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The Big Idea - Why don’t we see aliens in the sky?




Space is Vast Space is unbelievably vast 😲. It is so large that humans can’t really understand how large it is. This video might help: https://www.youtube.com/watch?v=WYQ3O8U6SMY. The universe is VAST! So, why does that mean we probably won’t see any aliens zooming around up above? Well, it’s all about light years. Light is the fastest thing in the universe, travelling at approximately 299,792 kilometres per second. It’s so fast that it can circle around the Earth 7.5 times in a single second 🌍⚡. Now, imagine you are travelling in a spaceship as fast as the speed of light (a feat beyond our current technological capabilities). You decide to venture far into space to the next nearest star system where scientists believe there's a tiny chance of alien life - Proxima Centauri 🌟. It’ll take 4.2 light years to get there, which means you’ll need to embark on a journey at the speed of light for over 4 years. Consider this: you will need to survive in your ship for 1533 days at full speed and take enough supplies for the journey, but you’re unsure if there will be food upon arrival 🍽️🚀. Thus, you need enough to go there, enough to explore while you’re there, and enough for the return leg. That’s 3066 days in travel time alone! Extraterrestrial beings would face the same rigamarole visiting us.



Time Humans have been present for less than 1% of Earth’s history 🌍. We have only had the technology to explore space for the past sixty years or so, which is a minuscule fraction of Earth's 4.5 billion-year history ⏳. As of … NOW, humans can travel to space but have not mastered light-speed travel 🛸. The possibility of encountering aliens 👽, or vice versa, hinges on both civilisations reaching a sufficiently advanced technological level within the same narrow window of cosmic time ⌛. Given the universe's vast age—approximately 13.8 billion years—finding a civilisation in the same stage of development is exceedingly unlikely 🌌. They could arrive a billion years too early or too late 🕰️. We might venture to their planet only to find we are billions of years off mark 🚀🌏. This temporal mismatch adds another layer of complexity to the already daunting task of discovering extraterrestrial intelligent life 🤔💫.


Probability

Probability is about how likely something is to happen 🎲. What’s the probability of meeting aliens as intelligent as humans - incredibly small 🔍. The only living things on Earth 🌍 that even think about aliens are humans 👥. So, any aliens out there will probably be a little slug 🐌 slimily sliding silently along the ground! Nevertheless, SETI (Search for Extraterrestrial Intelligence) is ploughing ahead with the search 🔭. If you consider our own Milky Way Galaxy 🌌, the chances of alien life existing are almost inevitable 🚀. Scientists estimate the number of stars in our galaxy alone to be between 100-400 billion in number ✨. Let me write the smallest of those numbers. 100,000,000,000 🤯. If every star is like our own and has 8 planets orbiting 🪐, we have 800,000,000,000 planets. In our own solar system, Earth has life 🌱, Mars has water 💧, and some huge moons have the same. If you searched through 800,000,000,000 planets, the chances seem high that you’d come across a couple of living lifeforms 🌳🐾. Factor in that the observable universe may have something like 2 trillion galaxies 🌠 and we have this number of potential planets. That spits out the very groovy number - 1,600,000,000,000,000,000,000,000 🌀 of potential planets. Do you suppose we’re the only planet with life? I wonder… 🤔💫.

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