B Can an object in every frame of reference have zero velocity?

[frankin garcia]

If I am sitting, not moving, my velocity can be zero along with my acceleration but in truth the Earth is moving along with the solar system and so on but i want to know theoretically if a massless object in space can have zero velocity and zero acceleration, in essence what i am askimg is can something, have zero velocity/acceleration in every frame of reference possible? ( excuse me if this doesn't make sense I am only in high school and I am still tryimg to teach myself this stuff, so if this sounds stupid I am sorry lol)

 

[jedishrfu]

In whatever frame I'm in, I will observe objects that are either stationary with me or moving closer or farther away.

If I then start moving then other objects will become stationary with me but not necessarily the ones that I observed earlier unless they started moving when I started moving.

You could think of it as being in a bicycle race, some folks are moving at your speed and so appear stationary whereas everyone else is moving faster or slower. If you decide to race a bit faster then some of those racing past you will appear to now be stationary and everyone else is still moving faster or slower.

 

[HallsofIvy]

If your question is "can there be an object which has 0 speed in every reference frame", the answer is clearly "no". Suppose we have one frame in which the object has speed 0. Then there certainly exist another frame which has speed v\ne 0 with respect to the first frame and that same object will have speed -v in that frame.

 

[Orodruin]

First of all, there is no such thing as "having zero velocity" unless you specify relative to what you have zero velocity. This is true in classical mechanics as well as in relativity and is really not anything particular for SR. In order to understand SR, you first need to understand what things are conceptually new.

Second, a massless object can never be at rest relative to something else it will always move at the speed of light.

 

[the_emi_guy]

Expanding on other replies, relativity is all about motion in space-time, not motion in space alone. If you move 1 mile in space in one second, you may consider this to be "fast" but during that same second you have traveled 186,000 miles in space-time.

 

[HallsofIvy]

In my answer, above, I assumed that your question was "can there exist an object which has velocity 0 in every frame". The answer to that is, clearly, "no" because we can have frames that are in motion relative to each other. Say, frame A has velocity non-zero v relative to frame B. An object that has velocity 0 relative to Frame A also has velocity v relative to frame B.

However, it occurs to me that you might have meant "in every frame, can there exist an object that has velocity 0 in that frame" (perhaps different objects in different frames). The answer to that is just as clearly "yes".

 

[alw34]

If I am sitting, not moving, my velocity can be zero along with my acceleration

You have a number of different concepts hidden in your post. It takes a while to learn how to sort them out from one another. I'll tackle a few here:

The correct way to state this would be to posit " ..my velocity can be zero along with my acceleration with respect to the room I'm in", for example, if that is what you were thinking...or "the class room I'm in". That provides your reference frame.

But even reference frames are tricky at first: Usually they are discussed as either inertial, meaning moving at a constant velocity, or 'non inertial', meaning accelerating. A 'room' is not such a simple reference as you might think.

When you are seated, what do you feel? a 'force' pushing against your backside, right? That is, the seat is pushing against you. That means you are actually accelerating! So even though you may not be moving with respect to your local reference frame [whatever room you are in] you are actually accelerating.

So sitting in a room, not only are you moving with a velocity as you understood, you are also accelerating which may be different that you assumed.

if a massless object in space can have zero velocity and zero acceleration

Post #8 answered that:

Second, a massless object can never be at rest relative to something else it will always move at the speed of light.

What is interesting is that when a massless object is emitted [created], say a photon [a 'particle' of light' emitted from an atom, as far as is known it appears at light speed and stays at light speed until it is absorbed somewhere else.

 

[PeterDonis]

So sitting in a room, not only are you moving with a velocity as you understood

As others have already pointed out, "moving with a velocity" is meaningless unless you specify relative to what. You are not moving at all relative to the room. The room is a non-inertial frame, as you point out, but that doesn't make it invalid as a reference relative to which velocity can be defined.

This also means that you can have zero velocity even though you are accelerating in the sense you have defined "accelerating"; that's because the sense of "accelerating" that you are using, i.e., that you can feel a force pushing on you, does not imply anything about the derivative of your velocity with respect to time. For clarity, the term "proper acceleration" is often used to refer to feeling a force, and the term "coordinate acceleration" is used to refer to the derivative of your velocity with respect to time.

 

[alw34]

As others have already pointed out, "moving with a velocity" is meaningless unless you specify relative to what. You are not moving at all relative to the room.

frankin, in case my post was not clear I was referring to your original post:

but in truth the Earth is moving along with the solar system

where you used a reference frame of sorts.

So even though it superficially seems you are 'sitting still in a room' you seemed to understand with respect to some other frame of reference, say the sun in our solar system, you are actually moving. And of course the sun is moving within our galaxy and so forth.

For clarity, the term "proper acceleration" is often used to refer to feeling a force, and the term "coordinate acceleration" is used to refer to the derivative of your velocity with respect to time.

I found the idea of "proper acceleration" very powerful because it is easy to relate to our everday experience when starting out trying to understand relativity. Other parts of relativity are NOT normally experienced at our everyday slow speeds.

There is a nice introduction of some terms here:

https://en.wikipedia.org/wiki/Proper_acceleration

Frankin, if you are interested, consider exploring each term in a source of your choice. Wikipedia is great on some and rather obscure on others.

Here's a nice example of proper acceleration:

"In an accelerating rocket after launch, or even in a rocket standing at the gantry, the proper acceleration is the acceleration felt by the occupants..."

Here is a good source I found recommended in these forums: http://mathpages.com/rr/rrtoc.htm [Reflections on Relativity]

And you have probably experienced a similar series of accelerations sitting sit in a car, where you feel a 'force' while seated without the vehicle moving along the road, then an additional 'force' as the car accelerates up to highway speed. And there is another acceleration you 'feel' as the car rounds a curve in the road.

If you have studied derivatives in math, many here can assist you in further understanding.

 

[Orodruin]

I found the idea of "proper acceleration" very powerful because it is easy to relate to our everday experience when starting out trying to understand relativity.

Well, perhaps because it is not a relativistic concept?

 

[frankin garcia]

These are all great but yet you fail to depict if and how an object can exist without speed. My question is still unanswered it feels.

 

[Nugatory]

These are all great but yet you fail to depict if and how an object can exist without speed. My question is still unanswered it feels.

Back after more than three years, I see... Welcome back!

Whenever you’re talking about the speed of something, it is always relative to something else. I’m sitting in my chair right now; my speed relative to the chair is zero so that’s my speed if I consider the chair to be at rest. However, the chair is actually a seat in a jetliner flying over the surface of the Earth at 800 km/hr so my speed relative to the surface of the Earth is 800 km/hr; so that’s my speed if I consider the surface of the Earth to be at rest. Because of the earth’s rotation and orbital motion around the sun, my speed relative to the sun is something different, and my speed relative the center of the galaxy is yet something else. The point here is that what you choose to call “the speed” of any object is pretty much arbitrary - you can make it make it come out to be anything you want just by choosing what you consider to be at rest.

So it’s easy for an object to exist without speed - just choose to define speeds relative to that object and it will have speed zero.

 

[Ibix]

i want to know theoretically if a massless object in space can have zero velocity and zero acceleration,

A massless object can only travel at the speed of light. I suspect you actually meant "weightless", in which case the answer is as several people have pointed out - velocity is always measured relative to something else (the local surface of the Earth, in everyday life) so it can have any value you like.

can something, have zero velocity/acceleration in every frame of reference possible?

For any object with non-zero mass there exists a family of frames in which it is at rest. In all others, it will have non-zero velocity.

Acceleration is a different story. For a start, you might mean either coordinate acceleration or proper acceleration. The former depends on your choice of (possibly non-inertial) frame, and is frame-dependent. The latter is what you would measure locally with an accelerometer (like feeling heavier or lighter in an accelerating lift). This is an invariant quantity and all frames will agree - so if this is zero in one frame it will be zero in all.

My question is still unanswered it feels.

In that case, ask it in a different way. We can only read what you've written, and if we aren't understanding what you've written in the way you want us to, write something different.

 

[frankin garcia]

Your replys are satisfactory, most definitely, my soul is that much more at ease, i was like 16 when i posted this, sooo excuse the parameters of that question. I have read and learn a lot on qm and gr/sr, altho only on its concepts, thinly on its mathematics although i currently am reading einsteins papers, so fingers crossed.

 

[frankin garcia]

The essential purpose of that question tho was to try to reconcile how everyone could think massless objects move at light speed, i understand why, but how? Wouldnt ot be a more intuitive idea to leave the massless objects in a ubiquitous static state, where they are not moving insead simply filling the air waiting to show the possibilities it has, like a vehicle traveling in the dark, with its headlights, i would see the things the headlight is predicting/demonstrating to be happening, but the light itself i have never seen move, not even when the car is moving does that light move. Only the things around it appear to be moving. Einstein seemed to care about how science should be intuitive, i agree and when reading on quantum mechanics, it seemed very intuitive, as if i were being told this twice by my dad.

 

[frankin garcia]

Also how is velocity, acceleration or, to consume the concept of change in motion, speed, how is speed not something that directly affects the traits of a particular thing. If i move whether in empty space or not, there is a resistance to move from my mass or pressure, so when a particle's motion is messed with or created how is the speed determining what traits it may carry? or At This Point is speed only because of things or are things because of speed, do we need speed to literally create some of the fundamental entities, for lack of better word.

 

[Ibix]

i currently am reading einsteins papers, so fingers crossed.

This isn't a good idea if you aren't confident with the maths and physics of electrodynamics as it was understood in the early 20th century. Remember Einstein was writing to be read by people who are already experts, not beginners. A modern textbook will serve you much better, and then you can go and read Einstein's papers if you want.

how everyone could think massless objects move at light speed

In relativity, you cannot describe a massless object moving at anything other than the speed of light. That fact emerges from the maths - it's not something you have a choice in believing if you accept relativity's two postulates. And every experimental test we've ever done has validated relativity to the best precision we can manage, so you'd be foolish to disbelieve it.

I'm afraid the rest of that post makes no sense, and you should probably re-read PhysicsForums' policy on personal speculation.

Also how is velocity, acceleration or, to consume the concept of change in motion, speed, how is speed not something that directly affects the traits of a particular thing.

Acceleration and velocity are different things - you cannot lump them together and hope to understand anything.

If i move whether in empty space or not, there is a resistance to move from my mass or pressure,

This is not correct. Mass is often treated as a resistance to a change of motion (i.e., a resistance to acceleration), but it is most definitely not a resistance to motion. That would make no sense - we've known since Newton that things carry on moving in a straight line at constant speed unless acted on by a force.

so when a particle's motion is messed with or created how is the speed determining what traits it may carry? or At This Point is speed only because of things or are things because of speed, do we need speed to literally create some of the fundamental entities, for lack of better word.

Again, this makes no sense. I think you probably need a textbook on non-relativistic physics before you start on relativity.

 

[frankin garcia]

I understand the path I am leading, i am considering what needs to be in order for it to be true and effective.
But what your telling me is, you know for sure due to research, that velocity and acceleration have 0 chemical effect and are, instead, a measurement of something else going on? or does an object moving really cause chemical change, whether be it velocity or acceleration or any other form of Movement?

 

[frankin garcia]

I like to understand science strongly at its most basic elementary roots. I find it incredibly useful in my day to day life.

 

[Dale]

you know for sure due to research, that velocity and acceleration have 0 chemical effect

As surely as anything can be known, yes, we know for sure that velocity has no chemical effect. Acceleration could, depending on the arrangement, as acceleration can lead to pressure which can have chemical effects.

 

[frankin garcia]

I love this place a little bit,
In baseball you can either be smart about where the pitcher will be throwing the ball or you can feel it out, both can easily result in a homerun with the right technique. This same thinking can be applied to how much Ingredients can be used while cooking, how much support i should place in areas while doing construction, or even at figuring out how fast I am moving in a car without the speedometer. Why is it than that science seems to soley care for the technique of technical thinking, instead of these sort of premonitions humans and all living things have been born with the ability to utilize? I personally have seen both methods teach me scientific laws and theories and so much more, without having heard of them before. Others i know have experienced the same.

 

[Ibix]

But what your telling me is, you know for sure due to research, that velocity and acceleration have 0 chemical effect and are, instead, a measurement of something else going on?

Velocity is always defined relative to something else. I can change your velocity relative to me by standing up and walking around. How could that have an effect on you? The only way velocity could have an effect on something is if there is actually a global rest frame, and you may recall that relativity got started partly because of our inability to detect such a thing.

I believe that people do continue to search for violations of Lorentz covariance, and a detectable universal zero for velocity would be one such thing. Nothing found yet, though.

Acceleration is a different matter. As Dale has already mentioned, this may have effects on objects. Notably, a sense of having more or less weight in a lift. I doubt that's chemical, precisely, but certainly heavy acceleration could initiate chemical reactions - the obvious one being dropping a stick of dynamite.

Finally, I'll just observe that there are no absolute certainties about our theories. But we only accept theories if they reflect the real world as far as we can see, and we keep poking at the edges so they get improved or replaced. We've poked so much at the idea of velocity having an absolute sense that it's difficult to imagine how it could not be correct.

 

[Ibix]

Why is it than that science seems to soley care for the technique of technical thinking, instead of these sort of premonitions humans and all living things have been born with the ability to utilize?

Because "gut feel" is something you develop by experience. And the only people with experience of the kind of extreme situations where relativistic effects become detectable are the people who fire particles through accelerators, or view galaxies and black holes through telescopes, and those who study the results. They express their knowledge in mathematical terms because experience has taught us that that is what works for explaining this.

Anything else is just guesswork or hand-waving - which works fine for baseball. Not construction, though, not for anything complicated. If you can't produce detailed calculations showing that your building shouldn't have fallen down, you'll be the one that gets sued back into the stone age when it does.

 

[Vanadium 50]

Why is it than that science seems to soley care for the technique of technical thinking, instead of these sort of premonitions humans and all living things have been born with the ability to utilize?

Why does science require science to be science as opposed to an unupported pile of woo?

 

[Doc Al]

This is a good time to close this thread.