How can quasars change brightness in days if they're light-years across?

[Phys12]

The video:

When Astrophysicists detected Quasars, they thought that they could not be more than a few light-days across as they were changing their brightness in just a few days. If we assume that they are light-years long, then the change in brightness from the other side would be observed year later, but we see the entire object's brightness change in just a few days.

However, can't it be the case that the closer end changed its brightness so much that it changed our measurements of the entire object's brightness while the change was still progressing through it at the farther end?

 

[Chronos]

According to any number of sources, most quasars vary in brightness over a span of several weeks or a month. While some do vary in brightness over a matter of days, it is not assumed, nor is there any evidence suggesting such rapid variations are representative of an object that spans light years in size. The video confirms these simple facts. Claims that quasars are much closer than their redshift indicates have been repeatedly rebutted over the years and are not seriously entertained by mainstream scientists.

 

[Somnambulant]

Claims that quasars are much closer than their redshift indicates have been repeatedly rebutted over the years and are not seriously entertained by mainstream scientists.

Can you provide any examples of, or pointers to, rebuttals to the claims that quasars are much closer than their redshift indicates?

 

[Chronos]

OK, I'll bite, how about http://arxiv.org/abs/astro-ph/0506366; Critical Examinations of QSO Redshift Periodicities and Associations with Galaxies in Sloan Digital Sky Survey Data, http://arxiv.org/abs/0807.2641; Evidence against non-cosmological redshifts of QSOs in SDSS data, http://www.astro.ucla.edu/~wright/cosmology_faq.html#QZ,

 

[mfb]

However, can't it be the case that the closer end changed its brightness so much that it changed our measurements of the entire object's brightness while the change was still progressing through it at the farther end?

It doesn't change the conclusion: the change in brightness happens in a small region. If the whole object suddenly appears twice as bright as before, then a small region has to emit as much light as the whole object before.

 

[Phys12]

then a small region has to emit as much light as the whole object before.

Which is impossible?

 

[mfb]

Which is possible. But that is the whole point: you can use the sudden luminosity changes to estimate the size of the region where the light (at least most of it) comes from.

 

[Stephen Albert]

According to any number of sources, most quasars vary in brightness over a span of several weeks or a month. While some do vary in brightness over a matter of days, it is not assumed, nor is there any evidence suggesting such rapid variations are representative of an object that spans light years in size. The video confirms these simple facts. Claims that quasars are much closer than their redshift indicates have been repeatedly rebutted over the years and are not seriously entertained by mainstream scientists.

Would you please share some evidence based reference that validates you statement...!

 

[Chronos]

If you fail to comprehend the evidence already presented, you are beyond my help.