The Curated Internet

  https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html Here the approximate cost in energy has been given in terms of velocity (kilometers per second, km/s), a common ploy engineers use to simplify the discussion. These numbers assume ideal conditions such as no losses for atmospheric drag or combustion but are close enough for the sake of this illustration.    

 

It took me a whole hour to figure how to set up a .desktop file on Ubuntu which honestly seems unnecessarily complicated. In previous versions of Ubuntu, there was a GUI (gnome-desktop-item-edit) which aided in this process but unfortunately, this appears to have been removed. Here are some useful notes to set up .desktop files .desktop file format example #!/usr/bin/env xdg-open [Desktop Entry] Version=1.0 Type=Application Terminal=false Exec=/usr/bin/gedit %U Name=Test_1 Comment=comment here Icon= What's the %U in the Exec file? It's a parameter for the Exec key in .desktop files (defined in the Desktop Entry Specification) that describes how arguments to the program (from the file manager/program launcher, e.g. multiple selected files) should be handled Make the desktop file executable and copy it to /.local/share/applications Launching the file from the terminal gtk-launch something.desktop  

 A great tool to understand galaxy rotation curves : https://wittman.physics.ucdavis.edu/Animations/RotationCurve/index.html