The Gell-Mann Amnesia Effect

Briefly stated, the Gell-Mann Amnesia effect is as follows. You open the newspaper to an article on some subject you know well. In Murray’s case, physics. In mine, show business. You read the article and see the journalist has absolutely no understanding of either the facts or the issues. Often, the article is so wrong it actually presents the story backward—reversing cause and effect. I call these the “wet streets cause rain” stories. Paper’s full of them.

In any case, you read with exasperation or amusement the multiple errors in a story, and then turn the page to national or international affairs, and read as if the rest of the newspaper was somehow more accurate about Palestine than the baloney you just read. You turn the page, and forget what you know.

— Michael Crichton

No comment necessary.

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Squeezed light a small step forward toward detecting gravitational waves

They stand as the last great prediction of general relativity: gravitational waves. They haven’t been detected yet, but it seems almost unthinkable for them not to exist. Detecting them though… that is what might be described as a tough problem.

These deformations of space are incredibly tiny. So tiny that making instruments to detect them has produced some of the most challenging engineering problems ever seen. Now, the engineers and physicists can celebrate some progress. Squeezed light has left the lab and is being used to improve a gravitational wave observatory.

Gravity is by far the weakest of the fundamental forces, so building detectors for gravity waves, let alone gravitons, pushes the limits of 21st century technology. The quantum effects are Yet Another Problem, since the quantum fluctuations of space itself add noise to the measurements.

Scott Chacon on Github Flow

At GitHub, we do not use git-flow. We use, and always have used, a much simpler Git workflow.

Its simplicity gives it a number of advantages. One is that it’s easy for people to understand, which means they can pick it up quickly and they rarely if ever mess it up or have to undo steps they did wrong. Another is that we don’t need a wrapper script to help enforce it or follow it, so using GUIs and such are not a problem.

Read the whole thing. Here’s the quick summary:

What is GitHub Flow?

  • Anything in the master branch is deployable
  • To work on something new, create a descriptively named branch off of master (ie: new-oauth2-scopes)
  • Commit to that branch locally and regularly push your work to the same named branch on the server
  • When you need feedback or help, or you think the branch is ready for merging, open a pull request
  • After someone else has reviewed and signed off on the feature, you can merge it into master
  • Once it is merged and pushed to ‘master’, you can and should deploy immediately

Using Rails 3.X with Heroku

A quick note from experience: using either Rails 3.0 or 3.1, I kept getting this error (issue #1376 at github):

$ git push heroku master
[…]
Installing ruby_core_source (0.1.5)

Installing linecache19 (0.5.12) with native extensions Unfortunately, a fatal error has occurred. Please report this error to the Bundler issue tracker at https://github.com/carlhuda/bundler/issues so that we can fix it. Thanks!

/usr/local/lib/ruby/1.9.1/rubygems/installer.rb:483:in rescue in block in build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

[…]

/usr/local/lib/ruby/1.9.1/fileutils.rb:243:inmkdir’: Read-only file system – /usr/local/include/ruby-1.9.1/ruby-1.9.2-p180 (Errno::EROFS)
from /usr/local/lib/ruby/1.9.1/fileutils.rb:243:in fu_mkdir'

Aha. The problem is in linecache19, and the explanation given by dpiddy in issue #1356 is spot on:

linecache at least with 1.9 needs the full ruby source/headers, not just what gets installed normally for building extensions. To aid in getting the necessary stuff, there’s the ruby_core_source gem which is used from linecache’s extconf.rb. ruby_core_source tries to fetch the appropriate ruby source distribution and move things from it under Config::CONFIG["rubyhdrdir"]. If that’s not somewhere you can write to, it’ll break.

You see the failure when installing linecache19 itself because installing ruby_core_source doesn’t actually do anything, it only does something when used from linecache’s extconf.rb.

The best way to avoid this problem is to put linecache (probably really ruby-debug) in a test/development group and pass --without development test or --deployment to bundle install on the server side.

So, to fix, make sure ruby-debug is specified in the Gemfile as follows (I like to use sqlite3 for local dev, but must use Postgres on Heroku):

group :development, :test do
  gem ‘ruby-debug19’, :require => ‘ruby-debug’
  gem ‘sqlite3-ruby’, :require => ‘sqlite3’
end

When you deploy to Heroku, Bundler will be run automatically as long as a Gemfile is present. If you check in your Gemfile.lock, Heroku will run `bundle install –deployment`. If you want to exclude certain groups using the –without option, you need to use `heroku config`. So, to make sure we don’t require the gems in development or test mode, set the app’s environment variable BUNDLE_WITHOUT as so:

$ heroku config:add BUNDLE_WITHOUT=”test development” –app app_name

Presto, Bob’s your uncle.

LHC results put supersymmetry theory ‘on the spot’

“It’s a beautiful idea. It explains dark matter, it explains the Higgs boson, it explains some aspects of cosmology; but that doesn’t mean it’s right.

“It could be that this whole framework has some fundamental flaws and we have to start over again and figure out a new direction,”

Lead_ion_collisions

This is how Science is supposed to work. Supersymmetry is a beautiful theory with lots of explanatory power. But if the predictions don’t match with observational evidence, well, it is just pretty math.

Supersymmetry hasn’t been completely ruled out, yet, but the versions that remain viable are more theoretically complex, and that is never good news. Nature usually sides with elegant ideas. Sadly, one of the elegant ideas to lose out will be String Theory, which requires Supersymmetry.