imatfaal

You have slipped up - earth is more dense than glass and water (1 gram / cm^3) thus it will need a smaller radius to make a black hole with the DENSITY (not mass as you have put) of earth.

I make it 14.1LM, 22.3LM , and 9.4LM respectively for Glass, Water, Earth.

More interestingly - a black hole with the MASS of the earth would be about a 3rd of an inch across (9mm)

This is the mass of a sphere (the curly p is a rho which stands for density, and r is the radius)

[latex]Mass_{sphere} = \rho \cdot \frac{4}{3} \pi r^3[/latex]

This is the radius of a blackhole (G and c are constants and M is the mass)

[latex]r_s=\frac{2GM}{c^2}[/latex]

You can work out all the figures from just these two equations - note that they both have radius and mass in them

Albert Frankeneinstein has been banned as a suckpoppet of zbigniew.modrzejewski

 

Well done Imatfaal +1 for you !

 

What is 22678 composed of ?

 

I reached the solution 2518 in the following way.

 

2520 being the LCM of [3,4,5,6,7,8 & 9] 2520 will be divided by 3,4,5,6 etc without remainder.

 

2520-2 = 2518 will be divided by each number with the remainder of 3-2, 4-2, 5-2, 6-2 etc leaving the remainder 1, 2, 3, 4, etc.

Oh my word that is a much neater solution than mine. Well done.

I used Chinese remainder theorem which can be phrased thus

for a set of congruences which are simultaneous as follows:

[latex]x\equiv a_i(mod\ m_i)[/latex]

for

[latex] i=1,2,...k[/latex]

if one sets

[latex]M=m_1.m_2...m_r[/latex]

and

[latex]b_i \frac{M}{m_i}=1(mod\ m_i)[/latex]

then

[latex] x \equiv \left [ a_1.b_1 \frac{M}{m_1}+...+a_k.b_k\frac{M}{m_k}\right ](mod\ M)[/latex]

This only works if all pairs of modulos are pairwise coprime - but if that is the case it always works. As you can see yours is so much nicer and simpler. I did mine with the help of a spreadsheet for the arithmetic

If you can measure them, why refer to them as virtual?

 

You say a void empty of everything does not exist, what then do you propose is left if we could remove all the matter from a volume of space?

 

Take note I said all the matter.

Particle/Antiparticle Pairs come into existence and vanish very quickly - they are a fluctuation that shouldn't happen according to classical physicals but must happen according to quantum field theory.

Classically we can remove everything from space (the classical vacuum) - but this is a approximate situation as you will always have blackbody photons, and quantum field fluctuations. Even in a toy universe with no matter and no radiation you will still have pairs popping into existence - a zero point energy

I have still not heard anything mentioned that suggests space is made of anything?

 

Fields occupy space ?

I do not understand that but recognise 0.

Of course it can never be empty space if people keep putting things back into it.

epsilon with a little zero in subscript and mu with a little subscript are the symbols for the permittivity and permeability of free space (the classical vacuum). The zero in the subscript shows they are for free space and not for another substance - neither has the value zero

epsilon_zero = 8.854810^-12 Farads per metre

mu_zero = 4*pi *10^-7 Newtons per Amp^2

Virtual means they do not exist physically, also you can not change definition to suit or it leads to global confusion. The definition of a void is space completely empty of everything, putting things in makes it no longer a void.

 

This is a science forum! may I suggest you get your definitions correct

You do realise we can measure them? And the philosophical void empty of everything does not exist.

Maybe I need to go back and find that and re-read it. On first reading I thought it seemed like stuff was leaving the two ends - just more through one end than the other. But it's been a while. And it definitely involved physics I'm only partially knowledgeable about. I'm really just an engineer. A PhD educated one, and I did try to load up on math and physics in graduate school, but I'm still not "professional grade" in those areas. Still in the "little learning" category of your signature quote (which I love, by the way).

I think the problem with every explanation that I have seen from the experimenters is that it leaves far too much open and unsaid - which is probably why we come to such varying conclusions. And from your credentials I can assure you are far in advance of me

"You have to believe we are magic

Nothin' can stand in our way

You have to believe we are magic

Don't let your aim ever stray"

A bit of the divine Olivia Neutron-Bomb - perfectly fitting for a physics thread

I really would not call this very simple - unless you know Chinese Remainder or are very adept with modular arithmetic then it would strike me as very hard.

A few hints in the next spoiler

Hey imatfaal, I understand what you wrote this time

 

Simple explanations satisfy me the most:

The act of observing an unknown state of particles involves acting upon them with some kind of radiation - photons for ex which influences the very act of observing these particles. The act of observing an unknown state of playing cards involves acting upon it with photons too but no matter how hard we try to bombard the cards with photons we will not influence the act of observing them. No matter how hard we try we won't get a deck of cards to behave in a quantum mechanical way.

 

Agree.

Just to whisper - we have got to the point of entangling macro size objects, I think mirrors; one day in the future there may be a possibility t do extraordinary things with superposition. This is the Schroedinger's cat thang - a way of merging the quantum and the macro to make a seeming paradox. But that is off topic and liable to confuse which I why I said it in a whisper

I'll concede that my statement was prematurly stated and not exactly how I should have expressed it. Also, what I had intended to say isn't really that important.

 

However, I think I understand where your going with this analogy which, If I'm right could serve a very useful purpose where I think we could have some common understanding of one of the more confusing aspects of entanglement, that I would have had trouble explaining myself, while recognizing it in your example of showing the relavance of the hidden information of entanglement.

1. It is not hidden - even if you use this word inadvisedly to mean unusual or unknown it is "taken" in this context by its usage in local hidden variables which have been proven not to account for qm effects. The information is not pre-existing yet hidden from the observer - the state of particle A and the state of particle B are not defined as yet; the only state which can be defined is the superposition. This is crucial - you cannot cannot cannot get the same results for local hidden variables; it was the genius of bell to find a relatively simple experimental method to test this

Correct me if I'm wrong but It seems like it was intended to show that the mathematical treatment of results when two observers measuring the same entangled spin angle is actually mathematically equivalent to two measurements of a single spin property as represented by the Queen

 

And that's mathematically different when measuring different spin angles that sometimes represent two different spin states represented by the Queen or Ace.

Not just mathematically but experimentally - the analogy was (as I think you understand) that if you measure spin on the same axis on both entangled particles (ie with a queen each time) then you always get opposite results as the spins are perfectly anticorrelated. However if you measure on two entangled particles on different axes (queen and ace) then you do not get the expected results demanded by a classical analysis. I started the analogy with the idea of the idea of using whether you can pair up your first card - ie a correlation; which is closer to the truth but it was already too complex. And in your last sentence - just to bring the point home; you do not measure two different spin states - you measure a pair of particles in superposition.

It wouldn't matter that neither observer knew when their measurements coincided, only that they know that they would a third of the time.

You do not need two observers for "weirdness" to occur. Don't start getting into quantum teleportation before you get your head around this - or concentrate entirely on quantum teleportation and ignore this. The Bell experiment is the repeated measurement of pairs of entangled particles (whether spin on electrons or polarisation of photons) at different axes and the amount of correlation or anti-correlation between the two particles of the pair. There is no need for a second observer who has only the information passed by the entangled pair etc. Keep it simple.

However, I think that's all the more reason for looking at it through an appropriate analogy. Once you realise that most of it is just probability, then QM becomes much easier to understand.

This, in my opinion, is the nub of the problem. There is no appropriate classical analogy - there cannot be as the results of the qm world are fundamentally odd. You can indeed work with QM by just sucking it up and doing the maths ("Shut up and Calculate" - as not said by Feynman) - but you are missing out on all the fun and just working as black box, more importantly you cannot extend your ideas if you do not embrace the divergence from the classical

 

 

I don't know. There are zero energy solutions to the Einstein Field Equations (the Milne model, for example) that consist of an empty space-time. These are useful to understand how space-time behaves in various different situations. They are "unphysical" in the sense of not representing the universe we live in, but they are valid physical thought experiments.

Exactly what I was getting at this section "We will often assume that space is empty as we don't care about a tiny number of virtual pairs (ie when dealing with planetary orbits)" but when you are dealing with EFE you are - perforce - dealing with the large scale and you can safely not care about the tiny interactions. This is where GR falls down - it works brilliantly on the large scale but there is no crossover to the microscale, there is no harmonious link up with qm/qft ; discussions of the void as completely empty space are necessarily dealing with the small scale and thus must engage with the quantum world. And as we are talking about fields as well then there is always the Higgs field to think about

Shadows don't destroy light, so any photons propagating from a light source would still be en route to the surface of the moon regardless of any shadows.

 

The light would still be hitting the moon for a few fractions of a moment before the shadow "reaches" it, so the speed of any shadow would still be limited to c surely?

nope. Perhaps it is easier to visualize with the lighthouse analogy - you set up a lighthouse with a very strong bright laser. At a given speed of rotation and radius of observation the lightbeam will be tracking a circle at a tangential speed greater than c. But any given photon / the EMR is moving radially outwards at c

A common misconception, if the space is defined to be empty, then why are you ''filling'' the space with matter? We have definition to avoid confusion, a void is empty of all matter.

This is a physics forum - nature trumps definition. You can define space as to be empty and you have created a non-physical environment whereas in reality even the deepest void has virtual particles/zero-point energy field. We will often assume that space is empty as we don't care about a tiny number of virtual pairs (ie when dealing with planetary orbits) - but if you are dealing with the small scale and talking about the vacuum then you must not ignore the reality of the situation.

Things to bear in mind in a nice investigation:

1. M1 and M2 will feel an equal and opposite force. If they are not fixed what will happen?

2. If M1 and M2 are fixed in space - this is very unphysical . Is there a more realistic example which you could look at?

3. What happens if M1=M2 and the test object cannot split?

4. What shapes can orbits take? How do you engineer (by changing relative masses/velocities) each of them? Is this a simple question - ie can you assume what will happen or do you need to calculate, and is it possible to calculate?

You might also wish to look at cathode ray tubes, or mass spectrometry. This is a very similar question - and it is something we do all the time

And remember that the shadow might track over the far distant surface at a very great speed - but changes to the shadows movement will only propagate outwards from the light at lightspeed. Information transit is still limited to c

The explanation I read made specific mention of more photons leaving through one end than through the other end. Even though both ends were closed - I wondered if it was perhaps some kind of tunneling. But I don't really know enough about tunneling to do any kind of real evaluation.

 

Are there more than one of these concepts around? Because another thing I read made reference to somehow changing the mass of a vibrating plate (the weird crazy part was how they managed to do that). I remember that article striking me as totally absurd.

From my reading your first paragraph is very nearly what they claim - however they claim this all happens inside the vessel. The particles are created at one end - the "field"/"environment" causes these particles to change in momentum in their passage from one end to another thus transferring the momentum to the vessel. It all sounds like the claim that firing a gun within a shipping container in space will cause the container to move as the bullets strike the end wall - this neglects that the recoil is equal and opposite and will provide exactly the same force in the opposite direction; as we know the CoM will stay put. They get around this by claiming that the change in momentum is leveraged on some sort of zero-point energy field - this is where the magic is

I went to a RS prize lecture on NMR - will see if I can dig out the video. She was a superb lecturer and I learned quite a bit

I assure you a void and a perfect vacuum are valid concepts. The observer would not observe anything but experience ''darkness'' in a perfect vacuum or a void because of the obvious that there is no light. However the observer can determine there is still space by having the ability to move limbs

 

I am sure empty space ''exists'' but the problem would be how to empty that space.

It doesn't. Even empty space is full of spontaneously appearing particle/anti-particle pairs; alternatively we could say that even empty space is permeated by a field and there is a zero-point energy. We can even measure the "pressure" that this exerts by placing two plates very close to each other - this is one heuristic explanation of the casimir effect

I didn't frame my question properly - I meant to say that in the hypothetical scenario each room was pressurized individually and the hole is about 2m x 1m. I screwed the question up.

 

If anyone cares to take another shot -- otherwise, thank you to all who responded. You're classy, here.

Frankly any architect that didnt design a few doors that failed safe in event of a pressure drop should be shot - it is an obvious design feature. Frankly a standard door resting open on a gentle hinge that is able to swing shut would slam shut with the wind - it would then be held tight shut by the pressure. If every junction between rooms was a small (10cm) space with a door opening into the room on each side - where ever the pressure leak was one of the two doors would slam shut and be held shut. The room with the leak would be isolated by the wind rushing from the two adjacent rooms and slamming the doors into that room

I've noticed at least some of this material that is referred to as "reactionless" in the popular media coverage but then when you actually read the underlying work that turns out not to be a claim made by the people involved. So it sort of depends on what you're looking at. I didn't see any physics violations in the one I read, but it was absurdly impractical. Like milli Newtons of force for thousands of watts of power invested. The only application I could ever see it having even a chance at would be satellite station-keeping. I've got a buddy online who's just convinced it's "star drive here we come," but... no.

They are reactionless - or at least claim to be. They have become wise to the fact that this requires them to explain how they are circumventing the conservation of momentum so they don't go on too much about this - frankly their explanations as to the theoretical reasons are balderdash.

Think about it this way - they claim that if you threw an imaginary sphere around the contraption in space that it would move forward with nothing leaving the imaginary sphere. That is to say that the system would undergo a net change in momentum with no external force; this breaches the conservation of momentum. Personally I think a decent amount of the thrust is of thermal origins (that is not reactionless), that some is due to magnetic interactions with support apparatus (that is external to system), and other things that have not been taken care of.

Phew

I think I have adequately shown that it is complicated Even if I was trying to do so much more

»Hvis man kan sætte sig ind i kvantemekanik uden at blive svimmel, har man ikke forstået noget af det,« Bohr

I have posted this in Danish as it seem this is probably about as understandable as my example

Whilst sometimes it is necessary to ask complex multifaceted questions it can be highly instructive to try and break these down to "component parts" to find out if there exists a nucleus of ethical objection on a far more basic level.

It would seem to me that your question has three important parts

1. Is it ethical to use embryonic cells?

2. Is it ethical to create animal human hybrids / chimeras? *

3. Is it ethical to utilise animals to provide medical cures for humans?

These are answerable separately and if (big if) one can answer them then and only then can you move forward to a synthesis and provide an argument that the specific combination of your original question is also answerable.

*I also think this is a highly emotive usage and think fiveworlds made a good point about limitation both within the animal and the species

 

I have to admit that I have no idea what you are talking about imaatfal

I mean the example you posted is very clear to me but I fail to see where to find a correlation between the unknown card setups in your example and quantum entaglement/superposition states.

I'm pretty sure that quantum mechanical type superpositions & entaglements have no relfection in poker ?

 

There is no connexion - exactly as you said. There is no reflexion in poker.

Sorry I was unclear. I was attempting to show how far from an unknown pair of cards that an entangled pair would be - obviously my analogy failed dreadfully. The point of the final measurement being completely unimaginable and impossible in poker is that entanglement is radically and fundamentally different from a mere state of being unknown.

I would try again without introducing cards - but frankly the best example is the Bell Inequality and Experiments and the OP has issues with that already.

Whether a particle has no specific state before one decides to look seems pretty irrelevant. However if you could give an example of how it becomes relevant, Id be open to considering it.

 

The following is not true - but it gives an idea. You have two cards A and B - one is an Ace the other a King; you do not know which is which. With classical cards you could say that measure card A by pairing with another known card and then turning the unknown over.

So if we measure card A by pairing with a Queen and measure card B by pairing with another Queen. If you get Ace Queen with card A you must get King Queen with card B. This would be the same if the Ace and King were in superposition

But if we measure card A and card B DIFFERENTLY - ie we measure card A with a Queen and Card B with a new Ace. Then with the classical measuring that if you get Ace Queen with card A then ALWAYS you will get King Ace. But with a superposition and with a different measurement of the two entangled particles (this is the equivalent of measuring on different axes in Bell Experiment) if you got Ace Queen with card A there would be a possibility that with card B you would get King Ace and also a possibility you would get Ace Ace