Frequently Asked Questions

OK, so there ARE lots of other galaxies, beyond the Milky Way: Are they moving?

Spectroscopy, which can identify objects via unique combinations of so-called “spectral lines,” can also be used to measure velocity, thanks to the Doppler effect.   Leavitt used the “identification” properties of spectroscopy to find her law, but to find his, Hubble needed to focus on velocity measurements as well.  He made extensive use of the measurements of Vesto Slipher, who was the first astronomer to measure Doppler shifts to higher velocity (...

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How Big is the Milky Way--is it the whole Universe?

By the early 20th century, it was possible to see and measure a very different Universe than was accessible to the Ancients, or even to Galileo and Newton.   It had many more stars, and it had beautiful collections of stars (then called “nebulae”) with crazy patterns—like spirals.  (See the modern image of M31 shown here in color, for a good example of a “Spiral” galaxy.) 

Spectroscopy hinted that faraway objects were composed of elements not unlike those in the Sun, and that they were...

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Supernatural Solutions

Of course, these two tricky questions can be avoided if a supernatural power pressed a "start" button on time, and controls whatever is "beyond" our Universe.  In Ancient times thinkers across cultures believed the Universe was controlled at least in part by supernatural forces. 

Even by the 17th century, when Galleo’s telescopic observations of Jupiter had effectively disproven the Ancients’ Earth-centered Solar System, and Isaac Newton had shown how gravity controlled the...

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Why does Hubble’s Law often confound those born and raised on Earth?

A wide variety of modern astronomical observations clearly show that our Universe had a beginning in time, known as the “big bang.”  But, those same observations also show that the Universe expands in all directions simultaneously, meaning that it has no single birthplace in space. 

Unless time is treated as a fourth dimension, akin to the three dimensions of space, these ideas--a starting time, but not a starting place, are...

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How can I use WWT on my Mac?

There are several ways you can use WWT on your Mac. The simplest way is to just use the web client in your browser without downloading anything. However, this does not give you full access to all of WWT's features. You can also install the Windows Operating System on your Mac and run WWT from there. There are a couple of ways to do that, including bootcamping your Mac and installing a paid program that lets you run Windows on your Mac. For more information on these options, see ...

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What is a tour?

"Tours" are interactive paths through the night sky, designed to tell a story or teach a particular astronomy concept.  They look like movies, but when viewed in WWT, you can pause the tour to explore regions of the sky that catch your interest, and you can click on hyperlinks throughout the tour to learn more about an object or phenomenon.

You may create a tour using the desktop version of WorldWide telescope.

Here is a screen cast of an example tour, made by Alyssa Goodman, called "Dust and Us."...

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How do I change the scale in WWT?

In the bottom right corner of the WWT window, you should see a small horizontal scale labeled “Planet Size” and going from “Actual” to “Large.” Adjusting this will enlarge the planets, stars, and other objects, keeping their relative sizes accurate, but without scaling the distances proportionally. This makes things much easier to fit on the screen, but makes things look much closer together than they are. ...
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