We got "stuck" in an MRI machine once. The walls were less than an inch away. When they started the test the machine started clacking real loud. (Apparently this is normal.) We freaked out and hit the "bail" button but that button was really just a notice to the operator to let us out, and they took a very long time to do it. We did not complete the test and if we ever need an MRI in the future we will probably have to be heavily sedated first.

[QUOTE=Xyzzy;410725]We got "stuck" in an MRI machine once. The walls were less than an inch away. When they started the test the machine started clacking real loud. (Apparently this is normal.) We freaked out and hit the "bail" button but that button was really just a notice to the operator to let us out, and they took a very long time to do it. We did not complete the test and if we ever need an MRI in the future we will probably have to be heavily sedated first.[/QUOTE]

That is indeed normal, that's the sounds of the machine's metal undergoing the severe stress induced by the extremely strong magnetic fields. Although scary as hell, it is indeed normal.

[QUOTE=Dubslow;410741]That is indeed normal, that's the sounds of the machine's metal undergoing the severe stress induced by the extremely strong magnetic fields. Although scary as hell, it is indeed normal.[/QUOTE]I've found my MRI scans rather pleasant, which it seems, is not normal.

To me they take place while I'm cocooned in a comfortable gently lit secure environment listening to something which sounds like music written by Stockhausen and performed by Kraftwerk.

Very relaxing, not scary as hell.

[QUOTE=Uncwilly;410714]The meter should be defined by the Planck length, not by light. This would be a better foundation. :two cents:[/QUOTE]Presumably you realise that the Planck scale is partly defined by the speed of light, right?

The other physical constants which go into it are G and \hbar. Using them and c one can produce a dimensionless quantity which defines the Planck scale. Planck units are then defined in terms of that scale.

Details left as an exercise for the reader.

We still have to fix the mass constant. In more than one way. First, get rid of the physical artefact. And second get rid of that kilo- prefix: grams, only grams, nothing but grams.

[QUOTE=xilman;410753]I've found my MRI scans rather pleasant, which it seems, is not normal.[/QUOTE]

It must be your personal magnetism!

[QUOTE=Xyzzy;410725]We got "stuck" in an MRI machine once. The walls were less than an inch away. When they started the test the machine started clacking real loud. (Apparently this is normal.) We freaked out and hit the "bail" button but that button was really just a notice to the operator to let us out, and they took a very long time to do it. We did not complete the test and if we ever need an MRI in the future we will probably have to be heavily sedated first.[/QUOTE]
When I took the test years ago, the button was actually a squeezable bag that pushed air through "something" that was very loud.

So if you're freaking out and the button looks like it contains air, continuous squeezing will get faster reactions and possibly rude language.

[url]http://phys.org/news/2015-09-redefine-chemistry.html[/url]

Thought you guys might be interested in this, I'm not educated enough to really understand the differences.

[url]http://www.techtimes.com/articles/86266/20150919/supermoon-lunar-eclipse-to-occur-on-sept-27-what-makes-this-celestial-event-special.htm[/url]

[url]http://www.natureworldreport.com/2015/09/tree-of-life-containing-2-3-million-species-released/[/url]

[QUOTE=xilman;410753]I've found my MRI scans rather pleasant, which it seems, is not normal.
[/QUOTE]


I had a head scan the other week. I found the experience of having your head in a giant square wave generator was rather pleasant. At some point when it felt like my head was in resonance that felt weird, but it was an awesome sensory experience overall. I've never 'felt' noises like that.