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banquo's_bumble_puppy
2005-Mar-29, 01:40 PM
If you were to stand completely still in space and not be affected by the gravity of other bodies; how long would it take you to leave the solar system? Does this ? make sense?

Hazzard
2005-Mar-29, 01:45 PM
Not realy!

Standing still relative to what.?

And why would you think that we eventualy would "leave"the solarsystem?

Maby youre thinking that the solarsystem would "leave" us given enough time?? 8-[

banquo's_bumble_puppy
2005-Mar-29, 01:52 PM
standing still relative to everything else in our solar system...no movement...yes the solar system would leave us...how fast?

Argos
2005-Mar-29, 02:37 PM
If you were left adrift somewhere in the solar system, the solar system would drag you along with it. You would still be orbiting the sun. YouŽd still be inside the sunŽs gravity well. YouŽd become kinda planet, or, being rigorous, a small asteroid. YouŽd never be "left behind".

Movement is an intrinsic characteristic of all bodies in the universe. WeŽve inherited it from the big bang. ThereŽs no standing still. There is no absolute frame of reference.

TravisM
2005-Mar-29, 03:20 PM
But, I think the solar system is orbiting the center of the milkyway at something like 200 million miles an hour. You'd have to move, not stand still.

Argos
2005-Mar-29, 03:32 PM
But, I think the solar system is orbiting the center of the milkyway at something like 200 million miles an hour.

That would be approximately 55,000 miles per second, an appreciable fraction of c. :o

In fact, 250 km/s (900,000 km / ~600,000 miles an hour) would be a more reasonable figure.

Arkyan
2005-Mar-29, 07:40 PM
I think the hypothetical question is, if you could suddenly stop all motion relative to the core of the galaxy, how long would it take for the solar system to sweep past you.

Let us assume that our starting position is the center of the Sun itself. The sun rotates about the Milky Way at some 217 km/s. It'd take you a little over 53 minutes to emerge from the Sun itself. 7 days, 22.5 hours later you would pass the orbit of the Earth.

It would take a total of 41 days, 12 hours and 26 minutes to pass the (mean) orbit of Jupiter; just over 315 days to pass the mean orbit of Pluto; 479 days to reach the heliopause (depending on the distance); and finally, 2240 years to pass beyond the edge of the Oort Cloud (assuming a max distance of 100,000 AU).

John Dlugosz
2005-Mar-29, 07:50 PM
Don't forget that our galaxy is moving towards Andramada at a pretty good clip, so being still relative to the core of the galaxy is still not "still". And both galaxies are being dragged toward the center of the cluster, etc.

I wonder, if you average the motion to find the total momentum, as the size of the sample area increases will the result converge? Seeing how it changes based on scale might be interesting in itself!

Arkyan
2005-Mar-30, 09:50 AM
Well part of the problem is that motion is inherently relative and never absolute. You can be still in relation to the Sun, or still in relation to the Earth, but never to both since they are in turn, moving in relation to each other. From our point of view as being "stationary" on the Earth, our friend at rest relative to the galactic center seems to be moving quite fast! No matter what you have to pick a point of reference in order to be stationary.

For the thought excersize I simply assumed the original poster meant stationary in relation to the galactic center. I suppose they meant "stationary in relation to the center of the universe", in which case we'd have to factor in the motion of the galaxy, the local group, and so on to arrive at a total "apparant motion" vector in relation to the Sun. However, having access to neither the speed nor direction of each vector of motion involved, it goes way beyond me to answer that one :)

Evan
2005-Mar-30, 07:08 PM
Hmmm. If we accept that all the motions of all the objects in the universe are the result of angular momentum of something about something and we accept that the sum of the angular momentum of the universe is zero then we may postulate that nothing is moving at all, on average.

Nergal
2005-Mar-30, 07:31 PM
Don't forget that our galaxy is moving towards Andramada at a pretty good clip, so being still relative to the core of the galaxy is still not "still". And both galaxies are being dragged toward the center of the cluster, etc.
This brings up a tangental question(s) for me...

An object's red-shift is the result of how fast that object is moving away from our point of observation. That object's apparent speed is (in a grossly over-simplified way, ignoring relative angles and such) the sum of how fast it's moving away from us and how fast we are moving away from it.

Which leaves me with two questions:

(1) Is there any way to determine what "part" of the red shift is due to the movement of our observation point (i.e. Earth, Sol, Milkway, etc...)? In other words, how much of the separation velocity is the (red-shifted) object's and how much is our own movement.

(2) Does it matter? For all intents and purposes the relative motion doesn't matter.

JHotz
2005-Mar-31, 01:54 AM
I would say that all movement is relative. Absolutely stationary is therefore relative as well. Since it is relative and undefined except by your whim then stationary is arbitrary and therefore no answer can be given until you establish an objective reference.

TravisM
2005-Mar-31, 04:10 AM
But, I think the solar system is orbiting the center of the milkyway at something like 200 million miles an hour.

That would be approximately 55,000 miles per second, an appreciable fraction of c. :o

In fact, 250 km/s (900,000 km / ~600,000 miles an hour) would be a more reasonable figure.

#-o :oops:

I quote orders of magnitude off... :D

200, 250... something, something... ;)

John Dlugosz
2005-Mar-31, 05:09 PM
(1) Is there any way to determine what "part" of the red shift is due to the movement of our observation point (i.e. Earth, Sol, Milkway, etc...)? In other words, how much of the separation velocity is the (red-shifted) object's and how much is our own movement.

(2) Does it matter? For all intents and purposes the relative motion doesn't matter.

When we look at the blue-shift from the Andramada Galaxy, for example, we measure the total relative motion between Earth and it (simplifying—it is spinning so each arm shows a different speed).

If we want to find out the relative motion between the two galaxies for purposes of finding out when they will meet, we need to subtract out Earth's motions within the galaxy.

If we want to model the dynamics of the whole local group, it makes sence to normalize everything to the center of mass of the group.

So, it "matters" if there are different types of motion involved. The cyclic motion doesn't affect overall movement in the long run.

mickal555
2005-Apr-01, 08:20 AM
Wait I think we are all missing the fundimental question: how does one stand in space?

banquo's_bumble_puppy
2005-Apr-01, 01:31 PM
http://www.calphysics.org/haisch/mercury.html

Jorge
2005-Apr-01, 02:33 PM
Wait I think we are all missing the fundimental question: how does one stand in space?

by being in the exact center of it?

eburacum45
2005-Apr-01, 03:49 PM
If you stand still with respect to some object (such as the Sun, or the centre of the Galaxy, or the Great Attractor) you will no longer be in orbit around it, and you will start falling towards it.
There is no way to stand still in space unless you define what you are stanging still in respect to; as soon as you are no longer in orbit around that object you will start falling towards it and you will no longer be stationary.

Can't be done.

John Dlugosz
2005-Apr-01, 04:39 PM
http://www.calphysics.org/haisch/mercury.html



we proposed a radical theory: that inertia is an electromagnetic force that switches on whenever an object accelerates through space.

My woo-woo alarm went off at this point.

Any theory that contradicts the Standard Model has to be complete enough to explain everything just as well. It can't just explain one thing, at the expense of messing up everything else!

Arkyan
2005-Apr-01, 07:27 PM
If you stand still with respect to some object (such as the Sun, or the centre of the Galaxy, or the Great Attractor) you will no longer be in orbit around it, and you will start falling towards it.
There is no way to stand still in space unless you define what you are stanging still in respect to; as soon as you are no longer in orbit around that object you will start falling towards it and you will no longer be stationary.

Can't be done.

Which is why we call this a hypothetical thought experiment 8)

eburacum45
2005-Apr-01, 07:45 PM
Well, alright;
as a thought experiment, let's say you are suddenly stationary with respect to the Cosmic Microwave Background Radiation;
you are suddenly moving at 600 km/s with respect to the Earth, and you will reach the Heliopause (14.3 billion miles away, one measure of the edge of the Solar system) in 276 days.

Quite a turn of speed, but the Solar system is very big.

um3k
2005-Apr-01, 09:07 PM
Well, alright;
as a thought experiment, let's say you are suddenly stationary with respect to the Cosmic Microwave Background Radiation;
you are suddenly moving at 600 km/s with respect to the Earth, and you will reach the Heliopause (14.3 billion miles away, one measure of the edge of the Solar system) in 276 days.

Quite a turn of speed, but the Solar system is very big.
Wow. Now if only we could do that, and then do the opposite when our destination reaches us.

Tacitus
2005-Apr-02, 04:05 AM
Since we seem to be discussing where we are relative to the Universe, it is the perfect time to reference Monty Python's version of the Total Perspective Vortex....

The Galaxy Song (http://www.gecdsb.on.ca/d&g/astro/music/Galaxy_Song.html) by Eric Idle.

TravisM
2005-Apr-02, 05:43 PM
600 km/sec? That's only 2 times c... 8)

:lol:

Again with the order of magnitude?

A Thousand Pardons
2005-Apr-02, 07:15 PM
600 km/sec? That's only 2 times c... 8)

D*ng it, now I have to memorize the speed of light (http://www.xs4all.nl/~jcdverha/scijokes/11_4.html#6) again: "An ingenious astronomy student remembers my easy light mnemonic"

mickal555
2005-Apr-03, 06:03 AM
C= 300, 000 km/sec

eburacum45
2005-Apr-03, 07:17 PM
It works out as 0.002c, I believe, but that is still rather fast.

TravisM
2005-Apr-04, 01:04 PM
600 km/sec? That's only 2 times c... 8)

D*ng it, now I have to memorize the speed of light (http://www.xs4all.nl/~jcdverha/scijokes/11_4.html#6) again: "An ingenious astronomy student remembers my easy light mnemonic"

:lol:

Dang is right. 300,000,000 meters per second, or 300,000 km per second, none of wich equals 600 km/sec ( my c*2 ... )
I have to get a cheat sheet so I quit doing this. I've been posting magnitudes off for weeks now. :oops:

CJSF
2005-Apr-04, 08:25 PM
Didn't Asimov write a short story that touched upon this topic? I seem to remember someone managed to generate an anti-gravity field, so that an object in it would be subject to NO gravity from any other object. It resulted in a billiard ball travelling through a competing scientist and out the building and on at c. The good doctor later commented that of course the entire ball wouldn't stay intact until it was in the anti-grav field - once the first atoms hit the field, they'd zip off a c, but he liked the dramatic effect in the story.
I'll have to find that story again somewhere. It may have been in an old Asimov's Sci-Fi mag.

CJSF

Kaptain K
2005-Apr-06, 03:45 AM
The story is The Billiard Ball. It was not so much an "anti-gravity" field as an "inertia dampinig" field. The central idea being that when the inertial mass was reduced to zero, the object would (like a photon) immediately take off at the speed of light.

CJSF
2005-Apr-06, 01:40 PM
Thanks Kap'n! But it would be because it's inertial mass was zero that it wasn't affected by gravity, right? Well, anyway, it'll be good to read the story again. Time for a trip to the library!

CJSF

John Dlugosz
2005-Apr-06, 07:33 PM
The Billiard Ball was a 1967 short story by Isaac Asimov, originally collected in The Best of Isaac Asimov.

An example of Asimov's "late style", the story is a journalist's recollection of the events surrounding the discovery of an anti-gravity device. Heavy with physics theory, the story describes relationship between the creator of the device, who is killed during its initial demonstration, and his former classmate, a scientist who had discovered most of the theory to make the device possible.

From Wikipedia (http://en.wikipedia.org/wiki/The_Billiard_Ball).