MathJakob

Great thanks. Just to be clear though, obviously I won't but I want to know for certain... if the case is broken and the contents is ingested, what will happen? I understand polonium 210 isn't poisionous by touch but if you ingest it, it will be fatal. So I want to know is the amount provided lethal if ingested? It would be kept in a safe location but for example if my dog swallowed it or something.

Thanks for the link. What I want to know though is if I bring one of these back from the US, will any gieger counters pick it up? For example when you watch a movie and some FBI person comes in the room holding a gieger counter and says "We have trace amounts of radiation in here". Would this small amount of radiation sold on the sites be detectable to gieger counters are a ranger of like 100m?

There are various sites that sell tiny amounts of radioactive material purely for the purpose of testing gieger counters and I just wanted to make sure that should the container be broken, would I be in any sort of danger? What if I touch it with my hands? For example: I don't want to bring it back from the US and have any gieger counters going nuts at the airport...

Can you link the original source / journal. Thanks.

I don't know if your math is wrong sinse you have not provided any math for us to see.

Hey guys. I have a question about two (possibly ostensibly) different definitions of a locally non-rotating observer that I have come across in my texts. The first is specifically for stationary, axisymmetric space-times in which we have a canonical global time function [latex]t[/latex] associated with the time-like killing vector field. We define a locally non-rotating observer to be one who follows an orbit of [latex]\nabla^{a}t[/latex] i.e. his 4-velocity is given by [latex]\xi^{a} = (-\nabla^{b}t\nabla_{b}t)^{-1/2}\nabla^{a}t = \alpha \nabla^{a}t[/latex]. Such an observer can be deemed as locally non-rotating because his angular momentum [latex]L = \xi^{a}\psi_{a} = \alpha g_{\mu\nu}g^{\mu}{\gamma}\nabla_{\gamma}t\delta^{\nu}_{\varphi} = \alpha \delta^{\gamma}_{\nu}\delta^{t}_{\gamma}\delta^{\nu}_{\varphi} = \alpha \delta^{t}_{\varphi} = 0[/latex] where [latex]\psi^{a}[/latex] is the axial killing vector field; these observers are also called ZAMOs for this reason. It might also be worth noting that the time-like congruence defined by the family of ZAMOs has vanishing twist [latex]\omega^{a} = \epsilon^{abcd}\xi_{b}\nabla_{c}\xi_{d} = \alpha\epsilon^{ab[cd]}\nabla_{b}t\nabla_{(c}\nabla_{d)}t + \alpha^{3}\epsilon^{a[b|c|d]}\nabla_{(b}t \nabla_{d)}t\nabla^{e}t\nabla_{c}\nabla_{e}t = 0[/latex]. The second definition I have seen is the much more general notion of Fermi-Walker transport. That is, if we choose an initial Lorentz frame [latex]\{\xi^{a}, u^{a},v^{a},w^{a}\}[/latex] and the spatial basis vectors evolve according to [latex]\xi^{b}\nabla_{b}u^{a} = \xi^{a}u_{b}a^{b}[/latex], [latex]\xi^{b}\nabla_{b}v^{a} = \xi^{a}v_{b}a^{b}[/latex], and [latex]\xi^{b}\nabla_{b}w^{a} = \xi^{a}w_{b}a^{b}[/latex], where [latex]a^{b} = \xi^{a}\nabla_{a}\xi^{b}[/latex] is the 4-acceleration, then the observer is said to be locally non-rotating. My question is, to what extent are these two definitions equivalent (both mathematically and physically) whenever they can both be applied? In other words, in what sense is the qualifier 'rotation' being used in each case? Let me elucidate my question a little bit. I know that for asymptotically flat axisymmetric space-times, there must exist a fixed rotation axis on which [latex]\psi^{a}[/latex] vanishes. Then the first definition tells us that the ZAMOs have no orbital rotation about this fixed rotation axis (for example no orbital rotation about a Kerr black hole); because these observers are at rest with respect to the [latex]t = \text{const.}[/latex] hypersurfaces, these observers are as close to stationary hovering observers as we can get in a space-time with a rotating source. We know however that such observers have an instrinsic angular velocity [latex]\omega[/latex]; if we imagine a ZAMO holding a small sphere with frictionless prongs sticking out with beads through the prongs then a ZAMO should be able to notice his intrinsic angular velocity [latex]\omega[/latex] by seeing that the beads are thrown outwards along the prongs at any given instant. Is this correct? Now, on the other hand, the second definition of local non-rotation (using Fermi-Walker transport) seems to be saying sort of the opposite. That is, it seems to be telling us which observers can carry such spheres and never see the beads get thrown outwards i.e. the orientation of the sphere will remain constant (the orientation will be represented by the spatial basis vectors of a Lorentz frame) so these are the observers who have no intrinsic angular velocity i.e. no self-rotation. This is why the two definitions confused me because they seem to be talking about two totally different kinds of non-rotation.

Hello everyone, don't worry I'm not looking to kill someone haha I've been watching a TV series called Fring, it's great you should give it a try, Anwyay in some of the episodes the criminals use poisions or toxins which are colourless, odorless and that travel through air, if you breath it in you die. I wanted to ask if poisons like this really exist? In one of the episodes he has some clear white liquid in a sealed glass bottle, he puts it in the air vent and takes the lid off so the fumes travel through the vent system and kill everyone. Just wondering if you could tell me the names of anything like this that actually exists. Strictly for research purposes Thanks.