Starship Asterisk*

Chris Peterson wrote:
All of the Universe on the other side of the horizon the defines our observable universe is moving away from us at faster than c. That's what makes it unobservable. But those relative velocities are the product of the metric expansion of space, not of Newtonian or relativistic acceleration.

This seems inconsistent with your argument that Hubble redshift is not a Doppler effect.

neufer wrote:

Chris Peterson wrote:
All of the Universe on the other side of the horizon the defines our observable universe is moving away from us at faster than c. That's what makes it unobservable. But those relative velocities are the product of the metric expansion of space, not of Newtonian or relativistic acceleration.

This seems inconsistent with your argument that Hubble redshift is not a Doppler effect.

How so? Keep in mind that the relative velocities were much less when the observed photons were emitted. If nothing but the Doppler effect were involved, the observed shift would be much less.

saturno2 wrote:I doubt very much that an " object" traveling to c and above c

Velocities are relative. That there are objects with relative velocities greater than c is quite certain, and that does not conflict with any laws of physics.

I wish i didn't have to read what the lot of you are saying here five, six or seven times in hopes of understanding what your saying, oh well lets see if I got some of this right kind-a-sort-a. Ok two bodies moving apart (relative to each other ) could be traveling faster than C etc, etc I don’t have a problem with that it makes perfect sense.
But now so its said that when astronomers look out into space that everything; galaxies and etc, are all moving away from us. There is nothing coming towards us that would allow us to take advantage of the fact. Not one star is headed our way?

Beyond wrote:Forsooth, Von Neufer hast once again wielded his mighty Google sword at .999c and delivered to us valuable information to help keep us from making a Pfuel's fool of ourselves, should one or more of us decide to dash through the Brandenburg Gate at close to the speed of C. Hoorah! Hoorah!

You'd get a helluva case of joggers nipple... OUCH.

wonderboy wrote:

Beyond wrote:Forsooth, Von Neufer hast once again wielded his mighty Google sword at .999c and delivered to us valuable information to help keep us from making a Pfuel's fool of ourselves, should one or more of us decide to dash through the Brandenburg Gate at close to the speed of C. Hoorah! Hoorah!

You'd get a helluva case of joggers nipple... OUCH.

I'm pretty sure that something like that would be the least of the experience

THX1138 wrote:Ok two bodies moving apart (relative to each other ) could be traveling faster than C etc, etc I don’t have a problem with that it makes perfect sense.

First, shine a laser pointer to the east. Then shine it to the west. The light pulses each move away from you with c, but in opposite directions. Hence, they separate with 2c.

THX1138 wrote:But now so its said that when astronomers look out into space that everything; galaxies and etc, are all moving away from us. There is nothing coming towards us that would allow us to take advantage of the fact. Not one star is headed our way?

All stars are located within a galaxy, to which they are bound gravitationally. Some stars move towards the Sun, others move away from it. Galaxies, in turn, are usually found in clusters of galaxies, where they are bound gravitationally as well. Not all galaxies are moving away from us. For example, Andromeda is approaching the Milky Way and there will be a galactic merger in about 2 million years. The picture starts to change when you start to look at clusters of superclusters. At these truly cosmological distances (about 1.3 billion light years) you start to observe the cosmological expansion of the universe. Distances between superclusters increase with time, which is conceptually something different than superclusters moving away from each other.

THX1138 wrote:But now so its said that when astronomers look out into space that everything; galaxies and etc, are all moving away from us. There is nothing coming towards us that would allow us to take advantage of the fact. Not one star is headed our way?

Not everything is moving away from us. We only see the effects of the metric expansion of space when we look outside our own galactic cluster. And even outside that, where we see galaxy clusters moving away from us, there may be individual galaxies (in the nearer clusters) still moving towards us, or stars in receding galaxies that are moving towards us due to their orbital motion.

The point is, we don't see anything moving towards us at a substantial percentage of c (well... there may be some jets) because all motion towards us has to be the product of ordinary acceleration processes (F=ma). There is no metric contraction of space to carry things towards us without such acceleration.

Chris Peterson wrote:we don't see anything moving towards us at a substantial percentage of c (well... there may be some jets)

Jets? Are these the "jets" propelled by warp drive already discussed here, or something else entirely? I have come to expect your answers to reveal esoteric new dimensions of the universe to me each time, so just thought I'd check.

Nitpicker wrote:

Chris Peterson wrote:we don't see anything moving towards us at a substantial percentage of c (well... there may be some jets)

Jets? Are these the "jets" propelled by warp drive already discussed here, or something else entirely? I have come to expect your answers to reveal esoteric new dimensions of the universe to me each time, so just thought I'd check.

Jets of material can be ejected by black holes and other dense, compact bodies that are actively accreting material. In some cases the jets have velocities approaching c. If such a system had a pole directed toward us, we would observe material moving in our direction at relativistic speeds.

Glad I asked. But I take it there is no need for "panic shopping" just yet.

At least not from forces off world.

Thanks all and especially thank you Chris for answering my question in the manner that you have as i actually understand what you stated and i didn't even have to read it a number of times. Maybe i'm actually getting some where with this stuff in my old age

Wait a second, wouldn't the object be viable eventually like possibly be seen where it used to be a second before / 186,000 miles from where it would presently be

THX1138 wrote:Wait a second, wouldn't the object be viable eventually like possibly be seen where it used to be a second before / 186,000 miles from where it would presently be

I'm not sure I understand what you are asking.

In fact, we don't see any moving bodies in their "real" position, due to the time it takes light to travel. In most cases this doesn't matter (we don't care about how objects at interstellar distances have changed), but within our own solar system it is important to adjust the apparent position of bodies to the actual position, or we couldn't properly account for bodies affect each other and their orbits. In some cases we also have to correct the position of objects due to the aberration of light- an apparent shift created by the relative velocities of the emitter and observer.