I'll Believe It When I See It

• Have you ever wanted something badly, then when you finally got it, you found out it wasn't as good as you expected?
• Have you ever thought you'd believe something if X, then when X happened, you found other excuses?

The thing is, things are rarely clear-cut. I just wanted to say this in response to believing things, like believing who someone is online, or pseudoscience. Whatever evidence you want, there's an alternative explanation.

Does Nature use wavelengths outside the visible spectrum?

I wonder if Nature uses infra-red or ultraviolet markings. I know some flowers use UV and bees can see in UV. Isn't it coincidental that the spectrum we see is so similar to the one Nature uses? I wonder which came first, and why this range was chosen.

Brain tags

After reading the book Incognito by David Eagleman, I suspect the brain works by tagging thoughts with things like "real", "imaginary", "past", "present" and "future". Malfunctions with tags result in things like deja vu (present event tagged as past) and hallucinations (imaginary tagged as real). If only there were a way to tag memories as present, then we could relive our memories.

Exchanging one poison for another

Many products claim to be free of one thing or another, in turn being better for you or the environment. I think this is a marketing gimmick, because on inspection they are replaced with something else, usually newer, less tested and so with less known about them.

My first example is MSG. It causes thirst and headaches in some people. I saw a brand of instant noodles claiming to be MSG free. This does not mean it is replaced by some natural ingredient, instead the noodles contains some chemical I didn't recognise, so I stuck to the tried and tested MSG.

The other example is acetone free nail polish remover. People know acetone is bad for them, so a nail polish remover without acetone must be better, right? Maybe you'd prefer MEK, almost identical to acetone, gamma butyrolactone http://www.ncbi.nlm.nih.gov/pubmed/16035208 or good old highly toxic methanol?

Other examples I could think of:

• BFRs
• Bisphenol-A
• Dioxins
• CFCs

Very often, the replacement isn't safer, it's just that we don't know how dangerous it is yet. I believe some replacements will be found to be worse than the original in the future.

Polarisers/polarizers

How do the polarisers in black and white LCD screens work? Polarisers have to block 50% of unpolarised light, but those screens are too bright to be 50%.

We see in 2D

I'm convinced that we actually see in 2D, or maybe pseudo-3D, and N-dimensional beings see in N-1 dimensions.

What I mean

• By "seeing in 2D", I mean that what we see can be expressed in a 2D image
• In other words, we can only see the front of objects. We cannot see what is behind, or blocked
• We also have some distance data, which is what I mean by "pseudo-3D"
• I would consider "seeing in 3D" to be able to see all sides of an object at the same time

Why I'm bringing this up

• In most "flatland" or 2D movies/stories, the world is shown from our point of view and we can see the entire world at once
• The characters also behave as though they are able to see what we see - what's behind other objects etc.
• What they see should really be expressed as a line
  

The Leidenfrost effect

The Leidenfrost effect is when the vapour produced by the surface of a liquid boiling insulates the liquid. It causes the skittering of water droplets over a hot surface. You can see experiments on YouTube where people dip their hands in molten lead without getting burnt. My question is: why doesn't this work with hot oil?

Polymorphs of silica

I haven't posted for a while. Merry Christmas to you!

What's the difference between silica, quartz, glass, silica gel, aerogel and zeolites? They all can be made only of Si and O. I think quartz and silica are crystalline, and the last 3 are porous.

Current and the path of least resistance

Someone in my Physics class once told me that electrical current ONLY flows through the path of least resistance. This is a serious misconception. This explanation might have been useful in explaining why a light bulb does not light up when a battery is short circuited, but I don't think it should be promoted.

The correct statement is current flows through ALL paths, inversely proportional to their resistance. Think about it: if you connect different kinds of light bulbs in parallel, does only 1 light up, or all of them? If current only flowed through the path of least resistance, only the highest wattage bulb would light up, wouldn't it?

Adhesion problems

Recently, my posters have been falling off the walls, both at home and in the office. My friend's poster too. I wonder if it's something to do with the weather?

1 poster I restuck fell off again, and 1 new poster fell off. At least my walls are easy to clean.

Things people believe that don't make sense

In school we learned that the filament of an incandescent bulb was made thin and coiled and double coiled to increase its resistance. It was also made of tungsten, a material with a high resistance. Now, if they wanted a high resistance, why didn't they just make it out of wood? Don't tell me carbon is a product of wood, you know wood has a much higher resistance than carbon. Something's missing here.

Flies hit by trains

I was wondering about this, and I think I've explained it satisfactorily:

Consider a fly getting hit by a train. The fly is initially hovering at rest relative to the ground. At the instant when the train hits it, they have the same speed. Does that mean the train stops momentarily? Does the fly stop the train?

Situation 1:
The fly is a point with small mass.
First let me explain this: things must bend (strain) to apply a force. Before you put a book on a table, does the table apply any force? No. After you place the book, the table applies a force to equalise the book's weight, keeping it stationary. Where does this force come from? The table deflects slightly, so slightly that you can't see it (unless you have a lousy table).
At the instant of impact, the windscreen of the train bends slightly. Glass is very stiff, so this slight bending imparts a very large force on the fly. The large force results in a large acceleration. Together, the bending of the glass and the acceleration of the fly result in them moving together.
Don't understand? Imagine the windscreen of the train is a rubber sheet. When a fly hits it, the rubber sheet bends inwards, towards the train. The part of the sheet that bends actually slows down. At the same time, the fly speeds up. The fly and sheet remain in contact.

Situation 2:
Point heavy mass e.g. pebble.
This mass requires a larger force for the same acceleration, so the glass must bend more. If the glass bends too much, it cracks. This is what happens if a large enough stone hits the windscreen.

Situation 3:
Soft heavy mass e.g. tomato.
This time, different parts of the soft mass can accelerate at different rates. When the train hits it, the outer layers accelerate first, then the inner layers. This inconsistent acceleration is what causes damage to the object.

It may seem trivial, but I think these thought experiments are important in the consistency of physics.

Time travellers

People say we won't ever invent time travel, because if we did, we would have met time travellers by now. People also say the world is getting worse, more wars, natural disasters etc.

How do we know the world wasn't even worse, e.g. there were 4 or 5 World Wars, then after all that settled down, what was left of humanity invented time travel to improve history? Maybe the world now has been influenced by time travellers without our knowledge and currently has the best future they can manage.

Things people believe that don't make sense

People say salt crystals consist of alternating + and - ions held together by electrostatic forces. Why then can't you put 2 crystals together and make them stick? Oh sure, there are defects, but if you take a tiny perfect crystal and cleave it in half, you can't get the halves to stick no matter what. Something is fishy here.

Bike on an escalator

I've always wondered about this: if you have a bike facing downwards on an upward traveling escalator (or conveyor belt), is it possible to remain stationary? Or will the bike always roll downwards? I'm sure if the escalator's speed is constant, the bike will move, so if the bike is to stay stationary, the escalator's speed has to increase. That isn't to say if the speed increases, the bike will stay stationary.

Birds on electricity wires

Why do people ask why don't birds get electrocuted when they perch on wires? Maybe the wires are, you know, insulated?

want^2

A thought experiment. Imagine this conversation between 2 people:
A: I want to get some exercise.
B: That's great! Exercise is good for you, but I'm too lazy. I wish I could feel that way. I want to want to get some exercise.

Is it possible to have a desire to have a desire for something, or does it boil down to a single desire? If it's possible, how many layers can it go?

Squeaky polystyrene

Has anybody noticed that polystyrene (styrofoam) tends to squeak? It's not as annoying when the foam squeaks, but solid polystyrene squeaks almost like claws on chalkboard. Try it for yourself. Take some polystyrene (transparent chocolate boxes or CD covers are an easy source) and rub it across the table.
I wonder what properties of polystyrene make it squeak easily, and what other materials squeak as well?

Things people believe that don't make sense

Has anyone noticed that some things people believe actually don't make sense when you think about them? I'm talking about science, not superstition or myth. I think we should question our beliefs, just in case we miss any discoveries. Here are 2 examples:

In the experiment where you place a candle in a bowl of water and cover it with a glass, after a while the water rises and the candle goes out. People claim the water rises by 20% of the height of the glass, showing the oxygen is used up.
Some observant students noticed that when you use 2 candles, the water rises more! Does that mean 2 candles burn oxygen more completely? No, the reason the water rises is that the air, which used to be heated by the candle, cools after the candle goes out and contracts. This pulls the water up. 2 candles make the air hotter, which means it contracts more, pulling more water. The candle actually goes out before all the oxygen is used up.

To prove air has mass, 2 balloons are balanced on a scale. 1 balloon is popped. The other balloon sinks!
This experiment is totally flawed once you look at it. Obviously after popping and having rubber pieces flying everywhere, the other balloon will be heavier. An improvement is comparing an inflated balloon and an uninflated balloon. However, this still won't work because the experiment is immersed in air, so the buoyancy effect of air cancels the weight of air out. If you fill a balloon with water and have another empty balloon, and weigh both underwater, which will weigh more?

A vacuum airship

What's lighter than air?  Hot air, helium, hydrogen. What's even lighter than them? A vacuum. If we could make a shell that would withstand a vacuum inside, we could make a ship that floats based on vacuum! Not very practical, but pretty cool. Of course, such a ship would be abhorrent to Nature.