Questions tagged [time]
Questions on time, the indefinite progress of events in the Universe.
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What are the twinkling stars in the New Horizons Arrokoth approach?
I've circled them in this edit:
Source: https://commons.m.wikimedia.org/wiki/File:New_Horizons_Approach_to_Arrokoth.ogv
Note, this has generated frames, see the source....
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Why does the tropical year have a ~161 years cycle?
Using PyEphem, I calculated the time difference between consecutive summer solstices in the south hemisphere for the last 4000 years, and plotted them in a graph. It seems like random noise around the ...
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Does Gravitational Time Dilation stack on top of Time Dilation caused by Velocity?
Using 1 CM from the Event Horizon of Super Massive Black Hole, SGR A, as the reference point. The particles within the accretion disk are traveling at extreme high speeds. Assume this speed increases ...
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Is TDB monotonic? Does it or any of its derivatives have yearly discontinuities with respect to an atomic clock?
This in-depth answer mentions that
...TDB is updated every year. As technology improves, these subtle updates change the timing of past events.
This makes me wonder...
Does this updating result ...
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Understanding the Julian Date equation in detail
I am trying to figure out the Julian date equation by myself. Unfortunately, there are not many resources I could find which explains in depth. Moreover, there are several variations of the same ...
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Is it possible (and if so where can I find one) to buy a sidereal wall clock or kitchen clock?
I've done some research and can't find one of these anywhere but would be dumbfounded if they didn't exist, surely sidereal wall clocks are sold somewhere (preferably online)?
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Calculating local solar time with python ephem library
I was learning to calculate local solar time with ephem. I must admit, unit conversion between radians, hours and days, which are all represented by a float in the ...
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Daytime length and sunrise / set cardinal directions
Let me illustrate the question with an example. On Feb 2nd 2022, the sun rises in Los Angeles at cardinal direction 110 and sets in direction 250 (according to timedate website). This means that the ...
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How are various orbital period measured?
How are the sidereal periods and synodic periods of celestial bodies measured from earth? The usual definition of the sidereal period of a celestial body is the time it takes to complete one ...
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If time is not absolute and depends on the gravitational field, then why we keep using our own (particular) time in cosmology?
Sorry if my question is not really clear, but indeed it is not clear in my mind neither.
But maybe some of you can help.
Time is not absolute and can be affected by the gravitational potential.
Now ...
user19333
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Syncing time for measuring the parallax of Mars
I read somewhere (I can't remember the website) that when Cassini and Jean Richer measured the parallax of Mars, they used Jupiter's (or maybe Saturn's) moons to sync their time. How was this done?
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How is the time of sunrise and sunset determined?
If I do a quick Google search for amsterdam sunrise, I immediately get the time back: 6:42 AM.
How is this time calculated?
(I ...
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How to find the constellation in which the sun is located using the night sky map?
The following sky map was given as part of practice problems in my Astronomy course
The moon is in its first quarter phase. I am supposed to find the approximate date and time of the year in which ...
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J2000 conversion to Position of date
Having spent an inordinate amount of time comparing the LBR values of Meeus (Astronomical Algorithms 1998) vs. ELP82B (Chapront's ELP82b Fortran Program)
I have figured out the data set I'm using is ...
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How to determine time when a photo of star trails was taken?
I was asked to define a time (most likely the month) and location of the picture below.
I hope I understood it right that it is the south pole, because we don't see a Polar star in the middle. ...
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How to determine how often a planet's center will be collinear with its moon's?
Expanding on the question: Let's say I have a planet orbiting some star (earth-like, sun-like, for the sake of example). If this planet has two moons, M1 with orbital period of 30 earth-days and M2 ...
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What exactly is a Right Ascension clock and how was one (mounted on a telescope) used in practice, historically?
@MikeG's answer to Why does this Lowell Observatory telescope have so many knobs? What do they all do? explains that item #6 labeled in the image there (and cropped version here) is likely to be a "...
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Is the Milankovitch calendar provably better than the Gregorian one considering a non-constant tropical year?
It's somewhat of a no-brainer the revised Julian calendar (attibuted to Milankovitch) is more accurate than the Gregorian one just because it started with a more accurate estimate of the duration of ...
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How do you calculate local time from local sidereal time?
There are many calculators online to convert local time to local sidereal time, but I can't find any resources to convert the other way. Can you convert back by doing the same conversion backwards? ...
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About bias in sidereal time (used by astronomers)
I came up on this stanza in various websites when looking up on experimenter bias. It says
"If the signal being measured is actually smaller than the rounding error and the data are over-averaged, a ...
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Energy conservation of the universe
I have tried to derive an equation for the total energy of the universe.
I have found that,
$$E(t)= \delta\dot a(t)^2a(t)\Omega(t)$$
Where $\delta$ is just a positive constant, a(t) is the scale ...
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Why does gravity make time go slower and warp light?
I know that objects with lots of gravity are capable of warping light or slowing time (an example being a black hole). I also know this is because of the theory of relativity, but I need someone to ...
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How to even approach this type of question
Can someone tell me how one would approach this type of question. is there an equation we would use or something of the sort.
Ths solution to this question is given below but I just want to understand ...
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Does time flow in a Minkowski spacetime?
In a spacetime where the stress-energy tensor is null (no energy, no matter, no entropy), I wonder whether any motion of the variable time in the phase-space is well defined.
The arrow of time, meant ...
user19333