New way to find expantion?

wolram

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http://www.science.psu.edu/alert/Chartas11-2000.htm [Broken]

in an earlier thread i asked if it would be possible to
support the evidence for expantion of space by useing data from pulsars.
while trying to find data for my hypothosis i came across
this site.
as it is dated 2000 what advances were made if any?
i have found some evidence that pulsars could aid this
research.
 
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Nereid

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lensed quasars and the Hubble constant

from the article Most attempts to measure time-delays until now have been made in the optical and radio bands. [...] For example, it has taken almost 20 years of optical and radio monitoring to obtain a universal accepted time-delay for the lensed quasar Q0957+561 to an accuracy of 3percent
This method is a powerful, independent check on the 'distance ladder', because a good estimate of distances can be made (more or less) directly from geometrical considerations.

How could you use gravitational lensing with pulsars? What would such observations reveal?
 

wolram

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the primary reason for this research is to confirm or
maybe improove the estimation for the hubble constant

an offshoot is that it can give good results on distance
from earth to lensing galaxy

the big problem "for me", is light is the ruler, it would
be neat if an alternative could be used.

it occures to me that as ligh is EM and can be "lensed",
then other parts of the spectrum, radio, x rays, etc can
also be "lensed", so pulses from a pulsar would arrive
at different times according to the path they have taken.

the pulsars distance from lensing galaxy.
 
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wolram

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http://thinkquest.master.eu.org/timing.htm [Broken]

If we want the TOA to indicate the real effects connected with the pulsar's changes, we need to level some disturbances , which are in most the effects of the Earth's rotational and orbital movement. To avoid them, we refer the TOA to the theoretical time that is the time of arrival for the point of Solar System's barycentre. It is the point that does not indicate any movements coused by the gravitational attraction of Sun, planets and other bodies in the Solar System. Other effects come from the existence of the mentioned interstellar medium which influences the signal. Also the transversal movement of the pulsar can disturb the readings. The time standard used to be compared with the pulsars signals are the most exact atomic clocks.
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sorry if this is of topic, but i thought it may be of interest.
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i have just listened to a few pulsars ,the signals are not clean
as in dot, dot, dot, they seem to have leading and trailing edges
im not sure if this is from the source or if it is distortion,
it maybe that individual pulses contain information.
 
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Nereid

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One of the cool things about gravitational lensing is that it is grey (or colourless) - the effect is the same at all wavelengths (I guess there may be some second order effects). In fact, that's one of the key tests used to show the variability is due to lensing, and not some other cause.

The extract you posted gives a neat summary of some of the work needed to isolate real changes in the source, cf local influences (marcus referred to some of these in passing, in replying to my post in the other thread). Fortunately, the relative motion (and postion) of any point on the Earth's surface - compared to the barycentre - can be calculated very precisely.

The ISM, being a plasma, does affect the propogation of radio waves; it's somewhat similar to the twinkling that stars show when you look at them at night - the atmosphere affects the passage of light; the ISM affects the passage of radio waves.

IMHO, pulsars beyond the local supercluster won't be much help with your quest - AFAIK, only a handful have been detected (pulsing) in wavebands other than radio (e.g. the Crab), and none outside the Milky Way (tho' I'd not be surprised if some had been found in the SMC or LMC).

The sounds of pulsars? Later!
 

wolram

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i forgot about ionized hydrogen emiting, interfering
with radio signals.
the fact that lensing is grey, "perturbs all wave lengths
by the same amount",did suprise me, intuitivly i would
have said that high frequency signals would be more
prone to scattering.

thankyou NEREID.
 

wolram

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548
http://www.soton.ac.uk/~pubaffrs/02003.htm [Broken]


The pulsars' unobscured location in the Small Magellanic Cloud (SMC), a neighbouring galaxy, provide a unique insight into the X-ray pulsar phenomenon, in which these objects erupt suddenly and randomly with an outpouring of X-ray radiation for days, weeks or months at a time. Each outburst glows with the intensity of 10,000 suns.
 
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So a kinda simple question, does the light from a distant source get affected diffently/differentially dependant upon the angle of inclination of disc of the interceding (lensing) galaxy?

If so, how is that either computed, or compensated for??
 

wolram

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http://www.iam.ubc.ca/~newbury/lenses/research.html [Broken]

Here is a simple model of Gravitational Lensing. Light emitted from a source bends around intermediate mass usually called the deflector or cluster mass distribution, according to Einstein's Theory of General Relativity. Not all the light emitted from the source reached the observer, only that light which bends through the correct angle.
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this is the best site i have found so far, im stuck with
land line, if you have BB then there are film clips.
 
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