The 3rd dimension
Read our general notes on Risk Assessment
Why don't we fall through the floor?
http://www.amazon.com/exec/obidos/ASIN/0691023808/ref%3Dnosim/icivilengineer103-9080566-6853405/104-3643306-3025516How come that we feel solid although objects are made up of atoms and there is loads of space between each? Are humans simply energy projections?
These questions were recently submitted to this web site. The first question reminded us of an excellent book by J E Gordon published a long time ago by Penguin but still available from Princeton University Press and on sale at Amazon.com. The Amazon reviews are very enthusiastic.
Read the first chapter in James Gordon's book called 'The New Science of Strong Materials' for a detailed discussion of the first question. The book is so well known that it is quite likely to be available from local libraries or even your school/college library.
Here is our brief response.
First question:
The empty space is mostly within atoms, but the argument goes something like this. If you consider two atoms approaching each other there will be attractive forces operating tending to draw them together and repulsive forces (between charge clouds and between nuclei) tending to keep them apart. At larger inter-atomic distances the attractive forces ‘win’. At very small distances the repulsive forces are greater. The atoms settle, as it were, at such a distance that the attractive and repulsive forces exactly balance. A solid can be thought of as being built up, one atom at a time, using the same principle.
It follows, therefore, that any attempt to displace atoms from their equilibrium positions requires the expenditure of energy – much more than would be provided by mere touch. This model is fine hypothetically at the absolute zero of temperature – at higher temperatures thermal energy causes vibration of the atoms, but this is random in direction and does not make it any easier to displace atoms in bulk – the solid still feels solid.
Second question:
We believe it is true to say that all objects have their energy equivalent. Very small objects such as electrons can be shown to have a wavelength as if they were not objects at all but waves – this wavelength is such that electron beams can be diffracted by atoms in a similar way to, say, X-rays, leading to an investigative technique called electron diffraction. Larger objects have such long wavelengths that you don’t appreciate their wave properties at all so that they behave virtually exclusively as if they were particles. I understand from Physics teachers that it is possible to calculate the wavelength of a human being so perhaps you are right!
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updated: 30 January 2007
