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3
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1answer
153 views

Distance between two galaxies of different redshift

Let $Q_1$ and $Q_2$ two different objects in the Universe (we can think to two galaxies or quasars), that we observe from the Earth at different angular position $(\alpha_1,\delta_1)$, $(\alpha_2,\...
0
votes
1answer
15 views

Relyance of plate distance on the capacitor equation

I am studying capacitors and i cannot seem to understand why the increase/ decrease in voltage and distance between the plates would affect the capacitor's abillity to store charge. Can anyone help??
0
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1answer
71 views

Are measurements of time and distance independent or always coupled by the speed of light

In texts about special relativity the light clock is usually described as a tool to measure time $t$. It counts how often light travels along a given distance $d$, i.e. $t = d/c$, where $c$ is the ...
0
votes
1answer
81 views

How to use radio waves to calculate distance over short distances?

I read an article about a company that created the equivalent of a GPS location system for internal spaces where the satellite based GPS is blocked. They made reference to the Fresnel number as to ...
0
votes
1answer
40 views

Finding the distance between two osclilating particles in a wave

Assume a wave function $\psi = \psi(x,t)$ where $x$ is position from the starting point $(0,0)$ and $t$ is time. Two oscillating points A and B are located at $x_1$ and $x_2$ respectively with $x_2 \...
-1
votes
1answer
91 views

how can $r=\frac{1}{n^{\frac13}}$ be used to calculate the mean separation between electrons?

Can $r=\frac{1}{n^{\frac13}}$ be used to calculate mean separation of electrons suppose that Na which has BCC crystalline structure, each atom donate 1 electron to form metallic bonding As it's BCC ...
6
votes
0answers
62 views

A 'distance' measure that involves 3 quantum states

The following question was asked by my friend Elie Wolfe. Given two quantum (or even classical) states $\rho, \sigma$, there are various measures that say how 'far' these two quantum states are, such ...
1
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0answers
24 views

The angular diameter distance for a radiation dominated universe

I'm attempting to work out the angular diameter distance for a radiation dominated universe, with $k=0$ and $\Lambda=0$. I have gotten myself to this point: $$ D_{A}=\frac{1}{H_{0}(1+z)}\int^{z}_{0}...
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0answers
52 views

Can a photon be captured in a grid space representation at a fractional Planck position?

Consider a photon, positioned in space in a finite portion of a grid. Any point of the grid is vertically or horizontally aligned, each distanced by a Planck unit. $l_P = 1.616 199(97) × 10−35 m$ ...
1
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0answers
47 views

Help with finding an equation to work out the length of cable required to produce loss of colour on an analogue video signal

When I briefly taught Broadcast Engineering I set up an experiment in order to demonstrate the effect of signal reflections along coaxial cable on an analogue PAL waveform. It involved getting the ...
1
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0answers
98 views

Which physical entities equal “distance times time”?

Are there useful physical quantities with dimensions of distance-time? The background for this question is a differential equation which I try to make sense of: http://math.stackexchange.com/...
0
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0answers
28 views

Scalar invariance and dimensions

I recently read an interesting article on scale in variance http://www.wired.com/2014/08/multiverse/ It discussed how modern physics is suggesting that scalar units really may not apply above the ...
0
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0answers
31 views

Does this calculation give displacement or distance?

So we have velocity as a function of time given $\overrightarrow{v}(t)=(1-2bt)k\overrightarrow{r_0}$ where $b,k$ are positive constants and $\overrightarrow{r_0}$ is a unit vector. It is found that if ...
0
votes
0answers
26 views

Why is light redshifted?

I heard that very distant stars can be seen as red. Why does light become more 'redder' when travelling long distances? My guess would be it loses some sort of energy, but can't seem to figure it out ...
0
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0answers
33 views

How to derive velocity, distance from a changing acceleration?

I'm making a electronic device that is out of the scope of this site, but essentially it gives me acceleration readings every X microseconds. Given these samples of acceleration, how can I find out ...
0
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0answers
11 views

Blocking Window Distance Estimation in sCMOS Sensor setup

I am trying to establish an appropriate distance between a spectrograph output window and a CMOS sensor. The spectrograph creates a focussed image on the CMOS sensor, but I need to block out some of ...
0
votes
0answers
213 views

Luminosity distance as a function of redshift

We know that the luminosity distance is: $d_L = a_0 R (1+z)$ with $z$ the redshift. How can we mathematically make explicit the dependence of $d_L$ from the redshift? I guess we need to make it ...