Tag Info

4

It is rather the other way around: our understanding of physics has enabled us to build GPS systems in the first place. It is correct however that GPS was direct confirmation of not only the theory of special relativity, but also of general relativity. Neglecting the time dilation from the difference in gravitational fields between the satellite's position ...

8

Galileo was the first to observed the phases of Venus, also here, which he was able to do by his telescope, around 1610. It was the phases of Venus as well as observing Jupiter's moons orbiting Jupiter, that, to Galileo, confirmed without any question that Copernicus' model was the correct one and planets orbited the sun and moons orbited planets. Galileo'...

25

According to the caption for that picture on the same Wikipedia article, it is Francesco Fontana’s drawing of the supposed satellite(s) of Venus. Woodcuts from Fontana’s work (1646). The fringes of light around Venus are produced by optical effects.$^1$ Fontana lived from around 1580 to around 1656. He was an Italian lawyer at the University of Naples ...

16

Generally speaking, Venus is rarely a full disk, because it's inwards from the Earth's orbit, so it displays a full cycle of phases. Mostly, it looks like this: Image source Thus, it's not surprising that Fontana would depict it like that, since most of the time Venus appears partially full or as a crescent. Moreover, the only times when Venus appears ...

2

Conjecture: The distance to the moon was approximately known by astronomers in Newton's days. Once you know the orbital radius and period, a simple diagram shows you how much the moon "falls". When angle $q$ is small, the distance $d$ is calculated from $$\frac{d}{v~t}= \frac{v~t}{R}\\ d=\frac{v^2 t^2}{R}$$ Note - interesting details on this ...

0

Good point, What Collier should be saying is: By assuming his own law to be true, and given what we know today, Newtons might could have reckoned that the Moon actually ‘falls’ not 5 m, but 1.37 mm (0.00137 m or about one sixteenth of an inch) below a straight line trajectory in 1 second. It wasn't until centuries later than anyone verified this ...

3

The most famous "terrestrial" experiment that I know of was the measurement of the speed of sound in Nevile's Court in Trinity College, Cambridge. As the tour guides will tell you, Newton stomped his foot and listened for the echo from the wall on the opposite end of the North Cloister. He timed the echo by making a (short) pendulum, and adjusting the length ...

-1

According to me positive charge is present in nucleus so it will attract towards negative charge and -charge is present outward nucleus so attraction is radially outward.

1

There are several examples of fields in physics which don't require calculus and were born far before its invention. For example: Geometric Optics: some of the laws governing light propagation were formulated by ancient Greeks. Catoptrics (from the Greek κατοπτρικός, "specular") has been studied by Euclid (350 BC) and Hero of Alexandria (10-70 AD). Statics:...

4

One very popular view (as espoused by Max Tegmark) is that (quoting count_to_10) : math works because the universe is based on math http://www.scientificamerican.com/article/is-the-universe-made-of-math-excerpt/ https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis Such a view was common from the time of Pythagoras, through to Kepler and ...

1

Ether theories did not yield consistent results, and they were not complying with experimental results. In this situation, Einstein presented a theory which allied the relativity principle with the postulate of the constancy of light. The price for this solution (that nobody dared to pay before him) was the abandon of the absoluteness of simultaneity of ...

6

Initially, when first glass rods were systematically being rubbed, the "charging" phenomena was observed. The electric charges were hypothesized to be positive and negative, and the pioneer (Franklin? forgot the name...) pretty much arbitrarily decided to call one positive and the other negative. Further experiments helped him deduce that two like charges ...

16

The Hall Effect shows that negative charge is moving. In the Hall effect, one passes a current through a wide strip of metal exposed to a perpendicular magnetic field. If positive charges moved, we'd expect the positive charges to be travelling in the same direction as $\vec{I}$, and the magnetic force $q\vec{v}\times\vec{B}$ would be to the right. Thus, ...

11

Physics's don't know that only negatively-charged particles move. We can create ion currents on demand in many environments. We do know that the current flowing in a metal wire is negatively charged particles in motion. As for how to determine that, you do a Hall effect measurement. The measurement works by subjecting a current in a relatively wide bar to ...

0

Einstein, when discussing the "asymmetries which do not appear to be inherent in the phenomena," was referring to a particular interpretation of Lorentz's electrodynamics that he learned, during 1896-1900, from an 1894 book by Föppl. See §15.1.6, "Origin of the Asymmetry Pointed Out by Einstein," pp. 264-265 (PDF pp. 284-285) of André K. T. Assis's free ...

0

It isn't the aether that Einstein rejected, but the notion of absolute simultaneity; and this rejection was forced by taking the speed of light as constant from all inertial or stationary frames; and this is a deduction from Maxwells EM theory. Lorentz, I take it, introduced length contraction as a way of making classical mechanics and EM consistent - or ...

2

Note: Following answer is just my humble opinion Galileo is the forefather of the modern physics. He has discovered law of inertia and law of acceleration. It may be worth noting that He was unaware of even very basic mathematics (like fractions). He had shown law of acceleration with the help the water clock and integer numbers. Moreover, Newton has ...

-2

There's a lot of physics which is miles away from calculus but the problem is it's not accurate I think 80-90% of that is totally piece of junk and remaining is way more hard to understand without calculus but if you want you can do it like proof of kinamatical equation can be given simply by calculating area under those graphs but that's lot more hard than ...

7

Infinitesimal calculus was first formulated by Isaac Newton and Gottfried Leibniz in the mid-17th century. By that time, a number of qualitative and quantitative physical laws had been formulated. Here are some examples of the quantitative laws: Dynamics Laws of planetary motion (Kepler) Motion of falling bodies, pendula, projectiles (Galileo, Torricelli) ...

2

Among competing hypotheses, the one with the fewest assumptions should be selected. Some electrified objects repel, some attract. This can be explained by two kinds of charge. Nothing that cannot be explained by two charges can be explained by adding a third kind of charge. So we continue to describe electricity as occurring in two kinds.

5

There are some good answers here, but I think I want to try to abstract Franklin's work a little bit. Because Franklin found just two options - "repel" and "attract", he was forced to consider only two kinds of charges. Consider the experiment, where glass-glass repels, plastic-plastic repels, and glass-plastic attracts. If all glass is the same, the glass ...

25

I agree with DanielSank that the question is asking (wholly, not partly) about the historical development of the concept of electrical charge, not our modern description of it - "how did they know?" not "how can we know?" The latter (answered by dmckee) is the end result of more than two centuries of observation, experiment, theorising and debate, and ...

3

Let's assume we don't know how many types of charges exist. But we know that there are bodies which either attract or repel each other. Now we perform an experiment We find all such bodies that repel each other and put them in separate categories. After extensive experimentation we observe that they only belong to two piles. Furthermore we also observe ...

42

Get together a collection of charges. As many different ways to generate a charge as you can think of. Go ahead and invite your friends so they can think of some more. (As a practical matter you make static charges just before you use them, but still...) Now, test them pair wise to see if they attract or repel one-another. Keep careful records. Find the ...

4

From the outset, there were three theoretical frameworks for QM; the Wave Mechanics of Schroedinger, the Matrix Mechanics of Heisenberg and the the abstract Bra-Ket formalism of Dirac. Its the formalism of Dirac thats standard, and which Dirac himself called Transformation Theory. Weinberg, in his text on QM, briefly goes into how Heisenberg discovered ...

3

Please note that this is not so much an answer as an extended comment. At this website (which is the Google Book website for Contemporary Newtonian Research by Z. Bechler) it says It is well known that Newton became convinced towards the end of his life that electricity played a vital role in the operations of nature. In the famous final paragraph of ...

1

I think you are asking far too much of one book, and your requirements are somewhat contradictory. Books for the layman are not usually "in-depth." It is up to you to define what you consider to be "major" and what topics you would like to read about. If you do not do so, we can only guess. Books on the detailed history of physics usually specialise in ...

0

One book I'd definitely recommend is John Gribbin's The Scientists. While it is a little more biographical, it does include the trial and error, the buildup, etc., as well as the stories of quite a few more obscure scientists that contributed way more than you'd think. His book is also in a narrative format, not an encyclopedic format. John Gribbin's book ...

Top 50 recent answers are included