Galileo’s telescope

Pretty self explanatory.

I really love images like this which give perspective. Am I reading this right that our radio waves have traveled only as far as diameter of the blue dot?

http://fieldmuseum.org/explore/depar...oology/insects

It seems off. The galaxy is about 100,000 light years across, and we've been transmitting for about 100 years, so the diameter of the blue dot should be about 1/500 of the diameter of the galaxy. Quick measurement gave a 2 mm diameter of that dot at a certain image size, so the whole galaxy would have to be 1 m, but it was only about 34 cm. So I would think that the dot should be about 3 times smaller. What I am I missing?

I didn't even think to question the accuracy of the image but this is a good point. Something else I didn't think about was the viability of being able to notice transmissions from a very long distance, in reality our bubble is much smaller.

I'd like to know what the maximum potential distance using existing equipment we could attain (if focused and amplified), i.e. the furthest star we can send a noticeable signal to.

Did you make the obvious mistake of measuring the blow up and then compare it to the original by chance, just checking.

I thought so at first, but then I viewed the pic in full size. Here I cut out the part with the smaller blue dot with a ruler below. The dot is 2mm in diameter.



As far as the whole pic goes, I'm getting a bit over 73cm, as seen in this pic below:



I shrunk down the pic some, but the 20cm ruler fits across 3 times and then there's 13.x more centimeters on the last on the right.

This is pretty good work dude! Only it looks to me from your first picture the dot is less than 2mm. Maybe closer to 1.5 mm, no? 73cm/1.5mm is pretty close to 500/1.

This is a good point. Maybe another equally technologically advanced society 100 light years from us may not be able to watch our loony toons and laugh at Hitler like we all do, but if they could pick up the signal at all I'll bet they could figure out it isn't just a simple quasar and probably a product of some other intellegence.

73 cm is the whole image. I measured the galaxy part which is 59 cm on his image, though there could be stars beyond that. His dot looks to be 2.5 mm, not 1.5 mm, though it is hard to read the scale because the hash marks don't look even. 59 cm/2.5 mm = 236/1. I got 170/1 before, and of course I measured both at the same scale.

Ah, yes you're right the galaxy is only 59-60 cm across depending on where you think the cloud of stars ends. I don't see how you get the dot is 2.5mm. When I zoom in on it closely (using my iphone here) it's clearly less than 2mm though the ruler is anything but precise of course.

I checked it again, and it looks like 2.5 plain as day. I'm looking at the whole diameter of the dot, so you have to look up. Maybe your phone doesn't resolve all the hash marks? On my monitor, the first 2 hash marks appear closer together than the next 2.

When I blow it up, there are clearly stars all the way out to the left edge of the image. Also, my dot may have been closer to 1 mm than 2 mm on my original measurement. So the 280/1 is probably closer if you only measure the dark part of the galaxy. About 330/1 if you measure the whole image. An image editor could do a more accurate job.

Let's try that again, the dot is 6 pixels, not 5.

I looked at the pixels with an image editor (because apparently I have nothing better to do) and I get numbers between 375/1 and 442/1 depending on where the galaxy starts on the left. The dot goes from pixels 2284 to 2289 so it is 6 pixels wide. Measuring to the outside of the arc of the galactic halo goes from about pixel 400 to 2650 so it is 2250 pixels wide. 2250/6 = 375/1. If we take everything on the left to be part of our galaxy and measure from 0 to 2650, that gives 442/1. So it's close since pixelation could account for up to a 1/6 = 17% error. The outermost pixels of the dot are dimmer in the vertical dimension than the horizontal dimension.

In any case, yeah, we've covered next to nothing.

We can hardly detect planets today, so how could we possibly detect any signal not sent with laser precision to our location from other starsystems. Seems like the whole SETI program has been about detecting advanced civilizations within 50ly(if they have some earth sized parabola to detect us first) that can't make the journey but want their presence known. Seems pretty far fetched to me.

I checked it on my iPhone, and I still see that it is about 2.5 mm. The left edge is on the long 10 hash mark, and the right side is between the 2nd and hash 3rd to the right of that. The first hash after the 10 looks closer to the 10 than to the next hash mark. This is also what I saw on my CRT monitor (4:3 aspect ratio, not 16:8 flatscreen).

Sometimes non-square pixels or different renderings of images on different devices can stretch objects horizontally, and sometimes they can stretch them differently for small objects than wide objects. I'm not saying that's what's going on here.

off topic:

Scientists snap a picture of DNA’s double helix for the very first time

There is a significant difference between what I get counting pixels vs. what we get when we measure on the screen. For the whole image edge to edge counting pixels I get 2795/6 = 466/1. Measuring on the screen I get 290/1, and that agrees almost exactly with the 292/1 for ganstaman if we use 2.5 instead of 2 for the dot.

How come we haven't had that picture long before now?

we used X-ray crystallography for reconstruction this is direct TEM imaging

linkziz: http://www.newscientist.com/article/...irst-time.html

http://pubs.acs.org/doi/abs/10.1021/nl3039162

Maybe it's at the end of that other spiral arm. Too bad that's 50,000 ly away.

I see. The problem wasn't the resolution, but getting it to hold still for the picture.

Okay, so our broadcast area in comparison to the rest of the galaxy is so small it practically cannot be represented on a normal sized picture. That's pretty crazy!

We've discovered quasars from billions of light years away, but they were powered by supermassive black holes. Does anyone here know how weak a signal we could detect and discern from background static these days? If radio signals of similar strength to our own were broadcast from the other side of our galaxy 50,000 to 100,000 years ago, could we detect them?