imatfaal

Got a test statistic of 141. P-value 0.003 even after MC simulation (2000 replicates). But maybe a different dataset as it had 3032 observations. I've attached my data as a text file for anyone to check themselves. Never heard of minimum difference survey, look forward to seeing it.

OK Prometheus - you may like to run this check as well on our methodology. I just downloaded 3032 randomly generated numbers between 1-100 from the internet random number generator. via this method I got a set of p values of only 9%, and 46%, and 1% and 98% and 74% etc.

It is not a sound method

Got a test statistic of 141. P-value 0.003 even after MC simulation (2000 replicates). But maybe a different dataset as it had 3032 observations. I've attached my data as a text file for anyone to check themselves. Never heard of minimum difference survey, look forward to seeing it.

if you have have done the putting in categories correctly (and I presume you have) then that result is correct.

I do chi squared by hand in excel - and get

141.6807 0.003186

And this means?

With a huge pinch of salt - that there is only a very very small chance that the numbers are randomly generated.

I do not think pearson chi-squared is the best test

Maybe it would be possible to design an installation on the moon that replicated 1g of gravity, but it would be a huge undertaking.

It's the minimum diameter of 200m that's the problem. Making machines that big on the Moon is probably a thousand years away.

 

One advantage of the cold on the Moon might be the ability to use superconductors as bearings, I only have a vague notion of how that stuff works without looking it up. But I know that they generally work much better in cold temperatures.

 

So maybe some sort of huge 250m plus rotating station could be made and run without much maintenance or energy input.

Did you not see the post about the negative issues regarding the regolith and associated charged dust particles? Also in the sun things heat up a lot - whilst there is no warming atmosphere so it may seem colder there is no atmosphere to allow heat dissipation in the ways this would happen on earth (ie warm up the air around you which gets replaced by colder air from further away). Engineering on the moon is fraught with difficulty

I am not aware what conclusions have been reached about the long term impact on physiology of low gravity, as on the moon, versus micro-gravity (erroneously called zero-g by some). Perhaps we shall get lucky and find lunar gravity, in combination with reasonable exercise, will be sufficient to maintain long term condition. Does anyone know of any research that has explored this issue?

Just to be clear - zero-g is probably just as good a name as micro-gravity; Gravity in the circumstances referred to is neither zero nor even much diminished - it is the reactive force from the ground which is missing. Those in orbit are in a state of free-fall - which is to say that gravity is the only force acting upon them. This is highly analogous to true zero-g or micro-gravity (ie hugely away from any mass) because their environment is in an exactly similar state of freefall so they appear weightless

The differences (D) are easily calculable of course - there are only 100 outcomes

D F(d)

0 10

1 18

2 16

3 14

4 12

5 10

6 8

7 6

8 4

9 2

But I don't have my data

Geeze. Why don't you calculate this lottery and win a few grand?

Seems like you'd be able to do it a lot more efficient then we did.

This was the penn state lottery but I don't gamble. All the large state and State lotteries are very well checked by some serious statisticians for loopholes and for bias

I got something like a chi-squared statistic of 155 on 99 DF, will check when i get home.

 

What dataset did you use? What distribution did you test against?

My data are on my pc at work - so I cannot recheck. There were 1602 data points.

I tested against an even distribution - ie sum^00_99 (bucket count - expected count if even distribution)^2 * (expected count if even distribution)^-1

Um, non genius here. What does that mean exactly?

Chi-squared test is a test which allows you to test a group of observations and see how well they fit a theoretical distribution. In this case the theoretical distribution is an even (ie all the same) distribution resulting from true randomness (although we know that would almost never be the case).

The figure we both quoted is basically the sum of the square of the differences between expected count and observed count (which is normalized by dividing by the expected count before summing)

The degrees of freedom is a statistical term which has lots of meanings - in chi-squared it means the number of categories minus 1.

The chi-squared figure and the degrees of freedom will give you (via a look up table or a function) a probability that the observed data and the theoretical data could both come from the same single data set

I got something like a chi-squared statistic of 155 on 99 DF, will check when i get home.

 

What dataset did you use? What distribution did you test against?

I also checked singly ie first number against buckets from 0-9 and second number against buckets from 0-9. The second number was down in the 40% range - which is not enough to void the null but still damn worrying for a lottery.

On monday I shall see if I can manage a minimum difference survey (followed by chi-squared) - that is the normal way to check the legitimacy of lottery draws. On a 6-49 lottery there is a 49% chance of a difference of one between two of the numbers, there are known chances for the other differences as well. You run a minimum difference for each set of 6 numbers and then pearson chi-squared the results of difference =1, =2, =3 etc. But I would first have to monte carlo / calculates analytically a set of probabilities for each of the differences for 2 draws from 10

I get a chi-squared of 77 which with 99 degrees of freedom is well within accepted chance of being drawn from the same distribution (ie random)

zztop has been banned as a suckpoppet of xyzt

I wish I could give you +10. The way it stands, I could only give you +1.

A few notes:

1. It is sufficient to do the analysis for half trip only. At the half trip, the travelling twin has clocked 3.46 and the stay at home twin has clocked 4. After that, symmetry takes over.

2. If one wants to take acceleration into account, for a more realistic analysis, I wrote these two sections for wiki long ago. The perspective of the travelling twin is most interesting.

I wrote these two sections for wiki long ago.

Surely you also need a particle at high speed (greater than phase speed of light in the material) for Cherenkov - it is basically a shckwave in the electromagnetic field within the material and if the driver particle is moving greater than the local speed of light you get a coherent result

the Euro original was called Jeux Sans Frontières it was rebranded as It's a Knockout for xenophobic and overly competitive Blighty

And cos you cannae have enough ...

Sorry but when I read your question all I could think of was "is that when you really really take the piss?"

I'll get my coat...

We have received a number of reports regarding "unfair" use of negative reputation and claims of persecution. Without zeroing in on any one member's moan, can we make a few points clear?

1. We, the moderating staff, can see who has given reputation points (both positive or negative), inter alia, this means :
   1. Complaining about small-minded people giving negative reputation points whilst doling out far more red downvotes yourself is both hypocritical and we know you are doing it. Unsurprisingly, we are not going to get involved.
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2. On the whole the reputation system is self-governing and self-balancing. For example I give far more green up-votes to balance (what I believe to be) unfair red down-votes than I give for pure quality of post. It doesn't take long to understand who likes/dislikes your work and why, even without the mod sneak-peek, so you tend to reinforce that which is approved of etc. and avoid that which is frowned upon. If you do not wish to modify your posting then so be it - but don't whinge when you get more red than green.
3. We have discussed this ad nauseam and will not be considering any changes to the reputation system unless we feel there is a new groundswell of support for change from our senior members.

Thank you for such great effort in this thread. However I can't get my head around it. Could you please help to learn me about Planck starting slow?

 

 

What is Planck time ?

 

What is a Planck length?

They are really just units - very basic units which require few assumptions and a healthy absence of anthropocentrism - but essential just units. SOME of them are about the energy scale when we realise that we have to include everything into our calculations. At the very largest scale of distance we can forget about everything except gravity, when distance is small and mass is smaller we can forget about gravity, etc. But at the planck energy scale we have to take into account quantum mechanics and gravity in one fell swoop and we cannot yet do this.

Martin's explanation is pretty damn good but requires careful reading and study - and I am pretty sure he won't answer any questions as I have a horrid feeling that he died (but maybe that was a different Martin with a great ability to explain physics)

...

No, my proof is exact, doesn't use any "simplification", there are no "curlies".

...

Sorry - I was looking at the posted equations rather than the links which I assumed were back up to the posts.

Elongation exists for ANY BH (it exists for any radial fall towards a gravitating body). The effect can be shown not only with the GR formalism but also with the Newtonian one. The amount of elongation is related to the Schwarzschild radius (which is related to the gravitating body mass but [math]r_s[/math] is a more elegant way of calculating). I already posted the exact proof. Once again, I want to thank all the small - minded people that keep downvoting my posts. It gives a good tally of all the people that fail to understand the subject. If you do not understand , just ask, I am more than happy to explain.

What makes you think I don't understand - I gave the figures for a SMBH and some rough ideas about other forces.

The schwarzchild radius is a long way from the most elegant way of calculating it - obviously for a Schild b-hole all you need is the mass (all you ever need). Surface (EH) tides are inversely proportional to the square of the mass - so it is patently clear that as the radius is proportional to the mass then the surface tides will become insignificant for large mass blackholes.

I am pretty sure that the exact proof you posted relies on a second order series simplification - but frankly I cannot be bothered to go back and look; it should definitely come with a curly almost equals and a health warning

And if we are talking about neg-reps - I only give them out for rudeness and arrogance. I haven't bothered dishing one out for a while - but bombastically making sweeping claims and then backtracking by narrowing the application of those claims is always good to gather red marks from the groundlings

This paper argues that at least one of the following propositions is true: (1) the human species is very likely to go extinct before reaching a “posthuman” stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a computer simulation. It follows that the belief that there is a significant chance that we will one day become posthumans who run ancestor-simulations is false, unless we are currently living in a simulation. A number of other consequences of this result are also discussed.

Are You Living In a Computer Simulation? Nick Bostrom. Philosophical Quarterly, 2003, Vol. 53, No. 211, pp. 243-255

The surface tides for a blackhole at the surface (EH) of a reasonable but undistinguished spiral galaxy (say 4million solar masses) would be a few tenths of a millimetre per second per metre *. So even two unconnected test masses would only move away from each very slowly and no spaghetification would occur outside the EH

* 6e-4 m/s^2 per metre

If I have my fermi estimations correct then at about 2e4 solar masses you would start to have problems (curl into the fetal position to avoid being stretched - although it might temporaraly fix a bad back) and at 10000 you would die. To be properly stretched at EH you would be down in the magnitude of 1000 solar masses and lower

 

 

Seems that I am the dense one after all. Always thought that certain mass within a certain small radius will have extremely high density without which a singularity would not form.

Black holes we know of are dense - the smaller ones very dense. But the maths and we believe the physics allow for blackholes of any size to form - and the bigger they are the smaller the density.

this is exactly what I was looking for thank you!

Check it is right before you use it!

If I have done my sums correctly

[latex]

m = \sqrt{\frac{3 \cdot c^6}{32 \cdot \pi \cdot G^3 \cdot \rho}}

[/latex]

Is the mass at which an spherical object becomes a blackhole for any given density rho

tdolowy - a pleasure. Keep investigating and "doing science"

I think the OP might be confused and the key point to make here is that black holes (singularities) are incredibly dense objects occupying ridiculously small area of space. I would also like to say that it is a pleasure to read and answer your question tdolowy...you dont have to worry about us having to bare with you. I remember being 14 and I was very much into black holes then

 

I'm afraid that they have to be Argent

Not true at all.

Any density can make a blackhole. The OP correctly gave the radius of a glass sphere (at 2400 kg/m3) which would become a blackhole. All you need is a certain mass within a certain radius - NOT a high density

Theoretically anything could become a black hole if you could squash it dense enough.

Exactly. But the op is making the slightly less usual point that any density object can be a black hole provided it is big enough. For constant density the mass increases with the radius cubed - so bearing in mind that in the equation for schwarzchild radius the mass and the radius are directly related as things get higher radius thn eventually the mass within the radius is high enough to exceed that required for blackhole. It is a little contrived as such a huge sphere would compress to a higher density