- #1
Simetra7
- 39
- 0
When the HST looks out into the far off regions of space, the data it receives (the light from distant galaxies etc.), has been traveling for millions of light years. When this data shows red shift, and therefore that the source of the light is moving away from us, does this mean that at the time that light was emitted (millions of light years ago), its source was traveling at the velocity indicated by the red shift, or does the red shift indicate the velocity of the source of the light at the present time? If we can only measure the velocity from the time the light was emitted, then how do we know whether the source is still moving away from us or not?