Hard Science Help

[Vondy]

MAJOR EDIT: I did some of my own math and need to rephrase the question. At 1g it seems you would hit the speed of light in a year.

 

Need math brain help:

 

A ship travels to Tau Ceti (~11.9 Light Years Away), accelerating at .25g until it reaches roughly .3C, cruises, and then decelerates at the same rate to its target?

 

Questions:

 

1. How long would the acceleration/deceleration phases take?

2. How long would the total trip take?

3. How much time (time dilation) passes on Earth?

[Maur]

Re: Hard Science Help

 

All of these are just basic algebra equations.

 

1. How long would the acceleration/deceleration phases take?

 

Acceleration is fixed, so v = a*t, solve for t and you get 1.165 years to reach max speed of .3c

 

2. How long would the total trip take?

 

Trip time: Time = (Total distance - 2 * acceleration distance)/Max velocity

 

for a travel time of 39.5478 years.

 

3. How much time (time dilation) passes on Earth?

 

Earth suffers no time dilation from the accelerating ship, so about 40 years pass on Earth while the ship travels.

[Vondy]

Re: Hard Science Help

 

All of these are just basic algebra equations.

 

 

 

Acceleration is fixed, so v = a*t, solve for t and you get 1.165 years to reach max speed of .3c

 

 

 

Trip time: Time = (Total distance - 2 * acceleration distance)/Max velocity

 

for a travel time of 39.5478 years.

 

 

 

Earth suffers no time dilation from the accelerating ship, so about 40 years pass on Earth while the ship travels.

 

Thanks. That helps.

 

I was more concerned with potential time dilation effects on communication as I am assuming an ability to generate tiny wormholes for long enough periods to send super-dense quantum bursts of information through.

[McCoy]

Re: Hard Science Help

 

MAJOR EDIT: I did some of my own math and need to rephrase the question. At 1g it seems you would hit the speed of light in a year.

 

Need math brain help:

 

A ship travels to Tau Ceti (~11.9 Light Years Away), accelerating at .25g until it reaches roughly .3C, cruises, and then decelerates at the same rate to its target?

 

Questions:

 

1. How long would the acceleration/deceleration phases take?

2. How long would the total trip take?

3. How much time (time dilation) passes on Earth?

 

Thanks. That helps.

 

I was more concerned with potential time dilation effects on communication as I am assuming an ability to generate tiny wormholes for long enough periods to send super-dense quantum bursts of information through.

Since the peak speed is expressed as a fraction of c, the time dilation is 1/(SQR [1-.3]), or about 20%. For each hour that passes on the ship, an hour and 12 minutes will pass on Earth. Communications -wise, less distortion than a 33 1/3 album being played at 45 rpm or vice versa. The people on the ship will find ground control sounds like chipmonks, the people on the ground will hear the people on the ship t a l k i n g v e r y s l o w l y.

[Nyrath]

Re: Hard Science Help

 

MAJOR EDIT: I did some of my own math and need to rephrase the question. At 1g it seems you would hit the speed of light in a year.

 

Need math brain help:

 

A ship travels to Tau Ceti (~11.9 Light Years Away), accelerating at .25g until it reaches roughly .3C, cruises, and then decelerates at the same rate to its target?

 

Questions:

 

1. How long would the acceleration/deceleration phases take?

2. How long would the total trip take?

3. How much time (time dilation) passes on Earth?

 

Relativity doesn't become noticeable until you get over .5c, and it doesn't become really obnoxious until you are over .9c.

 

However, the equations are here for you to play with.

http://www.projectrho.com/rocket/rocket3aj.html#relativity

[Nyrath]

Re: Hard Science Help

 

Earth suffers no time dilation from the accelerating ship' date=' so about 40 years pass on Earth while the ship travels.[/quote']

Well, that turns out not to be the case. According to Relativity, everything is, well, relative. Time dilation is symmetric between two inertial observers, so one can say that the ship is accelerating and Earth stays still, or the ship is staying still and the Earth and the entire universe is accelerating in the opposite direction. Earth says that the people on the ship are slowing down due to time dilation, while the people on the ship say that Earth and its population are slowing down due to time dilation.

 

Relativity says that both are correct.

 

http://en.wikipedia.org/wiki/Time_dilation#Time_dilation_is_symmetric_between_two_inertial_observers

[McCoy]

Re: Hard Science Help

 

Well' date=' that turns out not to be the case. According to Relativity, everything is, well, [i']relative[/i]. Time dilation is symmetric between two inertial observers, so one can say that the ship is accelerating and Earth stays still, or the ship is staying still and the Earth and the entire universe is accelerating in the opposite direction. Earth says that the people on the ship are slowing down due to time dilation, while the people on the ship say that Earth and its population are slowing down due to time dilation.

 

Relativity says that both are correct.

 

http://en.wikipedia.org/wiki/Time_dilation#Time_dilation_is_symmetric_between_two_inertial_observers[emphasis added]

The ship accelerates and decellerates, therefore is not an inertial reference frame.

[Vondy]

Re: Hard Science Help

 

First, thank you all for your responses.

 

I found a good calculator for determining these things (will post the link when I get home). I fiddled with the numbers until I got a relatively ( ) reasonable result based on long-term low g acceleration to midpoint and then subsequent deceleration. A trip of ~20 years shipboard, resulted in ~24.5 years on Earth.

[Clonus]

Re: Hard Science Help

 

Thanks. That helps.

 

I was more concerned with potential time dilation effects on communication as I am assuming an ability to generate tiny wormholes for long enough periods to send super-dense quantum bursts of information through.

 

That's very problematic. FTL communication would send back into the past of whichever side was recieving the message or something.

[Nyrath]

Re: Hard Science Help

 

The ship accelerates and decellerates' date=' therefore is not an inertial reference frame.[/quote']

You have a good point there, judge. I stand corrected.

[Kristopher]

Re: Hard Science Help

 

That's very problematic. FTL communication would send back into the past of whichever side was recieving the message or something.

 

????

 

Into the past?

[Nyrath]

Re: Hard Science Help

 

That's very problematic. FTL communication would send back into the past of whichever side was recieving the message or something.

????

 

Into the past?

 

Einstein's relativity proves that FTL travel/communication is exactly the same thing as time travel/communication.

http://www.projectrho.com/rocket/rocket3v.html#causality

[theltemes]

Re: Hard Science Help

 

You have a good point there' date=' judge. I stand corrected.[/quote']

 

You could estimate the relativistic effects by choosing a small time interval, say an hour, and

 

1. Find the average velocity over that hour.

2. Calculate the relativistic time dialation over that hour.

3. Add up differentials over the acceleration period.

 

I bet an excel spreadsheet could handle this quite well. It's not as exactly what's going on, but from an engineer's perspective you get a "close enough" answer. It should provide some insight as to what's going on during the acceleration phases of the trip.

[Inu]

Re: Hard Science Help

 

????

 

Into the past?

Yah, I don't get it either, and to me it looks more like 'because I can make the graph do this, it is so in real life!' but it seems to be well-accepted by scientists, so I shrug and accept that I'm not always going to understand high-level mathematics and physics. ^_-

[Clonus]

Re: Hard Science Help

 

????

 

Into the past?

 

That's what the physicists tell me. They're all mad, though. Completely barmy.

[Comic]

Re: Hard Science Help

 

To be fair, at most you could go only a bit over 4 years into the past, and that would be after 20 year had passed for you, and .. uh.. I thought I had a point, but I just sent myself something from the future saying it was pretty pointless.

[Clonus]

Re: Hard Science Help

 

To be fair' date=' at most you could go only a bit over 4 years into the past, and that would be after 20 year had passed for you, and .. uh.. I thought I had a point, but I just sent myself something from the future saying it was pretty pointless.[/quote']

 

The problem is their answer to you would be heard eight years before you sent your message.

[Comic]

Re: Hard Science Help

 

There you go.

 

So if I had FTL communication, and could accelerate an FTL repeater to a sizeable fraction of the speed of light, I could send myself news from my own future, up to a certain period ahead depending on the limits of my technology.

 

Which, since it can't happen, I'm good with.

[eternal_sage]

Re: Hard Science Help

 

basically, for those not understanding the whole "in the past" thing, relativity states that time moves differently depending on velocity. in particular, time moves more slowly for a body the closer to the speed of light it gets (the larger the ratio to c is). this is called time dilation, and has been expirienced by human researchers (though only in very small quantities).

 

so, moving at c, a body will expirience no time at all (100% c = 0 T, if i remember correctly), and moving beyond c (assuming that is even possible, and thats a very big if) would in fact then reverse time for those expiriencing it.

 

this is believed to be true because, since General Relativity is such an awesome tool that has yet to be disproven (or even given a good shaking, at least on the cosmic scale. atomic scale is abit different, hence the need for a unified theory) then it must be assumed that what it predicts is likely to be the case. basically, it, so far, has been right in every case to the point it is accorded law status (if we still did such things), so there is no reason to doubt its hypothesis about the effects of FTL.

 

also note that the closer to c you get the more mass you have (requiring more force to continue acceleration, and making it harder to maneuver), and if i remember correctly, the energy neccessary to move a mass from .999999999999999% of c to c is infinite, and the mass of said object at c is also infinite (again, i could be wrong, its been 10 years or so since physics, so the details are fuzzy).

[Vondy]

Re: Hard Science Help

 

As I understand it - and I'm a layman so correct me if I'm wrong - no one has gone into the past. Instead, one group of people travelled through time faster than another group of people for X years, which puts them at different points on the temporal road. The question is, can you call back in relation to where you are, or can they call forward in relation to where they are, and if so - are their limitations or odd-effects (like McCoy's suggestion of records playing at different speeds)?

 

Personally, I think we have a limited understanding of time as a phenomenon and scientists, like philosophers, need to suck it up and admit "we don't know jack and all our theorizing about possible and impossible is the product of limited minds." We think in a linear, three-dimensional way, but time and space are four-dimensional. We don't understand how that fourth dimension interacts with the other three. It may be it doesn't behave the way we want it to (meaning: in accordance with our current understanding).

 

Until we shoot someone out there are relativistic speeds, have them create a wormhole and send information back through it, we won't know. At the same time, according to current understanding, what would happen?

[SteveZilla]

Re: Hard Science Help

 

Personally, I think that time travel is impossible, because of the following thoughts:

 

1. Man Invents Time Machine -- both are both made out of matter contained within the universe.

2. Man uses Time Machine and travels into the past.

3. When Man arrives, the universe now has over 100% of the mass of the universe.

 

A similar reason would IMO prevent travel into the future (meaning you don't occupy space-time continuously from start to end of trip). For the period between "leaving" and "arriving", the universe has less than 100% of the mass of the universe.

[theltemes]

Re: Hard Science Help

 

basically, for those not understanding the whole "in the past" thing, relativity states that time moves differently depending on velocity. in particular, time moves more slowly for a body the closer to the speed of light it gets (the larger the ratio to c is). this is called time dilation, and has been expirienced by human researchers (though only in very small quantities).

 

It's all relative, baby.

 

The person moving near c experiences no sensation of time being different - he/she observes that the rest of the universe's time has sped up. Likewise, an observer of the really fast moving person would say that their time is moving at the "normal" rate, and that the person moving near c has almost no change in time. It still takes a person moving near c a little over a year to travel one light year to the outside observer, but to the person in the craft the journey is nearly instantaneous because of the relativistic length contraction of space.

[Maur]

Re: Hard Science Help

 

Both high velocity (relative to C) and large gravity generate time differences. So things without mass should experience no sense of time which seems to pan out. Photons are timeless and have no mass and move at C in the medium of space.

[SteveZilla]

Re: Hard Science Help

 

Both high velocity (relative to C) and large gravity generate time differences. So things without mass should experience no sense of time which seems to pan out. Photons are timeless and have no mass and move at C in the medium of space.

 

But Photons have (are) energy. And energy and mass are equivalent (E=MC^2). So don't they have "effective" or "equivalent" mass?

[eternal_sage]

Re: Hard Science Help

 

Von D-Man: you are correct, and you have to understand that good scientists have the opinion that relativity may be completely wrong, and just conviently happens to correlate. it is a theory, and nothing more, the product of limited brains trying to encompass infinity, as it were. i did not mean to sound that this is 100% true, just that it seems to us to be, based on what we've thus seen.

 

theltemes: that's what i was trying to get at, thank you for being more eloquent!

 

Maur: not sure on all that, but mass has nothing to do with gravity, weight does.

 

SteveZilla: both very interesting thoughts, really.

 

so, as to what would actually happen, it would be dopplershift, i imagine. i don't think it would actually help speed things up, just strech them out. but i think first of all, we need to define what exactly is a "wormhole" and how does it work? is it the old "blackhole-whitehole" pair, a "tear" in spacetime, hyper gravity spacetime folds, what?