computing

Extraterrestrials & the Digital Universe -Von Neumann & Edward Teller

Standard
Hello,

I’ve been reading George Dyson’s Turing’s Cathedral lately & today I read something interesting about intelligent life & computers from the age of John von Neumann & Edward Teller, which I’d like to share [1]:

Von Neumann rarely discussed extraterrestrial life or extraterrestrial intelligence; terrestrial life and intelligence were puzzling enough.

…”There is every reason to believe that any planet on which a large variety of molecules can reproduce by interconnected (or symbiotic) autocatalytic reactions, may see the formation of organisms with the same properties.” One of these properties, independent of the local conditions, might be the development of the Universal Machine.
Over long distances, it is expensive to transport structures, and in expensive to transmit sequences. Turing machines, which by definition are structures that can be encoded as sequences, are already propagating themselves, locally, at the speed of light.

…Those best able to survive the passage of time, adapt to changing environments, and migrate across interstellar distances will become the most widespread. A life form that assumes digital representation, for all or part of its life cycle, will be able to travel at the speed of light. As artificial intelligence pioneer Marvin Minsky observed on a visit to Soviet Armenia in 1970, “Instead of sending a picture of a cat, there is one area in which you can send the cat itself.” [p.290]

The host planet would have to not only build radio telescopes and be actively listening for coded sequences, but also grant computational resources to signals if and when they arrived. The SET@home network now links some five million terrestrial computers to a growing array of radio telescopes, delivering a collective 500 teraflops of fast Fourier transforms representing a cumulative two million years of processing time. Not a word (or even a picture) so far -as far as we know. [p.291]

In a discussion with Edward Teller, the authors quotes Teller:

 “…If there is life in the universe, the form of life that will prove to be most successful at propagating itself will be digital life; it will adopt a form that is independent of the local chemistry, and migrate from one place to another as an electromagnetic signal, as long as there’s a digital world -a civilization that has discovered the Universal Turing Machine- for it to colonize when it gets there. [p.292]

Useful Unix/Linux commands

Standard
$ indicates terminal command
# indicates a comment
Bold indicates “not installed by default”
$ lsusb     #list USB devices
$ lspci     #list all PCI devi
$ startx    #initialize an X session
$ more      #filter for paging through text one screenful at a time. (less gives more advanced).
$ less      #opposite of more; allows backward movement in the file as well as forward movement.
$ stty      #change and print terminal line settings
  $ stty size # prints terminal size

File commands

$ locate            #find files by name (for newbies I suggest the gui catfish -requires installation)
$ find              #search for files in a directory hierarchy
$ ls                #list directory contents
$ cd                #change directory
$ pwd               #print name of current/working directory
$ cp                #copy files and directories
$ rm                #remove files or directories
$ rmdir             #remove empty directories
$ file foo.format   #extracts info about file and what software it was written with; helpful in the case of having forgot which software was used to produce such a file

System info

$ uname
$ df                         #report file system disk space usage
                             #e.g; df or df /home
$ man                        #interface to the on-line reference manuals
$ free                       #Display amount of free and used memory in the system
                             #e.g; free -mt (m for MB & t for totals line)
$ uptime                     #tell how long the system has been running.
$ finger                     #user information lookup program
$ w                          #show who is logged on and what they are doing.
$ whoami                     #print effective userid
$ cat /proc/meminfo          #memory info
$ cat /proc/cpuinfo          #cpu info
$ lsb_release -a             #print (a: all ) distribution-specific information
$ last -x | grep shutdown    #show listing of last 10 logged in users; you can pipe this to the tail to read the last n instances.
                             #e.g; for 10 instances: last -x | grep shutdown | tail -n 10
$ last -x | grep reboot      #show listing of last logged in users
$ sudo shutdown -P hh:mm     #shutdown & poweroff (-P) @ hh:mm

Processes

$ uname
$ ps               #report a snapshot of the current processes.
$ top              #display Linux tasks
$ htop             #interactive process viewer based on top
$ watch            #execute a program periodically, showing output fullscreen
                   #e.g; watch -n 5 free -m
$ powertop         #program to analyze power consumption on Intel-based laptops
$ kill pid         #send a signal to a process
$ killall proc     #kill processes by name
$ pidof program    #find the process ID of a running program

Some useful terminal shortcuts

Ctrl+C #halt the current command
Ctrl+Z #pause command
$ fg #resume paused command in foreground bg resume paused command in background
Ctrl+D #logout of current session (similar to exit)
Ctrl+W #erase last word before cursor
Ctrl+U #erases the whole line
Ctrl+R #type to bring up a recent command
I hope this list turns out to be useful to you 🙂

Thanks for reading

last update: 2014-11-03

Linux: What is it & why? (vids)

Standard