Re: How do we know antimatter has POSITIVE mass?
- From: "Androcles" <Headmaster@xxxxxxxxxxxxxxxx>
- Date: Sat, 01 Mar 2008 09:28:21 GMT
<solletica@xxxxxxxxx> wrote in message
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On Feb 29, 7:01 pm, "Androcles" <Headmas...@xxxxxxxxxxxxxxxx> wrote:
<sollet...@xxxxxxxxx> wrote in message
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| This is layman's question. I'm NOT a physicist so be patient with
| me :)
|
| Experimental evidence--the annihilation of matter w/antimatter, and
| QFT both suggest that like matter, antimatter has positive energy.
|
| So, based on that, one can conclude that antimatter must also have
| positive mass, since an antimatter particle's mass = E/c^2 and E is
| always positive.
|
| However, doesn't this conclusion rest on the assumption that mass is
| simply defined to be energy in a contained (i. e. non massless boson)
| form?
|
| What if we define an object's mass M in the gravitational sense, i. e.
| as F*r^2/(G*M2), where M2 is another mass near M. In this way, an
| object is said to have negative mass if it has a repulsive rather than
| attractive gravitational force on other (smaller) masses.
|
| Of course, if Newton's and GR's predicitions for matter also apply to
| antimatter, then antimatter falls toward a larger positive mass
| object. But how particles of antimatter fall to Earth and the
| particle's INNATE gravitational field are two different things.
|
| In the Newton equation, acceleration due to a gravity of a negative
| mass object would still be downward (because a = F/m, and so if F is
| negative for a negative mass, a will be positive, since m is also
| negative).
|
| But if the BIG object had a negative mass, then the smaller object--
| regardless of whether it had positive or negative mass, would fall up,
| according to NEWTON's laws. GR would likely predict the same thing if
| mass were in fact defined as a quantity proportional to an object's
| gravitational field.
|
| From what I've read, no one has ever done an experiment with
| antimatter to accurately measure its acceleration due to gravity,
| although it seems it can be theoretically proven that smaller
| particles would fall down. However, there has also never been an
| experiment done with a BIG antimatter mass to assess its gravitational
| effect on smaller objects.
|
| So my big question is how do we know antimatter DOES not carry a
| negative (repulsive) gravitational field?
The big answer is: you don't. But you knew that anyway, so all
you are really doing is inviting opinion.
| As a matter of fact, I DID NOT know it for sure. That why I said I'm
| a layman :) But I appreciate the responses of the posters here,
| because now I know the answer--that it's unknown.
Nothing wrong with that. If we knew everything we'd be gods.
He who knows not and knows not that he knows not, he is a fool. Shun him.
He who knows not and knows that he knows not, he is a student. Teach him.
He who knows and knows not that he knows, he is a tool. Use him.
He who knows and knows that he knows, he is a sage. Follow him.
| However, if antimatter has an attractive gravitational force, like
| matter, then according to GR,
As a layman you are not capable of expounding upon GR, that
would require a mathematician.
| if empty space is filled with infinite
| matter and antimatter particles--as predicted by the Dirac equation--
| then empty space would be well, INFINITELY HEAVY, at least, according
| to my intuition.
In hypothetical sentences introduced by 'if' and referring to
past time, where conditions are to be deemed 'unfulfilled',
the verb will regularly be found in the pluperfect subjunctive,
in both protasis and apodosis.
-- Donet, "Principles of Elementary Latin Syntax"
You have 'if'^2 and no 'else'.
IF pigs could fly THEN they'd be pigeons ELSE they are bacon.
| I dunno if I'm seeing this right.
It's ok not to know.
| But I'm thinking of empty space as
| a giant net, and masses as balls placed on the net.
How nice for you. I think of empty space as being empty, which
is why I call it empty space and not filled space.
| When you place a
| ball on the net, it distorts the space around it,
Yesterday upon the stair
I saw a man who wasn't there.
He wasn't there again today,
oh how wish he'd go away.
| which represents
| gravitational distortion in space.
Wow, I wonder who came up with that crazy idea?
| But if you put infinite balls on
| the net, all with attractive G fields, then the net would just drop.
In hypothetical sentences introduced by 'if' and referring to
past time, where conditions are to be deemed 'unfulfilled',
the verb will regularly be found in the pluperfect subjunctive,
in both protasis and apodosis.
-- Donet, "Principles of Elementary Latin Syntax"
| Of course, the net would drop everywhere equally, making it flat.
Well, of course. BTW, have you had your medication today?
| But
| then how could you determine the presence of a particle in this net
| dropped to the floor?
Dropped? Floor?
Let me see if I have this right. You are using gravity as an analogy
for err... gravity, right?
| If you tried to represent the presence of a
| negative energy particle as a spot where the net was raised by an
| amount A, then the net wouldn't be raised at that spot because
| INFINITY-A = INFINITY.
In hypothetical sentences introduced by 'if' and referring to
past time, where conditions are to be deemed 'unfulfilled',
the verb will regularly be found in the pluperfect subjunctive,
in both protasis and apodosis.
-- Donet, "Principles of Elementary Latin Syntax"
(this is why I said I'm a layman! Trust me, I don't have any degree
in physics and much of what I read is solely based on my own
curiosity)
Of course you are a layman, you constantly start a sentence
with "if" and never provide an "else".
| Correct me if I'm wrong, but QFT reformulates the Dirac equation in a
| way that treats only localized bexcitations of the vacuum (whether the
| excitations represent matter or antimatter or photons) as the presence
| of particle(s), right?
Ok, wrong. I've corrected you as requested.
| And from the point of view of QFT, excitations
| represent positive energy densities, and where there are no
| excitations, there is nothing but the vacuum, correct?
From the point of view of mine, I'm not excited.
| So in QFT,
| there is no need for particles with a negative G field, it seems to
| me. Still, the QFT formulation seems to hide the negative energy states
| predicted by the Dirac equation.
Perhaps Dirac was a lunatic too.
| However, it seems to me (and I'm
| only a layman), that if
In hypothetical sentences introduced by 'if' and referring to
past time, where conditions are to be deemed 'unfulfilled',
the verb will regularly be found in the pluperfect subjunctive,
in both protasis and apodosis.
-- Donet, "Principles of Elementary Latin Syntax"
| you give antimatter a negative G field, then
| you can have this sea of negative energy as predicted by Dirac and
| nothing strange would happen to empty space because the positive
| gravity (matter) would push the net down and the negative gravity
| (antimatter) particles would compensate by pushing it up, keeping the
| net level and flat.
"Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!"
He took his vorpal sword in hand:
Long time the manxome foe he sought --
So rested he by the Tumtum tree,
And stood awhile in thought.
And, as in uffish thought he stood,
The Jabberwock, with eyes of flame,
Came whiffling through the tulgey wood,
And burbled as it came!
One, two! One, two! And through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back.
"And, has thou slain the Jabberwock?
Come to my arms, my beamish boy!
O frabjous day! Callooh! Callay!'
He chortled in his joy.
`Twas brillig, and the slithy toves
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgrabe.
.
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