Jinto

Actually, saying it's gravity is not implying causation at all. All gravity is is a verified mathematical relationship between the motions of objects with mass (whatever that is). How do you get causality out of that?
-----------------------------------------------------------------------------
Semantics: impeding logical arguments since the beginning of time (whatever that may be).

xian

no one has "demonstrated" that all movements require a cause. (initial force). you are simply assuming that a body in motion requires a cause.

Now, i have no problem with this.

what I am curious about is why this assumption of causation?

Psycho Economist

We have some thing A
We have some influence B
We have two states of nature: C & D.

Where we see A without B, we observe C.
Where we see B applied to A, we observe D.

B is necessary and sufficient to explain why we see C instead of D. An observation from which we can infer causation. Anything else is inconclusive for an argument about causation.

Specifically, here, A is massive bodies, B is outside force, C is rectilinear motion of constant velocity and D is acceleration (any change in velocity).

Given massive bodies and no perturbing force (think of a ball on a tabletop), it will move with constant velocity. Probably a constant velocity of zero. You can sit there all day, and it won't move. We're observing inertia.

Push the ball and it moves. You've applied a force, and we've witnessed the ball accelerate, and take on a new constant velocity. Eventually, the interaction of the ball and the tabletop will produce a frictional force that will accelerate (negatively) the ball back to a stop.

Backwards. The supermassive black hole is assumed because of X-ray emissions coming from the center of the galaxy that are consistent with the emissions one would expect from a very massive black hole. The stars whirl around each other because of their mutual gravitational attraction, collapsed dead star in the middle or not.

When you master basic velocity, acceleration and classical forces (e.g. gotten a C or better in a high school / junior college physics class), come back and we'll talk about this one. No offense, but without a basic understanding of what happens with and without force, you're not going to make sense of intergalactic motion.

Remember, the Big Bang and expanding universe weren't contrived by some atheist conspiracy to explain away your deity. They were constructed to explain astronomical observations in light of what we knew about classical mechanics. That they provide an explanation of where the universe may have come from that doesn't necessitate God and a firmament and six days of creation is an accident.

Tom Sawyer

I think we can assume that gravity is causing movement in the Andromeda galaxy because it fits the facts.

We know how gravity makes things move by observing its effects about us. These effects can be mathematically described. By using those same mathematical descriptions, we can calculate that various things should happen in the Andromeda galaxy. If, through observations of the Andromeda galaxy, those calculations hold up to how it is actually moving, then it is reasonable to assume that gravity is causing that movement. This is what has happened.

Of course, it is possible that we are wrong. The movement in Andromeda may be caused by some factor that our calculations have not taken into account. It may be moved by the Hand of God or it may be moving as a result of a basketball game between interstellar elves. Both are possible - however both are unlikely. The fact that all the evidence supports that gravity hypothesis and does not support the interstellar basketball hypothesis gives the conclusion that the gravity hypothesis is much more likely. If additional evidence emerges that favours the basketball hypothesis (ie all the movement stops while one star takes a foul shot), then we would have to reevaluate the evidence. Until then, though, it is reasonable to conclude that the hypothesis that the evidence supports is the correct one.

xian, you seem to be making the assumption that just because science cannot prove anything with 100% certainty - but only to a reasonable degree of certainty based on available evidence - that any conclusion drawn with it is no more valid than any other possible conclusion that is less supported by evidence. The more evidence there is to support a hypothesis, the more credibility it gains at the expense of competing hypotheses and there is enough evidence to support the gravity hypothesis in relation to Andromeda at the expense of any other hypotheses as to what causes that movement. We may be wrong about this, but until additional evidence surfaces to show how gravity is not the cause of the movement, we can reasonably say that it is the cause. If you have some evidence, please present it. Just pointing out that we do not know anything to 100% certainty contributes nothing to cast doubt on gravity causing movement in Andromeda.

xian

but you are assuming #2: "we have some influence B" when peering into the andromeda galaxy, and even our own galaxy for that matter.

In addition, you are also making the assumption "FOR ALL A....for ALL B..."

But in the case of stars that spin around our galaxy, there is no locally proven "cause" other than an assumption that there is a cause. When stars were observed spinning around the center of the galaxy, a cause was automatically assumed.

Bad science?



in reference to the andromeda galaxy:

A is massive bodies....B is an ASSUMED FORCE.....C is motion....D is acceleration


well most certainly if you push the ball it will move. but if you come upon a moving ball, what reason do you have to assume it was pushed? Simply because if you push a stationary ball and it moves, therefore all moving balls were pushed? Is that it? Sounds like you are eliminating the possibility of uncaused events.

It is not backwards. SUpermassive blackholes were "proven" due to motions of stars at the center of the Andromeda galaxy. This was the first proof for such a theory. But that is besides the point: X-ray emissions are given off in large quantities as matter is supposedly engulfed by a black hole.....we detect X-ray emissions and assume that those emissions were caused. Why? Maybe those emissions fluctuated into existence from the void? Why assume those emissions are caused by some unseen thing?


none of this is countered by what I am saying. If you apply force to something, it WILL be effected. What I am saying, however, is that if you observe an effect, how does that necessitate a cause?

expanding galaxies = initial force = assumption of causation. what kind of science is that? i didn't think scientists assume causation.

Wyz_sub10

You needn't assume #2 for this to work. You can observe 'A', and can observe 'C' and 'D'. The next steps is identifying the a distinguishing feature.

If the feature is potentially 'B', and that would be consistent with other observations where 'B' was observed to the same effects, then it is reasonable to conclude that the distinguishing feature in this case is indeed 'B'.

Also, it is not necessary to make "all" statements - only "all" in such case that it has been observed where the presence of 'B' would distinguish C and D, and where same holds true in theoretical obeservations.

xian

I push a ball, ball rolls.
I can do this repeatedly and observe it. Everytime I push a ball, ball rolls.

I see a ball that is rolling, therefore ball = pushed?


that seems to me what you are saying.

Wyz_sub10

Do not forget, I am saying it has to be consistent with observations producing the same effects - perhaps more than one observation, perhaps more than one effect.

You are suggesting that a rolling ball can have more than one cause. This is true, of course.

In the case of Andromeda, however, it is not simply a matter of seeing the galaxy swirl and attributing to it the only known cause.

It is a matter of how that galaxy swirls, the relationship of mass to gravity at smaller scales (i.e. planets), understanding that relationship when viewed locally (say, earth moon) and understanding the particulars of those relationships. If the particulars match, then one can reasonable assume the cause.

In your ball example:

You see a ball rolling. Pushed? Maybe not.

You see a ball rolling, uphill, away from a child who is in a physical postion consistent with having rolled a ball. The ball is not too heavy for him to roll, and the speed at which is travels up the gradient is within the range expected for a child of his size and strength.

Now pushed? Probably.

Feather

All other things being equal, would you assume some other reason for the ball's motion than it having been "pushed" given your scenario?

And that's rather the whole point.

We observe "gravity." We observe it all over the place affecting everything with mass/energy. We then observe something far far removed from immediate locality behaving in a particular way. We try out "gravity" to see if it describes the new observations. We find that it does. Therefore we "assume" gravity is in fact the cause.

It isn't some forced "by definition" type scenario, as you seem to suggest. Nothing is ever assumed. It is proposed that "gravity" explains the observations related to the galaxy Andromeda. It just so happens that the explanation of "gravity" actually matches the observations. The conclusion is that "gravity" is at work there.

That's the process. No assumptions necessary. Just a good guess based on past experience.

Psycho Economist

First, and this has been driving me up a wall: there is no such thing as "inertial force". Inertia is what is observed in the absence of forces... that is to say inertness, no change in acceleration.

Second, most importantly: it is not axiomatic in science to "assume no causation". Alternatively, it is axiomatic to "not assume what is not established as necessary, given the data." Go home, crack open a science book, and keep your nose in it until you get that important distinction.

Thirdly, I was not refering to gravity specifically in my general case. Read over it again.

If: ((A & !B) -> C), and ((A & B) -> D)
Then: B is necessary and sufficent to get D out of A instead of C. This is how causation is defined! I don't care what A, B, C and D are.

If ((A & !B) -> D, anyway) ever, or ((A & B) -> C, anyway) ever, then we don't know enough to say a thing about causation one way or another. In the case where ((A & !B) -> D), B is clearly not necessary to get D out of A. In the case of ((A & B) -> C, anyway), B is clearly not sufficient to get D out of A. We're left with an inconclusive situation.

But if we've established that B is necessary and sufficient to get D out of A, then when we observe A & D, it means B was present, and when we observe A & C, it means that B was absent.

Mass & No Force -> Constant velocity
Mass & Force -> Change in velocity, acceleration.

We observe acceleration when we see andromeda spin, so we can infer there is some force. Gravity fits the bill, given what we've figured out about it so far:

1. Gravitational force pulls massive things together towards their centers of mass.
2. All massive things have gravity in direct proportion to their mass.
3. Gravitational effects decay over distance.

Fourth, again, you're getting hung up on the issue of galaxies. Do the experiment with the ball on the tabletop. Tell me how long (on a level tabletop, negating gravity) it takes for the ball to move without any forces applied to it.

In the absence of forces from outside some frame of reference, we observe constant velocity of the body within the frame of reference. Given forces applied to a body in the frame of reference, we observe acceleration with respect to the frame of reference. End of story.

Lastly, I get the impression that you're trying to advance an existance of God by first cause argument... none of us is that dumb that we can't see through this. But here's the thing: we can observe what happens in the presence and absence of forces. If your god is as ineffable as he would have to be for us not to know he exists, then we cannot know whether we are in the God-exists or the God-does-not-exist condition. So we can't tell if we're dealing with ((A & B) -> D) or ((A & !B) -> D, anyway). Where A = void, B = god, D = universe.

Since we therefore cannot establish your god as necesasry for the universe's existance, we do not assume he exists. You're free to believe we're in the (A & B) condition in the absence of any conclusive evidence... we're just more strict about verifying B is necessary for D before we conclude B is present upon observing D.