suppose you are in a spacecraft, not an observer on earth, you start accelerating by using, lets say, antimater engines. the type of fuel is really not important as long as you don’t run out of fuel and antimater engines sounds way cool.
anyway you start accererating. now since all velocity is relitive at any given time you can say you are at 0 velocity even if you are traveling 100,000m/s faster then when you started. your acceleration rate should be the same, assuming same engine output and ignoring the loss of mass due to the propulsion system.
now what prevents you from simply accelerating to and past the 186,000 mi/sec ( = S.o.L.) past your speed you started at?
>> what prevents you from simply accelerating to and past the 186,000 mi/sec??
The fact that you do not have enough energy to get to the SoL. Do you know how much you would need?
AFAIK, nothing. The only limitation on space flight, science-fiction-wise, is the human life span. It might take you so long to get going faster than light that your human passengers would have died of old age long before that.
But then, I’m not a physicist, just a Trekkie.
if you could accelerate at about 1 g or 32 ft / sec, not only would you have artificial gravity but you would get to the S.o.L on about 1 yr
32 ft/s /s is appx 0.0064 mi/sec/sec so you speed would increase 0.0064 mi/sec every second, you would reach 186000 mi/sec in about 29,000,000 seconds or 8073 hrs or 336 days. so if that acceleration rate can be kept up, you would be at the S.o.L. in under 1 year.
Chronos, cleanup in GQ! Until he gets here, I’ll take a crack at this. As you accelerate towards c (186,252 mi/s, speed of light in a vacuum), you do two things: You gain mass and you lose length. At speeds very low compared to c, both of those are negligible. But as you get to .9c (90% of c) those effects have added up to the point where you are trying to accelerate a ship with near-infinite mass and near-zero length. It ain’t gonna happen. From your reference frame, nothing has changed except your engines have begun to give a lot less acceleration per unit of fuel. Soon you have stopped accelerating and no matter how much fuel you pour in you can’t accelerate. You have hit a very real wall. You either lay off the gas and coast for lightyears that fly by in months (or weeks, or even hours, depending on speed) from your frame of reference or you try to decelerate by pumping energy out the opposite direction.
[ed up to the point where you are trying to accelerate a ship with
near-infinite mass and near-zero length. It ain’t gonna happen. From your reference frame, nothing
has changed except your engines have begun to give a lot less acceleration per unit of fuel]
I don’t think so since velocity is relitive, your propulsion system with antimater engines is light (gamma radiation i think and a heck of a lot of it) leaving out the back of your spacecraft at the SoL, your headlights leave infrount of you at the SoL. you are effectively traveling at 0 mi/sec, there would be no reason that your mass should increase if you are on the ship
Derleth,
I don’t think you’d actually STOP accelerating, I think that your rate of acceleration would decrease, ** approaching** zero (becoming negligable), but it would only actually reach zero at the S.o.L. I think.
In one word, physics.
In the everyday world that we experience, we don’t see things going very fast. The intuitive model that we get about how physics works is actually a simplification of how things really work.
Of note:
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There is no absolute speed. Something can only have a velocity relative to some other thing.
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Speeds are not additive. At very slow speeds, relative to the speed of light, the difference between the real physics, and treating speeds as additive is so small as to be almost unmeasureable.
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Light in a vacuum moves at a constant speed, no matter what your frame of reference is. If you are moving 100,000 miles/sec. past me at the same time I shine a flashlight, and we each measure how fast the light is moving relative to ourselves, we each measure the same speed.
Because light will always be moving at the speed of light, relative to yourself, no matter how much you accellerate, you will never reach the speed of light, as sailor has said. Therefore, you will never go faster than the speed of light.
Maybe there is some way to “cheat”, to go faster than the speed of light. Maybe there’s something out there at the edge of special relativity that doesn’t behave exactly like the theory states, as special relativity did to Newtonian mechanics. But the world has done many, many, many experiments that verify the validity of special relativity.
If you’d like to know more, I recommend that you read a good book on physics. There are many out there; one I’ve been perusing lately has been Clifford Pickover’s “Time : A Traveler’s Guide”. It’s been pretty good so far, and doesn’t have any math more scary than square roots or fractions.
[ don’t think you’d actually STOP accelerating, I think that your rate of acceleration would
decrease, approaching zero (becoming negligable), but it would only actually reach zero at the
S.o.L. I think.]
this would apply to an outside observer not for people actually on the spacecraft. the mass would also increase to an outside observer but again, not to the people on the spacecraft
[2) Speeds are not additive. At very slow speeds, relative to the speed of light, the difference
between the real physics, and treating speeds as additive is so small as to be almost
unmeasureable. ]
not sure i understand this one
but your points are valid, but I don’t see how it would prevent you from going 186,000 mi/s faster then when you started. if an observer shot a laser at the spacecraft from behind, it would ‘appear’ to the people on the ship to come towards the ship at the SoL and if the laser missed, it would pass the ship and continue away at the Sol. the observer would ‘see’ the laser approach and pass the ship at the SoL.
and a little aside, why is my post count stuck at 269???
never mind that last one, I see that it is my total posts not the actual post number
The simplest answer is: it takes a certain amount of energy to accelerate by a set amount, say 1m/s. But the faster you go, the more energy it takes to attain that set amount of acceleration. As you get closer and closer to c, the energy it takes to accelerate goes up and up.
So, the energy it takes to accelerate asymptotically approaches infinity as you approach the speed of light. You can never go faster than c because there isn’t that much energy in the universe!
If you go past me at 50 mph, and throw a ball out at 75 mph, the ball will go past me at 125 mph. If you go past me at 50 mph and I throw a ball at 75 mph, it will go past you at 25 mph.
But, if you move past me at 50% of c (c = speed of light) and throw a ball out at 75% of c (pretend you’re a 24th & [sup]1[/sup]/[sub]2[/sub] century baseball pitcher) it will pass me at 91% of c, not 125% of c. And, if I throw the ball out at 75% of c, it will pass you at 40% of c, not 25% of c.
So, the guy is shooting light blasts across the bow of the ship, which is accelerating directly away from him. If the ship was going above 186,000 mi/s, the blasts would not be able to catch up to it; if it was able to go that fast for a long enough time, it would be able to catch up to a blast that had previously passed it.
But they will, and it won’t. To folks on the ship, the blasts will always be going 186,000 mi/s faster than the ship is, and will pass them going 186,000 mi/s faster than the speed it’s going. No matter how quickly it accelerates, or for how long. To the observer shooting across it, the ship will not accelerate at a constant speed. The closer the ship gets to the speed of light, the less quickly it will accelerate. The ship might get within 1% of the speed of light, from the shooter’s perspective, but to the occupants of the ship, they will always be 186,000 mi/s slower than light.
The math isn’t that tricky, but it isn’t what most people would expect. It’s a part of the universe that you don’t see normally, if at all, so it doesn’t seem like it would be true. But it is.
Well, you said it right there. In order to accelerate past c, you have had to define yourself as moving at 0 m/s. Very tricky of you, to be moving both at 0 m/s and 299787 km/s at the same time.
As you said, velocity is relative. It is impossible, within the boundaries of the universe that we know, for two objects to have a relative velocity greater than the spped of light. And light always has a relative velocity of c, even in the headlight beam of a car going 299000 km/s.
Because of this, if you could ride on the hood of a photon (not recommended, and illegal in 37 states), you would experience the fourth dimension as a point. All photons exist in the same time, and forward and backward in time mean nothing to them (which gives the interesting consequence that an anti-photon is exactly equivalent to a photon).
You might try an interesting book called In Search of Schrödinger’s Cat by John Gribbin. Fascinating stuff.
LL
Punoqllads said;
Not to be picky, but…
Everything that we see is light, which, by definition, travels at the SoL, which is very fast indeed!
But seriously…
Something has always bothered me about explanations of Relativity that I’ve read. They all suggest that if someone went on a space trip at near the speed of light and returned, that less time would have passed for the voyager than for the people left at home. For example; ten years might have passed for you but your twin brother, left behind on Earth, would be fifty or more years older.
But, if any inertial reference is as valid as any other, you could look at this trip as if you were still, not moving in space, and that the Earth left you at speeds approaching the SoL and eventually came back. In which case they are the ones who would have experienced relativistic time-dilation, and your twin on earth would have aged a mere ten years to your fifty.
Whazzup wit dat?
E d’Mann said:
You just stated the twin paradox. However it is a false paradox. The reason is that we aren’t dealing with pure inertial reference frames. The twin who travels needs to accelerate to near the speed of light, turn around, then decelerate to Earth’s inertial reference frame. This breaks the symmetry of the situation. You need to use general relativity to explain this fully. The twin who does the accelerating I believe will be the younger twin.
Are you all stupid?? If you were going the speed of light, time would stop. If you were going faster than the speed of light you would travel back in time. Time is a dimension, just like height, width, and depth. Time is chronological, and cannot be penetrated.
READ EINSTEIN’S WORKS!
Dr. Lao…
I still don’t really see the distinction, but since your response has at least triggered an inkling in my noggin, I will defer to your obvious qualifications.
(p.s. If you’re a real Phd. or sumpin’ check out my T.O.E. on my website and email me your criticisms (of which, I’m sure, there will be many.))
E d’Mann
Suppose your two twins are sitting in a space station. One takes off in his rocket at 1g acceleration. Now, the twin in the rocket can feel an acceleration, whereas his twin in the space station can’t. So the symmetry which would allow either twin to claim that they are stationary doesn’t exist. If they look back at each other through telescopes, one is floating around eating paste out of plastic bags, the other is working on his juggling technique. It isn’t hard to tell which one is accelerating!