The Battle Room is near-zero gravity environment where war games are conducted. Inside the area are large obstacles called "stars." Soldiers use these stars as cover, and also for launching off of. Disabled soldiers will also collide with the stars.

Shouldn't the stars start drifting after a few collisions?

4 Answers 4


The Wiki speculates that stars are held in place magnetically.

I don't believe it is ever specifically stated, but I believe that the stars are most likely held in place by the same technology that allows the Commander's Hooks to function.

The Hooks allow the army commander to move freely throughout the Battle Room during practices, and also allows the commander to unfreeze the suits of his army members during practice.

The Hooks do not function during actual Battles, so the school administrators clearly have quite a bit of control over the technology.

In the movie, Graff is shown using using his Hook to move the students, bringing them from various free-floating positions within the zero-gravity area, to a formation hovering in front of him.

It isn't much of a stretch to imagine more powerful versions being used to position the stars, and then to hold them in place during a Battle.


The end of the first book indicates that the International Fleet salvaged and reverse engineered the technology for artificial gravity - and that the battle room(s) were a direct result of that technology. It can be inferred that the way stars are placed in the battle room is due to this technology.

However, exactly how artificial gravity works in the Enderverse is not something that I've come across in the books I've read.

  • 1
    I don't know if there's an explanation or not, but I do know that artificial gravity was one of the technologies obtained from the buggers, which, like the ansible, the humans may have been using without entirely understanding themselves.
    – Tomari7
    Jan 20, 2014 at 10:28
  • The book isn't about the technology, the only bit of tech that's explained at all is the molecular disruptor and that's because it's important in the final battle. May 18, 2022 at 2:42

The text specifically states that Ender has worked out that the Fleet have the ability to control gravity. Graff later states that this technology was reverse-engineered from the buggers.

[Eros] was the treasure trove. If they had known we would win that first war, they probably' would never have built this place. We learned gravity manipulation because they enhanced the gravity here.

The Hook, the Stars and even the battle arena couldn't function without this technology.

In keeping with the neo-fascist government depicted in the book, the secret of gravity manipulation (and even the fact that it's possible) has been kept secret from the general population;

They never tell you any more truth than they have to. But any kid with brains knows that there've been some changes in science since the days of old Mazer Rackham and the Victorious Fleet. Obviously we can now control gravity. Turn it on and off, change the direction, maybe reflect it-- I've thought of lots of neat things you could do with gravity weapons and gravity drives on starships. And think how starships could move near planets. Maybe tear big chunks out of them by reflecting the planet's own gravity back on itself, only from another direction, and focused down to a smaller point. But they say nothing.”


Local volumetric modifications to the electronically generated gravity fields

The semi-canonical The Technology of Ender's Game: Some Thoughts on How the Battle School and the Battle Room Might Function by Stephen Sywak goes into detail about how the Stars stayed in position.

Although this work was not written by Card, "it informed his thinking as he worked on the Shadow books and Ender in Exile".

The “Stars” were first developed with these land-based systems. The early models were approximately 1/4m to 1m per side, and were built in various geometric shapes such as spheres, tetrahedra, etc. As the realization that the best way to utilize the Battle Rooms grew from hand-to-hand training to the larger planetary and deepspace theaters, the Stars changed from their original, “personal” sized units to the large, gravity-suspended, padded cubes currently used. The majority of the Stars are approximately 3m on a side, and all possess recessed handholds on all six of their faces. These handholds allow soldiers to hold on to, push off from, and reorient themselves as they pass by or lock onto a Star.

The Stars are held in position by local volumetric modifications to the electronically generated gravity fields. Because the positions of the Stars are maintained by these pseudogravitational forces (as opposed to rigid structural connections), the force of a student/soldier landing on or bouncing off a Star—if unopposed—could cause it to change position within the Battle Room. Radiolinked position sensors within the Stars report their positions back to the room control computers fifty times/second, and the projected gravity field adjusts itself though servo-control electronics to maintain each Star’s position and orientation to within a highly accurate 5 millimeters (<0.1°). The Star’s large mass (nominally 500 to 1,000 kilograms) allows sufficient resistive forces to be generated by the electro-synthetic gravity to keep the Stars in position against the impact loads of multiple students.

Stars are stored within the walls of the Battle Rooms. Large padded panels unlock and swing into the Battle Room to provide access to sizeable storage regions behind.

The Authorized Ender Companion - The Technology of Ender's Game

  • Do you have a link to the source? I would like to read it. Sounds interesting.
    – iMerchant
    May 16, 2017 at 16:07
  • @iMerchant - I found it in The Authorized Ender Companion.
    – ibid
    May 16, 2017 at 16:08
  • @iMerchant - Looks like much of it is freely available through Google Books.
    – ibid
    May 16, 2017 at 16:12

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