Starship Asterisk*

Chris Peterson wrote:

Tara_Li wrote:My understanding was that all three arose from General Relativity, and were essentially the same underlying phenomena appearing in different manners. I'm just surprised quantum theory doesn't throw in its own red shift source. (Or does it? Do photons lose energy through interactions with the background vacuum fluctuations?)

The Doppler Effect is generally considered a classical phenomenon (which applies to other kinds of waves, like sound). The classical description only applies when v is much less than c. A full analysis requires the use of special relativity. Of course, most classical phenomena are only fully described using relativity.

Tara_Li wrote:My understanding was that all three arose from General Relativity, and were essentially the same underlying phenomena appearing in different manners. I'm just surprised quantum theory doesn't throw in its own red shift source. (Or does it? Do photons lose energy through interactions with the background vacuum fluctuations?)

Chris Peterson wrote:

MarkBour wrote:I have not heard red-shift explained this way before. It does not sound at all like the explanations I have heard before, namely that we see red-shift because (at the time of emission), the light source was moving relative to the velocity we have (when receiving the light wave).

Their are different mechanisms that can cause redshift. You're describing Doppler redshift. That is different from cosmological redshift, where space expands while the photon is traveling, and from gravitational redshift, where the wavelength of a photon increases as it climbs out of a gravitational well. Each of these is very similar with respect to observation, but described by somewhat different theory and math.

MarkBour wrote:I have not heard red-shift explained this way before. It does not sound at all like the explanations I have heard before, namely that we see red-shift because (at the time of emission), the light source was moving relative to the velocity we have (when receiving the light wave).

Boomer12k wrote:

Tara_Li wrote:Here's the thing - there's *ALMOST* nothing there, but ... not quite.

Look at the "before" inset. There's a somewhat diffuse glow, strongest on the left, with something of a waist before it brightens back up just a bit (mostly reddish). There's also a somewhat more compact source in the upper left, reasonably bright.

Now, in the "after" inset, there's a brighter glow against the left edge, with almost no sign of that brighter reddish area near the bottom. And that compact source is much more muted. My guess: a molecular cloud of some kind, moving in from the right. Further characterization is left as an exercise for the professional astronomer.

So, it's not quite a dog that doesn't bark, as one that's muffled a bit.

I take astrophotography pictures. Even frames 1 second or less apart can be varied. Earth's Atmospheric conditions can distort things, and cause variations in the image....I KNOW...this is a SPACE TELESCOPE....no atmosphere...but I think there is probably just some camera, and light variations that can cause differences between images....especially DAYS, or Months apart....
I would say...the POST image....has better focus for example...

Just my take on it....

:---[===] *

MarkBour wrote:The last link in the APOD text points to the Dark Energy Survey website. I've never visited that site before. After reading through their overview materials, I noted that in two places, they give the same explanation of red-shift:

This is known as redshift. Objects in space such as galaxies or exploding stars emit light in the form of light waves. As the light waves travels toward the earth over millions or billions of years, the universe continues to expand, lengthening the traveling waves as it does.

(I added the emphasis). I have not heard red-shift explained this way before. It does not sound at all like the explanations I have heard before, namely that we see red-shift because (at the time of emission), the light source was moving relative to the velocity we have (when receiving the light wave).

What is this new heresy?

This is known as redshift. Objects in space such as galaxies or exploding stars emit light in the form of light waves. As the light waves travels toward the earth over millions or billions of years, the universe continues to expand, lengthening the traveling waves as it does.

Tara_Li wrote:Here's the thing - there's *ALMOST* nothing there, but ... not quite.

Look at the "before" inset. There's a somewhat diffuse glow, strongest on the left, with something of a waist before it brightens back up just a bit (mostly reddish). There's also a somewhat more compact source in the upper left, reasonably bright.

Now, in the "after" inset, there's a brighter glow against the left edge, with almost no sign of that brighter reddish area near the bottom. And that compact source is much more muted. My guess: a molecular cloud of some kind, moving in from the right. Further characterization is left as an exercise for the professional astronomer.

So, it's not quite a dog that doesn't bark, as one that's muffled a bit.

geckzilla wrote:Yeah, I sat there for a good few minutes saying to myself there's nothing there and wondering what it was I was supposed to look at before moving on to the reading part.

As Conan Doyle had Holmes say:

Gregory (Scotland Yard detective): "Is there any other point to which you would wish to draw my attention?"
Holmes: "To the curious incident of the dog in the night-time."
Gregory: "The dog did nothing in the night-time."
Holmes: "That was the curious incident.

I love it!

Ann