If the universe is expanding at a constant rate, how far does the earth move in a year?

Question

As per answer below, it's likely that the rate isn't constant. Still, is there a best guess how far the earth would be from its current position today in a year's time?

As per answer below, it's likely that the rate isn't constant. Still, is there a best guess how far the earth would be from its current position today in a year's time (with respect to the center of the universe)?

Answer 1

Easy answer: we do not know.

It is like living on the surface of a ball which is expanding: the centre of the ball does not belong to the surface. Yet, the expansion we witness is the expansion of the surface; it is from that expansion that we conclude that there must be some expansion from a centre.

With a ball, we (3-D creatures) can measure the diameter of the ball. Imagine tiny 2-D creatures living on the surface of the ball (unaware of the third dimension: they have no up or down). They'd have a hard time determining the radius of their ball, therefore they would have a hard time determining how fast they are moving away from a centre that is not located in their (visible) universe.

We are the same way, except that our Universe is a 3-D space, 'wrapped' around a 4th dimension. The centre of the universe is not in the universe.

The radius of the universe could be infinite (the most recent data from WMAP has eliminated most possibilities of a relatively 'small' radius for our universe). If the radius is infinite AND the expansion rate is finite (not infinite), then the percentage of expansion is exactly 0%. (Any finite number divided by infinity is equivalent to 0).

To put it in another way: if our distance to the centre of the universe was infinite last year, it is still infinite this year. Most cosmologists believe that the radius is infinite.

There is still a small possibility that the radius is not infinite. However, we do not know how large it would be (except that it would be much larger than the 'tiny' 13 billion light years that we see.

Answer 2

Neither the Earth nor anything else *moves* as a result of the universal expansion. The universal expansion is a stretching of spacetime itself, *between* objects in the universe. Galaxies are not streaming through space; space is expanding between the galaxies.

There is no center to the universe. The universe is unbounded, and perhaps infinite in size. Galaxies are not emerging from a central explaosion that thrust them outwards into emptiness; the universe is filled equally with galaxies everywhere, but the distances between them are increasing.

Answer 3

One of the least understood effects is the observed expansion of the universe...the red shift. I like this analogy...picture a balloon with white dots painted on its skin. Now blow the balloon up so it has its spherical shape.

The white dots are the galaxies on our universe, which is the skin of the balloon. Continue to blow up the balloon, the white dots get farther and farther away from each other. Not because they are moving away from each other, but because the skin (the universe) is stretching out between them.

So, to answer your question, the Earth, as a part of the Milky Way Galaxy does not move due to the universal expansion. What moves is space around it.

Galaxies do and are currently colliding. But those collisions are due to their own motions and not that of the expanding universe. Andromeda and our own galaxy, the Milky Way, are scheduled to collide a long long time from now. Still, over all, galaxies are getting farther apart due to expanding space...that big balloon.

Answer 4

It all depends on your point of view. To an observer 13 or 14 billion light years away we would be moving (along with the Milky Way galaxy) at nearly the speed of light, which works out to about 9.46 X 10^12 km per year.

To an observer on the earth we only know we are moving about the sun at about 30 km/sec, or 946 million km/year.

The sun revolves about the galactic center every 250 million years or so, and we are about 30,000 light years or so from the galactic center. So, these figures yield about 190,000 light years in 250 million years, or 8.1 billion km/year if my math is correct (diameter X pi = circumference).

To an observer in the Great Nebula in Andromeda we are moving at a rate of about 1200 km/sec toward him/her.

So, you see, there are multiple answers to your question (I apologize if my math is incorrect).

Answer 5

A question like this depends on your frame of reference.

The Earth goes around the Sun once per year, making a not-quite-circular path around 6 AU long.

But the Sun also goes around the Milky Way, and the Milky Way moves relative to other galaxies.

So, the answer is "with respect to what?"

Answer 6

The latest estimate of Hubble’s Constant is 70 km/Mpsec/sec and increasing; in other words, an object one megaparsec away gets 70 km farther away each second. Converting the HC to standard MKS units, you get 2.4 x 10^-18/sec; in other words, every second another 2.4 x 10^-18 meter is added to every meter in the universe; in terms of volume 1.4 x 10^-55 cubic meter is added to every cubic meter in the universe every second. That increases the Earth’s diameter about one hundredth of a millimeter per year. But the new space doesn't stick around long enough to get measured or noticed; right down to quarks, every object adjusts to its proper size; the new space ends up between galaxies.

At distances of billions of light-years, the expansion is apparent as red shift because it is greater than all other motions; but within our galaxy the stars and spiral arms simply adjust to the new environment, and the new space gets squeezed out into intergalactic regions.

In my own Fractal Foam Model of Universes, the expansion of space is explained as the un-popping of bubbles in the ether foam. The bubbles that make up our ether foam are the great voids in the cosmic foam of the sub-universe. The sub-universe is expanding, just as our universe is, and that causes its bubbles to pop; but the sub-universe is operating in reverse time, so from our point of view the bubbles are un-popping. Each time one of those bubbles un-pops, approximately one Planck volume of new space is added to our universe; this happens about 10^50 times per cubic meter per second.

P.S.: Every point in the universe is the center. That is true in the Big Bang conjecture, and it is true in any infinite universe model.

Answer 7

The latest says it is not expanding at a constant rate.