Space & Speed of light..

[phaxmohdem]

The in the weightless ness of space if you throw an item say a baseball at a speed of 2 meters per second, it would continue on indefinatley at the same speed/trajectory, (well until it hit something or was pulled off course by a gravitational field or something) right?

So assuming now we had built a rocket/propulsion device capable of accelerating a given craft continuously at a rate of 50 meters/sec(m/s), and assuming that the speed of light is: 299,792,458 m/s (Google Info), Theoretically the craft would reach the speed of light in a shade over 69 days would it not? (Theory of Relativity be damned for this example 😛 )

Also re: Theory of relativity, it is said the mass increases as an object approaches the speed of light... It has been tested on earth I've read, but has any one done any experiments on this in the vacuum of space yet?

Sorry for all this space question crap, I've just always been curious, especially after long burning Ion engines started coming out if it was possible to reach teh speed of light using a long term continuously accelerating engine.

 

[Gamingphreek]

No that wouldn't quite work. You would need a rocket that would burn continuously and keep giving more propulsion for 69 days. So not only would you need something capable of producing more thrust than is already being put out, but you also need millions of gallons of fuel to support this.

Additionally, remember that once you reach light speed you become pure energy. It is, at this point, theoretically impossible because entering lightspeed (assuming we could reach it) would give us infinite mass, and we would infinite energy; effectively killing us.

Also your mass shouldn't change, your weight (mass with respect to gravity) will change.

Im only in 12th grade physics so i probably have something wrong in that explanation. At any rate, you probably would have gotten better responses in the Highly Technical forum.

-Kevin

 

[Cattlegod]

the faster something gets it requires more energy to accelerate. i will make a couple graphs and post them for you.

 

[Whoozyerdaddy]

I think you answered your own question there...

As you approach the spped of light the object the engine is pushing will gain mass, thus slowing the rate of acceleration. So first off... It'll take longer than 69 days. Eventually the object being pushed will be so massive that all the engine can do is maintain speed.

That's the way I remember it from high school anyway.

 

[91TTZ]

Originally posted by: Gamingphreek


Also your mass shouldn't change, your weight (mass with respect to gravity) will change.

I think this is incorrect. It's your mass that increases as you near the speed of light.

 

[Atomicus]

OP, it is true in what you're analying the situation purely on Newtonian theory.

Based on Newton's law, F = m*a, in an ideal vacuum with no resistance to the object, by applying a constant F, the acceleration will in theory be constant as well. In conjunction with Einstein's E=mc^2, as you approach the speed of light, mass approaches infinity. And to balance F = m*a, acceleration will approach 0 (or if you prefer 1 * 10^-infinity). In conclusion? There's a threshold at which your acceleration will drop to almost nothing as you approach light speed and the only way to go faster is to put in the same amount of force as your mass increase.

I'm no physics major, but my reasoning is the same as Whoozyerdaddy's.

 

[Cattlegod]

graph.JPG

there you go, per my other post.

 

[Gamingphreek]

Originally posted by: 91TTZ

Originally posted by: Gamingphreek


Also your mass shouldn't change, your weight (mass with respect to gravity) will change.

I think this is incorrect. It's your mass that increases as you near the speed of light.

Yeah, i was hesitant of putting that there, because i learned it your way also. But isn't Mass, the ammount of matter within an object, we aren't gaining more matter the faster we go. Correct me if i am wrong, we aren't gaining mass, it just requires more and more energy to move us which gives the impression of greater mass until energy reaches infinity, as a result the mass is also infinity.

-Kevin

 

[edro]

You would need an ever increasing amount of energy... clear up to infinity.

 

[George P Burdell]

In theory: Your mass will tend to infinity as speed tends to c, which implies that your acceleration will tend to zero.

Basically you won't be able to maintain that acceleration at higher speeds, so you won't be approaching c, ever.

 

[Atomicus]

Originally posted by: George P Burdell
In theory: Your mass will tend to infinity as speed tends to c, which implies that your acceleration will tend to zero.

Basically you won't be able to maintain that acceleration at higher speeds, so you won't be approaching c, ever.

Thx for reading the postsfrom above, Capt. Obvious. :heart:

 

[phaxmohdem]

So in a perfect vaccuum, our little vessel is cruising along, as it gets faster and faster (assuming no increase in propulsion output is added) the rocket will start to lose acceleration until a point where it is no longer gaining any more velocity. (Due to the increase in mass)... Now if at that point you shut down the thruster completely, would the vessel actually start decelerating like a car does when you let off the gas peddal, or would it maintain the same constant speed it is traveling at since it is in space?

 

[mercanucaribe]

Here's my question about speed of light.. Supposedly it takes increasing amount of energy the closer you get to the speed of light.. but what is that speed relative to? No motion in the universe is absolute, so how can you absolutely require more energy the faster you are going?

 

[Atomicus]

Originally posted by: mercanucaribe
Here's my question about speed of light.. Supposedly it takes increasing amount of energy the closer you get to the speed of light.. but what is that speed relative to? No motion in the universe is absolute, so how can you absolutely require more energy the faster you are going?

I hope you're not getting into a parallax debate here.... don't think about speed in terms of relative motion. It is just length over time.

As for your second question, sounds like a philosophical inquiry rather than scientific.