104,797 reputation
4154282
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 8 months
seen 3 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.


5h
comment Can one model a spiral galaxy with a similar manifold to one for a whirlpool?
Not quite a duplicate, but pretty close: Could galactic rotation be similar to an irrotational vortex?
6h
comment What are the factors affecting transparency and color of a substance
AvZ: have a look through the results you get if you search this site for transparent
6h
comment finding angle of intersection in terms of the angle between mirrors
I get $180 - 2\theta$ as well. That doesn't mean your working is correct of course :-)
7h
comment Did the Big Bang happen at a point?
@JamesRyan: no. In fact it's impossible for time to be curved without space being curved as the answers to this question of mine show. The time coordinate in the FLRW metric is called comoving time and corresponds to the time shown on your wristwatch if you're floating at rest with respect to the rest of the universe.
7h
comment If I squeeze something really hard, will it ever become two-dimensional?
@SnowCrash: a black hole reduces everything to zero dimensions i.e. a point. There is no known black sheet that reduces everything to two dimensions.
7h
comment Did the Big Bang happen at a point?
@MarcvanLeeuwen: So at the Big Bang we have the very odd situation where the spacing between every point in the universe is zero, but the universe is still infinite is what makes the Big Bang a singularity. If you're interested the Physics chat starts in an hour and that's probably a better discussion venue that using comments.
7h
comment Did the Big Bang happen at a point?
@Jim: good point, I should make clear this is just FLRW and doesn't consider inflation.
8h
comment Did the Big Bang happen at a point?
@MarcvanLeeuwen: but at the moment of the Big Bang all spacetime points were in the same place. We are not talking about distant events.
8h
comment Did the Big Bang happen at a point?
@KyleKanos: oops, thanks :-)
10h
comment Did the Big Bang happen at a point?
@m4r35n357: I did consider that, but there is a great temptation when writing this sort of post to get diverted down interesting but irrelevant side paths. I decided not to go into the details of Fred Hoyle's views.
13h
comment Nuclear fusion using electromagnetic fields
@rmhleo: In tokomaks like JET and ITER the magnetic fields are used to confine the particles, but their energy comes from heating them with a large electric current. The mechanism is completely different to the LHC.
13h
comment By what factor a planet travels (in circular orbit) faster than another
@Jesse: Bingo! :-)
13h
comment If I squeeze something really hard, will it ever become two-dimensional?
@Falco: the wavelength of an atom depends on the energy. For a carbon atom to have a wavelength of greater than 1nm its energy needs to be less than about 0.0001eV, but at room temperature $kT \approx$ 0.025eV. So you aren't going to get 2D behaviour from atoms without special conditions.
16h
comment Centripetal motion (Average force vs magnitude of velocity)
possible duplicate of Relationship between centripetal force and magnitude of velocity
16h
comment Relationship between centripetal force and magnitude of velocity
Can you make it clearer what you mean by increasing the average force? Maybe sketch out a diagram of your experiment. How are you applying this force and to what?
17h
comment Infinite Universe and the big bang
The Big Bang didn't happen at a point; it happened everywhere. However you're correct that the FLRW metric predicts an infinite density at $t = 0$. I think the expansion rate is also infinite ($\dot{a}/a$ is certainly infinite) but I would have to check to be sure. Few physicists think this makes sense either, and we expect quantum effects to enforce a finite maximum density. The CMB didn't exist until 380,000 years after the Big Bang.
17h
comment If I squeeze something really hard, will it ever become two-dimensional?
@robertbristow-johnson: how would you confine any system to a thickness of a Planck length? What physical mechanisms exist that could do this, even in principle?
2d
comment Is relativistic event horizon half of newtonian event horizon?
I suspect the question is based on this article, or one like it.
2d
comment How to calculate the ship resistance caused by water viscosity
A Google search for hull drag would be a good place to start doing some research for yourself. Ignore the links related to drag queens in Hull - they are unrelated to ships.
2d
comment Is relativistic event horizon half of newtonian event horizon?
Also possibly related How can gravity affect light?. Achmed, can you make it clear what you mean by the relativistic event horizon half of newtonian event horizon?