I'm with you on this one. If antimatter was just backwards everything then there'd be large conspicuous clusters of the stuff all over the cosmos because ordinary matter would be repelling it instead of annihilating it.
While there does seem to be a lot of dark matter out there, if it were actually antimatter and had opposite gravity to normal matter one would imagine there would be a huge discrepancy between cosmologists' models and observation. The high-end supercomputer simulations and regressions cosmologists employ have good predictive power, even though we lack a full explanation for the phenomena we can observe. Cosmologists deal with such far-out concepts to begin with (by definition) that it's not as if they'd be averse to a concept like antigravity if it had predictive utility.
toys idly with desk magnets while thinking about it
Then again, given that photons are massless maybe there could be such a thing as a gravitational dipole...
We know two things about dark matter:
- It doesn't interact electromagnetically.
- It does interact gravitationally and produces extra gravitational attraction beyond the electromagnetically interacting matter we know about.
- It is dispersed throughout galaxies.
The first property rules out baryonic antimatter as dark matter, since that would interact electromagnetically. The last two properties rule out anything that has a repulsive gravitational interaction as dark matter.
while we don't know whether it exists at all. Whatever phenomena are explained by DM are also easy explained by molecular hydrogen (i.e H2) which is almost not detectable. [The hydrogen we know about in the space is atomic - H, and there should be orders of magnitude more of molecular one than atomic when you have atomic at such interstellar space conditions]
We know that dark matter cannot be baryonic matter (atoms) for two reasons. First, models of the big bang that have been confirmed by experiment closely bound the total amount of baryonic matter in the Universe. Second, dark matter doesn't seem to behave the same way that baryonic matter behaves (normal matter clumps, dark matter doesn't appear to do so).
>...models of the big bang that have been confirmed by experiment ...
to put it mildly, it is a very overreaching statement.
>Second, dark matter doesn't seem to behave the same way that baryonic matter behaves (normal matter clumps, dark matter doesn't appear to do so).
double whammy - we couldn't observe dark matter and we couldn't observe its clumps.
Or consider it another way - while it supposedly have gravitational attraction, and have no other strong interactions known, we somehow should suppose that its non-clumping, ie. gaseous/cloudy/spread-around state is still a normal thing.
Well, let's see what the data says. I confess I want the universe to surprise and confound. I want the theories to be wrong, I want reality to be stranger than fiction. That would be awesome!
Or I am wrong, in which case I'll happily pay out[1]. I'm a layman, as if that wasn't obvious, and it will be a much-needed physics lesson. Win-win.
[1] If in Australia, payout will take the form of alcohol credits at an establishment of winner's choosing. Hey, I want to learn from my superiors :) If not, a crisp USD$100 note will be posted to any mailing address in the world, to be supplied.
I want the theories to be wrong too, it's just that I'm a sceptic in this case simply because of the utter awesomness that would be the result.
I will happily spend more than $100 just on delivery if that is required to make a payout in liquor (local Swedish flavors) across the world. Crisp paper is fully acceptable as well :)
Doubt we will ever settle this though... I have painfully little faith in scientific breakthroughs.
That reddit post (and admittedly it is just a reddit post) actually says the opposite: there is no theoretical basis for antimatter not to behave exactly like regular matter in the presence of a gravitational field.
The null hypothesis (and, in the absence of any strong evidence to the contrary, the stronger hypothesis) is that antimatter and matter respond to gravity in exactly the same way.
It is actually great that they're doing this experiment 'cos if it turned out in a way that contradicted theory (which I think says "antimatter falls") then we might have to re-examine a whole lot of things!
For example, if antimatter rises, there ought to be a statistical preference for black holes to emit antimatter.
One of the posters on that site said CPT violation would be another great thing to check. Hell yeah!
While there does seem to be a lot of dark matter out there, if it were actually antimatter and had opposite gravity to normal matter one would imagine there would be a huge discrepancy between cosmologists' models and observation. The high-end supercomputer simulations and regressions cosmologists employ have good predictive power, even though we lack a full explanation for the phenomena we can observe. Cosmologists deal with such far-out concepts to begin with (by definition) that it's not as if they'd be averse to a concept like antigravity if it had predictive utility.
toys idly with desk magnets while thinking about it
Then again, given that photons are massless maybe there could be such a thing as a gravitational dipole...
/timecube