Tag Info

Hot answers tagged

25

Most of the reproduction of results in particle physics comes from two sources: Competing experiments running nearly simultaneously. In this case both ATLAS and CMS got comparable results. Now, they are both using the beam from the LHC, so how do we know the beam is properly understood? Because while they were commissioning those machines they reproduced ...


11

Nobody ever tried with LHC, but here is Anatoli Bugorski: http://en.wikipedia.org/wiki/Anatoli_Bugorski Given the damage he received with a beam of 70 GeV protons (intensity ~10^13) you can probably imagine the damage you would receive from 6500 GeV protons (intensity ~10^32). For more info about the "danger" of the LHC beams, I suggest you read about the ...


5

At present for physics research, a phenomenologist is a theoretical physicist who is well grounded in the current physical theories and at the same time understands the data and can create detailed theoretical models that can predict the behavior of future experiments. In this context, phenomenology is the study of the way current theories fit the data and ...


4

The LHC luminosity is $4.6\cdot 10^{32} /cm^2/s$ (reference) - that is an incredibly intense beam, but there is a finite number of protons going around. The thing that really matters though is the number of protons in the beam at one time: there are 2808 bunches in the beam (http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/collisions.htm) with a ...


4

There isn't an answer to your question because a varying magnetic field doesn't really produce an electric field (and a varying electric field doesn't really produce a magnetic field). Time varying magnetic and electric fields are associated, but it is misleading to imagine that one causes the other. Even physicists tend to instinctively think of electric ...


3

When they need to empty the beam of particles they are directed into a "beam dump" target Absorption Each beam dump absorber consists of a 7m long segmented carbon cylinder of 700mm diameter, contained in a steel cylinder, comprising the dump core (TDE). This is water cooled, and surrounded by about 750 tonnes of concrete and iron shielding. ...


3

Technically this question is off topic and would belong in an astronomy SE, but the answers you probably are seeking are terrestrial or terran depending on whether it is a person or an object. Terran has been sorta scooped up by the Starcraft community though so terrestrial is used in almost all cases to my knowledge.


3

cms and kgs are wrong. The SI units are abbreviations which are also used in the plural. You will write 2.6 m/s or 1 m/s, but say "2.6 meters per second" or "1 meter per second" respectively. Keep in mind the SI units are also used in tons of other languages that do not form the plural by attaching an -s. The units look the same in those languages. (e.g. ...


3

Relativists tend to use the proper time, $d\tau$, and the proper distance, $ds$, interchangably. If you're working with proper time you'd expect the equation for it to look like: $$ d\tau^2 = dt^2 + \text{other terms} $$ while if you're working with proper distance you expect: $$ ds^2 = dx^2 + dy^2 + dz^2 + \text{other terms} $$ The sign problem comes ...


2

It comes from S matrix theory, long before quarks were imagined, S,T and U characterize the type of exchange in the Feynman diagrams entering the S matrix calculation, and they are called Mandelstam variables. s channel-------------------------- t channel------------------------u channel duality meant that the sums could be done either in S ...


2

Just a start... there are others on this site that know much more about these things (David Hammen, are you reading this?). For any rocket to gain speed, it needs to expel some material - and the faster the material is expelled, the more speed the rocket gains. There is a "rocket equation" that shows the velocity you can reach depends directly on the exit ...


2

Ion propulsion rockets are just that, rockets. They're just a different kind of rocket that the typical chemical propulsion rocket. Chemical propulsion uses chemical reactions and thermodynamics to create a high velocity exhaust, and hence thrust. Ion propulsion works by ionizing a gas (typically a gas with a high molecular mass such as xenon), accelerating ...


2

This is a classic misconception that most people share at some point in their lives. For centuries, we struggled to understand this point. For example, the famous Aristotle expresses your misconception that: continuation of motion depends on continued action of a force i.e. you see a ball moving upwards, and think that there must always be a force ...


2

The first difficulty in making a measurement of this kind is, of course, to build the facility. However once you solve all the engineering issues and put your machines in place, the experiment flow is pretty straightforward: you run and you get the data, in principle without any human intervention. Up to here you just let Nature do its work in a pretty ...


2

A firm understanding of classical physics is essential. This means understanding the qualitative and quantitative aspects of: 1) Newton's three laws of motion (Kinematic and Dynamic perspective) 2) Rotational motion dynamics 3) Electromagnetism 4) Newtonian mechanics (Newtonian gravity) 5) Principle of superposition and waves 6) Classical thermal ...


1

The question is "how much scientific confidence can we put into things like the mass of the Higgs". Well, what is the level of certainty? According to CERN it is around 7 sigma. In simple terms at 7 sigma, both the CMS and ATLAS teams are reporting that there’s only a 0.0000000001% chance that they haven’t found a Higgs-like particle.


1

Do we have any similar experiments where we confirm a theory without being able to reproduce those results? Not today, but once we know how it works we can repeat it on a smaller and cheaper scale. The first electronic calculators required an entire floor, consumed staggering amounts of power and cost a budget-busting amount of money. Today, my phone ...


1

There would be a big difference between documenting the advance of truly fundamental physics, and documenting the advance of every investigation, discovery and idea which might count as physics. The fundamental advances are documented in places like encyclopedias, textbooks, and the list of Nobel Prize winners. Perhaps the closest thing to a central, ...


1

Once you release the ball, you are not applying a force to it; it is freely falling (despite its upward motion). The only force acting on it is the gravitational force, pulling it downwards (which is why it slows down and stops momentarily at the apex, before coming back down). See also the related question When a ball is tossed straight up, does it ...


1

I think Terran is as good a word as any, as is Geo. Thinking of terms where Solar or Lunar are used. Solar Gravity, Lunar Gravity, Terran Gravity, or Earth's Gravity. Solar Magnetic Field, Lunar Magnetic Field (which, I'm not sure there is one), Earth's Magnetic Field or Geo-Magnetic Field is also used. Earth's, Geo or Terran are the best 3 options I ...


1

A common misunderstanding of quantum mechanics is the belief that EVERYTHING in the world is quantized, but this is simply not true. For example the position of a free particle is not quantized but may take on any value.


1

It appears that you are looking for the "big picture" of quantum mechanics, not the ability to do extensive calculations. For this, in my opinion, you should start by understanding observables with two possible values (like spin in a particular direction, which is either up or down), rather than observables with infinitely many possible values (like ...


1

The relativity of simultaneity is not an axiom, the axiom is that the light velocity is the same in every frame of coordinates. A spot of light travels at the same velocity, c with respect to you, and at the same velocity $c$ with respect to a traveler traveling with respect to you at an arbitrary velocity. So, assume that you send two spots of light to ...


1

The name T-duality stands for Target-space duality, see e.g. this preprint.


1

One never pluralizes unit abbreviations. Your link goes to the BIPM, the body responsible for maintaining the definitions of the international system of units, and is authoritative. The folks at NIST agree and address most of your questions. I would say The pipe is 0.75 m long. or The pipe is 75 centimeters long. or even The pipe is ...



Only top voted, non community-wiki answers of a minimum length are eligible