See what "close to each other" is in other dictionaries. How close can two alien civilizations be to each other? What is human blood pressure? What is it like

Population I: stars like the Sun, 1-2% composed of elements heavier than hydrogen and helium. This material is well processed and creates a mixture of gas giants and solid planets in solar systems that can support life.
Population II: These are mostly old stars. Their content of heavy elements can be 0.001-0.1% of the sun, and the worlds around them are mostly diffuse, gaseous. There may be too few heavy elements for life, and they will be primitive.
Population III: the first stars in the Universe that were completely free from heavy elements. We have not yet found such, but theoretically they exist (and existed).

If you look at the first galaxies, they are full of Population II stars. But in our vicinity, we see a mixture of young and old, metal-rich and metal-poor stars.

One of the most important lessons learned from the Kepler mission was the Kepler-444 system. It is a Population I star (with planets around), but much, much older than earth... Our world is 4.5 billion years old, and Kepler-444 is 11.2 billion, which implies that the universe could have formed an Earth-like world a long time ago, 7 billion years before Earth formed. Given this possibility, as well as the fact that there are more metal-rich luminaries in the center of our galaxy than in the regions, it may well be that somewhere in the Universe (and maybe even in the Milky Way) there is a system with intelligent life.

So, given everything we know about where suitable stars could be, how close could two alien civilizations be? Where to find them? Under what circumstances? Let's take a look at five of the most likely options picked up by Ethan Siegel.

This is just a dream. In the early days Solar system it is likely that Venus, Earth, and Mars (and perhaps even Theia, the hypothetical planet that collided with the Earth and formed the Moon) were all in favorable conditions for life. They had a crust and atmosphere full of ingredients for life, and they also once had liquid water on the surface. Venus and Mars, on their closest approach, are 38 million and 54 million kilometers from Earth, respectively. But in red dwarf systems (M-class), the planets are separated by significantly smaller distances: about 1 million kilometers between potentially inhabited worlds in the TRAPPIST-1 system, for example. Moons near giant worlds may be even closer. If life develops successfully under certain conditions, why not repeat it twice in the same place?

Within a globular cluster

Globular clusters are massive collections of hundreds of thousands of stars enclosed in a sphere several tens of light years in radius. In the outer regions, the spheres of the stars are separated by light years, but in the inner, densest clusters, the distance between the stars can be as much as from the Sun to the Kuiper belt. The orbits of planets in such stellar systems must be stable even in dense conditions, and given what we know about globular clusters that are less than 11.2 billion years old, like Kepler-444, there could be many candidates for life. Several astronomical units are a surprisingly small distance between two civilizations, isn't it?

Near the galactic center

The closer you get to the center of the galaxy, the denser the stars become. Within the central few light years, the density of stars is extremely high, even when compared to the cores of globular clusters. In a sense, the galactic center is extremely dense because it contains black holes, huge clusters of masses and star formations that are not found in globular clusters. But the problem with the stars we see in the center of the Milky Way is that they are too young. Perhaps due to the region's instability, stars rarely live even a billion years. Despite the increased density, such stars are unlikely to acquire advanced civilizations. They just don't live.

In a dense cluster of stars or a spiral arm

What about star clusters that form in the galactic plane? The arms of a spiral galaxy are denser than other regions and are where new stars tend to appear. Star clusters that remain from those eras often contain thousands of stars located in a region only a few light years away. But again, stars don't stay in such conditions for long. A typical open cluster of stars disintegrates after a few hundred million years, and only a few live for billions of years. The stars move along the spiral arms constantly, including our Sun. And while the stars in the arm can converge up to 0.1 light years, they are unlikely to be good candidates for life.

Interstellar distribution

So we're back to what we're seeing in our own area: distances of several light years. As you get closer to the center of the galaxy, you can reduce this distance to what you saw in an open cluster: 0.1-1 light years. But if you get even closer, there will be a problem that we observed too close to the center of the galaxy: mergers, interactions and other catastrophes that destroy a stable environment. You can get closer, but usually interstellar space does not allow this. In the best case, you can wait until another star passes by, and this happens every few million years.

In general, while we do not expect intelligent alien life to be as ubiquitous and ubiquitous as planets and stars, every such world that meets the right conditions is very rare. And every time you get that chance, success is unlikely. The number of possibilities that can become reality is very limited. But now we at least know what to expect if we find a bunch of other advanced civilizations in the Universe.

It takes only 45 minutes to discuss these issues, but after this time people usually become much closer to each other - this is shown by research in social psychology. You can try answering them with your partner or just a friend, relative, to get closer and strengthen your relationship.

Each of you should take turns answering these questions:

1. If you could choose anyone in the world, who would you invite to dinner?

2. Would you like to be famous? In what area?

3. Before you call, do you practice what you are going to say? Why?

4. What does a perfect day mean to you?

5. When was the last time you sang with yourself? And to someone else?

6. If you could live to be 90 years old, but for the last 60 years you can keep either the body or the mind of a 30-year-old, which would you choose?

7. Do you have a premonition of how you are going to die?

8. Name three things that you and I have in common.

9. What are you most grateful for in your life?

10. If you could change anything about the way you were raised, what would it be?

11. Try to tell the story of your life in 4 minutes in great detail.

12. If you could wake up tomorrow with a new ability, what would it be?

13. If a magic ball could tell you the truth about you, your life, the future or anything else, what would you like to know?

14. Is there something that you've dreamed of doing for a long time? Why haven't you done it yet?

15. What is the greatest achievement of your life?

16. What do you value most in friendship?

17. What is your most precious memory?

18. What is your worst memory?

19. If you knew that you would die in a year, what would you change in your life? Why?

20. What does friendship mean to you?

21. What role does love play in your life?

22. Highlight my main good characteristic. Now name 5 of my merits.

23. How warm is the relationship in your family? Do you consider your childhood happier than others?

24. What do you think about your relationship with your mother?

25. Come up with three statements with the word "we". For example, "We both feel that ...".

26. Finish the sentence: "I wish I had a person with whom I could ...".

27. If you want to become a close friend with a person, what should he know about you?

28. Tell me what you like about me: be honest, say what you will not tell the first person you meet.

29. Tell me the most embarrassing or embarrassing moment in your life.

30. When was the last time you cried in front of another person? And alone with yourself?

31. Say that you already love in me.

32. What is too serious for you that you cannot joke about?

33. If you knew that you would die today, but could not talk to anyone, what untold words would you regret? Why haven't you said that yet?

34. Your house, in which everything you have is on fire. After saving loved ones and animals, you have the opportunity to save one more thing. What was that? Why?

35. The death of which of your relatives would be the most painful for you? Why?

And more options:

If you could choose the gender and appearance of the unborn child, would you do it?
Would you agree to see nightmares for a whole year for a reward of enormous wealth?
When traveling to another city, your partner spends the night with a stranger. Knowing that they will never meet again, and that you will never find out about it in any other way, would you like your partner to tell you about it?

It only takes 45 minutes to discuss these issues, but after this time people usually become much closer to each other.