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 seatbelt.

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 needs gravity.

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 the paper!)

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 other.

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 questions!

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.