The Answer is "Black Hole"
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gravity is a constant force pulling down on you. jumping doesnt escape that fact.
a black hole.
A black hole
You are referring to a black hole.
I think it's because of gravity.
By invisible i assume you mean that the object does not emit electromagnetic radiation. In which case your answer is dark matter. Or potentially black holes (if you ignore the possibility of Hawking radiation).
Jupiter gases do not escape because Jupiter has enough gravity to hold the gases in place.
To overcome gravity, you must reach "Escape Velocity" to overcome gravity and escape a planet's orbit.
There is gravity in space. Gravity is everywhere. You can never escape gravity.
A black hole because it can be small and massive and not even light can escape it.
There is no way to escape from a black hole because it's gravity is infinite.
Escape velocity is the speed you would have to go to escape gravity.
Titan has sufficient gravity to hold onto an atmosphere.
A black hole because it can be small and massive and not even light can escape it.
No. All planets have gravity. Any object massive enough to be considered a planet would have strong enough gravity that you could simply escape by jumping. It is, however, possible for an object to escape the gravity of any planet if it is launched in the right way and with enough speed.
It is fantasy, and not real. But my guess would be that he put the parcel in his invisible bag, thus making the parcel invisible.