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I found a seashell in the middle of the desert

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Re: I found a seashell in the middle of the desert

#121

Post by fsckboy »

m463 wrote: post #115
My_Name wrote: post #94

One thing that will have thrown the author off the trail is that he is holding a fossil of the organic parts of the snail and that is essentially a cast of the animal, not the shell. They are known as Steinkerns (stonecore). The insides get replaced by minerals, which harden, the shell dissolves, then the only fossil remaining is a mould of the inside of what used to be the shell. So on a fundamental level, the headl…

I've been told by a friend -- a wierd thing -- in many places you can dig a hole and it will fill with water. And at some point in the future fish will be swimming in it.

with a "pond sized" hole, I have read that fish eggs arrive on the feet of ducks and other waterfowl attracted to the new pond. (I have never looked up whether this is a myth)

Re: I found a seashell in the middle of the desert

#124

Post by My_Name »

m463 wrote: post #115
My_Name wrote: post #94

One thing that will have thrown the author off the trail is that he is holding a fossil of the organic parts of the snail and that is essentially a cast of the animal, not the shell. They are known as Steinkerns (stonecore). The insides get replaced by minerals, which harden, the shell dissolves, then the only fossil remaining is a mould of the inside of what used to be the shell. So on a fundamental level, the headl…

I've been told by a friend -- a wierd thing -- in many places you can dig a hole and it will fill with water. And at some point in the future fish will be swimming in it.

[dead]

Re: I found a seashell in the middle of the desert

#125

Post by drzaiusx11 »

altcognito wrote: post #60
drzaiusx11 wrote: post #45

Earlier quoted context omitted.

Using PCA on 3d shapes is a proven method for identification. It's nothing like phrenology aside from both involving morphology. Former actually works, latter does not.

(I upvoted, seems a little weird that you were downvoted) So, I spent a little time looking up "Principal Component Analysis" and yeah, this method works well with these forms, and my comment comparing it to phrenology was definitely more out of ignorance! I was most surprised that you could flatten a 3d structure down to 2d and not lose so much information that it would cause a very high rate of error. Someone else…

PCA (using eigenvectors for dimensionsional reduction) is kinda like moving the axis from an x/y/z grid and onto the shape itself. So it's not 2d in the sense of a simple projection where the loss of information is greater. It has a lot of useful applications, 3d shape recognition is just one.

Re: I found a seashell in the middle of the desert

#126

Post by hbwang2076 »

My_Name wrote: post #94

One thing that will have thrown the author off the trail is that he is holding a fossil of the organic parts of the snail and that is essentially a cast of the animal, not the shell. They are known as Steinkerns (stonecore). The insides get replaced by minerals, which harden, the shell dissolves, then the only fossil remaining is a mould of the inside of what used to be the shell. So on a fundamental level, the headl…

The iterative narrowing approach works well for broad research queries.

Re: I found a seashell in the middle of the desert

#127

Post by IAmBroom »

fsckboy wrote: post #121
m463 wrote: post #115

Earlier quoted context omitted.

I've been told by a friend -- a wierd thing -- in many places you can dig a hole and it will fill with water. And at some point in the future fish will be swimming in it.

with a "pond sized" hole, I have read that fish eggs arrive on the feet of ducks and other waterfowl attracted to the new pond. (I have never looked up whether this is a myth)

There are also fish that can walk overland to find new ponds. Weird, but real, with obvious implications for the origin of land tetrapods.
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