After all, from that distant galaxy’s perspective we are moving away from it faster than light, speed being relative and all. Since the speed of light is about 300,000 km/s, with our current Hubble constant that means that critical separation distance is about 15 billion light years.Ī galaxy 16 billion light years away is moving away from us faster than light, but that distant galaxy isn’t defying relativity. Because of this, if you consider two points far enough apart they will be moving away from each other faster than light. Since all of space is expanding, the greater the distance between two points in space, the faster they move apart.
This means that two point in space a million light years apart are moving away from each other at 20 kilometers per second. Currently our best measurement of the Hubble constant is about 20 km/s per million light years. The rate of cosmic expansion is determined by what is known as the Hubble constant. Over time we’ve come to understand that this relation is not due to galaxies racing away like an initial explosion from a single point, but rather it’s due to the fact that space itself is expanding. This relation between redshift and distance is known as Hubble’s law. Since the 1920s we’ve known that the more distant a galaxy is, the greater its apparent redshift, and thus the faster is appears to be moving away from us. What about something moving faster than the speed of light in a vacuum? It turns out that even that is possible in a way, thanks to general relativity. While that’s all fine and good, you might argue, neither of these phenomena are actually traveling faster than light. By analyzing these sounds we can determine things such as the density and pressure of the Sun’s interior. The study of these sonic vibrations is known as helioseismology, or in the case of other stars, asteroseismology.
Sound waves can travel through the Sun at thousands of meters per second, and they cause the Sun as a whole to vibrate. As a result, they aren’t hampered by the ions in the core. They are pressure waves that transfer energy through a material rather than transporting material itself. Guentherīut sound waves propagate in a different way. Animation of the l=3, m=0 mode of oscillation (shown greatly exaggerated).
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