Can we detect a blueshift of -c?
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From: Greg Neill on 23 Apr 2010 14:22 Brad Guth wrote: > On Apr 23, 5:09 am, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: >> Brad Guth wrote: >>> On Apr 22, 1:33 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: >>>> Brad Guth wrote: >>>>> How about photons from a vibrant 10 solar mass star that's situated >>>>> well within our visual detection horizon of 13.7e9 ly, but trekking >>>>> directly towards us at -c? >> >>>> It can't. Nothing physical within our horizon can be >>>> observed to move at or above c. Close to c, sure, but >>>> not at or above. >> >>>> The best a body can do is approach c with respect to >>>> observers in its proximity (within the local region of >>>> space moving with the Hubble flow). Every non-local >>>> observer (such as us sitting a great distance away from >>>> that region in our own local region) sees that region >>>> of space moving away in bulk according to the Hubble >>>> expansion, thus decreasing any net speed of approach. >> >>> I wasn't asking for your subjective opinion of physics. >> >>> I was asking about photons from a vibrant 10 solar mass star that's >>> situated well within our visual detection horizon of 13.7e9 ly, >>> trekking directly towards us at -c. How would we ho about detecting >>> this 100% blue-shift? >> >> See my first paragraph above. >> >> If your observed star is relatively close by, it's observed >> velocity will be limited by an upper bound approaching c. >> The further away it is (and the closer it gets to our >> cosmic horizon), the motion due to the expansion of the >> space between us and it has to be added to its motion >> through space, decreasing the net observed velocity. >> >> Near the horizon, a body moving at near c in its local space >> in a direction towards us will have a net velocity near >> zero (the best it could do would be to stand still with >> respect to us), and so its red shift would be very small. >> >> There is no way for a body to be observed moving towards us >> at c. > That's exactly what I�d thought. If we're moving away or towards > other mass at c, we'd be oblivious to realizing its existence. I don't see why you persist in assuming the impossible. A relative velocity of c or greater is simply not allowed by nature. > > I understand there's a few rogue stars moving at 1500 km/sec, and it's > thought possible that stars further out could easily be moving at .5c, > so what if another star were moving towards the other at .5c, making > their mutual closing velocity c. Due to their relative closing > velocity being c, could either of those fast moving stars notice the > other? (I don't think so) Look up relativistic addition of velocities. Closing velocity, as judged by a third party observer of two separate objects closing on each other, is not at all the same thing as one object moving at c or greater with respect to the other; Each of the stars would see the other as moving towards it at a velocity less than c. Neither star would be invisible to the other. > > It seems anything moving away or towards us at c (relative to us) > becomes stealth/invisible. But nothing can so move. So your conclusions are not logical. > This simply means we�re always at some > degree of risk unless fast moving exogravity can be detected. A > neutron star or black hole closing in on us, even if it were passing > outside of Pluto could be a cosmic form of fatal attraction, whereas > just the gravitational shockwave of one light year radii alone could > perturb and/or traumatize most everything about our solar system. And invisible pink elephants are a threat to ants of the 13th dimension. Makes as much sense.
From: BURT on 22 Apr 2010 20:08 On Apr 22, 4:10 pm, spudnik <Space...(a)hotmail.com> wrote: > there is no direct observation of "moving away;" > it is all presupposition of a "Dopplerian" redshift (probably > related to a belief in Pascal's absolute vacuum; I mean, > he did do the experiment). If light is absorbed sideways to motion instead of head on what kind of energy shift will it have? Mitch Raemsch
From: spudnik on 22 Apr 2010 20:13 that might affect the relative polarization of the wave. many high-energy astrophysical experiments do not bother wtih polarization, even though that's just about all that there is to "see." > If light is absorbed sideways to motion instead of head on what kind > of energy shift will it have?
From: BURT on 22 Apr 2010 20:26 On Apr 22, 5:13 pm, spudnik <Space...(a)hotmail.com> wrote: > that might affect the relative polarization of the wave. > > many high-energy astrophysical experiments do not bother > wtih polarization, even though that's just about all > that there is to "see." > > > > > If light is absorbed sideways to motion instead of head on what kind > > of energy shift will it have?- Hide quoted text - > > - Show quoted text - If from ahead or behind there is an energy shift what about sideways absorption of light? It looks as if angle determines the energy shift. With a maximum, and a zero for 90 degrees to motion. Mitch Raemsch
From: Brad Guth on 23 Apr 2010 00:31
On Apr 22, 1:33 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > Brad Guth wrote: > > How about photons from a vibrant 10 solar mass star that's situated > > well within our visual detection horizon of 13.7e9 ly, but trekking > > directly towards us at -c? > > It can't. Nothing physical within our horizon can be > observed to move at or above c. Close to c, sure, but > not at or above. > > The best a body can do is approach c with respect to > observers in its proximity (within the local region of > space moving with the Hubble flow). Every non-local > observer (such as us sitting a great distance away from > that region in our own local region) sees that region > of space moving away in bulk according to the Hubble > expansion, thus decreasing any net speed of approach. I wasn't asking for your subjective opinion of physics. I was asking about photons from a vibrant 10 solar mass star that's situated well within our visual detection horizon of 13.7e9 ly, trekking directly towards us at -c. How would we ho about detecting this 100% blue-shift? ~ BG |