LaurieAG

How do things work out if the spaceship travels in a circle at a constant velocity?

I didn't mean to put you off euclidean construction for fun diversion and learning - but I think in mathematical terms it is a little bit like latin; useful, a great foundation, the basis of many great past discoveries, but in the end a dead language.

Why bother about the latin when you can read the english translations.

I have been reading "On the Shoulders of Giants", edited, with commentary by Stephen Hawking and it contains 'On the Revolutions of Heavenly Spheres' by Nicolaus Copernicus, 'Dialogues Concerning Two Sciences' by Galieo Galilei, 'Harmony of the World, book Five' by Johannes Kepler, 'Principia' by Isaac Newton and selections from Albert Einstein's papers on relativity.

They all invested substantial effort in developing their ideas geometrically before finalising the maths.

Incidentally, whenever I read Einstein's 1905 SR paper I get the distinct impression that he intended it to allow the true beauty of relativity to shine through a window onto the euclidean world. Unfortunately somebody put up the shutters.

A blend was made from types of tea, X and Y, so that the mixure contains 20% of type X. If the quantity of X is doubled, find the percentage of type X in the new blend, given that;

(i) the same quantity of Y was used;

(ii) the total quantity of the mixure was unaltered.

 

How can I tackle this?

(i) 20 x + 80 y + 20 x gives x = 40, y = 80, total = 120, x = 1/3 of total and y = 2/3 of total

(ii) 20 x + (80 - 20) y + 20 x gives x = 40, y = 60, total = 100, x = 2/5 of total and y = 3/5 of total

If you look at this image, for example, the red band across the middle is the emissions from our galaxy. Earth's axis is not aligned with the galaxy's axis. I think it is *roughly* 90 degrees away.

 

http://commons.wikimedia.org/wiki/File:WMAP_2008_41GHz.png

More like somewhere around 60 +/- 1.5 degrees.

http://en.wikipedia.org/wiki/Solar_System

Orbit about Galactic Center

Invariable-to-galactic plane inclination

60.19°8 (ecliptic)

http://en.wikipedia.org/wiki/Invariable_plane

The invariable plane of a planetary system, also called Laplace's invariable plane, is the plane passing through its barycenter(center of mass) perpendicular to its angular momentum vector. In the Solar System, about 98% of this effect is contributed by the orbital angular momenta of the four jovian planets (Jupiter, Saturn, Uranus, and Neptune). The invariable plane is within 0.5° of the orbital plane of Jupiter,^[1] and may be regarded as the weighted average of all planetary orbital and rotational planes.

http://en.wikipedia.org/wiki/Earth

However, there is no reason to think that there is any such absolute frame, is there?

Apart from inclusion of a common reference frame to anchor the practical application of the theory.

Does our system of dates have an 'absolute' frame of reference, or how about our time or latitude or longitude?

Just because their start points are arbitrary doesn't mean that they are not a form of 'absolute' reference frame for most practical intents and purposes.

Meh, It's clear from Deuteronomy 20 that these commands are not general but specific. God is adressing particular people in particular place and time, regarding treatment of specific peoples. No one can use these passages as present day imperatives... and no one does.

From a western perspective alone the ancient Greeks and Romans used the method prescribed and, just to mention a few examples, several Irish towns suffered a similar fate in the 17th century at the hands of puritans. In the 19th century the defenders of 'the Alamo' were on the receiving end of 'the treatment'. Just because it is regarded as a war crime now does not mean that it does not occur. Also (fortunately) there is little archaeological evidence in support of the events as given.

BTW, I write 'god' as I am not particularly religious and do not wish to project any potential bias that could interfere with analysis of the issue at hand. While I can understand why breaking down the process to core motivations of key players might help I cannot fathom why anybody would consider 'commands from a god' as a valid defense for any current or ancient war atrocity.

Why would anybody think that cutting the grass (while also fertilizing the soil with blood and bone) would lead to anything but another bumper crop of grass that has to be cut?

Option B is False computers cannot understand intermediate languages they only understand pure machine language.

That only works if machine code is not a low level language.

Also, the two types of errors are syntax errors and logic errors.

D has some truth in it because it says interpreters will find errors in source code befo they are run but the second one im unsure because when i compile a program with syntax error it throws and error, but it says execute source code which is misleading.

So you already know that compilers, not interpreters, find errors in source code before they are run and should therefore know D's correctness status.

What are your reasons for classifying the others correctness?

The main problem with B and C is that they do not compare the first element with the last element and B also does not increment the counter. A is the option where all elements are compared with the last element. The FOR and WHILE loops operate differently as the FOR has the counter increment embedded.

If you step through each option for each increment and write down what each of the variables are for each of the cycles you will be able to see the differences.

KayS, please post your results for 3 cycles of B, C and D.

A     i     j    arr(i)   arr(j)
      1     5      m        m
      2     5      a        m
      3     5      d        m

For the first element both B and C test arr(i) or arr(index), where i or index = 1 (i.e. element 'm'), against len(arr) -1 (i.e. 5-1 = 4 or element 'a'), which is the second last element not the last element.

A only tests all elements against the last element, B and C test the first element against the second last element while D tests all the elements correctly.

 

No, that's not quite it. Dark matter is matter we can detect only via gravitational effects.

That's interesting as I came across the following on the Wikipedia Fictitious Force page.

http://en.wikipedia.org/wiki/Ficticious_Force#Gravity_as_a_fictitious_force

 

Gravity as a fictitious force

The notion of "fictitious force" comes up in general relativity.^[15][16] All fictitious forces are proportional to the mass of the object upon which they act, which is also true forgravity.^[17] This led Albert Einstein to wonder whether gravity was a fictitious force as well. He noted that a freefalling observer in a closed box would not be able to detect the force of gravity; hence, freefalling reference frames are equivalent to an inertial reference frame (the equivalence principle). Following up on this insight, Einstein was able to formulate a theory with gravity as a fictitious force; attributing the apparent acceleration of gravity to the curvature of spacetime. This idea underlies Einstein's theory of general relativity.

It's a variation of the Liars Paradox.

http://en.wikipedia.org/wiki/Liar_paradox

http://en.wikipedia.org/wiki/G%C3%B6del's_incompleteness_theorems#Relation_to_the_liar_paradox

It's best if you use the full Editor and click "Preview Post" before adding your reply.

Based on some new findings I think yes the weather will be affected by changes in the solar wind.

 

Evidence for solar wind modulation of lightning

It looks like lightning isn't the only thing modulated by changes in the solar wind.

Summary: The decay of a satellite from low earth orbit is of interest to many people. The drag force that such a

satellite experiences is due to its interaction with the few air molecules that are present at these altitudes. The density

of the atmosphere at LEO heights is controlled by solar X-ray flux and particle precipitation from the magnetosphere

and so varies with the current space weather conditions.

http://www.ips.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/SatelliteOrbitalDecayCalculations.pdf

Thank you LaurieAG for that link but is that available in India? As I am an Indian.

Hi Devansh, the courses are available online and there are SANS training centers in India. http://www.sans.org/security-training/by-location/all

Flexible Learning Options

All of the incorporated SANS courses may be taken either live at a SANS event or online from home or work. Though each individual course must be completed typically within four months of its start date, the entire program may be completed over approximately 18-24 months. This allows for any necessary breaks between courses so you may optimally schedule them to fit your work schedule and personal life.

What are the courses available in ethical hacking?

Here are some https://www.sans.edu/academics/certificates

Yes that is x^2

 

But one question, what is this that you are using --> +/-

 

In your example here, where did the 100 come from??

it looks like 10^2/2 = 1/2 = .5

 

(6 +/- SQRT(36-100))/2 = (6 +/- SQRT(-1)*SQRT(64))/2 = 3 +/- 4*SQRT(-1) = 3 +/- 4i

The +/- is just part of the standard quadratic formula. http://en.wikipedia.org/wiki/Quadratic_equation#Quadratic_formula_and_its_derivation

The 100 comes from 4 * a * c = 4 * 1 * 25 = 100 and the 36 comes from b^2 = -6 * -6 = 36 so SQRT(b^2 - 4 * a * c) = SQRT(-64) = SQRT(64 * -1) = SQRT(64) * SQRT(-1) = 8 * SQRT(-1) = 8i. As -b = 6 and 2 * a = 2 * 1 = 2 so the final equation is (6 +/- 8i)/2 = 3 +/- 4i.

It might look like 10^2/2 = 100/2 = 50 if you ignored the bracketing but you could only get .5 if you ignored the bracketing and redefined 10^2 or 2.

The quadratic equation x2 -6x + 25 = 0 where the 2 roots are 3 + 4i and 3 - 4i

I gather that's x^2 not x2. Work towards the roots and you will see where the i comes from.

The roots of a quadratic equation in the form of a*x^2 + b*x^1 + c*x^0 = 0 equal (-b +/- SQRT(b^2 -4*a*c))/2a.

With a = 1, b = -6 and c = 25 the roots are (6 +/- SQRT(36-100))/2 = (6 +/- SQRT(-1)*SQRT(64))/2 = 3 +/- 4*SQRT(-1) = 3 +/- 4i

Also, the roots of a quadratic equation in this form are the point(s) where the plot of the quadratic function crosses the x axis i.e. where y = 0.

I'm currently reading 'On The Shoulders of Giants', with some commentary by Stephen Hawking.

It contains English translations of 'On the Revolution of Heavenly Spheres' by Nicolaus Copernicus, Galileo Galilei's 'Dialogues Concerning Two Sciences', 'Harmonies of the World (Book five)' by Johannes Kepler, Isaac Newtons 'Principa Mathematica' and selected relativity papers by Albert Einstein.

Case in point, when CERN results showed neutrinos traveling slightly faster than light (something that is supposed to be impossible), their response was "Hey guys, we got a weird result. Could somebody check our work and see if we're doing something wrong?" while all the headlines were screaming "Einstein was Wrong!"

 

The former is how an actual scientist sounds. If you read something along the lines of the latter, it's a red flag that whatever you are reading probably wasn't written by an actual scientist.

 

(Incidentally, someone did eventually discover what was wrong at CERN, which is precisely why scientists don't go spouting off about overturning all of physics at the first sign of discrepancy).

I never thought that any of the multitude of dedicated physicists, engineers and technicians involved with the project had made any real error so I looked at the paper to see where an error of the magnitude of the discrepancy could possibly slip through during the entire process. I thought that the way the error rates in the calibration were broken down was unusual and could mask a cumulative packet/basket count error over the whole calibration cycle which could equal the main error. With high speed electronics you trigger the packet counter when the start of the packet arrives and increment the counter as when each new packet arrives. The only problem with using this method is if you fail to realise that the count that results from the end of the last calibration packet is one greater than the actual number of packets received. All I know is that they released the recalibration figures with much smaller packet sizes and the errors were exactly the same as for the original calibration figures, just before they found the 'loose wire'.

http://www.sfgate.com/bayarea/article/NASA-photo-on-strange-light-on-Mars-has-UFO-buffs-5387337.php

Maybe NASA noticed that the first and third images are from different perspectives (and even different days?) and the 'light's location remains consistent so they ruled out rogue wandering pixels and looked for other alternatives.

"One possibility," Webster said, "is that the light is the glint from a rock surface reflecting the sun. When these images were taken each day, the sun was in the same direction as the bright spot, west-northwest from the rover, and relatively low in the sky.

While the above images represent what the paths would look like if the sources were rotating at c the distance traveled to the observer equals c/v * 2 * Pi * r where v is the angular velocity of the source. i.e. If the source had an angular velocity of 0.5 c the distance traveled would be c/0.5c = 2 times longer than at c.

I posted the following thread about what the apparent light paths from sources rotating around a center of mass would look like geometrically.

http://www.scienceforums.net/topic/75390-apparent-red-shift-in-a-discrete-newtonian-frame/

It is well known that Newton worked out all of his proofs geometrically first before identifying the underlying mathematics and Einsteins papers progress from geometric considerations as well. When did this method become passe?