Other founders of the "Golden Age" of Sicience Fiction

[AnotherCat]

For those interested with an open mind and not just wanting to be argumentative I came across this explaining the Ant on a rubber rope paradox.

It explains how if an ant walks along a rubber rope that is expanding in length at a constant rate faster than the ant is walking, the ant will still reach the other end because the mathematical series that describes the ants progress does not converge. So it shows how something travelling towards one at a speed less than the expansion of the medium it is travelling along will eventually reach one even in our own local flat world.

It goes on to briefly use this example to put into intuitive terms why light from galaxies travelling away from us faster than the speed of light will still reach us - I am not sure this takes into account of the less intuitive parts of general relativity, but the effect lives.

It points out that the universe's expansion is believed to be actually accelerating (and the actual rate seems to be up for grabs at the moment) and so that places a limit on the visibility of the furthermost of those "faster than the speed of light" galaxies but those within that limit will be visible (and are, their red-shifts have been measured).

[arjaybe]

The Milky Way is moving at about one-fifth of one percent of the speed of light.

[arjaybe]

Originally Posted by AnotherCat

For those interested with an open mind and not just wanting to be argumentative I came across this explaining the Ant on a rubber rope paradox.

It explains how if an ant walks along a rubber rope that is expanding in length at a constant rate faster than the ant is walking, the ant will still reach the other end because the mathematical series that describes the ants progress does not converge. So it shows how something travelling towards one at a speed less than the expansion of the medium it is travelling along will eventually reach one even in our own local flat world.

It goes on to briefly use this example to put into intuitive terms why light from galaxies travelling away from us faster than the speed of light will still reach us - I am not sure this takes into account of the less intuitive parts of general relativity, but the effect lives.

It points out that the universe's expansion is believed to be actually accelerating (and the actual rate seems to be up for grabs at the moment) and so that places a limit on the visibility of the furthermost of those "faster than the speed of light" galaxies but those within that limit will be visible (and are, their red-shifts have been measured).

The light that reaches us was emitted by the galaxy before it reached the threshold. The light it emits after crossing the threshold will never reach us because the intervening space is expanding by more than a light year per year. In no case is any of the galaxies moving at anywhere near light speed.

[fjtorres]

Originally Posted by arjaybe

The light that reaches us was emitted by the galaxy before it reached the threshold. The light it emits after crossing the threshold will never reach us because the intervening space is expanding by more than a light year per year. In no case is any of the galaxies moving at anywhere near light speed.

Like a ship sailing away until it goes beyond the horizon.

Once the galaxy passes the universal horizon it effectively becomes part of another universe in a type 1 multiverse.
If we could track a galaxy crossing over it would be really cool.

[AnotherCat]

Originally Posted by arjaybe

The Milky Way is moving at about one-fifth of one percent of the speed of light.

You do not give what frame of reference you are using in stating that speed, it is meaningless unless you state a frame of reference.

However, I will assume that you are referring to our galaxy's motion against the cosmic background radiation (the radiation remnant of the "Big Bang") which approximates the figure you have given. If that is the case then the speed you quote has nothing to do with the expansion of the universe, it is a local effect due to the gravitational influence of other nearby galaxies and matter.

EDIT: added "it is a local effect"

[arjaybe]

Originally Posted by AnotherCat

You do not give what frame of reference you are using in stating that speed, it is meaningless unless you state a frame of reference.

However, I will assume that you are referring to our galaxy's motion against the cosmic background radiation (the radiation remnant of the "Big Bang") which approximates the figure you have given. If that is the case then the speed you quote has nothing to do with the expansion of the universe, it is a local effect due to the gravitational influence of other nearby galaxies and matter.

EDIT: added "it is a local effect"

Exactly, and the expansion of the universe doesn't impart any speed to galaxies' motion. While distant galaxies appear to be moving away from us at high speeds, they're not actually moving that fast, any more than we are, even though we appear to be to them.

[AnotherCat]

Originally Posted by arjaybe

Exactly, and the expansion of the universe doesn't impart any speed to galaxies' motion. While distant galaxies appear to be moving away from us at high speeds, they're not actually moving that fast, any more than we are, even though we appear to be to them.

I think you need to review what has been said and do some research from informed sources. From any point in the universe the universe is expanding away from it. The distance to other distant galaxies from that point is increasing with that expansion and so they are speeding away from that point and so from all other galaxies. That is what we have been saying.

If you do not believe that with expansion the galaxies are speeding away from each other because of expansion then look up the simple single surface model of points on a balloon being blown up (and so expanding the surface) speeding away from each other, that is often given as an example.

Galaxies do not have high velocities against the cosmic background radiation because the microwave cosmic background is expanding too (hence why it has cooled so much from its origin at the time of the "Big Bang"). (EDIT: perhaps your difficulty in understanding what is being said is because you do not realize that point?).

If you believe anything other than the above then your belief is contrary to the current expansionary models. If you do believe that, then you have completely misunderstood what has been posted and so have been arguing against it in vain.

At this stage I give up with you.

[Greg Anos]

A more interesting question is where is all the new space-time coming from?

[davidfor]

Originally Posted by Ralph Sir Edward

A more interesting question is where is all the new space-time coming from?

I suspect it is the same place my socks keep disappearing to. There s probably some conservation law happening.

[AnotherCat]

Originally Posted by Ralph Sir Edward

A more interesting question is where is all the new space-time coming from?

Our cats seem to know but won't tell us.

Whoops, am getting confused, it is spaced-out time that they have mastered.

[GlennD]

Somehow the notion of the cats being in charge doesn't seem all that far fetched.

[Greg Anos]

Originally Posted by GlennD

Somehow the notion of the cats being in charge doesn't seem all that far fetched.

You can get cats to fetch?

[arjaybe]

Originally Posted by Ralph Sir Edward

A more interesting question is where is all the new space-time coming from?

You're right. It just seems to appear between everything.

[dwig]

Originally Posted by GlennD

Somehow the notion of the cats being in charge doesn't seem all that far fetched.

Well, according to that wholly remarkable book, the Hitchhiker's Guide to the Galaxy, it is the white mice that are in charge, not the cats.

[arjaybe]

Originally Posted by AnotherCat

I think you need to review what has been said and do some research from informed sources. From any point in the universe the universe is expanding away from it. The distance to other distant galaxies from that point is increasing with that expansion and so they are speeding away from that point and so from all other galaxies. That is what we have been saying.

If you do not believe that with expansion the galaxies are speeding away from each other because of expansion then look up the simple single surface model of points on a balloon being blown up (and so expanding the surface) speeding away from each other, that is often given as an example.

Galaxies do not have high velocities against the cosmic background radiation because the microwave cosmic background is expanding too (hence why it has cooled so much from its origin at the time of the "Big Bang"). (EDIT: perhaps your difficulty in understanding what is being said is because you do not realize that point?).

If you believe anything other than the above then your belief is contrary to the current expansionary models. If you do believe that, then you have completely misunderstood what has been posted and so have been arguing against it in vain.

At this stage I give up with you.

Don't give up AnotherCat. Keep your eye on the spot on that balloon closest to you and you'll see that it isn't moving, even though the space between the spots is increasing. It's the same for every spot. None of them is moving but they're all getting farther apart, the more distant ones at a higher rate. The growing space between them makes the other spots appear to be speeding away, while none of them is actually moving. Within its limits, the balloon is a good three dimensional analogy for four dimensional spacetime. Distant galaxies appear to be speeding away because of the growth of space between us and them.