Science: Technoquest
Your support helps us to tell the story
From reproductive rights to climate change to Big Tech, The Independent is on the ground when the story is developing. Whether it's investigating the financials of Elon Musk's pro-Trump PAC or producing our latest documentary, 'The A Word', which shines a light on the American women fighting for reproductive rights, we know how important it is to parse out the facts from the messaging.
At such a critical moment in US history, we need reporters on the ground. Your donation allows us to keep sending journalists to speak to both sides of the story.
The Independent is trusted by Americans across the entire political spectrum. And unlike many other quality news outlets, we choose not to lock Americans out of our reporting and analysis with paywalls. We believe quality journalism should be available to everyone, paid for by those who can afford it.
Your support makes all the difference.Q How does the retina work?
The retina, at the back of the eye, is a complex structure which has a deep layer of light-sensitive cells called rods and cones, a middle layer of bipolar neurones and a surface layer of ganglion (nerve) cells. The neurones connect the rods and cones with the ganglion cells, fibres from which join to form the optic nerve.
This means that the front surface of the retina, which is about the size of a postage stamp, is not the light-sensitive part, because it's covered with blood vessels and nerve cells. But the brain ignores these obstructions; we do not see them as part of our image of the world. Instead, the back is the light-sensitive part, and the surface acts as a projection screen. The rods and cones capture the light, which is transmitted to the brain via the optic nerve, from which we gain our picture of the world.
Q Some microwave food containers seem to have metallic films on top of them. Isn't that dangerous, because metal things in microwaves cause sparks?
Metal containers can produce dangerous arcing in a microwave oven. However, many food packages actually contain thin films of metal that speed the cooking process. For example, new packaging techniques use polyethylene terephthalate (PET) film laminated to paperboard as a "heat susceptor" - a metallised film that absorbs microwaves, and becomes a miniature frying pan to brown or fry the foods in the package.
So yes, metal in sufficient thicknesses can cause sparking. But thin films can improve the cooking ability of the microwave.
Q If you've got ice cubes in a glass of water, what happens to the level of water when they melt?
The water level stays the same. The amount of space the ice cube takes up in the water is exactly the same size as the water it makes when it melts, even though some of the ice cube sticks up out of the water. This is because water shrinks when it melts and expands when it freezes, so the amount that's sticking above the water indicates the extent that the frozen water has expanded.
This, incidentally, is why the threat of sea-level rise from global warming is not due to melting icebergs. It's due to the melting of ice which presently lies on land.
Q What is the current number of species in the world?
The guesstimates for the number of species present in the world at the moment are between 10 and 30 million. Of these, more than 90 per cent are invertebrates. The World Conservation Monitoring Centre's records for 1996 are: 4,237 mammals; 22,000-plus fish; 9,672 birds; 4,000-plus reptiles; 6,500-plus amphibians; 460,000-plus plants; and more than 1 million invertebrates (though there are likely to be millions more).
Questions for this column may be submitted via e-mail to sci.net@campus.bt.com. You can also visit the Technoquest World Wide Web site at: http://www.sciencenet.org.uk Questions and answers provided by ScienceLine's Dial-A-Scientist on 0345 600444
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies
Comments