Universal Definition and 488 Threads

I recall reading on this forum that a theorem had been proved to the effect that is there was a effective speed limit c in SR then there would only be one such limit for all relevant phenomena. Is this true and if so can you point me at it as I don't seem to be able to formulate the question...

With NASA defining this equilibrium density at 9.9 x 10<30 gm/cm3, how can an increasingly expanding universe maintain a steady density as it expands?

Could relativistic Doppler, as in measuring the cosmic microwave background's wavelength from all directions, be used to determine one's velocity and direction in space? With maybe a gyroscopic device initialized to some arbitrary x,y,z grid?

So I understand this is probably more contiguous with philosophy than with physics, and there is probably no exact answer to this, but I had a couple of interesting questions relating to planes of reference, keep in mind I am a high school student and possesses very little knowledge of...

Did the universe Absolutely begin?

I have a question on convention regarding the universal law of gravitation formula. Sometimes the distance is represented with the lowercase r and sometimes with the uppercase R. Why is it listed two different ways? I am thinking that r is the total distance and R is the radial distance, no...

I've heard that unlike Special Relativity, General Relativity claims that you can' say any reference frame is better than another frame, including frames in which Newton's Laws don't hold. I've seen debates about this specifically in the context of geo/helio-centrism. From what I understand...

Homework Statement ANY HELP IS WELCOMED[/B] The single moon of an Earth-like planet creates tides on the planet that are slowing the planet’s rotation. The planet’s rate of rotation is decreasing at a rate of 7.00 x 10-7 radians/sec/century. The mass of the planet is 6 x 1024 kg, and its...

Homework Statement The single moon of an Earth-like planet creates tides on the planet that are slowing the planet’s rotation. The planet’s rate of rotation is decreasing at a rate of 7.00 x 10-7 radians/sec/century. The mass of the planet is 6 x 1024 kg, and its diameter is 12,600 km. The...

Given a perfect sphere with the ability to measure any of its diameters at any time, if traveling at relativistic velocities, could I use length-foreshortening to determine my speed and direction?

I'm seriously happy Elon Musk is behind a universal basic income. It's something we desperately need to advance.

Homework Statement I got part A of the problem right. I am stuck on part B. As you can see, they ask for the reactions at B, D and E.[/B]Homework EquationsThe Attempt at a Solution OK, here's the book's the answers: at D, 350N k. At E, -100Nk, and at B -250N k. So, we have a 50Nm torque...

Not resorting to religion, how does apparent ordered structured complexity materialize in the universe? I want to be honest here, so I will let it be known. I'm also interested to know how this forum, which is highly censored main stream view only, deals with a topic mainstream has little to...

No matter what direction I point my super duper telescope, I will observe galaxies that are barely 500 million years old in every direction some of them being located 12+ billion light years away. So 2 galaxies on opposite side of the Earth should be twice 12+ billion light years apart. In other...

What are good books in universal algebra, given that I have a background in Herstein (Topics in Algebra), Hubbard/Hubbard, Engelking (Topology), and Dugundji (Topology)? I am currently reading Hungerford, and I found a field called universal algebra while searching internet for some concepts...

Homework Statement [/B] Two 100-kg thrill seekers are diving into a neutron star. The neutron star’s mass is 1.1 solar masses and its radius is 12.0 km. For safety, they tie themselves together with a cord 10m long, so that as Melvin reaches the surface of the neutron star, Fred is 10.0 m...

Often, in the study of algebraic objects certain things (like tensor products) are often defined primarily in terms of an universal mapping property. When one is used to "concrete objects" one can calculate with, this often comes as a shock to the system. One feels as if one is spinning...

How significant is this development of a 5 qubit computer by IBM? See, "IBM invites users to test its quantum computer" at http://phys.org/news/2016-05-ibm-users-quantum.html "How IBM’s new five-qubit universal quantum computer works" at...

I am wondering if things can be objective but not universal.

Homework Statement Show that the rate of change of the free-fall acceleration with vertical position near the Earth's surface is \frac{d}{dr} [g] = -\frac{2GM_E}{R_E^3} Assuming h is small in comparison to the radius of the Earth, show that the difference in free-fall acceleration between...

Homework Statement This problem only requires to find h, but I want to make sure that I also found Me and g correctly. Starting with Newton's Law of Gravitation, determine the height h one person has to go from the surface of the Earth in order for that person's weight to be reduced to...

Using the electric field as an example: Does modern physics see the electric field as one universal field covering the entire universe or because of the vast distances involved it can be several?

Hello all, i have been tinkering with some series universal motors out of a vacuum cleaner and circular saws and would like some insight into the mechanism that determines directionality of the motor. Unlike dc motors i have used in the past, changing the wiring to the armature in relation to...

Homework Statement Choose two masses and vary their separation, measuring the force between them each time. Plot a straight line graph and use the gradient to estimate the universal gravitational constant. Include uncertainties in the results and express values with the appropriate number of...

Homework Statement Express the following statement using only quantifiers. (You may only use the set of Real and Natural Numbers) 1. There is no largest irrational number. Homework Equations ##\forall=## for all ##\exists##=there exists The Attempt at a Solution I express the existence of...

Homework Statement http://[url=http://postimg.org/image/f7e6kp0xv/][PLAIN]http://s21.postimg.org/f7e6kp0xv/image.jpg Homework Equations Kepler's laws The Attempt at a Solution I thought the answer will be C : I and II But the solution written (it was my friends book) is B, which is correct?

I am doing an Astronomy GCSE. I have to work out the orbital period for a satellite. I have got quite far with it, but I am really stuck. I have spent hours at it! This is the question:- A space laboratory is in circular orbit around the Earth at a distance of 6000km from the Earth's centre; its...

Are the cosmological constant and the universal constant essentially the same?

Homework Statement http://prntscr.com/9huihp Given, Mass of the Earth = 6*1024 Mass of Satellite = 45 kg Radius of Satellite's orbit = 4.2*107 G = 6.67*10-11 Find the velocity of the satellite. Homework Equations Gravitational Force Fg = (G*Me*Ms)/(Rs2) Newton's second law: Fg = Ms*a where a...

Does anyone know a manufacturer or supplier of joints like the one shown here: https://grabcad.com/library/universal-joint-graphite-bushes The main feature I'm looking for is the counterbores at the ends that allow mounting to a flat plate. Almost all the ones I've found are made for...

I'm alittle confused, is it saying that all the fundamental particles in the universe are really just one wave function?

Well we have been talking about the size of the universe and em waves all day and it's lead me to ask this. EM waves can no longer effect us from passed the CEH line right . And if gravity also travels at the speed of light a does this mean that once these galaxies are gone passed the CEH they...

Homework Statement Coproducts exist in Grp. This starts on page 71. of his Algebra. Homework Equations [/B] Allow me to present the proof in it's entirety, modified only where it's convenient or necessary for TeXing it. I've underlined areas where I have issues and bold bracketed off my...

The speed of light is the universal speed limit and absolute zero is the universal temperature limit. Are there any other universal limits like this in nature?

Homework Statement A piece of an empty rocket booster fuel tank (mass 45 kg) is ejected from a rocket that is 2100 km above the Earth's surface. It is traveling upwards at 4.5km/s at this time. a) what is the total energy of the booster at this time? b) Will it return to earth? Homework...

I am reading Paolo Aluffi's book, Algebra: Chapter 0. I am currently focused on Chapter II, Section 3: The Category Grp. I need some help in getting started on Problem 3.3 in this section. Problem 3.3 at the end of Chapter III, Section 3 reads as...

Hey all, I was reading up on some discoveries made in cosmology. http://iopscience.iop.org/1538-3881/149/4/137/ This could easily be due to observational error, but I was wondering whether something such as this is possible in our current models of expansion and dark energy without having to...

Does Universe Spacetime have clock of it's own? A period?

Hi everyone! I am new to cosmology and have come across this unbelieving interesting field quite recently ( after reading 'A Brief History of Time' to be honest ). This is my first post in PF. Hubble first discover that the universe is expanding with non-constant, accelerating velocity. Also...

Hey all, I have been put in charge of developing my company's research and development "lab" and I am currently looking for some testing equipment to buy. My background is in civil engineering, however I did do a small amount of material testing in school, and I'm familiar with the concepts...

Homework Statement The Earth has a mass of 5.98 x 1024 kg and the moon has a mass of 7.35 x 1024 kg. The distance from the centre of the Moon to the centre of the Earth is 3.84 x 108 m. A rocket with a total mass of 1200 kg is 3.0 x 108 m from the centre of the Earth and directly in between the...

Firstly, I'd be happy to be corrected if I'm not using the right wording or just plain incorrect with my approach. Is it practical to suggest that units of one measurement system could possibly represent the measurement of things not only at the macro level, but represent particles with and...

(All vector spaces are over a fixed field $F$). Universal Property of Tensor Product. Given two finite dimensional vector spaces $V$ and $W$, the tensor product of $V$ and $W$ is a vector space $V\otimes W$, along with a multilinear map $\pi:V\times W\to V\otimes W$ such that whenever there is...

Hi guys, got a question that's got me stumped. Not looking for the answer as I'd prefer to work it out myself, just a nudge or a pointer in the right direction. I'm being asked to prove if an XOR gate can be classed as universal (like the NAND & NOR gates are), but not sure how to go about it. I...

Homework Statement I am currently reading about Newton's Law of Universal Gravitation and I am so confused as to why there is a negative sign in front of the equation Fg = (G* m1m2)/r^2. Homework Equations Fg = (G* m1m2)/r^2 There is a vector form of the magnitude of the gravitational force...

Homework Statement Three point particles are fixed in place in the xy plane. The three partiles sit on the corners of an equilateral triangle with sides of length a = 2.50 mm. Particle 1 has a mass m1 = 12.0 kg, particle 2 has a mass m2 = 18.0 kg, and particle 3 has a mass m3 = 15.0 kg. 1...

I'm curious as to what he did to figure it out *Newton, sorry

Homework Statement What is the gravitational force between Earth and the sun if the Earth has a mass of 5.98 x 10^24 and the sun has a mass of 1.99 x 10^30. The r is (1.5 x 10^11)^2[/B]Homework Equations F=(Gm1m2)/r^2 G= 6.67 x 10^-11 N m^2 /kg^2 ( note that this is a constant)[/B]The...

If a bullet is fired vertically from the surface of the Earth with initial velocity v = 10 km / s, ignoring air resistance, at which distance h from the center of the Earth would arrive? (The radius of the Earth is RT = 6360 km, and the mass of the Earth MT = 5.98x10^24 kg) I used the formula...

I am trying to understand in more detail the answer to: http://math.stackexchange.com/questions/673187/universal-cover-of-a-surface-with-boundary It is mentioned that the universal cover of a hyperbolic surface ##S## with geodesic boundary is a closed disk ##D^2## with a Cantor set removed from...