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Are there aliens?

It's one of the biggest questions in astronomy - are there aliens? Watch this video to find out.
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Are there aliens? We haven’t found any yet. So why not, and could they be out there? To find alien life, we have to look away from the Earth. Astronomers have discovered many planets that orbit the twinkling stars you can see in the sky. Do any of these planets harbour life? We think liquid water and oxygen are key drivers for the continuing development of life on a planet. There isn’t a fast recipe for life, as far as we know. The first cells on Earth developed a whopping one billion years after our solar system formed. It took another 200 million years before cyanobacteria developed, giving Earth a burst of oxygen that was initially catastrophic.
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The rising oxygen levels dramatically reduced the amount of methane gas in the atmosphere, leading to a big freeze. Despite this, over the next billion years complex life flourished. Life can be found in the most extreme places here on Earth– from microbes surviving deep beneath ocean floors, to tiny water bears that could survive the intense radiation and vacuum of space. So, in theory, life could exist on some of the other inhospitable worlds out there, but how would we detect its presence? Imagine that there were aliens on a planet orbiting a distant star looking for us. The hypothetical aliens on Gliese 581c would see periodic dips in the Sun’s light as Earth and other planets passed in front.
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They would see that three planets, Venus, Earth, and Mars, fall into what we humans call the Goldilocks zone, a region around a star where liquid water could exist. To find out if one of these planets has life, the Gliesians need to study their atmospheres. They would look for the fingerprints of different gases in the light from these planets and send a spacecraft out to investigate us. However, if their technology is similar to ours, their probe would take over 400,000 years to reach us. They could also send us a strong radio signal hoping that someone would reply once the signal arrives at Earth, 20 years later.
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On the cosmic calendar, where one year is 13.8 billion years– the age of the universe– modern humans have only been around for eight seconds. During the cosmic calendar year, and across the whole universe, many civilizations may already have come and gone long before we developed the technology to look for them. Although imagining aliens to be sophisticated and intelligent like us is exciting, we have yet to find simple life, like extraterrestrial microbes, and we may have a better chance of finding alien life in our own cosmic backyard. Some of the many moons around Jupiter and Saturn are composed of ice sheets covering vast amounts of liquid water underneath.
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Perhaps a future mission can explore the subsurface oceans of these moons, and who knows what bizarre and beautiful alien life they may discover there.

We have seen how astronomy can be used to teach topics in physics, but it can also be used to teach topics in other sciences. Consider the question ‘Are there aliens?’ It’s a big question and one that relies on the multiple disciplines of science to answer.

  • Physically – how might we find them?
  • Biologically, what does life need to form and thrive?
  • Chemically – what kind of environment and conditions would be conducive to life?

Watch the video ‘Are there aliens?’ Then share any curriculum-science topics (physics, biology and chemistry) that you think could be taught using the context of aliens.

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Physics, Astronomy, and Space: Teaching Secondary Science

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