Maybe this is not possible to determine because of the nature of the universe, what with “curved space,” and/or the question of objects moving away from each other versus space itself expanding, and the limits of our observational abilities. But I’m wondering if we have determined where we are relative to the rest of the universe, particularly where we are relative to the origin of the Big Bang.
Maybe not possible to figure out, since no matter where you are in the universe, it appears that everything (or at least space) is moving away from you at a rate proportional to its current distance from you. But I ain’t no astronomer, so what do I know? Not much.
There is no center of the universe, and the origin of the Big Bang was everywhere.
On the other hand there are galactic velocities that are not caused by the expansion of space, so I suppose one could calculate the speed of the Milky Way with regards to everything else and calculate how far we’ve moved, but I’m not sure how interesting that would actually be and how far back the current straight line speed remains a valid estimate.
There is no “center” of the universe, as far as we know.
As an analogy, if you inhabited a 2-D universe that took place on the surface of an expanding balloon , you wouldn’t be able to locate a center either- everything would be speeding away from everything else.
It happens to be smack dab in the center of the Observable Universe as seen from Earth. But as said above, everything we know about cosmology is that the Universe is likely far far bigger and there is nothing special about our position in it.
Monty Python tell me we’re 50,000 miles from galactic central point, and everything else in the Galaxy Song that I’ve looked up is susprisingly true, so there’s one answer.
To expand on this and previous answers, the ‘center’ of the universe, i.e. the point at which the originally existed, is everywhere. By definition, all space was compactified into the singularity, and the subsequent inflation stretched out the universe to its currently observable boundaries and beyond, the extent of which may be infinite. (We cannot tell what is beyond the visible horizon, but we are pretty confident due to WMAP survey data that the visible universe does not fold back upon itself, so it is at least larger than the volume we can observe.) So every point in the universe is the center…from the observer’s point of view.
This is not to say that we cannot measure out displacement relative to the mean flow of observable mass (sometimes referred to as the dark flow or peculiar velocity as distinct from the the isentropic Hubble expansion) and the Cosmic Microwave background, and in fact the net speed of the the Milky Way galaxy is estimated to be about 545-560 km/s relative to the mean flow. This was once thought to be toward a gravitational source called The Great Attractor, in the diection of thr Hydra-Centaurus Supercluster (which cannot be directly obeserved as it is occluded by the Milky Way), but recent analysis indicates that the source lies beyond there any may be outside of the observable universe entirely.
To think of it another way, and reducing the four dimensions of spacetime by one, imagine that we all started out on the surface of a very tiny balloon, so that everything was essentially at one point. As the balloon inflates, the skin (which represents the three spatial dimensions as a two dimensional field) expands away from the temporal origin (the center of the balloon), and points become more distant even though they do not move relative to a local coordinate frame. One can think of “local” structures such as galaxies and superclusters as being pieces of popcorn stuck to the surface of the balloon, and therefore not strongly affected by global expansion. As the balloon expands, some of the surface eventually goes beyond the horizon of what can be observed; the distance to the the horizon is the same at all points, but shifts with respect to the reference of the observer. The ratio of curvature to radius to the (temporal) center is roughly analogous to the rate of change of flow, such that things that are once observable eventually disappear over the horizon. This isn’t a perfect analogy,of course, because it doens’t include consideration of the speed of expansion relative to relativistic limits, but it provides a visualizable model that bears a reasonable similarity to what we understand about expansion.
Yeah. It’s like trying to identify the midpoint of the circumference of a circle.
A straight line segment has a midpoint. But bend that segment into a circle and join the ends, and voila—it no longer has a beginning, an end, or a middle.
Our galaxy, on the other hand, is a finite sort-of-flattish sort-of disk, and disks have centers, so we can tell how far we are from the center of the galaxy, more or less.
And similarly, we can tell that our galaxy is actually quite close to the gravitational center of the Local Group or neighborhood cluster of galaxies. We can also tell sort of where we are in the next larger district, the Virgo Supercluster.
But we can’t locate ourselves with respect to some “center of the Universe”, because the Universe is “shaped” sort of like the surface of a sphere or similar objects that have no beginning, end or middle.
[ETA: Man, this post uses “sort of” a lot. That’s cosmology for ya.]
Can you explain just a little bit these two statements about how we can tell about (current?) peek-a-boo relations and --I think as in the second excerpt here-- fossil tracks of action in a 4-D volume larger than we can observe?
I am aware another thread is also chugging away now on the definition of observable universe, and this intersects nicely with that.
What really bakes my noodle is, if I have this right, the Milky Way is right at the center of the universe (and our Sun is also at the center…and so is the Earth…and, now that I think about it, so am I!! Not really surprising, that last bit). And so are all the other galaxies in the observable universe, in so far as ‘center’ has any meaning when talking about the universe. :eek: