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RE: Probing cosmic neutrinos with a giant 200000 km2 detector
The intergalactical medium is a good vacuum. There is very little matter in there. In fact, the universe is mostly empty, except at very well located points so that light travels at 'c'.
Concerning refraction, it always occur at the interface of different media. Since there is not that many of such interfaces in the universe, we are save. Gravity is what bends the trajectory of light.
yes but gravity depends on mass being present so a cosmic cloud of gas must have quite some to it , no ? and "mostly empty" does that count as vacuum, is it REALLY empty ? then that's where the dark matter hides ?
so its basically not empty ... it contradicts itself again , if you had like 1 million cubic lightyears of whats seen as vacuum it would still hold an amount of matter, right ? even if maybe so light that it barely dents spacetime maybe over lightyears it would bend a ray of light, if ever so slightly ? unless there's a treshold at which fotons dont react to it ? i mean below it ?
Density is what matters. A cloud of gas is not as compact as a star so that the deformation of spacetime are way smaller.
There are regions of the universe where there dark matter could be very abundant and those are not empty. But most of the universe is just empty.
A small amount very well localized. That makes the difference. To bend spacetime, one needs matter to be well localized and compact.
i see ... (i just keep asking lol) so what's the treshold for anything to actually bend spacetime ?
i understand a mini-black hole might bend it as much as a very large ultraplanet or star but what's the treshold ? at what number or numbers does it bend ? is there some kind of formula with constants that says "THIS is where spacetime starts to bend under its own weight ?"
and also, i still have a difficult time imagining it makes zero difference, if i may try to find an example.
Let's consider something localized like Terra here, a ray of light, a photon depending on which way you look at it, a dot, shoots past from wherever to whever it is travelling. Assuming the earth is enough to bend its trajectory (here it comes :)
the earth with all the space debris around it (can be considered as one local mass, right ?)
the earth WITHOUT all the space debris around it (all of it, the human waste AND the rest) is less massive ...
right ?
so i can't imagina that does not make even the slightest difference at maybe like 50 digits below the comma but it HAS to make a difference, right ? all those numbers are analogue
quantumfilosophy, here i go again, but that last bit wasn't right ? that was special relativity ? no ? :p
i keep having doubts, which i think is good, right, i once saw one those tv-superstars ... can't remember the name, it wasnt brian cox or muchi kaku
michy
chu lol, someone else, about quantum stuff, and possibilities, timelines and all that
claim he had once calculated all possible "coinflips" (aka timelines /splits) that could have happened since the big bang, and i thought to myself : "this guy needs to get out more" , he was just assuming there's an absolute quantum level at which time can't be divided since if thats not the case the number of coinflips is infinity once you reach moment one , after zero
im fascinated by infinity, in better days, (unstuck in time ofcourse, i should say "was" ... you know i keep saying in theory einstein declared that all you need for any mass to travel light of faster is an infinite amount of energy, and i always get physicists wanting to nail me at the stake for that lol but its just this mathematical thing with infinity and i really mathematically thats what it says ... even if the framework says :" nothing travels faster than light" )
and yea i said this several times before but the actual question was paragraph one lol, the photon and the earth (with or without the debris) will be bent in an ever so slightly different way since the mass is not the same but the "locale" is ... (i know, i am chaos lol, probably a remnant of back when the kid was deemed smart enough by the official state test they took back then when you were 12 to do latin-math ... and the elitist teachers in the catholic schools telling us we were the elite and the rest was "the garbage can", if we couldnt make it he would dump us there, stuff like that ... very healthy to put on a 15 year olds shoulders lol, the damage is done im afraid)