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What happens when I click on ksnn.larc.nasa.gov?
In 1989 researchers at a physics lab in Switzerland paved the way for the World
Wide Web or www, which allows computers to connect to each other anywhere in the world! Every computer on the web has an address so it can be easily located. The computer's address is called a Uniform Resource
Locator or URL; www and URL are quite a mouthful - that's why we abbreviate them! The KSNN web site's URL resides on a computer and KSNN's address is ksnn.larc.nasa.gov. This URL is similar to a mailing address if you think of each dot as indicating a new line. For example:
ksnn¿ ¿ Randy Caton
larc ¿ ¿ Christopher Newport University
nasa ¿ Newport News, Virginia
gov ¿ ¿ 23606
The URL lets computers know where other computers are, but how does that tell us what happens when you click ksnn.larc.nasa.gov? Well, the really valuable contribution of the researchers was to develop the hyperlink and hypertext. Hypertext is text on a special computer page that is linked by a hyperlink to another computer (anywhere in the world!) or even to text on a page in a file on a computer somewhere in the world. Everything happens in a hyperspace of linked computers we often now call cyberspace. To make the links in cyberspace, the URL is crucial.
You are so familiar with working in cyberspace that you don't even think of the complex things that go on when you click on a link with your mouse. The URL is a name we humans use to make it easier to remember. For example, KSNN stands for Kids Science News Network. The computer uses a number for the address of another computer called an Internet
Protocol or IP address. The IP address has a series of four 3 digit numbers seperated by dots, like xxx.xxx.xxx.xxx to allow for about 4.3 billion different addresses!
So what does happen when you click ksnn.larc.nasa.gov? You have to be on a computer that is connected to a special computer called a server (your own computer could be a server if it is set up that way) that does tasks like connect you to a web page maybe thousands of miles away. The server is connected to the Internet, which is the complex connected web of the world's computers you could also call cyberspace. When you click the mouse, your computer sends KSNN's IP address to the server and the server sends your requested URL out to the Internet in the form of an IP address. The request goes to a larger server that is set up just to connect to other big servers around the world. If the request isn't for a computer in its realm, which is most likely, it sends the request on to another big server. After anywhere from a couple to 20 hops to other servers, the request arrives at its destination. To get to Russia and back from the USA may take only 15 hops and around a hundred milliseconds (a tenth of a second).
Then how does your computer display the web page? The destination server takes your request and sends the web page back to your computer in a language called HTML. Your browser can interpret HTML and display the page on your screen. Then why does it often take a long time to load a web page? If the page has a lot of graphics, more information has to be sent and displayed by your computer and that takes time. So there is quite a lot going on when you click on ksnn.larc.nasa.gov!
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