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What can be defined as being motionless?

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Jenny
1035418.  Thu Nov 14, 2013 6:29 pm Reply with quote

djgordy wrote:
I used that argument to get out of a speeding ticket. So they gave me a parking ticket instead.


Funny!

 
Posital
1035420.  Thu Nov 14, 2013 6:38 pm Reply with quote

+1 n1 djg

On the OP: Errm - everything is motionless with respect to itself...

 
Posital
1035421.  Thu Nov 14, 2013 6:41 pm Reply with quote

dr.bob wrote:
Einstein's theory of relativity shows that all motion is relative to another object.

You don't need Einstein's Relativity to show that all motion is relative.

 
gruff5
1035518.  Fri Nov 15, 2013 7:39 am Reply with quote

Posital wrote:
You don't need Einstein's Relativity to show that all motion is relative.

Yep, think it was some chap called Galileo who originally came up with the concept of relativity. Bright lad. Though I think you do need the constancy of the speed of light (and Einstein's Special Relativity theory) to give solid evidence for the idea. Einstein, after General Relativity had brought in curved space-time, came back to the idea of the ether with a more favourable view.

What I don't understand is how the "quantum foam" of virtual particles popping in & out of existence doesn't provide a reference frame. But apparently, as an object moves, it sees its own quantum foam moving along with it. But I don't understand this. Presumably such a concept would unite Einstein's relativity and quantum theory - but I thought they hadn't done that yet?

 
dr.bob
1035555.  Fri Nov 15, 2013 9:21 am Reply with quote

gruff5 wrote:
Posital wrote:
You don't need Einstein's Relativity to show that all motion is relative.

Yep, think it was some chap called Galileo who originally came up with the concept of relativity. Bright lad. Though I think you do need the constancy of the speed of light (and Einstein's Special Relativity theory) to give solid evidence for the idea.


Quite so. Galileo showed that motion was relative. Einstein showed that all motion is relative.

 
Posital
1035639.  Fri Nov 15, 2013 3:03 pm Reply with quote

Isn't it obvious that motion is relative without needing to refer to great minds?

If you run towards a pig - you're going to catch it quicker if it's walking away than if it's running away.

I think I can extended this theory to include all the animals from the Lion King - and hopefully this can even include planets and other stuff at a pinch.

There - proof that motion is relative without constant light speed or special relativity.

But I'm not expecting a Nobel prize any time soon.

 
gruff5
1035862.  Sun Nov 17, 2013 7:14 am Reply with quote

Posital wrote:
Isn't it obvious that motion is relative without needing to refer to great minds?

Well, as Dr Bob pointed out, the notion that all motion is relative is the bit that needs great minds to prove. And Einstein didn't so much prove that a universal reference frame, such as the ether, didn't exist, but that it was unnecessary.

It can be almost impossible to prove that something doesn't exist - ref. the 'does God exist' debate!. By Occam's Razor, the ether was done away with, but Occam's razor is not infallible - our Universe being the ultimate example of this: "Why is there something, rather than nothing?"

Another great mind, Isaac Newton, tended more to the idea that space was a stage or background upon which events took place - ie he was more of a non-relativist. His notion, known as "Newton's Bucket" demonstrates that there is absolute rotational motion, seemingly relative to no other object. This is not properly explained by relativity theory, only some vague appeal to "it must be to do with the distant stars". IF so, how?

 
Posital
1035870.  Sun Nov 17, 2013 7:58 am Reply with quote

I'm not sure why you're highlighting the word all, but anyway. Perhaps I missed one of the animals in the Lion King?

Ok - you're saying people believed in a universal frame of reference - which no-one has proved to exist (or is unnecessary). And this could lead to people believing in absolute speeds (or motionlessness).

But Einstein only showed you get interesting effects when you consider different frames of reference. And Newton was persuing a universal frame of reference - but still motion would be relative.

People had already understood these relative frames of reference existed before any of these boffins even got out of bed.

 
gruff5
1035891.  Sun Nov 17, 2013 9:43 am Reply with quote

Posital wrote:
I'm not sure why you're highlighting the word all, but anyway. Perhaps I missed one of the animals in the Lion King?

In your example, if you and the pig are both running at the same speed, then you are effectively both motionless. It is only relative to something else (eg the ground) that the two of you can be said to be moving. This was a new concept (relativity), introduced by Galileo. He used the example of the inside of a smoothly sailing ship within which objects could be thrown about with all their ballistics as if the ship was stationary and there being no way to decide how fast the ship was moving. This was a new concept that probably a non-seafaring nation would not have come up with. Einstein used the high-speed transport of his day - railway trains - in place of ships.

Posital wrote:
And Newton was persuing a universal frame of reference - but still motion would be relative.

Practical measurements of motion would be referenced to something - eg the ground, or the "fixed stars". But Newton still showed indications that he conceived of an absolute space and an absolute time that provided the backdrop to events.

What are your thoughts about "Newton's Bucket"? I find it quite intriguing ...

 
Posital
1035974.  Sun Nov 17, 2013 4:47 pm Reply with quote

Now - Newtons Bucket.

This experiment draws on things outside my experience of the Lion King - and I may have to revisit Madagascar 3 and the wall of death to understand this phenomenon.

Why is it that bikers can stay on the stationary wall of death when travelling at speed, but if you make the wall rotate and the bikes stationary (relative to the earth(?)) then it doesn't work?

Tricky - I'll have to think about it.

 
dr.bob
1036011.  Mon Nov 18, 2013 5:29 am Reply with quote

Posital wrote:
People had already understood these relative frames of reference existed before any of these boffins even got out of bed.


Everyone understood about relative frames of reference, but everyone assumed that there was some absolute frame of reference to which all motion could be compared. What Einstein showed was that there is no absolute frame of reference at all.

In your example of someone chasing a pig, everyone would've understood the idea of the relative motions of the person and the pig, but they would've taken as obvious that both of their movements could be measured absolutely with respect to the ground beneath them.

What Einstein showed was that there was no physical way that you could tell whether you and the pig were moving relative to a stationary ground, or if the pig was entirely motionless and you and the ground were moving. That was the bit that took the big brains and still causes a lot of people considerable confusion.

 
gruff5
1036035.  Mon Nov 18, 2013 8:00 am Reply with quote

Posital wrote:
Now - Newtons Bucket... Why is it that bikers can stay on the stationary wall of death when travelling at speed, but if you make the wall rotate and the bikes stationary (relative to the earth(?)) then it doesn't work?

Tricky - I'll have to think about it.

Hah! I like your mental demonstration :-)

Perhaps it's to do with the Higgs field? The Higgs field (so we're told) gives particles mass by acting it bit like treacle or a crowd of fans (the Higgs bosons) thru which a celebrity (the particle) is trying to pass.

Perhaps the Higgs field has directional properties? So that the if the particle spins, there is an inertia & centripetal effect associated with that spinning - courtesy of interaction with the Higgs field.

If this were the case, then space does have an absolute directional frame of reference. This would be fixed relative to the orientation of the CMB and the Hubble Flow.

 
pagetheoracle
1092588.  Wed Sep 03, 2014 6:58 am Reply with quote

Posital gravity comes into this. If the wall is stationary, it already connected to the ground but the bike isn't. Forward momentum negates gravity in this instance.

Everything is in motion from atoms to planets but as you so rightly said it doesn't appear so to you as observer. In a recent documentary about the building of the Forth Road Bridge somebody else came up with this point too, that when on the bridge it didn't seem in motion but to observers on the ground it was swaying.

Now if you'll excuse me I feel a headache coming on, it's all that motion causing e-motion in me

 
pagetheoracle
1093058.  Sat Sep 06, 2014 10:17 am Reply with quote

I've got another definition of being motionless - the mind of a fundamentalist: It doesn't go forward but is constantly stuck in the past, so no movement is possible in its life.

 
gruff5
1094269.  Tue Sep 16, 2014 7:03 am Reply with quote

IS seem to want to shake up the Middle East in a big way, even if it is back to the future.

 

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