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Old 5th November 2017, 06:52 PM   #241
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Originally Posted by GlennB View Post
This website calculates the apparent g of rotating space habs according to the input parameters, and also discusses some side issues such as coriolis force and so on. It's worth a read.
Cool, thanks

Quote:
Out of interest I put in a target of 0.5g and a hab radius of 200m, which is not a huge space to support life for hundreds of thousands of years . Turns out the hab would need to be rotating at 1.5 revs per minute. I'd suggest that's a pretty fierce rate for something so big, especially if the hab area is sealed inside a significantly larger asteroid/comet.
Okay. I think you have a point and as jimbob said the comet idea probably isn't going to work, at least if we want to spin the whole thing up. Earlier in the thread I did suggest reinforcing it's surface (I mentioned a wire mesh), but I'm thinking that's not going to be strong enough, though someone would have to actually run the numbers.

His hollowed out nickel-iron asteroid sounds more feasible though.

200m is probably too small for our purposes.
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Old 5th November 2017, 09:06 PM   #242
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Originally Posted by theprestige View Post
I think that any plan that requires a few centuries of prep work will require humans who live a few centuries at least.
I think 1000 years from now either lifespans will be extended for human beings, or our descendants will be made of silicon, where "lifespan" has an entirely different meaning.

And, while I think it will happen, it's another case of "and then something amazing happens, which I can't even describe yet."
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Old 6th November 2017, 01:26 AM   #243
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Originally Posted by theprestige View Post
I think that any plan that requires a few centuries of prep work will require humans who live a few centuries at least.
I don't believe that.

Some of the cathedrals in the middle ages took 200+ years to construct. No individual that started the project lived to see it complete - and yet people were happy to throw huge efforts into it.

I guess it was important that there was a long lasting institution (the church) which was central to these projects. Our interstellar project will need something similar I guess.

Maybe long term projects like interstellar travel will replace religion in human society - i.e. give people a sense of purpose, make them believe their lives have meaning, and give them something to believe in. And with the added benefit that it would actually be real!

Another reason why we should go .

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Old 6th November 2017, 11:11 AM   #244
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Originally Posted by Roboramma View Post
Well, the idea was not that you don't have to slow down, the idea was that you don't have to slow down the entire mass of your ship/comet. Whatever part of it you don't need you can abandon. Every kg of stuff that you leave on that initial trajectory saves fuel. If that's 99% of your mass then you're saving a lot of fuel. Obviously you'd want to take the engines.
I'd think you wouldn't want to abandon any of it except to use it as reaction mass to slow down.
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Old 6th November 2017, 11:16 AM   #245
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Originally Posted by GlennB View Post
Nope. It's a normal force created by the rotation of the vessel in that context, and it just gets the snazzy label 'artificial gravity'. It's of no use whatsoever if you're on the outside, so we're still stuck with how to perform the work required to engineer the asteroid or comet in the first place. The film 'Armageddon' couldn't handle that issue so they pretty much ignored it.

Maybe you guys could address the actual issues there, such as lack of traction for your vehicles in micro-g, and how to move around without constantly flying up into the air?

But if your view is "anything is possible in the future" then, yeah, anything is possible in the future.
Build a simple truss around the asteroid. Just a ring to start. Attach your machines to that. Mine the asteroid for metals. Build more trusses. Repeat until it's entirely encased. Now you have a ship hull full of building materials.
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Old 6th November 2017, 10:18 PM   #246
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Originally Posted by phiwum View Post
Quite a while. Brilliant understatement.
Is this wrong?

"Accelerating to speeds closer to the speed of light with a relativistic rocket would allow the on-ship travel time to be drastically lower, but would require very large amounts of energy. A way to do this is space travel using constant acceleration. Traveling to the Andromeda Galaxy, 2 million light years away, would take 28 years on-ship time with a constant acceleration of 1g and a deceleration of 1g after reaching half way, to be able to stop."
https://en.wikipedia.org/wiki/Intergalactic_travel
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Old 6th November 2017, 11:39 PM   #247
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Originally Posted by Fudbucker View Post
Is this wrong?

"Accelerating to speeds closer to the speed of light with a relativistic rocket would allow the on-ship travel time to be drastically lower, but would require very large amounts of energy. A way to do this is space travel using constant acceleration. Traveling to the Andromeda Galaxy, 2 million light years away, would take 28 years on-ship time with a constant acceleration of 1g and a deceleration of 1g after reaching half way, to be able to stop."
https://en.wikipedia.org/wiki/Intergalactic_travel
How much fuel are you planning on bringing with you?
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Old 7th November 2017, 12:58 AM   #248
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Originally Posted by Roboramma View Post
How much fuel are you planning on bringing with you?
Just enough to sustain 1g acceleration for 28 years ... and not a drop more. How much would that be, per ton of ship, I wonder.
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Old 7th November 2017, 01:17 AM   #249
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Originally Posted by Craig B View Post
Just enough to sustain 1g acceleration for 28 years ... and not a drop more. How much would that be, per ton of ship, I wonder.
According to this guy, which looks right to me, if you are using anti-matter as fuel and your rocket is 100% efficient, you need 4.2 trillion kg of anti-matter fuel/kg of payload to get to Andromeda, if you want to stop there, by accelerating at 1g all the way.

Considering that there are probably no large natural sources of anti-matter and it's probably impossible to produce it efficiently, 4.2 trillion kg is a lot. You could use a different fuel source, but unless you are using a black hole emitting hawking radiation, which has plenty of problems of it's own, you are suddenly increasing your fuel requirements dramatically.
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Old 7th November 2017, 05:16 AM   #250
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Originally Posted by phunk View Post
Build a simple truss around the asteroid. Just a ring to start. Attach your machines to that. Mine the asteroid for metals. Build more trusses. Repeat until it's entirely encased. Now you have a ship hull full of building materials.
Nice one!
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Old 7th November 2017, 01:53 PM   #251
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Originally Posted by Roboramma View Post
According to this guy, which looks right to me, if you are using anti-matter as fuel and your rocket is 100% efficient, you need 4.2 trillion kg of anti-matter fuel/kg of payload to get to Andromeda, if you want to stop there, by accelerating at 1g all the way.

Considering that there are probably no large natural sources of anti-matter and it's probably impossible to produce it efficiently, 4.2 trillion kg is a lot. You could use a different fuel source, but unless you are using a black hole emitting hawking radiation, which has plenty of problems of it's own, you are suddenly increasing your fuel requirements dramatically.
You could save at least some fuel by using a giant laser to accelerate the craft, at least part of the way.
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Old 7th November 2017, 02:28 PM   #252
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Originally Posted by Fudbucker View Post
You could save at least some fuel by using a giant laser to accelerate the craft, at least part of the way.
How much laser would you need to save a meaningful fraction of 4.2 trillion tons of anti-matter?

And how do you solve the problem of encountering interstellar hydrogen at relativistic speeds?
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Old 7th November 2017, 02:39 PM   #253
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Originally Posted by theprestige View Post
How much laser would you need to save a meaningful fraction of 4.2 trillion tons of anti-matter?
Good question. Suppose you had a swarm of large solar collectors around a star collecting 1% of its total output. How big a laser could you power with that? For how long would it provide propulsion?

Quote:
And how do you solve the problem of encountering interstellar hydrogen at relativistic speeds?
As long as we're not breaking the laws of physics, I imagine some kind of high-tech "scoop" could work, and the interstellar hydrogen collected could augment the anti-matter drive, saving some amount of fuel.
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Old 7th November 2017, 02:58 PM   #254
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Originally Posted by Fudbucker View Post
Good question. Suppose you had a swarm of large solar collectors around a star collecting 1% of its total output. How big a laser could you power with that? For how long would it provide propulsion?



As long as we're not breaking the laws of physics, I imagine some kind of high-tech "scoop" could work, and the interstellar hydrogen collected could augment the anti-matter drive, saving some amount of fuel.
And if you couldn't induce the scooped hydrogen to fuse, at least the scoop arrangement
would be a useful brake for the last part of the voyage. I think when you're discussing intergalactic expeditions, the range of earth based laser propulsion would be absolutely negligible.
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Old 7th November 2017, 03:51 PM   #255
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Originally Posted by theprestige View Post
How much laser would you need to save a meaningful fraction of 4.2 trillion tons of anti-matter?

And how do you solve the problem of encountering interstellar hydrogen at relativistic speeds?
It is a problem but at least it reduces the number of problems you need to solve - why worry about making your ship habitable, for example?
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Old 7th November 2017, 04:01 PM   #256
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Why is wormhole technology so out of the question? Wouldn't it be similar to time travel since you are folding space and side stepping time?

I just rewatched Arrival last night and I was still amazed at the concept that speech/communication wires the brain's perceptions. The aliens didn't think in linear time. If we don't think in linear time how does that affect physics?

I don't think it's that far off in the future.
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Old 7th November 2017, 04:09 PM   #257
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Originally Posted by Jodie View Post
Why is wormhole technology so out of the question? Wouldn't it be similar to time travel since you are folding space and side stepping time?

[...]
Can you name one iota of wormhole technology?

That's why. There is none.
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Old 7th November 2017, 04:11 PM   #258
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Like any of the major countries or corporations working on it would publish that fact while it was still in development.
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Old 7th November 2017, 04:15 PM   #259
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Originally Posted by Jodie View Post
Like any of the major countries or corporations working on it would publish that fact while it was still in development.

Oh! Even better. The fact that there is no evidence is proof of a global conspiracy of silence.

Is there any woo you don't subscribe to?
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Old 7th November 2017, 04:20 PM   #260
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Have you done any reading lately on the topic? Obviously not. Ignorance doesn't make you right John.
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Old 7th November 2017, 04:27 PM   #261
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Originally Posted by Jodie View Post
Have you done any reading lately on the topic? Obviously not. Ignorance doesn't make you right John.
I read up on woo every day. Did you have a less obvious point?

Oh, maybe you meant to ask if I read up on wormhole technology. I'll look at anything you've got.

Waiting...
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Old 7th November 2017, 04:31 PM   #262
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Dude, I'm working off the assumption that anyone contributing to the thread has actually read something about the topic or at least checks up on it once in awhile. I suggest that if you can get to this forum then you are perfectly capable of doing your own google research. However, I doubt that's your point. Go ahead, keep derailing the thread.
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Old 7th November 2017, 04:45 PM   #263
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Originally Posted by Jodie View Post
Dude, I'm working off the assumption that anyone contributing to the thread has actually read something about the topic or at least checks up on it once in awhile. I suggest that if you can get to this forum then you are perfectly capable of doing your own google research. However, I doubt that's your point. Go ahead, keep derailing the thread.
I've read every post in this thread. I know what wormholes are purported to be. I first read about them in 1975. This is not a derail, but a request for evidence or descriptions of what you call 'wormhole technology' .
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Old 7th November 2017, 04:47 PM   #264
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Originally Posted by theprestige View Post
How much laser would you need to save a meaningful fraction of 4.2 trillion tons of anti-matter?

And how do you solve the problem of encountering interstellar hydrogen at relativistic speeds?
Dodge very fast.
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Old 7th November 2017, 04:51 PM   #265
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Originally Posted by Jodie View Post
Like any of the major countries or corporations working on it would publish that fact while it was still in development.
Well I can tell you for sure that NASA isn't working on it. They are a publicly accountable organisation; they have to justify and account for every penny they spend,. If they were working on wormhole technology or an "Einstein-Rosen" bridge device like the alien machine in Carl Sagan's "Contact", everyone would know about it.

This is the biggest trap that stupid conspiracy theorist nutjobs fall into when they accuse NASA of sooper sekrit space programmes and ongoing cover ups of allegedly faked moon landings.Those things cost money (far more money than the Apollo programme cost) and those costs would be ongoing...

► Paying off people to shut up - money
► Killing off people who won't shut up - money
► Paying shills to spread disinformation - money
► Landing equipment remotely on the moon to account for the LRO pictures of the landing sites - absolute shiploads of money
► Sample return missions to account for the nearly 400kg of lunar materials brought back - absolute shiploads more money.

All this money has to be coming out of someone's budget. CTs are too stupid to get this.
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Old 7th November 2017, 06:27 PM   #266
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Originally Posted by Jodie View Post
Why is wormhole technology so out of the question? Wouldn't it be similar to time travel since you are folding space and side stepping time?
The fact that wormholes would imply time travel is pretty good reason to think that they are impossible, though admittedly not conclusive. There are enough paradoxes associated with time travel that it's hard to imagine how it could exist in a consistent way in our universe.

Wormholes have major problems. Most aren't traversable. Those that are require exotic forms of matter/energy that we have no reason to believe exists.

Even if the necessary ingredients did exist, the engineering, manufacturing, and economic problems would be orders of magnitude greater than even the relativistic spacecraft we have been discussing.

Quote:
I just rewatched Arrival last night and I was still amazed at the concept that speech/communication wires the brain's perceptions.
While it made for an interesting movie, the Sapir-Whoorf hypothesis is on pretty shaky ground.

Quote:
The aliens didn't think in linear time. If we don't think in linear time how does that affect physics?
Our thoughts don't affect physics, except in the mundane sense that your brain is connected to your body with has physical interactions with the world. Ie. you can move a glass of water with your mind by picking it up with your hand.
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Old 7th November 2017, 07:03 PM   #267
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Originally Posted by Roboramma View Post
...
Our thoughts don't affect physics, except in the mundane sense that your brain is connected to your body with has physical interactions with the world. Ie. you can move a glass of water with your mind by picking it up with your hand.

Well crap... I've been going about telekinesis all wrong.


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Old 7th November 2017, 08:29 PM   #268
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Originally Posted by John Jones View Post
I've read every post in this thread. I know what wormholes are purported to be. I first read about them in 1975. This is not a derail, but a request for evidence or descriptions of what you call 'wormhole technology' .
No, you saw my post, you're bored, so you thought it was entertaining to make fun of my asking a question without doing your own homework.
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Old 7th November 2017, 08:31 PM   #269
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Originally Posted by smartcooky View Post
Well I can tell you for sure that NASA isn't working on it. They are a publicly accountable organisation; they have to justify and account for every penny they spend,. If they were working on wormhole technology or an "Einstein-Rosen" bridge device like the alien machine in Carl Sagan's "Contact", everyone would know about it.

This is the biggest trap that stupid conspiracy theorist nutjobs fall into when they accuse NASA of sooper sekrit space programmes and ongoing cover ups of allegedly faked moon landings.Those things cost money (far more money than the Apollo programme cost) and those costs would be ongoing...

► Paying off people to shut up - money
► Killing off people who won't shut up - money
► Paying shills to spread disinformation - money
► Landing equipment remotely on the moon to account for the LRO pictures of the landing sites - absolute shiploads of money
► Sample return missions to account for the nearly 400kg of lunar materials brought back - absolute shiploads more money.

All this money has to be coming out of someone's budget. CTs are too stupid to get this.
Other countries are working on it, and NASA too, but we are a far cry from jumping across the universe. They are looking at more mundane applications for it here on earth.
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Old 7th November 2017, 08:36 PM   #270
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Originally Posted by Roboramma View Post
The fact that wormholes would imply time travel is pretty good reason to think that they are impossible, though admittedly not conclusive. There are enough paradoxes associated with time travel that it's hard to imagine how it could exist in a consistent way in our universe.

Wormholes have major problems. Most aren't traversable. Those that are require exotic forms of matter/energy that we have no reason to believe exists.

Even if the necessary ingredients did exist, the engineering, manufacturing, and economic problems would be orders of magnitude greater than even the relativistic spacecraft we have been discussing.

While it made for an interesting movie, the Sapir-Whoorf hypothesis is on pretty shaky ground.

Our thoughts don't affect physics, except in the mundane sense that your brain is connected to your body with has physical interactions with the world. Ie. you can move a glass of water with your mind by picking it up with your hand.
If you don't think of time as linear would it not affect mathematical applications applied to any natural science? Instead of calculating the probabilities and hoping you thought of every single variable you'ld be able to see all probabilities. Physics is a not a complete body of knowledge yet.
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Old 7th November 2017, 11:19 PM   #271
Roboramma
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Originally Posted by Jodie View Post
If you don't think of time as linear would it not affect mathematical applications applied to any natural science? Instead of calculating the probabilities and hoping you thought of every single variable you'ld be able to see all probabilities. Physics is a not a complete body of knowledge yet.
Okay, if you mean that you might realise something about the nature of reality by thinking about it differently then that's entirely possible, and quite mundane.

Is time non-linear? Well, that's an interesting question. There are some who think time might turn out to be an emergent property rather than fundamental, though at the moment those ideas are just interesting ideas.

Here's what Sean Carroll has to say about that:
Quote:
The question of whether time is fundamental or emergent is, on the other hand, crucially important. I have no idea what the answer is (and neither does anybody else). Modern theories of fundamental physics and cosmology include both possibilities among the respectable proposals.
But that's not really about linearity. Even if time is an emergent property of some underlying reality, it can still be modelled as a dimension of space-time in an increadibly accurate way. Is it linear within those models?

Sort of. Ignoring closed time-like curves, which don't seem to be physical, causes precede their effects. This is a consequence of the geometry of spacetime. Spacetime (and obviously this includes time) can be curved and distorted, but not to the point where time travel is possible.

There are some models where closed time-like curves exist, but first, for those hoping for time travel these are really not something that you should hope for, and these models are very different from the universe in which we exist. For instance you might require an infinitely long cylinder spinning at near the speed of light. If I remember right (no guarantee) the original model which included closed time-like curves was of a universe that was itself spinning.

Are they possible in our universe? It's hard to answer that question, but some work has been done on simpler 2+1 dimensional models and they've been shown to be impossible.
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Old 7th November 2017, 11:36 PM   #272
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Originally Posted by Jodie View Post
If you don't think of time as linear would it not affect mathematical applications applied to any natural science? Instead of calculating the probabilities and hoping you thought of every single variable you'ld be able to see all probabilities. Physics is a not a complete body of knowledge yet.
I'd like to be able to see all probabilities. How should I think of time so I can do that?
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Old 8th November 2017, 08:59 AM   #273
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Originally Posted by Jodie View Post
Other countries are working on it, and NASA too, but we are a far cry from jumping across the universe. They are looking at more mundane applications for it here on earth.
Can you cite an example of someone working on wormhole technology?
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Old 8th November 2017, 09:08 AM   #274
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Originally Posted by phunk View Post
Can you cite an example of someone working on wormhole technology?
Nasa wants to conquer WORMHOLES: Agency plans to crack unknown physics to explore beyond our solar system
Washington DC-based agency has revealed its Technology Roadmaps
These are the technologies they want to develop over the next 20 years
They include plans to research 'space warp and wormholes'



Read more: http://www.dailymail.co.uk/sciencete...#ixzz4xrCxQOvB
Follow us: @MailOnline on Twitter | DailyMail on Facebook

It's the Daily Mail, but I do recall something about NASA funding something like wormhole propulsion. I didn't care to trace down the whole story.
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Old 8th November 2017, 09:12 AM   #275
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Originally Posted by Fudbucker View Post
It's the Daily Mail, but I do recall something about NASA funding something like wormhole propulsion. I didn't care to trace down the whole story.
There was a pretty large spate of really really bad reporting concerning NASA having a warp drive project in the works back in 2012 or so. Bad reporting came from unexpected sources well outside of the Daily Mail. Quite literal science fiction was being reported as fact based on something boiled down to one three month lone maverick project.
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Old 8th November 2017, 09:20 AM   #276
phunk
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Originally Posted by Fudbucker View Post
Nasa wants to conquer WORMHOLES: Agency plans to crack unknown physics to explore beyond our solar system
Washington DC-based agency has revealed its Technology Roadmaps
These are the technologies they want to develop over the next 20 years
They include plans to research 'space warp and wormholes'



Read more: http://www.dailymail.co.uk/sciencete...#ixzz4xrCxQOvB
Follow us: @MailOnline on Twitter | DailyMail on Facebook

It's the Daily Mail, but I do recall something about NASA funding something like wormhole propulsion. I didn't care to trace down the whole story.
Well, I said working on it, not thinking about looking into it some time in the next 20 years.

NASA puts a tiny bit of it's budget into investigating far out ideas that are extremely unlikely to work, just on the off chance that one of them does. They haven't actually developed ANY wormhole technology yet. They haven't even demonstrated that wormholes can even exist yet. All they've done is say "we want to start looking into that."
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Old 8th November 2017, 09:26 AM   #277
Craig B
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Originally Posted by Fudbucker View Post
Nasa wants to conquer WORMHOLES: Agency plans to crack unknown physics to explore beyond our solar system
Washington DC-based agency has revealed its Technology Roadmaps
These are the technologies they want to develop over the next 20 years
They include plans to research 'space warp and wormholes'



Read more: http://www.dailymail.co.uk/sciencete...#ixzz4xrCxQOvB
Follow us: @MailOnline on Twitter | DailyMail on Facebook

It's the Daily Mail, but I do recall something about NASA funding something like wormhole propulsion. I didn't care to trace down the whole story.
When you do care to track it down, which would be a lovely thing to do, you will find this
But most intriguingly of all, the agency says it will support research ‘to demonstrate microscopic instances of space warp or wormholes.’
If you can find a report of NASA intending to "fund wormhole propulsion" - a very different thing - please link to your source.
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Old 8th November 2017, 09:44 AM   #278
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Originally Posted by Jodie View Post
No, you saw my post, you're bored, so you thought it was entertaining to make fun of my asking a question without doing your own homework.
You're going to prove your ability to read my mind now, rather that provide evidence of any 'wormhole technology", or my lack of doing any purported homework.

You're right. It is entertaining. Don't stop now. What homework was I assigned, and failed to do?
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Old 8th November 2017, 09:45 AM   #279
Jodie
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Originally Posted by Roboramma View Post
Okay, if you mean that you might realise something about the nature of reality by thinking about it differently then that's entirely possible, and quite mundane.

Is time non-linear? Well, that's an interesting question. There are some who think time might turn out to be an emergent property rather than fundamental, though at the moment those ideas are just interesting ideas.

Here's what Sean Carroll has to say about that:


But that's not really about linearity. Even if time is an emergent property of some underlying reality, it can still be modelled as a dimension of space-time in an increadibly accurate way. Is it linear within those models?

Sort of. Ignoring closed time-like curves, which don't seem to be physical, causes precede their effects. This is a consequence of the geometry of spacetime. Spacetime (and obviously this includes time) can be curved and distorted, but not to the point where time travel is possible.

There are some models where closed time-like curves exist, but first, for those hoping for time travel these are really not something that you should hope for, and these models are very different from the universe in which we exist. For instance you might require an infinitely long cylinder spinning at near the speed of light. If I remember right (no guarantee) the original model which included closed time-like curves was of a universe that was itself spinning.

Are they possible in our universe? It's hard to answer that question, but some work has been done on simpler 2+1 dimensional models and they've been shown to be impossible.
I still think the difficulties have to do with how we perceive how the universe works. Impossible for now, but I don't think it's impossible in the future.
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Old 8th November 2017, 09:48 AM   #280
Jodie
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Originally Posted by John Jones View Post
You're going to prove your ability to read my mind now, rather that provide evidence of any 'wormhole technology", or my lack of doing any purported homework.

You're right. It is entertaining. Don't stop now. What homework was I assigned, and failed to do?
Well I'll say this, you have the bully lesson down pat. If you aren't going to contribute to the original question that I asked about then it should be self evident. Put up or shut up John.
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