106,067 reputation
4156287
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 8 months
seen 1 hour 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.


1d
comment What happens when a photon reaches the “edge” of the universe?
@CoilKid: I think (I haven't actually sat down and worked it out) that in a closed universe if you shine a light out from your current position the photons will slow down, come to a stop then start moving back towards you as the recollapse starts. So from your perspective the light does indeed move in a curved path. But this is routine in general relativity, and indeed it's the cause of gravitational lensing. In this case it's the whole universe acting as the lens!
1d
answered FRW metric and its validity througout the age of the universe
2d
comment What happens when a photon reaches the “edge” of the universe?
@CBauer: the views that Neil attributes to Hawking are not mainstream. If there is a Big Crunch (and current evidence suggests the universe will not recollapse) then most of us expect entropy to increase smoothly during the recollapse phase. Time won't run backwards or indeed do anything screwy. See the Wikipedia article on the Big Crunch for more.
2d
comment How to calculate heat generated from cosmic dust in space?
possible duplicate of Would a fast inter-stellar spaceship benefit from an aerodynamic shape?
2d
reviewed Leave Closed What will be the time taken by a stone to reach the ground if it is thrown with velocity $v$?
2d
reviewed Leave Closed Can beamer presentation can be used at APS meetings?
2d
comment Intensity of Brightest Fringe of a multi-slit Diffraction
Possibly, but it can't contain more energy. The integral of the intensity of the central fringe must be less that the integral of the intensity over all the slits that form the diffraction pattern. If it was that would mean there was more energy per second in the central fringe than was passing through the diffraction grating. However it's certainly true that if there are many slits, so a high overall area, the intensity at the central fringe can be higher than the intensity of the light hitting the diffraction grating.
2d
comment Intensity of Brightest Fringe of a multi-slit Diffraction
The integral of the intensity over all the fringes will be equal to the total intensity of the light coming through the slits.
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answered On solving a two lens system
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comment Can time be interacted with?
Zack, it's a good question, but it can't be answered in any useful way without getting into the maths. I dont know of any non-mathematical explanation that isn't ultimately misleading.
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revised What happens when a photon reaches the “edge” of the universe?
Tweak
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comment Can time be interacted with?
The downvote seems harsh. Zack is basically asking what the mechanism of time dilation is, and I suspect that's a question that has puzzled most of us at some point.
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comment Can time be interacted with?
Zack, the question I've linked as a duplicate explains what time dilation is and why it happens. A search of this site for time dilation will find you lots more related questions.
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comment What will be the time taken by a stone to reach the ground if it is thrown with velocity $v$?
Use the SUVAT equation $s = ut + \tfrac{1}{2}at^2$. $u$ is the initial velocity and $a$ is the acceleration due to gravity.
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reviewed No Action Needed Why can a ball tossed up object free fall upwards?
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reviewed Leave Closed How is the method of Lagrange multipliers used for multiple constraints of multiple variables?
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reviewed Leave Closed Complex Quantum Wave
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reviewed Looks OK Is it possible to cut harder material with a less hard material?
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reviewed Close Why can we cycle faster than we can run?
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reviewed Leave Open Fresnel lens magnification, convex divergence