We’ll never be able to reach 99.99999999999% of the Universe

Our planet and solar system belong to Milky Way galaxy, which is 100,000 light years across with a supermassive black hole in the center. Average distance between stars is 5 light years (29 trillion miles) approximately.

Imagine that the distance from the earth to the sun (93 mln miles, or about 8 light minutes) is compressed to the thickness of a typical sheet of paper. On this scale, the average distance between stars is 82 feet and the diameter of the Milky Way is 310 mile high stack of paper.

If we send a space ship today (at the record speed of 24,791 mph), to reach the nearest star (4.3 light years away), it would take 117,000 of years.

To cross our galaxy Milky Way, it would take us today 2,722 mln of years.

Well, our technologists talk about bringing speed of our space ships to 10% of the speed of light, that is 68 mln mph. None of the proposed concepts is ready to be developed for the coming few decades at acceptable cost. Yet, if that is possible, we would be able to reach the nearest star in 43 years, which sounds much better than 117,000 years. Unfortunately, even with such a speed, to cross Milky Way will require 1 mln years. Milky Way is huge, isn’t it?

The next in size structure is called Local Group. It consists of some 54 galaxies including our Milky Way. The nearest to us galaxy is called Andromeda (at 2 million light years, it is one of the most distant objects visible to the naked eye). It is 20 times further from us than the diameter of Milky Way. Which means that at 10% of the speed of light, we can get to it in 20 mln years.

Local Group of galaxies is 10 mln light years across (will require 100 mln years to cross at 10% of the speed of light).

The next in size structure is Laniakea Supercluster. It is 520 mln light years across and consists of 100 thousand galaxies like our Milky Way.

Millions of such superclusters compose the observable universe.

On the image below, you see a simulated view of the entire observable universe, approximately 93 billion light years in diameter.

The scale is such that the fine grains represent collections of large numbers of superclusters. At the center is the supercluster where we belong to, but it is too small to be seen in the image.

That is it! We cannot see anything bigger than the observable universe. By the way, it expands with acceleration all the time. Which means that in the nature exists not only attracting force (gravitation), but also repelling force (dark energy, which is called “dark” just because we cannot detect it and assume its presence theoretically).

Now, our Local Group is only 0.00000000001% of the observable universe, and that is all we can access ever, on principle. Why? Because only Local Group is gravitationally bound. The other groups are moving away from us at speed we cannot ever hope to reach.

So, we can never access anything outside our Local Group. Other groups will fly away farther and farther, until they will become undetectable for us. That is when the skies beyond our Local Group will become black forever.

In 4 billion years, our Local Group (which is gravitationally bound!) will merge into one big galaxy called Milkodromeda (Milky Way+Andromeda), and that is the only structure that will be present and accessible to our descendants.

Which means that right now we have the unique opportunity to study our past (because light of the farthest sources still reaches us) and see the whole universe. We will do it and preserve the knowledge, so our descendants will know what is “out there” although they themselves will not be able to see it.

It is reported that Copernicus’ parents
said to him at the age of twelve:
“Copernicus, young man,
when are you going to come to terms
with the fact that the world
does not revolve around you.”