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  • "Hey, another atom. I'm hydrogen, nice to meet you.

  • How are you feeling about the jump?"

  • "Hi there, I'm antihydrogen, your antiatom,

  • and to be honest, I'm feeling kind of neutral.

  • My positron and antiproton balance out, just like your electron and proton, right?"

  • "Hey, yeah! You look just like me, but different somehow."

  • "Whoa, be careful! If we get too close, we'll disappear in a spark of energy.

  • I'd like to stay in one piece."

  • "Oh wow, sorry."

  • "It's okay. I was just thinking,

  • it's kind of weird for us to be chatting like this before our jump above CERN."

  • "Why's that?"

  • "Well, for starters, how do we know we'll both fall?"

  • "Of course we'll fall. It's gravity,

  • you know, the force of attraction between masses.

  • I even know how fast we should fall.

  • Galileo showed in that tower experiment

  • that all falling objects accelerate at the same rate, regardless of mass."

  • "That's for bigger objects.

  • It's a different story for small particles like us.

  • Our mass is so tiny that the gravitational force we experience is miniscule,

  • and if the particles are charged, like my antiproton or your proton,

  • then it becomes impossible to detect

  • compared to the much greater electromagnetic force acting on them."

  • "But that's only for charged particles. You and I are both neutral.

  • Our charges balance out, so the electromagnetic force is small

  • and the gravitational force should be detectable.

  • I know mine's been measured."

  • "Because you're everywhere, but I'm kind of hard to find."

  • "Why is that, anyway?

  • Shouldn't there have been an equal amount of matter and antimatter created in the Big Bang?"

  • "You'd think so, then all of those particles would have annihilated each other into energy, remember?

  • And the Universe is obviously full of matter.

  • No one knows why there is more matter than antimatter,

  • which is why scientists are so interested in studying me."

  • "So where do they find you anyway?"

  • "Actually, I was made in that lab down there.

  • They needed an accelerator to make my antiproton because it's so heavy,

  • just as heavy as your proton.

  • Getting my positron was easier.

  • It's much lighter, like your electron, and there are materials that naturally decay by emitting one.

  • Then they just had to put the two together and they got me.

  • But it's only recently that they've been able to keep me around long enough to study my properties."

  • "And now they've sent you on this jump with me. Hey, wait a minute."

  • "That's right. We're reenacting Galileo's experiment,

  • but with matter and antimatter instead of two objects made of matter."

  • "So what's going to happen?

  • Are you going to fall upwards or something?"

  • "Only one way to find out!"

"Hey, another atom. I'm hydrogen, nice to meet you.

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B1 US TED-Ed antimatter proton matter fall gravitational force

【TED-Ed】If matter falls down, does antimatter fall up? - Chloé Malbrunot

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    彭彥婷 posted on 2014/10/22
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