Search found 360 matches

by stoppedcaring
Wed May 07, 2014 8:36 pm UTC
Forum: Fictional Science
Topic: Atmosphere Planet
Replies: 15
Views: 6894

Re: Atmosphere Planet

the average isn't relevant, though. you might want to read http://en.wikipedia.org/wiki/Atmospheric_escape That's a relevant factor in the upper atmosphere, but not so much at STP. According to this paper , the Maxwell distribution of N 2 and O 2 at 300K pretty much tapers off to nil at around 1 km...
by stoppedcaring
Wed May 07, 2014 6:51 pm UTC
Forum: Fictional Science
Topic: Atmosphere Planet
Replies: 15
Views: 6894

Re: Atmosphere Planet

that can't be true. for one thing, escape of gas does not depend on rotational speed, but on temperature. the gas would boil away even at normal temperatures, and your posited collapse would, as you wrote, generate a lot more. The speed of gas molecules at room temperature is only around 500 m/s, w...
by stoppedcaring
Wed May 07, 2014 6:33 pm UTC
Forum: Fictional Science
Topic: Atmosphere Planet
Replies: 15
Views: 6894

Re: Atmosphere Planet

I took the opposite approach. Assuming that you mean atmosphere at sea level, we'd be looking at converting the present average density of Earth (5,513 kg/m 3 ) to a density of 1.2754 kg/m 3 , meaning the Earth would suddenly lose 99.977% of its mass. Instead of being six million billion billion ton...
by stoppedcaring
Wed May 07, 2014 4:01 pm UTC
Forum: Science
Topic: 1338 changed my life! (veganism)
Replies: 153
Views: 22927

Re: 1338 changed my life! (veganism)

I get the thing about free range animals and whatnot, but I'm not sure why in-season produce is important. Out-of-season foods cannot be purchased locally; they have to be shipped in from far away. That's a problem, because things have to be picked earlier (lower overall nutrient profile) and tend ...
by stoppedcaring
Wed May 07, 2014 3:55 pm UTC
Forum: Serious Business
Topic: Encode a message so it can't be read until a certain time?
Replies: 84
Views: 55012

Re: Encode a message so it can't be read until a certain tim

If I try to channel my inner Randal and answer this "what if" style, I would tell you to forget about "encoding": Send that sucker on a planetary journey (especially around the outer planets) that isn't coming home till "a certain time". http://xkcd.com/1337/ Like so. ...
by stoppedcaring
Wed May 07, 2014 3:29 pm UTC
Forum: Science
Topic: 1338 changed my life! (veganism)
Replies: 153
Views: 22927

Re: 1338 changed my life! (veganism)

I get the thing about free range animals and whatnot, but I'm not sure why in-season produce is important. Out-of-season foods cannot be purchased locally; they have to be shipped in from far away. That's a problem, because things have to be picked earlier (lower overall nutrient profile) and tend ...
by stoppedcaring
Wed May 07, 2014 2:59 pm UTC
Forum: Science
Topic: 1338 changed my life! (veganism)
Replies: 153
Views: 22927

Re: 1338 changed my life! (veganism)

I just noticed one line from way earlier in this thread: ...they did not seem to have any financial interest... Bullocks. The super-fit octogenarians up on stage talking about their diet books didn't have any financial interest? Right. It's really hard to make a quantitative moral-ethical argument f...
by stoppedcaring
Wed May 07, 2014 2:08 pm UTC
Forum: Science
Topic: Are space objects ever pictured according to gravity fields?
Replies: 2
Views: 1538

Re: Are space objects ever pictured according to gravity fie

Let me just say that I love this idea.

Are you picturing the Hill Spheres of these stars, or some other radius based on mass?

I would say to use a different color instead of white, preferably one not typically associated with starlight. Dim purple, perhaps.
by stoppedcaring
Wed May 07, 2014 1:39 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

A couple more challenges (and some dangerously nifty solutions) I thought of last night.... I see two main problems arising with the current configuration. The first is an issue with propulsion. It's going to take a lot of force to accelerate a 21,000 tonne ship in any reasonable timeframe. We can g...
by stoppedcaring
Tue May 06, 2014 7:09 pm UTC
Forum: Science
Topic: Help Feynman's Dad
Replies: 32
Views: 6376

Re: Help Feynman's Dad

But I think that's not a point of confusion. Feynman's Dad isn't confused that energy is conserved. He's confused about where the photon actually comes from and I think the answer is that it comes from nothing. He can be solaced in the fact it's not entirely arbitrary, i.e. energy and other things ...
by stoppedcaring
Tue May 06, 2014 6:51 pm UTC
Forum: Science
Topic: Help Feynman's Dad
Replies: 32
Views: 6376

Re: Help Feynman's Dad

Any explanation how energy is "transformed" from electron potential energy into a photon is somewhat dishonest if you are trying to explain this to someone who wants to understand the mechanism because transformation implies some continuous process and this process is starkly discontinuou...
by stoppedcaring
Tue May 06, 2014 5:32 pm UTC
Forum: Science
Topic: Help Feynman's Dad
Replies: 32
Views: 6376

Re: Help Feynman's Dad

The problem is earlier in the question: He said, "I understand that when an atom makes a transition from one state to another, it emits a particle called a photon." "That's right," I said. Not to knock Feynman, but...not exactly. He should have seen this coming. When an atom make...
by stoppedcaring
Tue May 06, 2014 5:19 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

You seem to have done plenty of maths to back up each of your statements, and you seem to have been fairly dilligent in approaching the problem in terms of forseen difficulties (depending on how much the reader sees your solutions translating into practical realities.) So colour me impressed. I thi...
by stoppedcaring
Tue May 06, 2014 1:46 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

The momentum transfer enables the coilgun to act as the second stage; since it never leaves orbit, the weight cost associated with a second stage is zero even if the fuel is not. The rocket would need substantially more fuel to achieve the same velocity with an SSTO design, which is part of what I'...
by stoppedcaring
Mon May 05, 2014 6:12 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

don't forget the political dimension. whoever controls a doomsday weapon like this rules the world. One ring to rule them all... Hehe. Yes, this could double as a kinetic bombardment system. Then again, any country capable of putting a satellite in orbit can put up a kinetic bombardment system any ...
by stoppedcaring
Fri May 02, 2014 9:27 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

Do you get minor accidents at 4km/s? How close does the vessel would have to pass the gun? Well, there would be a whole range of entry speeds. Catastrophic failure would only be likely if you lined up your approach improperly...basically the same as a fighter jet dipping too low on entry for a carr...
by stoppedcaring
Fri May 02, 2014 8:46 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

Forget putting one up a decade later, the destruction of a multi-kilometre structure by a multi-km/s impact will push us straight into full blown Kessler syndrome at this stage. We'd be lucky to be going back to space at all within a decade :D My point being that using a flat or curved launch syste...
by stoppedcaring
Fri May 02, 2014 7:56 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

Incidentally, the nature of the momentum exchange is such that even using the same bipropellant liquid rocket fuel on the coilgun station, you'd still only be using a fraction of the fuel. Around 70 tonnes (as opposed to the ~300 tonnes the rocket would need to use for itself). You would still have...
by stoppedcaring
Thu May 01, 2014 6:52 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

Well the sprint missile (one of my favorites) had a burn-out velocity of around ~4km/s, but a ceiling altitude of only some 30km. A sprint missile modified to reach LEO could be built, but it would be huge - and therefore expensive. My problem with the acceleration is not whether or not we could bu...
by stoppedcaring
Thu May 01, 2014 4:48 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

Remember that the 80 km one is only if you want human-survivable launch. For a cargo-only launch system, it's just 4-8 km, with a launch cost of under $10 billion. I've stuck to the 80km figure not for human-survivable purposes but because of the weight penalty associated with building a rocket and...
by stoppedcaring
Thu May 01, 2014 2:18 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

I dunno... your quoted price of 62 billion for an 80km orbiting coilgun seems waaaay too low. The raw cost of launching the mass of the gun to space is only a fraction of the total cost. I'd say 62 billion is a reasonable amount to expect to pay to build an 80km coilgun on the ground . Oh, certainl...
by stoppedcaring
Thu May 01, 2014 1:33 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

By the time we have the ability to build and succesfully operate this, we won't need to. For example, the projected Skylon spaceplane, which could be operational within mere decades, is already projected to bring launch costs down to roughly £650 per kg (~$1000/kg). SpaceX is already promising laun...
by stoppedcaring
Thu May 01, 2014 1:31 pm UTC
Forum: Science
Topic: Singularities & their associated conceptual nastiness
Replies: 35
Views: 5725

Re: Singularities & their associated conceptual nastiness

Isn't the strong force what is overcome in radioactive nuclei? Ie: when you get enough protons together in a nuclei without enough neutrons to stabilise it they tend to break apart? Or is that an over-simplification? Nuclei actually break apart below the classical level, due to the effects of quant...
by stoppedcaring
Thu May 01, 2014 1:02 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Re: Orbital coilgun accelerator

Problems here with keeping the blasted thing in orbit - as soon as a rocket is "launched" through it, it will immediately start to fall out of orbit and will have to be re-boosted to its previous altitude - there is a question of whether ion engines will be able to provide enough thrust t...
by stoppedcaring
Thu May 01, 2014 12:36 pm UTC
Forum: Science
Topic: Singularities & their associated conceptual nastiness
Replies: 35
Views: 5725

Re: Singularities & their associated conceptual nastiness

Nothing can be accelerated past the speed of light, no exceptions. Not even in black holes. Oh, of course not. But the event horizon of a black hole is the same as the classical radius where escape velocity (and thus infalling velocity from infinity) reaches c. That's what I had in mind. b) No sign...
by stoppedcaring
Wed Apr 30, 2014 8:12 pm UTC
Forum: Science
Topic: Singularities & their associated conceptual nastiness
Replies: 35
Views: 5725

Re: Singularities & their associated conceptual nastiness

The electrostatic force is many orders of magnitude more powerful than the force of gravity.

Is a "black-static" hole possible -- a concentration of positive or negative charge so dense that an opposite-charge particle would be accelerated past the speed of light before impacting it?
by stoppedcaring
Wed Apr 30, 2014 5:07 pm UTC
Forum: Science
Topic: Orbital coilgun accelerator
Replies: 38
Views: 5872

Orbital coilgun accelerator

Okay, got an idea for an orbital launch system that might actually be feasible with current technology and materials (20th-century technology, TBH) and would almost definitely result in significantly lower launch costs despite the high initial construction cost. As What-If #58 references, it's quite...
by stoppedcaring
Tue Apr 29, 2014 4:54 pm UTC
Forum: Science
Topic: Energy requirements to launch to LEO (from vacuum zeppelin)
Replies: 46
Views: 36753

Re: Energy requirements to launch to LEO (from vacuum zeppel

How is the orbiting ned *de*celerating anything in that scenario? From its inertial reference frame, it's decelerating the payload. :) Deceleration is just an engineering convention, after all. "How would you catch an object thrown toward you at 5 miles per second?" is a lot easier to con...
by stoppedcaring
Tue Apr 29, 2014 2:23 pm UTC
Forum: Science
Topic: Energy requirements to launch to LEO (from vacuum zeppelin)
Replies: 46
Views: 36753

Re: Energy requirements to launch to LEO (from vacuum zeppel

Crazy spitballing here, I know, but what if you used an oversized sounding rocket to put payload up at orbital height and then used some sort of giant ultra-strong net strung between two orbiting satellites to catch it? It looks like you're talking about something like a skyhook . Skyhooks are quit...
by stoppedcaring
Tue Apr 29, 2014 1:55 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

If it helps any with the visualization, space is stretched in the vicinity of the EH as well as time. If you're hovering "just outside the EH", the actual location of the EH is always infinitely far below you in terms of proper distance. You can't just dip the tip of your fishing rod down...
by stoppedcaring
Mon Apr 28, 2014 8:40 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

gmalivuk wrote:Yeah, massive particles can't actually live there, as it's where orbital velocity reaches light speed. It's also not stable.

Hmm. A metastable circular orbit...sounds like the setup for the most powerful laser possible.
by stoppedcaring
Mon Apr 28, 2014 7:05 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

gmalivuk wrote:1.5 times the Schwarzschild radius.

Which, IIRC, is the distance to the photon sphere, where photons can sit in a perfectly circular orbit from anywhere between 1 revolution and a billion trillion revolutions.
by stoppedcaring
Mon Apr 28, 2014 4:55 pm UTC
Forum: Science
Topic: Energy requirements to launch to LEO (from vacuum zeppelin)
Replies: 46
Views: 36753

Re: Energy requirements to launch to LEO (from vacuum zeppel

Crazy spitballing here, I know, but what if you used an oversized sounding rocket to put payload up at orbital height and then used some sort of giant ultra-strong net strung between two orbiting satellites to catch it?
by stoppedcaring
Mon Apr 28, 2014 4:43 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

I suppose then that a circular orbit inside the event horizon is not possible, as the possible light cone points more and more toward the singularity the closer you get.
by stoppedcaring
Mon Apr 28, 2014 4:22 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

With small black holes this never comes up because tidal effects rip you into atoms long before you reach the event horizon...but for something like NGC 4889, tidal effects are practically nil. It sure would seem odd if your body was still physically connected but constrained by relativity such that...
by stoppedcaring
Mon Apr 28, 2014 4:16 pm UTC
Forum: Fictional Science
Topic: Crystal rings
Replies: 0
Views: 2654

Crystal rings

It's speculated that Uranus and Neptune could potentially have subsurface oceans of liquid diamond under high pressure...from what I understand, it's not too far-fetched. If such an ice giant were to collide with another planet or pass inside the Roche limit of its star, it would quite naturally be ...
by stoppedcaring
Mon Apr 28, 2014 4:08 pm UTC
Forum: Fictional Science
Topic: Find the Equator
Replies: 4
Views: 4991

Re: Find the Equator

There's no guarantee that the magnetic poles would align with the axial poles.
by stoppedcaring
Mon Apr 28, 2014 3:53 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

We talk about how a sufficiently large SMBH would have no noticeable effects as you crossed the event horizon. But if it's impossible for any signal to travel across the event horizon (or to travel "outward" from any point inside), wouldn't it instantly kill you? You wouldn't be able to fe...
by stoppedcaring
Fri Apr 25, 2014 9:57 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Re: Clarification on event horizons of black holes

if my math is right, it comes to a gravitational acceleration of 713 m/s2 or about 72g. Your math is not right, because you didn't take into account time dilation. If you're hovering at a particular height outside the event horizon, gravitational time dilation makes things seem to accelerate faster...
by stoppedcaring
Fri Apr 25, 2014 4:26 pm UTC
Forum: Science
Topic: Clarification on event horizons of black holes
Replies: 32
Views: 5220

Clarification on event horizons of black holes

This seems really obvious, but I wanted to make sure... There's nothing locally unique about the event horizon of a black hole, right? For a sufficiently large one (such that the acceleration and tidal forces at the Schwarzschild radius are minimal), a spacecraft could conceivably fly past the event...

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