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### Re: Science-based what-if questions

Posted: Sat Feb 10, 2018 3:14 am UTC
With that much power though, it's probably more cost-effective to just used the laser to blast the air let inside the jet pack and push up that way lol. Probably only need a fraction of the cost.

### Re: Science-based what-if questions

Posted: Sat Feb 10, 2018 5:16 am UTC
Yeah, the "advantage" of photon drives is that you need very little propellant to get a lot of velocity change, since you're sending your "exhaust" at the speed of light so you don't need a lot of it, mass-wise.

The problem is, "not a lot" mass-wise is still a huge amount, energy-wise. One gram of photon exhaust is almost 10^14 J of energy.

If you put that same amount of energy into something much more massive to speed it up to a tiny fraction of the speed of light, you'd get far more thrust out of the deal.

### Re: Science-based what-if questions

Posted: Sun Feb 11, 2018 3:12 pm UTC

10^14 J of photon energy is about 334,000 kg m/s of momentum change. The payload the Space Shuttle could deliver to LEO was 27,500kg, and this amount of thrust could give that payload a measly 12 m/s of velocity change.

If instead that much energy were put all at once into a 200kg mass, it would accelerate it to 500,000m/s, for 100,000,000 kg m/s of momentum change. This means the 27,300kg (minus the projectile) remaining mass would get 3663 m/s of velocity change. That's enough to escape Earth's orbit entirely.

(That's obviously not quite the way rockets work, since they spray out exhaust as fine particles and not 200kg chunks, but the principle is the same: your energy use is much more efficient if you're willing to use up more propellant.)

### Re: Science-based what-if questions

Posted: Sun Feb 11, 2018 9:58 pm UTC
That's 23.9 kT TNT.

The distance over which that projectile, fired straight down, is going to release that energy as heat is very short.

Maybe to a molecular biologist it's a vast distance, but in terms of 23.9 kT TNT, it's Not Far Enough.

That's very slightly more than the Fat Man plutonium bomb, which made one heck of a mess.

Anything you're trying to launch with that needs a very tough back end and a very remote launch-site.

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 3:38 am UTC
Yeah obviously that's a lot of energy, that was my point.

But also I was talking about LEO, where presumably wouldn't shoot it straight down.

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 11:07 am UTC
I feel like even in LEO, pumping that much energy into the atmosphere would make something happen that would provide more impulse to the shuttle than 12 m/s.

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 1:52 pm UTC
Why are you pumping any of it into the atmosphere?

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 2:17 pm UTC
Eebster the Great wrote:I feel like even in LEO, pumping that much energy into the atmosphere would make something happen that would provide more impulse to the shuttle than 12 m/s.

Hmmm...I doubt it.

If we are talking the equivalent of a Hiroshima detonation every second: depending on the frequency of the beam, the energy will be released partly in a column of atmosphere and partly at ground level. Energy absorption will be proportional to density of the medium and considering that 99% of the atmosphere lies below 20miles altitude, not much will be happening very close to the shuttle orbiting at ~200 miles. Combine that with the empirical knowledge that ground-level bursts of up to 50megatons do not knock spacecraft about in LEO.

When a large amount of energy is dumped into a small volume of atmosphere, not much (relatively speaking) air actually gets moved very far, a large bubble of hot gas will expand and rise, and there will be energy dissipation via shockwaves, but in order to have an effect on a shuttle at 200miles altitude, an ungodly amount of mass would have to be lofted very, very high and fast, and I just dont see a mechanism at this level of energy expenditure.

gmalivuk wrote:Why are you pumping any of it into the atmosphere?

Because he really, really, really hates whoever is living on that planet?
It might not be very spectacular in the thrust department, but this engine will slag continents.
Might take a few days to do a big one, but with a little patience and a steady hand...

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 5:45 pm UTC
It also of course depends on how fast you're releasing that energy. Sure, 100TW is a lot, but I never specified that it was a gram per second. Do it slow enough and it won't be slagging anything.

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 7:58 pm UTC
gmalivuk wrote:It also of course depends on how fast you're releasing that energy. Sure, 100TW is a lot, but I never specified that it was a gram per second. Do it slow enough and it won't be slagging anything.

Naturally.
I did combine some assumptions for the sake of argument
It certainly wouldnt be much of a photon drive if it only had a 100TJ capacity and as a weapon "only" about as capable as a common-or-garden nuke, and vastly more complex and massive.

### Re: Science-based what-if questions

Posted: Mon Feb 12, 2018 11:47 pm UTC
Yeah, 100TW in a photon drive produces less thrust than a typical large airliner. Not really what you'd want to use for significant space travel.

### Complete Solid Object

Posted: Mon Mar 05, 2018 2:07 pm UTC
Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you zoom it down infinitely, and is completely take up the space in it fully 100% while still obeying the law of the universe aside from the property above. What would it like (probably the same as anything else, I guess), and what would you do with it?

### Re: Complete Solid Object

Posted: Mon Mar 05, 2018 2:21 pm UTC
andykhang wrote:Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you scale it down infinitely, and is completely take up the space surrounding it fully 100% while still obeying the law of the universe aside from the property above. What would it like (probably the same as anything else, I guess), and what would you do with it?

Aside from some peculiar wording (atop of the peculiar scenario), sounds to me like it's a kind of 'exclusionary field'. Imagine Rutherford/Thompson/et al sending electrons into the 'thing', and finding they all bounce back, because there's not just the odd and sparse pinhead-atom getting in the way but all the throughout the 'thing', or at least all across its surface, it is always in the way and nothing gets through by shear luck or internal pinballing. EM radiation likewise.

Or else not at all, for some interactions, and therefore not visible/tangible/whatever. According to which interactions are lacking rather than absolute. There surely couldn't be partiality to the strong-force, for example. It either applies homogeneously or not at all. Same with the others. Different mixtures of which aspects work and which don't could make for different interesting materials. But probably very odd, in all cases.

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 2:34 pm UTC
So for example I want to make an Infinitely Sharp Sword with this thing, what kind of property should it have?

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 2:59 pm UTC
It already is infinitely sharp. It can cleave through physical reality.

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 3:02 pm UTC
Yeah, but what if it's perfectly round? Is it going to roll reality to death?

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 3:08 pm UTC
The point is that you're already breaking reality, so physics won't really tell you what happens as a result.

You're talking about magic, which is a fine thing to talk about but not a reasonable thing to expect reality-based science to tell you much about.

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 3:23 pm UTC
Let's say I am made of cells. What holds my cells together? Electromagnetism. If my skin encounters something that has an edge which eliminates the functioning of electromagnetism, it will rip through me. And you are postulating an object which occupies space and obviates electromagnetism. So it is sharp, regardless of shape.

I would miss electromagnetism. I would apologize for all the mean things I've said about Jackson.

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 3:31 pm UTC
Wait, but what do you mean my CSO is infinitely sharp?

### Re: Complete Solid Object

Posted: Mon Mar 05, 2018 4:12 pm UTC
andykhang wrote:Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you zoom it down infinitely, and is completely take up the space in it fully 100% while still obeying the law of the universe aside from the property above. What would it like (probably the same as anything else, I guess), and what would you do with it?

What properties would you like it to have?

### Re: Science-based what-if questions

Posted: Mon Mar 05, 2018 8:53 pm UTC
How does thermodynamics function with continuous matter?

### Re: Complete Solid Object

Posted: Tue Mar 06, 2018 7:18 am UTC
p1t1o wrote:
andykhang wrote:Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you zoom it down infinitely, and is completely take up the space in it fully 100% while still obeying the law of the universe aside from the property above. What would it like (probably the same as anything else, I guess), and what would you do with it?

What properties would you like it to have?

Well then, I want it to have a wish-granting property and wished for it to turn into a laser gun that turn anything to gold and sell for profit .

Jk aside, probably that it could split infinitely while still holding it original property? Basically an object lacking emergent property. Or probably something that is topologically constant , so kinda like a universal play-doh.

As for thermodynamic, probably very cold, if that thing is a giant sort-of atom (as in doesn't split) that obeying the universal version of square-cube law. Or probably something that could spread it heat evenly everywhere even when touch at one place, as this thing reach the state of equilibrium almost infinitely fast.

### Re: Science-based what-if questions

Posted: Tue Mar 06, 2018 9:01 am UTC
On the other hand, it may be incapable of radiating away heat, and without discrete particles it may not conduct heat very well either.

Temperature is a measure of the external/internal kinetic energy of the particles within a system, with only one particle this changes things dramatically.

What happens to EM radiation that hits it? Is it absorbed? Reflected? All the usual mechanisms for these things are absent. It is more of a defect in space-time than a physical object. Without electrons, interaction with a large portion of the EM spectrum might be non-existent - without particles of any kind, it may not interact at all.

The question "What happens to a photon/a photon's energy when it hits a solid, continuous wall of force?" doesnt make any sense and all answers are equally valid/invalid.

Does it contain Higgs bosons? Does it have mass/inertia? Does it obey F=ma? KE=1/2mv2? Is it attracted by gravity?

There is no reason to expect it to have any of the properties of normal matter whatsoever. In terms of real science it is very hard to assign it any properties.

### Re: Science-based what-if questions

Posted: Tue Mar 06, 2018 11:21 pm UTC
andykhang wrote:So for example I want to make an Infinitely Sharp Sword with this thing, what kind of property should it have?

You're describing RayShade solids and making them physical.

A simple sword blade is the sum of {the overlap of two ellipsoids} and {the overlap of two cylinders and a cuboid}. Imagine two 300x200x10 ellipsoids in parallel, 4 apart. Where they overlap is only 2 thick, quite wide and very long, and has infinitely sharp edges. That's your point. Behind it you have the overlap of a cuboid to give determined length with two infinityx200x10 ellipsoids (elliptical prisms?) to make a straight section of blade. Then you have a (bronze-coloured, to be classy) ellipsoid with its major axis perpendicular to the blade as a hand guard, a bronze-coloured sphere as a pommel, a grey ellipsoid combined with a lot of tiny grey spheres centred on its surface for a grip (because this thing would be too smooth to hold otherwise) as a grip and probably some lead trapped inside it to give it mass and balance.

Your sheath is the difference between a larger, wider copy and a merely wider copy, so you get a slot down the middle where the blade fits without the sharp parts touching. You'd probably want to tie it in, or have a pop-fit (using the famous light elastic strings).

Note that you can't just put a handle on a long, narrow triangle and use that as a sword because it would have zero resistance to motion edgeways and thus deflect and go edgeways, creating no separation of anything at all. Sure, you could swing it through your opponent's shield, arm, armour and body but it wouldn't even break a protein, let alone sever a limb, on the way through.

You want to know what I'd build out of that stuff? A bicycle. A lightweight, indestructible, totally corrosion-proof, bicycle, with really, really fine chainmail in the tyres. When the rubber wore out, I'd swap the (totally intact) chainmail for some new tyres with chainmail in, and the tyre company would cast new tyres over the (old but totally intact) chainmail again and again and again.

Also a deHavilland Mosquito, or one of the photo-recon Spitfires. You've got a way to make a frictionless engine that doesn't need oil and an aircraft with no rivets or anything to spoil the airflow and no mass. You're going to have the most amazingly efficient flight ... if you can get past that one small problem that in the original Spitfires, opening the throttle past about 35% for take-off would pull the aircraft over onto its nose. The bicycle wouldn't have that problem.

### Re: Science-based what-if questions

Posted: Wed Mar 07, 2018 3:47 pm UTC
Continuing from the thermodynamic thing, if that thing is a continuous wall of force, then by the quantum field theory, it's probably better to considered it a giant, very simple "wave" of matter, instead of just a collection of loosely connected wave. A giant point energy with all it force interaction pushed toward outside, or basically a whitehole, IMO.

In that case...yeah, still haven't solve anything, but at least it made it easier to visuallize the energy aspect of it. Were it's just a giant wave of matter, it wouldn't have it state change easily by the interation with all the particle around it, just by the virtue of it size, IMO.

### Re: Science-based what-if questions

Posted: Wed Mar 07, 2018 6:12 pm UTC
What, no, don't do "by the quantum field theory." QFT has nothing to do with this. You are postulating some non physical nonsense, there are no conclusions that QFT would have about it.

It would just let you do your QFT in the rest of the world with some weird boundary conditions on a weird shaped boundary, if you wanted to do that. Though you are probably violating causality everywhere if you do this. It is not just some parochial nonsense.

### Re: Science-based what-if questions

Posted: Thu Mar 08, 2018 10:30 am UTC
Well, I'm just trying to put this thing into a context where physics as we known it could still sorta work, and that's just one of the thing that could do it.
And beside, IMO, you definitively need QFT for the whole "continuous wall of force" thing to work, as this thing could be basically a giant quantum particle interact with countless particle surrounding it.

### Re: Science-based what-if questions

Posted: Thu Mar 08, 2018 4:59 pm UTC
What do you think "a giant quantum particle" means, and how do you think quantum field theory would represent this?

### Re: Complete Solid Object

Posted: Thu Mar 08, 2018 9:58 pm UTC
andykhang wrote:Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you zoom it down infinitely, and is completely take up the space in it fully 100% while still obeying the law of the universe aside from the property above.

I think a more interesting question is how could this theoretical object potentially be created?

### Re: Complete Solid Object

Posted: Thu Mar 08, 2018 10:14 pm UTC
Ranbot wrote:
andykhang wrote:Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you zoom it down infinitely, and is completely take up the space in it fully 100% while still obeying the law of the universe aside from the property above.

I think a more interesting question is how could this theoretical object potentially be created?

A black hole? Where the point of singularity is a cube 1x1x1?
(Thatâ€™s what I imagine this to be)

### Re: Science-based what-if questions

Posted: Thu Mar 08, 2018 10:34 pm UTC
That is not a black hole. Black holes are real things, with real properties, and they are not like this.

I am not trying to be some kill joy here. I think if you think about things like black holes, you will not lack for joy. They are pretty great. I promise. But maybe I am also kind of bitter and my entire presence in this thread is purely for some Old Man Yells at Cloud action. Maybe don't mind me. But look, i promise general relativity and quantum field theory are actually fun.

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 8:13 am UTC
You cannot have a single giant particle in this universe. You cannot push multiple matter particles together as close as you like, either. The closest you can compress matter (without converting it into something else) is what you'll find in a neutron star.

https://io9.gizmodo.com/5805244/what-wo ... -do-to-you

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 9:23 am UTC
Matter is one thing this object certainly is not.

***

On a related note, in Alastair Reynold's "Revelation Space" series of books, the BigBad is an alien machine race that is composed of replicating cubes of "pure force" with a description closely matching this object - no particulate matter, solid "walls" of force no matter how far down you zoom, impenetrable, little in the way of interaction with normal matter.
It is referred to as "femtotech", implying that their manipulation of matter has progressed so far that they can manipulate it on a sub-nucleonic scale.
Obviously this doesnt provide any real-world insight, Im just saying its come up before.
One thing Alastair didnt do is try and assign it much in the way of fancy material properties or try and explain where it came from, it represents "technology so advanced it is indistinguishable from magic", which is about the only way one can sensibly treat this.

In the books, one of the only ways to effectively combat them (immune to most conventional weapons) is to use devices that "delete" volumes of space-time ("bladdermines", "hypometric" weapons)

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 2:20 pm UTC
Of course it ain't. That thing is more closer to a singularity than any definition of matter applicable to us. And thing start to get weird even near a singularity, not to mention touching it.

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 2:32 pm UTC
andykhang wrote:Of course it ain't. That thing is more closer to a singularity than any definition of matter applicable to us. And thing start to get weird even near a singularity, not to mention touching it.

Name one similarity between a singularity and this force-object?

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 2:38 pm UTC
Well beyond even Anathem's "newmatter", as well.

(fake-edit upon ninja: not responding to the specific singularity stuff, just the general oddnessâ€¦)

### Re: Complete Solid Object

Posted: Fri Mar 09, 2018 3:44 pm UTC
Ranbot wrote:
andykhang wrote:Supposed they're exist a Complete Solid Object: An object that you will find no gap, no matter if you zoom it down infinitely, and is completely take up the space in it fully 100% while still obeying the law of the universe aside from the property above.

I think a more interesting question is how could this theoretical object potentially be created?

Maybe this would be really close to this theoretically completely solid object... Collect a sample of pure neutrons, chill to absolute zero, and place them under extreme pressure to pack them all together as closely as possible.

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 4:24 pm UTC
p1t1o wrote:
andykhang wrote:Of course it ain't. That thing is more closer to a singularity than any definition of matter applicable to us. And thing start to get weird even near a singularity, not to mention touching it.

Name one similarity between a singularity and this force-object?

The "infinite dense-ness" part, even if it's abit of a technicality, as you won't find "space" between any of the interacting part of the object itself.

### Re: Complete Solid Object

Posted: Fri Mar 09, 2018 4:50 pm UTC
Ranbot wrote:
Maybe this would be really close to this theoretically completely solid object... Collect a sample of pure neutrons, chill to absolute zero, and place them under extreme pressure to pack them all together as closely as possible.

If you're still talking neutrons, theres plenty of free space, even if they are "touching".
Squeeze them much further and boom, quantum singularity.

No infinitely smooth and complete "walls of force".

andykhang wrote:
The "infinite dense-ness" part, even if it's abit of a technicality, as you won't find "space" between any of the interacting part of the object itself.

Why would it be infinitely dense? Its not made of matter, theres no reason to assume it has any mass.

This is a thought experiment gone wrong by reason of infinite extrapolation.

### Re: Science-based what-if questions

Posted: Fri Mar 09, 2018 6:42 pm UTC
And if it is infinitely dense, then what you have is an actual black hole, not a "completely solid object", and it would behave the ways black holes behave.