Why is ice clear and snow white?
September 2nd, 2010 by Peter Stotereau
Snow comprises huge numbers of ice crystals with lots of trapped air between them. If we could look at a single tiny ice crystal within the snow, it would look clear.
Visible light from the sun is made up of components of different wavelength (the electromagnetic spectrum as in a rainbow; red, orange, yellow, green, blue, indigo, violet). When the light hits a single ice crystal, some of it is absorbed and some reflected back; on passing through the crystal the light changes direction due to a process called refraction, as in a prism, and can be internally reflected within the crystal.
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How do 3D glasses work?
August 12th, 2010 by Michael de Podesta
Normal 3 D vision works because our left eye has a slightly different view of the world from our right eye.
3 D glasses typically have the left-hand optic covered in red and the right hand-optic covered in blue. The 3-D material – a picture or a single frame of a film – has two images printed, one in red and one in blue. When we view this image through the glasses our left eye mainly sees the image printed in red and our right eye mainly sees the image printed in blue. Our brain interprets the differences between the different images as being due to differences n perspective and reconstructs a 3-D view of the scene. Read the rest of this entry »
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Why does paint dry on the wall but does not harden when in the tin?
July 21st, 2010 by Peter Stotereau
There are two basic mechanisms by which paints dry on the wall.
Many modern paints are largely water-based. As we know, water readily evaporates. However, the rate of evaporation of a liquid depends on the vapour pressure of that liquid above the surface. In a sealed tin of paint, a set vapour pressure is quickly established in the small headspace in the tin and the water in the paint does not evaporate and remains in the paint. But, when painted on the wall, the water can readily evaporate to leave a dried film of solid paint components behind – there is no build-up of water vapour pressure in a confined space as there is in the tin.
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Welcome to Ask a Scientist
July 15th, 2010 by Lloyd England
Ask a Scientist is a new site which aims to bring people face to face with real scientists to get them to answer their questions. Anyone over the age of 14 can submit questions via the site, or via twitter and the best will be selected and answered from scientists working from a wide range of fields from all around the UK. But the conversation doesn’t stop there. You can freely comment on the questions posted if you have different opinions from our scientists’, or even if you just want to comment on the answer! For more information on the site, please see the about page.
Use social media? So do we! We’re on Facebook, Twitter and Youtube – so if you like the site, show your support and like us or follow us! You can ask questions via twitter simply by @replying our twitter account, @askascientist – and they’ll be added to our question bank, ready and waiting for our scientists to answer!
Want to know about the people behind the answers? You can find out about them on our authors page.
We hope you enjoy the site, find it useful and contribute your own answers and comments. If you are a teacher or scientist and like what you see and want to get involved yourself, get more details about getting involved.
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Can salt lose its saltiness?
July 10th, 2010 by Peter Stotereau
Common salt comprises a very stable, simple chemical compound called sodium chloride, which has a salty flavour. As table salt, it typically also contains minor amounts of additives to keep it free-flowing.
As it is so chemically stable, sodium chloride will not lose its saltiness, even after being stored dry for many years. However, there are ways in which salt may appear to lose its saltiness.
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How do you build a water rocket?
July 8th, 2010 by Andrew Hanson
Andrew Hanson, from the National Physical Laboratory, explains how to build you very own water rocket, which is capable of being launched and flown in the air. With some basic, everyday household items and tools you’ll be able to make your own rocket in only an hour or so.
Safety Warning: Before you start, please be aware that water rockets can be a dangerous activity – which requires you to fire a highly pressurised rocket at high speed into the air. Please take the time to act safely, and never fire any rockets towards other people or animals.
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Why are plants green?
July 2nd, 2010 by Richard Gilham
I guess there are two parts to the answer- why is green a good colour for plants to be, and how do they go about it. The key to the first part lies in how plants go about the business of living- they use light energy from the sun to drive the process of photosynthesis, which converts carbon dioxide into the sugars that they need to survive.
The fact that the leaves are green is because they are reflecting green light, and absorbing the other colours in the visible spectrum. When the light is absorbed, it is absorbed by the atoms that make up the leaves. These atoms, stuck together in molecules, gain energy from the light and this is needed to run photosynthesis. The reason plants decide to use visible light as opposed to infra-red or ultra-violet light is the same reason as why we see in the visible- there’s plenty of it around to use!
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Science isn’t just a subject, it’s a career
June 22nd, 2010 by Laurie Winkless
Laurie Winkless, a Higher Research Scientist at the National Physical Laboratory, answers questions on her career into science and her inspiration of why she chose to become a scientist. Laurie has a BA (Hons) in Physics with Astrophysics, a MSc in Space Science and has just started a PhD in Nanostructured Thermoelectrics!
What inspired you to study physics?
I’ve loved science since before I knew what the term meant! I was constantly asking questions as a child, and loved anything mechanical. Once I realised that I wanted to have a science-based career, my entire family thought I was crazy, but they encouraged it!
At the age of about twelve, I first read the book that has most shaped me. Its called “Yeager” and it’s about General Chuck Yeager, an amazing combat pilot and the first human to break the sound barrier in a jet called the Bell X-1. His story is an inspirational one. The son of a poor farming family, he joined the US Air Force at 18 and worked his way up through the ranks. He understood the importance and function of every component in all of the planes he flew (and still flies). He never accepted a “rough approximation”, he learned as much as possible about the “hows”, “whys” and “what ifs”.
Tags: career
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What is beyond the edge of the universe?
June 15th, 2010 by Michael de Podesta
Firstly – and obviously – nobody knows. But you have actually asked two questions.
Firstly there is the observable universe, and then there is the Universe, and then there is your question. As we understand it at the moment, the story goes like this:
Initially the universe was filled with ‘primordial substance’ (protons, neutrons, and electrons mainly but not assembled into atoms) and was opaque to light and radio waves. About 300,000 years after the big bang, the universe condensed from separate protons and neutrons and electrons into atoms and at this point the universe became transparent.
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What does “splitting the atom” mean?
June 14th, 2010 by Michael de Podesta
It is a very confusing term. In a sense every chemical reaction ‘splits’ atoms because it takes or adds electrons away from atoms. However the phrase would be more correct if we spoke of splitting the nucleus of an atom.
This can be done in a number of ways, but typically, it involves bombarding a substance with protons or neutrons or even entire nuclei of other atoms. Most of the particles don’t hit nuclei in the target but some do, and by interact electrically and through the strong force they can break up a nucleus.
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