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Questions tagged [space-time]

Questions regarding the 4-dimensional background structure of our universe.

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Is space a thing?

Based on my extent of knowledge relating to astrophysics, I once thought space is a thing, which can be twisted a long side with Time regarding masses of objects(According to relativity theory). But ...
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What is the difference between the way light travels in a gravitational field and the way it travels through an expanding universe?

A photon is travelling through space. As it travels, the space through which it travels is expanding Does this describe A - a photon travelling from a distant galaxy to earth B - a photon travelling ...
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Does the Milky Way's movement through space have spacetime implications?

The way I usually see spacetime explained, it says that if you just sit still, you are moving at 0kph and so you are moving at maximum speed through time (ie. time for you is flowing at maximum speed)....
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What is the exact meaning of vicinity of Black hole or a disk? the same as inside?

What is the exact meaning of vicinity of Blackhole or a disk? Is this the same as inside the horizon for black holes? If so, why people don't say inside of BH, simply. What is the difference? I use ...
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How to convert factors of time dilation into something relatable? [duplicate]

On this post, Time according to the gravity of Sagittarius A? They found the factor of time on the varying distances from the SMBH, I am curious on how to turn those factors into relatable terms ...
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How is distance in light-years converted to years back in time?

When I look at the Alnitak,the left most star of Orion's belt, it is 736 light years away. How could I convert this distance to an estimate of how long ago what I am seeing happened. Would it be ...
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How to compare the observation with the theoretically predicted result?

On the Wikipedia Article on “Geodesics in general relativity”, it says the following: “Thus, for example, the path of a planet orbiting a star is the projection of a geodesic of the curved 4-D ...
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How can the universe be expanding? [duplicate]

I assume expansion implies an increase in the volume of the universe. But if the volume of the universe is increasing, does that not imply the area it is expanding into's volume is being reduced?
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Why do we use the Planck length?

We are not able to quantize spacetime and the theory of loop quantum gravity has been proved wrong but we still use the Planck length in astrophysics. Why?
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Since gravity is like an indent on a piece of paper (the space/time matrix) to a marble, can the black hole eventually suck in the matrix?

Can a black hole suck in time? People claim that if you were to put a bowling ball on a trampoline and rolled much smaller balls through the deppression, some would stay in "orbit", some would roll ...
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Is there a limit to how fast spacetime can bend/warp around an accelerating object?

If in the future a spaceship can accelerate to nearly the speed of light, will it encounter any kind of resistance/drag from the spacetime in front of it not being able to bend/warp fast enough around ...
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Does time dilation increase within overlapping gravitational fields?

If a spaceship was to travel to the barycenter of a binary star (the stars having identical size and mass) and come to a stop there, would the people on board this spaceship find that time is moving ...
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What exactly is the cosmic definition of ‘now’ is?

There is no cosmic definition of now because of special relativity, because of rate at which time flows for a particular object depends upon your point of view and your velocity. For a rocket ...
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Beginning of space-time

I have read that the Big Bang created space-time, but how could this be possible? The Big Bang was itself a singularity, and a singularity is a point in space-time where the curvature becomes infinite....
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Space curvature and its rotation

As I learn, the gravity is caused by the spacetime curvature. Is there any gravitational/magnetic field that really exists around the Earth, or any other planets? Since the planets/stars rotate, does ...
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Does Time Exist for Photons? [closed]

If time slows down the closer you get to the speed of light, does it follow that time does not exist for photons. Do photons - even if they travel across billions of light years of space - arrive at ...
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Dark Matter Curvature

Does Dark Matter affect Space Time Curvature? If so, then what is the formula to calculate space time curvature due to dark matter?
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What is the actual black hole merger speed?

I have seen models of 2 black hole mergers. https://www.theverge.com/2017/11/16/16665132/gravitational-waves-ligo-virgo-black-holes-merger-multi-messenger-astronomy When we see a space ship appear ...
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What is the fastest a galaxy or other body has been measured to (or can) travel?

Our solar system travels at an average speed of 515,000 mph and our galaxy at 1.3 million mph through space. What is the fastest moving body in space recorded and the fastest can a black hole or ...
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108 views

Are we really seeing the asteroids from the past?

Is it actually relevant to study objects that are light years far? Because in theories we are actually seeing the past as the light takes years to reach us. Lets say we are studying a asteroid that ...
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1answer
131 views

How well is Earth’s motion through the universe quantified?

If I had a time travel machine that could drop me into any point in space and time, could I accurately predict earth’s “position”? I know position is an improper term. Would it be possible to know ...
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Is the shape of observable universe and shape of space same?

I have read that Euclidean space is considered as flat space and Minkowski space is flat space-time. So when we say our observable universe is flat are we saying that the space is flat or space-time ...
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How does space time differ between galaxies? [duplicate]

Does the gravity wells differ enough between galaxies to have different speeds in space time? How much slower in space time would the biggest galaxy have compared to the Milky Way?
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How does space time differ within a galaxy?

Not the same question but is similar to other marked duplicate. How much time dilation does the center of a galaxy can exist and sustain human life from our point of view? What would a day equal to ...
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Gravitational eddies across the galaxy?

I read about natural gravitational eddies that travel in a wave that black holes have. They also have a strong magnetic field. Does those eddies follow magnetic field lines of the rotating black hole? ...
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1answer
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Which quantum reality will be seen in a future Earth [closed]

If we orbit near a black hole to travel to future and come back to Earth, which of the quantum realities will be observed in the future Earth? My question is regarding many worlds interpretation of ...
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Which quantum reality will be seen in a far away galaxy [closed]

I recently watched Brian Greene documentaries on parallel universes and am trying to wrap my brain around multiple quantum universes that form at every event and Einstein's relativity that in space-...
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do rockets follow a straight path but is looks curved because of space time?

Does the path of a rocket or anything going straight up look curved because the mass of the earth is curving space-time? If we assume the earth, the rocket and all the celestial bodies whose ...
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Is spacetime hyperbolic?

I have always seen answers to this point to measurements of how "flat" local geometry is, but my problem is, thats space not spacetime. I would say its safe to say that the geometry of space in our ...
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Is it correct to assume that the relationship between an objects mass and size, is what decides if it’s a black hole or not?

I’m asking this question in reference to a scenario I saw posted a couple of days ago, where it’s stated that if you would shrink earth to the size of a cherry, it would become a black hole. Is it ...
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Time travel in past and future [closed]

Why it is not even theoretically possible to travel in past but possible to travel in future ?
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How entropy increases over time [closed]

According to 2nd law of thermodynamic, in an isolated system entropy increases over tume. In an open system entropy might seems decreases but combined result of all related events results in overall ...
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Canvas and bowling ball

I'm having trouble understanding the basic model for how matter bends space. The classic illustration is the canvas and the ball but that model needs a reference frame where one can define a downward ...
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What defines stationary vs spinning in space?

To produce artificial gravity on a space station, we simply spin it around some central point, and the acceleration makes objects "fall" outwards. If our space station is so far in deep space that it ...
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Maximum disturbance to space time of gravitational waves, and will this affect humans? [duplicate]

Do we have a theory that can tell us how much change gravitational waves can make to space time. If it is infinite then I think any time we can see biggest change in space time and how much could it ...
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Can we peek into a black hole with magnetic waves? [closed]

Aside from the fact that nothing we know of, excluding pure energy can escape from black holes. They affect both space and time in a manner that nothing else can quite compare to, and usually have ...
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Knowing time any where and any when

My question is if I put you down somewhere in the Milky Way galaxy in any given period of time, is there a way for you to tell when and where you are based on stars or constellations? Or some known ...
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Are wormholes even possible?

While this question could fall under Space Exploration or Physics (I don't have the "best" reputation on THAT forum), I feel that it is very much related to how the universe itself functions, ...
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Does a 4-manifold universe imply zero net energy?

If our universe is a 4-manifold (i.e. with every point in space-time already existing) does this imply that there is zero net energy (as net energy would do work and so change the universe)? If so, ...
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Total mass of light? [duplicate]

I know that light is considered as energy, and as such has a mass. So it is certainly taken into account in universes models and calculations. So I'm wondering: How much of the total mass of the ...
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If the density of nebular distribution increases symmetrically in all directions, how does space curvature explain it?

Edwin Hubble, in The Observational Approach to Cosmology, wrote Thus the density of the nebular distribution increases outwards, symmetrically in all directions, leaving the observer in a unique ...
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Does Light Year is their past? [duplicate]

I just wanted to know if what we can only see out-side of our planet is just the past of other objects? If 1 Light Year is equals to 365.25 Days, then I saw an object outside our planet that is 1 ...
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As a black hole passes through spacetime, does it affect it?

Nothing in the universe stands still. It's always on its way from somewhere to somewhere. A black hole follows a trajectory through the universe, moving from one locus in spacetime to another locus. ...
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What effect does time dilation have on bodies orbiting close to Black Holes?

As far as my (somewhat basic) knowledge of astrophysics goes in general the closer to a star your orbit gets smaller (because you travel less distance) and faster (because you're deeper in the gravity ...
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What is length of the universe on lights perspective

According to Einsteins theory of special relativity, when something is travelling close to light speed, travel path is contracted. When the traveller is light itself, does it see the travel path ...
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What Types of Radiation Emanate in the Future and are Perceived in the Present?

Years ago I came upon a scientific text which mentioned different types of radiation and how they are perceived. One such form of radiation was described (from our perspective and understanding of ...
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Gravitational waves

We know that gravitational waves stretch space-time so light travelling through that space should be stretched as well. So my question is how do we know anything is stretching if the effect is ...
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Could the accelerating expansion of universe inidicate we are surrounded by “denser” space? [closed]

I'm quite novice about all this, only have read some vulgarization books and sites, but I wonder: could all the observable universe be falling outwards on some non-observable, more compact kind of ...
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In what ways does the mass and energy of the milky way curve space time?

Space is curved by mass (or more precisely by mass and momentum as described by the stress-energy tensor). The milky way system has a lot of mass and a lot of energy. In what ways is space-time curved ...
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Could space time curve from the vantage point of earth and out into the universe, and would d = 1 / P in that case give false estimates?

The seventeenth century saw a revolution in astronomy. The invention of the telescope and the acknowledgement of the heliocentric system triggered a race amongst astronomers to measure the parallax of ...