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Online Education. Udacity - Educating the 21st Century. OpenStudy: Study Together. Lets compile a list of the best online learning centers. We could all use a little education.


"Waiting for Superman": What it Means for You and Your Child. Every president, from Johnson to Obama, has made big promises when it comes to “fixing” education in America.

"Waiting for Superman": What it Means for You and Your Child

And almost every parent, from then until now has asked themselves an essential question—“Is my child getting a good education?” Regardless of neighborhood or income, it’s a concern that keeps parents up at night, and the answer rests at the heart of a national firestorm brewing over education. Fanning the flames is a new and controversial documentary, Waiting for Superman, which paints a grim picture of the education system in the United States today. Director and writer Davis Guggenheim, best known for his film An Inconvenient Truth, picks apart the issues holding American school children back; from government bureaucracy, to bad teachers who can’t be fired, to a system that is out of touch with the needs of the global economy.

Waiting for Superman has raised a lot of fear and anger.


Math. Nature. The Messenger Series. Lecture 1: The geometry of linear equations. Hi.

Lecture 1: The geometry of linear equations

This is the first lecture in MIT's course 18.06, linear algebra, and I'm Gilbert Strang. The text for the course is this book, Introduction to Linear Algebra. And the course web page, which has got a lot of exercises from the past, MatLab codes, the syllabus for the course, is And this is the first lecture, lecture one. So, and later we'll give the web address for viewing these, videotapes.

The fundamental problem of linear algebra, which is to solve a system of linear equations. So let's start with a case when we have some number of equations, say n equations and n unknowns. So an equal number of equations and unknowns. That's the normal, nice case. And what I want to do is -- with examples, of course -- to describe, first, what I call the Row picture. So in a minute, you'll see lines meeting. The second picture, I'll put a star beside that, because that's such an important one. And maybe new to you is the picture -- a column at a time.

Okay, so can I do an example?


Cell Size and Scale. Some cells are visible to the unaided eye The smallest objects that the unaided human eye can see are about 0.1 mm long.

Cell Size and Scale

That means that under the right conditions, you might be able to see an ameoba proteus, a human egg, and a paramecium without using magnification. A magnifying glass can help you to see them more clearly, but they will still look tiny. Smaller cells are easily visible under a light microscope. It's even possible to make out structures within the cell, such as the nucleus, mitochondria and chloroplasts. To see anything smaller than 500 nm, you will need an electron microscope. How can an X chromosome be nearly as big as the head of the sperm cell? No, this isn't a mistake. The X chromosome is shown here in a condensed state, as it would appear in a cell that's going through mitosis.

A chromosome is made up of genetic material (one long piece of DNA) wrapped around structural support proteins (histones). Adenine.


Physics. Astrophysics I « Physics Made Easy. Luminosity: Fλ is the radiative flux at the stellar surface.

Astrophysics I « Physics Made Easy

Energy may be lost due to neutrinos or direct mass loss. Flux: At the Earth’s surface, observed flux is Stellar flux Apparent magnitude, m, is based on the flux received at the Earth’s surface, fν (flux at frequency ν). Fainter star has larger magnitude. Absolute magnitude, M, is defined using the flux we would see from a star if it was 10 parsecs distant, Fν. Bolometric magnitude is calculated using the total flux f integrated over all frequencies. apparent absolute Distance modulus, d: by taking the difference between the apparent and absolute magnitudes, a measure of the distance to a star can be found.

Distance measurements using trigonometric parallax: ‘close’ stars appear to move against the background of fixed stars, such that their positions appear different to an observer on Earth when observed at the two extremes of the Earth’s orbit. Small angle know this, everything should be easier. d=distance to binary Kepler’s Laws 3<ν<5 or iii) 18.06 Linear Algebra, Spring 2010.