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I read this article where the title suggests the iPhone was dropped from space, but it looks more like it was dropped from an airplane

I would think that if astronauts dropped an iPhone from space that it wouldn't land on Earth, but rather, float on for infinity (our Universe keeps expanding), or would the iPhone be captured in some planet's gravitational force and drop there.

Help me understand this physics principle.

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    $\begingroup$ I can't phrase an answer well enough, but the gist of it would be that if it's dropped from orbit, the iPhone will keep orbiting until orbital decay brings it down to Earth. $\endgroup$
    – HDE 226868
    Jan 16, 2015 at 16:30
  • $\begingroup$ If you switch out "iPhone" for "spoon" this is a possible duplicate of physics.stackexchange.com/questions/140980/… $\endgroup$
    – Sean
    Jan 16, 2015 at 16:48
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    $\begingroup$ I highly recommend you read what-if.xkcd.com/58 for general clarification of "what space is". Astronauts so far have always been in orbit around either earth directly, or the moon (which of course itself orbits the earth). If you go "deeper into space", you start orbiting the sun independently, and even is in orbit around the center of the milky way. There is actually no such thing as "zero-g", being in space simply means you're free falling/orbiting. $\endgroup$
    – leftaroundabout
    Jan 16, 2015 at 16:59

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I would think that if astronauts dropped an iPhone from space that it wouldn't land on Earth

What exactly does "dropped" mean?

Standing on Earth, when we "drop" something we mean that we let go of something and gravity takes over.

With no gravity... It's not dropped. Just let go.

The iPhone will stay where it is (unless it has an initial speed of course), until something pushed or pulls in it - gravity from elsewhere, being hit by an object etc. If it will ever land on Earth again would strongly depend on where you let it go.

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  • $\begingroup$ Dropped means that you hold the iPhone and let it go in outer space $\endgroup$
    – Glowie
    Jan 16, 2015 at 16:26
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    $\begingroup$ @Sonihal: I guess the question is if you're in orbit when you drop it, or are you just above the earth? Or how far out into space are you? $\endgroup$
    – Zo the Relativist
    Jan 16, 2015 at 16:28
  • $\begingroup$ @JerrySchirmer I would say the deepest parts of space where astronauts have gone (not sure where that is though ???) $\endgroup$
    – Glowie
    Jan 16, 2015 at 16:39
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    $\begingroup$ Heh, that would be the moon -- the answer would be that it would fall to the surface of the moon. $\endgroup$
    – Zo the Relativist
    Jan 16, 2015 at 18:18
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Cool find! That balloon+camera+parachute rig looks like a great tool; the iPhone is just to distract journalists.

What happens to an object that's dropped from Earth's upper atmosphere or from low earth orbit depends on how much forward momentum the object has. After all, gravity isn't actually that much weaker in low earth orbit than at the surface; the difference is that the atmosphere is tenuous enough that an object can circle the earth many times without losing much kinetic energy to heat or drag.

In your case the balloon burst at an altitude of about 100,000 feet, which is about 19 miles or 30 kilometers. That's not really outer space, but about in the middle of the stratosphere; the ISS's orbit is about ten times higher up that this, in the thermosphere. That's consistent with the behavior of the balloon-attached phone in your video, which goes more or less straight up from the ground and then returns to a nearby field.

If you wanted to put the phone in orbit, you'd have to both get it above the thickest part of the atmosphere and also give it a horizontal velocity of about 7 km/s.

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