<p>Some basics:</p>

<p>Whether we listen for or send signals into space, something to keep in mind is that space is full of EM radiation of all wavelengths, from very long wavelength background radiation, to a range of microwave, infrared, visible and UV light from stars to gamma-rays from accretion disks and collapsing stars.   Any signals we send and perhaps any signals we could receive would be like raindrops in an ocean.   There's an obvious range to listen called <a href="http://www.setileague.org/askdr/hydrogen.htm" rel="nofollow noreferrer">the hydrogen line</a>, which is the emptiest region of EM radiation in space.</p>

<p>Even so, across light years, signals would still be faint, so the first signal that's sent needs to be an easily recognizable signal and math is very good for that.   Pi in binary or a series of repeating prime numbers wouldn't happen naturally, so signals like that are a great way of saying "We are here".</p>

<p>Once the first signals of prime numbers or other math are exchanged, and we see what direction the signal comes from and we know where to listen and where to send, then the communication can begin, presumably using more traditional language.  </p>

CC BY-SA 3.0
2018-02-14T08:49:27.283Z
2018-02-14T08:49:27.283Z
userLTK
<p>The general plan is to start very simply and build up - would you recognise the following?</p>

<p>.  .. ... .... .....</p>

<p>Numbers, right? You'd probably want to save typing out lots of dots in the long run, so you'd want to convert it to a "base-something" system, e.g.</p>

<p>0001 0010 0011 0100 0101</p>

<p>In conjunction with the original, it should be obvious that this is binary (the Aricebo message, if I remember correctly, used a form of base 10).</p>

<p>Then you can start describing sequences of numbers that you think the aliens should understand - primes, Pi, or as Aricebo did, the atomic numbers of H, O, C, N...the elements that primarily form life on Earth. </p>

<p>As long as the aliens have a concept of numbers, and a vaguely similar idea of mathematical logic to us, you can build up to most mathematical ideas in one way or another. Integrals, for example, could be done by sending a sequence corresponding to y=x^2, then defining two points in particular, and providing the resultant integration result. A civilization capable of picking up our signals <em>should</em> (I make no assumptions about aliens!) recognise the concept.</p>

CC BY-SA 3.0
2018-02-14T14:50:07.233Z
2018-02-14T14:50:07.233Z
The Geoff
<p>Always I wonder about that if some day alien wants to talk to us, then how can we talk to them? They didn't know any of the language on the Earth.</p>

<p>What will be the basic building blocks for it?</p>

CC BY-SA 3.0
2018-02-14T20:12:32.533Z
"God made the integers, all else is the work of man" so we can only be sure that they know the integers.  https://en.m.wikipedia.org/wiki/Leopold_Kronecker
badjohn
CC BY-SA 3.0
2018-02-14T08:12:09.460Z
There might be a good question here, but as phrased it is too speculative. It is unclear what you mean by "talk through maths", or why you ask about "integrals". Of course we know nothing about mathematical systems used by undiscovered intelligences.
James K
CC BY-SA 3.0
2018-02-14T08:20:19.230Z
It certainly worked in 1952! ;-) https://scifi.stackexchange.com/a/16368/51174 (in Hollywood at least)
uhoh
CC BY-SA 3.0
2018-02-14T08:27:44.423Z
This is an interesting question nonetheless. [Poincaré](https://en.wikipedia.org/wiki/Henri_Poincar%C3%A9) and [Wigner](https://en.wikipedia.org/wiki/Eugene_Wigner) might differ on how universal math might be, or if a very different civilization may use mathematics so different as it might be mutually unrecognizable vis-a-vis Earth's maths. Watch [Is math discovered or invented? - Jeff Dekofsky](https://youtu.be/X_xR5Kes4Rs)
uhoh
CC BY-SA 3.0
2018-02-14T08:30:06.320Z
The gold plates put on board Voyagers are there to get an idea of what might work.  At least if " to talk" is intended as "to communicate".
Alchimista
CC BY-SA 3.0
2018-02-14T08:41:04.983Z
[Weinberg's thoughts](https://www.youtube.com/watch?v=NpMk9G-ddiM) and [Wolfram's](https://www.youtube.com/watch?v=nUCwtLTUPQ4) (two Sevens, err... Stevens)
uhoh
CC BY-SA 3.0
2018-02-14T08:47:20.393Z
@james k then what we will do to talk to them
user9306517
CC BY-SA 3.0
2018-02-14T08:57:32.503Z
@user9306517 just after `22:00` https://youtu.be/4OXYLCVUaCc?t=1320
uhoh
CC BY-SA 3.0
2018-02-14T09:09:30.377Z
@user9306517 I don't know. Nobody knows. That is what makes this question speculative. I think it can be [edit]ed to make less speculative and clearer. Please edit, if you can.
James K
<universe><astrophysics><fundamental-astronomy><mathematics>
What happens if one day aliens want to talk to us. How can we talk to them?
user9306517
# What happens if one day aliens want to talk to us. How can we talk to them?

(Asked by: username_0 on 2018-02-14)

Always I wonder about that if some day alien wants to talk to us, then how can we talk to them? They didn't know any of the language on the Earth.

What will be the basic building blocks for it?

**Tags:** universe, astrophysics, fundamental-astronomy, mathematics

> **Comments:**
> **username_2**: There might be a good question here, but as phrased it is too speculative. It is unclear what you mean by "talk through maths", or why you ask about "integrals". Of course we know nothing about mathematical systems used by undiscovered intelligences.  
> **username_3**: It certainly worked in 1952! ;-) https://scifi.stackexchange.com/a/16368/51174 (in Hollywood at least)  
> **username_3**: This is an interesting question nonetheless. [Poincaré](https://en.wikipedia.org/wiki/Henri_Poincar%C3%A9) and [Wigner](https://en.wikipedia.org/wiki/Eugene_Wigner) might differ on how universal math might be, or if a very different civilization may use mathematics so different as it might be mutually unrecognizable vis-a-vis Earth's maths. Watch [Is math discovered or invented? - Jeff Dekofsky](https://youtu.be/X_xR5Kes4Rs)  
> **username_4**: The gold plates put on board Voyagers are there to get an idea of what might work.  At least if " to talk" is intended as "to communicate".  
> **username_3**: [Weinberg's thoughts](https://www.youtube.com/watch?v=NpMk9G-ddiM) and [Wolfram's](https://www.youtube.com/watch?v=nUCwtLTUPQ4) (two Sevens, err... Stevens)  
> **username_0**: @james k then what we will do to talk to them  
> **username_3**: @username_0 just after `22:00` https://youtu.be/4OXYLCVUaCc?t=1320  
> **username_2**: @username_0 I don't know. Nobody knows. That is what makes this question speculative. I think it can be [edit]ed to make less speculative and clearer. Please edit, if you can.  
> **username_1**: "God made the integers, all else is the work of man" so we can only be sure that they know the integers.  https://en.m.wikipedia.org/wiki/Leopold_Kronecker  

---

## 2 answers

### Answer by username_5 on 2018-02-14. Score: 2

Some basics:

Whether we listen for or send signals into space, something to keep in mind is that space is full of EM radiation of all wavelengths, from very long wavelength background radiation, to a range of microwave, infrared, visible and UV light from stars to gamma-rays from accretion disks and collapsing stars. Any signals we send and perhaps any signals we could receive would be like raindrops in an ocean. There's an obvious range to listen called [the hydrogen line](http://www.setileague.org/askdr/hydrogen.htm), which is the emptiest region of EM radiation in space.

Even so, across light years, signals would still be faint, so the first signal that's sent needs to be an easily recognizable signal and math is very good for that. Pi in binary or a series of repeating prime numbers wouldn't happen naturally, so signals like that are a great way of saying "We are here".

Once the first signals of prime numbers or other math are exchanged, and we see what direction the signal comes from and we know where to listen and where to send, then the communication can begin, presumably using more traditional language.


---

### Answer by username_6 on 2018-02-14. Score: 1

The general plan is to start very simply and build up - would you recognise the following?

. .. ... .... .....

Numbers, right? You'd probably want to save typing out lots of dots in the long run, so you'd want to convert it to a "base-something" system, e.g.

0001 0010 0011 0100 0101

In conjunction with the original, it should be obvious that this is binary (the Aricebo message, if I remember correctly, used a form of base 10).

Then you can start describing sequences of numbers that you think the aliens should understand - primes, Pi, or as Aricebo did, the atomic numbers of H, O, C, N...the elements that primarily form life on Earth.

As long as the aliens have a concept of numbers, and a vaguely similar idea of mathematical logic to us, you can build up to most mathematical ideas in one way or another. Integrals, for example, could be done by sending a sequence corresponding to y=x^2, then defining two points in particular, and providing the resultant integration result. A civilization capable of picking up our signals *should* (I make no assumptions about aliens!) recognise the concept.


---

