Scientists Cut Uncertainty of the Size of the Universe in Half


The night sky has captivated people for as long as we have told stories. For millennia, mankind has sat in the dark and taken in the glorious spectacle of the stars and planets as they have marched across the sky. While we now know that space goes on essentially forever, it’s important to remember that star gazing is inherently a two-dimensional endeavor. To all intents and purposes, the sky is like a giant television screen. We can precisely know the position of celestial objects on the tapestry of the heavens, but knowing how far away these objects are is much harder.

In our common experience, we can determine the distance of objects using our binocular vision inherited from our tree-living ancestors, but even using our best space-based telescopes and most sophisticated techniques, this approach works for objects that are within a ten or twenty thousand light years. While impressive, that distance is just peanuts to space.

For distances greater than that, it is necessary to compare the absolute and observed brightness of well understood objects and to use the difference to determine the object’s distance. Essentially, this approach is the same as when sailors use the apparent brightness of a known lighthouse to estimate how far away it is.

In astronomy, finding an object of known brightness is very difficult. After all, there are examples of both bright and dim stars and galaxies. Luckily there is one astronomical phenomenon for which it is possible to work out its absolute brightness. This object is called a supernova. Supernovae are the death throws of a star in the last minutes of its life. The star explodes with such violence that we can see the flash across the vast universe. The special —> Read More