Extent of human radio broadcasts photo

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Discussion Overview

The discussion revolves around the extent of human radio broadcasts as depicted in a photo relative to the Milky Way Galaxy. Participants explore the representation of this extent, the implications of the distances involved, and the feasibility of capturing images of the Milky Way from various perspectives.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants suggest that the extent of radio broadcasts should be represented as a sphere rather than a square, indicating a preference for a more accurate depiction.
  • There is confusion regarding the blue circle's representation, with some believing it indicates the extent of broadcasts while others argue it is merely highlighted by the square inset.
  • One participant clarifies that the blue dot in the inset photo represents the 200 light-year zone of radio transmissions from Earth, emphasizing its insignificance compared to the Milky Way's size.
  • Several participants humorously acknowledge the limitations of human radio broadcasts, noting that transmissions have not yet reached 200 light-years due to the relatively short history of radio technology.
  • Questions arise about the feasibility of capturing a direct image of the Milky Way, with some participants referencing concept art and discussing the challenges of obtaining such images from a specific angle.
  • There is speculation about the time it would take to send a probe to capture images of the Milky Way, with some participants expressing skepticism about current technology's capabilities.
  • Participants debate the practicality of achieving speeds necessary for intergalactic travel, with some suggesting that time dilation could allow for faster travel without exceeding the speed of light.
  • Concerns are raised about the limitations of current propulsion technologies, with references to ion drives and the challenges of reaching distant celestial bodies.

Areas of Agreement / Disagreement

Participants express a range of views on the representation of radio broadcast extent, the feasibility of capturing images of the Milky Way, and the practicality of advanced space travel technologies. No consensus is reached, and multiple competing perspectives remain throughout the discussion.

Contextual Notes

Participants highlight limitations in understanding the distances involved and the technological challenges of space exploration. There is an acknowledgment of the assumptions underlying discussions about speed and the capabilities of current technology.

  • #31
Using the formula for Free Space Path Loss given by http://en.wikipedia.org/wiki/Free-space_path_loss and the capabilities of the Arecibo Observatory http://en.wikipedia.org/wiki/Arecibo_Observatory, the range for three scenarios can be calculated.

Frequency...Effective Radiated Power...Distance
2.38 GHz...20 TW......0.669 ly
0.43 GHz...2.5 TW......0.300 ly
0.047 GHz...300 MW........0.00586 ly

For this calculation I assumed an Arecibo type antenna at both ends and a receive sensitivity of -120 dBm. Even though Free Space Path Loss is higher at higher frequencies, it is offset by the higher transmitting power and higher antenna gain. It looks like the best we can do is still a long ways from 200 ly.
 
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  • #32
jackmell said:
Funny. It is of course a real galaxy. Spiral-barred I believe. Would be nice anyway to know which one. And we can actually construct a picture of what the Milky-way looks like from afar. Would have been better I suppose to have used that one so no . . . explanations would be necessary.

Bet if you posted that galaxy picture in the Astronomy forum and asked which one it is without looking it up, there are some there that would know.

You are absolutely right. . Should we really take their word that is is the real and original Milky Way? It could be a fake.
And that little sign with the arrow that says "You Are Here"? Who put that there?
 
  • #33
micromass said:
I wonder how they took that picture of the milky way...

Lol micro, I had that same thought :biggrin: :-p!
 
  • #34
Micro is definitely pulling your leg :-p although his jokey attitude is one we get here frequently, and for real.

I'd love to see an accurate (as much as possible) picture of the Milky Way taken by photographing all the stars/nebulae/etc we can see from our solar system, measuring their positions and creating a 3D image we can rotate and examine. That's obviously less simple than it sounds though.
 
  • #35
Ryan_m_b said:
Micro is definitely pulling your leg :-p although his jokey attitude is one we get here frequently, and for real.

I'd love to see an accurate (as much as possible) picture of the Milky Way taken by photographing all the stars/nebulae/etc we can see from our solar system, measuring their positions and creating a 3D image we can rotate and examine. That's obviously less simple than it sounds though.

I tried (little bit) and could not find the picture I saw some years ago, a "composite" picture of what our galaxy would look like say a million light years away. I'll ask in the Astronomy forum.
 
  • #36
micromass said:
Why couldn't we take a picture from that angle?

My goodness, Micro. If I didn't know better. ... :rolleyes:

Anyway here is one of the presently most famous pictures of the Milky Way galaxy, taken by Dr. Axel Mellinger.
http://home.arcor.de/axel.mellinger/
"Between October 2007 and August 2009, I assembled a new digital all-sky mosaic image from more than 3000
individual CCD frames. Using an SBIG STL-11000 camera, 70 fields (each covering 40° × 27°) were imaged from
dark-sky locations in South Africa, Texas and Michigan."​

http://home.arcor.de/axel.mellinger/mwpan2_Aitoff_1200x600.jpg

========================

...I first saw this mosaic, in poster form, at the local telescope shop. My then-girlfriend, the telescope shop guy, and
myself were all admiring it.
...My then-girlfriend asked, "where's Earth?"
Before I could address her question the telescope shop guy pointed to somewhere in the picture and said, "I think
it's right around here."
... I thought to myself, "Ahhh, Jasus balls, no! Not the telescope shop guy!" I cried a little inside.

[Edit: Just in case you didn't get that, Earth (and the whole solar system for that matter) is not in the picture
Earth is where the camera is!]
 
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  • #37
Why the radio waves don't go further? It's just another EM wave, right?
 
  • #38
Radio waves in a vacuum travel at the speed of light.
 
  • #39
Evo said:
Radio waves in a vacuum travel at the speed of light.

Yes, so why are the radio broadcast limited to just the blue dot shown?

Edit: Nevermind. Just went through all the posts.
 
  • #40
jobyts said:
Yes, so why are the radio broadcast limited to just the blue dot shown?

Edit: Nevermind. Just went through all the posts.
The thread title might have given you a hint. :biggrin:
 
  • #41
Hi,

I'd like to correct my post above: After talking to some in the Astronomy forum, the original picture posted in the thread is what is believed to be a relatively accurate description of what the Milky-way would look like from a distance. It is however not quantitative as we cannot easily measure stellar distances in the galaxy beyond about 4000 light years and so is only a rendition. The picture is not some other galaxy as I original believed. Also, the picture of the Milky-way I was referring to above was similar to the picture posted by Collins above which is inside looking out at the Milky-way (I believe).
 

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