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What can be defined as being motionless?

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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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