Detecting a voyager-like object

[Ingolifs]

The comments section on one of the news sites I frequent were discussing the ultimate fate of the voyager probes. What they actually said is beside the point, but it got me thinking.

If an object, similar in size and makeup to a space-probe, and obviously not naturally ocurring, drifted through our inner solar system, would we be able to detect it?

[mfb]

With our current technology... only if it hits or nearly misses the earth, I think. It is in many ways similar to a random rock with the same size. Maybe the cross-section for radio waves is a bit larger as it has conducting metal (not sure how the Voyager probe will look after millions of years in space). At the moment, there are still kilometer-sized objects in the asteroid belt we did not find yet, and in the Kuiper belt we just began to find objects with 1000km+ diameter.

[SlyReaper]

If it was broadcasting stuff, then maybe. Otherwise it would be extremely unlikely with current technology. You could conceivably detect it if the hubble telescope happened to be looking in the right direction at the right time, but the chances of that are so slim it's barely even worth mentioning.

[Kang]

A debate about the infamous Drake equation once led me to a similar idea:

If we knew we were doomed as a civilisation (knowing that seriously with a bit of a real deadline), a way of 'telling the universe' we were ever here could go right along those lines. Not a voyager probe for obvious reasons, but a small and complicated object, which just obviously could not have come about in a natural way, then enclosed in a massive body and shot into space. Basically creating an artificial asteroid that'll coast around the universe and possibly impact on anything sooner or later.
If that would work you could basically dig up evidence for extraterrestrial life from the ground.

[mfb]

I would paint one side of a massive object (reference intended). With real color, and with some rare elements you would not expect there naturally. Easier to find than a meter-sized object, even in another planetary system. And you give several systems the possibility to detect it.
And send out electromagnetic radiation. Let the earth glow in radio frequencies!

[idobox]

Build a bunch of identical wideband antennas, plug them to identical multimodal resonators (weird shaped metal boxes). Tie them to a long rope or pole, and send that into space. Or even better, make a 2D array of them.
It will have a huge radar cross-section, very dependent on the frequency, that will show it's definitely not natural. You can even code a message in the spectrum.

[Roĝer]

If somehow the object was still functional, that would mean it has to have some energy source, so it could be warmer than the surrounding space, which makes it easier to pick out. This could be by solar energy, although solar cells would not be any use in interstellar space, or maybe by some kind of future tech reactor that somehow still works after 40 000 years.

[thoughtfully]

I have a hard time seeing how a civilization would equip a probe, even if they could, with a 40000 year energy source, when a 400 year source would be abundant, and cost/weigh/take up less space by a factor vaguely resembling 100 times. Unless of course, 400 years isn't abundant, and they really do reckon timescales of 40000 years as something useful to plan for

I suppose.. if the power source isn't a significant constraining factor in the overall design. That would be an advanced cilivization

[Yakk]

Oh, that is easy. You design a power source that, while it doesn't malfunction, just doesn't stop producing power.

You then attempt to boost its reliability as high as you can, because this reduces headaches. I mean, your civilization uses a few million of these power sources, and who wants to break the drywall to fix the generator you put in the wall in your grandparent's time? So much hassle.

So it gets improved and improved and improved over time.

An analogy might be LED lights -- currently, their technology lasts for ~20 years of use (estimated) -- add a few more iterations of reliability, and you could easily imagine LED light bulbs that outlast the drywall you mount them in.

From the perspective of a previous age, why bother making a light source that lasts ~20 years? I mean, you won't be using one longer than a single night, and even that is rare! Just get a new one the next day.

Now, you might say "turning electricity into light is different than turning differentials between two kinds of dark matter flows into electricity", but it really isn't.

[Zamfir]

A very robust light source can be created by just collecting a bunch of hydrogen atoms together. Make it roughly the right amount, and it burns for billions of years without maintenance. It will even withstand most disturbances that are likely the be encountered over such a time period.

[jmorgan3]

A very robust light source can be created by just collecting a bunch of hydrogen atoms together. Make it roughly the right amount, and it burns for billions of years without maintenance. It will even withstand most disturbances that are likely the be encountered over such a time period.

Isn't there a risk that the products of fusion will develop sentience and surpass your own civilization in notoriety?

[Zamfir]

A very robust light source can be created by just collecting a bunch of hydrogen atoms together. Make it roughly the right amount, and it burns for billions of years without maintenance. It will even withstand most disturbances that are likely the be encountered over such a time period.

Isn't there a risk that the products of fusion will develop sentience and surpass your own civilization in notoriety?

From the looks of it, not really. It has been done trillions of time, and all you get is some carbon-based pond scum on the debris that's left over when you build your light source. It sure looks funny, and you could even call it "sentient" if you want to stretch the concept. But not "surpassing" or "notorious".