SUNSET: 
New Studies Agree: The Universe Is Expanding Faster Than Expected
Measurements of elliptical galaxies provide a new way of calculating the current expansion rate of the universe. And the results are adding to a growing controversy.
How many digits are satisfactory in the measurement of pi?
In the 3rd century BC, Archimedes proved that the ratio of a circle’s circumference to its diameter is less than 3 1/7 but larger than 3 10/71. That’s about 3.141. Later mathematicians have computed what we now call p (pi) to greater and greater accuracy — but how many digits…
How can we find the Sun's place among the constellations?
How can I find out how our Sun would look among the constellations, as seen from a nearby star? What made me curious was a painting by space artist David Hardy that pictured the Sun as an extra star in Cassiopeia. Fancy planetarium projectors produce such scenes, but you can…
Should you use light-years or parsecs for astronomical distance?
You give astronomical distances beyond the solar system in light-years, but professional astronomy papers use parsecs. Which is preferable? Light-years, no question! Here’s how I see it. The parsec (which equals 3.26 light-years) is defined as the distance at which a star will show an annual parallax of one arcsecond.…
When we say a galaxy is 300 million light-years away is that its distance now or 300 million years ago?
When we say a galaxy is 300 million light-years away, is that its distance now or 300 million years ago? Oftentimes, neither! In most cases astronomers try to get a handle on a galaxy’s distance by measuring its redshift: the degree to which the universe’s expansion has stretched its light…
What's the most distant object I can see with my telescope?
Is there a more distant object than NGC 4889 (Caldwell 35) that I can see with my 5-inch reflector? Yes, by a factor of 7! Think quasars. NGC 4889 is a member of the Coma Galaxy Cluster, which lies about 300 million light-years away. But the quasar 3C 273 is…
Why are the stars so far away?
Why are the stars so far away? That question has a real answer: Because if the stars were much closer, Earth wouldn’t exist, and we wouldn’t be here to ask.
