Top Ten Tricky Science Questions
Answers to More Tricky Science Questions
After the huge success of my last hub, Top 10 Tricky Science Questions: Answered, I decided to do a follow up. Here you will find 10 more tricky science questions such as 'why does ice float?' and 'how big is space?' and other such questions that have arisen whilst teaching science.
As with my first list, each question has a straightforward answer, followed by a slightly fuller explanation and, where necessary, a link or video for more information. Enjoy!
1. Why Does Ice Float?
When water freezes, it expands (see why here). This means that the water's mass gets spread over a larger area when it freezes. Due to this expansion, ice is less dense than water, and so floats on top! Quite lucky really! Imagine what would happen to life if ponds froze from the bottom up...
Explanation: The principle of ice expanding can be demonstrated in a simple experiment. Get two transparent plastic cups and half fill them with water. Put cling-film over the top of both to prevent evaporation. Place one cup in the freezer and wait a few hours. The cup you placed in the freezer will be at a higher level than the water. As you know you started with the same amount of water, the water must have expanded.
Something that is less dense than water cannot push the water atoms out of the way and so floats on top. Rocks are much more dense than water and can easily push water molecules out of the way - this allows them to sink
2. How does a Jet Engine Work?
A Jet Engine's genius lies in its simplicity, and is an example of Newton's Third Law:
For every action there is an equal and opposite reaction
A Jet engine works on the principle of suck, squeeze, spray, spark, blow
Explanation: In brief a jet engine:
- Uses a turbine to suck air in (suck)
- Uses a compressor to compress this air (squeeze)
- Injects Fuel into the compressed air (spray)
- Ignites this fuel (spark)
- Blows the expanding gases out of the back of the engine (blow)
3. Why Does the Moon Sometimes Look Red/Huge?
My last question hub answered 'Why is the Sky Blue;' the Answer to this question has a similar principle.
The Moon can appear red for several reasons. In desert regions dust can scatter the light reflected from the moon, giving it a reddish quality. Far more spectacular, however, is a Lunar Eclipse. Instead of the Moon blocking the Sun as in a Solar Eclipse, a Lunar Eclipse occurs when the Earth gets between the Sun and the Moon. The Earth's atmosphere acts as a filter (just like on stage lights) allowing more red light through than other wavelengths of light. This light gets reflected back off the Moon, giving a red colour.
Explanation: We see the Moon because it reflects the Sun's light. When the light from the Sun gets scattered by the Earth's atmosphere, more red-wavelength light lands on the surface of the Moon than blue-wavelength light. This means more red light is reflected back towards Earth. Many of the different colours the Moon appears to take on are due to the filtering effects of our atmosphere.
The Moon can appear larger and smaller due to the effects of perspective (technically called the Ponzo Illusion.) When the Moon is high in the sky, you have nothing to give you a sense of scale. When the moon is close to the horizon, you can compare it to trees and buildings. Need proof? Next time you see the Moon out, hold out your hand with your thumb up. The moon should be neatly covered by your thumbnail. Try the same trick when the Moon appears large - your thumbnail will still neatly cover it.
More proof!? O.K., try this - Next time the Moon looks huge, roll up a piece of paper and look at the Moon through that. This breaks the optical illusion by removing any objects your eyes use to 'scale' the Moon.
Addendum: As was pointed out, there is much more to the Ponzo illusion than mere scale. Check out this link, courtesy of scottcgruber, which explains it in full.
4. Are Humans Still Evolving?
Most scientists agree that the human race is still evolving. We may bicker about the driving force of evolution, but as long as mutations can enter the human gene pool, the possibility for change (evolution) persists
Explanation: This is quite a contentious issue. Steve Jones, from University College London, has argued that Natural Selection is no longer important for humans. After all, in the last 500 years, a British Baby had a 50% chance of surviving to adulthood; now the figure stands at 99%.The weak are no longer getting weeded out by natural selection. This does not, however, mean that evolution is not occurring - merely that natural selection is not driving it.
Sexual selection for so called 'desirable-traits' could be the main driver of human evolution. When combined with high rates of migration, huge population size and promiscuity, mutations are actually entering the human genome at an unprecedented rate. People are also getting better at choosing mates based on intelligence, athleticism, physical health etc. This may mean that advantageous mutations are selected for. This may even be accelarating the rate of human evolution, as new mutations have plenty of opportunities to become fixed in a population.
The factors that people state have 'halted' evolution (medicine, culture, equality) have only taken root in the last few hundred years - yesterday in evolutionary terms, definitely not long enough to have an effect on our evolution. Most experts agree that all species are continually evolving - just at different rates. As long as there are mutations in the genetic code, there is the possibility for change. Sustained change, whatever the driver of this change, will always result in evolution.
5. How Big is Space?
In short, vast.
The Universe is on a scale that can barely be imagined. Forunately, this is what we have special effects departments for. The video opposite can give you an inkling of the the vastness of the universe, as well as the scale of the microscopic world.
(NB: The video opposite is a revamped, Hi-Def version of the original and groundbreaking 'Powers of Ten' video by Charles and Ray Eames. The original video is still amazing and well worth a look.)
6. How did the Sea get it's Smell?
Have you been told the seaside smells like it does because of the salt? Not quite. The smell is caused by a chemical called Dimethyl Sulfide (DMS). This chemical is used to make clouds, and flavour food. This chemical is made by plankton (tiny organisms living in the sea). We are not sure why these organisms do this though!
7. What is a Burp/Hiccough?
A burp is nothing but a noisy release of gas - just like a fart! Where does this gas come from? Good question! Most of this gas is just air that we have swallowed whilst eating. The rest usually comes from fizzy drinks - the bubbles in these drinks are carbon dioxide gas...and that gas has to go somewhere! The excess gas escapes the stomach, travels up the food pipe (oesophagus) and exits via the mouth. The sound is made by the speed at which this gas travels.
A Hiccough (or hiccup) is completely different. From the science museum website, a hiccup is:
"... a kind of forced intake of breath, caused by spasms in your chest and throat There are over 100 causes for hiccups, but the most common is irritation of the stomach or the oesophagus. The "hic" noise comes when the breath is cut off by the snapping shut of your glottis - which is like a fleshy lid or trapdoor that separates the food and air tubes in your throat."
We don't know what hiccups are for.
8. Why does Helium Make Your Voice go Funny?
Helium is six-times less dense than air. This allows sound waves to travel through the helium much faster, causing a squeaky voice. Pretty much what is said in the video...without the hilarious voice.
Explanation: Sound is caused by the vibration of particles in a solid, liquid or a gas. The pitch of a sound is almost entirely related to how quickly the sound wave makes the particles vibrate. High pitched sounds are caused by fast moving sound waves; low-pitched sounds are caused by slow moving sound waves. Our sound waves for speech are made in the voicebox. If we fill this box with a gas of a different density to air, sound waves can travel through it at different speeds, creating different pitches.
9. What is Space Made Of?
Mainly? Nothing. And Everything. If you take a look at the video above you can see that, zoomed right out to the edge of the visible universe, most of space is empty blackness. But space also contains everything, everywhere!
Explanation: It all depends on your perspective. Are you talking about:
- space, the vacuum; or
- space, everything outside the Earth's Atmosphere
The vacuum of space contains only a few hydrogen atoms per cubic metre (A perfect vacuum - a region with no matter at all - is a practical impossibility). That is pretty empty... Whilst the Deep Field Image opposite may make space look rather crowded, take a look at how much of the picture is still black.
But it isn't that simple! If you define space as everything that is not Earth, the space is made up of Everything, Everywhere in the Universe
But then, the Universe is said to be in space....anyone else's head starting to throb?
If that made your head hurt, chew on this: If we are made of atoms, and atoms are 99% empty space, how are we solid!?
10. How did Saturn get it's Rings?
Saturn's rings are not solid. They are made of billions of particles of ice, dust and rock. These particles can be as small as a grain of sand or as large as a house. The rings are huge, but very thin - the largest ones can be up to 170,000 miles wide, but only 200 metres thick. But where did they come from?
Explanation: We are not sure, but we think the rings were made when objects like comets, asteroids or moons were ripped apart by Saturn's strong gravity. These pieces kept colliding making smaller and smaller pieces. These pieces remained trapped by Saturn's gravity and entered orbit around the planet.