Today, for the 2nd part of Exploring the Universe, Andy and Ammar explained the boundaries of human travel in space. The first thing that was discussed was the limits of the interactable space where they talked about the universe after the Big Bang. Just after the Bigbang happened, the young universe was just a tiny bubble of energy that wasn’t uniform; some parts of the bubble were denser than other parts. When a process called cosmic inflation happened, the universe started to expand with the bubble of energy started to expand quickly too, this happened so fast that all those tiny differences in density were stretched from subatomic distances into galactic distances. After that short but powerful inflation ended, gravity began trying to pull everything back together: in the part where it was denser, the gravities were strong and made a group of galaxies, like the “Local Group” we live in today. However, outside of the pocket of the gravitationally bonded local group, the expansion of the universe was never stopping - it is getting faster and faster and this expansion shows that there is a cosmological horizon around us, which 94% of the galaxies we can see today have already passed it and are lost to us forever. Everything beyond it is travelling faster, relative to us, than the speed of light, and everything that passes the horizon is out of reach forever and we will never be able to interact with it again. However, if we can’t interact with them, how come we can still see them? Well, the way we are able to see something is via light (every second the light reaches us, they are actually from trillions of galaxies that have passed the horizon because they used to be closer to us when they emitted the light). So the observable universe is much larger than the universe we can actually interact with. This then led to a question from part 1: “Do you believe there will be other creatures or Civilisations like our humanity in the observable universe?”. We concluded, even though there might be other creatures/civilisations out there, it is impossible for us to reach out to them as they are not in our local galactic group.

Apart from the intriguing question, we have also covered Fermi Paradox: The Great Filter, which is a simple theory that states that when a civilisation is needed to be made, it has pass-through lots of filters, for example, natural disasters, climate change, etc - which destroys all kinds of living creatures, hence, at the very end, there might be a filter that destroys everything, including us - humans; it's said that the earth is still in the process of passing a filter so we might also reach the end at a point. The solution for this issue was to colonise our own universe that was habitable for humans. For this, firstly, we had to figure out about space travelling, thus we moved on to the topic of space tourism, which brought up a question: “With the current technology, how could the average humans like us go into space?”. Currently, on Earth, there are two types of space tourism: Suborbital Space Tourism and Orbital Space Tourism. Suborbital Space Tourism is a spaceflight in which the spacecraft reaches outer space, but its path intersects the surface of the Earth so that it will not complete one orbital revolution, whereas Orbital Space Tourism is a spaceflight in which the spacecraft reaches outer space and will be able to complete one orbital revolution around the Earth. How exactly will space travelling help? we may wonder. Travelling to space requires enormous amounts of energy, however, if we are able to find a solution in which we can harvest all the energy resources in the solar system to ourselves with the new, advanced technologies, we will be able to build much more energy-efficient space crafts to explore outer space further.

Next up, we have the third chapter: The Theoretical Solution To Travel. This could solve the problem of travelling outside the earth but also give theories on how we could explore and colonise our entire solar system. One solution we covered is a theory called the “Dyson Sphere”, a megastructure that surrounds a whole star to capture its power output and basically give humanity unlimited energy. With the amount of energy around the solar system, we could create the infrastructure for all sorts of projects, including having colonies on other worlds and even travelling to other stars - this would be the start of an interstellar civilization and could be our first step to intergalactic colonisation! We also further looked into terraforming planets with that unlimited amount of energy; this means manipulating planets' atmosphere and other environmental characteristics so that the climate of that planet can become habitable for the lifeforms. This is tried to be done on Mars, however, there are quite some challenges: Mars has a very thin atmosphere, an average temperature of -63°C and air pressure of less than 1%. Only if we address all of these conditions first, we would be able to proceed with the others, like how to grow food, etc. So how could we address these challenges? One way that we talked about was using the Dyson sphere again, along with giant mirrors to make the atmosphere of Mars hotter, or we could also release greenhouse gases from the planet's surface such as carbon dioxide (CO2) to trap heat, warm the climate and ultimately increase the atmospheric pressure. There probably are many other ways we could do this, but we just have not found them out. Towards the very end of our session, we had several questions like 'What if the huge amount of energy we harnessed from the Dyson Sphere would lead to our destruction rather than for our benefit?' and 'Would we really have enough materials to build the Dyson Sphere? How will we actually build it?' Since the Dyson Sphere doesn't exist and is still a theory, it wasn't possible for us to give out solid answers but we used our creativity to answer them. Overall, theories and assumptions are always part of astronomy and this session left us questioning about what will everything look like in the future and how much will we really be able to achieve - a very intriguing session!