143,555 reputation
13244402
bio website ratsauce.co.uk
location Chester, United Kingdom
age 54
visits member for 4 years, 6 months
seen 2 hours ago

Semi retired old time computer nerd who started programming on a Commodore Pet.

Since I'm also active in the Physics forum I should add that I started as a theoretical chemist, moved into solid state photochemistry and finally worked in industry as a colloid scientist. I only became a full time computer nerd in 1997.


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comment Why do people say “finite temperature” instead of “nonzero/positive temperature”?
The term finite is frequently (ab)used to mean greater than zero and less than infinity. Strictly speaking this is wrong because finite just means not infinite and therefore zero is a finite number as well. However the habit is so ingrained that I suspect the abuse of the terminology is here to stay. It's normally clear from the context what is meant.
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comment A very large dumbbell shaped object is floating in space. How would its gravitational pull vary with position of a nearby object?
No. A non-spherically symmetric object doesn't behave like a point mass. You'll have to calcukate the force from the bar by integrating. You could approximate it by a row of point masses. The more point masses you use the better will be your approximation.
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comment A very large dumbbell shaped object is floating in space. How would its gravitational pull vary with position of a nearby object?
As long as you are outside a sphere its gravitational field is the same as a point mass. So the two large spheres on the dumbbell produce the same gravitational field as two point masses positioned at the centres of the spheres. Just calculate the forces from the two spheres and (vector) sum them to give the total force.
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comment A very large dumbbell shaped object is floating in space. How would its gravitational pull vary with position of a nearby object?
PC, if the rod is light compared to the balls just consider it as two point masses. If the rod isn't light it's a complicated integral.
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comment A very large dumbbell shaped object is floating in space. How would its gravitational pull vary with position of a nearby object?
This is basically a homework question since you're asking us to do a calculation for you. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems. You could try asking in the chat to see if anyone is willing to do this, but as a post on this site it is off topic.
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comment Why does temperature affect the toxicity of aluminium?
@user86008: the dissolution rate of aluminium is likely to be lower at lower temperatures, so I doubt the main factor is the temperature. I suspect it's the time the food is in contact with the aluminium. Just heating tomato sauce takes only a few minutes, but if you're storing it in the fridge that will probably be for many hours or days. Either way, this is definitely a chemistry question.
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comment Bond formation in covalent bonding
Can you clarify what you're asking? A diatomic molecule is rotationally symmetric about the midpoint, so it isn't clear what you mean by the orientation. The electrons minimise their energy by increasing their density where they are as close as possible to both nuclei. Obviously this is at the midpoint between them.
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comment Diagonal part of the configuration space of two indistinguishable quantum particles
Please add links for the papers you cite. I'm not familiar with either of the papers but managed to find the Leinaas and Myrrheim paper by Googling. I have yet to locate the Laidlaw and DeWitt paper.
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comment Diagonal part of the configuration space of two indistinguishable quantum particles
According to Leinaas and Myrrheim the configuration space is singular at $\Delta$. They remove $\Delta$ to remove the singularity.
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comment Would a piece of paper look as big as a small bedroom to an atom?, or bigger?
I'm voting to close this question as off-topic because it isn't about concepts in physics
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comment Question about Sharvin resistance
Can you edit your question to explian what you have already attempted to research this? At the moment it looks as if you can't be bothered even to Google it.
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comment Why do cylinders roll easily and not square or rectangular slabs?
possible duplicate of Why doesn't a block rotate due to friction?
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comment Why does temperature affect the toxicity of aluminium?
I'm voting to close this question as off-topic because it's a question about chemistry not physics. You could try asking on the Chemistry SE.
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comment What are mesons and leptons?
@Alex: it's a very important principle of this site that OPs must be willing to put in enough effort to ask a good question. I'm not the biggest fan of downvoting, but in this case the question shows absolutely no effort. It's the sort of question that really shouldn't be here. I'm sorry, but that's the way it is. This is a physics site not the Discovery channel.
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comment Dmitri Mendeleev's Periodic Table
@KyleOman: join the physics chat and ask there
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comment What are mesons and leptons?
The most obvious of Google searches will find dozens of articles explaining what the various leptons are. I'm afraid your question shows insufficient prior research.
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comment What makes electrons behave like particles or waves at different times?
Hi Diyanko, this has been asked many times. The link ACuriousMind suggests probably gives the best discussion, though a search of the site will find many more related questions.
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comment Vertical throwing exercise
Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems.
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comment Nucleus validation
Yes, I do mean the running of the fine structure constant. It's only an issue at accelerator energies, and even then only at the high end. But it has been experimentally measured.
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comment Dmitri Mendeleev's Periodic Table
I'm voting to close this question as off-topic because it's about the history of science