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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Spacetime around a Black Hole

If we consider the sun, then space-time is curve around it. My question is that what is the kind of curvature of space and time around the black hole. Is that space and time more curved around the ...
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325 views

The radius of the universe and time [closed]

Ok - fair warning - Non-physicist asking dumb-assed questions here again. I've been reading a lot of Einstein, Feynmann, Ferris etc. I'm just loving this stuff. But I suddenly found myself looking at ...
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265 views

The metric expansion of space and Hawking

In a Wikipedia article I read that the "Metric Expansion of Space" exceeds the speed of light. If this is true then we must be being disconnected from very remote parts of the universe since gravity ...
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180 views

“Conceptualizing” neutrinos

Layman here. EE and BS physics. I am "content" in viewing photons/electromagnetic radiation as an "emergent" property of spacetime? due to the electrons ("particles..?") and all their activity jumping ...
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93 views

Resources for current thought on time/spacetime?

Are any of the big-name physicists associated with the time in the same way that Hawking and Penrose are associated with black holes? I'm interested in some good books that focus on the topic.
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293 views

Can a vortex be self-sustaining? [closed]

Can vortices be self-sustaining? I suppose vortices in water are not self sustaining, since they need constant supply of water at speed i.e. kinetic energy. But is the same case applicable to space ...
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684 views

Why does moving through space at the speed of light automatically limit us from moving through time? [closed]

If I'm moving through MY reference frame at the speed of light, isn't time still passing by normally for me? Help me think about this fourth dimension- space-time. I want to intuitively understand ...
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1answer
46 views

How can I send a message to myself in the past? [duplicate]

It is easy to send a message to myself in the future: I can put a letter in the post and will receive it tomorrow. Can you think about a way to send a message to myself in the past; it does not need ...
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191 views

Is it possible for the Higgs Field strength, to increase with time? [closed]

Magnetic fields are created when an electric current flows: the greater the current, the stronger the magnetic field. What influences could affect the Higgs Field? If the Higgs field grew in ...
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67 views

Space time curvature and gravity [duplicate]

Is Space time curvature responsible for gravity or Gravity responsible for the curvature in space-time.
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83 views

How is the universe flat?

I have real trouble visualising what is meant by the descriptor 'flat' when referred to the shape of the observable universe. Which one of the below is more accurate? a) It is flat in a 2D way, like ...
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120 views

Does gravity have two directions?

Imagine a particle that interacts strongly with gravity, but not with any of the other forces, and does not interact with normal matter (this may be analogous to the description of dark matter, I'm ...
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1answer
68 views

Spacelike interval and length contraction

I am having a serious trouble finding an agreement between the two facts in Special Relativity: (1) given two events $A$ and $B$ in spacetime separeted by a spacelike interval $s$, the distance in ...
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168 views

Is distance always 0 relative to an object moving at speed of light $c$?

As I understand it, when an object is traveling at the speed of light, relative to itself all travel is instantaneous and the distance is zero. If a photon traveling from the sun was aligned with the ...
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1answer
95 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 ...
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1answer
106 views

Why point mass leaves it's own gravitational well? [closed]

I suppose that point mass has its own gravitational well. Why this point mass is still attracted by other gravitational waves. I expect that this point mass is surrounded by "gravitational hills". Why ...
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1answer
138 views

Does physics recognize the particle of light separately from the wave of light? [closed]

To frame this question, we need to assume that time freezes when traveling at the speed of light. This is theoretically congruent with Einstein's theory of relativity and the theory of time dilation, ...
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312 views

How can time dilation be symmetrical? [duplicate]

I recently posted a version of the twin paradox with a twist but here I'd like to propose a new thought experiment all together. Take two clocks, A & B, and place A 1 AU away from B. Once the ...
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2answers
141 views

Infinitely many points of space-time?

Please can someone provided me with academic literature (Journals/Books, titles & links) which discuss the current view on space time i.e. that there is not Infinitely many points of space-time?
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412 views

Can we have a static point in the universe? [closed]

Big bang theory states that the universe began from a single point (which we may consider as a central frame of reference for the objects in the Universe). In 1929, Edwin Hubble confirmed that the ...
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Does the stretching of space time have a limit?

Why does the stretching of spacetime have no limit? If multiple universes exist. Wouldn't each universe occupy a defined area? If these universes do occupy a defined area wouldn't there be a limit to ...
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310 views

Questions about spacetime curvature and gravity

These are some further important queries regarding the question here Why would spacetime curvature cause gravity? Q1. Explain the statement “Everything in spacetime moves at the speed of light”. Is ...
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2answers
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Can we actually prove with 100% accuracy that there are more than 3 dimensions plus time (t,x,y,z)? [duplicate]

Can we actually prove with 100% accuracy that there are more than 3 dimensions plus time? In the news there are always articles like "there are probably 7, 11 or more dimensions", "time is actually ...
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Is the tide on Earth caused by curvature of spacetime

The tide on Earth appears absolutely whenever the moon is overhead. Is that tide caused by spacetime, re-curvature in space or attraction gravity?
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What does a point in space mean? What we humans think a point in space is in scientific term? (a broader picture)

I am a first year and general student. I Am just curious about the vacuum or space. I just don't get what actually space is. Well, I know our scientists are still working on it but still I just want ...
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133 views

How much energy is needed to curve the space so the Sun will come 1 meter closer to our planet? [closed]

How much energy/work will it take if our planet is: 5.9736×1024 kg or 3.0×10−6 Suns to move Sun and Earth 1 meter closer ...
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167 views

How is spacetime depicted in quantum field theory?

How is spacetime depicted in quantum field theory? Is space and time completely separate, and time is just nature of law as in Newtonian mechanics?
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64 views

How to prepare mental skills to understand relativity theory? [closed]

Upto the high- school, I had to admit and write-on-exam the strange, counter-intuitive statements of relativity theory; those I could not believe. Now, I'm not a physics or math-student, (and indeed ...
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1answer
62 views

Could it be theorically posible “cut off” a piece of space-time? [closed]

I know I may not have an accurate idea of what are the properties of space-time, but here is the idea: By doing an analogy with moving from 2 to 3 dimensions, I have been wondering if in theory it ...
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2answers
69 views

Is time a coordinate or a parameter in Newtonian mechanics?

In classical (Newtonian) mechanics we only ever seem to consider 3-dimensional space, with physical quantities being represented by 3-vectors. My understanding for this is because in classical (...
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46 views

2 space and 1 time dimensions [closed]

I know it is impossible to visualise a 3 space and 1 time dimensions. But what about 2 space and 1 time dimensions? Will it be like similar to 3 space dimensions or different? If different will it be ...
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1answer
57 views

Distorting the space-time fabric

If point masses could be generated in a controlled manner distorting the fabric of space-time objects could be made to move in any direction relative to each other and not simply attract as is ...
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1answer
38 views

Is turning space into time and time into space possible from an observer's perspective?

If the distinction between space and time depends on the reference frame, what reference frame should we use to perceive time as space and space as time?
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69 views

Black hole's singularity: Does it has to be multi-dimensional?

We assume that there is an infinite density at the center of a black hole. But we also know that if it was really infinite, it would apply an infinite gravitational force to masses even if they were ...
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75 views

Trouble in understanding spacetime

I have a problem in understanding spacetime. What i understood from the conversion of time to distance is that the interval between any two events is always the same for any observer. But how is that ...
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1answer
109 views

How can gravitational waves be detected when spacetime bends the instruments? [duplicate]

Apologies for the naive question, hoping someone with a proper physics background can explain this in layman's terms (as opposed to the more detailed answers at LIGO flawed by the identical expansion ...
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1answer
181 views

LIGO discovery: if the space “time” metric is changed, how is it measured? [duplicate]

Regarding the wonderful 2016 news about gravitational waves. Travel time in one arm of the LIGO is ~ 30μs. A gravitational wave affects the arm for some few hundred of these laps. Then for example ...
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75 views

Space-time and gravitational fields

I am reading a book by Carlo Rovelli, Seven Brief Lessons On Physics, and would like to check if I have understood something. Apologies if my question is badly phrased, feel free to edit where ...
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51 views

Empty space and velocity

If there was a universe without anything in it except you in a space rocket how you would you know what your velocity if you kept the engine on?
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122 views

Is causality a total order?

I've read that it is physically not possible to violate causality defined as a total order on the spacetime graph. So I was wondering if at least causality can be broked down to a partial order and if ...
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1answer
57 views

See behind the black hole

Why in this video does the 2nd black hole appears to change size and appear larger the farther away it gets? How can you see behind it? http://www.youtube.com/watch?v=ENd8Sz0AFOk
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113 views

What is the basic concept of four-dimensions in physics?

I have been reading a few books lately and browsing the internet for an explanation on the concept of "four-dimensional" space (or, space-time, as some of them have been calling it). But, what those ...
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82 views

Are there continuous spacetime events?

What is the formal definition of an event? According to Wikipedia, "an event is a point in spacetime (that is, a specific place and time) and the physical situation or occurrence associated with it." ...
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1answer
42 views

Calculate the relativity of time of an event occurred in different frames

Imagine we have a train which is moving with a velocity and there's an observer inside of that train and there is an observer that is outside of the train observing the train moving. There's a ball ...
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1answer
107 views

Is presuming that any linear uniform motion is transformed into another one sufficient to assume that Lorentz transformation must be linear?

I've read this condition in a script: The Lorentz transformation must be linear because any uniform motion must be a uniform motion in any inertial frame. All other proofs that I've read so far need ...
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1answer
125 views

Time dilation: linear or exponential or other?

As you near the speed of light, time slows for you relative to the world around you. So you would be traveling at more than one hour per hour. Is the rate of time slowing for you linear or exponential ...
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2answers
103 views

Frame dragging in general relativity versus classical vorticity concepts

Can anyone please clarify what one means by a vorticity in Space-Time? I'm aware of the vorticity in Fluid Mechanics. Is it the same vorticity that appears in General Relativity? Is vorticity related ...
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1answer
97 views

Does spaghettification really happen with conditions found close to a black hole?

This website tries to explain why the term spaghettification doesn't actually occur when something gets close to a black hole. The argument of the author is that the equations we use to predict the ...
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On a graph, can the compositions of both the x and y variables involve the unit time?

Time seems to be so fundamental to the calculations that we make, that it seems to be at the core of everything we do. Indeed, this is not just philosophically true, time is very often the x axis, by ...
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81 views

Understanding the nature of metric tensor [closed]

The metric tensor for a flat spatial manifold gives us length on object, or separation between two space points. Similarly, $g_{\mu \lambda} dx{^\mu} dx{^\lambda}$ gives separation between two space ...