We observe farther galaxies with higher redshifts. How can we be sure that this is due space itself expanding? How do we know that this is not just Doppler shift of galaxies running away from us at higher speeds long time ago, that got lowered (decelerated by gravity of matter in the universe) later on leading to lower redshift for closer galaxies? Do you know of any papers investigating and/or dismissing such idea? I know that observed redshifts are uniform irregardless of direction. Does that necessarily imply, if these are Doppler redshifts, that we must be at epicenter? Couldn't being at some point away from epicenter of large enough explosion lead to no asymmetry or to asymmetry that would be unnoticeable for us? What if epicenter of explosion was not a point? What if galaxies were like steel balls mixed with gun powder so energy that pushed that gave them kick away in the beginning was between them? Wouldn't that look uniform from the point of view of most debris that are far enough from the edge?