Search found 509 matches

by eternauta3k
Sun Oct 29, 2017 2:48 pm UTC
Forum: Science
Topic: Is meditation just relaxation?
Replies: 15
Views: 3509

Re: Is meditation just relaxation?

At what point do you call "bullshit"? For example, do you believe claims of significant psychological change are plausible? I'm curious how people with a mainstream scientific view approach this question. I suspect that enlightenment doesn't get much hype because its wonderful benefits are...
by eternauta3k
Sun Oct 29, 2017 12:20 pm UTC
Forum: Science
Topic: Is meditation just relaxation?
Replies: 15
Views: 3509

Is meditation just relaxation?

Hi. I was looking at this subreddit where they're discussing meditation technique in detail, talking about using attention in a certain way, peripheral awareness in another, holding intentions, etc. https://www.reddit.com/r/TheMindIlluminated I was wondering if people here think this is all quackery.
by eternauta3k
Sat Oct 22, 2016 6:29 pm UTC
Forum: Science
Topic: Ideal balance of two bodies in orbit
Replies: 28
Views: 5786

Re: Ideal balance of two bodies in orbit

Conservation of orbital angular momentum would give you a lower bound for the distance between two rigid bodies. However, I'm not sure that orbital angular momentum is actually conserved here (maybe the bodies torque each other and turn orbital into spin).
by eternauta3k
Wed Apr 29, 2015 2:41 pm UTC
Forum: Serious Business
Topic: Encode a message so it can't be read until a certain time?
Replies: 84
Views: 55010

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

Regarding not rolling my own crypto: I was thinking of starting Dan Boneh's crypto class again (I dropped out the first time but greatly enjoyed it). However, it feels like a bad idea that'll only make me confident enough to be dangerous. Thoughts?
by eternauta3k
Thu Apr 02, 2015 4:51 pm UTC
Forum: Science
Topic: Teleporting inside a wall
Replies: 16
Views: 5298

Re: Teleporting inside a wall

While we're asking this sort of question... what happens if you teleport a region of *space* (not just the matter inside it)?
by eternauta3k
Tue Mar 24, 2015 6:41 pm UTC
Forum: Science
Topic: Maxwell's demon -- consensus on disproofs?
Replies: 20
Views: 5151

Re: Maxwell's demon -- consensus on disproofs?

What correlation is there between the pressure you detect now and the pressure after you open the gate?
by eternauta3k
Sat Dec 20, 2014 12:02 pm UTC
Forum: Science
Topic: Fermi's Golden Rule and laser rate equations
Replies: 5
Views: 3353

Re: Fermi's Golden Rule and laser rate equations

As far as I remember, you derive Fermi's golden rule for a single particle. You can then apply it to a system of particles under the independent particle approximation. What do you mean by "it breaks down"?
by eternauta3k
Sat Dec 20, 2014 11:39 am UTC
Forum: Science
Topic: Fingers on Humans
Replies: 80
Views: 18329

Re: Fingers on Humans

We should have 105 fingers total.

https://www.youtube.com/watch?v=PkyZGZRnQb4
by eternauta3k
Wed Dec 17, 2014 12:12 pm UTC
Forum: Science
Topic: Radio wave propagation in water
Replies: 5
Views: 2605

Re: Radio wave propagation in water

It's similar. But water absorbs visible light by excitation of the molecules (correct me if I'm wrong), while any absorption at RF is because of free carriers like ions doing what moiraemachy explained.
by eternauta3k
Thu Oct 02, 2014 1:17 pm UTC
Forum: Science
Topic: Favorite home experiments
Replies: 590
Views: 483251

Re: Favorite home experiments

What's the effect?
by eternauta3k
Sat Jul 05, 2014 11:51 am UTC
Forum: Science
Topic: How many neutrinos can fit inside the Earth?
Replies: 7
Views: 2880

Re: How many neutrinos can fit inside the Earth?

I'm guessing he means: how many neutrinos in a degenerate neutrino Fermi gas at 0K with the volume of the Earth?
by eternauta3k
Mon Jun 02, 2014 8:48 pm UTC
Forum: Science
Topic: Why do only some fields generate particles?
Replies: 19
Views: 3835

Re: Why do only some fields generate particles?

You don't need a field to interact with itself in order for it to produce particles when quantized. For example, the electric field (photons don't interact directly).
by eternauta3k
Sun Jun 01, 2014 1:00 pm UTC
Forum: Fictional Science
Topic: Solid Universe
Replies: 47
Views: 17040

Re: Solid Universe

You can think of a bubble in a uniformly dense infinite material as the superposition of the infinite material without holes, and a sphere of negative density. The force you feel is the sum of the force from the infinite material (0, from symmetry considerations) and the force from the sphere (repul...
by eternauta3k
Sat May 24, 2014 12:19 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2958
Views: 723000

Re: RELATIVITY QUESTIONS! (and other common queries)

That is an interesting question. Is there any configuration of masses that are not spherically symmetrical for which the set of points at which the gravitational effects are identical to a point mass or a spherical mass is of non-zero measure? Probably not. But I could imagine a literally infinite ...
by eternauta3k
Thu May 22, 2014 2:06 pm UTC
Forum: Science
Topic: Star Gazing Question
Replies: 7
Views: 1988

Re: Star Gazing Question

The problem is that any field of view sufficiently narrow to allow the stars to be bright will only show a very small portion of the sky. Because you want to project an image rather than simply viewing the image through a mirror, the rays will have to focus to a point and then diverge again. That w...
by eternauta3k
Sat May 10, 2014 4:46 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2958
Views: 723000

Re: RELATIVITY QUESTIONS! (and other common queries)

The man sees his feet contract and dilate as they accelerate with respect to him.
by eternauta3k
Sun Feb 09, 2014 4:01 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 26617

Re: Can you (passively) heat an object hotter than your sour

The argument against the optical heating mechanism seems to be that, when the object's surface temperature reaches the source's temperature, outgoing radiation balances incoming radiation and the temperature stops rising. My question is, what happens in very short timescales before you reach thermal...
by eternauta3k
Fri Jan 31, 2014 10:02 pm UTC
Forum: Science
Topic: Can you (passively) heat an object hotter than your source?
Replies: 98
Views: 26617

Re: Can you (passively) heat an object hotter than your sour

You can heat something to a higher temperature than the Sun. The system won't be in thermal equilibrium for a long while.
by eternauta3k
Thu Jan 16, 2014 12:38 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2958
Views: 723000

Re: RELATIVITY QUESTIONS! (and other common queries)

frequency at or exceeding the speed of light
Would there be a measurable effect?
Nah you're good.
by eternauta3k
Mon Jan 06, 2014 9:07 pm UTC
Forum: Science
Topic: Why do we perceive a 4-dimensional universe as 3?
Replies: 98
Views: 15870

Re: Why do we perceive a 4-dimensional universe as 3?

It's interesting how you can just throw that around but the person who disproves it has to plug some actual quantities to prove it's unlikely.
by eternauta3k
Mon Jan 06, 2014 5:02 pm UTC
Forum: Science
Topic: Why do we perceive a 4-dimensional universe as 3?
Replies: 98
Views: 15870

Re: Why do we perceive a 4-dimensional universe as 3?

From the annihilations.
by eternauta3k
Wed Jan 01, 2014 12:04 am UTC
Forum: Science
Topic: Size limits of a hollow planet.
Replies: 11
Views: 3355

Re: Size limits of a hollow planet.

We need to know how a sheet's crumple resistance scales depending on curvature and thickness.
by eternauta3k
Mon Dec 23, 2013 8:35 pm UTC
Forum: Serious Business
Topic: Racism in cultures other than your own
Replies: 97
Views: 25925

Re: Racism in cultures other than your own

Not sure if this is the right thread, but reading about Zwarte Piet reminded me of this: here in Argentina kids regularly wear blackface (painting their face with burnt cork) for school plays set in colonial times, to represent African slaves. Wondering about your opinion on this.
by eternauta3k
Wed Dec 11, 2013 10:56 am UTC
Forum: Science
Topic: Wave/Particle duality and Entanglement
Replies: 8
Views: 3436

Re: Wave/Particle duality and Entanglement

In the atom emitting a photon, you get the same correlations you get from classical statistics. It's ike telling someone to throw a ball in a random direction: as soon as you observe the ball you gain knowledge about the person's momentum. Nothing misterious there.
by eternauta3k
Fri Dec 06, 2013 10:08 pm UTC
Forum: General
Topic: Cast the hypothetical xkcd movie
Replies: 23
Views: 11405

Re: Cast the hypothetical xkcd movie

Normal guy is Randall Munroe.
by eternauta3k
Fri Dec 06, 2013 8:50 pm UTC
Forum: Science
Topic: Alternative Calendars
Replies: 46
Views: 11260

Re: Alternative Calendars

First day of the year should be an equinox, to have some degree of North-South symmetry.
by eternauta3k
Fri Dec 06, 2013 7:39 pm UTC
Forum: Science
Topic: Wave/Particle duality and Entanglement
Replies: 8
Views: 3436

Re: Wave/Particle duality and Entanglement

I think you don't get misterious behavior out of entanglement *unless* you use non-commuting observables. Without non-commuting observables it's the same as classical correlations which simply quantify your knowledge about the state and encode no new physics.
by eternauta3k
Fri Dec 06, 2013 6:32 pm UTC
Forum: Science
Topic: Matter/Antimatter Symmetry--a tricksy proposal
Replies: 38
Views: 8283

Re: Matter/Antimatter Symmetry--a tricksy proposal

doogly wrote:Yeah, there is nothing distinguishing colors. It's just a label.

And this fact leads to the existence of the strong force. Funky stuff.

Can you do the same with spin? Localize SU(2) symmetry -> get some force out?
by eternauta3k
Mon Dec 02, 2013 10:41 pm UTC
Forum: Science
Topic: Matter/Antimatter Symmetry--a tricksy proposal
Replies: 38
Views: 8283

Re: Matter/Antimatter Symmetry--a tricksy proposal

Mousepup wrote:the difference between green/antigreen and the other four charges is way over my head
SU(3) symmetry basically means that red, green are blue are identical. You may have to pick labels in order to study a system, but they are arbitrary (like your choice of coordinates).
Mousepup wrote:nuclear binding force is limited to a short radius, something physicists call 'confinement,'
Reading up on this I learned that we don't know why the nuclear force decays exponentially.
by eternauta3k
Fri Nov 29, 2013 10:37 pm UTC
Forum: Science
Topic: Can someone explain more about the Higgs Boson and mass?
Replies: 24
Views: 5765

Re: Can someone explain more about the Higgs Boson and mass?

Supose I write the Klein-Gordon equation for two particles with opposite electric charge. How do I get out that the mass of the composite system differs from the sum of the two particle masses? Is it necessary to quantize the EM field?
by eternauta3k
Sun Nov 17, 2013 9:16 pm UTC
Forum: Science
Topic: Matter/Antimatter Symmetry--a tricksy proposal
Replies: 38
Views: 8283

Re: Matter/Antimatter Symmetry--a tricksy proposal

It's more like a busy place with people running in all directions, with a small net flow in some direction.

Also the people barely bump into each other. And they are delocalized, I think (not sure if conduction implies localized electrons).
by eternauta3k
Wed Nov 13, 2013 4:30 pm UTC
Forum: Science
Topic: Can Someone Explain I(f) = (2hf^3/c2 )[1/(ehf/kT -1)]?
Replies: 2
Views: 2933

Re: Can Someone Explain I(f) = (2hf^3/c2 )[1/(ehf/kT -1)]?

Think of each electromagnetic mode of a cavity as a quantum harmonic oscillator -> its average energy is ħω/(exp(ħω/kT)-1) But you want the average energy of all the modes around ω -> you count how many modes are between ω and ω+dω and you get something that goes like ω², plus a bunch of constants I...
by eternauta3k
Wed Nov 13, 2013 2:16 pm UTC
Forum: Science
Topic: What is the smallest object that has gravity?
Replies: 65
Views: 19332

Re: What is the smallest object that has gravity?

lgw wrote:Heck, at this point I'd easily believe that all of the gravity of normal matter comes from binding energy, and we just don't know enough about quarks yet to see it yet.

That would mean one kind of energy gravitates and the other kind doesn't.
by eternauta3k
Wed Nov 13, 2013 2:14 pm UTC
Forum: Science
Topic: Matter/Antimatter Symmetry--a tricksy proposal
Replies: 38
Views: 8283

Re: Matter/Antimatter Symmetry--a tricksy proposal

skolnick1 wrote:we got the charge convention wrong on the electron

Meh, you can have charge carriers of either sign so there's no point privileging electrons.
by eternauta3k
Mon Nov 11, 2013 5:22 pm UTC
Forum: Serious Business
Topic: Encode a message so it can't be read until a certain time?
Replies: 84
Views: 55010

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

I bet there's some funky way to do this involving a betting pool. Make your secret the XOR of a million bit sequences. Choose a million people and let them bet on the time that the secret is revealed, but first place your bet on the time you want the message out. If each participant is perfectly gre...
by eternauta3k
Mon Nov 11, 2013 2:42 pm UTC
Forum: Science
Topic: What is the smallest object that has gravity?
Replies: 65
Views: 19332

Re: What is the smallest object that has gravity?

You'd need the oscillation period to be huge so you can ignore the vibrations from moving tonnes of stuff around.
by eternauta3k
Sun Nov 10, 2013 9:37 pm UTC
Forum: Science
Topic: What is the smallest object that has gravity?
Replies: 65
Views: 19332

Re: What is the smallest object that has gravity?

If your ships are point masses, sure.
by eternauta3k
Thu Nov 07, 2013 4:09 pm UTC
Forum: Science
Topic: What is the smallest object that has gravity?
Replies: 65
Views: 19332

Re: What is the smallest object that has gravity?

Let's not turn a thread about experimental challenges into a thread about theoretical vs experimental physics.
by eternauta3k
Tue Nov 05, 2013 9:47 pm UTC
Forum: Science
Topic: Molten Metal Bubble Blowing Contest, In Space!
Replies: 36
Views: 7970

Re: Molten Metal Bubble Blowing Contest, In Space!

the surface tension of molten metal is going to be pretty darn high
How high is it? And how high does it need to be?
by eternauta3k
Tue Nov 05, 2013 7:45 pm UTC
Forum: Science
Topic: Magnitude of celestial body bright enough to cast shadow
Replies: 12
Views: 5771

Re: Magnitude of celestial body bright enough to cast shadow

You need to know the level of noise in your image. If all sources of light add a predictable intensity, then you're limited by the brightness resolution of your detector like Carnildo said.

Go to advanced search