vdondeti
Joined 16 years ago
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Comment · 12 years ago
Comment · 13 years ago
I took another approach to this. I have been meaning to post it to HN for a while, though it is still a little raw. I call it geokode - https://geokode.com - it is meant to be like bitly for location. You can essentially choose what your url should be for any location. This makes it very user-friendly and you can also brand your location link. Currently, you can only use English characters and numbers. I have pre-populated it with some entries (see examples below), but the goal is to get users to create their own 'geokodes' as I like to call them. I am also working on a API to make the location data available once the geokode is provided. You can even link a geokode to GPS coordinates, which will be especially useful in countries where addresses are not simple. Obviously, the site needs a lot more polish, but let me know what you think. It is currently free to register a geokode - I have to update the demo video.
Some examples to highlight use cases:
https://geokode.com/*abckitchen
https://geokode.com/*joneswedding
https://geokode.com/*dormroomfundhq
Also, I will be at TC Disrupt in NY today in the Startup Alley in the Mobile category. Feel free to come by.
Comment · 13 years ago
Well, it depends on how far back you want to go. All elements come from nuclear reactions in suns/stars which occur partly due to gravity. Some elements are unstable making them radioactive, some of which we use for nuclear fission. Big chunks of stars form planets and the associated geothermal energy. So, solar reactions and gravity account for all energy either directly or indirectly. Gravity is also the cause of tidal energy.
Comment · 14 years ago
I assume you mean a demo video and are looking for something affordable: http://demogirl.com/
Comment · 14 years ago
This is sort of a tangent, but why don't more people use Amazon FPS. I know it requires that the customer have an Amazon account (which many customers do have), but it is supported in many countries. You can at least have it has one of the payment options.
Comment · 14 years ago
The uncertainty principle does not state that you can't measure both position and momentum; it states that you can't measure both accurately. So, as your accuracy of one increases, the accuracy of measurement of the other decreases.
Some pertinent quotes:
http://todayinsci.com/QuotationsCategories/M_Cat/Measurement...
On careful examination the physicist finds that in the sense in which he uses language no meaning at all can be attached to a physical concept which cannot ultimately be described in terms of some sort of measurement. A body has position only in so far as its position can be measured; if a position cannot in principle be measured, the concept of position applied to the body is meaningless, or in other words, a position of the body does not exist. Hence if both the position and velocity of electron cannot in principle be measured, the electron cannot have the same position and velocity; position and velocity as expressions of properties which an electron can simultaneously have are meaningless. — Percy W. Bridgman Reflections of a Physicist (1950), 90.
The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... — Michio Kaku Quoted in Nina L. Diamond, Voices of Truth (2000), 333-334.
Comment · 14 years ago
I think you missed the quote monjaro posted which I responded to "According to the generalized uncertainty principle, the Planck length is in principle, within a factor of order unity, the shortest measurable length - and no improvements in measurement instruments could change that."
i.e. Planck lengths is the shortest measurable length and thus you can't measure anything of smaller length, and so the smallest length any object can have is the Planck length.
Comment · 14 years ago
What I stated above was an interpretation of the statement you cited. In essence, I (and many others) would posit that if you can't measure it, then you can never know it exists. So, the smallest length any object can have is the Planck length. And then I believe, that since you can't measure sub Planck lengths, everything you measure must be an integral number of Planck lengths. Obviously, one is free to disagree with this interpretation.
Comment · 14 years ago
Fair point. Depending on how you define it, all charges are an integral multiple of e or e/3 (see below). Either way, the relevant point to this discussion is that charge is quantized/discrete.
As for the Fractional quantum Hall effect, based on a quick glance, it seems that thus far only quasiparticees with charge e/3 have been discovered. So, while the theory could be correct, we will have wait and see if the other predicted fractional charges are detected.
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From the Quark wikipedia page you cited: What is the quantum of charge? All known elementary particles, including quarks, have charges that are integer multiples of 1⁄3 e. Therefore, one can say that the "quantum of charge" is 1⁄3 e. In this case, one says that the "elementary charge" is three times as large as the "quantum of charge". On the other hand, all isolatable particles have charges that are integer multiples of e. (Quarks cannot be isolated, except in combinations like protons that have total charges that are integer multiples of e.) Therefore, one can say that the "quantum of charge" is e, with the proviso that quarks are not to be included. In this case, "elementary charge" would be synonymous with the "quantum of charge".
Comment · 14 years ago
From my understanding, the Planck length is the smallest length there can be, and every other length has to be an exact integral multiple of the Planck length [1]. I believe the same applies to the other Planck units [2]- they are fundamental units. Similarly, every charge has to be an exact integral multiple of the charge of the electron. These fundamental units seem to to indicate that our universe is not continuous, but quantized/discrete. With that said, there are some theories stating that these fundamental units only apply to our universe (and even in our own universe, the fundamental units may change over long periods of time), and that other universes may have different fundamental units. So depending on how you define the universe, the answer to whether the universe is continuous or discrete could change.
[1] http://en.wikipedia.org/wiki/Planck_length [2] http://en.wikipedia.org/wiki/Planck_units
PDF: http://jech.bmj.com/content/early/2014/03/03/jech-2013-20350...