Questions about space

[Misr]

Hello ,

1-Why does space rocket can move through space while airplane cannot?

2-Why does plant roots grow upwards inside a spaceship?

[Yuqing]

Airplanes and Rockets both move due to Newton's third law of action and reaction. An airplane normally works by "pushing" on the air we have in our atmosphere to propel itself. There is no air in the vacuum of space. A rocket however moves forward by propelling fuel in the backwards direction thereby giving itself a forwards momentum.

As for the plants, plants are known to exhibit a phenomenon called gravitropism where polar auxin transport dictate the direction of growth. Without gravity in space, the direction of growth is dictated primarily by light.

[mathman]

1. Rocket is propelled by rocket engine which delivers a lot more thrust than an airplane engine. The space shuttle is a bit of a hybrid in that its return trip is partly like an airplane.

2. Inside a spaceship there is no up or down once it is in orbit.

[Misr]

Without gravity in space

Gravity does exist in space.
Thanks very much

[D H]

Gravity does exist in space.
Thanks very much
Not very helpful, and no need to be snarky.


As for the plants, plants are known to exhibit a phenomenon called gravitropism where polar auxin transport dictate the direction of growth. Without gravity in space, the direction of growth is dictated primarily by light.
To avoid the snarky replies, the latter sentence would be better expressed as "Without weight in space ..." ... And that is still going to get snarky replies. So be it. In anticipation of such replies, google the term weightlessness.

Yuqing's response is essentially correct. Plants in space grow toward light (the above ground part, that is). We physicists need to be somewhat forgiving regarding biologists technically incorrect use of the term gravity. Nothing can sense gravity. Nonetheless, to a biologist that is exactly what plants seem to do.

The part of a plant that is above the ground grows toward light in space. The part that is below the ground, the roots, are (anthropomorphizing) utterly confused due to the lack of clues. Plant roots exhibit very funky behavior in plants grown in a zero-g environment.