The result of sampling the property of a system

learn more… | top users | synonyms

0
votes
1answer
105 views

Does one require calculus to work with uncertainities?

I'm very young so know no calculus whatsoever. I want to be able to calculate uncertainties for a Physics course I'm doing online, but I believe you need to have knowledge of differentials to do this ...
3
votes
3answers
466 views

Calculating uncertainties for a final result

Say you are dividing 2 times with uncertainties: $$\frac{t_1}{t_2} ~=~ \frac{0.551s \pm 0.002s}{ 0.712s \pm 0.002s}.$$ After doing the calculations you get: $$\frac{t_1}{t_2} ~=~ 0.774 \pm ...
1
vote
1answer
62 views

How to properly read a measurement result if it is a number?

If the result of a measurement is i.e. $3.2 \pm 0.7$, what is 0.7? At which confidence level we know that the real result is inside of this interval?
2
votes
1answer
189 views

Accuracy of atomic clocks

When you hear about atomic clocks, it's accuracy is described by saying something like, " it neither gains or loses $x/y$th of a second in $z$ years." How is this error calculated? Does an error imply ...
10
votes
4answers
775 views

Energy Measurements in a Two Fermion Double Well System

This question is related but my question here is much more elementary than discussions of the Pauli principle across the universe. There has been a fair amount of discussion around at the moment on ...
2
votes
3answers
1k views

What is the velocity area method for estimating the flow of water?

Can anyone explain to me what the Velocity Area method for measuring river or water flow is? My guess is that the product of the cross sectional area and the velocity of water flowing in a pipe is ...
-1
votes
1answer
112 views

How can constants… change?

I recently noticed that the value of Planck's constant has changed on Wikipedia. The value that I had in mind (from Google), $6.626068\cdot{}10^{-34}\text{J.s}$, has changed to ...
4
votes
3answers
365 views

How Is It Possible To Measure Extreme Temperatures? (>2M Deg)

Linked Article: Fusion: X-ray laser zaps solid to 2 million degrees The quest to create nuclear fusion may have come a step closer when scientists heated solid matter to two million degrees with ...
3
votes
2answers
93 views

How long does it take to weigh an uncooperative mass?

(This is curiosity, not a practical question. It was inspired by standing still for a digital scale, and considering whether it would be possible to make a scale that could handle being jumped on, ...
2
votes
2answers
398 views

Does the measured mass of earth include that of the atmosphere?

Just what the title states please... and perhaps naive too... Wikipedia pegs the mass of our Earth at 5.9722 × 10^24 kg. Does this figure include the mass of the Atmosphere?
1
vote
1answer
118 views

What kind of interactions denote 'observation'?

I'm quite perplexed by the notion of 'observation' in regards to the collapse of a particle's probability wave. Does a particle's wave only collapse when it is involved in a strong interaction (such ...
17
votes
1answer
2k views

How did they measure the speed of light observing Jupiter's moons, centuries ago?

I am interested in the pratical method and I like to discover if it is cheap enough to be done as an experiment in a high school. Thank you.
1
vote
5answers
370 views

Are Uncertainties in Measurements Important?

In the first lecture of MIT's Classical Mechanics Prof. Lewin highlights the importance of uncertainties in measurements by quoting "Any measurements, without the knowledge of uncertainty is ...
5
votes
2answers
150 views

Can quantum measurement process be thought of as a sieve?

Consider an observable represented by the Hermitian operator $$A=\sum_{a'}a' |a'\rangle \langle a'|.$$ As I read on Sakurai's textbook, the process of measuring $A$ throws a system ...
3
votes
1answer
173 views

Distinguishing two quantum states practically

Suppose we have two states $$|x\rangle = 1 |0\rangle + 0 |1\rangle$$ and $$|y\rangle = \sqrt{1-\epsilon^2} |0> + \epsilon |1>$$ where say $\epsilon = 10^{-20}$ Can we distinguish ...
1
vote
1answer
255 views

Measuring a Rod in Motion with two Synchronized Clocks

An explanation of special relativity I'm struggling with, goes like this: A rod traveling by a "stationary" observer has its length measured by use of two stationary synchronized clocks (synchronized ...
1
vote
1answer
280 views

Graphing measurements with uncertainties

I need to draw a graph of measurements of time for a ball to drop on an inclined plane, with error bars, along with lines of best and worst fit. The problem is that I need to do this on the computer ...
3
votes
1answer
396 views

simple test/measurement to quantify water opacity

I am performing some measurements on liquid surfaces and I want to quantify how these mesures depend on the liquid opacity by performing it with different concentrations of colorant. To allow ...
10
votes
1answer
54 views

Why is the measured distance to the Triangulum Galaxy much more uncertain than to the Andromeda Galaxy?

Why is the measured distance uncertainty for M33 (835 ± 105 kiloparsec) six times bigger than the measured distance uncertainty for M31 (778 ± 17 kiloparsec)? They are approximately at the same ...
1
vote
2answers
6k views

Comparing scales of atomic level objects to scales of everyday size objects

I am trying to come up with everyday size objects comparisions of atomic scales items, e.g. if a proton probability cloud was of size basketball how far would the next atoms to it be? reason being is ...
13
votes
1answer
3k views

Home experiments to measure the RPM of a pedestal fan without special equipment?

Is it possible to determine to an approximate degree, the revolutions per minute of a fan, for example a pedesal fan pictured below, without using some electronic/mechanical measuring device? One ...
3
votes
0answers
24 views

Review of Gas Chromatographs?

Could anyone suggest a recent review article or book on gas chromatography instrumentation? My interest is in the devices themselves, rather than using them for a particular application. This ...
4
votes
3answers
404 views

How could a particle be isolated to avoid decoherence?

The question aims to this issue : if there is some technological arrangement (or action) to take over the particle/system in order to keep it in a coherent state, then the field, (force or whatever) ...
6
votes
2answers
973 views

Mass of a galaxy via luminosity

Is there a general formula for calculating the mass of a galaxy, or even a nebula from the luminosity? Or, is there a way of calculating the total mass of a galaxy from its energy output? Is there a ...
2
votes
0answers
142 views

What near-future measurement technique improvements will extend our physical knowledge?

Inspired by the wiki-article on atom-lasers: Another application, which might also benefit from atom lasers, is atom interferometry. In an atom interferometer an atomic wave packet is ...
1
vote
2answers
409 views

Can two entanglement particles satisfy at same time two different wave functions?

The wave function determines the probabilities of an outcome, and the wave function is parameterized "shaped" depending on the measurement set. i.e. two different measurement set would lead to two ...
1
vote
3answers
342 views

How can I measure the physical properties of a metallic string?

Metallic strings exist in different kinds but I would like to measure for a metallic string: the section/geometry along its length, to a precision of 1/100 mm its elongation when a tension is ...
2
votes
2answers
843 views

Can you use a laser to measure the speed of light with a rotating mirror?

I have learned that the classical measurement of the speed of light with a rotating mirror does not work with a laser (as opposed to, say, a mercury-vapor lamp). Can you tell me if and how coherency ...
3
votes
1answer
445 views

Measuring the magnitude of the magnetic field of a single electron due to its spin

Is it possible to measure the magnitude of the magnetic field of a single electron due to its spin? The electron's intrinsic magnetic field is not dependent upon the amount of energy it has does it? ...
3
votes
3answers
266 views

Knowing when wavefunction collapses

So I learned that after a measurement of, lets say the position of the wavefunction of a particle is made, if another measurement of the position of the particle is made right away, you should get the ...
8
votes
4answers
2k views

Measuring the spin of a single electron

Is it possible to measure the spin of a single electron? What papers have been published on answering this question? Would the measurement require a super sensitive SQUID, Superconductive Quantum ...
3
votes
2answers
2k views

Measuring acceleration of earth due to its fall around the sun

Every orbiting of a satellite around a mass is nothing else but a constant fall - and therefore acceleration - towards this mass. In a way it is a "falling around" that mass. My question Is it ...
3
votes
3answers
462 views

Size of atoms based on atomic number

I'm interested in the size of atoms (extent of the outermost electron cloud), in particular its cross-sectional area and how it scales by increasing Z. (I trust that this won't be affected much by ...
8
votes
5answers
576 views

How would I go about detecting monopoles?

A question needed for a "solid" sci-fi author: How to detect a strong magnetic monopole? (yes, I know no such thing is to be found on Earth). Think of basic construction details, principles of ...
8
votes
4answers
5k views

Weight on carpet vs. hard floor

Will the scale say I weigh more, less, or the same on a carpet as compared to a hard floor? You can assume the scale works via spring mechanism. Free body diagrams encouraged!
4
votes
10answers
1k views

What is the wavefunction of the observer himself?

I am aware about different interpretations of quantum mechanics out there but would mostly like to see an answer from the perspective of Copenhagen interpretation (or relative quantum mechanics if you ...
1
vote
4answers
694 views

How to describe a well defined “zero moment” in time

Suppose you have to specify the moment in time when a given event occurred, a "zero time". The record must be accurate to the minute, and be obtainable even after thousands of years. All the measures ...
6
votes
3answers
865 views

Pauli exclusion principle and Entangled pairs

It is true for fermions in the same potential that the total wavefunction of two particles must be antisymmetric with respect to exchange of electrons. Which means the spin wavefunction is given by ...
9
votes
3answers
420 views

If time standard clocks and any memories about the time standard are destroyed, can we recover the time standard again?

Assume the time standard clocks and any memories about the time standard are destroyed. Can we recover the time standard again exactly? Recovering the time standard again means we can determine the ...
4
votes
4answers
1k views

Measuring the speed of light and defining the metre - absolute or relative?

If the metre is now defined as the distance light travels in vacuum in 1⁄299,792,458th of a second and the speed of light is accepted to be ...
25
votes
5answers
3k views

What if the universe is rotating as a whole?

Suppose in the milliseconds after the big bang the cosmic egg had aquired some large angular momentum. As it expanded, keeping the momentum constant (not external forces) the rate of rotation would ...
10
votes
2answers
597 views

Unambiguous distinguishing of quantum states by local measurement

Let's have two orthogonal n-particle quantum states: $|\psi \rangle$ and $|\phi \rangle$. In theory it is always possible to make an unambiguous measurement. However, things get complicated when one ...
35
votes
13answers
9k views

Home experiments to derive the speed of light?

Are there any experiments I can do to derive the speed of light with only common household tools?
6
votes
4answers
2k views

Finding the volume of this irregular shape I have

I have an approximately basketball-sized non-hollow piece of aluminum sitting in my house that is of irregular shape. I need to find the volume of it for a very legitimate yet irrelevant reason. ...
18
votes
2answers
2k views

How does one measure the mass of a galaxy? And other such large quantities

Trained as a pure mathematician, I see claims about the mass of a galaxy and other such huge measurements that are arrived at experimentally, and I just have to scratch my head. I know this is a bit ...