Has anyone heard if they managed to observe the effect of gravity on the particles? The Nature article was vague...
I remember hearing that this was one of the reasons why they needed to trap antimatter for observable lengths of time. To my understanding, they aren't completely sure yet which way antimatter "falls."
It will still be a while before this is directly observed.
We're fairly sure that it "falls" downwards for a wide range of theoretical reasons and also due to the 1987 observation of gravitational lensing in neutrinos and antineutrinos from a supernova. If we observe the opposite in a lab then it will be incredible because we'll have to reevaluate a lot of what we think we know about physics. If we observe it "falling down" then it will be an important result but not at all revolutionary.
Antimatter has opposite electrical charge (and magnetic moment) from normal matter. It should have the exact same mass and interaction with gravity as normal matter.
An anti-electron is called a positron because it has a positive charge instead of negative. Antiproton (sometimes called negatron, but rarely) is just a proton with opposite charge. You can even make a hydrogen atom out of an antiproton and a positron, called antihydrogen. https://secure.wikimedia.org/wikipedia/en/wiki/Antihydrogen
I meant falling downwards towards the surface of the earth which would experimentally show that there is an attractive force between matter and antimatter. Experimentally showing that antimatter gravitationally attracts antimatter is next to impossible for technical reasons but there is even less doubt about this than about matter attracting antimatter. No matter how sure we think we are about something we can also be wrong though. Experiment gives us the final word (albeit with statistical limitations) and there have been numerous times in history where established theories have been flipped upside down by experiments.
This is actually somewhat of a complicated topic. The overwhelming expectation is that anti-matter has the same inertial and gravitational mass as ordinary matter does. However, there are some intriguing possibilities for matter that doesn't.
Consider what happens if an object has "negative mass" though. It would be repelled by ordinary matter. OK, simple enough though, right. But then what happens? Well, F = ma right? So the repulsive force would repel ordinary matter, but it would result in an attractive acceleration of the negative mass. Now, if it turned out that gravitational and inertial mass could be different, that would be an incredible result as well.
(only a very rough grounding in particle physics here)
it offers an explanation for the abundance of matter - if large enough quantities of matter and anti-matter are created, and can gain enough separation, then although the attractive forces of the electromagnetic attraction are strong, the result of gravity repulsing opposite matter types would separate them. so matter/anti-matter creation would be symmetric, but all the anti matter would be beyond the edge of the observable universe.
lets just hope the LHC doesn't create a mini black hole which eats up the planet, before we find out..!
To further venture down the rabbit hole: it's unlikely that anti-matter actually has negative inertial mass though. Since that would result in an electrostatic repulsion from normal matter (which would, for example, prevent an anti-proton from annihilating with a nucleus). The observational evidence is pretty strong that anti-matter has at least a positive inertial mass. There is a remote possibility that inertial and gravitational masses can be different, which would be a very unexpected result.
If only we could develop a small device (say the size of a briefcase) to convert electricity to antimatter and then slow release antimatter reaction back to electricity.
It would make electric vehicles much more economical than oil. We could finally make a ship that could pack enough punch to make a trip to the asteroid belt and back. To bring back the unobtainium.
The ability to carry road-trip quantities of antimatter in a briefcase would take the threat of terrorism to a whole new level. How much would you need to take out a plane? A building? A city?
Nuclear cars would be cool, too, but I think we need to consider the weaponizable nature (both for governmental military forces and for terrorists) of these technologies.
From Wikipedia: The reaction of 1 kg of antimatter with 1 kg of matter would produce [...] the rough equivalent of 43 megatons of TNT. For comparison, Tsar Bomb, the largest nuclear weapon ever detonated, reacted an estimated yield of 50 megatons.
I dare say this would take a briefcase bomb to a whole new level.
The energy density of antimatter has 9 more zero compared to TNT.
So, roughly speaking, a soda bottle of antimatter is a megaton of TNT[1]. Well, half a soda bottle if you ask the stewardess for a soda of non-antimatter once you get on the plane.
If you want to equal the largest of nuclear warheads tested, you will have to pay a small overage fee on your luggage.
[1] I'm ignoring containment overhead. Once you show me a gram of antimatter we can talk about containment.
There will be a scanner on the airport line that would detect antimatter atoms in quantities of more than a few thousand atoms, which is what you would need to create an explosion.
So the problem is making it safe enough to not explode even if the electric-antimatter converter is shot, crushed, disintegrated in an explosion or superheated.
Bond the anti hydrogen with anti Oxygen, Bond it with an anti-matter noble gas (elements that refuse to react). Maybe there is a creative way to make it hard to unlock into it's explosive state. That way you can only dole out the energy with a complex process that an accident would not recreate.
Antimatter will annihilate when it comes into contact with any normal matter; it's not a chemical reaction. You can't make antimatter 'inert' because it's reactivity doesn't depend upon some chemical property (arrangement of anti-electrons for example), but simply on the fact that it's antimatter. Hence the use of magnetic fields for containment since they prevent contact with ordinary matter.
Your airport scanner would thus have to infer the presence of antimatter rather than detecting it directly (by looking for high-energy photons), but if your containment vessel is leaking then you have bigger problems than law enforcement :-)
No there will not be a scanner because it's impossible to tell the difference from afar.
Scientists would LOVE to find a difference, it would explain so much about the universe.
And no, there is no "creative way to make it hard to unlock into it's [sic] explosive state". Such a thing is impossible. The only thing you can do is make some kind of really good containment.
And BTW a few thousand atoms is not much, even for anti-matter. It's about the energy of a flying mosquito.
> There will be a scanner on the airport line that would detect antimatter atoms in quantities of more than a few thousand atoms, which is what you would need to create an explosion.
If I've got a kilo of antimatter in a briefcase, I'm just going to set it off at the scanner then, killing the ~10k people in the airport... and half the city it's part of.
I can already buy an unlimited amount of gasoline from thousands of sources..
I can also buy any type of "missle" (read vehicle).
I can also buy fertilizer, cheaply.
Say I forego the fertilizer route, and fill my car full of gasoline. Now, all I need to is then put a rag in the gas intake and break off the tab. I have a molotov cartail, that, when steered does a lot of damage.
It's easy to kill people and cause terror. Moreso, if you are an engineer. But its decency and ethics that keep people from doing these sort of things.
Antimatter is a terrible store of energy because it is "fail-dangerous". The failure mode is a catastrophic release of energy.
The closest comparison for endurance would be nuclear power. Its worst failure mode is meltdown, which while very bad is nothing like as destructive as an AM explosion.
And it gets worse! Suppose your AM containment fails in a carpark. The explosion will cause a chain reaction of car explosions.
Finally, there is the incredible inefficiency with which AM is manufactured. It takes gigawatts and many hours of accelerator time to create even minute quantities. Because the only way we know of to create AM is smashing things together in particle accelerators. There aren't many LHCs to go around.
In the far future, I could see technology advancing enough to where we could efficiently create/manufacture antimatter (e.g. from a star or something).
But the "fail-dangerous" issue is more of a user responsibility, and I don't see that being solved anytime before the above technology is discovered (if ever).
Peter F Hamilton surmised in his Night's Dawn trilogy that antimatter would be outlawed, but produced by large accelerators parked close to suns in unoccupied solar systems. It was still heinously inefficient, but the high price of black-market AM justified the cost.
Putting speculation aside, we know that AM is fail-dangerous. For all current purposes, we have better alternatives. For long-endurance power sources we have fission. For weapons we have fusion.
I cannot personally think of a common use where the statistical certainty of failure outweighs the risk.
A lot of the yield in H-bombs actually comes from the fission of the depleted uranium tamper - in the Ivy Mike test (the first real multi stage H-bomb) 77% of the yield was generated this way:
The Tsar Bomb test was restricted to 50Mt by missing out the 3rd stage - so it was primarily a fusion device. Had the depleted uranium tamper been in place it would have given the 100Mt the design was capable of - but with horrific fall-out.
My knowledge in this domain is quite limited, but maybe someday somebody will figure something out. Just the thought of antimatter existing is very cool.
No it wouldn't make electric vehicles more economic. It takes many orders of magnitude more energy (and thus money) to create and capture antimatter than we'd ever get out of it in your car.
Right now it takes many orders of magnitude more energy.
When electricity was first being invented for human utility, I bet it took several orders of magnitude more energy to package it than to simply light a candle, for example.
Or when candles were first invented, it took several orders of magnitude more energy to create one than to keep a campfire going. Etc.
Right now we're at the "invent a candle" stage, and talking about the "hydroelectric dam" stage, so it's hard to imagine. But it's far from impossible.
