Saturday, February 16, 2008

One of the Earliest Galaxies Ever Observed

Many of my students are fascinated with the concept of gravitational lensing. In general relativity, Albert Einstein conceived the idea that gravity is not a force, in our sense of the word, but rather a consequence of matter warping the space-time continuum. This is indeed very abstract and weird for one to comprehend, as our brains are unable to picture things in four dimensions. However, a prediction based on this model was that light should then be 'bent' by gravity since photons must travel through space and time. It is like a ball rolling on a hilly surface...it will 'bend' its direction of travel because it must follow the surface. In the case of gravity, this was very different from what Newtonian gravity predicted, since photons do not have mass.

Gravitational lensing is now used on a daily basis by astronomers to help them see very distant objects. Now, a galaxy has been observed at some 13 billion light-years from the earth. This galaxy would have existed fairly soon after the Big Bang (13.7 billion years ago), and I would have to guess it was a first generation galaxy with first generation stars. Chalk up another discovery for the Hubble Space Telescope.

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