Science-based what-if questions

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andykhang
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Re: Science-based what-if questions

Postby andykhang » Wed Jan 31, 2018 10:56 am UTC

I see someone comment it would, so I assume it. Either way, yeah, no way in hell it stop being a charge particle of death for any unlucky type .7 civilization. Top of my head, probably a planet cracker.

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Re: Science-based what-if questions

Postby gmalivuk » Wed Jan 31, 2018 10:33 pm UTC

In order to crack a planet it has to transfer some of its energy into the planet. How is that supposed to happen in this scenario?
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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 2:31 am UTC

It’s a charge particle going at the speed of light and carrying a solar mass worth of kinetic energy. Basically, I would be surprise if that thing wouldn’t completely annihilate a row of atom of more than 6000 km high and into a column at least 1 m wide of instant particle destruction at the point of impact.

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Re: Science-based what-if questions

Postby morriswalters » Thu Feb 01, 2018 2:41 am UTC

What is the maximum KE an electron can have?

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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 4:02 am UTC

Does it matter? It's not like it's going to decay any time soon.

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Re: Single Electron Disaster

Postby DaBigCheez » Thu Feb 01, 2018 4:07 am UTC

andykhang wrote:What happen if you concentrate all the energy the Sun have to accelerate a single electron? Would it become a black hole traveling at near-light speed?

andykhang wrote:It’s a charge particle going at the speed of light and carrying a solar mass worth of kinetic energy. Basically, I would be surprise if that thing wouldn’t completely annihilate a row of atom of more than 6000 km high and into a column at least 1 m wide of instant particle destruction at the point of impact.

If you already knew what the only answer you're prepared to believe is, what's the necessity of asking a question in the first place?
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Re: Science-based what-if questions

Postby gmalivuk » Thu Feb 01, 2018 4:12 am UTC

andykhang wrote:
It’s a charge particle going at the speed of light and carrying a solar mass worth of kinetic energy.
It's got the charge of one single electron and doesn't have any easy way to transfer much of that kinetic energy to anything around it.

Basically, I would be surprise if that thing wouldn’t completely annihilate a row of atom of more than 6000 km high and into a column at least 1 m wide of instant particle destruction at the point of impact.
By what mechanism will it do this?

I don't care what would surprise you, I care what would surprise someone who knows about physics.
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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 4:20 am UTC

And the KE of a single solar mass, mind you. Any number that big would give out big number regardless of the property of that single electron. That thing will definitively gone pass the Pauli's Exclusion Principle and the Strong force and smash any proton and neutron in it way, no matter how you cut it. Honestly, I'm more interest in the resulting's temperature and heat.

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Re: Single Electron Disaster

Postby andykhang » Thu Feb 01, 2018 4:25 am UTC

DaBigCheez wrote:
andykhang wrote:What happen if you concentrate all the energy the Sun have to accelerate a single electron? Would it become a black hole traveling at near-light speed?

andykhang wrote:It’s a charge particle going at the speed of light and carrying a solar mass worth of kinetic energy. Basically, I would be surprise if that thing wouldn’t completely annihilate a row of atom of more than 6000 km high and into a column at least 1 m wide of instant particle destruction at the point of impact.

If you already knew what the only answer you're prepared to believe is, what's the necessity of asking a question in the first place?


I'm asking for specific, as I'm not that good as physics. That thing would smash through any particle, sure, but I'm not sure if the resulting's heat would be enough for what I said later after that.

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Re: Science-based what-if questions

Postby gmalivuk » Thu Feb 01, 2018 5:07 am UTC

andykhang wrote:And the KE of a single solar mass, mind you. Any number that big would give out big number regardless of the property of that single electron. That thing will definitively gone pass the Pauli's Exclusion Principle and the Strong force and smash any proton and neutron in it way, no matter how you cut it. Honestly, I'm more interest in the resulting's temperature and heat.
Okay, so it smashes every nucleus it runs into. But it's still an electron, and thus still very very small, so it only runs into nuclei in an electron-width path through the Earth, which is not enough to worry about on a global scale.

You're still missing the fundamental fact that however much energy the electron has, it must transfer that energy to the Earth in order to damage the Earth, and you haven't given any explanation for how it transfers that energy beyond the fact that it runs into a few nuclei.
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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 5:15 am UTC

Mind you, it run into the nuclei of every single atom in the long, 6000km+ column of matter it have to travel through, and that atom would be completely toast if a single electron just smash through it core like bullet through sheet of paper anyway.

The energy from just destroying the atom alone though is barely that of an asteroid, I admit. The resulting's heat and temperature rival that of the very beginning of the Big Bang itself would make thing very different though.

Edit:...Though, even if the heat is Big Bang level, the resulting particle that come out of it would only destroy around a million atom worth of width from the center of impact as best. And since i'm still assume relativity still work, no amount of time would be enough for that heat also to destroy the electron particle itself before it safely pass through the Earth, I assume.
Last edited by andykhang on Thu Feb 01, 2018 5:37 am UTC, edited 1 time in total.

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Re: Science-based what-if questions

Postby gmalivuk » Thu Feb 01, 2018 5:35 am UTC

Earth is about 13,000,000 meters in diameter, but an electron is about 10^-15 meters in diameter. Even if it annihilates (not just cracks the nucleus of every atom, but actually turns it into pure energy) everything within a full nanometer (which, remember, is a million times bigger than the electron itself), that's a volume of 13,000,000*pi*.000000001^2, or 0.00004 mL. That amount of iron is 0.0003 grams, and converted entirely to energy is the equivalent of about 6 tons of TNT stretched all the way through the planet.

It's a linear energy density of 1 gram of TNT per two meters.
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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 5:40 am UTC

Yeah...and the resulting heat also probably didn't do much of anything either. It's just too darn fast for both the Earth and the electron itself to feel anything, for completely different reason. (Not that sure if the electron truly doesn't feel anything, even from the heat that should undermine it own force that support it)

Wow...that's abit more dissappointing.

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Re: Science-based what-if questions

Postby Soupspoon » Thu Feb 01, 2018 6:58 am UTC

It's very much in the manner of a large amount of not very much at all, leaving one to have to work out at what sort of balancing point does that become significant in 'normal' terms.

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Re: Science-based what-if questions

Postby cyanyoshi » Thu Feb 01, 2018 7:53 am UTC

What kind of magnetic effects could you expect from an electron travelling that quickly through Earth? Would that be enough to do any additional damage?

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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 8:27 am UTC

Not that much really, this thing's charge is still that of an Electron.

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Re: Science-based what-if questions

Postby Soupspoon » Thu Feb 01, 2018 8:47 am UTC

andykhang wrote:Not that much really, this thing's charge is still that of an Electron.

A charge moving at whatever speed we decided it had to move to have the energy specified. A magnetic field generation from a very very little electric field moving very very fast.

A fleeting but (potentially) high-spiking event. It'd be an anomoly, certainly. But not sure about how significant it would be to detectors at various distances or in other physical manefestations. (Rather than directly running into any significant amount of baryonic matter, I'd expect some 'shockwave' effects. But hugely significant or practically imperceptible?

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Re: Science-based what-if questions

Postby andykhang » Thu Feb 01, 2018 9:09 am UTC

...Really, why the hell that the faster you go, the more stable you're anyway?

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Re: Science-based what-if questions

Postby Soupspoon » Thu Feb 01, 2018 9:19 am UTC

andykhang wrote:...Really, why the hell that the faster you go, the more stable you're anyway?

Can you rephrase that? It doesn't seem to be in reply to me, but I'm the only person you can be replying to, unless it's an older part of the thread that you're revisiting..

(Of course, a very very very fast object, w.r.t. to an observer, is observed as experiencing significant time-dilation, so a natural decay-rate would be seemingly attenuated. That isn't something I mentioned, but if it's actually an answer then I may have saved an iota of time.)

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Re: Science-based what-if questions

Postby Eebster the Great » Thu Feb 01, 2018 11:26 am UTC

By my calculations (which may be very wrong), the electron would be travelling at 0.999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 999 90 c = (1-10-121) c, with a rapidity of 140. From the electron's reference frame, the Earth would be only 5.7 * 10^-54 m thick (3.5 * 10^-19 Planck lengths), so the electron would only remain inside it (assuming it was not significantly slowed) for 1.9 * 10^-62 s (the same number of Planck times).

So it's not surprising that there is no significant interaction. It's hard to imagine anything much happening in less than a quintillionth of one Planck time. I'm not even sure it would smash the nuclei it flies through.

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Re: Science-based what-if questions

Postby p1t1o » Thu Feb 01, 2018 11:47 am UTC

But from the Earths perspective, the electron take about a twentieth of a second to pass through, and while it does, it is under the influence of a solar mass worth of gravity at very close proximity.

So there is some scope for interaction, no?

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Re: Science-based what-if questions

Postby gmalivuk » Thu Feb 01, 2018 4:13 pm UTC

Yeah space will curve in weird ways as it passes though it won't curve the same way it would if it were a stationary solar mass.

(The hyperrelativistic motion means it's nothing like the static Schwarzschild solution most people refer to when discussing whether some configuration of matter becomes a black hole.)

Edit: Which is to say, doogly is probably wrong with
doogly wrote:No it doesn't, that is a very reasonable situation, entirely within known science.

The electron would just be going very fast.

Like, yes, the electron would be going very fast, but that "just" is only appropriate with a physically meaningful solution to the field equations for something moving this fast (and even then the size means quantum gravitational effects are probably relevant even if relativity on its own has something nice and clean to say about it).
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Re: Science-based what-if questions

Postby doogly » Thu Feb 01, 2018 5:07 pm UTC

It's a lot like the static schwarzschild solution, just a Lorentz shifted version.

I mean if you want to model the electron somehow getting from rest to that speed, you'd have a lot of splainin to do, because this is a bunch of ridiculous nonsense. But if you just want an electron to be moving at that speed, Lorentz can get you there for cheap.

The gravity of such a thing is totally normal. No worries on that front. I mean, instead of saying "don't worry about QG near the event horizon, start worrying O(planck length), maybe you start worrying O(electron compton wavelength)? That's probably fair to worry about. But it's still inside the schwarzschild radius, so.

So then you just have a question of a relativistic electron, which is answered with QED. That has ways to handle the diverges. It's fine with v/c = .9, or .99alotof9s. You may have to actually *DO* more of the loop calculations, but they converge. QED is a mighty fortress.
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Re: Science-based what-if questions

Postby p1t1o » Thu Feb 01, 2018 5:53 pm UTC

I presume that there will be a frame-dragging effect as it passes as well, that ought to have some impact on Earth's fabric as well, yes?

Given that the total gravitational binding energy of the Earth is 1 ten-thousand-billionth of the energy of this electron, I would wager that if there is any interaction at all, Earth is gas.

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Literal Manhattan Project.

Postby andykhang » Sat Feb 03, 2018 3:20 pm UTC

Suppose that I want to transform the Manhattan Island into a floating warship, capable of sailing around the world and be a literal world threat. What kind of requirement would it need, and how would you build this? (Asking, because one of the novel I read climax at the end with this thing, that also carrying a weapon that's essentially nuclear fusion weapon in a shape of an cannon)

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Re: Science-based what-if questions

Postby Sableagle » Sat Feb 03, 2018 6:56 pm UTC

You'd need to divert the Hudson, move everything off Manhattan, dig Manhattan out to considerable depth, build a hull there, install engines, dig a channel out to sea, move everything back onto the hull and then allow the Hudson back into its course to float the thing.

Manhattan's rock, and rock generally sinks.
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Re: Science-based what-if questions

Postby morriswalters » Sat Feb 03, 2018 8:03 pm UTC

Invent the Spindizzy.

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Re: Science-based what-if questions

Postby Soupspoon » Sat Feb 03, 2018 8:50 pm UTC

I'd go for a deep, deep quarry, removing as much material as I possibly could whilst not extending beyond the 'edges' of the island, and applying a spraycrete-type lining (like in certain tunnels) plus some variety of steel-or-better buttresses. If I could remove the buildings as well, that'd be useful (at the cost of removing the 'character' of the place), but if I were forced to keep the ground as well (such as the sculptured 'nature' of Central Park) then maybe do it as a cavernous subteranean quarry-mine with cathedral-like buttresses left in place to support the vault-like roof (and some thought of how to accomadate or replace the bedrock-pilings used by the various buildings, plus a thought to balancing the remaining mass in all orientations).

Then, working from the river-bed and/or from a deep air-lock deep in the bowels of our mined-out void, punched through the lowest-most extent of our mica-schist (or whatever is below that) 'hull', tunnel beneath the island in many, many closely parallel ribs, carefully allowed to flood (during/after tunelling, which might require a particularly specialised TBM, or rather a lot of them) while a myriad of strain-guages and laser-reflectors monitor ground movements allowing us to apply additional strategic jacking bracing, and then finally coordinate the cutting between the under-hull rib-tunnels (same TBMs, if they'd been initially deployed at less than a tunnel-width separation in their original phase?).

Much of the strength of the 'hull' would have to be artificial bracing (not the brittle rock itself) and most of the waterproofness of the hull would have to be our lining (not the fracture-prone rock itself) and the mass/volume of the removed rock would have to be considerable to equalise the weight of the remaining rock+superstructure as pretty much that of the water it would now be effectively displacing for buoyancy (building up the waterfronts, in the manner of the DD Tanks and perhaps with material somehow processed from some of the extracted rock, would mean less hull needs digging out, but then a greater amount of below-hull removal is required to let the structure settle down low, and still also needs advanced bracing/load-distribution against the water-pressure), and yet it might not be totally into the territory where unobtanium is needed.

It would be easier, of course, to just build a separate metal hull the size and shape of Manhattan, perhaps initially as a shallow shell of a hull supported by retractable piling in a nearby esturine area that can be lowered once it is built up enough, then built up further evenly around the edge once towed into deeper (but sufficiently sheltered) waters, and recreate all the required features of Manhattan (landmark buildings, surfsce topography) as braced lighter-weight alloy just to pretend that it is the original island. Rob Manhattan's buildings of their external stone cladding, perhaps, to do a kind of Boat Of Theseus variant, demolishing and abstracting whatever is not transfered to make it memetically obvious that the only actual Manhattan is now the one upon this new hull.


I have not, of course, consulted any geological sources, nor performed sufficiently extended surveys of my own, to determine the exact extent of hulling-out required. Nor consulted metallurgical tables to determine the best configuration (probably multi-compartmentalised cellular construction, to tight tolerances) or composition of the doppleganger 'island' boat. The tendering document lacks pretty much any of the detail one really needs in order to start calculating how much non-hull mass needs supporting… ;)

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Re: Science-based what-if questions

Postby Sableagle » Sat Feb 03, 2018 11:30 pm UTC

https://www.quora.com/How-many-tons-of- ... o-make-NYC

Well, There's approx. 33.77 sq. mi in manhattan alone, so for the sake of our math, let's use that number. If each building has footings that go approx. 10 yards deep (assuming an average here, I can't go building by building and figure out how deep each one's footings go) Then we multiply by the square yards of 33.77 sq. mi (around 1.04606e+8 sq. yards) which gives us 1,046,060,000 cu. yards. Each cubic yard weighs approx. 4,000 pounds (2 tons) So, multiply 1,046,060,000 (the total cu yardae of concrete) by 2 (the number of tons per cu. yard) and that gives us 2,092,020,000 tons of concrete. If someone could double check my math, that'd be great, but I feel like I'm in the ballpark here.


https://www.thrillist.com/culture/how-m ... ttan-weigh

... 705,900,000 pounds—or 352,950 tons—of people meat.
... 3,000 tons of pure animal.
... 702,100 cars ... 1,158,465 tons. ... buses ... 25,100 tons. ... 450 35-ton dump trucks (31,500,000 pounds/15,750 tons).
... 6,384 subway cars ... 121,296 tons. ... 1,200 trains ... and 700 ... 1,073,500 tons.
... 2,394,111 tons.
.508.38 linear street miles ... 3,170,000 tons of asphalt. If we say the sidewalks are four inches thick, we get 1,006,000 tons of sidewalk. Total here: 4,176,000 tons.
... I looked at the Empire State Building, which weighs 350,000 tons. I looked at the average house, which weighs 70 tons. ... 118,159,600 tons of buildings.

But if every building was empty and no one had any possessions besides cars and pets and food? Manhattan would still weigh at least…wait for it…125,208,467 tons. That’s 250,416,934,000 pounds. The more you know, right?


They're within two orders of magnitude. I think the first guy's overestimated how much of the island is ten-foot-thick concrete footing.

Google says that's 113587210.581194 tonnes, which is 110386016 cubic metres of seawater. Manhattan is 59.1 km², so that's a piffling 1.87m of extra draught. You'd probably want to make the hull bigger than the island, just to get a sensibly sleep outline.

Two further questions to consider:

What do you do with the bridges and tunnels?

How are you going to move this thing? One 30 MW nuclear submarine propulsion engine would take a full hour to get that mass up to ...
... 1.38 millimetres per second.
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Re: Science-based what-if questions

Postby Eebster the Great » Sun Feb 04, 2018 1:27 am UTC

You don't have to do these sorts of estimates if you know the mean density of the rock under Manhattan Island. From that figure, you can readily get a pretty accurate estimate of the volume of rock you need to excavate and replace with air to make the island buoyant. Granted, that depends on the depth of the proposed vessel. If the vessel is not very deep, then you will need to account for the enormous mass of concrete, asphalt, steel, glass, etc. built on top of the island (unless you propose to remove it). But that will never add too much anyway; maybe an extra few feet (yards?) of excavation. Most of the mass is bedrock, at the end of the day.

The challenge comes from excavating cubic miles of rock (mostly submarine), finding a place to put it, and putting it there. All of those are pretty much impossible in the foreseeable future, but not completely impossible full stop. The other challenges address why you would ever want to do something like that.

Also, most bedrock is only moderately strong, so your island would break apart immediately after launching (actually, long before then). The challenge of holding everything together might be more difficult than the challenge of building the ship in the first place, since I'm not convinced any material can feasibly accomplish the task, given the strict weight limits.

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Re: Science-based what-if questions

Postby andykhang » Sun Feb 04, 2018 4:56 am UTC

Well, the novel I'm talking about isn't exactly hard scifi, so you bet they have some mean to move and reinforce the thing (heck, they're used to build massive weapon, that's practically 2 times heavier than a CV, run at 500 km/h, is about 200m tall, run by a nuclear fusion reactor and could survive a nuke).

Also, in that novel world, they won't have any hesitation about completely replacing the landmass of manhattan with something like this, just like they don't have any problem building this ridiculous thing in the first place.

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Re: Science-based what-if questions

Postby morriswalters » Sun Feb 04, 2018 5:29 am UTC

Rebuild Manhattan on an iceberg in Antarctica. You figure out how to propel it. Ice appears to have better structural properties than basalt, and likely steel if you can keep it cold. Oh yeah, stay in deep water since the depth of the keel won't allow you close to the coast. The berg created by the break on the Larson ice shelf was on the order of 5800 km2. Manhattan is somewhat smaller. James Blish had a somewhat better idea, fly it off into space. Bon voyage. Read better science fiction.

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Re: Science-based what-if questions

Postby Sableagle » Sun Feb 04, 2018 9:36 am UTC

andykhang wrote:heck, they're used to build massive weapon, that's practically 2 times heavier than a CV, run at 500 km/h, is about 200m tall, run by a nuclear fusion reactor and could survive a nuke.
Mechwarrior.

Spoiler:
Battlemechs.

These things:

Image

Image

The drop-down on the guns on the first one and the cockpit position and design on the second? Your world has bigger issues than how to shove Manhattan out to sea.

This design makes more sense:

Image

... but not as much sense as these:

Image
Image
Image
Image
Image
Image
Image
Image
Image

Observe the changes from these:

Image
Image

... via these:

Image
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... to these:

Image
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Sloping armour, hatches at rear, driver behind the engine in the Merkava so anything that gets through the front armour has to get through the engine too to reach him or her (Do the IDF have female tank drivers? Apparently yes, for a few weeks now.), armament at the top so it can shoot over hard cover, low profile and in precisely no cases one of THESE:

Image

... sticking out at the front just to make it look cool.


The only answer from Mech fans to any of those criticisms has been "In the battlemech world, giant robots are better."

You may as well cover Manhattan in tethered blimps and use them to hold it up.
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Re: Science-based what-if questions

Postby Eebster the Great » Sun Feb 04, 2018 11:06 am UTC

Now hang on there for a moment. It sounded like you were suggesting that Mech Warrior was not entirely realistic.

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Re: Science-based what-if questions

Postby andykhang » Sun Feb 04, 2018 12:34 pm UTC

TBH, what they built is more like giant ball of steel, with propulsion for feets, large cannon on the side and small one porcupining the whole thing, so at least it's more "realistic" than tank with bipedal.

Still ridiculous though.

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Re: Science-based what-if questions

Postby Soupspoon » Sun Feb 04, 2018 2:35 pm UTC

Sort of reminds me of https://en.wikipedia.org/wiki/Mortal_Engines … Only at sea?

Is https://en.wikipedia.org/wiki/Inverted_World less fantastic? (At least within the immediate vicinity of the city, if you don't try to make sense of what the Sun looks like, and why it would, and stuff like that...)

andykhang
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Laser jetpack

Postby andykhang » Fri Feb 09, 2018 2:07 pm UTC

Supposed that I want to built such a thing. How many Terawatt of light do I need to propel myself with just light alone?

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doogly
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Re: Science-based what-if questions

Postby doogly » Fri Feb 09, 2018 2:37 pm UTC

The momentum of light is E/c. Force is dp/dt, or power/c. If you want your weight to be supported by the light, you need a power of weight*c. So under a terawatt, actually.

This is with only one coffee in me though, don't hold me to it.
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Re: Science-based what-if questions

Postby p1t1o » Fri Feb 09, 2018 3:32 pm UTC

doogly wrote:The momentum of light is E/c. Force is dp/dt, or power/c. If you want your weight to be supported by the light, you need a power of weight*c. So under a terawatt, actually.

This is with only one coffee in me though, don't hold me to it.


You got it, project rho confirms. It works out to about 300MW per Newton of force. Or about 300GW to acclerate 100kg at 1G.
The biggest problem with this is its very difficult to emit a directional beam of photons without a decent proportion of waste heat.
So even if your drive is 99% efficient, you need to dump 3GW of heat to prevent your ship from vaporising.

FYI that requires a radiator running at 1000K with an area of 66,000m2.

A reasonable area-density for a radiator is 10kg/m2 but lets pretend ours is bleeding-edge tech and comes in at 1kg/m2.

The radiator masses 66tons and now you are accelerating at 0.015m/s2 or 0.0015G.

And that is a highly optimistic estimate, quite apart from the 99% efficiency and (very) lightweight radiator we still dont have a power source, or anything else with mass.

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Eebster the Great
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Re: Science-based what-if questions

Postby Eebster the Great » Fri Feb 09, 2018 10:24 pm UTC

Right, that's 300 GW of optical power, which I think is like a million times more powerful than massive weaponized lasers. Apart from the challenges of generating terrawatts of power continuously in a backpack or dumping similar quantities of heat through the surface of a backpack into air, you would also have to worry about obliterating everything below you to significant depth.


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