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John Murrin
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John Murrin

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This is a gigantic molten sphere of plasma and twisted magnetic fields is over 100 times larger than our own little planet, at a diameter of nearly 860,000 miles. Its mass is whopping 330,000 times that of Earth and has a surface temperature of nearly 10,000 °F. At its core, roughly 620 million metric tons of hydrogen is fused into helium by nuclear fusion EACH SECOND. Representing 99% of all the mass in our entire solar system, this object in our skies is, by all measures, god-like. 

Even at 93 million miles away, it can warm your skin, drive the evolutionary processes of an entire living Earth, and, if you don't respect it, it can kill you. 

It is known by many names. Eguzkia, hasi, sόlin, an ghrian, ilanga, qorraxda. In English it is simply known as "The Sun".

image: Alzate/Solar Dynamics Observatory

#sun   #SolarSystem   #Solar   #NASA   #SDO  
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 -- There are 200 billion stars in the Milky Way and 90% are small enough and old enough to have planets in orbit. And only 10% of these stars were formed with enough heavy elements to have Earth-like planets with 2% of these -- or  100 million super-Earths and Earths -- will orbit  within their star's habitable zone. 
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John Murrin

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The Brachistochrone
This animation is about one of the most significant problems in the history of mathematics: The Brachistochrone Challenge:

If a ball is to roll down a ramp which connects two points, what must be the shape of the ramp’s curve be, such that the descent time is a minimum?

Intuition says that it should be a straight line. That would minimize the distance, but the minimum time happens when the ramp curve is the one shown: a cycloid.

Johann Bernoulli posed the problem to the mathematicians of Europe in 1696, and ultimately, several found the solution. However, a new branch of mathematics, Calculus of Variations, had to be invented to deal with such problems. Today, calculus of variations is vital in Quantum Mechanics and other fields.

#physics   #mathematics
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John Murrin

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Privacy level insane!
Some people can go lengths to get their privacy!
Meet www.interestingengineering.com ♥
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BOSTON—A study published this week by psychologists at Northeastern University has determined that even a single instance of backing down during a fight with a significant other can inflict severe damage upon the relationship, often causing irrepara...
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John Murrin

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How QR codes work
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Have him in circles
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John Murrin

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[American Voices]

“Next thing you know, they'll say ‘listening’ and ‘writing things down’ will increase productivity too.” 
A new study has found that employees have more productive group meetings when they stand, suggesting that companies should adopt furniture designs and layouts that discourage sitting.
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Selling Science with Glossy Pictures and FTL Travel Baby!!!
The Washington Post published pictures of NASA's concept of what a Alcubierre drive spaceship might look like.  A few pundits immediately pointed out that perhaps hyping what amounts to a set of mathematical equations with a spacecraft design might not have been the classiest move on NASA's part.  NASA collaborator Mark Rademaker[1] maintains it was done with the intent of convincing people that STEM is cool, you know, 'for the kids'.  Here's Mark's big, glossy, futuristic design

It's cool and soooo pretty!

Discussion of how STEM should be sold aside, there are now conversations circulating the internet regarding whether or not the ship would violate causality by flying faster than the speed of light.  The answer is, that this might be an issue if the ship actually violated the speed of light by traveling 4.3 light years in 14 days.  As it is though, it doesn't.  Read on:

you can read everything here, but for the blog version with the pretty equations and so on, go to http://copaseticflow.blogspot.com/2014/06/selling-science-with-glossy-pictures.html

Travelling Faster than the Speed of Light Without Really Trying, (but not really)
The description in the Washington post article triggers a pretty common misconception:

"If an object reaches a distance x light years away in under x years, then it must be travelling faster than the speed of light."

What the article failed to mention is that the 14 days quoted is in the reference frame of the ship.  The equation for the distance travelled with respect to time in the frame of the ship, (known as proper time), is

(picture 2),

where a is the acceleration of the ship and c is the speed of light.

Using this formula, it can be shown that at an acceleration of 188g, (188 times the acceleration due to gravity), the ship could reach alpha centauri in 14 days of ship time.  You might point out that 188 g's would surely smush everyone against the back wall of the ship, but the beauty of the theoretical drive described is that you carry your own gravity well along with you and therefore, you're always in freefall and don't feel the acceleration.

Here's the problem though.  The time that will have elapsed here on Earth will be much, much greater than the 14 days that elapsed on the ship.  The expression for the time elapsed on Earth is

(picture 3),

which can be used to show that when the ship reaches alpha centauri, 817 years will have passed here on Earth.

The calculations shown here are nothing new, by the way.  Rindler applied them to the problem of relativistic space travel for the first time in 1960 in a Physical Review article titled "Hyperbolic Motion in Curved Space Time""[2].

References
1.  Mark Rademaker's blog
http://mark-rademaker.blogspot.com/

2.  Rindler, W., "Hyperbolic Motion in Curved Space Time", Phys. Rev. 119 2082-2089 (1960).

#physics   #specialrelativity  
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Sierpinski’s Triangle

This remarkable geometric object has an area of zero, but its perimeter is infinite.

The graphic shows the steps in constructing the triangle. At each step, the area decreases, and the total perimeter of its parts increases. 

Waclaw Sierpinski (1882–1969) conceived of this object in 1915.

#mathematics #fractals
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Not crazy enough

Niels Bohr (1885–1962) was a Nobel Prize-winning Danish physicist who made key contributions to understanding atomic structure and quantum theory.

Bohr expected that, to have a chance of being a good model of reality, any new physical theory would need to be deeply counterintuitive. He once made the following comment after hearing a lecture by his younger colleague, the Nobel Prize-winning Austrian physicist Wolfgang Pauli (1900–1958):

We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.

I found this version of the quote in the first sentence of the preface of the book The Self-evolving Cosmos: A Phenomenological Approach to Nature's Unity-in-Diversity by Steven M. Rosen.

Many of the quotes from physicists that one sees on social media come from Einstein or Feynman, but Bohr also said a lot of quotable things. You can find some of his other quotes at http://en.wikiquote.org/wiki/Niels_Bohr.

Relevant links
Picture source: Niels Bohr Archive (http://nba.nbi.dk)

Wikipedia on Niels Bohr: http://en.wikipedia.org/wiki/Niels_Bohr

Wikipedia on Wolfgang Pauli: http://en.wikipedia.org/wiki/Wolfgang_Pauli

#physics #scienceeveryday
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