# Tennis on the moon, possible?

sonhouse
Posers and Puzzles 04 Jun '11 01:48
1. sonhouse
Fast and Curious
04 Jun '11 01:48
So it's a couple hundred years from now, cities on the moon, in caves or domes, whatever, but pressurized with good breathable air. You want to play tennis, but can you in 1/6 Earth gravity? The court in Earthy tennis is 78 feet long, the net 3 feet high in the center, an inch or so higher at the edges.

Could you play a decent game on the same sized court on the moon? It seems to me if you just made the thing longer to account for the shallow drops a ball would make on the moon would just give the opponent that much more time to get to the ball.

What would be an acceptable set of dimensions for the court, the serve box, the doubles line, net height and total length?

Would putting english on the ball make it curve more in 1/6 gravity or would the path be unaffected?
2. 06 Jun '11 06:04
OK, here it goes. Taking into consideration only the gravity and not any difference in density/friction of air on moon surface, I think that, ...
... tennis can be played
... current dimensions wouldn't be enough for a decent game since to put the ball into opponent's court players would have to be closer to the net
... the court should be 6 times longer AND 6 times wider (so 36 times the area)
... spinning the ball should make it curve for a longer time hence theoretically enabling a boomerang shot
... players would have to cover a wider area (obviously) but they also will have a longer time to breathe after they shoot so I don't know if they will tire quicker or slower.

Of course one could also lower the height of the net (not sure about the ratio, but shouldn't be as much as 6 times) and keep everything else the same. This should also enable an enjoyable game.
3. sonhouse
Fast and Curious
06 Jun '11 15:16
Originally posted by talerin
OK, here it goes. Taking into consideration only the gravity and not any difference in density/friction of air on moon surface, I think that, ...
... tennis can be played
... current dimensions wouldn't be enough for a decent game since to put the ball into opponent's court players would have to be closer to the net
... the court should be 6 times longer ...[text shortened]... ch as 6 times) and keep everything else the same. This should also enable an enjoyable game.
The only thing I see about a bigger tennis court is the longer time the ball would be in the air. As it is now, you get maybe one second to react to a fast ball coming at you. If the court was 6X bigger, you would have what would look like 6 seconds or so before the ball gets to you, enough time to go off court, get a squirt of water, come back and then hit it backðŸ™‚

That is what Earthy gravity gives us, fast games. So how can we have fast games on the moon if the size was so large. Remember, 6 times 78 is a court 468 feet long. At that distance, I don't think you could even SEE the ball unless you were using binoculars.

A football field is about 360 feet so that would make it will over 100 feet longer. Think about how that would effect the game of tennis.
4. AThousandYoung
All My Soldiers...
06 Jun '11 19:12
Another possibility would be a more massive ball.
5. sonhouse
Fast and Curious
07 Jun '11 12:29
Originally posted by AThousandYoung
Another possibility would be a more massive ball.
Yeah, that could flyðŸ™‚
6. sonhouse
Fast and Curious
07 Jun '11 21:401 edit
Originally posted by sonhouse
Yeah, that could flyðŸ™‚
A more massive ball would go further I would think, now that I thunk it. More MV Squared and all that.

It seems to me one solution would be to have the ball have a metallic center, not too heavy, and the court to have a nice fat magnetic field.

Looks to me like that would put things back in balance.
7. 10 Jun '11 07:18
Originally posted by AThousandYoung
Another possibility would be a more massive ball.
Actually mass is irrelevant here because g is acceleration and is not related no mass.
8. 10 Jun '11 07:51
Another problem is how the players run around. They probably couldn't run normally because there woudn't be enough traction and might have to do bounding leaps like astronauts on the moon.
9. sonhouse
Fast and Curious
10 Jun '11 13:351 edit
Originally posted by iamatiger
Another problem is how the players run around. They probably couldn't run normally because there woudn't be enough traction and might have to do bounding leaps like astronauts on the moon.
That could be mitigated by having a kind of sticky pad surface that could imitate gravity by holding on the the shoes worn a bit to increase friction and such. Still, if the court was 400 + feet long, you would do a LOT of running to chase down balls. I guess the lower gravity would reduce the amount of energy used to cover such distances but it would still be a lot of running!

I like the idea of a magnetically responsive ball and a vertically oriented magnetic field to change the flight characteristics of the ball to match on the moon what is the gravity of earth.

Seems to me the only practical way to have the game anything like the earthy version.

If that were possible, the size of the court would be the same as on Earth.

Combine that with magnetically responsive boots, you might have a game close to earth version.
10. AThousandYoung
All My Soldiers...
10 Jun '11 22:30
A more massive ball will move slower with the same racket strike, giving gravity more time to act on it.

A shuffling motion would probably be necessary to move without bounding upwards.
11. sonhouse
Fast and Curious
10 Jun '11 23:15
Originally posted by AThousandYoung
A more massive ball will move slower with the same racket strike, giving gravity more time to act on it.

A shuffling motion would probably be necessary to move without bounding upwards.
I gather you haven't seen Rafa or Roger hit the ball lately?
12. 14 Jun '11 06:51
You wouldn't be able to trot off the court get a drink and still have time to return the ball. In 1/6 gravity a step would translate into a bound, a very slow bound. In order to accelerate to a sprint you need at least four or five steps to come up to speed. How much speed can you generate with only one step? Movements while exaggerated would appear to the spectator to be in slow motion. Good point about being able to spot the ball though. Maybe if it were a luminescent ball you could easily see it.
13. sonhouse
Fast and Curious
14 Jun '11 13:58
Originally posted by 4nonprophet
You wouldn't be able to trot off the court get a drink and still have time to return the ball. In 1/6 gravity a step would translate into a bound, a very slow bound. In order to accelerate to a sprint you need at least four or five steps to come up to speed. How much speed can you generate with only one step? Movements while exaggerated would appear to t ...[text shortened]... eing able to spot the ball though. Maybe if it were a luminescent ball you could easily see it.
Or VR glasses that with software defining the ball position. I somewhat disagree about the slow bounce, the apollo astronauts bounced around on the moon, seemed to go pretty fast. Maybe it would be some kind of wheelchair sport with the chair tied to a giant etch-a-sketch kind of mechanism which whips you around the court to get the balls. I still like the magnetic field concept to simulate gravity at least as far as the ball is concerned, that would allow a standard sized court.
14. wolfgang59
14 Jun '11 22:50
Originally posted by talerin
Actually mass is irrelevant here because g is acceleration and is not related no mass.
The players will be hitting the ball with the same force as on Earth so mass IS relevant.
15. sonhouse
Fast and Curious
15 Jun '11 14:322 edits
Originally posted by wolfgang59
The players will be hitting the ball with the same force as on Earth so mass IS relevant.
Of course it's related to mass. If it were freefalling in a gravity field, all masses would react pretty much the same, but we are talking about a tennis ball getting whacked by a racket which is a kinetic acceleration, just like a bullet in a gun, if the same powder charge in two bullets goes off, one bullet is lighter than the other, the smaller mass will accelerate faster, the heavy one will be slower, have less acceleration. Same with the tennis ball. The acceleration comes in the extremely brief time it is in contact with the racket where the strings are stretched back a bit and then snaps the ball forward. If the ball is heavier, it will not be going as fast when it leaves the racket. You have to picture that effect in extreme slowmo. When the ball makes contact with the ground, there is a further deceleration and reacceleration that changes the trajectory of the ball, the energy of that change came from the racket and the human swinging it.

Found a school exam piece covering this exact problem:
http://cyclotron.tamu.edu/gagliardi/P218_Exams/FEx_F09_key.pdf

Well it is several problems, only the first one is of interest, and it tells how many meters the ball is in contact with the racket during the swing. It can be used to find out the acceleration though. 29 ms to get to 73 meters per second. 29 ms inverted is about 34, times 73= about 2500, which is 2500 meters/sec/sec divide by 9.8 gives an acceleration of about 250 g's!