6 ms·
How can he fit three-dimensional coordinates into a single 128-bit number? Seeing how he divides diameter, I assume he only took care of one axis. I'm curious
by guard-of-terra 16y ago
How can he fit three-dimensional coordinates into a single 128-bit number? Seeing how he divides diameter, I assume he only took care of one axis.
I'm curious how many bits do we need to address a point in an universe with reasonable accuracy.
- CapitalistCartr 16y agoWe'd need three axes to define a coördinate in space, four to include time. Given his estimation of the known Universe as 9.3e10 light years across, giving each axis 2^96 would yield an accuracy of about 1.1 kilometers, plenty enough for space navigation. Multiply that by the number of axes.
- rorrr 16y ago1.1 kilometers is not even close to being enough precision. That's way larger than your typical missile or a space ship. You can't deal with that kind of error and expect collision detection to work correctly.
- andos 16y agoIt will never be the case, fortunately, that humanity will have to navigate a missile or spaceship across the observable universe (or the galaxy) with fixed point or otherwise.
- jimktrains2 16y agoyay! someone else who uses diæresis marks:)
- rorrr 16y agoYou specify the accuracy you need. Let's say, 1 millimeter. (9.3e10 light years) / (0.001 meter) = 8.79 × 10^29 log2(8.79 × 10^29) = 99.471 So you need 100 bits to represent each coordinate at that precision.
- cmaggard 16y agoHe was indeed only specifying a single axis, just as you wouldn't use a single float to specify three axes.
- guard-of-terra 16y agoThe number of scalars to specify a point in space varies from one to twelve and probably more - depending on the terrain. For example, to point at objects reliably you need to factor their movement relative to gravity vector in. I can totally imagine using just one (long) scalar, too.
- qntm 16y agoThe interesting thing is that, as you get further and further from Earth or the Sun or the centre of the Milky Way, the level of precision which is even useful becomes less and less. What is one light year left or right for a quasar 13,000,000,000 light years away? Floats, then, behave entirely appropriately in this situation.