Traveling at the speed of light and time dilation

[phinds]

would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?

Communication signals would experience a predictable and continuous down-shift in frequency during the acceleration and then become constantly downshifted while coasting but all that can be compensated for. The biggest issue, I think, would be signal power but you can hand-wave your way out of that pretty easily.

 

[DHF]

Thank you very much Phinds, I was keeping that in mind when designing the ship for the book. when the ship is traveling it employ a shielded dome on the front of the ship and shielded panels covering the sides. while in transit the ship looks like a mushroom with an octagon shaped stem. when the ship arrives it ejects the dome and shielded panels to reduce mass and make travel around the solar system more fuel efficient. each of the eight sides of the ship will extend solar panels to provide auxiliary energy for the ship and crew. power will also come from a second fusion reactor that will utilize the fuel that wasn't spent for propulsion.

Though the front of the ship is protected, the rest of the hull is more vulnerable. while in transit, cosmic rays penetrate the less shielded area of the hull. part of the crew's programming is effected by interaction with said cosmic rays and this leads to uncomfortable thoughts popping up during their mission, like home sickness.

 

[Ryan_m_b]

Phinds is right of course, you'll need to take into account shielding.

OK that works for me. so the only cap on speed is the amount of fuel you can carry. So if they wanted to go .12c its simply a matter of: can you carry enough fuel to accelerate to that speed and still have enough fuel to decelerate?

Not quite, you missed the point of maximum acceleration. If you want to go to speed X in a given time frame you have to have enough fuel to accelerate to it and slow down and a powerful enough engine.

Some back of the envelop calculations (feel free to check this by using the rocket equation yourself, it's not my field by a long way):

If we assume the craft masses 1000 tonnes (small but I'm handwaving here) and the exhaust velocity of a fusion rocket is 500kmps (taking a rough average from these estimates)) then to get to .12c would require ~8*10³⁷ kg of fuel (much more than the mass of the solar system). And that's just to reach the speed! Not even to slow down again.

(You have to bump exhaust velocity way up before the numbers become reasonable. At 10,000kps the fuel mass would be 40 thousand tonnes of fuel. At 100,000kps it's just 440 tonnes but that implies you have an exhaust velocity of 1/3rd the speed of light! At that speed you'd have to pump in ~5e15 joules per kilo of fuel, 300x global energy usage.)

How much thrust you produce is worked out by your mass flow x exhaust velocity. Essentially how much mass exits the back of the ship (assuming it does so perfectly collimated). For the 500kmps ship to accelerate at 1G would take a mass flow of 1.6e33 kgps, again more than the amount of mass in the solar system.

So you'll have to do some playing with the numbers to decide on a reasonable exhaust velocity, a reasonable payload mass and a reasonable mass flow. Once you have that you can begin to work out what acceleration and top speed is feasible.

would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?

I imagine that should be relatively easy to compensate for, it's just Doppler shift.

Thanks for the help :)

No worries.

 

[DHF]

then to get to .12c would require ~8*1037 kg of fuel (much more than the mass of the solar system). And that's just to reach the speed! Not even to slow down again..

augh! damn you reality with all your numbers!

the heck with it, I am just going to put them in a trash can and give them a good shove. they should get there in a few million years, they are androids, they won't care.

there, mass and fuel and all that nonsense solved ;)

or I might just have a dragon take them there. that should help me avoid any further calculations :D

 

[Ryan_m_b]

augh! damn you reality with all your numbers!

Lol! IMO it's entirely possible to write hard SF to get round this, generally there just has to be one piece of super-technology proposed.

the heck with it, I am just going to put them in a trash can and give them a good shove. they should get there in a few million years, they are androids, they won't care.

To be fair that isn't a bad idea. I've read stories before where androids traveled interstellar at very slow speeds. It might have taken them millennia but that wasn't a problem because the crew just cranked their clock rate right down as a form of stasis (speeding back up regularly to conduct maintenance) and anyone not essential was kept backed up on a computer ready to download into a body constructed on arrival.

 

[Ryan_m_b]

I just remembered another way (from an SF story) you could tap dance past this problem and keep it within the realm of acceptabley hard science fiction. You could propose that the ship is a type of Starwisp, essentially a giant solar sail, and give it a small payload of around 1 tonne. The ship could be accelerated by laser arrays orbiting the sun, when it comes to slowing down it could release a large part of its sail which doubles up as a mirror bouncing the beam back to the small payload. The payload itself could be some hypothetically super-compact fab lab, a number of small robots, a computer and some source of energy. AI could be downloaded into the robots and sent out to set up the fab lab, gather resources and build infrastructure. It might take a very long time but assuming no catastrophe (a big assumption admittedly) those initial machines could build up factories for mass producing stored copies of their crew.

 

[DHF]

I know: The ship will be powered by unobtainium. there, done!

 

[Ryan_m_b]

You could switch from fusion to some sort of antimatter rocket. Getting back to the energy requirement of 5e15 joules per kilo for an exhaust velocity of 1e8mps: annihilating a kilo of matter gives 9e16 joules (18 times more than the energy requirement). If you suggest that antimatter can be made in bulk then you could up your fuel requirement by 5% and have half of that be antimatter. That extra 5% of matter and antimatter could be annihilated to produce the energy to accelerate the fuel but you'd need a hand wavy answer to suggest how.

 

[DHF]

I had initially shied away from antimatter because I felt that it might realistically be thousands of years before we can use it in a practical manner. however the more we crunch numbers, I just don't think Fusion will do the job if I want the crew to get there in a human lifetime. Ironically I move away from having a living crew to escape the confines of human life spans but then I realized the mission would still need to operate within human life spans because humans funded the mission and I don't think the government or a private company woul spend hundreds of billions of dollars on a venture that would take centuries to unfold.

so getting back to anti-matter. I suppose if it is the only way I can make it work I will go that route, but I feel that we would sooner perfect proton - proton fusion first. Speaking of which, it is not as powerful as matter/anti-matter but if the characters had access to such perfect fusion, what kind of speeds an acceleration could I expect?

 

[Deleted member 498135]

It's impossible for objects with mass to attain the speed of light. You're question is therefore unanswerable because it essentially asks "if we ignore the laws of physics what do the laws of physical say?"

Very true... Too bad :( if it was real, hypothetically speaking, would time stop?

 

[Travis_King]

This is why many SF writers who want to lean toward the hard side of SF tend to:
a) Stay within the Solar System
b) Stay within some distant star system which was seeded long ago by a sub-light speed ship
c) Go the colony sized ship route
d) Use space-time warping as their mode of travel rather than actual ship velocity. I've seen several instances of this type where you don't even have to explain how; the main characters don't know how it works, they just know that someone in their world knows and created the drive.

 

[DHF]

This is why many SF writers who want to lean toward the hard side of SF tend to:
d) Use space-time warping as their mode of travel rather than actual ship velocity. I've seen several instances of this type where you don't even have to explain how; the main characters don't know how it works, they just know that someone in their world knows and created the drive.

This is very true, an I can appreciate that as I have learned during my research just how ridiculously hard it is to travel between stars. Even granting the characters mastery over fusion we would still have them *Crawling* to the nearest star and doing so only at a ludicrous expenditure of fuel.

Truth is even if we set the tale 1000 years in the future and handwavinly gave the characters an unlimited power source the size an mass of a marble... they would still be limited just under the speed of light and thus travel from star to star would still take years, ruling out any sort of federation or swashbuckling through the galaxy.

As such my tale focuses on the next generation of explorers, a humanity that has made travel through their own star system practical. But for all their technology, for all the awesome power of Fusion and Anti-matter energy drives... getting to the nearest star is as hard for them as the moon was for the Apollo program.

 

[Enigman]

Well, if you are reaching for hand-wavium already and this is your general story line:

I got around the whole keeping the crew alive thing by ditching a living crew. The current crew will be androids with AIs based on human astronauts back on Earth. In this way the life support can be ditched and the mass of the ship can be further reduced because they won't have to worry about a return flight. Once the ship arrives, the crew will be stationed in the Alpha Centuri Star system permanently, intending to explore and run experiments while transmitting the results back home. The drama will arrive when certain members of the crew start to realize that their programming has changed during the flight, they come to the conclusion that they are self aware and tensions arise when members of the crew question the idea of being abandoned light years from home.

then-
http://mysite.verizon.net/res148h4j/javascript/script_starship.html
at 10000000 G for 4.22 light years distance time on board is about 1 min 47 sec

or you could use:

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)
with best time as 133 years to alpha centauri.

or other versions of nuke-propulsions:

Unlike Daedalus' (see the next quote) closed-cycle fusion engine, Longshot would use a long-lived nuclear fission reactor for power. Initially generating 300 kilowatts, the reactor would power a number of lasers in the engine that would be used to ignite inertial confinement fusion similar to that in Daedalus. The main design difference is that Daedalus would rely on the fusion reaction being able to power the ship as well, whereas in Longshot the internal reactor would provide this power.

The reactor would also be used to power a laser for communications back to Earth, with a maximum power of 250 kilowatts. For most of the journey this would be used at a much lower power for sending data about the interstellar medium, but during the flyby the main engine section would be discarded and the entire power capacity dedicated to communications at about 1 kilobit per second.

Longshot would have a mass of 396 metric tons (873,000 lb) at the start of the mission, including 264 tonnes of Helium-3/Deuterium pellet fuel/propellant. The active mission payload, which includes the fission reactor but not the discarded main propulsion section, would have a mass of around 30 tonnes.

A difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star while the higher speed Daedalus would do a one shot fly-by lasting a comparatively short time.

The journey to Alpha Centauri B orbit would take about 100 years, at an average velocity of approximately 13411 km/s, about 4.5% the speed of light, and another 4.39 years would be necessary for the data to reach Earth

http://en.wikipedia.org/wiki/Project_Longshot

Alan Bond led a team of scientists and engineers who proposed using a fusion rocket to reach Barnard's Star, only 5.9 light years away. The trip was estimated to take 50 years, but the design was required to be flexible enough that it could be sent to any of a number of other target stars.
[..]
Daedalus would be propelled by a fusion rocket using pellets of deuterium/helium-3 mix that would be ignited in the reaction chamber by inertial confinement using electron beams. The electron beam system would be powered by a set of induction coils tapping energy from the plasma exhaust stream. 250 pellets would be detonated per second, and the resulting plasma would be directed by a magnetic nozzle. The computed burn-up fraction for the fusion fuels was 0.175 and 0.133 for the First & Second stages, producing exhaust velocities of 10,600 km/s and 9,210 km/s, respectively. Due to the scarcity of helium-3 it was to be mined from the atmosphere of Jupiter via large hot-air balloon supported robotic factories over a 20 year period.

The second stage would have two 5-meter optical telescopes and two 20-meter radio telescopes. About 25 years after launch these telescopes would begin examining the area around Barnard's Star to learn more about any accompanying planets. This information would be sent back to Earth, using the 40-meter diameter second stage engine bell as a communications dish, and targets of interest would be selected. Since the spacecraft would not decelerate upon reaching Barnard's Star, Daedalus would carry 18 autonomous sub-probes that would be launched between 7.2 and 1.8 years before the main craft entered the target system. These sub-probes would be propelled by nuclear-powered ion drives and carry cameras, spectrometers, and other sensory equipment. They would fly past their targets, still traveling at 12% of the speed of light, and transmit their findings back to the Daedalus second stage mothership for relay back to Earth.

The ship's payload bay containing its sub-probes, telescopes, and other equipment would be protected from the interstellar medium during transit by a beryllium disk up to 7 mm thick and weighing up to 50 tonnes. This erosion shield would be made from beryllium due to its lightness and high latent heat of vaporisation. Larger obstacles that might be encountered while passing through the target system would be dispersed by an artificially generated cloud of particles, ejected by support vehicles called dust bugs, some 200 km ahead of the vehicle. The spacecraft would carry a number of robot "wardens" capable of autonomously repairing damage or malfunctions.

Overall length: 190 metres
Propellant mass first stage: 46,000 tonnes
Propellant mass second stage: 4,000 tonnes
First stage empty mass at staging: 1,690 tonnes
Second stage mass at cruise speed: 980 tonnes
Engine burn time first stage: 2.05 years
Engine burn time second stage: 1.76 years
Thrust first stage: 7,540,000 Newtons
Thrust second stage: 663,000 Newtons
Engine exhaust velocity: 10,600,000 m/s & 9,210,000 m/s
Payload mass: 450 tonnes

http://en.wikipedia.org/wiki/Project_Daedalus

 

[DHF]

Thanks Enigman, I appreciate the references. I tempting as it is, I am trying to wave my hands as little as possible, this is difficult because I am Italian but I will try none the less.

I am trying to strike a balance, I would like to keep the propulsion and fuel ratio withing believable limits but for the sake of the plot I would like to keep their trip within a 20-40 year window.

The current design I have on the drawing board is designed to go one way to the nearest star and has no considerations for food or life support because the crew will not need either, even still the ship is little more then a latticework cylinder covered in fuel tanks. not a very exciting look but exciting and realistic seem mutually exclusive.

 

[Enigman]

Er...only the first one was hand-waving and meant as a pun, the nuclear propulsion examples are real scientific models.
Project Longshot fits best with your needs:
Project Longshot was a conceptual design for an interstellar spacecraft , an unmanned probe intended to fly to and enter orbit around Alpha Centauri B, and that would be powered by nuclear pulse propulsion.

Developed by the US Naval Academy and NASA from 1987 to 1988, Longshot was designed to be built at Space Station Freedom, the precursor to the existing International Space Station.
http://en.wikipedia.org/wiki/Project_Longshot

 

[DHF]

No no I wasnt dismissing the Longshot and Deadalus designs, I have heard of them and I fully appreciated the material you provided. my reference to handwavium was strictly addressing your first suggestion with 10000000G propulsion. I mean sure if I was setting the tale 10,000 years in the future and portable pocket stars were as common as cellphones then what the heck why not :)

Actually the very earliest concept for the book was total hanwavium. it was set at a much more distant point and the ship was straight out of the thickest sci-fi mud, but the more I developed it the more I realized that I wanted something that felt like like the adventures of real astronauts with just enough Tech to make interstellar travel plausible. There will be no space dragons, no evil world conquers with cosmic cubes... The Drama comes from detailing how difficult their journey was and how much they had to sacrifice to make it happen, and then regret, wondering if they sacrificed too much.

 

[lendav_rott]

Mass effect relays from Mass effect franchise can propel a vessel faster than the speed of light :D :D :D

 

[Infinite/Zero]

A thing will be always greater than a thing(not infinity).
It is possible.

 

[DHF]

Everything I have read advocates putting the engine in front of the ship and pulling the bulk of the ship rather then pushing it in order to reduce the amount of mass the engines have to move. Personally I dislike all of the designs I have seen to that end and I am trying to find alternatives. Two possibilities:

My first Idea was to build the engines and fuel tanks as a self contained unit, The Cargo and crew quarters will be a separate ship that is pushed in front of the Engines by electro magnets. Does this design have any feasibility? will pushing the bulk by magnets relieve any of the burden of mass on the engines or will the mass be the same even though there is no physical connection between the engines and the cargo and crew vessel?

The other idea was to build it Tie Fighter style, with the Bulk of the ship being built flush with the Engines so that there is nothing being pushed in front of the engines or being pulled behind them. would this be more fuel efficient then pushing the bulk of the ship in front of the engines?

Do either of these ideas have any merit?

 

[Ryan_m_b]

Everything I have read advocates putting the engine in front of the ship and pulling the bulk of the ship rather then pushing it in order to reduce the amount of mass the engines have to move.

Could you give examples of what you mean by this? No matter where you put the engines the mass, and therefore the force needed, will be exactly the same

My first Idea was to build the engines and fuel tanks as a self contained unit, The Cargo and crew quarters will be a separate ship that is pushed in front of the Engines by electro magnets. Does this design have any feasibility? will pushing the bulk by magnets relieve any of the burden of mass on the engines or will the mass be the same even though there is no physical connection between the engines and the cargo and crew vessel?

Doesn't matter how the ship is held together; metal, magnets or magic the mass is the same and so the engines have to do the same amount of work.

The other idea was to build it Tie Fighter style, with the Bulk of the ship being built flush with the Engines so that there is nothing being pushed in front of the engines or being pulled behind them. would this be more fuel efficient then pushing the bulk of the ship in front of the engines?

Nope, see above. Long story short there aint no such thing as a free lunch. At the end of the day accelerating X mass to Y velocity is going to require the same amount of energy no matter how you assemble the parts (all else being equal).

 

[phinds]

A thing will be always greater than a thing(not infinity).
It is possible.

That is very awkwardly stated, but I think you mean that if X is not infinite there is always something bigger than X, yes? If so, then yes, that's pretty much self-evident. Am I missing your point?

 

[micromass]

That is very awkwardly stated, but I think you mean that if X is not infinite there is always something bigger than X, yes? If so, then yes, that's pretty much self-evident. Am I missing your point?

I think he suggests that if $X$ is a finite speed, then there must be a speed bigger than $X$. So he suggests that since $c$ is finite, there must be some object that goes faster than $c$. This is wrong, of course.

 

[phinds]

I think he suggests that if $X$ is a finite speed, then there must be a speed bigger than $X$. So he suggests that since $c$ is finite, there must be some object that goes faster than $c$. This is wrong, of course.

Ah ... good point. It did not occur to me that he might be that far out of touch with physics.

 

[DHF]

Could you give examples of what you mean by this? No matter where you put the engines the mass, and therefore the force needed, will be exactly the same
.

I was referring to Dr. Charles Pellegrino's Valkyrie design. He claims that putting the engine in front of the ship will allow the ship to be less massive. He claims that it would be easier for the engines to pull a mass rather then push it.

 

[Bandersnatch]

@ Ryan:
The mass reduction is due to structural differences in ship design(i.e., shielding, beams), rather than some new physics.
http://en.wikipedia.org/wiki/Project_Valkyrie

 

[Ryan_m_b]

I was referring to Dr. Charles Pellegrino's Valkyrie design. He claims that putting the engine in front of the ship will allow the ship to be less massive. He claims that it would be easier for the engines to pull a mass rather then push it.

From reading the wiki it seems clear that the proposed advantage is that by dragging the crew compartment on a long tether large amounts of radiation shielding can be left out (which would be needed in any antimatter rocket). This doesn't mean that engine placement matters in terms of how good the engine is, it's just an approach to minimising what other things you have to take with you.

 

[DHF]

From reading the wiki it seems clear that the proposed advantage is that by dragging the crew compartment on a long tether large amounts of radiation shielding can be left out (which would be needed in any antimatter rocket). This doesn't mean that engine placement matters in terms of how good the engine is, it's just an approach to minimizing what other things you have to take with you.

ok fair enough. That being the case I don't think it will make a difference for me. Since I am using a non living crew I shouldn't have to worry about radiation as much. And to keep the mass of the ship down I will be waving my hands a little and will be using pollyunobtanium. :D

 

[Ryan_m_b]

ok fair enough. That being the case I don't think it will make a difference for me. Since I am using a non living crew I shouldn't have to worry about radiation as much. And to keep the mass of the ship down I will be waving my hands a little and will be using pollyunobtanium. :D

I wouldn't be so sure about not worrying about radiation. Radiation induced bit rot would probably damage your machines as well.

 

[DHF]

Fair enough so they would be radiation tolerant but not radiation proof. If I am waving my hands for a as of yet un-invented super light material for the ship hull then I can just take the Valkyrie design in reverse, instead of having a long tether trailing behind the engines, I could protect the crew from radiation by distancing them rather then packing many tones of shielding. if for example the ship were 2 kilometers long and the crew compartment was near the front, that would keep them away from the engines and radiation with minimal shielding. with the story taking place over two hundred years from now I don't think a lot of hand waving is needed to assumed the ship is constructed of some advanced decedent of Graphine or a type of the like. Thus letting the ship be incredibly long yet light. I didn't picture a thick battle ship design either, I was imagining the ship would have a honeycomb latticework structure with only the crew an cargo compartments being solid.

 

[Infinite/Zero]

Am I missing your point?

No, you are right

 

[Ryan_m_b]

No, you are right

Velocity doesn't work like that, sure there might be a number higher but it is not possible for objects with mass to reach the speed of light, nor for anything to exceed it.

 

[DHF]

Ok I did some calculations on how much fuel I would need but I have never done these calculations before so I would be appreciative if anyone could tell me if I am on the right track or if I am totally missing something.

Dry Mass =1000 Metric Tons
Engine output = 644.93 TJ/kg
Desired speed = 11.91% c
Fuel needed = 1000 Metric tons

This is assuming the ship will accelerate at .10G until it reaches 11.9c then it will coast for several decades then decelerate at .10G

The Engine output is assuming a proton to proton Fusion reactor. It will require a small Anti-matter catalyst but I am not adding those figures in at this time. I just wanted to make sure I was on the right track for my mass ratio calculations.

 

[Ryan_m_b]

What are you using to work that out? When you say "644.93 TJ/kg" are you referring to the kinetic energy you'll be imparting per kg? If so I make that an exhaust velocity of ~0.12C. Using the ideal rocket equation with:

1e6kg payload
3.6e7mps exhaust velocity
3.6e7mps desired velocity

I get 1.77e6kg of fuel. To slow down again I get 6.7e6kg. In other words your craft would have to carry 870 grams of fuel for every 1kg of payload. For an initial acceleration of .1g you would have to expend 25 grams of fuel per second.

All seems reasonable until you consider that your craft is producing as much energy per second as the entire Earth.

 

[DHF]

Yes the 644.93 TJ/kg refers to the kinetic energy imparted per kg. and yes it is a mind numbing amount of energy, clearly ridiculous by today's standards. Even still, I am trying to keep the specs of the ship fairly modest and we still are looking at insane amounts of energy.

To get the figures I posed I used The figures posted for fusion reactions on this site: http://www.projectrho.com/public_html/rocket/fusionfuel.php and then I used the Relativistic Star Ship Calculator to calculate the mount of energy I would need to move the ship to the desired speed.

I added a shield in front of the ship to take care of dust and micrometeorite impacts. however in order to decelerate the ship needs to flip around and fire its engines for over a year before it enters the Alpha Centuri system. There is no shield on the back of the ship so how does the ship protect itself from micro impacts for the year during it's deceleration? will the thrust from the engines clear the way? will debris still get through?

Another aspect of the ships's designs are the radiators. instead of simple heat sinks that dumped waste heat into space I wanted to turn them into generators that converted the heat into electrical energy to power the ships systems this way the fusion reactors could devote all their energy to propulsion. Is it conceivable to convert all the heat into electrical energy or would the generators still need to dump waste heat once the electrical energy was produced?

 

[DHF]

In my last post I asked if the thrust from the engines would clear the way, I meant exhaust not thrust. duh.

 

[LitleBang]

There is no speed limit. As far as the crew of a ship with an unlimited supply of fuel is concerned they can accelerate up to c and beyond. A trip from Earth to Andromeda for instance. They can accelerate up to c, as viewed by a stationary observer, for one month and decelerate for one month for a total travel time of two months. Remember that their clocks stop at c. Obviously they can never reach c as viewed by a stationary observer but as far as the crew is concerned they did reach c and beyond.

 

[phinds]

There is no speed limit. As far as the crew of a ship with an unlimited supply of fuel is concerned they can accelerate up to c and beyond. A trip from Earth to Andromeda for instance. They can accelerate up to c, as viewed by a stationary observer, for one month and decelerate for one month for a total travel time of two months. Remember that their clocks stop at c. Obviously they can never reach c as viewed by a stationary observer but as far as the crew is concerned they did reach c and beyond.

Uh, relative to WHAT is it that you think they reached c? There is no absolute motion so it has to be relative to SOMETHING and since you even realize yourself that they won't reach c according to a "starionary observer" (meaningless concept though that is), then what DO they reach c relative to?

Also, why do you think their clocks stop? That certainly isn't true. Their clocks just keep right on ticking at one second per second.

 

[DHF]

Phinds has already mentioned why that isn't accurate but its a moot point really because it doesn't have any real world applications, even in a fictional story. You would never have an unlimited amount of fuel and fuel alone is not the sole determining factor, you would need engines with enough power to accelerate you to that speed. In this thread we touched on the absolute ludicrous amounts of power you would need to reach even 12% of c and at a crawl of an acceleration.

This thread has given me a real appreciation for just how challenging interstellar travel can be when you play within the laws of physics. Its why nearly all Sci Fi tales with space travel jettison said laws. Otherwise the Enterprise wouldn't even have made it to Alpha Centuri by the time the series was over and they would have spent several Jupiters in fuel mass to get that far.

 

[Drakkith]

There is no speed limit. As far as the crew of a ship with an unlimited supply of fuel is concerned they can accelerate up to c and beyond. A trip from Earth to Andromeda for instance. They can accelerate up to c, as viewed by a stationary observer, for one month and decelerate for one month for a total travel time of two months. Remember that their clocks stop at c. Obviously they can never reach c as viewed by a stationary observer but as far as the crew is concerned they did reach c and beyond.

Not true. You have forgotten the effects of length contraction. To the observers on board the spaceship, the distance between them and the Andromeda Galaxy contracts so that they can reach their destination without ever reaching c or beyond.

 

[Paintjunkie]

gamma...?

 

[Drakkith]

gamma...?

Can you elaborate on your question? And possibly quote the section of whatever post it's related to?

 

[Paintjunkie]

sorry I don't have a question its more a GAMMA! but maybe my question is... mathematically isn't that formula that gives us gamma the reason why we can go faster than the speed of light?

 

[Drakkith]

sorry I don't have a question its more a GAMMA! but maybe my question is... mathematically isn't that formula that gives us gamma the reason why we can go faster than the speed of light?

I believe so. Also, please don't post "noise". Make sure your posts are relevant to the thread.

 

[frish]

Hello DHFPeople read about Relativity in the newspapers, memorize the 'mc square', hear strange tales about objects getting heavier when they move at close to the speed of light, then bring themselves to ask on Internet forums:
"What does it look like when one is moving with a speed close to the speed of light?" in the same way they might ask in long distance global phone call,
What's the weather down there? Is it hot?;"

Well, it is not so, as explained in more details here:http://www.iei.info/knol/pf/3trm10yysobsi-15-relativity-str-and-gtr-in-three-k.php