Then, we people are very soon capable of communicating using quantum entanglement, which means it’s beyond wireless and you simply couldn’t tap into it with some antenna.
For these reasons I suspect that SETI is waste of money.
This is true. The signals we communicate with amongst ourselves would be too weak to detect using present equipment at any distance.
> when it’s encrypted digital data. I mean it’s just noise like any background signal..
This part is not true. A simple spectrum analyzer will show what radio bands are being communicated on and it's clear as day.
> we people are very soon capable of communicating using quantum entanglement,
This is very much not true. This is theoretically impossible. Unless we are very--very--wrong about quantum mechanics, we cannot use effects related to quantum entanglement to communicate.
ELI5 to a non-physicist why not? I thought this was possible, if Alice and Bob share an entangled pair of a set of particles (i.e. each has a clique of particles entangled with the other), and they pre-arrange an algorithm for determining the meaning of different states of their particles.
IIRC wasn't this the gist of the "wormhole" paper that went viral last year (which was criticized for being improperly named, but nonetheless demonstrated a method of "communication" between two locations given a prearranged algorithm for assigning meanings to different states of entanglement)?
It does not mean that if you push on one particle, the other one lights up.
Imagine that two people are each given a coin with the property that whenever they flip those two coins simultaneously, they will either both come up heads, or both come up tails. How can you use that to communicate, that is, send information from one to the other? You can't. You can pre-arrange actions that you both will take when you see either heads or tails, but that's not communication.
I don't fully understand the subtleties, but the root problem seems to be that by measuring the state, you're perturbing the system and putting it into a new state, such that your measurement becomes irrelevant, as if you're always one step behind the message and can never catch up.
> The only way that this problem could be circumvented is if there existed some way of making a quantum measurement that actually forced a particular outcome. (Note: this is not something permitted within the presently-known laws of physics.)
[0] https://bigthink.com/starts-with-a-bang/quantum-entanglement...
Heads = 1, Tails = 0?
It does not allow Alice or Bob the place a die on the table on a specific number and have the other die roll over to that number. If Alice or Bob try to influence the number that the die rolls, it will break the connection between the two dice.
The link I posted downthread seemed to suggest that the No Cloning Theorem is the constraint that makes this impossible. Any chance you can try to explain that within the context of the dice analogy?
Alice and Bob have a dozen dice. They agree that if they roll a 4, that's the signal for "attack at dawn" and Alice has decided that she wants Bob to attack at dawn. Alice rolls the 12 dice, and at the agreed upon time, Bob also rolls his 12 dice. The sequence they get is 1,5,3,2,2,4,6,5,1,2,1,6. The 6th die is a 4, which is the signal that Alice wants to send. How does Alice signal to Bob that she wants him to look at the 6th die? If Alice can send a signal to say, "look at the 6th die", why wouldn't she just send a signal that says, "attack at dawn"?
> If an extraterrestrial civilization has a SETI project similar to our own, could they detect signals from Earth?
> In general, no. Most earthly transmissions are too weak to be found by equipment similar to ours at the distance of even the nearest star. But there are some important exceptions. High-powered radars and the Arecibo broadcast of 1974 (which lasted for only three minutes) could be detected at distances of tens to hundreds of light-years with a setup similar to our best SETI experiments.
It's not really a surprise why we aren't finding things. It's a surprise that we're still acting like this is a good way to look.
I think the real problem is the timing. It seems unlikely that anyone will be looking at the same time anyone else is sending a message.
TO be clear, the signals it is referring to are those that would be similar the unintended leakage of normal broadcast and military radar systems used on earth. So detecting ETIs from their passive emissions is certainly unfeasible that the moment.
Signals broadcast by a hypothetical extraterrestrial civilisation as part of an intentional seti signalling effort would (presumably) use much higher power, narrower bandwidth, and frequencies chosen to reduce attenuation by the interstellar medium. These would be detectable using our current technology, and is largely what seti is looking for.
Just because it's "noise" (ie. random/unpredictable looking) doesn't mean it's indistinguishable from other "noise".
Not all "noise" is created equal. "noise" can have properties that make it distinguishable from other "noise". You may have heard of "white noise", "brown noise", "pink noise", "gaussian noise", etc...
A sequence that appears random or unpredictable may nevertheless fall in to certain distributions.
I am not an astronomer, statistician or cryptographer, but would not be in the least surprised if encrypted communication could be clearly distinguishable from the cosmic microwave background radiation -- not only based on its distribution, but other properties such as intensity of the signal, how frequently the signal appears, and other much more advanced signal analysis techniques which are way beyond my expertise to analyze but not beyond the experts at SETI.
My microwave produces noise but I'd like to think scientists could pick it up with their sensors and say "huh, sounds like a microwave".
You might be sending encrypted noise over the wire, but the things like error correction codes are not encrypted. It might be white noise, but you've got to make sure it's the correct white noise when it arrives at its intended destination.
> Then, we people are very soon capable of communicating using quantum entanglement
How many years from now do you think it'll be before we simply stop using radio waves entirely?
This is nothing other than sci-fi. I don't understand how you can be so sure of something like this.
I guess you haven’t heard of the military monitoring the activity even of encrypted enemy channels. You don’t even need to know how to decrypt it, you can detect peaks in communication.
How much do you wanna bet? Do you have a specific bitrate and year in mind?