Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.

Questions tagged [space-time]

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

Filter by
Sorted by
Tagged with
2
votes
1answer
144 views

Based off of the study that found the universe has a positive curvature, how big would the whole universe be?

This study found that the universe has a positive curvature https://www.nature.com/articles/s41550-019-0906-9. I didn't really want to buy it and see if it says how big the universe might be. I know ...
0
votes
0answers
33 views

Whats the time dilation difference between the earths reference and (near) the milky way galaxy central black hole? [duplicate]

How much difference in time is there between our time of reference and very near the black hole at the center of our galaxy. I was trying to get answer in terms of something like "1 year in here ...
4
votes
2answers
106 views

Neutron star size in different reference frames

What is the estimated size of neutron stars observed in their reference frame and in our reference frame? That is, how bent is space-time around neutron stars?
9
votes
3answers
2k views

How is time defined in astronomy?

I was amazed when my teacher told me that in space, time is define as a coordinate. It means we can define something with a four coordinate system with "negative time" $-t$ as easily as we can say $-...
2
votes
3answers
149 views

How does time work beyond the cosmic event horizon?

The faster you move through space, the slower you move through time - the calculations show that as you approach lightspeed, time comes to a standstill. How does time work beyond the cosmic event ...
3
votes
0answers
40 views

Why does the outside edge of a Kerr black hole ergosphere rotate at the same speed as the inner edge?

Reading through the Wikipedia on a Kerr black hole ergosphere, and this nice question on the maximal spin rate of a black hole leads me to ask: why does the outer edge of the ergosphere rotate at the ...
1
vote
1answer
134 views

Do gravitationally bound (e.g. orbiting) objects really resist the expansion of space?

Thinking about the expansion of space, it is commonly explained that gravitationally bound objects (like galaxies and galaxy clusters) will not be affected by the expansion of space (dark energy). I ...
0
votes
1answer
203 views

Will intergalactic travel be impossible in roughly 15 billion years?

Even if we (or aliens somewhere in the universe living at that time) somehow invent something that can go just short of the speed of light, will intergalactic travel still be impossible in roughly 15 ...
0
votes
3answers
160 views

How can we see stars if they are hundred years of light far from the Earth?

So the right question is, is the light years counted from that second when you look up to the sky? If that so, how can we see the stars from the telescope (which I think it starts when you put your ...
-4
votes
1answer
174 views

What is the time dilation less a magnetic field?

Does time dilation drop off like a gravity or does resemble a magnetic field model? Could a smaller body with a magnetic field have more time dilation then a larger body without and to what degree?
7
votes
1answer
186 views

Universe is expanding, why doesn't time expand with it?

Reading this response When the universe expands does it create new space, matter, or something else? I understand Universe is not expanding like if it is stretching its space, but it is actually ...
3
votes
3answers
246 views

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 ...
1
vote
0answers
114 views

How does a spinning black hole affect space-time compared to a non-spinning black hole?

I often see questions on this site that only apply to non-spinning black holes and often wonder how the answer would be different for a spinning black hole. As the title says, what are the major ...
3
votes
1answer
124 views

Discontinuity in space-time

What I understood about it till now is that space-time fabric is kind of broken there. Please tell me whether I am correct. If it's true then does it mean that perception of time will stop there? I ...
0
votes
1answer
55 views

What would happen if space-time began to contract? [closed]

Assume that the expansion of the universe stops and it starts to contract again. What would happen? Would only distances between objects get smaller, or are there other effects we can expect?
1
vote
1answer
85 views

Looking at the Expanding Universe through the lens of relativity [closed]

The basis and most observable metric for how the universe is understood to be expanding at an accelerating rate is the red shift in observable light. I am assuming it has been thought about or maybe ...
2
votes
1answer
92 views

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 ...
7
votes
3answers
2k views

Can we track matter through time by looking at different depths in space?

If we look back far enough we can see all the origins of the universe, so is it possible, even if not feasible, that we could trace the history of some matter as it moves through space-time? I want to ...
3
votes
0answers
68 views

The nature of cosmological inflation — unfolding dimensions?

While the paradigm of cosmological inflation is well established, the nature of the inflation is not known and is tackled by introduction of a hypothetical "inflaton" field. I was wondering if there ...
2
votes
3answers
170 views

Is space a thing? [closed]

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 ...
5
votes
2answers
102 views

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 ...
0
votes
2answers
133 views

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)....
1
vote
1answer
84 views

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 ...
1
vote
1answer
69 views

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 ...
3
votes
2answers
181 views

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 ...
2
votes
0answers
39 views

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 ...
0
votes
1answer
72 views

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?
3
votes
2answers
182 views

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?
-1
votes
2answers
84 views

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 ...
1
vote
2answers
84 views

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 ...
1
vote
1answer
83 views

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 ...
2
votes
1answer
92 views

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 ...
1
vote
2answers
183 views

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....
0
votes
1answer
87 views

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 ...
4
votes
1answer
596 views

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 ...
1
vote
2answers
93 views

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?
5
votes
1answer
947 views

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 ...
0
votes
2answers
313 views

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 ...
0
votes
2answers
112 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 ...
2
votes
1answer
138 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 ...
2
votes
3answers
233 views

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 ...
-2
votes
1answer
392 views

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?
2
votes
2answers
304 views

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 ...
5
votes
0answers
179 views

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? ...
0
votes
1answer
75 views

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 ...
1
vote
1answer
85 views

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-...
2
votes
1answer
154 views

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 ...
1
vote
2answers
913 views

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 ...
2
votes
1answer
67 views

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 ...
0
votes
1answer
80 views

Time travel in past and future [closed]

Why it is not even theoretically possible to travel in past but possible to travel in future ?