FTL Travel vs Wormhole Travel: Some Questions


Homebrew and House Rules

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Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
ShallowHammer wrote:

I came up with a FTL technology that I felt was interesting. Instead of just traveling through space, you also modify the speed at which you're traveling through time. So for example, relative to earth, in normal speeds (sublight) you travel at 1 sec/sec (I know this changes as you go faster, but bear with me). Then at ftl you're traveling at 10 sec/sec relative to earth. so by the time you've traveled through 10 second at whatever sublight speed, you've effectively gone FTL.

F. M. Busby in "All These Earths" called what you're talking about "Skip Drive". the ship would accelerate to about .7c and then would travel using Skip Factors that would "skip" it's appearances in quantised space-time. thus creatin a mulitplier based on Skip Factor. Skip Factor 1 being no multiplication, 2 being 10x, 3 being 100x and so on.

The only downside is that at Skip Factors 4 or higher, you'd run the risks of skipping off your universe's track altogether and wind up in a parallel universe, with no practical way of return because of the random nature of the "skip".


LazarX wrote:
Goth Guru wrote:
In the book Crystal Singer, certain gifted individuals were able to tune crystals so the signal put into one came out the other. Distance was not relevant. They also tuned crystals that created warp fields. The crystal singers had crystals in their flesh are were supposed to be sterile, but that might just be a literary device. The subspace radio would have no tuner, just a series of buttons for selecting the crystal.
Ah yes.. Crystal Singer... a classic example of fantasy and magic wearing sci-fi trappings.

As was Dragonriders of Pern, by the same author.

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

Go to here.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Goth Guru wrote:
LazarX wrote:
Goth Guru wrote:
In the book Crystal Singer, certain gifted individuals were able to tune crystals so the signal put into one came out the other. Distance was not relevant. They also tuned crystals that created warp fields. The crystal singers had crystals in their flesh are were supposed to be sterile, but that might just be a literary device. The subspace radio would have no tuner, just a series of buttons for selecting the crystal.
Ah yes.. Crystal Singer... a classic example of fantasy and magic wearing sci-fi trappings.

As was Dragonriders of Pern, by the same author.

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

Go to here.

I wasn't really looking to start a war with Anne McCaffrey's fans by directly naming her, but yeah.


Not being hostile, and I only read the first book. Sorry if I seemed touchy.


Aelryinth wrote:

It's also VERY similar to what a Bergenholm does (inertialess drive). You are effectively creating momentum while ignoring inertia.

So, if you can find some way to replicate this effect, you've got a reactionless drive. Still, you're limited by Einstein's Wall, as you still can't get your atoms to hit light speed.

But then you have an inertialess drive in your setting. Those violate conservation of energy in a big way. You don't want to violate conservation of energy. When you're working on a small scale in a single reference frame with a GM vetted spell list it's not too bad, but when you get into space you get large relative velocities and it's <voice="cheesy gameshow announcer">welcome to planet cracking on a budget</voice>.


^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.


LazarX wrote:
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

Actually physicists are seriously researching the speed with which gravity effects propagate. One observational research suggested gravity speed of between 0.8 and 1.2 light speed but the results could have been explained by different effects taking place as well.

If the gravity had no "speed" it would mean that any change to mass also causes immediate transfer of information everywhere within the measurable gravity field of that mass, breaking the light speed barrier.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Drejk wrote:
LazarX wrote:
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

Actually physicists are seriously researching the speed with which gravity effects propagate. One observational research suggested gravity speed of between 0.8 and 1.2 light speed but the results could have been explained by different effects taking place as well.

If the gravity had no "speed" it would mean that any change to mass also causes immediate transfer of information everywhere within the measurable gravity field of that mass, breaking the light speed barrier.

You've obviously never heard of "Spooky Action At a Distance".

You also don't realise that the light speed "barrier" only refers to acceleration for the most part. There's nothing preventing space itself from receding faster than light speed. When that happens of course, that space and what's contained within it is no longer part of our observable universe.

The logical objection that many physicists raise against FTL travel is the causality argument, that you'd observe a ship arriving before you'd observe it leaving.


UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?


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LazarX wrote:
Drejk wrote:
LazarX wrote:
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

Actually physicists are seriously researching the speed with which gravity effects propagate. One observational research suggested gravity speed of between 0.8 and 1.2 light speed but the results could have been explained by different effects taking place as well.

If the gravity had no "speed" it would mean that any change to mass also causes immediate transfer of information everywhere within the measurable gravity field of that mass, breaking the light speed barrier.

You've obviously never heard of "Spooky Action At a Distance".

You also don't realise that the light speed "barrier" only refers to acceleration for the most part. There's nothing preventing space itself from receding faster than light speed. When that happens of course, that space and what's contained within it is no longer part of our observable universe.

The logical objection that many physicists raise against FTL travel is the causality argument, that you'd observe a ship arriving before you'd observe it leaving.

But physicists do debate the speed of gravity. It's not clear yet how fast that curvature of spacetime propagates. It's not necessarily forbidden by relativity for it to be instantaneous, but that doesn't mean that it is.


If you shine your flashlight with or against the Earth's spin, the light speed stays the same. This is because everything is measured relative to light speed. In a plane, above the Earth, going with all spins, Earth, Solar System, Galaxy, ect. you could go faster than light shined in the opposite direction. This is how Biggles time traveled.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
thejeff wrote:
UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?

Actually you can wreak havoc on planets by simply hitting them with a ship going close to the speed of light. relativistic mass coupled with near C speed is easy enough to cause an extinction event. In fact that's the premise of one Robert Forward novel which points out the inherent threat posed by even near light speed travel. If you do this at a speed fast enough, there's no defense against this trick, other than putting a barrier at the right place and the right time. The one weakness on this tactic is that you can't turn on a dime and the pilots on board or the remote controllers have an equal lack of opportunity to react to that kind of trap.


I actually don't quite know the science behind FTL drives wrecking planets. So I'm curious. What makes an inertialess drive so good at planet cracking? Also, why can't one use FTL near a planet? I've seen that used as a limitation before but never actually understood why.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Odraude wrote:
I actually don't quite know the science behind FTL drives wrecking planets. So I'm curious. What makes an inertialess drive so good at planet cracking? Also, why can't one use FTL near a planet? I've seen that used as a limitation before but never actually understood why.

There's no science or math behind inertialess or FTL drives so there's no answer for that.

For the STL example I quoted, it's simply a matter of plain old kinetic energy.. force being mass times velocity squared. Relative mass being heightened by relativistic effects.

It doesn't take much.. if you're by Arizona you can see the results of a 300 or so foot rock hitting the planet at a mere 20 miles per second or so. Just do the math and scale it up appropriately.


LazarX wrote:
thejeff wrote:
UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?

Actually you can wreak havoc on planets by simply hitting them with a ship going close to the speed of light. relativistic mass coupled with near C speed is easy enough to cause an extinction event. In fact that's the premise of one Robert Forward novel which points out the inherent threat posed by even near light speed travel. If you do this at a speed fast enough, there's no defense against this trick, other than putting a barrier at the right place and the right time. The one weakness on this tactic is that you can't turn on a dime and the pilots on board or the remote controllers have an equal lack of opportunity to react to that kind of trap.

Of course you can. But you can't do that by hitting them with an inertialess ship going close to (or above) the speed of light. Because relativistic mass is irrelevant if there's no inertia. It just stops. Instantly. Without the slightest shock.


Odraude wrote:
I actually don't quite know the science behind FTL drives wrecking planets. So I'm curious. What makes an inertialess drive so good at planet cracking? Also, why can't one use FTL near a planet? I've seen that used as a limitation before but never actually understood why.

Generally for reasons of plot. Any actual science behind it mostly just handwaving around the occasional bit of theory.

But it's a convenient way to make ships have to slow down at a reasonable distance so they can be intercepted and you can have real space battles rather than just hitting planets with FTL ships.


i can see we have a few Masters of the Universe here.
I suggest you go with Bistromathic Drive it is great.


thejeff wrote:
UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?

You turn off the inertialess drive and lose velocity, eh? With respect to what reference frame? If it's the nearest gravity well you can still set up nearly unlimited potential energy by killing your inertia between periapsis and apoapsis and leaving it off between apoapsis and periapsis. You wind up at the edge of the stellar sphere of influence. Then you flip your orbital direction contrary to your target for dirt cheap and dive in at stellar escape velocity adding the targets orbital velocity with full inertia. Then you rearrange some continents.

And that's the reference frame condition that makes things hardest.

It doesn't take all that much mass to wreck a planet when moving at stellar escape velocity either. KE=mV^2 after all.

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LazarX wrote:
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

mmm. I'm referring to something like this: If earth suddenly pops out of existence, and you're a light year away, how long before you could tell it wasn't there by observing the change in gravity?

That's the speed of gravity. If it's instantly possible to tell, then we have a speed of gravity. If it's not...time to measure!

The CRystal Singer is a story built around a single SF item - the ansiple (a McGuffin name for any device allowing instantaneous communication across vast distances). McAffrey is going more into psionics then magic for the attunement process (who knew perfect pitch could be so valuable?), but this 'impossible' thing is what keeps space viable in that story. The ansiple in this story are the crystals the singers cut.

I'm aware of the dangers of energy build up from relativistic speeds and stuff. But a Bergenholm drive harvesting vibrational speed gets around that since inertia is not a factor. You also put in a limiting factor, so the vibrational force is less and less as it enters other energy fields.
Note that there is no acceleration buildup of energy in this method, because your atoms are already vibrating at massive speed...you're just aiming it in one direction. So, you're shifting the direction, not the speed, and there's no energy accumulated that isn't already there. So, instantaneous redirection of velocity is actually possible!...you just can't do it when you're close to big things very easily.

As for power requirements, it's harvesting the vibrational speed of atoms, and simply aligning their natural velocities, so there's no need for extra energy input. It's tapping the energy that makes up what a person IS, i.e. the dance of electrons.

ON the website listed above (seriously, check it out, it's EXCELLENT...needs more Warhammer 40k, however), they give an excellent example of an attack by relativistic weapons. Literally wipes out humanity, there's no way to stop it.

The Killing Star is the name of the source novel.

Lensmen is more fun. Because you don't have inertia, you can exceed lightspeed. They power everything first by converting iron into energy, and then drawing on the background cosmic force of the universe. They bring in planets from other dimensions moving at multiples of the speed of light, which when they hit our universe promptly explode with force enough to take out solar systems. They turn the entire output of a sun into a laser beam that can cook planets. They smash a planet between two other planets used as weapons.

The Lensman series is the inspiration for every command and control center in existence today, and space opera at its grandest.

The Skylark series is also like this, scaling up even faster, but not as easy to find in print.

Does anyone happen to know if the Skylark series is online somewhere? I managed to read the first book a LONG time ago, so I know about atomic copper and salt...but I never read the last two books.

==Aelryinth

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Atarlost wrote:
thejeff wrote:
UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?

You turn off the inertialess drive and lose velocity, eh? With respect to what reference frame? If it's the nearest gravity well you can still set up nearly unlimited potential energy by killing your inertia between periapsis and apoapsis and leaving it off between apoapsis and periapsis. You wind up at the edge of the stellar sphere of influence. Then you flip your orbital direction contrary to your target for dirt cheap and dive in at stellar escape velocity adding the targets orbital velocity with full inertia. Then you rearrange some continents.

And that's the reference frame condition that makes things hardest.

It doesn't take all that much mass to wreck a planet when moving at stellar escape velocity either. KE=mV^2 after all.

Flipping off your Lensman Bergenholm results in the return of your previous inertia, subject to whatever conditions it was in. This results in you spinning away in a random direction, since the inertia is programmed to go in 'that direction', and the whole structure of the ship has moved and shifted and you've no way to know what direction that is actually going to be at this point. You end up having to regain control of inertia through normal means, so nobody comes out of inertia close to planets, for example. They have no control.

Or, you return to 'normal' at 0 inertia, as all your atoms set to '0' and are promptly harmonize to the nearest greater body of mass as the reference frame as they return to normal.

So you'd ram into a planet inertialess, turn off the drive, and your atoms would promptly take up the inertia and velocity of the surrounding vibrational atoms, and nothing happens of note.

It would be this tendency to keep harmonizing to the surrounding energy fields of mass which would restrict your insystem velocity. Your atoms want to move with the solar wind, not against it. Or rotate the planet, not ram into it. Move with the gravity field, hum along the magnetosphere, etc.

The stronger the external influence, the less internal speed you can use, until basically you're just back to using a gravity drive to do what you want insystem or near bodies of mass. You could flip the drive 'on' and 'off' to perform a braking maneuver close to an object, basically putting you into a perfect parallel to it, which would be great for stopping and being able to turn...but movement itself within such a zone would devolve back down to more normal physics because of nearby mass.

Interdiction zones could easily be set up to cover massive areas that force harmonization and stop the whole tactic from working. Its just a gravity field, after all, and those can be immense. Even a magnetosphere works if you can tweak it...the sun's magnetosphere extends twice as far out as Pluto, as I recall.

==Aelryinth

RPG Superstar 2012 Top 16

thejeff wrote:
LazarX wrote:
thejeff wrote:
UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?

Actually you can wreak havoc on planets by simply hitting them with a ship going close to the speed of light. relativistic mass coupled with near C speed is easy enough to cause an extinction event. In fact that's the premise of one Robert Forward novel which points out the inherent threat posed by even near light speed travel. If you do this at a speed fast enough, there's no defense against this trick, other than putting a barrier at the right place and the right time. The one weakness on this tactic is that you can't turn on a dime and the pilots on board or the remote controllers have an equal lack of opportunity to react to that kind of trap.
Of course you can. But you can't do that by hitting them with an inertialess ship going close to (or above) the speed of light. Because relativistic mass is...

Which is a key maneuverability feature for space battles in Lensmen! You can't even damage an inertialess enemy unless you can hold him tight in a tractor beam so the stuff you're throwing at him doesn't just push him away.

==Aelryinth


Atarlost wrote:
thejeff wrote:
UnArcaneElection wrote:

^Depends upon whether you really violated conservation of energy, or just moved yourself faster with a relatively small amount of energy by reducing your inertia. If the latter is the case, if you crash, you don't make any bigger crater than if you had the same drive on but with the reduced inertia feature turned off. Although you do make it a lot sooner.

As long as you can only apply your inertialess drive to relatively small objects you should be ok.

The trick with breaking planets with an inertialess drive isn't going really fast and hitting something - you're inertialess and when you hit something you stop. Instantly and without shock. And generally when you turn off the drive you go back to your velocity from before you turned on the drive, not your current velocity.

The trick is to take a planet, put inertialess drives on it and move it so it will smash your target when you turn them off. Slowly, but with much force. Or surround your target with planets with the necessary initial momentum, so even if it's inertialess it can't slip away.

Why yes, I have been rereading Lensmen. Why do you ask?

You turn off the inertialess drive and lose velocity, eh? With respect to what reference frame? If it's the nearest gravity well you can still set up nearly unlimited potential energy by killing your inertia between periapsis and apoapsis and leaving it off between apoapsis and periapsis. You wind up at the edge of the stellar sphere of influence. Then you flip your orbital direction contrary to your target for dirt cheap and dive in at stellar escape velocity adding the targets orbital velocity with full inertia. Then you rearrange some continents.

And that's the reference frame condition that makes things hardest.

It doesn't take all that much mass to wreck a planet when moving at stellar escape velocity either. KE=mV^2 after all.

In the classic Lensmen Bergenholm inertialess drive, which is the only place I've ever seen it, you don't "lose velocity" when you turn it off, you retain the inertia and velocity you had before you turned it on. You can't play the tricks you're suggesting.

It's hard to talk about what velocity you really have due to relativity, but it could be phrased as "the velocity you had when you turned on the drive relative to the thing you're concerned about hitting when you turn it off".
In order to land on a planet, you need to be able to match your speed to it, without using your inertialess drive.
But it's still hard to get to serious planet cracking relative velocities. You essentially have to do that with real normal acceleration. Much easier to make a big (asteroid, moon or planet big) mass inertialess, move it into place, turn the inertia back on and just let it impact to do your damage.


Aelryinth wrote:
Does anyone happen to know if the Skylark series is online somewhere? I managed to read the first book a LONG time ago, so I know about atomic copper and salt...but I never read the last two books.

The first two are on Gutenberg.

I'm not sure why only those two are available. They all seem available on Amazon in various used editions, at least some of them cheaply.


Odraude wrote:
I actually don't quite know the science behind FTL drives wrecking planets. So I'm curious. What makes an inertialess drive so good at planet cracking? Also, why can't one use FTL near a planet? I've seen that used as a limitation before but never actually understood why.

The basis of the science:

Kinetic energy = mass * velocity^2

If you can get an object moving very very fast, it has a lot of kinetic energy. This is the basic principle behind, say, a bullet: it's not big, but it's fast.

Similarly, a ship is not (usually) all that big compared to a planet, but it's very, very, very fast. At the speeds we're talking, it's literally so fast it breaks physics.

And when you hit something while moving that fast, you deliver a lot of kinetic energy at once. It's very possible to crack a planet open like an egg in this way; some asteroids do it and they're much slower.

FTL near a planet depends entirely on the technobabble behind the FTL. Typically it has to do with gravity wells. Something about the pull of gravity adversely affects FTL, which depending on the setting can render it dangerous, suicidal, or outright impossible.

But that depends entirely on your method of FTL and whatever pseudoscience you choose. I would generally say that you're wiser to use such a rule, because otherwise yes, genocide is downright easy (it's easy in space anyway, as all you need is a big rock, but that at least requires some kind of resources).

RPG Superstar 2012 Top 16

I have a question for the physics guys here.

I was reading on the website there that only lasers in the visible light spectra would be usable on earth because of the atomosphere, the air would literally absorb gamma and UV rays.

So, I was wondering about the viability of high-spectra energies as lasers.

Basically, is a 10 Gigawatt Infrared laser just as dangerous as a yellow laser or a blue laser or a UV laser or a Gamma ray laser of the same wattage? In short, if I put an identical amount of energy into each form of laser, are they all equally lethal assuming they reach their target?

I always wondered what would happen if you could take a given amount of visible light and break the Unified Field Theory, transform it all into microwaves, and get several zillion times as much microwave energy as white light energy, or some such.

==Aelryinth


The energy you would need to make a gamma Ray laser is not the same as for a common red laser pen.
I dont undestand how the atsmophere should absorb some but not others.
And i am not really a Physics guy.


Aelryinth wrote:
LazarX wrote:
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

mmm. I'm referring to something like this: If earth suddenly pops out of existence, and you're a light year away, how long before you could tell it wasn't there by observing the change in gravity?

That's the speed of gravity. If it's instantly possible to tell, then we have a speed of gravity. If it's not...time to measure!

The CRystal Singer is a story built around a single SF item - the ansiple (a McGuffin name for any device allowing instantaneous communication across vast distances). McAffrey is going more into psionics then magic for the attunement process (who knew perfect pitch could be so valuable?), but this 'impossible' thing is what keeps space viable in that story. The ansiple in this story are the crystals the singers cut.

I'm aware of the dangers of energy build up from relativistic speeds and stuff. But a Bergenholm drive harvesting vibrational speed gets around that since inertia is not a factor. You also put in a limiting factor, so the vibrational force is less and less as it enters other energy fields.
Note that there is no acceleration buildup of energy in this method, because your atoms are already vibrating at massive speed...you're just aiming it in one direction. So, you're shifting the direction, not the speed, and there's no energy accumulated that isn't already there. So, instantaneous redirection of velocity is actually possible!...you just can't do it when you're close to big things very easily.

As for power requirements, it's harvesting the vibrational speed of atoms, and simply aligning their natural velocities, so there's no need for extra energy input. It's tapping the energy that makes up what a person IS, i.e. the dance of electrons.

ON the website listed above (seriously, check it out, it's...

I think I missed the website you linked. Can yuo link it again please?

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Atarlost wrote:
This is really not the place to get rules advice for a SF setting. Try Winchell Chung's site. In particular, pay attention to the implications of FTL.

It's this website here. A great find!

==Aelryinth

RPG Superstar 2012 Top 16

Cap. Darling wrote:

The energy you would need to make a gamma Ray laser is not the same as for a common red laser pen.

I dont undestand how the atsmophere should absorb some but not others.
And i am not really a Physics guy.

I said nothing about a red laser pen.

I said a 10 gigawatt laser, i.e. a big honking laser weapon. I want to know if shoving that much power into a lower spectrum weapon is more effective then a higher one. i.e. is IR just better because it goes straight to heat without having to be converted to visible light first, or is there something else going on?

==Aelryinth


Aelryinth wrote:

I have a question for the physics guys here.

I was reading on the website there that only lasers in the visible light spectra would be usable on earth because of the atomosphere, the air would literally absorb gamma and UV rays.

Air does absorb many (not all) light frequencies outside the visible spectrum, but not instantaneously. So the full thickness of Earth's atmosphere protects against gamma ray/X-ray bursts and greatly blunts the Sun's UV output (sunburn up in space would be way worse than down here, even if it wouldn't look like that depicted in Deep Impact), but if you project a UV, X-ray, or gamma ray laser beam, it is going to be dangerous for quite a long distance.

Aelryinth wrote:

So, I was wondering about the viability of high-spectra energies as lasers.

Basically, is a 10 Gigawatt Infrared laser just as dangerous as a yellow laser or a blue laser or a UV laser or a Gamma ray laser of the same wattage? In short, if I put an identical amount of energy into each form of laser, are they all equally lethal assuming they reach their target?

For the most part, yes. "Assuming they reach their target" is the key here, and also includes how far they go into their target (cooking the insides is often more damaging than making a burn on the surface), and how vulnerable the targets are to particular frequencies, although when you are putting enough energy in to cook things by simple heating, the latter property starts making less of a difference. Infrared and visible light in excess are both going to be deadly, but will not make it through opaque targets until they burn their way through (or enough heat gets conducted through outer layers into vulnerable parts to do the dirty work), whereas gamma rays and to a lesser extent X-rays will go through solid matter with attenuation dependent mainly on distance multiplied by raw electron density (hence the importance of lead or depleted uranium for radiation shielding; this also works against high speed charged particles, and these substances conveniently also have big hunky nuclei to absorb neutrons all the better, although in the latter case uranium has the nasty side effect of fissioning some of the time, especially if not fully depleted, and superhigh energy gamma rays can also cause fission).

Aelryinth wrote:
I always wondered what would happen if you could take a given amount of visible light and break the Unified Field Theory, transform it all into microwaves, and get several zillion times as much microwave energy as white light energy, or some such.

Breaking Unified Field Theory or getting more energy out than you put in has to involve more than just cranking up light intensity. The first part we don't have a real clue how to do yet (somebody who figure out how to do it could get a Nobel Prize), and the second requires the energy you put in to cause a reaction, such as starting a fusion reaction -- actually, even though the second part is understood on a theoretical basis, it is hard enough to do in a practical way that you could get a Nobel Prize for that too.


FTL drive can be built along current scientific theories or your own. For some real scientific drives that allow you to travel faster then light, there is the Alcuberrie drive, the warp drive from Star Trek, which has some validity in a couple of published papers, and wormhole discovery/manipulation/creation of dark matter acting as the main force for concentrating or lessening gravity. Also, realize that the less mass you have for a ship or object traveling at light speed, the faster light speed becomes.

As for wormhole travel, for most classic SF work, you're limited to point to point travel. However, you may also discover that Wormhole A can connect to wormhole B and C, but B doesn't connect to C, nor B to C. Constructed wormholes are usually created by a new handwavium element built on a ship, a fixed location (IE wormhole gates), or even an external series of acceleration rings shot out from a ship and arrayed in a specific pattern.

For normal FTL, you also have to decide if it is real-time or dimensional suspension. Is it instantaneous? Does it cause the crew to have massive disruptions like jump sickness, turning the crew members into werewolves, that sort of thing? As for FTL communication and sensors, for maps involving the PC's ship via light speed sensors onlyis pretty easy if you create a short size limit for the point at which FTL can be used. If you go jump gates or alternate dimension, does the FTL medium allow for ship combat and communication ala B5, or is the ship impervious to all forms of attack while in FTL mode?

Magic FTL drives are some of the more interesting, because in Dragonstar, they use teleport drives to go around the laws of physics, or jump your ship into the astral plane where time doesn't pass and allows you to travel far more quickly then with normal sub-light travel.


Several years ago I read a science fiction short story (of which unfortunately I can neither remember the name nor the author's name) that had the premise that would-be conquerors who had 17th/18th Century technology but had stumbled upon some magical FTL drive principle that Earth scientists had managed to miss came to Earth to try to conquer it, got ROFLstomped, and then Humans explosively spread through the Galaxy with the drive that they got from their would-be conquerors. Fast forward to the present day: Humans have gotten complacent and disorganized, while the aliens have been learning from their mistakes and advancing the rest of their technology.


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The Road Not Taken, by Harry Turtledove.

The premise is that manipulating gravity is actually really, really easy, and humanity is unique in that they missed the trick. Everybody else focused all their tech that way, colonized all over the place, but they're still using matchlocks. And well... yeah. It goes as UnArcaneElection explains.


Alright I think with a lot of the information, I feel set on how I want to use FTL travel. I certainly don't want to make it instantaneous, since I want there to be a focus on exploration. Thanks again for the information and especially that website. It really has opened up my eyes to the implications of FTL. I'll probably go for the Alcubierre Drive, with some natural wormholes that the players can discover. I'll figure out the other complications (like gravity wells) but thanks again.


kestral287 wrote:

The Empire actually did that, on a smaller level. It's called the Galaxy Gun. The Death Star was designed as more than a planet-buster though.

And with Star Wars tech you can't do that as you describe anyway. When you get too close to a gravity well, such as a planet, you're forcibly shunted out of hyperspace. You'd make a fun little crater on impact but that's about it (which is pretty much what the Galaxy Gun was designed to do, and it did its job well. It also had explosive-laden projectiles much larger than an X-Wing though).

Which really just means that you should establish the rules of your FTL to disallow such things, not that you shouldn't allow FTL. Many settings demand FTL to be playable.

Fun crater lol..read what NASA has to say about FTL.

When you 'shunt out of hyperspace' you still have the potential energy of going FTL and NASA indicates also create a shotgun like blast as all the particulates that the front of your hyperspace/warp bubble collected (space isn't empty) now get ejected at FTL velocities destroying a couple solar systems at your destination/shunt out point.

Either way one fighter could destroy any planet and likely a system as getting shunted out doesn't negate energy.

RPG Superstar 2012 Top 16

Aye, you'd have to put all that potential energy somewhere...unless, of course, your warp space transfer is simply traveling at a controllable speed, and it's SPACE which is the key thing for FTL, so popping back into normal space is merely a question of going from grid paper with lots of little lines to grid paper with spaced out longer lines, and energy isn't a problem, just dimensional translation.

==Aelryinth

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Aelryinth wrote:
LazarX wrote:
Aelryinth wrote:

Meh. If you can handle tachyons and gravity, you can handle FTL communication.

Nobody knows how fast gravity is.

You don't speak of gravity as being "fast". Gravity is the bending of spacetime around mass.

mmm. I'm referring to something like this: If earth suddenly pops out of existence, and you're a light year away, how long before you could tell it wasn't there by observing the change in gravity?

That's the speed of gravity. If it's instantly possible to tell, then we have a speed of gravity. If it's not...time to measure!

It's a question we don't have an answer to until we successfully detect a gravity wave that's significant for us to measure. Then we need to create a gravity wave evemt and compare it's detection to our detection of the event's other effects.

RPG Superstar 2012 Top 16

oh, come on, Lazar. Surely creating a significant gravity wave event wouldn't be that hard. You'd only have to disintegrate a celestial body of some size, or something.

==Aelryinth

RPG Superstar 2012 Top 16

UnArcaneElection wrote:
Aelryinth wrote:

I have a question for the physics guys here.

I was reading on the website there that only lasers in the visible light spectra would be usable on earth because of the atomosphere, the air would literally absorb gamma and UV rays.

Air does absorb many (not all) light frequencies outside the visible spectrum, but not instantaneously. So the full thickness of Earth's atmosphere protects against gamma ray/X-ray bursts and greatly blunts the Sun's UV output (sunburn up in space would be way worse than down here, even if it wouldn't look like that depicted in Deep Impact), but if you project a UV, X-ray, or gamma ray laser beam, it is going to be dangerous for quite a long distance.

Aelryinth wrote:

So, I was wondering about the viability of high-spectra energies as lasers.

Basically, is a 10 Gigawatt Infrared laser just as dangerous as a yellow laser or a blue laser or a UV laser or a Gamma ray laser of the same wattage? In short, if I put an identical amount of energy into each form of laser, are they all equally lethal assuming they reach their target?

For the most part, yes. "Assuming they reach their target" is the key here, and also includes how far they go into their target (cooking the insides is often more damaging than making a burn on the surface), and how vulnerable the targets are to particular frequencies, although when you are putting enough energy in to cook things by simple heating, the latter property starts making less of a difference. Infrared and visible light in excess are both going to be deadly, but will not make it through opaque targets until they burn their way through (or enough heat gets conducted through outer layers into vulnerable parts to do the dirty work), whereas gamma rays and to a lesser extent X-rays will go through solid matter with attenuation dependent mainly on distance multiplied by raw electron density (hence the importance of lead or depleted uranium for radiation shielding; this also works against high...

MMM. okay, so the question got too broad. Basically, it's hard to measure a conversion from light to UV or Gamma Ray because the effects of a laser is significantly different.

Let's just stick to Infrared and light spectra.

Is there ANY difference in effect from using an IR laser (let's assume in space and keep atmosphere out of it) and a red, green or blue laser?

I'm assuming that (reflection factors aside!) that 10 gigawatts of power stuck into each mode is going to end up with basically the same thing, as a laser basically converts to heat on hitting something.

However...lasers used as Propulsion are a Thing, so visible lasers have mass and power, in addition. I'm just unsure of how that translates when used as a weapon.

==Aelryinth


Aelryinth wrote:
So you'd ram into a planet inertialess, turn off the drive, and your atoms would promptly take up the inertia and velocity of the surrounding vibrational atoms, and nothing happens of note.

Do you even orbital mechanics? You don't ram the planet inertialess. You use your inertialess drive to build as much gravitational potential energy as possible in the system, violating conservation of energy because being able to change your rest mass does that, and then you turn it off and hit with inertia.


Atarlost wrote:
Aelryinth wrote:
So you'd ram into a planet inertialess, turn off the drive, and your atoms would promptly take up the inertia and velocity of the surrounding vibrational atoms, and nothing happens of note.
Do you even orbital mechanics? You don't ram the planet inertialess. You use your inertialess drive to build as much gravitational potential energy as possible in the system, violating conservation of energy because being able to change your rest mass does that, and then you turn it off and hit with inertia.

Oh yeah, you can fall onto the planet. And that's nice and it'll do some damage. "Rods from God" style.

But it's fairly easy to intercept - assuming high end spacefaring civilization. And unless you're pretty damn big and solid, it's not planetcracking.
The inertialess doesn't really help here, other than making it a little easier to get into position. You could do the same thing with any ship capable of escape velocity.

Which is why you strap your inertialess drive to a moon, move it into position, turn it off and let nature take its course.


Aelryinth wrote:

Is there ANY difference in effect from using an IR laser (let's assume in space and keep atmosphere out of it) and a red, green or blue laser?

I'm assuming that (reflection factors aside!) that 10 gigawatts of power stuck into each mode is going to end up with basically the same thing, as a laser basically converts to heat on hitting something.

I think that the difference is energy efficiency one. Different types of lasers have different energy efficiency and they produce specific frequencies that correspond to specific parts of EM spectrum. At the moment I can't fight the clear info, only vague notes that red light lasers tend to be more energy efficient than green and blue ones. It might be that IR laser are more efficient than the red ones.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Drejk wrote:
Aelryinth wrote:

Is there ANY difference in effect from using an IR laser (let's assume in space and keep atmosphere out of it) and a red, green or blue laser?

The power of a laser is determined by it's frequency. the more power, the shorter the wavelength. So lasers at that power level are all X-Ray lasers.

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
LazarX wrote:
Drejk wrote:
Aelryinth wrote:

Is there ANY difference in effect from using an IR laser (let's assume in space and keep atmosphere out of it) and a red, green or blue laser?

The power of a laser is determined by it's frequency. the more power, the shorter the wavelength. So lasers at that power level are all X-Ray lasers.

Yeah I know I got that wrong, I should have put in wavelength instead of frequency.

RPG Superstar 2012 Top 16

uh, what?

You're telling me that you can't have a 10 gigawatt IR laser now?

That makes no sense at all.

It's like saying "No, you can't see the sun, it's putting out too much energy, it's all gamma rays!"

==Aelryinth

RPG Superstar 2012 Top 16

Atarlost wrote:
Aelryinth wrote:
So you'd ram into a planet inertialess, turn off the drive, and your atoms would promptly take up the inertia and velocity of the surrounding vibrational atoms, and nothing happens of note.
Do you even orbital mechanics? You don't ram the planet inertialess. You use your inertialess drive to build as much gravitational potential energy as possible in the system, violating conservation of energy because being able to change your rest mass does that, and then you turn it off and hit with inertia.

Not sure where this is going?

The idea is to have a story element where abusing inertialess is difficult, not where it's easy to weaponize and turn into End of Story Boom!

Which is also why you don't make Bergenholms that can make a planet inertialess ;) Lensmen is a cool read, but when you start operating on galactic space opera at that scale, wow.

===Aelryinth

Grand Lodge

Pathfinder PF Special Edition, Starfinder Roleplaying Game Subscriber
Aelryinth wrote:

uh, what?

You're telling me that you can't have a 10 gigawatt IR laser now?

That makes no sense at all.

It's like saying "No, you can't see the sun, it's putting out too much energy, it's all gamma rays!"

==Aelryinth

As it is, you don't see the true color of the sun. If you looked at the sun from orbit, you'd see a white orb. We see it differently on the ground because wavelength scattering. You can't see what's happening on the sun RIGHT NOW because it's 8 light minutes away. If it blew up this instant, it'd still look perfectly normal for 8 more minutes.

Yes.. the world of extreme physics is full of things which might not make "sense" from a layman's viewpoint.


insaneogeddon wrote:
kestral287 wrote:

The Empire actually did that, on a smaller level. It's called the Galaxy Gun. The Death Star was designed as more than a planet-buster though.

And with Star Wars tech you can't do that as you describe anyway. When you get too close to a gravity well, such as a planet, you're forcibly shunted out of hyperspace. You'd make a fun little crater on impact but that's about it (which is pretty much what the Galaxy Gun was designed to do, and it did its job well. It also had explosive-laden projectiles much larger than an X-Wing though).

Which really just means that you should establish the rules of your FTL to disallow such things, not that you shouldn't allow FTL. Many settings demand FTL to be playable.

Fun crater lol..read what NASA has to say about FTL.

When you 'shunt out of hyperspace' you still have the potential energy of going FTL and NASA indicates also create a shotgun like blast as all the particulates that the front of your hyperspace/warp bubble collected (space isn't empty) now get ejected at FTL velocities destroying a couple solar systems at your destination/shunt out point.

Either way one fighter could destroy any planet and likely a system as getting shunted out doesn't negate energy.

What NASA says means nothing in the context of this discussion.

You specifically cited Star Wars. That means we're playing under Star Wars rules, not NASA rules. That means that no, when you drop out of hyperspace (forcibly or otherwise) that energy is effectively 'lost'. Insert technobabble to explain such here.

Within the context of Star Wars, one fighter cannot destroy a planet with its engines. The universe Does Not Work That Way.

Really, once we start discussing any hypothetical universe, our rules no longer exist, no matter what those rules are. This is why it's vital to frame the rules of any new universe, which was pretty much my initial point.

You posited that FTL travel shouldn't be put in a game because players will use it to 'break' the game, and cited planet-busting as the example. The solution to that is not "don't use FTL", it's "use FTL that can't break planets". And, whether you or NASA like it, Star Wars is an excellent example of a universe operating under such rules.

RPG Superstar 2012 Top 16

LazarX wrote:
Aelryinth wrote:

uh, what?

You're telling me that you can't have a 10 gigawatt IR laser now?

That makes no sense at all.

It's like saying "No, you can't see the sun, it's putting out too much energy, it's all gamma rays!"

==Aelryinth

As it is, you don't see the true color of the sun. If you looked at the sun from orbit, you'd see a white orb. We see it differently on the ground because wavelength scattering. You can't see what's happening on the sun RIGHT NOW because it's 8 light minutes away. If it blew up this instant, it'd still look perfectly normal for 8 more minutes.

Yes.. the world of extreme physics is full of things which might not make "sense" from a layman's viewpoint.

Which is completely and totally avoiding the question.

Of course the sun looks white. It's a blending of all colors of the spectrum. It's yellow-tilted because of its age and the ratio of stuff burning inside it.

But what you're saying is you put too much power into a laser and it changes wavelength.

Which is utter nonsense. The only thing you change is the amplitude of the wave.

Energy in the EM spectrum is a function of wavelength, which is waves/second, and the power of that is amplitude, i.e. how tall those waves ARE.

The waves don't suddenly get shorter because you're cranking more power into them. As a matter of fact, I seem to remember that for a given amount of energy, the area under the curve will always be the same regardless of the wavelength used. So it doesn't matter if you have a million hertz or a billion hertz, they both deliver the same amount of energy at the same amplitude, it doesn't suddenly shift into 'high gear'.

My questions was, is there any reasonable difference between IR and the different colors of the spectrum for the same amount of energy input?

The only reply has been 'IR lasers are more efficient', which makes sense, as basically a beam of heat would be better at dumping heat then a beam of light, which has to be converted into heat.

===Aelryinth

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