LITERALLY No Velocity...

[Matuchkin]

1 hour ago, KerbMav said:

Although, if you really manage to fix something in space ... shouldn't everything else be drawn towards it?

Why? Doesn't that depend on mass?

5 hours ago, RainDreamer said:

Heat death of universe?

I'm not sure that heat will balance itself throughout the universe merely because of a small object standing still somewhere in it.

[KerbMav]

1 hour ago, 073198681 said:

Why? Doesn't that depend on mass?

Where did you specify that your object has no mass?

[Chakat Firepaw]

23 hours ago, 073198681 said:

Everything we know moves at a huge velocity. The planets orbit around our solar system, our solar system moves around other systems and orbits Sagittarius A, Sagittarius A moves around other galaxies and expands with them...

What if an object was literally standing in one spot, not moving? It will be standing completely still in space. What do you think will happen?

The question is meaningless given our current knowledge of physics.  There is no such thing as "standing completely still in space," as that would require there to be a single base reference frame for the entire universe.

Now, if you were to take some inertial reference frame and propose a stationary object in that frame, (perhaps it's being pushed by some extra-universal force), you have something meaningful but not particularly interesting:  You have a mass at the one point that generates gravity and makes a few equations relating to it a bit easier to solve.

[Bill Phil]

Is everything stationary, or is it just the object as a whole?

[Matuchkin]

4 hours ago, KerbMav said:

Where did you specify that your object has no mass?

Nowhere. I should have thought this thread through.

Okay, enough. I'll see for any suggestions on what I could have written in the topic (to make this thread more planned), then, I'll ask for this thread to be locked and start a new thread with the same topic, but more revised.

Who agrees?

[KerikBalm]

There exist at least two objects in the universe which have non-zero relative velocity.

Therefore, it is impossible to add a third object which displays zero relative velocity to both of those two at once*

Therefore it is impossible for an object to have no velocity relative to something else in the universe.

*assuming no funny stuff with curved spacetime, or warp drive like things where space is expanding/contracting in some areas but not others, etc.

[K^2]

1 hour ago, KerikBalm said:

There exist at least two objects in the universe which have non-zero relative velocity.

Therefore, it is impossible to add a third object which displays zero relative velocity to both of those two at once*

As I've explained a number of times in this thread alone, this is not true.

[Sandworm]

The assumption is that the only relevant velocity is with other objects within this universe.  Under multiverse schema it may be that relative velocities between universes establish some sort of baseline, that universes move relative to each other in a dimension we cannot appreciate but that nevertheless has influence.  I've read at least one paper suggesting this as a proposed dark energy.

[swjr-swis]

9 minutes ago, Sandworm said:

The assumption is that the only relevant velocity is with other objects within this universe.  Under multiverse schema it may be that relative velocities between universes establish some sort of baseline, that universes move relative to each other in a dimension we cannot appreciate but that nevertheless has influence.  I've read at least one paper suggesting this as a proposed dark energy.

We may already have collided with another universe.

[RainDreamer]

12 hours ago, 073198681 said:

I'm not sure that heat will balance itself throughout the universe merely because of a small object standing still somewhere in it.

I didn't read the OP properly and was thinking you mean literally no velocity exists for anything anymore.

[lajoswinkler]

Zero relative to what? When discussing speed and velocity, you always have to note the frame of reference.

Thing is, there aren't privileged frames of reference in the universe, at least not any we know of.

[KerikBalm]

On 1/12/2016 at 2:03 AM, K^2 said:

Trivial example, picture a bunch of objects on a rotating table. They are all in motion with respect to each other from perspective of any inertial frame. But in a rotating frame of reference, they are all at rest with respect to each other. General Relativity allows me to generalize this notion for arbitrary relative motion.

In this example, the distance between said objects does not change at all. If they have relative velocity such that their distance is changing... it becomes rather hard without "funny stuff" like I said before with expanding/contracting spacetime, etc.

Also, I wouldn't think we'd have to explain the issue with a rotating reference frame

[Steel]

5 minutes ago, KerikBalm said:

In this example, the distance between said objects does not change at all. If they have relative velocity such that their distance is changing... it becomes rather hard without "funny stuff" like I said before with expanding/contracting spacetime, etc.

Also, I wouldn't think we'd have to explain the issue with a rotating reference frame

Don't take the example too seriously, its just an aid to the imagination. As K^2 has said a few times, using general relativity you can generalise the principle of the this example to any motion (the "funny" stuff you mentioned is quite a key part of this)

[problemecium]

As the OP is currently worded ("it is standing completely still in space", with no references to relative velocities), this situation is more or less meaningless.

Human understanding of the laws of physics generally favors small objects moving around bigger ones rather than the other way around. So Earth orbits the Sun because the Sun is massive and Earth is less so. A reference frame could of course be constructed in which Earth is stationary and the Sun orbits it in a complicated fashion, but even if the mathematics all hold up, this goes against human intuition about "still."
So we say "everything is moving at high velocity" because we find that galaxies move rapidly relative to distant galaxies, and we prefer the reference frame in which the heaviest objects move the slowest - effectively, the reference frame with a total velocity of zero - and we dub this "the universe" in our minds. So an object that's standing "still" is any object whose velocity relative to all other objects averages out to zero, so relative to the sum of all objects is is still. Such an object would be pretty ordinary. Relative to some objects it would appear to move very fast (because relative to "still" they themselves are moving fast), while relative to others it would move slowly. It wouldn't experience any abnormal relativistic effects or forces.
The problem is that the sum total of all known objects in the universe does not equate in physicists' terms to "the universe." The equivalence principle dictates that space itself does not have a special reference frame, so as mentioned above, any object could claim to be "still," or conversely any object could claim to be zipping through space at high speed. So the objects in the universe might all happen to be rushing in one direction very quickly, and thus your stationary object would, from their perspectives, be moving very quickly. Until some object is found that we decide to count as the "real" center of the universe, we are unable to prove whether or not your stationary object is moving, so people's claims that the object is moving in a certain direction are equivalent in validity to others' claims that it is everything else that is moving.

Long story short all you've really described is an object that doesn't believe it is moving, but that doesn't make it special in any way.

[K^2]

13 hours ago, KerikBalm said:

In this example, the distance between said objects does not change at all. If they have relative velocity such that their distance is changing... it becomes rather hard without "funny stuff" like I said before with expanding/contracting spacetime, etc.

Also, I wouldn't think we'd have to explain the issue with a rotating reference frame

Actually, you do have to explain the issue with the rotating frame. The only "issue" I can think of is that it's non-inertial. Well, guess what? There is no such thing as inertial frame of reference in the real world. Thanks to gravity, we don't have flat space-time. No flat space-time, no inertial frame of reference. Which makes rotating frame of reference as good as any other.

And once we extend this properly, with an arbitrary choice of a metric that matches the actual curvature of space time, we can assign to every point in space any velocity we like. Even to the point that, yes, two objects moving with respect to each other will be both at rest with respect to a third object.

This is the reality of relative velocities. I know it's hard to accept, because you spend your entire life picturing all space as Eucledian, where naive notions of relativity work. But it's not. And relative velocities are a slightly more complciated concept than that. Not only do actual velocities of objects are a matter of coordinate system choice, but also the relative velocity between any set of objects is a matter of coordinate system choice. That's just how universe works.

[A35K]

The problem is that space itself is expanding, (it even stretches electromagnetic waves, CMBR), so for something to not be moving at all, shouldn't it be in the exact center of the universe?

[K^2]

36 minutes ago, A35K said:

The problem is that space itself is expanding, (it even stretches electromagnetic waves, CMBR), so for something to not be moving at all, shouldn't it be in the exact center of the universe?

The way space expands, every single point is at the center of the universe. It's more of an inflation, with space itself stretching, than "stuff flying apart."

[Guest]

Considering that gravity of literally everything acts on this object, it's likely impossible.  If you want to get on a molecular level, you'd need to go to absolute zero, which scientists have gotten close to, but have had no luck actually achieving it.  Basically, you'd need it to be the only thing in the universe, cooled at absolute zero.  That's also if you don't factor in the fact that velocity is ONLY relative.  For all we know, everything's falling, but all at the same rate, making it seem like zero velocity.  If you are completely still on Earth, you are going really fast when looked at from the perspective of the sun.  This means that this object could be moving, but there is no way to measure it.  

1 hour ago, K^2 said:

The way space expands, every single point is at the center of the universe. It's more of an inflation, with space itself stretching, than "stuff flying apart."

Somewhat true.  Take a room, and put chairs in it spread evenly apart and always a fixed distance from the edge.  Now make that room bigger.  The chairs will be spread evenly apart, and will still be that distance from the edge, but they are now much further apart.

Edited January 14, 2016 by Guest

[K^2]

28 minutes ago, CliftonM said:

Somewhat true.  Take a room, and put chairs in it spread evenly apart and always a fixed distance from the edge.  Now make that room bigger.  The chairs will be spread evenly apart, and will still be that distance from the edge, but they are now much further apart.

Except, there is no edge, and all of the room and chairs used to be a single point. Which makes the analogy somewhat weak.

[Slam_Jones]

In my mind, it works like this:  velocity is a relation between two objects.  Therefore velocity is always relative.  Relative to my chair, I am not moving.  Relative to the sun, I am flying around at high speed.  Relative to the center of the galaxy, I am moving even faster.

So (again, in my mind, at least) your question needs another part: zero velocity in relation to what?  The nearest celestial object?  A specific orbit?  A distant, but relevant, object?

Edited January 14, 2016 by Slam_Jones

[Guest]

58 minutes ago, K^2 said:

Except, there is no edge, and all of the room and chairs used to be a single point. Which makes the analogy somewhat weak.

Correct, but the intent of it is to show that things move with expansion.  It's really just putting it into an easy to understand form.  What I really should have said was that they are always in the same place in the room when you factor in scale.  It's kind of hard to explain rather than to just understand, so that one is also a good deal wrong as well. 

[K^2]

19 minutes ago, Slam_Jones said:

In my mind, it works like this:  velocity is a relation between two objects.  Therefore velocity is always relative.

For the n-th time, no, it's more complicated than that. This kind of logic only works in space-time that is flat everywhere. Once you have objects with mass distorting space-time, this simplistic view doesn't work anymore. Relative velocity between two objects is still a matter of frame of reference.

[problemecium]

^ That's a tougher order than you might imagine. The current claim of most of the astrophysics community is that since the universe arose from a single point, all points in space can trace the expansion of the universe back to a point at their own location, and therefore the "Singularity" is wherever you are, wherever you happen to be in the universe.

Of course in my book that begs a further question. That analogy only holds up in a spherical universe. In a flat universe, a hypothetical adventurer should be able to find a point beyond which there are no stars or galaxies. And if a bunch of such people were to share data, they could triangulate the exact center.
Either that, or the universe is infinite, in which case one of the following must be true:
- It is infinitely old
- It was always infinitely large
- For some non-zero length of time in its past, it must have been expanding infinitely fast

To answer llanthas's question in particular, if such a hypothetical point did exist, refer to my previous post. The object would have a velocity of exactly zero on average when measured relative to all objects in the universe, but relative to any particular (moving) object, it would appear to move just like any ordinary object. If there is a "true" center of the universe, it'll still be hard to find because that point wouldn't appear special in any obvious way.

[Rdivine]

On 1/12/2016 at 4:52 AM, Chakat Firepaw said:

The question is meaningless given our current knowledge of physics.  There is no such thing as "standing completely still in space," as that would require there to be a single base reference frame for the entire universe.

Now, if you were to take some inertial reference frame and propose a stationary object in that frame, (perhaps it's being pushed by some extra-universal force), you have something meaningful but not particularly interesting:  You have a mass at the one point that generates gravity and makes a few equations relating to it a bit easier to solve.

Now, since inertia of an object increases exponentially with speed, there could be a method to calculate its acceleration with a constant force, and use it to determine its lowest possible intertia, hence determining its absolute velocity relative to the fabric of spacetime itself?

Then we can achieve absolutely no velocity at all.

[Chakat Firepaw]

On 16/01/2016 at 10:13 PM, Rdivine said:

Now, since inertia of an object increases exponentially with speed, there could be a method to calculate its acceleration with a constant force, and use it to determine its lowest possible intertia, hence determining its absolute velocity relative to the fabric of spacetime itself?

Then we can achieve absolutely no velocity at all.

Nope, all that would do is determine the frame of reference where its velocity is 0.  This frame always exists and is much easier to determine.