What is it with people imagining that black holes have some magic gravitational property that allows them to draw things towards them any more effectively than an equal mass of matter that hasn't collapsed to a singularity?
You might as well dangle a big rock in front of your spacecraft. Or a carrot.
Gravity is a really weak force. That's why you can overcome the entire gravitational attraction of the mass of the Earth with your little finger. It's 10^33 times weaker than the electric force. To put that into context, here's Feynman:
"...If you were standing at arm's length from someone and each of you had one percent more electrons than protons, the repelling force would be incredible. How great? Enough to lift the Empire State building? No! To lift Mount Everest? No! The repulsion would be enough to lift a "weight" equal to that of the entire earth!"
This propulsion concept is just layer upon layer of nonsense. You "create" a black hole. How? At the very least, you need to be using as much mass to create it as the mass of the resulting black hole, that you create in some unspecified fashion. And then what? It won't have any more gravitational attraction than the mass you started with, which will be tiny. If it's small, it will also be extremely unstable (that's Hawking radiation, by the way). Your "solution" to this is to carry enough mass to create a whole series of these futile black holes, making your spacecraft immensely resistant to being accelerated by the tiny force of gravity you think you are generating.
yeah right. lets try forcing a ftl spaceship to fly through "the holes in the laws of physics" ........
i suppose everyone has read andersons sf novel "tau zero" .......
I don't think Alcubbier was ever proposing flying through "the holes in the laws of physics" but rather exploiting a quirk of relativity, namely space/time itself doesn't have a speed limit.
Well, that's certainly more manageable, given that it would currently take the Earth's entire output of energy for the next 10 million years to create just one kilogram of antimatter.
I'd hold off on booking a ticket, If I were you.
Yes, and at one time it would have required a massive bank of Voltaic cells to generate any worthwhile electrical power.
Besides, Alcubierrs original proposal required the mass energy equivalent of two and a half times the mass of the known universe.
I don't think Alcubbier was ever proposing flying through "the holes in the laws of physics" but rather exploiting a quirk of relativity, namely space/time itself doesn't have a speed limit.
right. maybe our entire universe is just a commuter journey to work for aliens ? they create another universe, ie this one, pop in here though a wormhole, and let the metric expansion of spacetime take them to the office .........
yeah right. lets try forcing a ftl spaceship to fly through "the holes in the laws of physics" ........
I thought I had been reasonably clear about the probable impracticality of having to work in the 'borderline' areas without suggesting any actual magic spells beyond flights of fancy...
Once we get physics down to absolutely everything being absolutely understood then I'll accept there aren't any holes in it. Until then, we have tardises, hyperspace jump gates, warp engines, wormholes, dimension portals and hordes of green/grey aliens probing orifi.
i suppose everyone has read andersons sf novel "tau zero" .......
No... presumably that's not a requirement though...
There's always folding space but I think you need to be high on spice to do that and we haven't found that planet yet and would probably need FTL to get there in any useable timeframe so perhaps that's a non-starter.
Apart from the physics saying travel close to the speed of light is damn near impossible, if it were in fact possible then we might expect aliens to arrive from time to time from distant star systems and galaxies. Isn't it a bit like time travel? If it were possible, let alone easy, we might similarly expect visitations from the future.
Apart from the physics saying travel close to the speed of light is damn near impossible, if it were in fact possible then we might expect aliens to arrive from time to time from distant star systems and galaxies. Isn't it a bit like time travel? If it were possible, let alone easy, we might similarly expect visitations from the future.
Even if the journey to any other star system is easily affordable, and only takes a week, and we (or they) have good data to show where other possibly infested planets are - there's still The Prime Directive.
It may be quite a while before 'we' find some aliens, on their home planet, we think we'd like to have any kind of relationship with. Some of them are incredibly ugly and ill mannered.
Gravity is a really weak force. That's why you can overcome the entire gravitational attraction of the mass of the Earth with your little finger. It's 10^33 times weaker than the electric force. To put that into context, here's Feynman:
So you're saying that a ship located - say - fifty metres from a black hole would not move toward it? That seems on the face of it to fly in the face of everything we know about black holes. I thought the whole point of them was the immense attraction of their mass.
So you're saying that a ship located - say - fifty metres from a black hole would not move toward it? That seems on the face of it to fly in the face of everything we know about black holes. I thought the whole point of them was the immense attraction of their mass.
They have exactly the same gravitational attraction as the matter which created them in the first place. They don't suddenly become cosmic hoovers.
Creating (in some unspecified manner) a micro black hole in front of your spacecraft doesn't achieve anything that you couldn't have achieved by dangling the same mass of rock in front of it - almost nothing, given how weak gravity is. And nothing at all, given that you have to have somehow moved it from inside the ship.
It's worse than that, because creating a micro black hole would require vast amounts of energy to do, and the thing would explode almost as soon as you created it. Like I said, none of this makes any sense. It's wrong on so many levels it's not worth analysing them all!
Rather than putting a mass that you have carried with you in front of you, and hoping that its tiny gravitational force will pull you along, you need to throw the mass out of the back of the ship at high speed, and rely on Newton's laws of motion to propel you. This is what rockets do.
If a tiny black hole were to miraculously appear in front of you (and it would still contain a great deal of mass - one the size of a small marble would have as much mass as the Earth, for example), then of course you would fall towards it. But you would need to worry about tidal forces tearing your ship apart. Large black holes are far more benign in that respect than small ones. And it isn't going to conveniently move to pull you along, let alone accelerate.
About the only thing you might be able to do with a black hole is to use one as a gravitational slingshot, in much the same way as probes have used planets within our solar system. But you'd have to get to one first.
They have exactly the same gravitational attraction as the matter which created them in the first place. They don't suddenly become cosmic hoovers.
Ah so you're suffering from a limited imagination! Finally we find out what your problem is.
What we (and Alan Dean Foster) are talking about is creating a gravity anomaly that mimics a black hole (in fact ADF doesn't even mention black holes). There's no talk of using mass to create it. Just some kind of gravity generator.
Now, can your limited imagination finally grasp what we're suggesting?
Personally I don't like the idea and I don't see why it would lead to superluminal speeds but since I'm willing to accept artificial gravity as being a fairly common feature of science fiction I have no problem with the basic premise. It remains to be seen of course whether or not artificial gravity can be created - which is why I've mentioned a couple of times that that's the stumbling block.
Ah so you're suffering from a limited imagination! Finally we find out what your problem is.
What we (and Alan Dean Foster) are talking about is creating a gravity anomaly that mimics a black hole (in fact ADF doesn't even mention black holes). There's no talk of using mass to create it. Just some kind of gravity generator.
Oh, I can do imagination. I've just invented a FTL drive that uses pellets of strawberry jelly to create a reality inversion field. I've invented it in my head, where it doesn't matter that it's complete bollocks.
Alan Dean Foster rambles on about "hydrogen sparkplugs", amongst other things. None of it means anything.
Now, can your limited imagination finally grasp what we're suggesting?
Sure I can. You are suggesting that you can make up any old rubbish you like, and expect people who actually know something about physics to take you seriously.
Sure I can. You are suggesting that you can make up any old rubbish you like, and expect people who actually know something about physics to take you seriously.
I have news for you. This is a public general discussion web forum. It's not a physics symposium. I'm not expecting anyone to believe anything particularly. You're the only one taking it seriously. If you read my posts more carefully instead of going off into a hissy fit you'll see that it's not my theory and I don't even like it because I don't think it addresses the actual problem of FTL.
But rant on, bro, if you think it's really that important.
... There's no talk of using mass to create it. Just some kind of gravity generator. ....
On the basis that artificial gravity isn't a guarantee of being able to produce a point of gravity outside the ship:
This is where the particle accelerator comes in. At near lightspeed, a particle will have a relativistic gain in mass, so if you have a sufficiently large quantity of particles in your accelerator there will be a sufficiently large gain in mass to cause a gravitational effect.
If your accelerator is circular, the apparent centre of this newly-created gravity will be the middle of your circular accelerator, so...
Your spaceship is in two parts - a circular particle accelerator and a stick-like main body, such that one can pass through the other.
Start with the accelerator some distance ahead, and switch it on. The mass increase of the accelerated particles gives rise to a gravitational effect, which attracts the main part of the ship. The accelerator will also move a very small amount but its extremely high mass (and therefore inertia) means this won't be by much.
When the ship is halfway through (or before, but not after), switch off the accelerator.
The accelerator (or rather the particles within) come to a stop, return to their normal mass, and the whole thing becomes light enough to be towed by the main ship which is still moving forward.
This can be repeated for further acceleration.
Unfortunately, given the nature of the operation of the drive - i.e. a stick repeatedly entering a circle - I'm not sure it would get a very complimentary nickname.
Sort of like a needle and an electromagnetic coil, except the coil has a variable mass so you can take it with you. Job done, though still no lightspeed. One problem at a time...
I have news for you. This is a public general discussion web forum. It's not a physics symposium. I'm not expecting anyone to believe anything particularly. You're the only one taking it seriously. If you read my posts more carefully instead of going off into a hissy fit you'll see that it's not my theory and I don't even like it because I don't think it addresses the actual problem of FTL.
It seems to me that the one throwing a hissy fit when the flaws in his understanding are pointed out is you...
But thanks for confirming that nothing you say is meant to be taken seriously. That does provide some much-needed context.
On the basis that artificial gravity isn't a guarantee of being able to produce a point of gravity outside the ship:
This is where the particle accelerator comes in. At near lightspeed, a particle will have a relativistic gain in mass, so if you have a sufficiently large quantity of particles in your accelerator there will be a sufficiently large gain in mass to cause a gravitational effect.
So you have access to an unbelievably large amount of energy, along with a vast particle accelerator containing huge (and very heavy) superconducting magnets (among many other things) and you plan to use it to create a tiny amount of additional gravity (over and above that due to its inherent mass), which will have an imperceptible effect on anything, let alone your spacecraft. What with gravity being an incredibly weak force, as I have already explained.
Your spaceship is in two parts - a circular particle accelerator and a stick-like main body, such that one can pass through the other.
Start with the accelerator some distance ahead, and switch it on. The mass increase of the accelerated particles gives rise to a gravitational effect, which attracts the main part of the ship. The accelerator will also move a very small amount but its extremely high mass (and therefore inertia) means this won't be by much.
When the ship is halfway through (or before, but not after), switch off the accelerator.
The accelerator (or rather the particles within) come to a stop, return to their normal mass, and the whole thing becomes light enough to be towed by the main ship which is still moving forward.
On the contrary, your particle accelerator would be so massive (much more massive than the relativistic particle mass you think would create additional gravity when you switch it on) that the "main ship" would immediately grind to a halt, when it eventually drifts through the centre of your "accelerator" a few months or years later (I'll give you the numbers, once you've fleshed out your design with some actual details) .
... On the contrary, your particle accelerator would be so massive (much more massive than the relativistic particle mass you think would create additional gravity when you switch it on) that the "main ship" would immediately grind to a halt, when it eventually drifts through the centre of your "accelerator" a few months or years later (I'll give you the numbers, once you've fleshed out your design with some actual details) .
You are definitely having trouble comprehending the nature of this thread. That said, it would be rude not to thank you for your splendidly kind offer to use your magnificent intellect to give me some numbers and further enlighten us lowly peasants with the benefit of your wisdom.
1) "sufficiently large quantity of particles", i.e. not just a couple of protons, maybe not even a particle accelerator, maybe even just two contra-rotating rings.
2) there we are in our spaceship with artificial gravity, still constrained by the specification of an underground 20th-century concrete installation.
3) if we need energy we can use solar power and really big batteries and a long extension lead, or maybe fusion has been solved by then, or we need to feed several billion hamsters and find a really big poop scoop.
4) the cavemen died out because they didn't bother to invent fire once they found out there was nowhere to plug in the microwave.
You are definitely having trouble comprehending the nature of this thread.
Am I? The thread poses the question: "Faster than light travel - will it ever be possible?"
A couple of posters, including you, seem to have interpreted this as an invitation to post various hopelessly impractical means of achieving sub-light-speed propulsion. Then you get upset when I point out why they won't work. You seem to think that is somehow contrary to the "nature of the thread". Perhaps you would prefer me just to congratulate you on the fertility of your imagination?
That said, it would be rude not to thank you for your splendidly kind offer to use your magnificent intellect to give me some numbers and further enlighten us lowly peasants with the benefit of your wisdom.
This should be good...
1) "sufficiently large quantity of particles", i.e. not just a couple of protons, maybe not even a particle accelerator, maybe even just two contra-rotating rings.
You are living up to your moniker. What is a "sufficiently large quantity of particles"? I can't do the sums without the numbers! But why do you need more than one proton anyway? All you have to do is make it go fast enough, and you will have all the mass you could possibly want!
2) there we are in our spaceship with artificial gravity, still constrained by the specification of an underground 20th-century concrete installation.
I don't understand what you are saying. Are you hinting that you have devised another way of building a non-linear particle accelerator that doesn't involve very large and heavy magnets, and large structures to hold everything together? Do tell.
3) if we need energy we can use solar power and really big batteries and a long extension lead, or maybe fusion has been solved by then, or we need to feed several billion hamsters and find a really big poop scoop.
Well, let's take your most practical suggestion. Fusion power is about 1% efficient at converting mass into energy. How much fuel were you planning to take aboard your ship?
May I suggest that you look at this another way? Energy and matter are different forms of the same thing (the relationship is succinctly expressed in Einstein's famous equation). So one way of looking at matter is that it is the most concentrated form of energy you can possibly have. Sadly we know of no way of converting more than a tiny fraction of matter into energy, without the benefit of an equal amount of antimatter (which is not widely available).
Your propulsion system relies on taking energy and turning it into "relativistic mass" - itself a very inefficient process. So you are going from mass (in the form of fuel) to energy and then to "relativistic mass". But you cannot possibly create more mass than you started off with, even if you were able to turn all the fuel mass into energy, and impart all that energy to the particle(s), which you can't.
FTL / NAFAL is either a plot device we take as a given in SF or something we discuss using numbers.
Suppose I said to someone that it's possible to store the entire Internet on a laptop, would you congratulate me on my open mind or dismiss my argument with numbers?
Strictly speaking that is not Faster than Light - in warping space you reduce the actual distance so keeping with the rule that FTL travel is not possible - it is analogous to the Warp Drive of the Starship Enterprise.
Star Trek would be the obvious exception - the warp drive warps spacetime to allow FLT travel.
Anyway the Infinite Improbability Drive is a wonderful new method of crossing interstellar distances in a mere nothingth of a second, without all that tedious mucking about in hyperspace.:)
Sorry I'm a bit late in confirming the validity of this post. I was having a bit of a snooze.
lets all become brains in jars then we can PRETEND these impossibilities ..... i daresay some people .... oops i mean brains ...... would prefer endless sex instead .. .... the matrix has much to recommend it ........
Comments
Okay so it needs a bit of development work.;-)
I don't think Alcubbier was ever proposing flying through "the holes in the laws of physics" but rather exploiting a quirk of relativity, namely space/time itself doesn't have a speed limit.
Yes, and at one time it would have required a massive bank of Voltaic cells to generate any worthwhile electrical power.
Besides, Alcubierrs original proposal required the mass energy equivalent of two and a half times the mass of the known universe.
right. maybe our entire universe is just a commuter journey to work for aliens ? they create another universe, ie this one, pop in here though a wormhole, and let the metric expansion of spacetime take them to the office .........
Once we get physics down to absolutely everything being absolutely understood then I'll accept there aren't any holes in it. Until then, we have tardises, hyperspace jump gates, warp engines, wormholes, dimension portals and hordes of green/grey aliens probing orifi.
No... presumably that's not a requirement though...
There's always folding space but I think you need to be high on spice to do that and we haven't found that planet yet and would probably need FTL to get there in any useable timeframe so perhaps that's a non-starter.
Your article said the drive previously required a "ball of antimatter the size of Jupiter".
Clearly there have been a series of profound incremental enhancements!
It may be quite a while before 'we' find some aliens, on their home planet, we think we'd like to have any kind of relationship with. Some of them are incredibly ugly and ill mannered.
Creating (in some unspecified manner) a micro black hole in front of your spacecraft doesn't achieve anything that you couldn't have achieved by dangling the same mass of rock in front of it - almost nothing, given how weak gravity is. And nothing at all, given that you have to have somehow moved it from inside the ship.
It's worse than that, because creating a micro black hole would require vast amounts of energy to do, and the thing would explode almost as soon as you created it. Like I said, none of this makes any sense. It's wrong on so many levels it's not worth analysing them all!
Rather than putting a mass that you have carried with you in front of you, and hoping that its tiny gravitational force will pull you along, you need to throw the mass out of the back of the ship at high speed, and rely on Newton's laws of motion to propel you. This is what rockets do.
If a tiny black hole were to miraculously appear in front of you (and it would still contain a great deal of mass - one the size of a small marble would have as much mass as the Earth, for example), then of course you would fall towards it. But you would need to worry about tidal forces tearing your ship apart. Large black holes are far more benign in that respect than small ones. And it isn't going to conveniently move to pull you along, let alone accelerate.
About the only thing you might be able to do with a black hole is to use one as a gravitational slingshot, in much the same way as probes have used planets within our solar system. But you'd have to get to one first.
What we (and Alan Dean Foster) are talking about is creating a gravity anomaly that mimics a black hole (in fact ADF doesn't even mention black holes). There's no talk of using mass to create it. Just some kind of gravity generator.
Now, can your limited imagination finally grasp what we're suggesting?
Personally I don't like the idea and I don't see why it would lead to superluminal speeds but since I'm willing to accept artificial gravity as being a fairly common feature of science fiction I have no problem with the basic premise. It remains to be seen of course whether or not artificial gravity can be created - which is why I've mentioned a couple of times that that's the stumbling block.
Alan Dean Foster rambles on about "hydrogen sparkplugs", amongst other things. None of it means anything.
Sure I can. You are suggesting that you can make up any old rubbish you like, and expect people who actually know something about physics to take you seriously.
But rant on, bro, if you think it's really that important.
This is where the particle accelerator comes in. At near lightspeed, a particle will have a relativistic gain in mass, so if you have a sufficiently large quantity of particles in your accelerator there will be a sufficiently large gain in mass to cause a gravitational effect.
If your accelerator is circular, the apparent centre of this newly-created gravity will be the middle of your circular accelerator, so...
Your spaceship is in two parts - a circular particle accelerator and a stick-like main body, such that one can pass through the other.
Start with the accelerator some distance ahead, and switch it on. The mass increase of the accelerated particles gives rise to a gravitational effect, which attracts the main part of the ship. The accelerator will also move a very small amount but its extremely high mass (and therefore inertia) means this won't be by much.
When the ship is halfway through (or before, but not after), switch off the accelerator.
The accelerator (or rather the particles within) come to a stop, return to their normal mass, and the whole thing becomes light enough to be towed by the main ship which is still moving forward.
This can be repeated for further acceleration.
Unfortunately, given the nature of the operation of the drive - i.e. a stick repeatedly entering a circle - I'm not sure it would get a very complimentary nickname.
Sort of like a needle and an electromagnetic coil, except the coil has a variable mass so you can take it with you. Job done, though still no lightspeed. One problem at a time...
But thanks for confirming that nothing you say is meant to be taken seriously. That does provide some much-needed context.
On the contrary, your particle accelerator would be so massive (much more massive than the relativistic particle mass you think would create additional gravity when you switch it on) that the "main ship" would immediately grind to a halt, when it eventually drifts through the centre of your "accelerator" a few months or years later (I'll give you the numbers, once you've fleshed out your design with some actual details) .
1) "sufficiently large quantity of particles", i.e. not just a couple of protons, maybe not even a particle accelerator, maybe even just two contra-rotating rings.
2) there we are in our spaceship with artificial gravity, still constrained by the specification of an underground 20th-century concrete installation.
3) if we need energy we can use solar power and really big batteries and a long extension lead, or maybe fusion has been solved by then, or we need to feed several billion hamsters and find a really big poop scoop.
4) the cavemen died out because they didn't bother to invent fire once they found out there was nowhere to plug in the microwave.
A couple of posters, including you, seem to have interpreted this as an invitation to post various hopelessly impractical means of achieving sub-light-speed propulsion. Then you get upset when I point out why they won't work. You seem to think that is somehow contrary to the "nature of the thread". Perhaps you would prefer me just to congratulate you on the fertility of your imagination?
This should be good...
You are living up to your moniker. What is a "sufficiently large quantity of particles"? I can't do the sums without the numbers! But why do you need more than one proton anyway? All you have to do is make it go fast enough, and you will have all the mass you could possibly want!
I don't understand what you are saying. Are you hinting that you have devised another way of building a non-linear particle accelerator that doesn't involve very large and heavy magnets, and large structures to hold everything together? Do tell.
Well, let's take your most practical suggestion. Fusion power is about 1% efficient at converting mass into energy. How much fuel were you planning to take aboard your ship?
May I suggest that you look at this another way? Energy and matter are different forms of the same thing (the relationship is succinctly expressed in Einstein's famous equation). So one way of looking at matter is that it is the most concentrated form of energy you can possibly have. Sadly we know of no way of converting more than a tiny fraction of matter into energy, without the benefit of an equal amount of antimatter (which is not widely available).
Your propulsion system relies on taking energy and turning it into "relativistic mass" - itself a very inefficient process. So you are going from mass (in the form of fuel) to energy and then to "relativistic mass". But you cannot possibly create more mass than you started off with, even if you were able to turn all the fuel mass into energy, and impart all that energy to the particle(s), which you can't.
No free lunch for you, I'm afraid.
I'm taking it seriously enough to agree with njp.
FTL / NAFAL is either a plot device we take as a given in SF or something we discuss using numbers.
Suppose I said to someone that it's possible to store the entire Internet on a laptop, would you congratulate me on my open mind or dismiss my argument with numbers?
My dream is that the ansible is possible btw.
Strictly speaking that is not Faster than Light - in warping space you reduce the actual distance so keeping with the rule that FTL travel is not possible - it is analogous to the Warp Drive of the Starship Enterprise.