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Thread: JTL Physics Completley Off (fun yes, but darn it)
Sirpi wrote:
Good input, but to clarify a few things
1. alot of you are confusing Velocity/Speed with acceleration. The 'thrust' limits acceleration, not speed (until you get very high up, like half the speed of light, and then, speed is limited by mass if i remember correctly), unless, as mentioned above, your talking velocity as a funtion of time, which is of course limited. However, my main point was that I just wanna coast. So, I could have a 1lb thruster attached to a boulder and it would eventually reach a very high speed, even though it would take forever. Current Ion propulsion systems work like this. They have very low thrust, but nearly limitless power, so they can accelerate for a very very long time.
Speed and velocity are always functions of time. The only difference is that speed is the magnitude of velocity. It has no directional component, i.e. velocity = 10 m/s north.... speed = 10 m/s.
Velocity is not a direct function of mass. For example, drop two balls that are the same size(if they are not the same size, the larger ball will fall slower because of more friction) that weigh different amounts and they will fall at the same velocity at a rate equal to earth's gravitational force.
True, thrust is a function of acceleration, but it's also a function of velocity because acceleration is a function of velocity.
"Current Ion propulsion systems work like this. They have very low thrust, but nearly limitless power, so they can accelerate for a very very long time."
To accelerate for a very very long time, you need 1. an infinite source of energy and 2. the ability to produce increasing "thrust" or force for a very long time.
It is meters, not miles. Don't tell me you can dogfight with ships that's 600 miles from you.
Lilleth wrote:
And to the "meters" - I wondered first time too. But now I think it's "miles" - imagination is a good thing you know
Yours
A lot of misinformation concerning science going on around here and I blame GL for it. Yes, the physics in Star Wars are more akin to atmospheric physics, not space physics.
falsehoods:
1). Constant engine glow/thrust. Unless you are accelerating, engines should not expel propelent. There's no need to in space unless you're trying to overcome gravity. The original poster is correct in that at our current scale of operation, no practical limit on speed should exist. The reason there's a limit on speed as you approach the speed of light is because relative mass increases and in fact goes to infinity at C (the speed of light).
2) When thrust is cut, you stop. That is another case of bad physics. Once you reach your desired speed after accelerating with thrust, you should be able to cut the engines and coast, not stop! Fortunately in game it can be explained away by invoking the notion of counter thrust (which we don't see in the graphics, but can be assumed I guess).
3) Two objects dropped at the same time fall at the same velocity. That's not quite true. They fall at the same RATE (which means rate of acceleration) Let's take the actual experiment as performed by Astronaut David Scott on the moon when he dropped a hammer and a feather simultaneously. Both hit the surface of the moon at the same time. They fall at the same rate of acceleration, meaning their velocity changes with time. Velocity is not constant. Check out the Hammer and Feather video here.
Early in beta they had a more realistic physics model, but that was shot down. I fully understand why GL designed his ships this way. He needed to appeal to the masses. But since then we've become (I hope) a lot more sophisticated about space which is why virtaully all Space related movies and games have realistic space physics models today.
CerionSkydreamer wrote:
3) Two objects dropped at the same time fall at the same velocity. That's not quite true. They fall at the same RATE (which means rate of acceleration) Let's take the actual experiment as performed by Astronaut David Scott on the moon when he dropped a hammer and a feather simultaneously. Both hit the surface of the moon at the same time. They fall at the same rate of acceleration, meaning their velocity changes with time. Velocity is not constant. Check out the Hammer and Feather video here.
Velocity is also a rate. It's a measure of the rate of change of distance as a function of time. So within any given time period, both objects will have the same velocity.
And the velocity of these objects will eventually become constant..... it's called terminal velocity. This happens when the force of friction is equivalent to the object's weight. At this point there's no longer any acceleration and velocity is constant.
theres no laserfire in space
there cant be explosions in space.
the way you deaccelerate in jtl is out of this world. theres no friction in space, so whats the counter force thats slowing you down to 0? hell i dont see reverse rocket on the front of my x wing. do you?
Created by the Creator of the Universe.
S-1-l2-H-C wrote:
i got one for you.. if energy can neither be created nor destroyed, where did all this energy come from?
Message Edited by Amuro0079 on 11-14-2004 07:00 PM
Sirpi wrote:Want to know if there was a reason that physics were done the way they were in space.1. The only max speed you have is light (unless you coun't hyperspace/wormholes/warping etc). Ships would have a max ACCELERATION, not a max speed.2. There is no atmosphere, no medium, to slow a ship, so why cant we blast away, cut the burners, then coast (hmmm, Battlestar Galactica (the new one)has done it the best i've seen so far), or rotate around and blast our pursuers3. Targeting distance is in meters? If it takes my ship that long do fly 3000 meters i'd be better off in a space suit with a can of hairspray to propel meI realize some of these may be design issues, but I'd really like to know. Also, The 'X-Wing' series of games (God bless 'em) had the same problem. While totally entertaining, it was like your ship was a combination of car/plane. It really acted nothing like a ship in space, other than you being able to 'sit still' and rotate on your various axis.
If you want real physics in an online game wait for Elite online (yes its in the works along with Elite 4)
lnflux wrote:
also:
theres no laserfire in space
there cant be explosions in space.
the way you deaccelerate in jtl is out of this world. theres no friction in space, so whats the counter force thats slowing you down to 0? hell i dont see reverse rocket on the front of my x wing. do you?
Influx, I have to correct you there. "Laser-fire", is totally possible, lasers are used (for navigation and location finding) in space today, I think. Either way, laser is just light, light travels through space, so laser weapons in space are totally feasible. In fact, laser is just "Coherent light" (look it up), and the word "laser" and an acronym for "Light Amplitude Stimulated Emission & Radiation". Because the light is "coherent", then all of the little photons are in phase with each other. This is like pushinga child on a swing at the right moment. If your pushing is in phase with the swing then the child swings higher (amplitude of oscillation increases). Lasers do this with "stimulated emission", so it's kind of like a positive feedback effect directly at the source. Then becaue the photon's are in phase (constructive interference), and not deconstructively interfering, then the beam doesn't spread out, and we get the absolute straight laser beams that we're all familiar with today.
Explosions, well quite right oxygen based fires are not possible in space, since there is no oxygen atmosphere. However plasma fires are possible in a vacuum, so imagine that's what you're seeing when you see ships go boom. Having said, when you do see a ship go boom, it probably had a lot of oxygen inside already, and that willburn nicely!
You're welcome dude, nice to be able to put my physics master's to use at last
Sirpi wrote:
Thanks all, nice to know there are more than one or two geeks who share this world with me.
DaveG and Cerion, thanks for the posts btw. Youvoiced my main concerns more simple than I could after 20 gallons of coffee and zero sleep with none of my reference material with me (lesson learned, I'm bringing my schoolbooks to work from now on before I start spouting gibberish).
mafia-man wrote:
If you want real physics in an online game wait for Elite online (yes its in the works along with Elite 4)
Message Edited by DaveG on 11-14-2004 03:47 PM
CerionSkydreamer wrote:
/cries for science education
3) Two objects dropped at the same time fall at the same velocity. That's not quite true. They fall at the same RATE (which means rate of acceleration) Let's take the actual experiment as performed by Astronaut David Scott on the moon when he dropped a hammer and a feather simultaneously. Both hit the surface of the moon at the same time. They fall at the same rate of acceleration, meaning their velocity changes with time. Velocity is not constant. Check out the Hammer and Feather video here.
Early in beta they had a more realistic physics model, but that was shot down. I fully understand why GL designed his ships this way. He needed to appeal to the masses. But since then we've become (I hope) a lot more sophisticated about space which is why virtaully all Space related movies and games have realistic space physics models today.
Ouch, bad use of language on your third point there. You keep refering to the "rate of acceleration", which implies acceration is changing. In the case of David Scott, there is no "rate of accerlation", theacceleration is constant, and that rate is equal to the "acceleration due to gravity" of the moon (on earth, this value is g=9.81 m/s^2).
The only time you would have a "rate of acceleration" is when the force is a function of time, then there isa rate of change of acceleration because acceleration is a function of force. However, in call cases of dynamics with constant force (i.e. not a function of time), then acceleration is constant (for constant mass, typically the norm in non-relativistic models), and thus has no rate of change.
Apart from that, if anyone else is confused, then I suggest the rest of you take "Newton's Laws of motion" as required reading!
As for more sophisticated sci-fi, yeah totally!A really good example is most dog fights shown in "Babylon 5", particularly the StarFury fighters.
Message Edited by DaveG on 11-14-2004 08:10 AM