Galaxies are enormous, but they are not the largest structures in the Universe. We find that the galaxies themselves group into clusters of galaxies held together by mutual gravitational attraction, and that clusters of galaxies are themselves associated with even larger superclusters of galaxies. In this lab we will look at these largest structures that we know of and use them to determine the value of Hubble's constant, which tells us the rate of expansion of the Universe itself.

In this lab you will learn about the expansion of the universe and you will use some of the same methods astronomers use to find out how rapidly the universe is expanding. You will also use these techniques to determine the age of the universe. In the process you will also learn about clusters of galaxies.


  1. Read the background material by clicking on the topics listed on the menu on the left side of this page. For a given topic there may be multiple pages each of which can be accessed using the navigation buttons arranged across the top of each page.

  2. Click on the menu item "Problems." A window should open at the bottom of your screen with the questions.

  3. Familiarize yourself with clusters of galaxies. Use the Virtual Observatory to determine distances to clusters of galaxies.

  4. Use the interactive plotting activity to help you determine the Hubble constant.

  5. Read the section on the age of the universe and answer the relevant questions.

  6. Answer the questions by filling in the form fields on the computer. Hit the button labeled "Submit" when you are done. A confirmation page will appear with all your answers imbedded. Be careful not to close the problems window until you are finished and want to submit or your answers may be lost and you will have to reenter your answers.

  7. Check over the confirmation page to make sure that you are happy with your answers. If you need to change your answers go back to step 6 and re-submit. We will only grade the last form you submit.

    Good Luck!