|In space gravitational force acts, then why we can
not write with pencil /pen in space(outside the
|Question Date: 2016-10-15|
You can write in orbit just like you can on
Earth. The problem is that when you push down
on the paper, the paper pushes back on you. On
Earth, that's not a problem, because the desk
below the paper is pushing up on the paper just as
the paper pushes down on the desk, and the floor
pushes up on the desk as the desk pushes down on
the floor, and then the floor pushes down on the
ground and the ground pushes up on the floor.
All of this is because the center of the Earth
is not being acted on by gravity, because it's
at the center where the force equals out in all
directions. This means that you sitting at your
chair at your desk is possible because gravity is
pulling down on you but the chair can't fall down
because the floor is in the way (and the floor
can't fall because the ground is in the way).
In space, you, the paper, the chair, the desk,
the space ship, and everything else are all
falling at the same rate. So you writing on the
paper will push the paper away from you, and push
you away from the paper. This isn't a problem if
you strap yourself down, somehow, like wearing a
A pen and pencil both work in outer space! A
pencil is always usable. It writes words with
lead-graphite, which leaves a trail on paper. A
pen, on the other hand would not work in all of
space. The pen writes words with ink. In order to
leave an ink trail on paper, gravity must be
pushing the ink out of the pen. This is why you
cannot write upside-down, nor in zero-gravity.
However, there are pens that do not require
gravity to push the ink out. These pens are
used by NASA, and have a pump that pushes ink out
of the pen.
Maybe instead of inventing this crazy
space-pen, next time we could just bring a pencil.
I hope this answers your question!
You can write with a pencil in space
because the pencil needs friction to transfer
graphite from the lead to the paper.
You can't write with a pen because it
Americans made an expensive pen that worked
with no gravity. They proudly presented it to the
Russian astronauts who showed the Americans that
they could just use a pencil. ... But the pen
would be good so one couldn't just erase stuff
later to hide evidence!
Some people think that in outer space, you
can't write with pencils or pens. But this is a
myth! It turns out that you can write with
pencil or with pen in outer space.
The reason doesn't have much to do with
gravity. The main force involved in writing is
actually the force from your hand and fingers
pushing graphite or ink into paper. Once your
pencil or pen has pressed some graphite or ink
into the page, it is stuck there, even without
gravity. (After all, when you turn a page upside
down here, gravity cannot make the words fall off
Astronauts do have other things to worry about
for their writing instruments, though. For
example, pencils often leave wood shavings or
graphite breaks off of the tip. These shavings
will float around, since the gravitational pull
from the Earth is much weaker in outer space.
The temperature and pressure in outer space may
also be very different than on Earth. This can
affect how pens work, like by making them leaky.
This is a great question! First of all, you
are correct when you say that the gravitational
force acts in space. In fact, gravity is one of
the only forces that is very long range (acts over
very large distances). However, the gravitational
force between two objects gets weaker and weaker
the farther away the two objects are from each
MATH ALERT: The force of gravity
between two objects is proportional to:
(M1 x M2)/(r2)
Where M1 is the mass of
object 1, M2 is the mass of
object 2, and r is the distance between the
centers of the two objects. That means, that if
you double the distance between two objects, the
force goes down by a factor of 4!
Now that we understand how gravity gets weaker
with distance, let’s talk about the pens and
pencils. You are right when you say a typical
ballpoint pen will not work outside Earth’s orbit.
This is because a ball point pen works by letting
ink slowly travel down a hollow tube until it
meets a tip with a rotating ball. The ball holds
the ink in place until you roll the ball on a
piece of paper. In a typical ball point pen, the
flow of the ink is due to gravity alone. If you
hold a typical ball point pen upside down for a
long time, the ink will flow to the opposite end
of the tube and you will need to hold the pen the
correct way for a while before it writes again.
Since this process depends on Earth’s gravity, the
pen will not work as well in space where the
gravity is much weaker. There are special pens
that have a pressurized tube that forces the ink
towards the tip no matter how you hold then pen,
and these pens will work in space just as well as
they work on Earth.
However, a pencil doesn’t depend on gravity at
all! So a pencil will work just fine in
space (but the graphite shavings that come off
the pencil and don’t stick to the paper might
float around the space craft forever!)
Thanks for being so curious. Keep asking
Let's consider a specific scenario in space, a
space station that orbits around the earth.
Indeed, the gravitational force from the earth
does act on astronauts in the space station, but
because the space station is rotating around the
earth, there is also an effectively a centrifugal
force that cancels the gravitational force.
So inside the space station, an astronaut does not
feel any force at all. Then many gravity-based
phenomena no longer exist any more. For example,
we can no longer write with a pen. But, we can
still write with a pencil.
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