# Would a javelin fly further in a vacuum?

My current WIP involves an athletics competition on a non-terraformed moon, namely the Earth's moon. And while it would be a bit difficult to play certain sports without a breathable atmosphere, the javelin throw strikes me as an event that would be better enjoyed in the moon's 'fresh air' – or rather, lack of it. So, other than the additional challenge of wearing a space suit (and trying to make the damn thing land point first), I would expect an outdoor javelin throw on the moon, after accounting for other variables.

The only thing is: would it? I don't know if the air on Earth has the effect of reducing the length of a javelin throw through obvious frictional effects (as it would with a thrown stone or shot put) or increasing it by giving it something to glide on (as it would with a paper plane).

My hunch is that a realistic world record, after factoring in the other variables like restricted movement from wearing a space suit, would be somewhere in the 400-500 metre range for men, 300-400 metres for women, and 350-450 for eligible non-binary folks. (For comparison, the world records back on Earth currently stand at 98.48 and 72.28 metres for men and women respectively.) Are my guesses realistic?

• Aerodynamic lift is a thing in javelin flight, and flight behaviour is dependent on differential lift/drag turning it. There have been rules changes and re-designs prompted around athletes and manufacturers finding techniques that got further distance, and record distances have been adjusted as a result. How much of this would impact an answer is not clear to me, but I don't think it is straightforward. Sep 29, 2018 at 15:08
• Is it a record if you throw the javelin into orbit so that it never lands?
– Mark
Sep 29, 2018 at 20:20
• @Mark I actually did a back of the envelope calculation, and found that a lunar javelin thrower would achieve an extra 30-40 centimetres as a result of the moon's curvature. Space is weird. But unless they've taken some serious roids, I think the danger of missing the ground remains quite minimal. And even then, orbits decay. Sep 29, 2018 at 21:08
• Current edition javelins are slightly less effective in the L-D department than a ballistic trajectory. Men's javelins fall about 3 meters short of a ballistic trajectory at the elite level. Women's javelins are worse and fall about 15 meters short due do higher drag to mass ratio. Neither generate much of a aerodynamic (shuttlecock) stability, but the center of mass is forward of the pressure center, so there is an aero pitch down moment for positive angles of attack. Overall, expect the performance difference to be governed by gravity and possibly a higher run-up speed. Sep 29, 2018 at 22:42
• @mark, when you launch an unpowered object into space it has two options, escape orbit, or return from wence it came. As gravity is strong and even the strongest human weak, gravity airways wins Oct 1, 2018 at 3:13

With no air resistance and less gravity, check the astronauts playing golf. The ball reached an outstanding distance.

Also, since the shape won't matter due to no aerodynamic profile to speak of, you may throw a stone, ball, cube.

All that matters would be mass.

• I was thinking the same thing about the shape of the object that is thrown. Another fun fact: if a javelin were thrown with the tip pointing up at 45 degrees, then it would land with the tip still pointing up at a 45 degrees. The shaft is going only going to rotate at all if it's initially given a rotation. There's no wind resistance to cause the shaft to rotate 90 degrees, from tip-up to tip-down. Sep 29, 2018 at 14:20
• @BrettFromLA vacuum is weird :D Sep 29, 2018 at 16:55
• That run-on sentence though... Sep 29, 2018 at 16:55
• The tip would still point downwards, javelins don't end up falling point first due to air resistance, but because the front end is heavier than the rear end. Sep 29, 2018 at 18:09
• @TCAT117 how will the front end's greater weight make it fall faster without air resistance though? unless you mean some effect that imparts rotation upon release, the weight will not matter w/out aerodynamic effects. a hat and a cannon ball fall at the same speed in vacuum. Sep 29, 2018 at 18:17

From basic physics and the initial throwing speed of the javelin (33m/s for the best throwers) on earth I calculated that the furthest you can throw a javelin is 672m without friction and the much lower gravity of Earth's moon. Then it depends on how restricted movements are and how would athletes adapt to the 45° angle for the throw. The distance is proportional to the initial speed, so if the initial speed is 25m/s the distance will be 509m. It's also proportional to the reciprocal of your moon's gravity.

• Excellent answer. I'm terrible at math and I was gonna gear up to take a crack at butchering it, but then I saw your answer was already on point. Good job. Sep 29, 2018 at 18:12