It was Jan 2022. My community was in a lockdown due to the ongoing pandemic. With everyone locked up inside their home, I thought this is a good opportunity to interact with the children virtually to keep them engaged. I asked the parents of children in the age group of 5 to 10 years to come up with questions related to science in general and astronomy, so that I could field those questions in the virtual session. Why 5 to 10 years? Because this is the age where they should be the most inquisitive towards everything around them, and many times the questions from young children can open up new avenues for knowledge and exploration. So here we are, a collection of questions, and my answers to them, received from the children of my community, Casagrand Luxus:
When will all the Hydrogen get exhausted in the Universe?
Ans: One estimation is 10 to the power of 13 years from now. But will all Hydrogen be exhausted? No, because not all molecular clouds that contain Hydrogen would collapse to form stars. So there will be still Hydrogen left in those clouds forever.
Why Moon is not colourful like Earth?
Ans: Because the Moon has no atmosphere and water. Also the Lunar soil is mainly made of fine rock particles, which is predominantly different shades of grey. So Moon appears in different hues of grey (light to dark)
What is the actual colour of the Sun?
Ans: White. Sun appears orange during sunrise and sunset due to scattering of blue light over large distance, leaving only red end of the rainbow colours visible to us at that time.
Why the sky is blue?
Ans: Due to a phenomenon called "Raileigh's scattering". Violet, Indigo and Blue have shorter wavelengths compared to red and orange. So those colours get scattered more. But sunlight has more blues than violet and indigo. Also our brain is not so sensitive to violet and indigo. All these make the sky blue.
Like Blackhole, is there a Whitehole as well?
There is no proof that Whitehold exists. If it does, it could be the other end of a blackhole through which light escapes into another Universe, perhaps.
Why there is an asteroid belt and why it is between Mars and Jupiter only?
Asteroid belt is in a way the debris left behind after the solar system formation. It is found between Jupiter and Mars because Jupiter being a massive planet, it did not allow a planet being formed using the asteroids in the belt.
Why is pluto no longer a planet?
Two main reasons: Pluto turned out to be much smaller than initially thought. Because of its tiny size, it was unable to clear its neighbourhood off debris. Also it's orbit is too unstable and sometimes even crosses into Neptune's orbit.
Why doesn't it snow in Bangalore?
Because Bangalore is not that cold to condense water droplets into snow crystals, unlike high altitude areas like Himalayas.
Why stars twinkle?
Twinkling is caused by the light rays disturbed by our atmosphere's turbulence. Starlight is coming from nearly a point of light, as stars are far away. Whereas planets are nearby and the light is coming from a bigger cross section of the planet compared to stars. So the twinkling of lights from planet is not that much compared to stars.
What is the rings of Saturn made of?
Mainly ice and dust particles
Why the rings of Saturn did not become moons?
Because the size of Saturn exerted too much pressure on the small particles that were trying to come together to form the moons. The current moons are likely to be captured from the neighbourhood.
What Jupiter is made of?
Mainly lighter gases like Hydrogen and Helium, but with a solid core consisting of heavy elements like silicates, iron, etc.
What happens if the Sun suddenly disappears?
We will come to know only after 8 minutes. After 8 minutes, the gravitation influence Sun has on Earth to keep it in its orbit disappears and Earth will fly outside of the solar system in a tangent. Over time all vegetation will die with photosynthesis stopping. All life that depend on the Sun will also eventually die of starvation and cold. However, there are nearly 25 billion tons of micro organisms that live beneath the surface of the Earth. They live off the heat coming from the molten core of Earth. As long as Earth has the hot interior, these micro organisms will continue to live though life on the surface is completely gone. Additional details here: https://astronomy.com/news/2018/12/scientists-discover-staggering-amount-of-life-deep-within-earth
Are there aliens?
No proof yet. Difficult to find out through optical telescopes. So we listen for radio signals using Radio telescopes. But so far no such signal is received. Multiple reasons for this silence:
Aliens may not be existing
Aliens do exist but :
they arestill primitive and do not have the technology to create radio signals
they arefar more advanced than humans. So they may not be interested in us.
they live in a planet that is too far from us, and signals may not have reached us yet
they would have destroyed themselves through war or environmental destruction.
Additional questions (not from the children)
How seasons are formed?
Due to axial tilt of Earth. More details to be added later.
Why nightsky is not bright, if there are trillions of stars in the Universe?
Olber's paradox to be explained.
Does colour really exist?
No, it does not. Colour is a perception of the brain. The light carries a spectra of 7 colours. But what we see is the specific colour in that spectra that is emitted by the object that you are seeing. So if an apple looks red because it has all colours in the light, except red. The red is reflected and all other colours are absorbed. So in reality Apple is anything bur red.