Speed and Mass

[ccwebb]

I have come across a few different posts and threads that are referring to mass and speed. Specifically, that the faster something goes, the more massive it becomes.

 

Am I just confusing a topic here and this is completely wrong, or that statement true? If it is true, then how is it possible? As a plane flies it gets lighter (less massive) as it flies do to fuel burn. This is why airliners rarely fly level, more a parabola. The lighter they are the less lift (and thus drag) is needed.

 

But if speed increases mass, then the mass loss with fuel burn doesn't matter. Then why do.... well, you seem my catch 22?

 

Is mass and speed directly related somehow?

[EdEarl]

That faster things are more massive is predicted by the theory of relativity. Airplanes travel too slow for this effect to be noticed.

[swansont]

That faster things are more massive is predicted by the theory of relativity.

 

Actually, no. Mass increase is predicted by applying an equation of relativity to a situation that is contrary to one of the assumptions of that equation. When Einstein derived E=mc^2 ("Does the Inertia of a Body Depend upon its Energy-Content?"), the assumption was that the object was at rest. The energy measured by an observer in a moving frame would be the mass energy added to the kinetic energy. No mention of mass increasing.

 

In the formalism of relativity that has arisen since, mass refers to the rest mass or invariant mass when looking at energy in different frames of reference. [math]E^2=p^2c^2 + m^2c^4[/math]

 

The notion that mass changes is an independent application of E=mc^2 that introduces yet another kind of mass, which was not an original part of relativity.

[EdEarl]

ty swansont

 

Is it accurate to say an airplane does not go fast enough for the effect to be significant compared to the rest airplane mass.

Edited May 27, 2013 by EdEarl

[swansont]

ty swansont

 

Is it accurate to say an airplane does not go fast enough for the effect to be significant compared to the rest airplane mass.

 

The "effect" is having 1/2mv^2 not accurately describe the kinetic energy, and you are correct that an airplane will not move fast enough for this to be noticeable. (The effect on atomic clock frequencies is somewhere around a part in 10^12, and need to be integrated for at least several hours to be able to measure a result. We can measure that more precisely than we can mass)

[ccwebb]

I have seen, and conducted, the time experiment myself while flying. (and it can not be measured with a wrist watch!)

That makes sense about not being fast enough to notice the effect of increased mass, thus leaving the decreased fuel being the 'bigger' variable.

 

Now this increased mass, who would notice it? If a person began accelerating to the point were increased mass can be measured, would this increase mass be applied to the person moving or perceived by the person standing still?

[EdEarl]

"noticed"...just trying to keep it simple for the OP. Changed to "effect to be significant compared to the rest airplane mass" for swansont. I am not an expert, obviously, but not uneducated either. I hope we do not overwhelm the OP with nuance. I would prefer starting another thread for my education.

[Ron Bert]

Physical Mass and Relational Speed are related only in a system where both are valid considerations. In the case of our tangible universe, one would be hard pressed to isolate one from the other making them always directly related to that of the observer. However, multiple answers exist depending upon various considerations and indirect viewpoints. Simple questions at times are the most complex. It has always been a challenge to see things outside of the box, truthfully. We can say, I believe with certainty, that the present connects us to the observable. So, does this always mean mass and relational speed correspond with inflation? Ponder on. Take, for example, any rest mass or inert substance under consideration, the penny in your hand for example. Location, location, location. This is what gives us one answer over another, the frame reference that we decide to use; here or there? There are so many considerations to your fundamental question that most if not all still scratch heads over the basic principles involving space, time, speed, energy, substance, parabolic or hyperbolic relations, etc.

 

My dear friend, books have been and are yet to be written concerning your simple inquiry. As for the penny, at rest mass for you, seemingly without velocity, is our illusion. My vague memory tells me that we propel about the Sun at some odd 65,000 miles per hour and in relation to the galactic core, perhaps 500,000 miles per hour. Still, these are yet relatively low speeds in relation to what the Red Shift indicates with a universal universe edge approaching the speed of light in all directions. So, if I looked back from that distant edge of our universe to the penny in your hand, its mass would appear unchanged, yet traveling at the fantastic speed of near light speed. You see how mass and speed need that third element of location to make precise judgments. I might add in fact, that a fundamental premise for the way absolute time works is that all mass falls forward at the speed of light causing all mass to be in a state of inflation which we do observe (If it were The Big Crunch, we would observe deflation which has not been observed). For the tangible, all things are in motion. Time stops for no man. It is in different relative present speeds, in space, that calculates various openings out, or in, perspective wise. My high school teacher once told me that if mass opened to the speed of light, that it would timelessly and instantly expand to the size of the universe. Seeds from the past. This link may help you - http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html . Good luck in your continued thinking!

Edited May 27, 2013 by Ron Bert

[swansont]

ccwebb, on 27 May 2013 - 16:06, said:

I have seen, and conducted, the time experiment myself while flying. (and it can not be measured with a wrist watch!)

You can with this kind of wrist watch.

 

http://leapsecond.com/pages/atomic-bill/

[ccwebb]

Ron- thank you. Your answer actually does make things a bit clearer for my simple mind.

 

 

Swansot... that watch is just a bit bigger than my Citizen, Eco-drive, Blue Angels edition! lol

[Enthalpy]

 

 

[...] The energy measured by an observer in a moving frame would be the mass energy added to the kinetic energy. No mention of mass increasing.

 

In the formalism of relativity that has arisen since, mass refers to the rest mass or invariant mass [...]

 

The notion that mass changes [...] introduces yet another kind of mass, which was not an original part of relativity.

 

Maybe it's just a matter of wording. How shall we call that mass that increases with speed? Since it is the one mass that limits accelerations and creates gravity, I was pleased with the short expression "mass" for that one, or if really necessary "relativistic mass", and "rest mass" for the constant one.

 

There is a little bit more in it. We can't distinguish rest mass from kinetic and interaction energies, in some objects whose interior is imprecisely known. It is said to be the case for protons and neutrons, whose mass shall result essentially from movement and interactions between quarks and gluons. But when considering a complete proton, we say "mass" and even "rest mass" for it, despite its constituents are very far from rest. We can't do better, and don't need to because it makes no difference, despite said "rest mass" is essentially non-rest.

 

So a distinction between rest mass and energy seems artificial to me, as both have the same effects, and in some cases we can't attribute them to one rather than the other. I'd prefer "mass" or "mass-energy" for the sum of both, which is the observable quantity. Or?

[swansont]

Enthalpy, on 28 May 2013 - 18:30, said:

Maybe it's just a matter of wording. How shall we call that mass that increases with speed? Since it is the one mass that limits accelerations and creates gravity, I was pleased with the short expression "mass" for that one, or if really necessary "relativistic mass", and "rest mass" for the constant one.

We can call it the abomination, or the conceptually misleading mass, or, as you point out, the relativistic mass. Or just use the total energy, since it's just a proxy for that. But it's still an add-on to relativity, conjured by taking an equation and misapplying it. The danger is that the errors you get in using it are not readily apparent. But the mass terms in almost any equation you might use in relativity will not be relativistic mass, so you will end up making those errors.

Enthalpy, on 28 May 2013 - 18:30, said:

There is a little bit more in it. We can't distinguish rest mass from kinetic and interaction energies, in some objects whose interior is imprecisely known. It is said to be the case for protons and neutrons, whose mass shall result essentially from movement and interactions between quarks and gluons. But when considering a complete proton, we say "mass" and even "rest mass" for it, despite its constituents are very far from rest. We can't do better, and don't need to because it makes no difference, despite said "rest mass" is essentially non-rest.

 

So a distinction between rest mass and energy seems artificial to me, as both have the same effects, and in some cases we can't attribute them to one rather than the other. I'd prefer "mass" or "mass-energy" for the sum of both, which is the observable quantity. Or?

Rest mass refers to the center-of-mass motion being zero. The equation was derived in terms of kinematics, and the same conventions apply.

 

"mass-energy for the sum of both" belies a conceptual error. There is no sum with relativistic mass: mass and total energy are identically the same.

[Enthalpy]

Rest mass refers to the center-of-mass motion being zero.

That sounds good. The center-of-mass can be known even when the internal details of an object are unknown, and even if ignoring the internal speeds, interactions, kinetic energies... (at a proton for instance), the composite particle gets a rest mass and a center-of-mass that summarize the sub-particles and energies. Thanks!

 

Fun: as interaction energy has inertia (said to be the main contribution in a proton), we would need to know where the interaction energy resides in order to compute a center-of-mass.