Zan Boag: As a space scientist, you’ve been gazing deeply into space. You’ve been living and breathing the idea of ‘space’. The universe has been your playground. What is space? How far does it extend? Is it limitless?
Günther Hasinger: It is a little bit like the overview effect that the astronauts get when they leave the Earth and then they see the Earth as a small blue dot in a big surrounding universe. But as an astrophysicist, a space scientist, I actually have a perspective which is even larger. So, basically, our whole solar system is just one out of many. Our whole galaxy is one out of many, and so in principle you could imagine that space, as such, is infinite. It is very likely not infinite, but it is bigger than anything we can imagine. And the point is that there is a horizon. When you ask what is at the end of the universe or the end of space, it turns out that the end of space as we see it is only an optical illusion. Space goes much further, beyond where we would ever be able to see.
And you can imagine this, like when you stand on the coast and you look at the horizon, you think that the Earth is finished there, right at the horizon, but you know very well that when you see ships coming up, they come from beyond the horizon. And when you go to the horizon you see another horizon, and another one. The same is true for our universe. So, what we see as the boundary of space right now with the Microwave Background glow, is only a horizon. And if we would be able to fly there, we would see billions of more times the same universe.
In principle, if you take our whole Earth and you put a needle down, the tip of the needle is roughly what we see from our current universe and there is so much more universe out there which we cannot see.The reason we cannot see it is because the lifetime of the universe is finite, and therefore light did not have enough time to travel to us from those distant regions. It’s not that there is an end to this, it is basically just that we don’t have any information because light doesn’t reach us from there.
For a better understanding, one first would have to guide people through the huge dimensions. For instance, the time the light takes to travel to us. The light from the Sun takes eight minutes to travel to us. From the outer solar system – Jupiter, Saturn – it takes hours to get to us. From the next star, it takes four years to come to us. And then from the centre of the galaxy, it takes 30,000 years to reach us.The next galaxy is about 170,000 light-years away and the next big galaxy a million light-years.
And so, you work out into space by the time the light needs to travel to us, and at some distance you reach the point where the light that travels to us needs longer to get to us than the age of the universe, and therefore the light has never reached us.
There’s an article on the ESA website with the headline, ‘Galactic crash may have
