Ah yes. This must be in the Mutara Nebula. Take permits many.

Sadly, we haven’t been pumping out RF that can pierce the ionosphere very long at all, but in the future our high power radars and broadcast stations will hopefully reach someone out there since they are narrow banded. I don’t know the maths for signal attenuation per light year though.

Hello u/lukinhasb, your submission "Would an Earth-like planet with identical technology be able to detect signals from us?" has been removed from r/space because:

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Oh yeah? Who's going to stop me from going there?

RF engineer here.

This is an excellent question that I wish more people would think about. Almost every RF signal generated by humans would be impossible to detect by another earth even a few light years away due to spreading loss.

Detection of a link across interstellar distances requires all of the following:

• Extremely high transmit power (megawatts)
• Extremely high gain, highly directional transmitter (e.g Arecibo type dish)
• Extremely high gain, highly directional receiver (another Arecibo)
• Both antennas pointing exactly at each other at the correct time (the beamwidth of Arecibo was just a few arcmin, covering about 5e-8 of the sky)
• Extremely narrow bandwidth and/or completely deterministic signal (very little information)

Our terrestrial RF emissions do not meet these criteria and could not be observable by another earth. Certainly not broadcast signals like radio/tv. The only signals that possibly could be detected are the few times we have intentionally transmitted a beacon from Arecibo, but given the infrequency of these, the likelihood anyone was listing in our direction is very low.

Feel free to play with this tool yourself: https://www.satsig.net/seticalc.htm

Edit: I just ran the numbers: an Arecibo-like dish (300m, 20K noise temp) could detect a typical TV broadcast (1MW, 6MHz, 0dBi antenna) to a distance of 5.3AU, about the distance to Jupiter.

Sure, if you're looking for that kind of signal I guess!

Though bear in mind that repeated radio signals like that also exist in nature in the form of things like spinning black holes and neutron stars.

If we were looking in the Cosmic Background Radiation for subtle repetition, we probably wouldn't be able to differentiate it from natural sources.

Also bear in mind that the other reason such signals get lost is also because they fall below the signal strength of the CBR, and get entirely overwhelmed, not just masked in the random noise.
I'm not expert on signals-analysis or radio-waves, but I don't think there's a way to extract meaningful data out of that.

Tricky and energy intensive to produce.

Doesn’t count as that is not our current technological development.

Laser light would be more efficient but you would have to know where to point the laser.

Probably something that would need to be "negotiated" with radio communication first to convey specifics of wavelength though.

No that's just your mom's ass

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>How close would an Earth-like planet need to be to detect our signals, and what signals would be easiest to detect at this distance?

The wave front of our radio broadcasts are around 100 light years away. TV broadcasts are just radio signals. With a large enough radio telescope, someone could in principle detect those signals. The signal attenuation over that distance would make it very difficult to seperate signal from background noise.

>How does this distance compare to the observable universe, and what does this mean for the search for extraterrestrial life?

100 light years / 13.8 billion light years. Identifying a technosignature would answer the "are we alone in the universe" question but the further away the origin of the signal, the less chance of engaging in meaninfgul dialogue with any discovered species.

>Is it theoretically possible that there are signals from developed civilizations that we haven't detected yet because it hasn't reached us here on earth, because of speed of light limitations?

Yes. There also may be centuries millenia worth of signals we didn't detect because we weren't even capable of looking for them more than 100 years ago.

The milky way has a couple dwarf satellite galaxies close by, including the small and large Magellanic Clouds

I’ve seen it suggested that our most powerful telescopes would struggle with separating Earth-like signals from cosmic background noise from sources around 100 light years out. The distance could be increased if someone was intentionally focusing high powered communications directly at us wanting to be seen, but as far as detecting incidental signals it’s not very far out with respect to the the vastness of the galaxy.

In terms of searching we’ve barely looked around the galaxy. That being said, there’s about 60,000 stars within that radius. So the sample set isn’t zero.

National Geographic (and others) have done whole episodes on this topic.

https://www.nationalgeographic.com/science/article/how-aliens-could-discover-life-on-earth-one-strange-rock-science

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yes

I love how new discoveries keep challenging the theories we currently have. Show how little is known about the space and how much we have yet to learn.

Is there a way to deal with that - surely if you average over time then you can pick up even a very weak signal if it is repeated often enough. If we had a constant brief repeated signal at regular intervals over, say, the course of a year - wouldn't that be enough to be detected among noise if averaging was used?

He’s a troll with a weeks old account. General rule of thumb on Reddit- check the profile and anything under 3/4 months old is probably a troll, whose life is so pathetic that they spend their days trying to annoy/anger strangers on the internet.

Please don't stop learning nor asking questions. Space is fascinating and even physicist ask questions. Question everything! Godspeed, my friend.

Can't catapult people into space - the forces generated by the catapult system exceed 10,000g. People can usually handle about 9g before bad things start to happen and will become mush well before hitting 10,000g. Pretty much restricted to non-compressible things if we're going to launch them via catapult.

And then there's the return trip, deceleration, landing or splashdown, etc. All of these things require energy and are replete with opportunities for catastrophic failure. And you'd need thousands of ships returning each day to get any meaningful amount of water (see below).

As far as where to put the salt, back in the ocean is fine. It's simply not possible to remove so much fresh water from the oceans that putting the salt removed back into the oceans will make a significant (or really even noticeable) difference. Sure, the actual dumping points will be impacted, but the oceans generally will not be.

Here's the basic math:

The average person used 3,800 liters per day of water. Let's say that we learn to reduce that by 75% (which is highly unlikely). That takes it down to about 1,000 liters per day per person, or 8 trillion liters per day worldwide. Now let's assume we want to get 10% of that from extraterrestrial sources - that's 8 hundred-million liters of water a day, every day, which is 8 hundred million kgs brought in each day every day (or 8 hundred thousand metric tons). The largest payload we can launch currently from Earth in one launch is about 17 metric tons. Granted, we're not launching from Earth is we're harvesting ice off-planet, so let's assume we can (somehow) launch 100 times the amount from somewhere else (a silly assumption, but we'll doit anyway). So now we can lift (from Mars or wherever) 1,700 metric tons of ice/water on one launch. To supply just 10% of the GREATLY reduced water consumption needs of the Earth under these incredibly favorable and ridiculous assumptions, we'd need about 500 unbelievably huge ships (each one carrying a payload measuring 1,700m x 1,700m x 1,700m, or nearly 5 billion cubic meters) delivering ice/water each day, every day. The Astrodome - a huge stadium that fits 68,000 people, is only 1.2 million cubic meters in volume, meaning we'd need to bring over 4,166 Astrodomes worth of water just to meet 10% of the needs (again assuming great reduction from current usage). And somehow we'd need to launch enough ships, parts, people, fuel, etc. to carry on this mission.

And even if this was a one-time project to just add to the water supply on Earth, the new water would immediately join the same water cycle as the existing water, so we'd have to be desalinizing and or decontaminating the newly arrived water as well.

Nothing changes the bottom line - it will always be easier and cheaper and more environmental friendly to deal with the water already on Earth than to try to get a meaningful amount from elsewhere.

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Come on, guy. u/OhioVsEverything is just trying to learn, why the shitty attitude?