

Thank you for taking the time to find material to provide content here... it is not easy to find new stuff I guess otherwise we would have many new threads each day...

best wishes to all and let peace and calm guide your thoughts and actions.

alex

[renormalised (Carl)]

I'm just tired of people pushing agendas, Alex. This is not a forum for pushing agendas. I've made my point of view very clear in other threads. I'm not going to repeat myself here.

[CraigS]

I have only one agenda … to explore and learn as much as is possible.

I only hope that others are interested in the same.

[xelasnave]

Originally Posted by renormalised

I'm just tired of people pushing agendas, Alex. This is not a forum for pushing agendas. I've made my point of view very clear in other threads. I'm not going to repeat myself here.

Yes I can understand how you feel Carl but agenda pushing is what humans do best ...I just dont like to see you upset.

If we have a particular interest..say gravity for example.. it may appear to others we are obsessed about that interest and pushing a particular idea whereas I suggest it is more a matter of sharing with friends ideas you think they will find as interesting as you find them.

I am thick so I havent noticed any friction but when I do it really upsets me when I perceive such...

Thanks for taking the time to comment have a great day.

alex

[xelasnave]

Originally Posted by CraigS

I have only one agenda … to explore and learn as much as is possible.

I only hope that others are interested in the same.

Well Craig in spite of my obsession with how gravity works that is where I come from.

I am fortunate to have folk around me who hold very strange ideas and determined to convert others and so I have learnt not to argue...which is strange..arguing is a joy for me.

When I became more relaxed I realise these folk are only trying to share something with me... because I seem interested they seek me out to let me know of their latest idea...planet x arrives in June..whatever... but I see it as a good thing as they see me as a guy who they can confide in... so rather than feeling trapped I feel special to be in these folks confidence and trust.

So as I have suggested many times we create our reality to a large degree by how we classify what is going on....

alex