A planet can be habitable if it is within the habitable zone of a star, orbit a stable star, has sufficient mass, rotates and has an atmosphere. The distance from a star its habitable zone is from depends on the star's temperature. The shell-shaped region of space around the star is the habitable star. If a planet is within the habitable zone, the planet should maintain liquid water. Liquid water is one of the factors to determine if a planet is habitable. The star's luminosity increase over time should not be too severe. If it were to be too severe, everything on its nearest planet would burn up.
A planet should rotate on its axis and revolve around its parent star. For life to have a chance to evolve, other conditions have to be met in its rotational motion. For example, the planet's axial tilt should be close to perpendicular to its plane of orbit.
A planet must be made up of rocks, not gases, to also be habitable. It should also have sufficient mass to retain an atmosphere. However, life forms may somehow live on the cloud tops of gas planets.
The presence of an atmosphere is necessary as it blocks most of the harmful radiation and cosmic rays, protecting the planet's surface. It keeps the planet warm and allows for liquid water and prevents the water from boiling away due to low pressure compared to the water.
Examples of habitable planets include Proxima b, Wolf 1061c, Gliese 832c and Trappist-1d.
Proxima b orbits Alpha Centauri, the nearest star to the Sun. It may be covered with a liquid ocean up to 200km deep and orbits within its habitable zone. It has a mass of 1.3 times the Earth's and has an atmosphere similar to Earth's.
The Dark Forest theory was derived from a novel called "The Dark Forest". It was published in 2008. It provides an explanation for why we haven't seen or encountered aliens yet. It suggests that if we were to meet aliens, it would be our doom. Aliens might be purposefully hiding from us and might already be present in our universe. This opens up two possibilities: we are more advanced than us and fear us, or they are waiting for the moment to annihilate us.
The Drake Equation allows us to estimate there are at least 20 civilizations in our cosmic neighbourhood. However, we have not seen any other life forms yet. This links up with the Dark Forest theory: aliens don't want to be found.
At the end of the lesson, we played a kahoot game. I got first place! I feel happy as this session was interesting and I got the key concepts right. We also learnt about the many times people thought aliens were trying to contact us, and how potentially habitable planets may not be so habitable - planets orbiting a red dwarf in its habitable zone would be tidally locked to its host star: one side of the planet permanently faces the star, heating up that part of the surface and causing it to remain uninhabitable. We also did research on potentially habitable planets and realised how some of them may not be so easily habitable. I wished that this lesson had a slightly longer kahoot game to increase the suspense and slides on some conspiracies.
A planet should rotate on its axis and revolve around its parent star. For life to have a chance to evolve, other conditions have to be met in its rotational motion. For example, the planet's axial tilt should be close to perpendicular to its plane of orbit.
A planet must be made up of rocks, not gases, to also be habitable. It should also have sufficient mass to retain an atmosphere. However, life forms may somehow live on the cloud tops of gas planets.
The presence of an atmosphere is necessary as it blocks most of the harmful radiation and cosmic rays, protecting the planet's surface. It keeps the planet warm and allows for liquid water and prevents the water from boiling away due to low pressure compared to the water.
Examples of habitable planets include Proxima b, Wolf 1061c, Gliese 832c and Trappist-1d.
Proxima b orbits Alpha Centauri, the nearest star to the Sun. It may be covered with a liquid ocean up to 200km deep and orbits within its habitable zone. It has a mass of 1.3 times the Earth's and has an atmosphere similar to Earth's.
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| Artist's impression of Proxima b. Credits to ESO. Licensed under CC BY 4.0 International. Original image is here. |
R x ƒp x ne x ƒ1 x ƒc x L = N
N = number of civilizations in our galaxy which communication may be possible
Enrico Fermi came up with the Fermi Paradox, which aims to answer the question of where the aliens are. He used it to make the question on extraterrestrial life. The Drake equation identifies specific factors which play a role in the development of civilizations. It is generally accepted by the scientific community.The Drake Equation allows us to estimate there are at least 20 civilizations in our cosmic neighbourhood. However, we have not seen any other life forms yet. This links up with the Dark Forest theory: aliens don't want to be found.
So-called "evidence" of alien life
Martian "fossils" were discovered in meteorite ALH84001 from Antartica in 1996. In 2001, the red tinge of Jupiter's moon Europa was proposed to be due to frozen bits of bacteria, explaining the mysterious infrared signal it gave off. In 2004, a mysterious radio signal was received by SETI on 3 occasions, from the same region in space.
At the end of the lesson, we played a kahoot game. I got first place! I feel happy as this session was interesting and I got the key concepts right. We also learnt about the many times people thought aliens were trying to contact us, and how potentially habitable planets may not be so habitable - planets orbiting a red dwarf in its habitable zone would be tidally locked to its host star: one side of the planet permanently faces the star, heating up that part of the surface and causing it to remain uninhabitable. We also did research on potentially habitable planets and realised how some of them may not be so easily habitable. I wished that this lesson had a slightly longer kahoot game to increase the suspense and slides on some conspiracies.
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