Official "Science News" Thread

[science_man_88]

Originally Posted by cheesehead

A couple of clicks gets you to http://phys.org/news/2013-01-astrono...-universe.html where the article has a chart from which you can estimate the apparent angular size.

Looks like about 1/4-1/3 radian to me.

if it's a quarter of the radius of a circle then 4 billion light years * 4 = 16 billion light years distant, if 1/3 then 4 billion light years *3 = 12 billion light years away. thanks for the help.

[cheesehead]

Originally Posted by science_man_88

if it's a quarter of the radius of a circle then 4 billion light years * 4 = 16 billion light years distant, if 1/3 then 4 billion light years *3 = 12 billion light years away. thanks for the help.

... except that:

(1) it's never said that the 4GLy dimension is perpendicular to our line of sight, and

(2) nothing whose light we now see can be more than 13.7 billion light-years away in a 13.7-billion-year-old universe.

[science_man_88]

Originally Posted by cheesehead

... except that:

(1) it's never said that the 4GLy dimension is perpendicular to our line of sight, and

(2) nothing whose light we now see can be more than 13.7 billion light-years away in a 13.7-billion-year-old universe.

I'll admit I never thought about that, now that I do if it's 1.6 billion " in most directions" that 1.6 billion puts it between 4.8 and 6.4 billion light years away to fit the rough radian measures suggested. meaning the tail end should be between 8.8 and 10.4 billion to fit the 4 billion being completely parallel. I'm guessing this is not going to matter either.

[LaurV]

Looks like you are talking about the money I am going to make finding prime numbers...

[xilman]

Originally Posted by cheesehead

... except that:

(1) it's never said that the 4GLy dimension is perpendicular to our line of sight, and

(2) nothing whose light we now see can be more than 13.7 billion light-years away in a 13.7-billion-year-old universe.

Number 2) is false.

Think about it. If you don't see why, I'll post the solution.

[Brian-E]

Originally Posted by xilman

Number 2) is false.

Think about it. If you don't see why, I'll post the solution.

My attempted solution:
The space between us and distant objects has expanded since the light we now see left the object being observed, so it is further away than the distance actually covered by the light.

[science_man_88]

Hubble Telescope to take new 'deep field' views of universe

The Hubble Space Telescope's iconic "Deep Field" photo wowed the world in 1996 by revealing a huge collection of galaxies hiding inside a patch of the sky that looked like nothing more than blank space. Now NASA plans to image six more "empty" bits of sky for a whole new set of deep fields that could revolutionize astronomy once again.

Since the original photo's release, Hubble looked even longer at the same spot to create the "Ultra Deep Field" in 2004 and then the "eXtreme Deep Field" in 2012. But the new effort, called Hubble Frontier Fields, will be the first to try a similar technique on some new areas of the heavens. These photos won't go quite as deep as the Ultra Deep Field, but will represent some of the deepest images of the universe ever taken.

[xilman]

Originally Posted by Brian-E

My attempted solution:

Give that man a cigar!

[chalsall]

Originally Posted by xilman

Give that man a cigar!

"Light cone" anyone?

[cheesehead]

Originally Posted by xilman

Number 2) is false.

Nope.

Think about it. If you don't see why, I'll post the solution.

Perhaps you and others mistake the meaning of my phrases "whose light we now see" and "can be". Of course, I could have worded it more clearly...

Something whose light we now see may have emitted that light quite a while ago, but never more than 13.7 billion years ago, according to current estimates of the time since Big Bang.

Calculating the supposed "current distance" (including cosmological space-time expansion) to that object as of "now" is irrelevant to my statement, if that's what anyone is thinking about.

It is a standard assumption in astronomy that, unless otherwise specified, when a distance to an object is mentioned, that means what its distance is according to how far the light we now see has traveled. So when I wrote "can be", I meant this light-travel distance, not the cosmological distance adjusted for space-time expansion since the light was emitted.

In a 13.7-billion-year-old universe, no light we now see can have been traveling for more than 13.7 billion years.

I suspect that your "solution" may depend on a different interpretation of my words than what I intended.

- - -

Furthermore, the meaning I intended (distance according to light travel time) is consistent with what I perceive as the intent of davar55's and science man 88's posts, which are the ones to which my statements were directed.

[cheesehead]

Now, to the subject I had in mind when I checked in here today:

Some of you may have seen/heard that wildfires in Australia have menaced the Siding Spring Observatory, home of the largest optical telescope in Australia.

Here is a blog description with photos: http://amandabauer.blogspot.co.uk/20...day-after.html

Summary: It appears so far that none of the large telescopes were damaged, but several residence buildings at or near SSO have been damaged or destroyed.

Note: A different Australian observatory, Mount Stromlo Observatory, suffered major damage in 2002 when a wildfire swept its site.