Anti-matter / anti-gravity question

DougC · #1 by **DougC** » Jan 31, 2012 2:59 am

The question of whether normal matter's shadowy counterpart anti-matter exerts a kind of "anti-gravity" is set to be answered, according to a new report.

http://www.bbc.co.uk/news/science-environment-16756457

klazmon · #2 by **klazmon** » Jan 31, 2012 8:16 am

Yep. It is actually very difficult to measure the acceleration due to gravity of elementary particles, especially charged ones. Cold neutral atoms (or anti atoms in this case) are the best bet - I see the experiment mentioned was talking about positronium but than doesn't last long. Anyway, I would be very surprised if they don't show the same gravitational attraction as normal matter. Mass/Energy gravitates and anti matter has the normal quantity of mass/energy via momentum considerations measured from its production. So if anti matter had anti gravity it would be a major conundrum.

trubble76 · #3 by **trubble76** » Jan 31, 2012 1:08 pm

They make it sound really difficult to check, but wouldn't it be as simple as creating a beam of your chosen anti particle and then measuring any deflection caused by moving a mass close to the beam?

advaitya · #4 by **advaitya** » Jan 31, 2012 1:24 pm

How'd this anti-gravity phenomena be different from the mythical dark energy?

twistor59 · #5 by **twistor59** » Jan 31, 2012 1:34 pm

trubble76 wrote:They make it sound really difficult to check, but wouldn't it be as simple as creating a beam of your chosen anti particle and then measuring any deflection caused by moving a mass close to the beam?

The problem is that the particles are so damn light and the gravitational force is so damn weak that getting any measurable damn deflection is tricky !

twistor59 · #6 by **twistor59** » Jan 31, 2012 1:37 pm

advaitya wrote:How'd this anti-gravity phenomena be different from the mythical dark energy?

Dark energy is some hypothetical scalar field that exists everywhere and causes a spatial expansion. Anti matter falling the other way in gravity wouldn't explain the expansion, since antimatter isn't all -pervasive throughout the universe.

trubble76 · #7 by **trubble76** » Jan 31, 2012 1:37 pm

twistor59 wrote:
trubble76 wrote:They make it sound really difficult to check, but wouldn't it be as simple as creating a beam of your chosen anti particle and then measuring any deflection caused by moving a mass close to the beam?

The problem is that the particles are so damn light and the gravitational force is so damn weak that getting any measurable damn deflection is tricky !

Sure, but that is partly the reason that we built fuck-off big machines with equally fuck-off big detectors, isn't it? Compared to some of the mind-bending experiments currently being run, measuring a small deflection in a particle beam seems like childs play to me. What am I missing?

twistor59 · #8 by **twistor59** » Jan 31, 2012 1:48 pm

trubble76 wrote:
twistor59 wrote:
trubble76 wrote:They make it sound really difficult to check, but wouldn't it be as simple as creating a beam of your chosen anti particle and then measuring any deflection caused by moving a mass close to the beam?

The problem is that the particles are so damn light and the gravitational force is so damn weak that getting any measurable damn deflection is tricky !

Sure, but that is partly the reason that we built fuck-off big machines with equally fuck-off big detectors, isn't it? Compared to some of the mind-bending experiments currently being run, measuring a small deflection in a particle beam seems like childs play to me. What am I missing?

Just the pathetic weakness of the gravitational force.

trubble76 · #9 by **trubble76** » Jan 31, 2012 1:55 pm

twistor59 wrote:
trubble76 wrote:
twistor59 wrote:
trubble76 wrote:They make it sound really difficult to check, but wouldn't it be as simple as creating a beam of your chosen anti particle and then measuring any deflection caused by moving a mass close to the beam?

The problem is that the particles are so damn light and the gravitational force is so damn weak that getting any measurable damn deflection is tricky !

Sure, but that is partly the reason that we built fuck-off big machines with equally fuck-off big detectors, isn't it? Compared to some of the mind-bending experiments currently being run, measuring a small deflection in a particle beam seems like childs play to me. What am I missing?

Just the pathetic weakness of the gravitational force.

But with a deflection, even an unimaginably small one, all you need to do is to apply the deflection for a greater period of time, no?
For example, if I deflect a laser beam on my desk by 0.00000001%, I would be hard pressed to spot it, but if I extended the beam by several factors, the deflection would become increasingly easy to spot, wouldn't it?
It just seems to be a relatively simple problem, when compared with some of the incredible physics we seem to engage in on a regular basis.

twistor59 · **#10** by **twistor59** » Jan 31, 2012 2:02 pm

trubble76 wrote:
twistor59 wrote:
trubble76 wrote:
twistor59 wrote:

The problem is that the particles are so damn light and the gravitational force is so damn weak that getting any measurable damn deflection is tricky !

Sure, but that is partly the reason that we built fuck-off big machines with equally fuck-off big detectors, isn't it? Compared to some of the mind-bending experiments currently being run, measuring a small deflection in a particle beam seems like childs play to me. What am I missing?

Just the pathetic weakness of the gravitational force.

But with a deflection, even an unimaginably small one, all you need to do is to apply the deflection for a greater period of time, no?
For example, if I deflect a laser beam on my desk by 0.00000001%, I would be hard pressed to spot it, but if I extended the beam by several factors, the deflection would become increasingly easy to spot, wouldn't it?
It just seems to be a relatively simple problem, when compared with some of the incredible physics we seem to engage in on a regular basis.

But keeping the particles in a beam (like they did with positrons in the LEP days)*, they apply massive confining magnetic fields which completely swamp any gravitational effects, even for a long beam. For some reason, the new approach has overcome that problem. I've not seen the details on how the new approach works though.

Edit: or even like they do now with antiprotons

twistor59 · **#11** by **twistor59** » Jan 31, 2012 2:12 pm

Not much more information but a bit here:

In the case of positronium, CassidyMills, a professor of physicsastronomy, were interested in achieving a long lifetime for the atom in their experiment. At the Rydberg level, positronium's lifetime increases by a factor of 10 to 100.

"But that's not enough for what we're trying to do," Cassidy said. "In the near future we will use a technique that imparts a high angular momentum to Rydberg atoms," Cassidy said. "This makes it more difficult for the atoms to decay,they might live for up to 10 milliseconds - an increase by a factor of 100,000 -offer themselves up for closer study."

CassidyMills already have made Rydberg positronium in large numbers in the lab. Next, they will excite them further to achieve lifetimes of a few milliseconds. They will then make a beam of these super-excited atoms to study its deflection due to gravity.

"We will look at the deflection of the beam as a function of flight time to see if gravity is bending it," Cassidy explained. "If we find that antimattermatter don't behave in the same way, it would be very shocking to the physics world.

trubble76 · **#12** by **trubble76** » Jan 31, 2012 2:17 pm

twistor59 wrote:
trubble76 wrote:
twistor59 wrote:
trubble76 wrote:

Sure, but that is partly the reason that we built fuck-off big machines with equally fuck-off big detectors, isn't it? Compared to some of the mind-bending experiments currently being run, measuring a small deflection in a particle beam seems like childs play to me. What am I missing?

Just the pathetic weakness of the gravitational force.

But with a deflection, even an unimaginably small one, all you need to do is to apply the deflection for a greater period of time, no?
For example, if I deflect a laser beam on my desk by 0.00000001%, I would be hard pressed to spot it, but if I extended the beam by several factors, the deflection would become increasingly easy to spot, wouldn't it?
It just seems to be a relatively simple problem, when compared with some of the incredible physics we seem to engage in on a regular basis.

But keeping the particles in a beam (like they did with positrons in the LEP days)*, they apply massive confining magnetic fields which completely swamp any gravitational effects, even for a long beam. For some reason, the new approach has overcome that problem. I've not seen the details on how the new approach works though.

Edit: or even like they do now with antiprotons

Ah ok, I think we are getting to the nuts of it now. The magnetic fields used to confine the beam overwhelms the gravitational effects. I suppose the answer to that would be to run the experiment a numberless amount of times and see if a trend pokes it's nose out of the noise.

twistor59 · **#13** by **twistor59** » Jan 31, 2012 2:26 pm

Yeah, the fact they're using a neutral atom (positronium) means that they don't have to use the confining fields like they have in the LHC. They do, however, seem to have to keep pumping it to keep it in that Rydberg state. I've no idea what that entails.

Given that positronium is one particle + one antiparticle, if the anti particle is anti gravitational it should be weightless. If they observe a fall given by the expectation with two electron masses, then they've falsified the anti gravity theory. Which they will !

trubble76 · **#14** by **trubble76** » Jan 31, 2012 2:36 pm

twistor59 wrote:Yeah, the fact they're using a neutral atom (positronium) means that they don't have to use the confining fields like they have in the LHC. They do, however, seem to have to keep pumping it to keep it in that Rydberg state. I've no idea what that entails.

Given that positronium is one particle + one antiparticle, if the anti particle is anti gravitational it should be weightless. If they observe a fall given by the expectation with two electron masses, then they've falsified the anti gravity theory. Which they will !

Thanks for sticking with me through another demonstration of my lack of physics knowledge. You are a most patient tutor. :cheers:

twistor59 · **#15** by **twistor59** » Jan 31, 2012 2:43 pm

trubble76 wrote:
twistor59 wrote:Yeah, the fact they're using a neutral atom (positronium) means that they don't have to use the confining fields like they have in the LHC. They do, however, seem to have to keep pumping it to keep it in that Rydberg state. I've no idea what that entails.

Given that positronium is one particle + one antiparticle, if the anti particle is anti gravitational it should be weightless. If they observe a fall given by the expectation with two electron masses, then they've falsified the anti gravity theory. Which they will !

Thanks for sticking with me through another demonstration of my lack of physics knowledge. You are a most patient tutor.

TBH I don't really know what I'm talking about, I know very little about particle physics :oops:

trubble76 · **#16** by **trubble76** » Jan 31, 2012 3:02 pm

twistor59 wrote:
trubble76 wrote:
twistor59 wrote:Yeah, the fact they're using a neutral atom (positronium) means that they don't have to use the confining fields like they have in the LHC. They do, however, seem to have to keep pumping it to keep it in that Rydberg state. I've no idea what that entails.

Given that positronium is one particle + one antiparticle, if the anti particle is anti gravitational it should be weightless. If they observe a fall given by the expectation with two electron masses, then they've falsified the anti gravity theory. Which they will !

Thanks for sticking with me through another demonstration of my lack of physics knowledge. You are a most patient tutor.

TBH I don't really know what I'm talking about, I know very little about particle physics

In the land of the blind snakes, the one-eyed snake... or something like that.

Xaihe · **#17** by **Xaihe** » Jan 31, 2012 5:18 pm

Gravity affects particles that are their own antiparticles, like photons. Assuming these particles also cause/interact with/affect gravity, that would definitely be a problem for the idea that antiparticles cause anti-gravity.

CdesignProponentsist · **#18** by **CdesignProponentsist** » Jan 31, 2012 6:31 pm

My guess is that anti-matter has normal gravity. Wouldn't a particle that exerts anti-gravity require negative mass?

xtraordinaryevidence · **#19** by **xtraordinaryevidence** » Jan 31, 2012 6:57 pm

Isn't anti-matter essentially the same as matter but with opposite charge (and/or spin?)? Different types of ordinary matter have different charges but are affected by gravity, so they are right in that it would shock the physics world.

RationalVegan · **#20** by **RationalVegan** » Jan 31, 2012 8:52 pm

CdesignProponentsist wrote:My guess is that anti-matter has normal gravity. Wouldn't a particle that exerts anti-gravity require negative mass?

Is negative mass possible? Would that not be the same as having negative size and is negative size not impossible?