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13.7 billion years is long enough
![[Sloan Digital Sky Survey] Redshift 5.0 quasar. That faint red dot represents an object a hundred times brighter than a typical galaxy.](2003-06-06-quasar.gif) Q:
I believe you are mistaken when saying a quasar is 27 billion light years away
from us, as there is nothing in the universe that is currently farther away than
about 13.7 billion light years away as this is currently the approximate age of
the universe, and light can’t travel any farther than that, thus there hasn’t
been time to see anything 27 billion light years away. ------Gerry
C, Burlington, Vermont.
[Sloan Digital Sky Survey] Redshift 5.0 quasar. That faint
red dot represents an object a hundred times brighter than a typical galaxy.
A: But wait. The quasar light was only 4 billion light years away when
it started toward us. So, the light had time to reach us. That’s the
light we are seeing now.
You are right about the light the quasar is presently emitting. Light
from the 27-billion-light-year-distant object has not had time to reach us.
How did the quasar get 27 billion light years away in only 4 billion years?
Space is expanding at greater than light speed.
"For a redshift 6 quasar, that means that the Universe has expanded by a
factor of 7 since the quasar emitted its light," says Andrew JS Hamilton,
astrophysicist at the University of Colorado.
For each mile that a quasar photon moves toward us, it must now travel an
additional 5.8 miles due to expanding space.
Further Surfing:
WonderQuest:
Expanding space
Andrew JS Hamilton,
University of Colorado: Universe growth factors
(Answered June 6, 2003)
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