MadSci Network: Astronomy |
Hello, Carl - Well, I think the best response comes from Ask the Astronomer: http://www.astronomycafe.net/qadir/acosmexp.html "Am I being stretched along with the expansion of the universe?" "No. The 'stretching' of space in Big Bang cosmology only happens on very large scales in the universe of millions of light years or greater. It is not something we can detect at our scale because local space-time is determined not by cosmology, but by the fact the Earth and Sun are nearby; and their gravitational fields do not produce a constantly dilating background space." So the spaces between particles would not be stretched either. Here are some more questions and answers from the same site: "Wouldn't the expansion of space show up inside the solar system in the predicted positions of the planets?" "No, and for a variety of reasons. The most significant reason is that the gravitational field of the Sun and the Milky Way are stronger than the local gravitational field of the universe. This means that the dynamics of spacetime in our solar system and Milky Way are dominated by the curvature produced by these local masses. As an example, if the cosmological expansion could be detected in our solar system, its 60 kilometers/sec/megaparsecs would translate into a space dilation rate of 6 centimeters per second per parsec, or for a scale inside our solar system, 0.0002 centimeters/sec per billion kilometers. In 100 years this stretching would amount to 6.2 kilometers at the solar system scale, and 186,000 kilometers at the interstellar scale. Neither of these are measurable, nor is there any physical reason from general relativity why they should even be present given the strength of the local sources of gravity which completely overpower the effect." "Why don't the distances between stars also 'expand' with the universe?" "A good question. The answer is that general relativity eventually joins smoothly with ordinary Newtonian physics, just as special relativity does for low enough velocities. By the time you get to scales comparable in size to individual galaxies, the character of space-time is controlled not by the comparatively weak gravitational fields of the cosmos, but by the stronger gravitational fields of individual stars, star clusters and the rest of the contents inside a galaxy. These fields are strong enough to maintain the dynamical integrity of a galaxy against the expansion of the rest of the universe. Clusters of galaxies, however, are in some cases so large that they do not remain cohesive against the so-called Hubble Flow, and so the physics of these vast systems can require a 'cosmological correction' due to the expansion of space. Stellar distances, however, are controlled by the gravitational physics of their immediate environment, and there are no cosmological corrections of any significance. Interstellar space, therefore, does not stretch the same way that intergalactic space does under cosmic expansion."
Try the links in the MadSci Library for more information on Astronomy.