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fms.fossils

Here was a lucky little find from today’s fossil hunt on Charmouth beach. This is a pyrite ammonite of the species Echioceras raricostatum. They are preserved in very soft shale, as you can see, which means that they come out in one piece very easily. Usually, the sea pulls them out of the rocks and dumps them on the beach. This can easily damage or destroy them. This one has a thin calcite shell on top of the pyrite which would have been removed by the sea almost instantly if it had got to it before I did. This fossil is around 196 million years old.

Map of US National Parks

Heather Nesheim  -  https://www.etsy.com/es/people/heddarsketch  -  https://twitter.com/heddarsketch

A short note on how to interpret Fourier Series animations

When one searches for Fourier series animations online, these amazing gifs are what they stumble upon.

They are absolutely remarkable to look at. But what are the circles actually doing here?

Vector Addition

Your objective is to represent a square wave by combining many sine waves. As you know, the trajectory traced by a particle moving along a circle is a sinusoid:

This kind of looks like a square wave but we can do better by adding another harmonic.

We note that the position of the particle in the two harmonics can be represented as a vector that constantly changes with time like so:

And being vector quantities, instead of representing them separately, we can add them by the rules of vector addition and represent them a single entity i.e:

                                                  Source

The trajectory traced by the resultant of these vectors gives us our waveform. 

And as promised by the Fourier series, adding in more and more harmonics reduces the error in the waveform obtained.

        Have a good one!

**More amazing Fourier series gifs can be found here.

Zany zebra facts: 1) Each zebra has a unique stripe pattern—no two are alike. 2) A zebra’s eyesight at night is thought to be about as good as that of an owl. 3) Zebras have a pad of fat under their mane that keeps it standing straight up.

Thanks to Todd Lahman for the stunning shot of Zari the zebra.

whiskies

Top Shot: A Lion’s Gaze

Top Shot features the photo with the most votes from the previous day’s Daily Dozen, 12 photos selected by the Your Shot editors. The photo our community has voted as their favorite is showcased on the @natgeoyourshot Instagram account. Click here to vote for tomorrow’s Top Shot.

Your Shot photographer Pratha Narang photographed this lion after a buffalo hunt. Your Shot Producer, David Y. Lee writes, “Fantastic portrait of this magnificent animal. I agree with Your Shot photographer Jiawei L. who commented, ‘This is such an intense photo! I love the frame gives me an opportunity to look through the blur branches and finally reach the eye of the lion. It is such an intense spot!’” Photograph by Pratha Narang