jackson@ttidcb.UUCP (Dick Jackson) (08/16/85)
There's a discussion on net.scifi-lovers relating to negative mass - the hope is to produce an FTL drive somehow. This triggered off a memory and I'm hoping someone can contribute. In about 1966 I attended a seminar by Prof. Fairbanks who researched at Stanford U (I think). He was trying to slow down positrons for long enough to tell if they fell upwards or downwards. Does anyone know how this turned out? If this experiment did not get completed, has there been any other work?
michaelm@bcsaic.UUCP (michael b maxwell) (08/21/85)
In article <437@ttidcb.UUCP> jackson@ttidcb.UUCP (Dick Jackson) writes: > >In about 1966 I attended a seminar by Prof. Fairbanks who researched >at Stanford U (I think). He was trying to slow down positrons for long >enough to tell if they fell upwards or downwards. > >Does anyone know how this turned out? If this experiment did not get >completed, has there been any other work? I read in the newspaper about a week ago that someone (Stanford??) was doing research on the mass of antimatter (not specifically positrons). The article stated that NASA was interested in this peripherally--they wanted to know whether antimatter could be contained, in the hopes that *it could be used as a fuel in spaceships*. Shades of Star Trek!! Can this really be? Or are the newspapers up to their often bad standard of journalism? :-) On a more morbid note, suppose antimatter could be contained, presumably in an electric field inside a vacuum bottle. Off hand, it seems that such an apparatus could be very small--perhaps briefcase sized. It wouldn't take very much antimatter to make a very powerful bomb. (Did I read that something like a gram of matter gets converted into energy in a nuclear bomb blast?) Let's hope that antimatter remains extremely difficult to produce. (Has more than a microgram ever been produced in all the world? I have no idea, but from what I hear even the largest accelerators produce only a few 100,000 antimatter particles?? At that rate, we're safe for a long time...) Of course, another problem with the idea of an antimatter terrorist bomb is that no vacuum bottle is perfect, and the antimatter would be a constant source of radiation as matter leaking in encountered the antimatter. Perhaps too much radiation to safely carry around? I hope so... Does anyone have a handle on the math of this? -- Mike Maxwell
tan@ihlpg.UUCP (Bill Tanenbaum) (08/22/85)
> There's a discussion on net.scifi-lovers relating to negative mass - > the hope is to produce an FTL drive somehow. This triggered off a > memory and I'm hoping someone can contribute. > > In about 1966 I attended a seminar by Prof. Fairbanks who researched > at Stanford U (I think). He was trying to slow down positrons for long > enough to tell if they fell upwards or downwards. > > Does anyone know how this turned out? If this experiment did not get > completed, has there been any other work? -------------------- The existence of negative mass (i. e. mass that falls up) would blow general relativity out of the water as it violates the equivalence principle. Also, the equivalence of gravitational and inertial mass has been shown experimentally to great accuracy (I can't remember the experimental error). I don't know whether anyone has directly experimentally determined that positrons fall down, but if they don't it would be a great shock to all physicists, expecially to the one doing the experiment. -- Bill Tanenbaum - AT&T Bell Labs - Naperville IL ihnp4!ihlpg!tan
dbb@aicchi.UUCP (Burch) (08/25/85)
> doing research on the mass of antimatter (not specifically > positrons). The article stated that NASA was interested in this > peripherally--they wanted to know whether antimatter could be contained, > in the hopes that *it could be used as a fuel in spaceships*. Shades of > Star Trek!! > > Can this really be? Or are the newspapers up to their often bad > standard of journalism? :-) > Well, In an unclassified paper by Robert L. Forward for DOD, he predicts that the production of anti-hydrogen snow could be a reality in a short period of time. He cites (incorrectly) the efficiency of the anti proton source at Fermilab as evidence that some level of economy can be reached. Really, if magnetic confinement fusion can be realised, it would be much cheaper, and very much less dangerous. A bomb, however, does not need to be cheap... -Ben Burch
sutin@astrovax.UUCP (Brian M. Sutin) (08/25/85)
> There's a discussion on net.scifi-lovers relating to negative mass - > the hope is to produce an FTL drive somehow. This triggered off a > memory and I'm hoping someone can contribute. > > In about 1966 I attended a seminar by Prof. Fairbanks who researched > at Stanford U (I think). He was trying to slow down positrons for long > enough to tell if they fell upwards or downwards. > > Does anyone know how this turned out? If this experiment did not get > completed, has there been any other work? -------------------- There is a theorem of particle physics which states that all particles with a negative mass travel backwards in time. This means that the positrons will fall upward, but they do it backwards, so one sees a downward fall forwards in time. Since all the effects of a negative mass cannot be distinguished from positive mass, all particles are labeled with a positive mass just to keep things simple. All this comes from charge, parity, and time symmetry arguements. Brian Sutin -- Princeton Astrophysical Sciences
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (08/26/85)
> There is a theorem of particle physics which states that all > particles with a negative mass travel backwards in time. ... > All this comes from charge, parity, and time symmetry arguements. How do you relate mass to CPT?
pmk@prometheus.UUCP (Paul M Koloc) (08/26/85)
> > There is a theorem of particle physics which states that all > > particles with a negative mass travel backwards in time. ... > > All this comes from charge, parity, and time symmetry arguements. > > How do you relate mass to CPT? I don't know if there exists a theorem, but, mass is related to gravity. Terrific! So what. Well, gravity is weakly coupled to time. Gravitation field density affects the rate of time flow, and, if the field (mass) density could be infinite then rate of time flow would zero. But reverse???? No chance. From another perspective. My guess is that "negative gravity" would be repulsive (by definition?) in our time orientation. By reversing the direction of time (playing a movie of such an event backwards) a "negative gravity event" would transform to a "positive gravity" one. Neat, huh? Dumb, it appears that the positron (with its hypothetical negative mass) "keeps up with us in time". If it were traveling backwards in time then, except for a single "collision time frame" the the NM positron would not exist in our space-time world. My conclusion is that positrons have normal mass, and excluding a "single time frame event" any coupling of mass to Time direction is moot. It is self contradictory or at least it doesn't appear logical to me. If, however, positrons are experimentally proven to have "negative mass", then I would be willing to reconsider my position, ---- but give me a couple of weeks advanced notice before publishing. :-) :-) - - NOTE: MAIL PATH MAY DIFFER FROM HEADER - - +-------------------------------------------------------+--------+ | Paul M. Koloc, President: (301) 445-1075 | FUSION | | Prometheus II Ltd., College Park, MD 20740-0222 | this | | ..umcp-cs!seismo!prometheus!pmk.UUCP | decade | +-------------------------------------------------------+--------+
ethan@utastro.UUCP (Ethan Vishniac) (08/26/85)
[] > > In about 1966 I attended a seminar by Prof. Fairbanks who researched > > at Stanford U (I think). He was trying to slow down positrons for long > > enough to tell if they fell upwards or downwards. > > > > Does anyone know how this turned out? If this experiment did not get > > completed, has there been any other work? > -------------------- > The existence of negative mass (i. e. mass that falls up) would blow > general relativity out of the water as it violates the equivalence > principle. Also, the equivalence of gravitational and inertial mass > has been shown experimentally to great accuracy (I can't remember the > experimental error). I don't know whether anyone has directly > experimentally determined that positrons fall down, I do (unfortunately I can't remember the reference but it was about 3-5 years ago). Antimatter falls. -- "Support the revolution Ethan Vishniac in Latin America... {charm,ut-sally,ut-ngp,noao}!utastro!ethan Buy Cocaine" ethan@utastro.UTEXAS.ARPA Department of Astronomy University of Texas
tan@ihlpg.UUCP (Bill Tanenbaum) (08/26/85)
> > There's a discussion on net.scifi-lovers relating to negative mass - > > the hope is to produce an FTL drive somehow. This triggered off a > > memory and I'm hoping someone can contribute. > > > > In about 1966 I attended a seminar by Prof. Fairbanks who researched > > at Stanford U (I think). He was trying to slow down positrons for long > > enough to tell if they fell upwards or downwards. > > > > Does anyone know how this turned out? If this experiment did not get > > completed, has there been any other work? > -------------------- > [Brian Sutin] > There is a theorem of particle physics which states that all > particles with a negative mass travel backwards in time. This means > that the positrons will fall upward, but they do it backwards, so one > sees a downward fall forwards in time. Since all the effects of a > negative mass cannot be distinguished from positive mass, all > particles are labeled with a positive mass just to keep things simple. > All this comes from charge, parity, and time symmetry arguements. > -------------------- Mr. Sutin's theorem is correct, but since particle physics (without gravity) deals only with inertial mass, not gravitational mass, it does not say anything about how positrons behave in a gravitational field. To answer that question, you need also the gravitational mass of the positron. The equivalence principle of General Relativity is needed here. -- Bill Tanenbaum - AT&T Bell Labs - Naperville IL ihnp4!ihlpg!tan
myers@bnl.UUCP (Eric Myers) (08/27/85)
> On a more morbid note, suppose antimatter could be contained, > presumably in an electric field inside a vacuum bottle. Off hand, it > seems that such an apparatus could be very small--perhaps briefcase > sized. It wouldn't take very much antimatter to make a very powerful > bomb... Today's Science Times (NY Times, 27 August) has an interesting article about the production of anti-protons at Fermilab, and it briefly discusses the use of anti-matter for space propulsion or for bombs. One thing they fail to mention is where all this anti-matter is supposed to come from. It appears that the entire observed universe is made of matter, not anti-matter (why this is so is currently a puzzle), so it would have to be made in an accelerator, with great expense and difficulty. You don't need much of the stuff, that's true, but for a rocket or a bomb you'd need more than a few million particles. So I think that the article was a little too dreamy and focused on the wrong point. Still, it is interesting to know the latest going's on at Fermilab. -- Eric Myers, Physics Dept., Brookhaven National Laboratory, Lon Guyland, NY myers@bnl.arpa / myers@bnl.bitnet / philabs!sbcs!bnl!myers
drdave@rocksvax.UUCP (08/30/85)
nti-particles respond to gravity just like "regular" ones. This was "proved" conclusively about 20 years ago when it was pointed out that if particles and anti-particles were affected in opposite ways by gravity, then the K-0 /anti-K0 interference effects wouldn't work. Very elegant proof by I believe Jim Fitch (of the Cronin&Fitch team that discovered CPT violation). Dave Birnbaum
jheimann@bbncc5.UUCP (John Heimann) (08/30/85)
>Very elegant proof by I believe Jim Fitch (of the Cronin&Fitch team >that discovered CPT violation). > >Dave Birnbaum You mean CP violation. For those who are interested, I recently came across the original report of the K0-decay experiment. As I recall, it's J.H. Christenson, J.W. Cronin, V.L. Fitch, and R. Turley, _Phys._Rev._Letters_, _13_, 138 (1964). Does anybody know of any other CP-violating process? John
mcgeer%ucbkim%Berkeley)@sri-unix.ARPA (09/03/85)
From: mcgeer%ucbkim@Berkeley (Rick McGeer (on an aaa-60-s)) One thing they fail to mention is where all this anti-matter is supposed to come from. It appears that the entire observed universe is made of matter, not anti-matter (why this is so is currently a puzzle), I've heard this before, but I don't understand how anyone can make this claim. How can we tell that Andromeda, say, is composed of matter and not anti-matter? What observational differences would there be between a matter galaxy and an anti-matter galaxy? The only difference between a particle and its anti-particle is charge, and large agglomertaions of matter are electrically neutral. No? -- Rick.
grl@charm.UUCP (George Lake) (09/04/85)
I've tried to avoid this, relying on Ethan to tidy up these disputes when they go too far. Antimatter has not been observed to fall. What has been shown is that virtual positrons behave like virtual electrons. There are a couple of people around here who always grouse about the virtual and have plans on the back burner to drop real positrons. Nobody has yet.
Physics@sri-unix.ARPA (09/07/85)
---------------------------------------------------------------- Date: Wed, 4-Sep-85 06:18:47 PDT From: ihnp4!houxm!mhuxt!mhuxr!mhuxn!charm!grl@UCB-Vax.arpa (George Lake) Article-I.D.: <739@charm.UUCP> In-Reply-To: Article(s) <437@ttidcb.UUCP> <1115@ihlpg.UUCP>, <607@utastro.UUCP> I've tried to avoid this, relying on Ethan to tidy up these disputes when they go too far. Antimatter has not been observed to fall. What has been shown is that virtual positrons behave like virtual electrons. There are a couple of people around here who always grouse about the virtual and have plans on the back burner to drop real positrons. Nobody has yet.
Cramer%CSL60%ti-csl.csnet@CSNET-RELAY.ARPA (09/17/85)
From: Nichael <Cramer%CSL60%ti-csl.csnet@CSNET-RELAY.ARPA> >>How can we tell that Andromeda, say, is composed of matter and not >>anti-matter? What observational differences would there be between a matter >>galaxy and an anti-matter galaxy? The space between the Milky Way and Andromeda isn't a perfect vacumn. Were Andromeda made of anti-matter, there would have to be matter/anti-matter frontier somewhere between us. I don't have any numbers to back this up, but it seems that the resulting spike in the background radiation at ~1MeV would be easily observable. NLC -------
Cramer%CSL60%ti-csl.csnet@CSNET-RELAY.ARPA (09/18/85)
From: Nichael <Cramer%CSL60%ti-csl.csnet@CSNET-RELAY.ARPA> [Our system crashed during my first attempt to send this. Sorry, if you get this twice.] >>I've heard this before, but I don't understand how anyone can make this >>claim. How can we tell that Andromeda, say, is composed of matter and not >>anti-matter? What observational differences would there be between a matter >>galaxy and an anti-matter galaxy? The only difference between a particle The space between the Milky Way and Andromeda, while a REAL GOOD vacumn, is not a perfect vacumn, and so there would have to a matter/antimatter frontier somewhere. While I don't have any numbers for this it seems that the highly anisotropic distortions in the background radiation resulting from the matter/antimatter interactions should be easily observable. This radiation should have a clearly defined spectrum; a nice spike at ~1Mev, for instance. NLC -------
FAILOR%LLL@LLL-MFE.ARPA (09/19/85)
From: Bruce Failor <FAILOR@LLL.MFENET>
To: Physics@SRI-UNIX.ARPA
In-Reply-To: Message from "Physics@SRI-Unix" of Thu 19 Sep 85 00:50:28-PDT
By the way, does anyone know how good a vacuum intergalactic
(and interstellar) space is, say in protons or electrons per cc?
According to what I have heard, it is mainly H.
One of the professors on a friend's oral examination committee asked
a question about the time of arrival of high energy photons. The prof
maintained that the arrival time was a function of energy with a
threshold at the energy required to produce an electron-positron pair.
If pair production is the process that causes the lag, there needs to
be protons or other nuclei available to allow for momentum and energy
conservation. He stated that the high energy photons produce pairs
which in turn annihilate which in turn produce pairs, etc.
Since matter travels at less than the speed of light, the photons that
spend the most time as electon-positron pairs will experience the most
time lag.
Has anyone else heard of this/know of references to actual
measurements?
Bruce Failor
-------