# Where's the beef? I mean the mass

• April 19th, 2012, 02:47 PM
icewendigo
Where's the beef? I mean the mass
So E=mc2

But what the heck is mass anyway and where does the mass come from? If my cup of coffee is transformed into pure energy will this energy have mass or be attracted by gravity?
• April 19th, 2012, 03:16 PM
TheObserver
There isn't really such a thing as pure energy. It has to come in some form, such as mass or kinetic energy. You can convert mass into kinetic energy and photons or other particles but you can't get just energy on its own, the energy has to be imparted into something. All energy exerts a gravitational influence so even if you could get "pure energy", so yes it would produce a gravitational attraction. Though Im not sure what it would mean for the energy itself to be attracted by gravity. Energy, whether its mass or not warps space as we currently understand it.

We do not yet understand the origin of mass, there are a number of open problems associated with it. My particular favourite problem is that the "charge" associated with gravity, provided you use the right units and proportionality constant, is exactly equal to inertial mass (the tendency to resist acceleration). You may have heard of the higgs mechanism for generating mass but the details of that are a bit too advanced for me right now, and I would imagine you as well. Either way the higgs mechanism is only a proposal and does not yet have any conclusive experimental evidence.
• April 19th, 2012, 04:26 PM
brody
From middle school Physical Science, I remember that "energy is the ability to work", work being the act of force exertion on an object in observable effect.

I'm not sure if this is to imply energy is just an abstract concept to describe the capacity to do something. Or is it actually tangible? Like ... energy you can physically contain and see (theoretically)? As in energy that actually "moves" from one object to another, like some tangible, yet invisible, force.
• April 20th, 2012, 02:04 AM
Markus Hanke
Quote:

Originally Posted by icewendigo
So E=mc2

But what the heck is mass anyway and where does the mass come from? If my cup of coffee is transformed into pure energy will this energy have mass or be attracted by gravity?

Think of mass as just another form of energy. So it is irrelevant whether, in your coffee cup example, you consider the mass m or the energy E; since both are equivalent descriptions of the same underlying reality, you get the same gravitational field.
• April 20th, 2012, 02:57 AM
Ghrasp
"the two are equivalent" is not the same as using ecquivalent words for what can be considered the same.

For equations "=" also means something as "both sides equivalent more then "the same".
A difference is that in an equation things both sides of it can be time-sultaneous.

For instance temperature and thermic energy of hot water in a pan the temperature is equivalant for the thermicenergy.
Such a formula doesn,t tell what can be done with that energy or what will happen to it. E=mC^2 then says that any objekt you see around you can be considered as energy correspondent to it,s mass. Analogue to thermic equations mass is more like the themperaturemeassurement for this energy.
Working formula,s around with unitanalysis parallel to working with the equations can sometimes help to get a better view.
Kg Ns^2/m can be notated then as Ns/(m/s) for instance.
Doing unitanalysis parallel, sometimes the two (equations and unitanalysis) connect and sometimes it shows paradoxes.
• April 20th, 2012, 03:33 AM
logic
Quote:

Originally Posted by Markus Hanke
Think of mass as just another form of energy. ...

They say mass is trapped energy. A photon, in certain conditions, splits into a +positron and an -electron. So EMR is pure energy (with charges) that can fly like an airplane with two wings (charges + and -) . If you split an airplane in two, longitudinally, the two half planes can't fly, they are stuck.
That is mass!

Is this correct?
If it is, I ask : how can the standard model guess the existence of mass with no charge? How can a particle like boson,neutrino etc be its own antiparticle?
How can they trasform into EMR, since the latter has charges ant they have not? What is the explanation they give?
Thanks
• April 20th, 2012, 03:51 AM
Strange
Quote:

Originally Posted by logic
They say mass is trapped energy.

If "they" say that, then they are using an analogy. (Who are "they"?)

Quote:

A photon, in certain conditions, splits into a +positron and an -electron.
The energy of a photon can, in certain conditions, be used to create a particle/anti-particle pair. These do not need to be an electron and positron, not do they need to be charged (as far as I know). This does not mean that the photon was made of these two particles.

Quote:

Is this correct?
Er... no.

Quote:

How can a particle like boson,neutrino etc be its own antiparticle?
Because there is more to an antiparticle than opposite charge. In the case of antineutrinos, for example, they have opposite chirality. However, it is also possible that neutrinos and antineutrinos are identical; not enough is known about them yet. (Look up Majorana fermions for more on this - I don't fully understand the subject.)

Quote:

How can they trasform into EMR, since the latter has charges ant they have not?
If by "the latter" you mean photons, then they don't have charge. But as long as the net charge is conserved, there is no problem.
• April 20th, 2012, 04:15 AM
Ghrasp
Mass as trapped energy is for this equation something as "temperature is trapped energy"
The basic equivalance is for weight and accelleration (combine f=ma and f=mg) weight is not the weightforce for this but F/M. In a restsituation for an objekt on a table f/m is 9,8/1 for 1 kg. 2 kg F/M= 19,6/2 is 2*9,8/ 2*1 = 9,8 or 2 * (9,8/1). Calculators can,t recognize this notation and calculate it to 2*9,8/1. The quivalance for an objekt lying in rest on a scale or table g is balanced out by F/M.
F is upward from the scale to an objekt so negative if g (g is down for a free fall) is considered positive (or reversed). Mg=-Ma the altitude stays the same because the two accellerations cancel each other out. In an elevator that accellerates upward Mg+Ma = M(g+a).
But from the equivalance Mg = -Ma. Not saying it,s true or classic but this is how I understand Einsteins toughts on this and how he interprets Newton somewhat differently then usual for coming to this equation combining f=ma and f=mg timesimultaneous.

Assume situation in rest g is 9,8 with an objekt of 1 kg lying on a table. E=1*C^2. (1=1 kg) Does this apply without asking for what it can be used for ? If not the equation would not apply.

Trapped energy simply revers to energy after a conversion from some use, need or want. E within the equation is not after a conversion because then the situation is no longer in rest and the mass can,t be meassured anymore. E would be potential energy then. Nothing wrong with that but potential energy is not trapped energy.
• April 23rd, 2012, 08:50 AM
icewendigo
Ive read somewhere that a particle accelerated to great speed has a greater mass? Why? Is the gravity of a black hole moving at a great speed greater than the gravity of a black hole that appears to be stationary?
• April 23rd, 2012, 09:07 AM
Strange
Quote:

Originally Posted by icewendigo
Ive read somewhere that a particle accelerated to great speed has a greater mass? Why?

It is because mass and energy are equivalent. As you accelerate a particle, you are giving it more kinetic energy. This is equivalent to adding mass. (Guitarist wrote a nice post recently giving the [relatively] simple derivation of E=mc2).

However, many people don't like this idea of "relativistic mass" as it can lead to confusion (as in the second half of your post). You can't directly measure the mass of the moving particle and all the effects you can measure can be explained in other ways.

Quote:

Is the gravity of a black hole moving at a great speed greater than the gravity of a black hole that appears to be stationary?
There is no simple answer to this.

First, note that this is a relative effect. So, although we may consider a moving particle/back hole/spaceship to have more mass, from the perspective of that object nothing has changed. So if the spaceship travels fast enough it will not turn into a black hole.

Secondly, to determine if the added "relativistic mass" increases the gravitational effect of the object requires the use of general relativity where the gravitational effect depends on rest mass, energy momentum, pressure, and other factors. I think the answer is that it has some effect but not as much as you might expect as some of the factors cancel out...
• April 24th, 2012, 01:13 AM
Markus Hanke
Quote:

Originally Posted by icewendigo
Ive read somewhere that a particle accelerated to great speed has a greater mass? Why? Is the gravity of a black hole moving at a great speed greater than the gravity of a black hole that appears to be stationary?

Such a system would be incredibly complex indeed. The short answer is yes, there would be some increase in gravity due to the momentum of the fast moving black hole. More importantly however, there would be a very pronounced "frame dragging" effect - just like a rotating black hole "drags" space-time around it, a very fast moving black hole would drag space-time behind it. Also, it would likely emit large amounts of gravitational radiation.
• April 24th, 2012, 01:20 AM
HexHammer
My unscientific theory:

- with a heavier core, the more "gravity particles" are "leftover" and can bind to gravity.
- gravity might be mistaken as only being recognized as gravity as it may consist of other forces.
• April 24th, 2012, 02:37 AM
MeteorWayne
Ya know, if it's unscientific, it's by definition, NOT a theory. At best it's a hypothesis, but even that requires a scientific foundation. The best description would be "my unscientific speculation".
• April 24th, 2012, 08:53 AM
HexHammer
Quote:

Originally Posted by MeteorWayne
Ya know, if it's unscientific, it's by definition, NOT a theory. At best it's a hypothesis, but even that requires a scientific foundation. The best description would be "my unscientific speculation".

You are indeed right, I struggle with the correct terms as:

1) english isn't my first language.

2) I have a good amount of dyslexia, I mix up terms and what not.

3) thanks for helping out with the definitions.
• April 24th, 2012, 10:00 AM
Janus
Quote:

Originally Posted by HexHammer
Quote:

Originally Posted by MeteorWayne
Ya know, if it's unscientific, it's by definition, NOT a theory. At best it's a hypothesis, but even that requires a scientific foundation. The best description would be "my unscientific speculation".

You are indeed right, I struggle with the correct terms as:

1) english isn't my first language.

2) I have a good amount of dyslexia, I mix up terms and what not.

3) thanks for helping out with the definitions.

Mod note: In addition, this is the "Physics" sub-forum. Personal theories and hypotheses belong in the "New Ideas and Hypotheses" sub-forum.