## Search found 167 matches

Tue Jun 11, 2019 7:44 pm UTC
Forum: Mathematics
Topic: "tricky" factoring problem
Replies: 18
Views: 835

### Re: "tricky" factoring problem

Yes. There appear to be quite a few. For example: {(10,3), (15,2)} , {(12, 5), (20, 3)}. I used Mathematica to brute force search. Here is my code: For[n = 5, n < 1000, n++, f = {n/#, #} & /@ Select[Divisors[n], # < Sqrt[n] &]; d = Flatten[{#[[1]] - #[[2]]} & /@ f]; s = Flatten[{#[[1]] +...
Mon Apr 29, 2019 10:34 am UTC
Forum: Science
Topic: Is it possible to escape from a black hole using another black hole?
Replies: 56
Views: 3541

### Re: Is it possible to escape from a black hole using another black hole?

If you pass through a surface and then escape to an arbitrary distance. The surface you passed was not an event horizon. So no.
Mon Mar 25, 2019 4:17 pm UTC
Forum: Science
Topic: Verifying physics at home
Replies: 15
Views: 2144

### Re: Verifying physics at home

I don't see how this is possible without quantum:

(Three Filter Experiment)
Fri Feb 08, 2019 7:43 pm UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 277
Views: 49941

### Re: Science fleeting thoughts

Neutrinos are useful for monitoring nuclear reactors from a distance:

https://www.aps.org/units/fps/newslette ... trinos.cfm
Thu Jan 10, 2019 5:03 pm UTC
Forum: Science
Topic: Stars in background of deep-sky photos are in foreground
Replies: 21
Views: 4478

### Re: Stars in background of deep-sky photos are in foreground

Also, you are probably not starting in a equatorial earth orbit anyway. The most energy efficient orbit to get into from a launch site is one with inclination equal to the latitude of the site. You can pick your LAN by the time of day you launch. Then picking the time of month, you can pick the loca...
Wed Nov 14, 2018 3:09 pm UTC
Forum: Science
Topic: Proprioceptive string microscopy
Replies: 10
Views: 3064

### Re: Proprioceptive string microscopy

Thu Apr 19, 2018 1:31 pm UTC
Forum: Science
Topic: Particles as sets?
Replies: 7
Views: 5095

### Re: Particles as sets?

Also the sets involved would be absurdly complicated. For instance, real numbers are usually defined as either equivalence classes of Cauchy sequences of rational number or of Dedekind (sp?) cuts or real numbers. If we go with the Dedekind cut definition, then every real number is actually a subset ...
Thu Apr 05, 2018 2:39 pm UTC
Forum: Science
Topic: Are Vitamin Supplements Toxic to Non-Human Animals?
Replies: 14
Views: 5680

### Re: Are Vitamin Supplements Toxic to Non-Human Animals?

Thu Mar 15, 2018 1:39 pm UTC
Forum: Fictional Science
Topic: Yet another FTL question...
Replies: 35
Views: 11445

### Re: Yet another FTL question...

Can I check something? Does the distortion of the light-cone grid arise naturally from what happens to space and time in special relativity? i.e. can those grids be derived from those two aspects of SR alone, or is another factor required? The light cones don't get distorted. In either grid,they ar...
Sat Dec 09, 2017 5:07 pm UTC
Forum: Science
Topic: A bag of french fries
Replies: 10
Views: 2544

### Re: A bag of french fries

I was thinking the sorting might happen as the fries are put in the container. They usually use that funnel/scoop contraption. Smaller fries might fall out sooner.
Fri Dec 08, 2017 5:40 pm UTC
Forum: Science
Topic: A bag of french fries
Replies: 10
Views: 2544

### Re: A bag of french fries

Tue Oct 31, 2017 2:13 pm UTC
Forum: Science
Topic: Is meditation just relaxation?
Replies: 15
Views: 3330

### Re: Is meditation just relaxation?

I don't want to threadjack, but my favorite example of the placebo effect is acupuncture. It turns out that it doesn't matter where you put the needles. If you shove needles into a person in a quiet place and let them rest with needles in them for half an hour it works the same if there are in acupu...
Sun Oct 29, 2017 9:59 pm UTC
Forum: Science
Topic: Is meditation just relaxation?
Replies: 15
Views: 3330

### Re: Is meditation just relaxation?

I am definitely of a scientific mindset, and I've been meditating most days for about a year (20 minutes a day). I've found it very helpful. I also do 1 hour of cardio every other day. Both of these are to deal with stress and anxiety. If I had to say, meditation is about 25% effective in the short ...
Wed Sep 20, 2017 4:55 pm UTC
Forum: Science
Topic: EXPERIENCE TRUE LEVEL!
Replies: 21
Views: 12010

### Re: EXPERIENCE TRUE LEVEL!

SLAC is probably the longest straightest. (2 miles) LIGO is longer (4 mile arms) but the pipes could curve I think without trouble, since the beam doesn't interact with the pipes. So at 8 inches per miles, SLAC's ends are 8 inches higher than the middle. I assume the floor or the SLAC facilility is ...
Mon Mar 27, 2017 12:55 am UTC
Forum: Science
Topic: Is terraforming Uranus and Neptune possible?
Replies: 22
Views: 6926

### Re: Is terraforming Uranus and Neptune possible?

I think that if you have the technology to do that kind of work, its probably easier to just live in space.
Mon Mar 06, 2017 5:00 pm UTC
Forum: Fictional Science
Topic: Material with High Specific Heat
Replies: 12
Views: 9333

### Re: Material with High Specific Heat

You could use it to time-average solar thermal power. Molten salt is used for this now, but can't last all night IIRC.
Mon Feb 13, 2017 4:47 pm UTC
Forum: Science
Topic: Walking on a neutronium Dyson Sphere
Replies: 15
Views: 5853

### Re: Walking on a neutronium Dyson Sphere

A little alpha'ing gave this: https://www.wolframalpha.com/input/?i=(standard+Gravity)%2F(Gravitational+Constant)%2F(4+Pi)%2F(1000+meters) If the shell is 1 km thick it has to be as dense as the densest white dwarfs. What is it that you think that equation shows? If you look at the surface gravity ...
Thu Feb 09, 2017 3:03 pm UTC
Forum: Science
Topic: Walking on a neutronium Dyson Sphere
Replies: 15
Views: 5853

### Re: Walking on a neutronium Dyson Sphere

A little alpha'ing gave this:

https://www.wolframalpha.com/input/?i=(standard+Gravity)%2F(Gravitational+Constant)%2F(4+Pi)%2F(1000+meters)

If the shell is 1 km thick it has to be as dense as the densest white dwarfs.
Thu Feb 02, 2017 3:38 pm UTC
Forum: Mathematics
Topic: Genetics in a species with three sex chromosomes
Replies: 18
Views: 4701

### Re: A World With Three Genders

You are talking about sex no gender.

Also, there are a variety of sex determination systems used by sexually reproducing life.

https://en.wikipedia.org/wiki/Sex-determination_system
Wed Feb 01, 2017 3:48 pm UTC
Forum: Science
Topic: Newton's shell theorem with negative mass
Replies: 12
Views: 3907

### Re: Newton's shell theorem with negative mass

I actually did my doctoral dissertation on negative mass, but mostly on cosmological scales. A matched pair of positive and negative mass particles would indeed accelerate forever. This doesn't violate conservation of energy, since the negative mass has negative kinetic energy. Generalizing, a gas w...
Wed Feb 01, 2017 12:18 pm UTC
Forum: Science
Topic: Newton's shell theorem with negative mass
Replies: 12
Views: 3907

### Re: Newton's shell theorem with negative mass

No, the -1kg object will fall down. The difference is that actually the 10kg object hits the earth faster than the 1kg object since the earth falls towards the 10kg object faster. Likewise, while the -1kg object is falling down, the earth is falling in the same direction, (so away from the -1kg obje...
Sat Dec 03, 2016 12:44 pm UTC
Forum: Mathematics
Topic: Patient Probability Problem
Replies: 7
Views: 2953

### Re: Patient Probability Problem

What you are describing is a Markov Chain.

https://en.wikipedia.org/wiki/Markov_chain
Tue Nov 29, 2016 5:04 pm UTC
Forum: Mathematics
Topic: Three externally tangent circles sharing a single point of tangency
Replies: 19
Views: 7102

### Re: Three externally tangent circles sharing a single point of tangency

jestingrabbit wrote:
Nicias wrote:In sphereical geometry, you will have trouble with "external"

Not really. You just need to give circles their centres, and then it should follow.

Sat Nov 12, 2016 7:26 pm UTC
Forum: Mathematics
Topic: Three externally tangent circles sharing a single point of tangency
Replies: 19
Views: 7102

### Re: Three externally tangent circles sharing a single point of tangency

In sphereical geometry, you will have trouble with "external"
Thu Oct 20, 2016 11:49 am UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 277
Views: 49941

### Re: Science fleeting thoughts

You might want to look into http://physics.ucsd.edu/do-the-math/

it's a blog by a physicist who got into an argument with an economist about why a perpetual growth model for the economy is impossible on "boiling the oceans" grounds.
Mon Oct 03, 2016 2:49 pm UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 277
Views: 49941

### Re: Science fleeting thoughts

Isn't this what tidal power does?
Sun Oct 02, 2016 5:14 pm UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 277
Views: 49941

### Re: Science fleeting thoughts

Maybe it'd be easier not to use rocks. Something with an even density would allow greater control of machine loading, electricity generation and so on. Something more fluid than large rocks would allow control of flow better, too, so sand may be a better choice. Then you still need a way to get san...
Mon Sep 05, 2016 11:18 am UTC
Forum: Science
Topic: In 1Billion Years, Earth will become a second Venus.
Replies: 7
Views: 3253

### Re: In 1Billion Years, Earth will become a second Venus.

will remain fairly stable for more than five billion more. So, assuming Wikipedia is correct, a billion years will not make Earth as hot as Venus. There will probably be a point after that 5 billion years when the sun will be bigger than the orbit of earth. That'll vaporize our atmosphere over time...
Wed Jun 08, 2016 2:39 pm UTC
Forum: Fictional Science
Topic: Splitting/Duplication in Humans
Replies: 25
Views: 10297

### Re: Asexual Reproduction in Humans

You might also want to check out the Orthognal Series . The main species in reproduces essentially asexually, an adult "female" splitting into two male and two females, with the males sterile. Sometimes they split into 2 females and 1 male, or one of each. Some of the plot is driven by a d...
Tue Jun 07, 2016 9:17 pm UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 434
Views: 152037

### Re: Math: Fleeting Thoughts

Another dumb question: I'm struggling to parse this sentence. "A polynomial with integer coefficients has a root in Z_p if and only if it has an integer root modulo p^k for any k >= 1". I get what it means to say two numbers are congruent mod n; it's a relationship between two numbers. I'...
Thu May 05, 2016 1:23 am UTC
Forum: Fictional Science
Topic: Could this planet exist?
Replies: 6
Views: 6749

### Re: Could this planet exist?

You also could have the planet tidally locked. Then rivers would flow to the hot side, where they would evaporate, and condense on the cold side. It could be tidally locked to the sun or just be a moon of a warm gas giant, and tidally locked to that, so that the hot/cold was not that extreme.
Sun Mar 06, 2016 3:33 pm UTC
Forum: Science
Topic: Protein isolate foam - how to eliminate?
Replies: 6
Views: 3849

### Re: Protein isolate foam - how to eliminate?

It depends on what the structure of the foam is. Some things to try:
• Oil of some sort, shouldn't matter what
• an emulsifier (egg yolk, mustard powder or things containing them, mayo, mustard)
• both
You should add these before you blend.
Wed Feb 24, 2016 3:47 pm UTC
Forum: Mathematics
Topic: Is math real?
Replies: 105
Views: 19105

### Re: Is math real?

I personally think that math is realer than all of those things you named.

All of the items you named are contingent on the physical laws of the universe.

To me, math is independent of that. I'm somewhat of a Platonist in terms of math.
Sat Feb 13, 2016 7:20 pm UTC
Forum: What If?
Topic: What-If 0145: "Fire From Moonlight"
Replies: 157
Views: 75061

### Re: What-If 0145: "Fire From Moonlight"

I think some of you are misunderstanding the argument. Lenses (and all other linear optics) can only change the apparent size of an object, not its surface brightness. So, the best you could do is make it appear to an object that the moon completely surrounds it. You could sustain that for about 12 ...
Wed Feb 10, 2016 12:26 pm UTC
Forum: What If?
Topic: What-If 0145: "Fire From Moonlight"
Replies: 157
Views: 75061

### Re: What-If 0145: "Fire From Moonlight"

Surely a carbon black stone dropped in the middle of the surface of the Moon would raise at a higher temperature - just like on Earth asphalt ends up hotter than limestone if both are left in the sunlight in summer. So I really think the argument is at least incomplete - it can be fixed if we take ...
Wed Feb 10, 2016 11:52 am UTC
Forum: What If?
Topic: What-If 0145: "Fire From Moonlight"
Replies: 157
Views: 75061

### Re: What-If 0145: "Fire From Moonlight"

The argument is that moon rocks don't get that hot, and they being hit by moonlight from many directions, plus the sun, for two weeks at a time.
Fri Dec 11, 2015 2:25 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2949
Views: 710228

### Re: RELATIVITY QUESTIONS! (and other common queries)

Depends on what you mean by "their reference frame" when an observer accelerates they could handle that in two ways: Naively, they could keep doing the same measurements they had been doing, this results in them having a non-intertial frame with them still at the spatial origin. Or they co...
Thu Dec 10, 2015 9:57 pm UTC
Forum: Science
Topic: A question about Dyson Spheres
Replies: 13
Views: 2715

### Re: A question about Dyson Spheres

Just wanted to point out that if this thing does collapse to a neutron star, it will be a very hot neutron star. All of the energy obtained by basically fusing the entire mass of the star is still bouncing around inside the sphere in the form of light and neutrinos If you ever cracked this thing ope...
Mon Dec 07, 2015 5:53 pm UTC
Forum: Fictional Science
Topic: Physics of a Flat World
Replies: 15
Views: 8463

### Re: Physics of a Flat World

They might not be periodic, but they are stable. A 1/r force has a logarithmic potential. You add the angular momentum term and you get an effective potential for your orbit of the form: A ln(r) + k /r^2. So V-> Infinity as r goes to either zero or infinity. So actually all orbits are bounded. You d...
Mon Dec 07, 2015 5:49 pm UTC
Forum: Science
Topic: Could we save the sun?
Replies: 18
Views: 3346

### Re: Could we save the sun?

That is a lot easier. It's also a relatively shortsighted solution, as once the sun has gone through it's red giant phase (with thousands of times it's current luminosity and a size of about the Earth's orbit).it will have a helium flash . That would be bad. Afterwards, if we invent some magic shie...