[data_monkey]

I don't understand this result. How would this experiment be able to detect the "antigravity" of antimatter? If the Earth is curving space time in one direction and then antimatter is curving space time in the opposite direction, would not relative impact of the antimatter be so negligible to be undetectable? We are talking about the ability to "unbend" space time of what a particle or two relative to the mass of the earth? So what if it falls, that just means its barely unbending space time.

To use an analogy, Let's say I am on the Amazon river (fastest river according to google). You want to detect which way I was swimming. Would you even be able to detect the marginal effects of me swimming upstream relative to the massively more impactful force from the river?

I am sure the problem here is me, so if someone can correct my thinking.

[mnw21cam]

You're making a very interesting distinction between the experimental result, which is that antimatter follows the same space-time curve as normal matter, and the dashed hope of warp drives, which is that antimatter causes the same space-time curve as normal matter.

However, if antimatter were to create a negative curvature but follow positive curvature, then you would be able to put a lump of normal matter next to a lump of antimatter, connect the two together, and the whole mechanism would spontaneously accelerate forever, breaking the laws of conservation of energy and momentum. For that reason, I think this experiment also gives us high confidence that antimatter causes exactly the same space-time curvature as normal matter, even though we haven't gathered enough antimatter to see it creating a normal space-time curvature. In essence, gravity is symmetrical.

[stromgo]

Maybe it helps to consider all 4 possibilities for the sign of the gravitational mass of antimatter, and the sign of the inertial mass of antimatter?

(-,-): antimatter would fall down, but we could break conservation laws with a mechanism.

(+,-): antimatter would fall up, but we could break conservation laws with a mechanism using electrically charged particles.

(-,+): antimatter would fall up, but ruled out by the experiment.

So what remains is (+,+)?

[elil17]

To my understanding, the researchers released antimatter particles with detector plates above and below them. The particles started out traveling in random directions. Some of the particles hit the top, some hit the bottom. They saw that more particles hit the bottom than the top.

If the particles had "anti-gravity", they'd be repulsed by the large mass of the earth (instead of attracted), and you'd have expected more to hit the top plate than the bottom plate.

The researchers also added a magnet to the top designed to cancel out the downward force from gravity, and they hit the top and bottom plate at even rates.

[pvaldes]

Hum, How can they be sure that what is hitting the plate is still antimatter? (Or only antimatter?)

[ben_w]

Positrons react with electrons to produce a distinctive pair of 511 keV photons travelling in opposite directions in the frame of reference of their collision.

There's also a much more complex mess that happens when protons react with antiprotons.

[dmurray]

> To use an analogy, Let's say I am on the Amazon river (fastest river according to google). You want to detect which way I was swimming. Would you even be able to detect the marginal effects of me swimming upstream relative to the massively more impactful force from the river?

Definitely yes! If you're even a reasonably competent swimmer you should be able to outswim the Amazon and make headway upstream at most points.

I'm not sure what this says about your analogy, but I would think the measurement devices are millions of times more sensitive than needed to detect which way you were swimming.