Tag Archives: why

Why is the Sky Blue?

Here is a a nice post explaining why we see blue when we look at the sky, Why Is The Sky Blue?:

Most of the atmospheric gases are transparent to visible light. They don’t filter the Sun’s light and make it yellow, as a yellow filter would. Besides, if colored gases made the Sun appear yellow, where does the blue come from? The part of the atmosphere that changes the Sun’s light is the molecules and tiny particles that are floating in it.

There are particles of water–tiny droplets too small to be seen as clouds. There are particles of organic material–smog or haze, condensed from volatile organic chemicals that have gotten into the air. There are particles of sulfuric acid from volcanoes and power plants. There are molecules of gases in the atmosphere.

These tiny particles, much smaller than the wavelengths of sunlight, scatter the sunlight as photons from the Sun interact with the particles. This is called Rayleigh scattering after the British physicist who described how it works. (Larger particles, like the water droplets in clouds, are closer to the wavelengths of sunlight, and they scatter it differently. This is why clouds are not blue.)

Science explained – quick overviews of scientific concepts: How Does That Happen? Science Provides the Answer – Incredible Insects – 10 Science Facts You Should Know – What Everyone Should Learn – Science Summary: Photosynthesis – String Theory in 1 page – How do antibiotics kill bacteria?

Why do We Sleep?

Study puts us one step closer to understanding the purpose of sleep:

Sleep remains one of the big mysteries in biology. All animals sleep, and people who are deprived of sleep suffer physically, emotionally and intellectually. But nobody knows how sleep restores the brain.
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Although an electronic power-napper sounds like a product whose time has come, Tononi is chasing a larger quarry: learning why sleep is necessary in the first place. If all animals sleep, he says, it must play a critical role in survival, but that role remains elusive.

Based on the fact that sleep seems to “consolidate” memories, many neuroscientists believe that sleeping lets us rehearse the day’s events.

Tononi agrees that sleep improves memory, but he thinks this happens through a different process, one that involves a reduction in brain overload. During sleep, he suggests, the synapses (connections between nerve cells) that were formed by the day’s learning can relax a little.

Sarah, aged 3, Learns About Soap

A Dialogue with Sarah, aged 3: in which it is shown that if your dad is a chemistry professor, asking “why” can be dangerous [the broken link was removed] by Stephen McNeil.

DAD: Why does the soap grab the dirt?
SARAH: Yes.
DAD: Because soap is a surfactant.
SARAH: Why?
DAD: Why is soap a surfactant?
SARAH: Yes.
DAD: That is an EXCELLENT question. Soap is a surfactant because it forms water-soluble micelles that trap the otherwise insoluble dirt and oil particles.

Great. I remember such discussions with Dad (Chemical Engineering professor). The only danger I saw was him getting tied of -why? (when I was older). And sometimes giving me answers the teacher didn’t like (a way of doing math problems that wasn’t the way my teacher was teaching).

Related: Illusion of Explanatory Depth – Excellence in K-12 Mathematics and Science Teaching – What Kids can Learn – Science for Kids
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Illusion of Explanatory Depth

The “Illusion of Explanatory Depth”: How Much Do We Know About What We Know? (broken link was removed)

Often (more often than I’d like to admit), my son (Darth Vader over there on the left) will ask me a question about how something works, or why something happens the way it does, and I’ll begin to answer, initially confident in my knowledge, only to discover that I’m entirely clueless. I’m then embarrassed by my ignorance of my own ignorance.
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I wouldn’t be surprised, however, if it turns out that the illusion of explanatory depth leads many researchers down the wrong path, because they think they understand something that lies outside of their expertise when they don’t.

Great stuff. It took me a lot longer to stop asking why, why, why than most kids. I only gave up after years of repeated obvious clues that I was not suppose to ask why (once I aged past 5 or 8 or something – I actually have no idea when it is no longer desired). But most days I, curious cat, want to ask how does that work, why do we do that, why can’t we… I just stop myself. But it does mean I asked myself and realized I don’t really know. So I am at least more aware how little I really know, I think I am anyway.

The internet is a great thing. Google doesn’t mind if you ask as many questions as you want.

Related: Theory of Knowledge – Feed your Newborn Neurons

Energy Efficiency of Digestion

Why is Fecal Matter Brown?

The complex digestion process ensures that almost no useful energy goes unused. The average bowel movement is three parts water to one part solid matter. Bacteria make up 30 percent of the solid stuff. The same goes for indigestible foods like cellulose and extra fiber. The remaining 40 percent contains various inorganic wastes, fats and used-up body substances like red blood cells

Scientists Examine 100 Trillion Microbes in Human Feces:

Aiding the large intestine in this task are trillions of microbes that reside in the gut, where they help digest foods we would otherwise have to avoid. In this way the bugs contribute to our overall health.

Some of these tiny settlers are with us from birth, imparted from our mothers, while others gradually colonize our bodies as we grow. This microbial community is as diverse as any found in Earth’s seas or soils, numbering up to 100 trillion individuals and representing more than 1,000 different species.

Spider Thread

Spider hanging by its thread

Why a spider hanging from a thread does not rotate

The extraordinary properties of spider’s thread are like a blessing for researchers working on polymers. However, the amazing twisting properties it displays are still not very well understood. How can one explain the fact that a spider suspended by a thread remains completely motionless, instead of rotating like a climber does at the end of a rope?
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Spider’s thread, on the other hand, is very efficient at absorbing oscillations, regardless of air resistance, and retains its twisting properties during the experiments. It also returns to its exact original shape. Certain alloys, such as Nitinol, possess similar properties but must be heated to 90° to return to their original shape.

The amazing properties of spider’s thread have been known for several years: its ductility, strength and hardness surpass those of the most complex synthetics fibers

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