the suns distance. - Multiverse - Solar Week Message Board -

Solar Week - Ask a Question

Come here during Solar Week (next one: March 22-26, 2021) to interact. To post a question, click on your area of interest from the topics below, and then click on the "Ask New Question" button. Or EMAIL or tweet or plant in Answer Garden your question about the Sun or life as a scientist to us -- and watch for it to appear here. You can also visit our FAQs (frequently asked questions). In between Solar Weeks in October and March, you can view all the archives here.

Forums
Search Forum
Advanced SearchTopicsPosts

Prev Go to previous topic

Go to next topic

Last Post 3/18/2008 8:03 AM by David Alexander

the suns distance.

1 Replies

Sort:


You are not authorized to post a reply.

Author

Messages

Anonymous

Posts:

3/18/2008 5:52 AM
I was wondering how scientists can tell the distance between the sun and the earth. I read the facts on the sun and it said how they could tell how hot it is, the denceity, and how fast it is moving. Thoughout the whole paragraph there was nothing about how sciencetists can tell what the distance is between the sun and the earth. So my question is how can sciesntist tell what the distance is between the sun and the earth? Christina P.

David Alexander

New Member

Posts:50

3/18/2008 8:03 AM
Christina, Here is something I wrote recently relating to your question. Hope it helps. Most schoolchildren know that the Sun is 93 million miles (150 million kilometers) distant from the Earth. However, not many realize that we have only known this number for less than 150 years. Newton's laws of gravity, first appearing in the publication of his treatise “Philosophiae naturalis principia mathematica”, commonly known as Principia, in 1687, led to great advances in the understanding of planetary motions. However, with no accurate measurement of the true distance from the Earth to the Sun, astronomers could only determine the distances and orbits of other planets in the solar system in terms of the Earth's distance from the Sun (1 Astronomical Unit or 1 AU) and the Earth's 1 year orbit. It was almost 75 years later that careful observations by many dedicated astronomers who had ventured to the remotest parts of the globe led to a determination of how big 1 AU actually was in physical units (miles or kilometers). By observing the transit of Venus across the Sun simultaneously from several different latitudes they determined the value of 1 AU within the range of 1 AU = (149 – 156) million kilometers. Venus transits happen in pairs separated by 8 years with each pair being separated by 105-122 years (the most recent transit occurred on June 8, 2004, the next one will be June 5, 2012). The rarity of transits meant that it was very important to use the ones that came around as effectively as possible. The Venus transits of 1761 and 1769 gave the first opportunity to perform the necessary observations with sensitive enough telescopes to attain a value for the astronomical unit. For the astronomers of the 18th century it would be the observation of a lifetime. Subsequent transits refined the value of the astronomical unit but it wasn’t until the Venus transit of 1882 that the modern value of 93 million miles was attained was sufficient precision, some 200 years after the original publication of Newton’s Principia. Cheers - David