As a consequence of the Lorentz transformations, time and space transform into each other when changing reference frame. This calls for a unified description: Minkowski spacetime.

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3answers
142 views

Is a black hole a 3D hole? And doesn't it pull into the 4th dimension?

Hear me out here please: A body on a line (a 1-D world) causes a warp in the line, i.e. a curve (2-D) A body on a plane (a 2-D world) "sinks", causing a warp in the plane, i.e. a pit (3-D) Then does ...
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1answer
161 views

Is time an illusion? [closed]

IS time an illusion? I have tried thought experiment after TE and quite frankly I can't find any instance where time is defined wholly on its own. It is always a measurement of the interim between to ...
3
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2answers
96 views

Can a hypothetical universe have more than 2 types of dimensions: spatial and temporal?

Our universe is often described as having 3 space-like dimensions and 1 time-like dimension. Can hypothetical universe exist with more than space- and time-like dimensions? If so how would these ...
3
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2answers
370 views

Why time is considered a dimension?

Why is time considered to be a dimension? And the other 7 (except the 3 dimensions of space, and the dimension of time) dimensions that string theory suggests, why can't they be realized?
3
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3answers
177 views

Do massless particles follow the curved spacetime or not?

I am assuming that zero (rest) mass particles don't interact gravitationally with each other and other particles. Does that mean they experience a "flat" spacetime instead of a curved one? I find it a ...
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2answers
112 views

Is it possible to travel ONLY through Time and not Space? [closed]

The question is as stated above. I although think, the most probable answer is no, but I really want to know the reason to it. If, One can travel through only space by travelling at the speed of ...
0
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1answer
142 views

What is dimension and how many types of dimensions are there in the universe?

What is dimension and how many types of dimensions are there in the universe? I mean how many total dimensions are there? I have only heard about 2d and 3d. Other than these two, are there any other ...
2
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3answers
268 views

Vacuum-ether and spacetime

In the past you could not give an explanation for various phenomena in which there was an action at a distance, like magnetism or gravity, that occurred in a vacuum; For this reason, ether was ...
3
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0answers
147 views

Curvature and spacetime

Suppose that it is given that the Riemann curvature tensor in a special kind of spacetime of dimension $d\geq2$ can be written as $$R_{abcd}=k(x^a)(g_{ac}g_{bd}-g_{ad}g_{bc})$$ where $x^a$ is a ...
6
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2answers
332 views

Sewing together flat spacetime pieces = flat spacetime?

I'm trying to imagine the geometry "operations" here: Angular deficit and Conical spacetime of cosmic string If we sew flat spacetime pieces together, what is the requirement for the sewing to not ...
-3
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3answers
115 views

Why would the curvature in space-time attract photons which have zero mass? [closed]

I know that we are surrounded by dark matter, does the dark matter affects space time ???and I know the reason for gravity according to explanations in general relativity. But all the explanation ...
3
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3answers
175 views

How can space be euclidean when light bends?

I have read people arguing that tridimensional space sections of space time continuum (whatever its number of dimensions) appears to be euclidean from empirical evidence. I cannot reconcile it with my ...
0
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1answer
54 views

Time relativity / paradox [duplicate]

After watching the movie Interstellar, the theory of time relativity / paradox really mind-boggles me. If it is true that gravity controls everything even to the extent of time, then it might as well ...
3
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1answer
153 views

Regarding the possibility of Closed Timelike Curves

I've been looking a lot at Closed Timelike Curves, and how if a theory allows for these curves it doesn't respect causality. I understand that about the curves themselves (Grandfather Paradox), but ...
3
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1answer
70 views

The actual space curvature

What is the curvature of our physical space, according to the latest experimental data? I've found it somewhat difficult to find a definitive answer to the question, because the spacetime curvature ...
2
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7answers
496 views

Curvature of Spacetime

I have been exploring for some time both the Special and General Relativity, hoping to glean at least a conceptual grasp of their basic tenets. In reading the book "Gravitation" by Misner, Thorne and ...
1
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2answers
71 views

Theory of relativity. Relative to what? [duplicate]

If I properly understand relativity, time ticks faster for an object sitting still than for an object passing by. So, in a universe with only two objects which have the same "age", object A is ...
0
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1answer
71 views

Exactly which components of special relativity are contained in Minkowski spacetime?

In other words, which components or concepts in special relativity are reflected in Minkowski spacetime? If I'm not mistaken, Lorentz covariance is one of these concepts, correct? I'm trying to ...
1
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3answers
293 views

How do we know dark matter isn't curved spacetime?

Could Dark Matter actually just be spacetime with curvature "leftovers" from the big bang or the inflationary epoch?
0
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0answers
71 views

Spacetime in Loop quantum gravity

In LQG, does spacetime consist of interconnected loops? Are those loops real? If spacetime does not consist of the aforementioned loops, what it consists of?
0
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1answer
102 views

How does a wormhole form? [duplicate]

I heard about wormholes. I know that they are paths that can be got by contracting spacetime. But, how does a wormhole form?
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2answers
104 views

Does mass curve space?

Just to be sure, according to the theory of General Relativity, my understanding is that mass curves space-time. My question is, can mass also curve space?
0
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2answers
54 views

Space: a vacuous void or an entity?

I am a chemist and, until recently, a senior Research Manager with a major chemical company. Please excuse the potentially naive ramblings of an idiot in what follows, but I do not have the ...
1
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0answers
47 views

Space and time variant? But together invariant?

I admit I'm having difficulty with spacetime. I don't understand how unifying space and time, seemingly variant quantities, results in an invariant spacetime. All texts and references talk about using ...
6
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4answers
813 views

Does (it make sense to say that ) the universe has a center?

I was reading this page: http://www.guardian.co.uk/science/2011/oct/23/brian-cox-jeff-forshaw-answers and I found this sentence by Brian Cox: That seems to imply that everything is flying away ...
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2answers
33 views

Is there a friction or retarding force in creating spacetime?

As matter and energy expand with the big bang, they create spacetime (or so I've been told). Is there any evidence that this creation of spacetime has a retarding force on the expansion? If not, ...
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2answers
58 views

Expanding universe and speed of light [duplicate]

Galaxies are moving away from us proportional to the distance between us and them , but nothing can travel faster than light, so even the farmost galaxies should be travelling away from us along with ...
2
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2answers
203 views

Why do things slow down when you move faster, rather than speed up?

I've been trying to get to grips with SpaceTime. As I understand it, we move at a set rate through spacetime. Any increase in our rate of travel through space results in a decrease in our rate of ...
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3answers
201 views

Is a nuclear bomb in some sense a bullet travelling at the speed of light, but along time rather than along space?

Apologies if this is a silly or perhaps obvious question, but $E=mc^2$ just looks so much like classical kinetic energy (except for the factor of 2). So I'm thinking of the to-be-fissioned-away ...
0
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1answer
69 views

What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
1
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2answers
79 views

Allowable spacetime deformations [closed]

What deformations are possible with spacetime? By 'deformation' I am referring to the kind of change in spacetime caused by the presence of a mass which deforms spacetime sufficiently to deflect ...
0
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1answer
40 views

Relationship bewtween the principle of Galilean Relativity and absolute time

The principle of Galilean Relativity is: The laws of Mechanics are invariant in every inertial frame of reference. I say "laws of Mechanics" specifically because I'm referring to the principle ...
1
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0answers
47 views

Are reversible and irreversible processes frame dependent?

since it is all about time. If I have a look at an irreversible process from a frame where time runs really slow. is there a possibility of considering that process reversible from that frame?
0
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1answer
127 views

Could there be a time dilation of 2,000,000x between Earth and other parts of the universe?

Don't ask me why, but you may be able to guess why I would ask such a question. The question is, what kind of conditions would have to be present in a universe in order for billions of years pass in ...
2
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1answer
93 views

Does spacetime have symmetric curvature around an object? If yes, then why do planets revolve around the Sun in elliptical orbits?

Does spacetime have symmetric curvature around an object? If yes, then why do planets revolve around the Sun in elliptical (as opposed to circular) orbits?
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2answers
95 views

Off-diagonal terms in metric for 4D space-time [closed]

Consider a delta between two events in 4D space-time written as a 4-vector, $x^\mu=(dt, dR)$. The time $dt$ is a scalar difference in time. The 3-vector $dR$ points some direction in space. One ...
4
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2answers
158 views

Why are orbits around black holes stable?

Black hole theory involves space (or space-time), itself, being sucked into the black-hole, with the event horizon marking the point at which space/space-time is moving faster than the speed of light. ...
15
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6answers
3k views

Is it possible to watch the same distant star's supernova event twice?

Usually relativistic time dilation effects require something traveling near the speed of light. But the high speed requirement can be replaced with a high distance requirement instead. Traveling away ...
2
votes
1answer
115 views

Can energy bend space? [duplicate]

I know mass bends the space around it and I also remember matter can be converted into energy and vice versa, so my question is: can energy interact with space in a similar fashion as matter does?
11
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3answers
533 views

Space is expanding so what is time doing? [duplicate]

Space is expanding and as we know space and time are intrinsically linked to be now known as spacetime. What is happening to time during expansion? Is there more time, longer time or is the time part ...
0
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2answers
56 views

Can I see stars in my light-cone that you can never see?

The light cone of our galaxy is a lot different to the light-cone of a galaxy 5 bly away. Our Hubble volumes are much different. Everyone is born in/at a different space/time. Can I see stars in my ...
1
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2answers
72 views

Can a point in empty space be motionless with respect to light?

Being that the speed of light is constant throughout the universe, can a point in empty space be motionless with respect to light?
0
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1answer
75 views

Is gravity instantaneous? [duplicate]

I want to know if (hypothetically) a star appears out of nowhere at a certain distance (say 20 light seconds) away from me, how long will it take for me to get the feel of it's gravity? Will I know it ...
13
votes
2answers
1k views

Can quaternion math be used to model spacetime?

Quaternions are commonly used to model 4 dimensional systems where the quaternion consists of a real 3 dimensional vector and an imaginary scalar. So on the surface Quaternions seem well suited to ...
2
votes
2answers
151 views

What spacelike, timelike and lightlike really mean?

Suppose we have two events $(x_1,y_1,z_1,t_1)$ and $(x_2,y_2,z_2,t_2)$, then we can define $$\Delta s^2 = -(c\Delta t)^2 + \Delta x^2 + \Delta y^2 + \Delta z^2$$ which is called the spacetime ...
3
votes
2answers
90 views

The creation of time in the early universe

I have seen roger Penrose video https://www.youtube.com/watch?v=sM47acQ7pEQ. In it explains that time origins are related to the rise of mass in the early universe. In the video it relates mass from ...
0
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1answer
64 views

Infinite halving of a distance

If an object is, say, 100 cm. from a wall, and I move the object halfway to the wall and stop, then the distance is reduced to 50 cm. If I continually move the object by one half of the remaining ...
1
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2answers
65 views

Gravity and the Speed of Light

Let's assume that I am on an airplane that is at about 4,000 altitude and now let's also assume that I am standing on one of the wings with a light torch, if I point the light torch below to the ...
0
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2answers
116 views

How does the warping of time behave as a fourth dimension?

My problem is that I have a hard time grasping something if I can't conceptualize it, though maybe this can not be conceptualized, just accepted, in which case I thank you for your patience. The ...
2
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2answers
102 views

Proper length in GR

What meaning/use is associated with the notion of proper length in general relativity? Do you know an example of any quantity that depends on it? I have so far found statements like "the length ...