Using Search Engines

These days, astronomers use the Internet as one of their primary research tools. Finding information on the Internet, however, can be very frustrating. Very often you find yourself thinking, "How do I find information on pulsars? Is this information accurate and/or reliable? This isn't what I meant by 'relativity'!!!". This guide should provide you with some ideas for making your Internet searches more successful. In particular, we will look at using general search engines (like Yahoo and Altavista) and more specialised online astronomical databases (eg. ADS, the HST image archive).

A word of warning: One of the most difficult aspects of doing research on the Internet is deciding whether the information you have found is accurate or reliable. This is particularly true if you are researching a subject that you don't know much about. Take careful note of the website address and who is responsible for maintaining the site. In general, you can be confident that information you have found on websites maintained by universities and academic institutions, government research units (eg. NASA or CSIRO), or by professional astronomical associations will be accurate. You should treat information from someone's personal webpage, however, with a circumspection- no-one checks websites to make sure they have their facts straight!

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Introducing Search Engines

There are many different search engines available on the Internet, though these days just about everyone seems to use Google! Other search engines include Yahoo! and AltaVista. You can go to the default search engine for your web browser by clicking the "Search" icon on the toolbar of your browser window. Some search engines are better than others. In this context, 'better' means that they perform a wide-ranging search, but only return a well-sorted list of relevant links - nobody wants to wade through a list of 100,000 vaguely relevant or obscure webpages!

A brief introduction to Google

In this section, we will look at how to use the Google search engine effectively. Although some of the details will be different for other search engines, the general concepts that we will discuss (e.g. refining your search, sorted search results) apply to nearly all search engines. Remember that most search engines have a 'Help' and FAQ page if you get stuck, or want to study the search engine's advanced features.

The Google search engine can be found at http://www.google.com. The main page looks something like this:

Basic Search

To send a simple query to Google, just type in a few descriptive words and hit the 'enter' key (or click on the Google Search button). Google uses text-matching techniques to find websites that contain information that is relevant to your search. For example, to find information about the Crab pulsar, simply type Crab pulsar. i.e.,

Note that search engines are usually not case-sensitive, i.e., searching with large magellanic cloud and LARGE MAgellanic Cloud will produce the same results.

Choosing good search words

You need to think carefully about which words you want to search with. Suppose the essay topic you are researching is "Finding the redshift of distant quasars". To search the web effectively, you need to identify the most important concepts that you researching. In this case, the words redshift and quasars would be good choices to search with because they are very specific to the topic you are interested in. Searching with the words findingor distant, on the other hand, would produce a long list of websites that are irrelevant to your essay topic.

Refining Your Search

Sometimes a simple word search is not enough. Fortunately, there are quite a few conventions that can make your web-searching more precise. In particular, double quotes and - signs are very helpful.

Double quotes
Placing a phrase between double quotes ("....") will search for web pages containing exactly that phrase. For example, to search for pages about the cosmic microwave background you may wish to enter "cosmic microwave background" as an entire phrase. This will exclude pages that may use the words cosmic, microwave and background in a different context.

The - sign
You can use the - sign to exclude certain words. You may find, for example, that there is a brand of car called "Galaxy" and you want to exclude all its webpages from your search. To do this, simply type a - sign immediately before the excluded word. ie., type galaxy -car. Note that there is no space between the - sign and the excluded word.

Boolean Searches

Most search engines use Boolean expressions to refine search parameters. If you want to find websites with information about both pulsars and supernovae, for example, you would enter pulsar AND supernova in the search field. If you were looking for pages that contained information about either pulsars or supernovae (or both), on the other hand, you would type pulsar OR supernova. By convention, most search engines use an OR search as default.

Google, however, automatically searches for pages that contain ALL the terms that you enter. If you are using Google, there is no need to type AND between each term. To make an OR search with Google, you need to search twice. For our previous example, you would simply search with pulsar the first time, and then search again with supernova.

Wildcards

Most search engines use * to signify a wildcard characters. For example, entering cosm* will return websites containing the words cosmology, cosmic, cosmos, cosmologist, cosmetic, cosmopolitan... and many more besides! Simply typing cosm will have the same effect.

Note, however, that Google does not follow this convention. Typing cosm* into the Google search field will only return websites that actually contain the (non-existent) word cosm*.

Interpreting the search results

Once you have entered your query, the search engine returns a list of relevant websites. In general, the websites that the search engine thinks are the most relevant will be listed first. For example, here are the results from a Google search on quasars redshift:

A. Page Title
The first line of the result is the title of the web page found. Sometimes, instead of a title there will be a URL, meaning that either the page has no title, or the search engine has not indexed the full content of that page. Clicking on the Page Title will take you straight to the page.

B. Text Below the Title
This text is an excerpt from the returned result page with your query terms bolded. These excerpts let you see the context in which your search terms appear on the page.

C. Description
If your search query is listed in the web directory, the description filed by the open directory author is displayed.

D. Category
If your search query is listed in the web directory, the category in which it appears is displayed below its description.

E. URL of Result
This is the web address of the returned result.

F. Indented Result
When Google finds multiple results from the same web site, the most relevant result is listed first with the other relevant pages from that same site indented below it.

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