How can light from the first galaxies reach us when the space simply grows faster than the speed of light?

The light of extremely distant objects has done about 13 billion years to reach us.

This does not mean that these objects were also 13 billion light years away.

During the 13 billion years that the light was on the way, the universe continued to expand.Since expansion went very quickly in the beginning, those objects were much and much closer, in this case around 3 billion light years.

It also does not mean that these objects are now 13 billion light years away.Even after the light that we now see from very distant galaxies had gone through a piece of space, it just continued to stretch.

A distance in which the light took over 13 billion years, has a redshift of 9 by the expansion of the universe. That corresponds roughly to a distance of 30 billion light years.

For determining those distances and redshift it is necessary to go out observations of the expansion velocity.The different observations give a slightly different value. There are uncertainties about the other parameters as well. There is a growing consensus that the most common values for these parameters are indeed the right one.

However, I have rounded the distance values so bluntly to easier numbers, that these differences are little.

Distances in the Universe

Cosmology Distance Calculator

Even the light of the CMB (Cosmic 2.7 K radiation) still reaches us.That light was last aired ~ 400 000 years after the Big Bang from a place now with ~ 4 times the light velocity of us removes. If the expansion of space does not diminish, the light of that place (where galaxies are now also) will not be able to reach us. So there is a finite amount of light coming to us from that place. That doesn’t stop suddenly but is being smeared over an infinite time with ever increasing redshift. Now the distance from whence the CMB radiation came 46 billion light years. At the time of appearance, that distance was ~ 46 million light years, the universe has expanded in the meantime by a factor of 1000. Expansion in which the speed of light is exceeded is not in contradiction with relativity theory. The expansion concerns the geometry of the space. The speeds of objects in that geometry cannot exceed the speed of light.

It is indeed assumed that there are galaxies of which we cannot see the light, and that this is even much more than we can see.

If the space grows faster than the speed of light (which is not yet established), it does not mean that all galaxies will be removed at a speed higher than the speed of light of our galaxy.Apart from the fact that objects with mass can never move at a speed of light or higher, galaxies also sometimes move towards each other.

Leave a Reply