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Astronomy and Sustainability - Questions from young children

Writer's picture: Suresh RandadathSuresh Randadath

Updated: Oct 29, 2024




These are questions received from children of Grade 6 during a session on Astronomy and Sustainability that was delivered to a school in Bengaluru, and answers to them.


  1. How did the Moon get tidally locked?

    It's tough to explain without an illustration. Earth's gravity pulls the Moon in one direction making it slightly ovel in shape. If the Moon tries to rotate on its axis, the ovel shape will get misaligned with the major axis of the Moon. In that instance, Earth will try to pull the Moon so that the ovel shape is aligned with the major axis. In the illustration below the bigger sphere is Earth and smaller is the Moon. If Moon tries to spin on its axis, Earth will try to bring the oval shaped Moon back to the original position by pulling on its major axis. This tussle goes on forever. This is the reason.

  2. Why the Moon has an oval shape?

    Due to the gravitational pull of the Earth. The oval shape is not very visible, though in the above illustration it is exaggerated for easy understanding.

  3. Why Mars and Venus could not sustain life?

    Mars lost all its atmosphere most likely due to the loss of magnetic field strength. As a result it did not have enough shield to protect it from the radiation from the Sun. This resulted in all the water getting evaporated into space. Mars would have lost its magnetic field, because it cooled down too quickly, unlike Earth which is still hot inside. Venus is an example of runaway greenhouse effect that made the planet extremely hot, preventing life to form. The thick clouds, permanently enveloping the planet completely, is creating this greenhouse effect.

  4. Will over consumption reduce if the population is reduced?

    It is not the size of the population that is an issue, it is the life style of the people that is the problem. We need to follow a lifestyle based on reduce-reuse-recycle principle, rather than use-and-throw. We need to follow a minimalistic life style. For example, do you really want to buy a new car every 3 to 5 years? A car is capable of running for 15 years. Another example: why buying cloth regularly, when a cloth can last for many years? Remember, garment industry is the third largest polluter and amount of plastic in the garment is quite high these days, making the cloths non-biodegradable.

  5. If there is so much garbage then how is the Earth still blue?

    The blue colour is from the oceans that is covering 2/3 of the planet. The ocean water reflects blue rays in the sunlight more making the water look blue. Though there is garbage in the oceans and it is growing, it is not large enough to cover the entire oceans, yet. Hence Earth still looks blue.

  6. How did humans survive after 5 mass extinctions?

    The 5 mass extinctions I mentioned in the session were before humans evolved. The 5th one was the extinction of Dinosaurs 75 million years ago. The 6th mass extinction is started, and unless humans don't stop global warming, it is likely to wipe us out.

  7. Don't other materials have a high carbon footprint?

    It is not the material as such that is leaving a carbon footprint, but the production of that material and/or the use of that material. Any goods manufactured and shipped uses energy. If it is not using clean energy like solar or wind, then there is a carbon footprint. Similarly food imported from faraway places leave a big carbon footprint due to the transportation, refrigeration (of meat and dairy products), etc.

  8. Doesn't Kauveri sustain Bangalore?

    Kauveri did not have enough water last summer to supply water to so many people. Unless we improve the groundwater levels, we will not have water if Kauveri runs dry in one summer. Our forefathers were very intelligent to understand the geography of Bangalore and build thousands of interconnected lakes to tap the rainwater. But unplanned growth resulted in many of these lakes encroached by buildings. The Rajakalves (channels) that used to connect these lakes also vanished due to unplanned development.

  9. How was galactic dust formed?

    It is formed once the universe started cooling down after the big bang. It mainly contained Hydrogen and little bit of Helium. But as the stars formed and exploded during its death, the material formed inside the star got mixed with these galactic dusts making it rich with elements heavier than Hydrogen and Helium.

  10. How did the clouds condense with such less gravity?

    Clouds have enormous gravity as these are structures that are few light years across. Initially it collapses due to gravity and flattens. Then the star is formed at the center. Different elements started condensing at different places depending on how far away they are from the star, because temperature started dropping as one goes away from the star, and that helped in condensation.

  11. What happens if the heat destroys the gravity in the star?

    It cannot destroy the gravity, but it can overcome the gravitational force. If that happens, star explodes, as the gravity is not strong enough to balance the thermal pressure.

  12. How much pressure is required to begin nuclear fusion?

    Based on a search I did on the internet, it seems it requires 1017 Pascals of pressure.

  13. Why didn't all the planets collide to make one big planet?

    The were formed at different locations within the solar system, with large distances between them. Collision only happened between planets that are close enough to be pulled to each other by gravity.

  14. What happens when Iron in a star runs out?

    Iron being a heavy element, it is formed towards the end of the life of a star. Iron can get fused to form even heavier elements if the gravitational pressure is enormous. Iron will only runout after it is fused to form heavier elements. So star could continue the fusion process even after that, depending upon its size and strength of the gravitational pull towards the center. If the pressure is not strong enough then star could expand into a red giant and then eventually become a white dwarf or blackhole/neutron star (depending on how big the star was).  

  15. How did the big bang occur?

    It is one of the unsolved mysteries of the universe. Current understanding is that there was a state of singularity that was disturbed causing the expansion of the Universe. But Big Bang was not an explosion, but a sudden expansion of the space itself.

  16. What elements are formed during a GRB and a CME?

    GRB (Gamma Ray Bursts): Difficult to tell exactly, as GRB can be caused by multiple events. If it is due to merging of two neutron stars, then heavier elements in the periodic table could be formed.

    CME (Coronoal Mass Ejection): This does not produce any new material. It is basically ejection of materials already existing inside the Sun (that could be any material that is formed during fusion)

  17. Can stars die without turning into a red giant?

    No.

  18. What was before the big bang?

    No one knows, though there are several theories. I think we will never come to know.

  19. Why is there a need of axial tilt?

    There is no real need to have this tilt. But because of this tilt that Earth has, life is able to flourish (due to changing seasons).

  20. What holds our galaxy together?

    Dark Matter.

  21. Why the gas Jupiter does not compress to become gold?

    For gold to form, it requires enormous pressure, like merger of two neutron stars. Jupiter does not have any nuclear fusion going on inside, because it is not big enough to have that kind of gravitational strength to ignite a nuclear fusion inside.

  22. If many people reuse straws and bags why there is still so much plastic waste?

    Because the number of people reusing is far fewer than the number of people using and throwing.

  23. How long will it be till we run out of materials for us to use?

    Exact time duration is not known. But the current consumption requires 1.7 Earths to sustain for a long time. More details here: https://overshoot.footprintnetwork.org/

  24. If we have ways to produce renewable energy why are we still not carbon neutral?

    Because we are living a life of excesses. We are consuming more than what we need. A new car every now and then, new clothes when our wardrobe is already full, holidays in far away land, following a use-and-throw lifestyle, etc. All these requires lot more energy than hydro power, solar power and wind power can generate. We must reduce our consumption.

  25. What are the downside of eco-friendly materials?

    None.

  26. How helium gets a neutron during a nuclear fusion?

    Hydrogen goes through multiple steps in the fusion process before it becomes Helium. One of the protons in the hydrogen turns into neutron during this process.

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