Astronomy Stack Exchange
Astronomy Stack Exchange

Questions tagged [space-time]

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

Space-time is a concept popularized in Albert Einstein's theory of special relativity and intimately woven into his later theory of general relativity. In our universe, it consists of three dimensions of space and one of time, and so scientists sometimes to the space-time we observe as 3+1 dimensional.

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Why is time referred to as "The" capital T 4th dimension?

Often you hear people say "time is The 4th dimension". What confuses me is that people talk about "The 4th" dimension as if it's a specific thing and I don't understand why. What I mean by that, is that I can plot the position of a point in 3D space…
Michael Seltenreich
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Can Space-Time Itself Have Energy Qualities Like Momentum?

Hypothetically, if space could be moved or scaled, what would happen to everything inside? I'd like to know if an element of momentum could be transferred to objects by contorting space-time. Other than gravity, what effects does space-time…
proPhet
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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 universe is indeed euclidean, but space isn't over…
Terran
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Questions about time and space (from beginner)

To be honest my knowledge about astronomy and related physics is close to zero. However, since I studied math a bit, I would like to ask a couple maybe stupid questions, which I am curious about and I don't know who and where to ask. A) Projection…
Michal
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Will I age slower in space or on other planets?

I came across few videos which says Astronauts in ISS will have 0.07 seconds extra life. So if life is possible on mars, than what is the time period of life for us humans? Is it the same as that of earth or different? For example, if I spend 500…
Ashish Srivastava
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Why is time considered a (fourth) dimension?

Since dimensions usually refer to space and we naturally acknowledge three of them, we also perceive time and we separate space from time ("space AND time"), why is it, that time has ended up in the same shelf as spatial dimensions. Is time really a…
marko-36
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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. So how could the Big Bang create something…
Harshit Arora
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Why is space and time spoken of as one thing

I've never understood why it's spacetime and not space and time. In other words why aren't space and time spoken of as two different things. Can someone explain to me why this is
user11186
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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 exactly where to land so that you are at the same…
Michael James
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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 direction to work. For the life of me I can't…
user21901
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What is the speed of time?

From the theory of relativity, if any object is moving with the speed of light or more than the speed of light, then the time stops or seemed to be stopped for that object. That means, that the speed of time for an object moving with the speed of…
Rahul Yadav
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Light Cone Explanation

Not sure if this question belongs here, or on Physics. Would someone please describe the "anatomy" of a light cone and provide an intuitive example? I have read the Wikipedia article (http://en.wikipedia.org/wiki/Light_cone) and I think I have a…
rdinardo
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Distance between two events

I would like to start from the very basic such as Pythagoras Theorem. If I want to calculate distance between two points in a right-angled Triangle We use $c^{2}= a^{2}+b^{2}$; Using this We are quite capable to calculate the distance between two…
Amartya
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Does Light Year is their past?

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 Light Year away from us, does it means I just saw its…
Onel Sarmiento
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How the watches are showing perfect time?

The actual time for one day is 23hrs, 56mins, 4.1secs right? Then how can the clocks and watches can show perfect time? I mean, if I observe the sun rise at 6:00am this day, tomorrow I should observe it before 6:00 or I can say at 5:56…
Charan
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