Science Friday: Rain Bomb (Microburst) Over Phoenix | Science Still Doesn’t Know Why a Bike Stays Upright

[…]

Microbursts are spectacular but very dangerous downdrafts associated with violent thunderstorms such as the ones travelling across portions of the southwest US this week.

They are occasionally referred to as “inverted tornados” because they actually have the opposite motion of a twister (downward) and can cause surface winds well in excess of 100 mph, the equivalent of at least an EF1 tornado.

The two main mechanisms involved in the formation of a wet Microburst are precipitation and evaporation, with the first of the two having a greater effect on its intensity.

On occasions, a dry version of the phenomenon can form without precipitation reaching the ground, as water evaporates in higher levels of the atmosphere and evaporative cooling causes the denser air to flow downward as a strong draft. The diameter of these very intense downdrafts can vary, but it is usually less than 2.5 miles wide.

With the towering Cumulonimbus growing in size, large amounts of moisture are drawn into the cloud and water drops and hail begin to form and grow in size. When updrafts feeding the cloud get stronger, a tremendous amount of super cooled water droplets mixed with hail remain suspended in the upper portion of the thunderstorm.

[…]

https://www.theweathernetwork.com/us/news/articles/science-behind-the-awe-inspiring-microburst-over-phoenix/70377

I borrowed the title from 

http://tywkiwdbi.blogspot.com/2016/07/this-is-rain-bomb.html


The Bicycle Is Still A Scientific Mystery

A bicycle is surprisingly stable for an upright, two-wheeled vehicle that needs to be propped against a wall when it’s not moving. But perhaps a bigger surprise is that no consensus exists on why the bike is as stable as it is. For such a simple design, which almost anyone can understand, this seems crazy. After all, we live in a world of self-driving cars and safe passenger airplanes. Surely the bike can’t still hold any physics or engineering mysteries?

At the heart of the puzzle is something we’ve all observed. If you push a riderless bicycle, it balances itself, steering automatically to correct for any wobbles, until it slows down and finally falls flat on its side.

[…]

http://www.fastcoexist.com/3062239/the-bicycle-is-still-a-scientific-mystery-heres-why

The original article the above post is based on, is here

http://www.scientificamerican.com/article/the-bicycle-problem-that-nearly-broke-mathematics/

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