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by Tass
Thu Jan 28, 2016 5:06 pm UTC
Forum: Science
Topic: PhD study of this forum
Replies: 28
Views: 13812

Re: PhD study of this forum

I am obviously a bit late to the party, but I was a PhD-student in 2010-2012 when I was also much more active on this forum. Ask away, I'll gladly help in any way I can.
by Tass
Sun Jan 24, 2016 11:53 am UTC
Forum: Science
Topic: Landing rockets upright is unnecessary?
Replies: 61
Views: 9053

Re: Landing rockets upright is unnecessary?

The Falcon 9 would collapse like a crushed can on takeoff and landing if it didn't have internal pressurant resisting that. I have 5 questions that I the answer to really quickly. 1: How much does a Falcon 9 cost? 2: Can a Falcon 9 launch and/or land without people inside of it? 3: Does a device th...
by Tass
Fri Jan 22, 2016 10:06 pm UTC
Forum: Science
Topic: My own avian learning experiment
Replies: 12
Views: 3692

Re: My own avian learning experiment

Sorry it took so long, but I am posting now to tell that I expect my automatic trainer to be online in a few weeks! I have some laser cut parts assembled into a sort of drum shape with a hole in the side. A stepper motor can turn the drum once so that a small amount of food drops out of the hole ont...
by Tass
Sat Apr 04, 2015 10:39 pm UTC
Forum: Fictional Science
Topic: Black Hole Tidal Maths
Replies: 10
Views: 4752

Re: Black Hole Tidal Maths

Less than three g's, doesn't look scary at all. Jet pilots easily pull that, and if you are in a free fall trajectory around it you don't even feel it. In any case the tidal forces are going to be negligible until much further in than that.
by Tass
Fri Mar 27, 2015 5:45 am UTC
Forum: Fictional Science
Topic: Super-Powers (Super-Speed!)
Replies: 73
Views: 13579

Re: Super-Powers (Super-Speed!)

Also, because of the low-G she experiences while shifted, staying shifted for too long will leave her vulnerable to all the medical complications that come with exposure to low-G environments (there's a lot, everything from heart complications to bone complications). She'd have to use it a lot to g...
by Tass
Thu Mar 26, 2015 1:53 pm UTC
Forum: Fictional Science
Topic: Super-Powers (Super-Speed!)
Replies: 73
Views: 13579

Re: Super-Powers (Super-Speed!)

Neil_Boekend wrote:If step 2 causes her (from her perspective) to slow down to 1 km/h why does step 4 not include speeding up to 100 km/h from her perspective?


It would. And no matter her amount of practice she would fall, and possibly die. She'd do well to slow down before speeding time back up.
by Tass
Wed Mar 25, 2015 6:32 pm UTC
Forum: Fictional Science
Topic: Super-Powers (Super-Speed!)
Replies: 73
Views: 13579

Re: Super-Powers (Super-Speed!)

The Great Hippo wrote: (do bullets traveling at 1700 mph leave a small vacuum behind them? If so, she might see their 'air trails', ala the Matrix).


In water definitely. In air, no, nothing visible.

There are plenty of photos of bullets in flight
by Tass
Wed Mar 25, 2015 4:05 pm UTC
Forum: Fictional Science
Topic: Super-Powers (Super-Speed!)
Replies: 73
Views: 13579

Re: Super-Powers (Super-Speed!)

Though, actually, reading about it now -- bullets go at about 1700 mph. At 10x, it'd be going at 170 mph; still too fast for him to dodge or manipulate in any meaningful way. Are you also saying that in this state, the bullet would be relatively harmless to him? Way too fast to catch, yes. It would...
by Tass
Wed Mar 25, 2015 3:49 pm UTC
Forum: Science
Topic: Zero and low-gravity activities
Replies: 22
Views: 8777

Re: Zero and low-gravity activities

I would think in 1/100g terminal velocity is quite survivable?
by Tass
Mon Mar 23, 2015 1:05 pm UTC
Forum: Fictional Science
Topic: Fission Stars
Replies: 26
Views: 7003

Re: Fission Stars

In effect we have a decreasing fission rate with a decreasing density. Combined with the radiation pressure I foresee a self stabilizing system. Density is too high -> less neutrons decay before they encounter a fissile core-> fission rate increases -> radiation pressure increases -> star expands -...
by Tass
Mon Mar 23, 2015 1:02 pm UTC
Forum: Fictional Science
Topic: Super-Powers (Super-Speed!)
Replies: 73
Views: 13579

Re: Super-Powers (Super-Speed!)

...that's an excellent question, and something I hadn't thought about. I imagine to him, when he dilates time, gravity acts at a fraction of its expected power; IE, x100 means he falls x100 slower, so gravity 'feels' like it's working at .001 what's expected. Almost, but not quite. It is right grav...
by Tass
Mon Mar 23, 2015 12:27 pm UTC
Forum: Fictional Science
Topic: Fission Stars
Replies: 26
Views: 7003

Re: Fission Stars

A fusion event doesn't cause other fusion events. A fission event can cause further fission events. Thought: There may be stabilising mechanisms; as the fission rate increases the "star" expands due to the increase thermal pressure - would that reduce the reaction rate (the star becomes l...
by Tass
Sun Mar 22, 2015 10:08 pm UTC
Forum: Fictional Science
Topic: Fission Stars
Replies: 26
Views: 7003

Re: Fission Stars

I think a big problem might be to make the chain reaction self-regulating. In certain reactor types (such as FLIBE) this an be achieved because thermal expansion of the fissioning material gives larger surface area that loses more neutrons. In ordinary fusion stars it works because the reaction rate...
by Tass
Sun Mar 22, 2015 8:23 am UTC
Forum: Science
Topic: Sea level rising Question
Replies: 11
Views: 2010

Re: Sea level rising Question

A cause of variation that no one has mentioned yet is changes in gravity as a result of the shifting mass. When an ice cap melts, the mass of the ice no longer attracts water to the vicinity. So the rest of the water in the oceans redistribute to fit the new shape of the Earths gravity. Thus sea lev...
by Tass
Wed Jan 21, 2015 7:13 pm UTC
Forum: Science
Topic: What would it be like to put a giant drop of water in a...
Replies: 15
Views: 4665

Re: What would it be like to put a giant drop of water in a.

That actually sounds quite dangerous. Here's a link to a recent occurrence where an astronaut's helmet started filling up with water. http://www.space.com/24835-spacesuit-water-leak-nasa-investigation.html While the total volume of water in the helmet was nowhere near the volume of air, the water f...
by Tass
Mon Dec 08, 2014 8:48 am UTC
Forum: Science
Topic: Charge Distribution in Fluid
Replies: 7
Views: 2385

Re: Charge Distribution in Fluid

Assuming a "perfect" insulating mechanism that prevents charge from moving between solution and plates, and that the ions are otherwise free to move throughout the solution (ie, conduct), then i think the end result would be equivalent to a pair of 1m x 1m parallel plate capacitors in ser...
by Tass
Tue Nov 04, 2014 5:45 pm UTC
Forum: Fictional Science
Topic: A Real Suit for Superhuman Speeds
Replies: 16
Views: 8216

Re: A Real Suit for Superhuman Speeds

stoppedcaring wrote:It shouldn't be too terribly hard to estimate, at least order-of-magnitude. The heat capacity of water is well-known.


So it is. But the heat transfer rate through the shock front will be much harder to calculate.
by Tass
Mon Nov 03, 2014 1:17 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1442: "Chemistry"
Replies: 63
Views: 15585

Re: 1442: "Chemistry"

How to make gold:

Al + Cu -> Au + Cl
At + Pu -> Au + Pt
by Tass
Sun Nov 02, 2014 8:29 pm UTC
Forum: Fictional Science
Topic: A Real Suit for Superhuman Speeds
Replies: 16
Views: 8216

Re: A Real Suit for Superhuman Speeds

Holding your skin at boiling point sounds a fair bit better than just burning to death immediately, but still painful and likely fatal after more than a few seconds. Would it be possible to engineer a suit like that to keep the boiling water just a bit further away from the skin? High temperature r...
by Tass
Wed Oct 22, 2014 1:51 pm UTC
Forum: Fictional Science
Topic: A Real Suit for Superhuman Speeds
Replies: 16
Views: 8216

Re: A Real Suit for Superhuman Speeds

CNT's are also made of carbon, and thus quickly attacked by the hot oxygen they would be moving through (i.e. they burn). For the best materials we've found, look to reentering spacecraft, obviously the problem is pretty much the same. Sadly the good ones tend to be inflexible and heavy, you don't w...
by Tass
Mon Aug 18, 2014 12:32 pm UTC
Forum: Fictional Science
Topic: Silly Question: Neutrino Rocket
Replies: 23
Views: 9874

Re: Silly Question: Neutrino Rocket

Yeah, if you've got the mirror setup, it means you're already making sure the path between that and the ship is clear of obstacles, so just go the photon route. Hell, generate them on the ground instead and you don't even have to worry about the waste heat on your ship. The neutrino suggestion was ...
by Tass
Wed Aug 06, 2014 11:34 am UTC
Forum: Science
Topic: Radioactive decay can be influenced?
Replies: 9
Views: 2396

Re: Radioactive decay can be influenced?

I would assume that, because it is a beta-decay (producing an electron) that the electron density in the nucleus has a slight effect.

It changes the relative energies of the reactant and product.
by Tass
Mon Aug 04, 2014 10:22 pm UTC
Forum: Science
Topic: Why is hydrogen's boiling point higher than helium's?
Replies: 4
Views: 4711

Re: Why is hydrogen's boiling point higher than helium's?

Yeah, the Helium may have twice the mass, but that is more or less irrelevant. They have the same number of electrons, and the hydrogens' are more spread out and more polarizable.
by Tass
Sat Aug 02, 2014 1:32 pm UTC
Forum: Fictional Science
Topic: Solid Universe
Replies: 47
Views: 13916

Re: Solid Universe

But…wait a second. The shell theorem makes clear that a uniform spherical shell exerts no gravitational force on objects within, regardless of location within. In our one-bubble universe, we may view the solid (or liquid) universe as concentric shells around the bubble. Then matter inside the bubbl...
by Tass
Sat Jul 19, 2014 12:35 pm UTC
Forum: Fictional Science
Topic: Silly Question: Neutrino Rocket
Replies: 23
Views: 9874

Re: Silly Question: Neutrino Rocket

How is that at all relevant for the discussion?

Anyway, the same is true for a regular rocket, if you bounce the exhaust back an forth between the rocket and a planet. It is then not really a rocket anymore, but some sort of exotic propulsion scheme.
by Tass
Mon Jul 14, 2014 10:28 am UTC
Forum: Science
Topic: Absorption of visible light in atmosphere
Replies: 14
Views: 5205

Re: Absorption of visible light in atmosphere

Are we talking dry air or regular atmospheric air? After all water is blue, because of actual absorption. It absorbs red light more than blue (a tail from an actual absorption peak in the infrared.) Come to think of it I don't know if that is true for gaseous molecules or only for liquid water. Lack...
by Tass
Sat Jul 12, 2014 3:11 pm UTC
Forum: Fictional Science
Topic: Solid Universe
Replies: 47
Views: 13916

Re: Solid Universe

Note: I am of course assuming that the matter is incompressible and nonvolatile, so that there will be a finite and conserved amount of void. But in that case their reasoning consists of a rigorous mathematical demonstration that the hole behaves a certain way, not just verbal analogies. It is not j...
by Tass
Sat Jul 12, 2014 10:08 am UTC
Forum: Fictional Science
Topic: Solid Universe
Replies: 47
Views: 13916

Re: Solid Universe

It works perfectly. A continuum of the dense matter (water, whatever this universe is made of) is in equilibrium. Now remove some: In the water this makes a bubble, this bubble is less dense and thus feels less gravity. Everything else is the same as before, thus it has to rise. In this fictional un...
by Tass
Fri Jul 11, 2014 12:44 pm UTC
Forum: Fictional Science
Topic: Silly Question: Neutrino Rocket
Replies: 23
Views: 9874

Re: Silly Question: Neutrino Rocket

Well I wasn't necessarily supposing that the photons were quite energetic enough to knock neutrinos out at that speed. Oh, right. I was just assuming MeV neutrinos since they are the only ones we have good data on. Of course if the energy is lower then the exhaust velocity drops too, although it ha...
by Tass
Fri Jul 11, 2014 11:31 am UTC
Forum: Fictional Science
Topic: Silly Question: Neutrino Rocket
Replies: 23
Views: 9874

Re: Silly Question: Neutrino Rocket

Tass, I'm thinking you were using some code that was supposed to render math. What should I use to read it? They're just urls that the forum software didn't parse correctly. Paste it into your address bar. Whoops, yeah, that doesn't look too nice. Any idea how to fix it? Maybe I should just remove ...
by Tass
Wed Jul 09, 2014 10:32 am UTC
Forum: Science
Topic: How many neutrinos can fit inside the Earth?
Replies: 7
Views: 2200

Re: How many neutrinos can fit inside the Earth?

Well, neutrinos can not actually pass through an elemental particle. That is what the Pauli exclusion principle tells us. That is not what it says at all. Elementary particles are not little balls. Between molecules there is a relatively big vacuum. Between the atoms in a molecule is some space. Th...
by Tass
Tue Jul 08, 2014 2:02 pm UTC
Forum: Fictional Science
Topic: Solid Universe
Replies: 47
Views: 13916

Re: Solid Universe

Hypnosifl wrote:
snowyowl wrote:I like this universe with a cosmological constant. Voids produce anti-gravity that repels solid matter, but they attract other voids.

What's the argument for why they would attract other voids?


Because they repel matter.
by Tass
Tue Jul 08, 2014 12:59 pm UTC
Forum: Fictional Science
Topic: Silly Question: Neutrino Rocket
Replies: 23
Views: 9874

Re: Silly Question: Neutrino Rocket

Most posts in the thread discuss the infeasibility of a neutrino rocket, rather than addressing the question of radiation, so let us assume a perfect magical matter-to-neutrino-thrust rocket, and see whether it would be harmful. Randalls references for the lethal neutrinos what if is a good place to...
by Tass
Sun Jul 06, 2014 5:25 pm UTC
Forum: Science
Topic: How many neutrinos can fit inside the Earth?
Replies: 7
Views: 2200

Re: How many neutrinos can fit inside the Earth?

eternauta3k wrote:I'm guessing he means: how many neutrinos in a denegerate neutrino Fermi gas at 0K with the volume of the Earth?


And confined by earths gravity.
by Tass
Sun Jul 06, 2014 5:23 pm UTC
Forum: Science
Topic: I can't find where I'm going wrong. (perpetual motion flaw)
Replies: 19
Views: 3205

Re: I can't find where I'm going wrong. (perpetual motion fl

You cannot stack enough object to overcome the air pressure difference at the seal. Or rather, you can, but the stack will be too high, you won't have enough energy from the buoyancy to get it high enough. Each object has a potential energy equal to its mass times g times the height plus its volume ...
by Tass
Thu Jun 05, 2014 8:07 pm UTC
Forum: Fictional Science
Topic: Hard sci fi and the tyranny of the rocket equation
Replies: 53
Views: 10649

Re: Hard sci fi and the tyranny of the rocket equation

A nice thing to have in science fiction is antigravity or hovering capacity. But the rocket equation makes this difficult if you're using anything like conventional propellant. Truly hard scifi probably restricts you to the rocket equation, but what's the "hardest" semi-firm scifi solutio...
by Tass
Tue May 27, 2014 8:31 pm UTC
Forum: Science
Topic: Possibly illegal but ostensibly feasible money-making scheme
Replies: 17
Views: 3432

Re: Possibly illegal but ostensibly feasible money-making sc

it's not the efficiency, but the hardware/maintenance costs that'll break your scheme. Surely maintenance for a small vacuum maglev flywheel isn't that bad. Maybe not, but he also said hardware cost. If you spend a thousand dollars to earn a cent per day then you are not earning anything. Money cos...
by Tass
Tue May 27, 2014 8:26 pm UTC
Forum: Fictional Science
Topic: Solid Universe
Replies: 47
Views: 13916

Re: Solid Universe

Okay. I'm a physicist. (We'll a biophysicist who has never taken General Relativity, but I like to kid myself that I have some rudimentary understanding of it anyway.) In lieu of some actual cosmologist, I'll try to give my best answer. First off: Lack of a center does not mean that collapse can not...
by Tass
Tue May 27, 2014 6:56 pm UTC
Forum: Science
Topic: Possibly illegal but ostensibly feasible money-making scheme
Replies: 17
Views: 3432

Re: Possibly illegal but ostensibly feasible money-making sc

My city's municipal authority is starting to roll out an opt-in peak-power system. Consumers who opt in to the new program are charged only 6 cents per kilowatt-hour during off-peak hours but are charged 38 cents per kilowatt-hour during peak hours (where peak is 3pm to 7pm during the weekdays). If...
by Tass
Sun May 25, 2014 4:51 pm UTC
Forum: Science
Topic: If you want a warm room, does energy efficiency matter?
Replies: 28
Views: 8273

Re: If you want a warm room, does energy efficiency matter?

billy joule wrote:I don't think you understand what a heat exchanger does...


He meant a heat pump.


billy joule wrote:EDIT:God dammit, this thread is from 2012 :oops:


Indeed.

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