The Internet’s Own Boy: The Story of Aaron Swartz

The film follows the story of programming prodigy and information activist Aaron Swartz. From Swartz’s help in the development of the basic internet protocol RSS to his co-founding of Reddit, his fingerprints are all over the internet. But it was Swartz’s groundbreaking work in social justice and political organizing combined with his aggressive approach to information access that ensnared him in a two-year legal nightmare. It was a battle that ended with the “taking of his own life” at the age of 26.

The film follows the story of programming prodigy and information activist Aaron Swartz. From Swartz's help in the development of the basic internet protocol RSS to his co-founding of Reddit, his fingerprints are all over the internet. But it was Swartz's groundbreaking work in social justice and political organizing combined with his aggressive approach to information access that ensnared him in a two-year legal nightmare. It was a battle that ended with the "taking of his own life" at the age of 26. Aaron's story touched a nerve with people far beyond the online communities in which he was a celebrity. This film is a personal story about what we lose when we are tone deaf about technology and its relationship to our civil liberties.

Revert a git branch state to a previous commit

How to revert state of a git branch to a previous commit from an older state

To reset index to former commit, where ‘26e05ffab‘ is the code associated with the old commit:

git reset 26e05ffab

Move pointer back to previous HEAD:

git reset --soft HEAD@{1}

Make a local commit of the whole revert:

git commit -m "Revert to commit 26e05ffab"

Update working copy to reflect the new commit

git reset--hard

Push the changes to remote branch:

git push origin [branch_name]

Push the changes to remote master branch:

git push origin [branch_name]:master

 

Update to Fedora 22 and GNOME 3.16

To update to GNOME 3.16 with Fedora, it is first necessary to update to Fedora 22 from Fedora 21.

To update to GNOME 3.16 with Fedora, it is first necessary to update to Fedora 22 from Fedora 21. To do this, first open a terminal and as root (i.e. sudo) and run the following commands:

sudo yum install fedora-upgrade 
sudo fedora-upgrade

This will update to the next highest upgrade available. In this case it will update Fedora 20 to Fedora 21. Next run

sudo rpm --import https://getfedora.org/static/8E1431D5.txt
sudo yum update yum
sudo yum clean all
sudo yum groupupdate 'Minimal Install'
sudo yum --releasever=22 distro-sync --nogpgcheck

If there are any problems running sudo yum --releasever=22 distro-sync --nogpgcheck, try the following instead:

sudo yum --releasever=22 distro-sync --nogpgcheck --skip-broken

If the problem persists you may wish to manually install the program causing trouble. But if so, do this with extreme caution by checking the program you are removing is not a core part of your install!

To install the GNOME Desktop simply type the following into the terminal:

sudo yum groupupdate "GNOME Desktop"

Parts of this instruction were borrowed from The Fedora Project Wiki

 

Free Textbook: Ordinary and Partial Differential Equations

Finite Difference and Spectral Methods for Ordinary and Partial Differential Equations is a textbook which was written during 1985-1994 and used in graduate courses at MIT and Cornell on the numerical solution of partial differential equations.

Finite Difference and Spectral Methods for Ordinary and Partial Differential Equations is a 325-page textbook  which was written during 1985-1994 and used in graduate courses at MIT and Cornell on the numerical solution of partial differential equations.

The book has not been completed, though half of it got expanded into Spectral Methods in MATLAB. Nevertheless, the part of it that is written is in quite polished form, including many exercises, and is suitable for classroom use (and indeed has been used at quite a few universities). Copies are now available here for use by anyone who wishes. There is no restriction on this use, except that any copies must not alter the original text and must include the author’s name.

The files currently online are missing some tables, figures, and text that are not available in PostScript or are in copyright; a list of some of these omissions is available.

Thanks to Darryl Yong of Harvey Mudd College for converting these PostScript files into searchable pdf files.

Cover Pages (ps,pdf)

Chapter 1. Ordinary differential equations. (ps,pdf)

Chapter 2. Fourier analysis. (ps,pdf)

Chapter 3. Finite difference approximations. (ps,pdf)

Chapter 4. Accuracy, stability and convergence. (ps,pdf)

Chapter 5. Dissipation, dispersion, and group velocity. (ps,pdf)

Chapter 6. Boundary conditions. (ps,pdf)

Chapter 7. Fourier spectral methods. (ps,pdf)

Chapter 8. Chebyshev spectral methods. (ps,pdf)

References. (ps,pdf)

A reasonable way to cite this book would be: Lloyd N. Trefethen, Finite Difference and Spectral Methods for Ordinary and Partial Differential Equations, unpublished text, 1996, available at http://people.maths.ox.ac.uk/trefethen/pdetext.html

Energy at the Center of Mass: Proton-Proton Collisions

Step by step instruction on how to calculate the center of mass for proton proton collisions.

Recall the definition of $s$:

$$s=(p_a+p_b)^2 = p_a^2 + p_b^2 +2p_a\cdot p_b$$

Where $p_a$ and $p_b$ are the 4-momenta of each colliding proton. For head on collision of particles with same energy and momentum as is the case with proton-proton collisions

$p_a=(E_p,\underline{p})$ and $p_b=(E_p,-\underline{p})$

Where $E_p$ is the energy of the proton and $E_p$>> the protons mass, $m_p$

$$s=(E_p, \underline{p})^2+ (E_p, -\underline{p})^2+2(E_p^2, \underline{p})\cdot(E_p^2, -\underline{p})$$

$$s=E_p^2+ |\underline{p}|^2+ E_p^2+|\underline{p}|^2+2E_p^2 -2|\underline{p}|^2$$

Sum together to get

\begin{eqnarray}
s=& 4E_p^2
\end{eqnarray}

The square root of $s$ gives the energy at the centre of mass

$$\sqrt{s}=2\sqrt{E_p}$$

 

 

A Crash Course in Einstein’s Relativity

Mark Twain once wrote: “It ain’t what you don’t know that gets you into trouble –it’s what you know for sure that just ain’t so.” So it was that, 109 years ago, some of humanity’s collective confusions were lifted when a 26-year-old Swiss patent clerk realized that something that everyone on Earth knew for sure was actually profoundly wrong. Come hear Professor Shankar get to the heart of Albert Einstein’s great insight, which has been called “The most beautiful thought that anyone has ever had,” using a blackboard, a piece of chalk and no equations. The only prerequisite for you: an open mind.

From Zero to c in 60 Minutes with Ramamurti Shankar

Mark Twain once wrote: “It ain’t what you don’t know that gets you into trouble –it’s what you know for sure that just ain’t so.” So it was that, 109 years ago, some of humanity’s collective confusions were lifted when a 26-year-old Swiss patent clerk realized that something that everyone on Earth knew for sure was actually profoundly wrong.

Come hear Professor Shankar get to the heart of Albert Einstein’s great insight, which has been called “The most beautiful thought that anyone has ever had,” using a blackboard, a piece of chalk and no equations. The only prerequisite for you: an open mind.

Professor R. Shankar is the John Randolph Huffman Professor of Physics at Yale University. A popular lecturer, his wry sense of humour and spontaneous witticisms have made him as famous as his research accomplishments and best-selling textbooks.

A sample: “Many people think that, since they’re going to be doctors or something, they’re never going to need to know about relativity. Well, what if one of your patients starts running away from you at the speed of light? Then you really need to know this.

Belt of Stability

The graph of stable elements is commonly referred to as the Band (or Belt) of Stability. At the higher end of the band of stability lies alpha decay, below is positron emission or electron capture, above is beta emissions and elements beyond the atomic number of 83 are unstable radioactive elements.

Table of Isotopes

 

Alpha decay is located at the top of the plotted line, because the alpha decay decreases the mass number of the element in order to keep the isotope stable. This is done by using the element helium (He). An unstable isotope’s protons are decreased by 2 and its neutrons are decreased by 4, and because the isotope was originally unstable before it went through alpha decay, the elements are still considered unstable.

Beta decay accepts protons so it changes the amount of protons and neutrons. the number of protons increase while neutrons decrease. To make things easier to understand think of the ratio of the isotope: there are too many neutrons compared to the number of protons therefore it is above the band of stability.

Positron emission and electron capture is when the isotope gains more neutrons. Positron emission and electron capture are below the band of stability because the ratio of the isotope has more protons than neutrons, think of it as there are too few protons for the amount of neutrons and that is why it is below the band of stability.

This work is a derivative of content from UC Davis  Creative Commons License