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- Thread starter Reflector
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Reflector said:

I don't know what you mean by "-ve velocity". Can you please clarify? Thanks.

Pete

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Okay. Say your moving near lightspeed. You go from speed A to speed B. Your mass increases by 5. Now say you have mass 5 and you are stationary. Now you go from speed B to speed A... '-ve velocity'. Get it? There is a connection between mass and velocity. So if you have mass you need to have '-ve velocity'....

Also '-ve velocity' corresponds to the direction/line connecting two masses by their centre of gravity. All other 'lines' all around the mass/es becomes positive, meaning positive velocity.

I bet you weren't expecting planets to have this so-called property of '-ve velocity'.....

Also '-ve velocity' corresponds to the direction/line connecting two masses by their centre of gravity. All other 'lines' all around the mass/es becomes positive, meaning positive velocity.

I bet you weren't expecting planets to have this so-called property of '-ve velocity'.....

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No. First you say that the massReflector said:Okay. Say your moving near lightspeed. You go from speed A to speed B. Your mass increases by 5. Now say you have mass 5 and you are stationary. Now you go from speed B to speed A... '-ve velocity'. Get it?

There is a connection betweenThere is a connection between mass and velocity.

Note: In most cases I use the term "mass" to mean "inertial mass" (aka "relativistic mass"). However please note that some people here have a strong tenancy to become confused when you leave the "inertial"/"relativistic" qualifier out.

Please define yout terms. What is "ve"? What is "-ve"? What is "-ve velocity"? Please define these terms precisely. Otherwise they mean nothing.So if you have mass you need to have '-ve velocity'....

Pete

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Alright, I was wrong... but it sounded cool. Gravity = negative velocity. I was just thinking the real laws of physics are based on really cool ideas and they are elusive to find.

I'll try to explain some more in case I am right. You increase in mass when you increase your velocity, meaning positive velocity. But then if you already have mass and you are at rest atleast relative to another mass, then how did you get that mass in terms of the same idea that mass increases by speed increasing? You didn't have speed to attain it. So you must pay for it by going from '0' velocity relative to another mass to something below zero, meaning you attain negative velocity. That's the only way you can pay for it, because if you get additional 'positive' velocity, your mass only increases. It doesn't explain the original rest mass. So therefore you have to have negative velocity.

But so how can 'negative velocity' not increase your mass? I don't think it ever can based on the construction of the Universe. You can't have two masses so far apart that their gravitation could cause them to increase in mass as they approach each other. Gravity is two weak, and there is not enough space to make them approach lightspeed....

I'll try to explain some more in case I am right. You increase in mass when you increase your velocity, meaning positive velocity. But then if you already have mass and you are at rest atleast relative to another mass, then how did you get that mass in terms of the same idea that mass increases by speed increasing? You didn't have speed to attain it. So you must pay for it by going from '0' velocity relative to another mass to something below zero, meaning you attain negative velocity. That's the only way you can pay for it, because if you get additional 'positive' velocity, your mass only increases. It doesn't explain the original rest mass. So therefore you have to have negative velocity.

But so how can 'negative velocity' not increase your mass? I don't think it ever can based on the construction of the Universe. You can't have two masses so far apart that their gravitation could cause them to increase in mass as they approach each other. Gravity is two weak, and there is not enough space to make them approach lightspeed....

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I've already explained to you that mass isReflector said:You increase in mass when you increase your velocity, meaning positive velocity.

You're incorrectly assuming that m(v = 0) = 0. That is incorrect. While it is true that mass is aBut then if you already have mass and you are at rest atleast relative to another mass, then how did you get that mass in terms of the same idea that mass increases by speed increasing?

[tex]m = \frac{m_{0}}{\sqrt{1-v^2/c^2}}[/tex]

Part of the mass, i.e. m

The term

Notice that when v = 0, m (v) = m(0) = m

Pete

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pmb_phy said:I've already explained to you that mass isnota function of velocity. It is a function ofspeedonly. Speed is defined as the magnitude of velocity.

You're incorrectly assuming that m(v = 0) = 0. That is incorrect. While it is true that mass is afunctionof speed it doesnotmean that when the speed is zero then so is the mass. the height of a person under the age of 15 is a function of time difference between the current day and the day that person was born. Call that time difference the person's "age." Therefore the child's height is a function of age. That doesn't mean that when the child was born that their height was zero. Mass is related to theproper massm_{0}(aka rest mass) as

[tex]m = \frac{m_{0}}{\sqrt{1-v^2/c^2}}[/tex]

Part of the mass, i.e. m_{0}, is an inherent property of a body and the rest is a result of relativity (which means that it is a result of time dilation and Lorentz contraction).

The termproperhere literally means "intrinsic".

Notice that when v = 0, m (v) = m(0) = m_{0}. And that is not zero.

Pete

You have already been proven wrong on all this in this forum. Why are you still spamming for Planck?

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Tom Mattson

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DW said:You have already been proven wrong on all this in this forum. Why are you still spamming for Planck?

What--exactly--is wrong with pmb's post? I know that he's not adhering to the preferred convention of defining mass as the norm of the 4-momentum. But that's all it is: a convention. Conventions aren't "proven wrong". They are simply adopted or rejected based on their usefulness or lack thereof.

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Tom Mattson

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I'm moving this to Theory Development. You have a lot of curiousity and are very imaginative, which is great, but the ideas you are posting are exaclty that: your ideas. They are not commensurate with relativity.

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Tom Mattson said:What--exactly--is wrong with pmb's post? I know that he's not adhering to the preferred convention of defining mass as the norm of the 4-momentum. But that's all it is: a convention. Conventions aren't "proven wrong". They are simply adopted or rejected based on their usefulness or lack thereof.

dw knows, as

Reflector - Since I don't know you all that well and don't know if you're familiar with this whole debate thing on the term

One case that comes to mind is a book a friend of mine just sent me to read during my convalescence. The author is the author of one of the most widely used GR texts that exists today and that is used to teach GR. The name of this new (Pub. 2003) is

(1) Nothing can travel faster than light.

(2) Light cannot be made to stand still.

(3) Clocks run slower when thery move.

(4) The length of an object contracts along the direction of its motion.

(5) There is no universal definitioin of time and simultaneity.

(6)

(7) Energy is equivalent to mass.

(8) Photons have zero rest mass.

(9) The Doppler redshift formula changes slightly.

Most of my relativity texts speak of mass in this way in some place or another in the text. And that includes texts published on or after 1994, of which there are 9. 3 of them use the concept throughoput the text. Some (Like Schutz's GR text) will say what I say, i.e. that inertial mass (aka relativistic mass) depends on speed while rest mass (an invariant) does not. The others don't use the concept at all, of which there are 4. I have 8 relativity texts published before 1994 and of them 2 do not use the mass = inertial mass (aka relativistic mass) definition.

For a complete discourse on the concept of mass in relativity please go to www.geocities.com/physics_world and click on the link labeled

Tom -

[tex] (m_{0}c)^2 = \bold g(\bold P, \bold P) = \bold P \bullet \bold P[/tex]

where

Pete

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