Ask A Scientist© Astronomy Archive

Author:      kris whelan, amit srivastava, jeffrey m ulmer, burbank school
If the universe is expanding, what is it expanding into?  In other words how
does one define the universe?  

Response #:  1 of 4
Author:      jasjeet s bagla
By definition, Universe includes everything therefore there is no question
of its expanding into something.  An example which is easy to grasp is that
of surface of a balloon.  If we were two dimensional creatures restricted to
surface of a balloon then we will see the "Universe" (balloon) expand.  This
example does not convey the whole richness of possible universe, as there
can be universes which are infinite in spatial extent which can stretch as
time goes on.  No matter how much stretching the universe goes through, it
can not have a size larger than infinite!

Response #:  2 of 4
Author:      jasjeet s bagla
It seems that the Universe is infinite in extent.  If it is not then the
most likely form is that of surface of a sphere but in higher dimensions
(Surface of a sphere in 4 dimensions).  In that case, it is finite without a
boundary - just like the surface of a football or that of Earth.

Response #:  3 of 4
Author:      samuel p bowen
No one has a picture from a telescope that shows the end.  So, no one really
knows.  As far as we know for the present, it does not end.  

Response #:  4 of 4
Author:      unterman
Space and time exist within the universe.  The universe does not exist
within space.