Illustrations Of Electrical Sparks From Memorie - Classe Di Scienze Fisiche, Matematiche E Naturali Ser.3:v.1:disp.1

Inside Penrose's universe – Physics World

Physics World

Inside Penrose's universe – Physics World

<b>Julian Barbour</b> thinks the ideas in Roger Penrose's new book are "implausible"

x

stop trying to find yourself and start creating yourself!!!!!!!!!!!!

Hello! Why did penguins evolve to have black feathers if they live in icy (mostly white?) locations? I understand them having a white tummy because when swimming they could be more difficult to identify by a predator swimming below them? Thanks!

Love your blog!

Hello! So, here's what I learned at uni:

the widely-accepted reason penguins have black feathers is the same reason they have white tummies, but backwards. When swimming, they are more difficult to identify by a predator swimming above them! You can see similar countershading in sharks and dolphins, and also on land animals like mountain goats and lizards. Overall, it helps to make animals less obvious when viewing from the side, because it reduces the obviousness of their shadow.

As to why penguins have black feathers in icy, mostly white, locations (on LAND), you need to consider why it would be good to be white in an icy, white location in the first place!

Mostly, it would provide camouflage, which would protect from land predators! However, penguins don't really have any significant land predators in Antarctica. There are no polar bears, or big snakes, or even foxes or coyotes in Antarctica, so the penguin won't benefit from being camouflaged on land. Basically, there's no "selective pressure" for them to be all white!

some penguin chicks, however, do have to worry about a few predators, so they have a little more camouflage than the adult penguins:

What's more, there are likely advantages to black feathers in a cold environment like Antarctica! For example, in the sun, dark feathers absorb more thermal energy, helping to warm the penguin and maintain their body heat.

There may also be some stuff with black feathers being more resistant to wear/ friction drag in the water, but that's entering the realm of ongoing research, which I won't get into here.

Let me know if there's anything that needs clarifying!

(some citations if anyone wants further reading:)

Bonser, R. H. (1995). Melanin and the abrasion resistance of feathers. The Condor, 97(2), 590-591.

Ksepka, D. T. (2016). The penguin's palette--more than black and white: this stereotypically tuxedo-clad bird shows that evolution certainly can accessorize. American Scientist, 104(1), 36-44.

Rowland, H. M. (2009). From Abbott Thayer to the present day: what have we learned about the function of countershading?. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1516), 519-527.

Zagrai, A., & Hassanalian, M. (2020, July). Penguin coloration affects skin friction drag. In 2020 Gulf Southwest Section Conference.

The limits of my language means the limits of my world.

-Ludwig Wittgenstein

The Myth of Dreamless Sleep

Consciousness never "switches off" because it isn't generated by the brain. Its sensory inputs can be switched off - during sleep or general anesthesia, for instance - but your consciousness is still there. For example, a small but consistent number of patients report out-of-body experiences (OOBEs) or near-death experiences (NDEs) while under general anesthesia. As someone with REM Sleep Behavior Disorder (RBD) I can attest to this, since I act out dreams that occur during the non-REM phases of sleep.

ScienceAlert

We Were Wrong About Consciousness Disappearing in Dreamless Sleep, Say Scientists

When it comes to dreamlessness, conventional wisdom states that consciousness disappears when we fall into a deep, dreamless sleep.  But res

Books and bookmarks

Some downloaded files on interesting topics, I keep these in my phone in case I forget my book!