Questions tagged [distance]
The distance tag has no usage guidance.
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Would a supernova 1A appear to last longer if it were more distant and does it depend linearly on measured cosmological redshift?
Would a supernova 1A appear to last longer if seen more distant and does this depend linearly on measured cosmological redshift? I asked a question on a very popular radio station where they talked ...
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1answer
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Confusion with light year distance and space events
I had read that the Betelguese star may be going supernova in may of 2022. Now it is about 500 Light years away, so if we see a supernova explosion in may, then does that mean it occurred about 500 ...
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When we say 'Andromeda galaxy is 2 500 000 light years away from us' do we mean 'now' or in a far past?
When we say 'Andromeda galaxy is 2 500 000 light years away from us do we mean 'now' or in a far past and can this past be calculated easily?
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If I putt a golf ball that is 5 x heavier (229.5 grams) than what a normal ball weighs, 45.9 grams 3 foot, how far would it travel if it were 45.9g? [closed]
To start off, I am a layman, i.e. I have no understanding of physics so I thought id ask on the relative forum for some help.
I am looking at buying practise golf balls that are 5 x heavier (229.5 ...
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1answer
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Why the parsec (pc) is still a good cosmological definition in the curved spacetime in a large scale of universe?
The parsec (pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,000 astronomical units (au), i....
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What is the "true" distance an object travels based on relative speeds?
There are two objects (x and y) with x travelling at 10km/h and y travelling at 11km/h, both with respect to the earth. After 1h, from the perspective of the earth, y travels 11km, but from the ...
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1answer
46 views
Distance given two velocities
I have a home trainer that is connected to an application that I am writing which needs to calculate a distance traveled given the speeds that the trainer is sending.
As such, every second, the ...
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19 views
Relation between proper distance and comoving distance
I have a doubt regarding the comoving distance and the proper distance.
be $t_e$ the time of emission of a photon at comoving coordinates (0,0,0) and $t_0$ the time the photon is received at ...
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Ryden Eqn 5.49, Proper distance with changing scale factor
In Chapter 5 on Barbara Ryden Intro to a Cosmology 2nd ed, she presents this equation for calculating the proper distance at current time ($t_0$) to a distant galaxy whose light emitted at time $t_e$ ...
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1answer
35 views
On the decibels of a Heartbeat
I am trying to gauge the strength of the super-senses of a character from a novel, and I am seeing exactly the decibel range he can hear. The situation is being able to hear heartbeats, but I am ...
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1answer
45 views
Why does the estimation of the distance of supernovae depends on the cosmological model?
I was reading a paper from arxiv (https://arxiv.org/abs/1312.5798) when I stumbled upon this passage at pag 4
"However, even at low redshifts, there are limitations to how well the
Type Ia ...
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1answer
59 views
Light cone shape
Looking at figures such as on the following page:
Is the cosmic horizon related to the Big Bang event?
I am a bit confused about the shape of the light cone. In the top diagram (proper distance) it ...
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2answers
37 views
How to distinct between far loud voice and near soft voice?
How to distinct between far loud voice and near soft voice?
Imagine a voice assistant robot trying to know if a person is commanding with her louder voice from a long distance or with her softer voice ...
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0answers
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Breaking distance including downforce, air etc
I would like to calculate breaking distance for car from 200km/h to $100$ km/h with acceleration $-44$ m/s. I found this:
$$
V_{\rm init} = 200~{\rm km/h} = 55~{\rm m/s}~,\\
V_{\rm final} = 100~{\rm ...
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2answers
115 views
Why is position proportional to time squared?
Now I know some of the obvious answers to this, such as if you integrate the acceleration twice, you’ll get time squared, but what I’m really looking for is more of an intuitive answer.
One of the ...
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37 views
Myopia far point virtual image
My textbook says that a diverging lens works by rendering the object a virtual image at the myopic eye’s far point. However, wouldn’t the eye then perceive an object farther than its far point at the ...
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3answers
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How does the universe preserve distance? [duplicate]
Assume I have some physical system, no matter of it's nature. Suppose also that this system can be descripted as some scalar field. So my physical object is just a function q = f(x, y, z). Imagine ...
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1answer
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Is the size of far away galaxies smaller or larger than expected?
When items are further away, they look smaller. If we know the size of something nearby, then we can calculate the size of something a known distance far away. So if there is a galaxy whose size (...
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1answer
37 views
How do we measure the size (not mass but dimensions) of far away galaxies?
I understand how distances to galaxies are measured. I think I even understand how their mass might be measured (by their orbital trajectories?). But how can we know How big far away stars are? Like ...
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2answers
327 views
Difference between distance and norm
In special relativity, different observers measure lengths of objects differently, depending on their respective velocities. However, all observers agree on the invariant inner product of two vectors (...
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1answer
44 views
Forces distance dependent find derivatives of position time dependent
Suppose we have a force which is dependent on distance from some point. It is easy to find the acceleration based on the distance from that point, but in a previous question, I asked they told me that ...
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1answer
33 views
Distance of the Moon Cycles
Recently, I started to search more about the orbit of the moon, and noticed there are certain periodic patterns or cycles for which I did not find any satisfactory explanation.
The first cycle can be ...
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54 views
Suppose you are told that the linear size of everything in the universe has been doubled overnight. Can you test this statement? [duplicate]
Suppose you are told that the linear size of everything in the universe has been doubled overnight. Can you test this statement by measuring sizes with a meter stick? Can you test it by the fact that ...
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1answer
79 views
Distances in General Relativity, near massive bodies
I've been studying the basics of General Relativity, and my question is: does it make sense to say that near a black hole (or any massive body), distances increase, the way on a topographical map the ...
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How is position calculated when the acceleration is not constant?
To get the position of an object we can use the equation: $$x=x_0+v_0t+\frac{1}{2}at^2$$
But now I don't have a constant acceleration, both $x_0$ and $v_0$ start at $0$ and $v$ ends at $16 \text{ m/s}$...
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1answer
36 views
How to calculate the speeds two objects need to move at in order to reach different destinations at the same time [closed]
For example: On a graph there are two points. Each point has a different destination. The distance between Point A and its destination is 50, and the distance between Point B is 100. The points will ...
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2answers
351 views
How do I determine the exact distance from Jupiter to the Sun on a specific date?
I've recently needed to determine exactly how far Jupiter was from the Sun on April 25th 2018, when a Hubble image of Jupiter was taken.
I'm a beginner in physics and Google searches lead me nowhere. ...
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2answers
77 views
Variables in rectilinear motion
I wrote a post few days earlier on circular motion but it seems i still haven't got the hang of it yet. When is this equation actually true?
$s=ut+\frac{1}{2}at^2$
Suppose velocity is given by $v=t-2$ ...
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1answer
33 views
Work in different forces over the same distance [closed]
If two forces are different (Force A < Force B) but the distance over which the forces are applied is the same, then by the work formula, the object that is pushed with force B should have more ...
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1answer
68 views
Can we observe an event that occurs more than 13.7 billion light years away? [duplicate]
In Kurzgesagt's latest video about the largest black holes, the narrator says that two black holes have been observed orbiting each other at a distance of 17 billion light years from Earth. So light ...
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1answer
162 views
How can the strong force, which is conservative, not follow the inverse square law?
In terms, which someone with a background in chemical physics & quantum chemistry might understand, what is the evidence that the strong force, across whatever its range is, follows something ...
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504 views
Regarding distance laws of gravity from “A Brief History of Time” and why the Earth doesn't fall into the Sun
In “A Brief History of Time”, Hawking explains Newtonian gravity in Chapter 2, Space and Time. The further apart the bodies are, the smaller the force. The gravitational attraction of a star is ...
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1answer
86 views
Why do we consider that if initial & final positions are same then displacement of an object is Zero?
I was thinking on a basic high school problem about motion on one axis and came across one of those problem where displacement is zero because final and initial positions are same.
My question is that ...
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2answers
30 views
Is it possible to derive a distance time graph from a displacement time graph?
If I take the derivative of a displacement-time function, it will give the function of its velocity over time. If I take the absolute value of my velocity function it will give me a function of its ...
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2answers
129 views
Shooting two projectiles at the same time with different mass [closed]
Shooting two projectiles having the same radius and in the same condition with the same initial velocity and angle
one with a mass of 10kg and the second with a mass of 100kg
which one of them will ...
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1answer
92 views
What is the reason only one axis measure is given for the Universe?
We are given the diameter of the Universe to be approximately 880 Ym. Is this the the distance observed at any place when looking into space, or is this value more of an average?
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Linearity from fractional equation? (solar cell)
I am doing a little research into solar cells, namely the fill factor. It is a ratio, defined as maximum power divided by theoretical power [of the solar cell].
The maximum power and theoretical power ...
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How should I calculate the redshift of an object if I know its light travel distance?
If an object placed at hubble horizon i.e. 14.4 billion light years approx sends a light ray today and it reaches on earth sometimes in the future so how can I calculate its redshift when it will ...
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1answer
60 views
Distances in cosmology (relativistic) [closed]
so, my problem is that distance measures in cosmology seem to ignore General Relativity GR (or even STR). There, the proper distance is the distance w.r.t. a specific rest frame!
This means that, in ...
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1answer
73 views
Distances in cosmology
I want to make sure that I understand the different distance measures is cosmology.
To do that I consider the FLRW metric:
$$ ds^2=dt^2-R(t)^2\left(\frac{dr^2}{1-kr^2}+r^2d\theta^2+r^2\sin^2\theta d\...
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2answers
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What is definition of displacement in context to kinematics? [closed]
I want explanation of word particular here.
The change in position of a body in a particular direction is called displacement.
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2answers
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Displacement definition
Is it correct to define the displacement exactly as the shortest distance covered (not necessarily a particular case of the distance covered in this case)? In another way, can it be said that it is a ...
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0answers
46 views
Definition of the sound horizon
I have been looking at the sound horizon $r_s$ as used for CMB and BAO analysis. In the literature this is defined as
$$
r_s(z,\mathbf{x}) = \int_0^z \frac{c_s dz^\prime}{H(z',\mathbf{x})} \quad (1),
$...
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2answers
64 views
Is the line element a distance vector or displacement vector?
In my Electrodynamics and Electromagnetism course, the professor is deriving Maxwell equations and the electromagnetic field tensor from differential geometry and wants to show how special relativity ...
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1answer
55 views
Is it a coincidence that distance between Sun and Earth=(Distance between Earth and Moon)*(365.25+24) or is there any logical reasoning behind it? [closed]
Here $365.25$ days is the time taken for Earth's Revolution around the Sun while $24$ hours is the Earth's rotation.
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Is it possible for coordinate distance to disagree with proper distance in flat spacetime?
The title pretty much sums it up. I'm learning about general relativity and I've ran across descriptions of coordinate distance not matching with a moving objects proper distance. We know this is ...
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Is the $d$ in $W=F*d$ displacement or distance?
My textbooks say that work=force times displacement but when I was considering conservative and non-conservative forces I got a bit confused. I know that the work done by non-conservative forces onto ...
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${}$ Electric Charges [closed]
We have two positive point charges, moving toward each other, with velocities $v_1$ and $v_2$. How to prove (mathematicaly) that their distance will be minimum, when their velocities become equal? The ...
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1answer
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Calculate displacement through a force acting on body during some time
By definition 1 Newton is the force that acting on 1 kg body during 1 second will move it on 1 meter. It is clear.
I confused on calculating the distance, with another force and mass. Obviously, 2 ...
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How to calculate WORK when FORCE vector is Diagonal, and Object is moved Diagonally at a Different Angle?
Suppose I have this scenario :
(a) The force vector is [2, 4]. (This means the X component of the vector is 2, and Y = 4 ).
(b) The object is moved diagonally [5, 6]. (This means the object is ...
