ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Cold Dark Matter (CDM)

Updated on March 18, 2013

Before we discuss cold dark matter, if you don’t know what dark matter is, it might be an idea to see my hub ‘What is Dark Matter?’ which explains this.

Dark matter cannot be detected at all by electromagnetic radiation and it is thought to exist because of the detection of its gravitational effect. The idea that it is present can be used to explain how galaxies were formed after the Big Bang. Cold Dark Matter is the more likely scenario of the three hypotheses that attempt to explain this process. The others are Hot Dark Matter (HDM) and Warm Dark Matter (WDM).

The difference between all these hypotheses is the distance that the particles traveled just after the Big Bang. Until the particles were slowed down by the expansion of the universe, the distance they travelled was known as the free streaming length. This length determines whether we are talking about the dark matter being hot, warm or cold.

A protogalaxy is a cloud of gas that is prior to it forming into a galaxy, possibly of the size of a dwarf galaxy. If the free streaming length of particles is thought to be about smaller than this protogalaxy, then we are talking about Cold Dark Matter.

Cold Dark Matter is the simplest and most likely of the explanations for what happened after the Big Bang. Most particles are found to become non relativistic very early on, this means that they have a velocity that is very small in comparison to the speed of light, and therefore can be classed as particles of Cold Dark Matter.


The particles that are thought of as being part of this Cold Dark Matter theory are called WIMPs (Weakly Interacting Massive Particle). No-one knows what these particles might be and nothing has been found that fits the criteria yet. However, if they were to exist, this would make the Cold Dark Matter theory the most attractive.

Cold dark matter leads to a bottom-up formation of the universe with small objects being created first, and larger galaxies and clusters of galaxies being created subsequently. There are a few discrepancies between this theory and some observations of galaxies for example the fact that there should be more dwarf galaxies than is observable. However, computer simulations of dark matter particles operating as Cold Dark Matter particles, confirm that the universe would be created as it is today with these rules in place.


    0 of 8192 characters used
    Post Comment

    • writerbeth profile imageAUTHOR


      5 years ago from England

      No problem, I was trying to keep it simple really and I did go into more detail in my main hub about dark matter itself - what would you like to know more about? I'll see if I can help. Thanks Beth

    • ilscherzo profile image


      5 years ago from Singapore

      Thank you for sharing. The formation of the universe is an interesting topic. However it would be nice if you elaborated a little more.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)