Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: @monozuky on 19/01/2011 17:30:03
-
@monozuky asked the Naked Scientists:
Matter and matter attract each other.
What about matter and antimatter? They repulse? Also attract?
What do you think?
-
The relationship between particle and antiparticle is that they have the same mass (and spin, baryon number etc) but opposite charge. So, for instance, a proton and an anti-proton would be of opposite charge +1 and -1 (by definition) thus they would be attracted to each other - they would then annihilate each other to give off energy a/o other particles.
Matter is also attracted to matter with by the action of gravity - as the amount of gravitational attraction is determined (in part) by mass then the matter and antimatter would again attract each other as both have positive mass.
As a rule of thumb over small distances and with small particles look at the electric charge to see if objects will attract (particle /antiparticle will always do so) and for long distances and heavy objects look at gravity (and practically all gravity is attractive) - so in both cases anti-matter and matter will attract (and go bang when it meets!)
-
We discussed this question on our show
We posed this question to Professor Andy Parker from Cambridge University and Jeffrey Hangst from CERN...
Andy - If you just take a positron and an electron, they attract each other because they've got opposite electrical charges. But a much more interesting question is if you make a matter atom and an antimatter atom, do they then attract each other? Because if they were two atoms, they would have a positive pull together from gravity. So an interesting question which I think Jeffrey might like to comment on is whether there's some anti-gravitational force related to antimatter...
Jeffrey - It’s a very fascinating question and an experimental one that another group here at CERN hopes to answer. The short answer is that nobody knows because physics is fundamentally an experimental science, but people are planning on doing that experiment. Maybe in five to ten years, we’ll have an answer. Most people don't think that there’s antigravity. In other words, that antimatter and matter repel each other, but there may be some slight correction to the attraction. That's what the current thinking is, that’s as far as it goes at any rate.
Click to visit the show page for the podcast in which this question is answered. (http://www.thenakedscientists.com/HTML/podcasts/show/2011.01.23/) Alternatively, [chapter podcast=2987 track=11.01.23/Naked_Scientists_Show_11.01.23_7811.mp3](https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.thenakedscientists.com%2FHTML%2Ftypo3conf%2Fext%2Fnaksci_podcast%2Fgnome-settings-sound.gif&hash=f2b0d108dc173aeaa367f8db2e2171bd) listen to the answer now[/chapter] or [download as MP3] (http://nakeddiscovery.com/downloads/split_individual/11.01.23/Naked_Scientists_Show_11.01.23_7811.mp3)
-
I used to believe there was a chance antimatter could exhibit antigravitational properties. It turns out I was wrong. We have made antihydrogen now, and it exhibited no antigravitational properties.
-
I used to believe there was a chance antimatter could exhibit antigravitational properties. It turns out I was wrong. We have made antihydrogen now, and it exhibited no antigravitational properties.
Were they able to measure it gravitationally? The latest I'd heard, the general consensus was that there's no compelling reason to assume that antimatter has anti-gravity, but due to the tiny masses of antimatter created, and its instability, this has never actually been tested experimentally.
-
I used to believe there was a chance antimatter could exhibit antigravitational properties. It turns out I was wrong. We have made antihydrogen now, and it exhibited no antigravitational properties.
Were they able to measure it gravitationally? The latest I'd heard, the general consensus was that there's no compelling reason to assume that antimatter has anti-gravity, but due to the tiny masses of antimatter created, and its instability, this has never actually been tested experimentally.
What they are specifically looking for is a matter which by theory, should act completely symmetric with respect to ordinary matter. You are completely correct however, there is no reason other than purely hypothetical (not even theoretical) that would suggest antimatter has an antigravity repelling subtsance to it. But then again, we have never directly viewed such a particle and so the questioned remained for a while that perhaps the negative solution of -Mc2 could have exhibited what we would call an exotic antigravitational matter. It goes to question however, no matter how wild the hypothetical model went (and what this site calls a ''new theory'' lol) it must have been on the back of physicists mind for there to have been an investigation into it. I know a lot of the data is still being analyzed, but when this was reported to me, it was said no antigravitational effects had been witnessed...
-
But the CERN experiment write-up that I read only had single anti-hydrogen atoms held at any one time (they got 30ish over a few hundred runs) - there is no mechanism for ascertaining gravitational attraction/repulsion for a single atom. I haven't read any more recent articles on this - but it is clear that it is ongoing; the latest podcast had two anti-matter physcists and one refered to the fact that they can now isolate for 10^3 seconds whereas the article below is in the 10^-3 seconds range
Here is the initial write-up from a few months ago http://www.nature.co...ature09610.html - it's behind a paywall I'm afraid - but here is a quote "Our work is a crucial step towards precision antihydrogen spectroscopy and anti-atomic tests of fundamental symmetries or gravitation."
It makes mention of a CERN proposal for creating an experiment to test these ideas
Drobychev, G. Y. et al. Proposal for the AEGIS experiment at the CERN antiproton decelerator (antimatter experiment: gravity, interferometry, spectroscopy). Tech. Report SPSC-P-334; CERN-SPSC-2007–017 (European Organization for Nuclear Research, 2007)
-
The really interesting question to me is what it say about particles, be they positive or negative. They annihilate each other, don't they?
And if 'energy' is an expression of interactions and no 'primal stuff' in itself? Then what you think are 'particles' I think are expressions of interaction too. And if that is correct you need to ask yourself what makes for those 'positive' expressions taking the upper hand. And that I expect to be regulated by constants.
-
But the CERN experiment write-up that I read only had single anti-hydrogen atoms held at any one time (they got 30ish over a few hundred runs) - there is no mechanism for ascertaining gravitational attraction/repulsion for a single atom. I haven't read any more recent articles on this - but it is clear that it is ongoing; the latest podcast had two anti-matter physcists and one refered to the fact that they can now isolate for 10^3 seconds whereas the article below is in the 10^-3 seconds range
Here is the initial write-up from a few months ago http://www.nature.co...ature09610.html - it's behind a paywall I'm afraid - but here is a quote "Our work is a crucial step towards precision antihydrogen spectroscopy and anti-atomic tests of fundamental symmetries or gravitation."
It makes mention of a CERN proposal for creating an experiment to test these ideas
Drobychev, G. Y. et al. Proposal for the AEGIS experiment at the CERN antiproton decelerator (antimatter experiment: gravity, interferometry, spectroscopy). Tech. Report SPSC-P-334; CERN-SPSC-2007–017 (European Organization for Nuclear Research, 2007)
This is true. I don't know what extent this has been investigated, all I know is there is plenty more data to analyze.