Science quickies


How high is that building?
Lenses under water
Telling eggs apart
A trip around the moon
Universal solvents 1
Universal solvents 2
A puzzling puzzle
Other pages on this site


Universal solvent
Why is a universal solvent impossible?

This will help you

Universal solvent revisited
Having shown that a universal solvent is impossible, how could you keep some in a glass bottle?

This will help you

The height of a building
Your problem: to come up with a creative way of using a barometer to measure the height of a building. It is a mercury-filled Fortin barometer, 800 millimetres high, weighing just under 10 kg. Be imaginative!

This will help you get started

Which egg is which?
You have two eggs in your refrigerator. One of them has been hard-boiled, while the other egg is raw. How can you tell which egg is which?

This will help you

Underwater spectacle
Suppose you have a magnifying glass, and you want to look at a fish. Would it help to put the magnifying glass under water, close to the fish?

This will help you

Once around the moon
Your lunar exploration vehicle has fuel tanks which will carry it one third of the way around the moon, and it can carry twelve spare fuel containers, enough to take it another third of the way around the moon. This means that a full fuel load will let you travel one third of the way around the moon and back, or two thirds of the way around the moon before you run out of fuel.

You can top up the fuel tanks at any time: what is the smallest number of fuel containers (starting with the tank empty) that you will need to travel once around the moon?

And when you have solved that, can you come up with an answer for a situation where twelve fuel containers only carry you a quarter of the way around the moon?

This will help you

Can you make this?
When I saw this one, about twenty years ago, it was described to me as a test for budding architects in Russia. They were shown this shape, given a pair of scissors and a filing card, and told to make it. They had the advantage of seeing the real thing, but this is a good test of your ability to think in three dimensions.

You do not need glue, tape,staples, or any other attaching things.

This will help you understand

And now for some help

The problem with universal solvents
How can you keep a universal solvent in anything? By definition, the universal solvent dissolves everything , including any containers you may wish to store it in.

Perhaps you could snap-freeze it, or store it as two components which do not react, and just mix the components that form the universal solvent when you need some.

Don't pour it down the drains when you are finished, though!

Back to the enquiry | Back to the index

Storing a universal solvent
You can store universal solvent in a glass jar, as long as you have already added enough powdered glass to saturate the solvent with glass.

If you need to have the universal solvent work on glass, you would need to use the iron-saturated stuff that you keep in an iron vat instead.

Back to the enquiry | Back to the index

How high is that building?
The standard ("guess what I'm thinking") answer is to use the atmospheric pressure at the bottom and the top, and from this, deduce the actual height of the building.

The interesting answers I have heard include, in no particular order:

  • giving the barometer to the building manager in exchange for the information you need;
  • dropping the barometer from the top of the building and timing its fall (rather enivironmentally undesirable!!);
  • using the barometer as the weight of a pendulum, so you can dangle it on a string and time the period of the pendulum;
  • lowering the same pendulum, pulling it back up and measuring the string;
  • measuring the shadows of the pendulum and the building and using thshadow ratio to get the height ratio;
  • using the 800 mm barometer as a yardstick, working your way up the fire stairs, marking off 800 mm rises as you go.

Back to the enquiry | Back to the index

Sorting the eggs
Put one of the eggs on a dinner plate, and spin it fast. Then stop it, and watch what happens. Then do the same with the other egg, stopping it as it is spinning fast, and letting it go again.

The difference you see is due to momentum: think about what a liquid can do inside and egg shell that a solid cannot do. If you think about it, you may be able to relate this to why we feel giddy after spinning around -- look up "semi-circular canals" to find out more.

Now here is a puzzle I don't have an answer for: maybe you can find one: two cans of drink sit on the shelf in the refrigeratot. You know that your mischievous friend has just shaken one of them, very hard. How can you tell which is which, before you open it? (I would take the left-hand one, tell the friend it is the left-hand one, point it at the friend, and go to open it -- if the friend ducks, I would take the other can, and repeat the experiment, but this time, I would open it, anyhow :-) Which is well and good, but how can you telll if the friend isn't there?

Back to the enquiry | Back to the index

Lens under water
The power of a lens comes mainly from the difference between the refractive index of the lens material and the refractive index of the surroundings. Air has a refractive index of about 1, water is about 1.33, glass is about 1.5 -- work it out!

The answer annoys me -- as I get older, I see less and less when I go snorkelling, and I recently had the bright idea of attaching an old pair of spectacles to the outside of my mask. A few moments thinking, though, and I realised that I would not get the result I wanted. Can you work out how I could get the necessary help? (Hint: pince-nez .)

Back to the enquiry | Back to the index

A round trip of the moon
Six fuel containers carry you one-sixth of the way around the moon. With a full load of fuel, you can travel out one sixth of the way, dump twelve containers, and return. On your second trip, refill your tanks, and drive out to one-third of the way, dump twelve containers, return to the staging point, load the remaining six containers, and return to the base camp. Then load up with a full load of fuel, and travel around the moon in the opposite direction, arriving at the one-third dump, just as you use up all your fuel.

Back to the enquiry | Back to the index

Can you make this shape?

All I am going to say is that it can be done. :-)

In fact, I once made one from a sheet of copper -- it used to sit on my desk and puzzle people who assumed I had used solder in the making. You will have to take my word for it that I hadn't.

Back to the enquiry | Back to the index

This file is, first created on September 27, 1997. Last recorded revision (well I get lazy and forget sometimes!) was on August 23, 2000.
Worried about copyright? You need to go look at my fine print . Well, maybe you don't after you read the next paragraph, but do it anyhow . . .

©The author of this work is Peter Macinnis -- , who asserts his sole right to the product as it is packaged here, recognising that many of the ideas are common. Any non-profit educational or home use is completely acceptable without let or hindrance. Copies of this whole file or site may be made and stored or printed for personal or educational use. The work used here derives from on-going research and development which will one day lead to a book on brain food ideas.

This site had 219,000 hits on the index page from 1999 to January 2007 and an unknown number on other pages. In January 2007, a combined counter was placed on all of the pages, counting page hits which now total