Questions tagged [space-time]
Questions regarding the 4-dimensional background structure of our universe.
189
questions
7
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3answers
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When we see the Sun, do we actually see its past?
The Sun's rays hit our eyes around 8 minutes after they are emitted from the Sun.
Does this mean that the Sun that we see is always the Sun as it was some 8 minutes before? I strongly think this must ...
0
votes
4answers
2k views
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....
9
votes
1answer
248 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 ...
5
votes
2answers
2k views
Why does the distance between Sun and Earth stay the same?
Well, we all know Sun gravity , makes the Space time curvature and space pushes the earth towards the Sun. But my question is "why the distance between the Sun and Earth is Same? Earth should have ...
4
votes
2answers
827 views
time on earth compared to completely stationary in space
I recently started trying to understand the theory of relativity and I have the following question. Because earth is orbiting the sun at approx 67,000 mph (and its my understanding time slows down ...
5
votes
2answers
264 views
How would Special relativity explain past-present-future if thinking about 13-billion-light-years distanced objects
Halo.
I'm interested in how would Special relativity comment on this:
Suppose there are 2 objects, A and B. They are 13 billion light years away from each other.
When the light from the B object ...
27
votes
2answers
5k views
Age of the universe and time dilation
Given our knowledge and the standard cosmological model, we estimate that the age of the universe is about 13.7 billion years old.
How much sense does it make to talk about the age of the universe as ...
6
votes
3answers
4k views
What is the relative time difference between us and a star system in outer layer of our galaxy?
Just curious to know what will be the time difference between someone living on the outer layer of our galaxy and us, considering the known facts that
Time is relative to gravity
Our sun goes around ...
3
votes
1answer
71 views
World line coordinate finiteness
If you trace two particles' world line backwards in time, according to current theory, both objects should converge at big bang.
Would both objects arrive there simultaneously?
Another way of asking ...
1
vote
1answer
105 views
the length of second, minute or hour, what defines the time of exo planetary bodies
we measure time based on earth and earth mass\gravity plays a role in the measurement ? so how and what would be time if not earth time on other exo planets since they will be having different mass/...
2
votes
1answer
312 views
How is space-time bent by black holes?
I just read When a star becomes a black hole, does its gravitational power become stronger? and it confused me a bit;
I always thought black holes are supermassive and that is why they bend space-...
4
votes
1answer
92 views
Perception of an objects history passing as an observer moves toward it
If a star is 20 light-years away and I look at it through a telescope, what I'm observing is what the star was doing 20 years ago yes? So, if I fix my sight on the star and move toward it (for example'...
2
votes
2answers
385 views
Why doesn't this paradox disprove (some) multiverse quantum gravitational theories?
As I understand it, one theory of the multiverse is that there are an infinite number of universes separated by small distances in other (than our observable 3/4) dimensions and that gravity is weak ...
3
votes
2answers
625 views
What is gravity really?
What is gravity? I want to know more than it being simply the "mysterious force" that attracts things to earth. Is it a particle, a wave, or something else entirely?
6
votes
1answer
222 views
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 ...
14
votes
3answers
12k views
Would time go by infinitely fast when crossing the event horizon of a black hole?
If you were to fall into a black hole, my understanding is that from your reference point, time would speed up (looking out to the rest of the universe), approaching infinity when approaching the ...
3
votes
1answer
164 views
Taking Advantage of Time Dilation
According to Einstein's theory of Special Relativity, one's speed in relation to a relatively stationary object would 'slow down' time on the moving object.
With this in mind, would it be possible to ...
2
votes
1answer
796 views
A day in earth, a thousand years somewhere else
By followig the laws of physics, is it possible, that in a place far far away that one day (at that place), is counted as 1000 years in the earth.
I am familiar with black holes having impact on time....
46
votes
8answers
9k views
Does matter accumulate just outside the event horizon of a black hole?
My understanding is that time slows and approaches stopping when approaching the event horizon of a black hole. I have seen this explained several places, including a brief explanation in the last ...
2
votes
1answer
155 views
How often do stars form?
There are many more stars in the universe than the years that the universe has been in existence, so wouldn't this mean that stars were/are forming at an astounding rate?
6
votes
3answers
1k views
What shape are black holes theorized to be?
I have always been curious about what black holes (or their event horizons) would look like if we could directly observe them. I notice that they tend to be depicted as flat holes in space but it ...
23
votes
4answers
4k views
What is a singularity? What is at the center of a black hole? Specifically regarding space-time
So because I can only really think of space-time in 2-dimensions like a sheet of something, my assumptions might be wrong to begin with. I was watching a YouTube video on black-holes and there was a ...
5
votes
2answers
265 views
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 ...
6
votes
2answers
4k views
Our universe the surface of a 4-dimensional sphere?
The cosmic microwave background that we observe uniformly around us is usually explained by assuming that our universe is the surface of a four dimensional sphere. That way the uniformity makes sense ...
4
votes
1answer
115 views
Einstein General relativity and bending of space [closed]
As Einstein's General relativity suggests that the space
time curves in the presence of matter, which is experimentally
proven too, this phenomenon also explains orbits. My question
is if the ...
5
votes
2answers
2k views
Why does time get slow near a black hole? [closed]
Why exactly does time get slow around a black hole? And does it provide a way to go into the future?
1
vote
1answer
467 views
Matter/mass exist into the space. Where does space exist? [duplicate]
It is said that before big bang there was nothing. Not even space/time. So, now where does space exists?
1
vote
1answer
134 views
traveling past the speed of light [closed]
According to the theory of relativity (If I understand correctly), nothing is supposed to be able to travel faster then the speed of light. I believe, to my limited knowledge and grasp of the concept, ...
10
votes
3answers
310 views
Is there anything special about our position in the galaxy thats necessary for life?
It's a fact that our planet's location from our parent star (among other factors) is of crucial importance to the existence of life. But can our position in the galaxy be considered a factor when ...
6
votes
1answer
169 views
Time dilation on an object circling earth
How would a receiver on Earth hear a radio transmission from an object circling earth at 99% of the speed of light for 24 hours. The transmission from the object circulating would be non-stop.
...
15
votes
4answers
19k views
What is the difference between our time and space time?
I am trying to understand the phenomenon of space-time. But, everything on internet seems to be too complicated for me since I do not have a background in physics. Can anyone give me simple ...
20
votes
5answers
23k views
By putting a mirror in space, would we be able to see into the past?
I only ask this because of how fast light travels. The question remains in the title. Why, or why not, would this work?
7
votes
2answers
427 views
Why do we have the cosmological constant?
Since the cosmological constant is not required to explain that the universe seem to be expanding, why do we have it?
What other factors cause us to have that constant?
Background:
Without the ...
7
votes
1answer
1k views
When we say a galaxy is 200 million light years away, does this account for the expansion of space in the time it took it's light to reach us?
When we see a distant galaxy, the light we are watching started it's journey millions of years ago. In all that time, space has been expanding, so if the initial distance was A, right now the distance ...
3
votes
2answers
23k views
What is the exact time Earth takes to revolve around its axis? [closed]
I read that our day is not exactly 24 hours long. If it is not then why weather seasons come at the same time (Summer, Winter, Autumn Spring) ? how it is equalized ?
Update: Sorry I could not make it ...
27
votes
5answers
8k views
Why is the observable Universe larger than its age would suggest?
The age of the Universe is estimated at 13.8 billion years, and current theory states nothing can exceed the speed of light, which can lead to the incorrect conclusion that the universe can't have a ...
6
votes
4answers
716 views
Can it be inferred that our cosmological horizon has increased over time?
If I am right, we can see only those stars that lie within our cosmological horizon, and there may or may not be any stars beyond that. Given last 150 years of using telescopes, and since then our ...
0
votes
3answers
174 views
Why does Astronomy still use the Anno Domini system for Time Synchronization
Since Time is such a valuable variable in the calculation of Astronomic movement why does the Astronomy Community still rely on the the 6th Century Anno Domini system developed by Dionysius Exiguus to ...
6
votes
2answers
553 views
Why Do Planets Revolve Faster When they Are Closer to Their Parent Star?
According to Kepler's second law: A planet sweeps out equal areas in equal times (A simple definition). This means that if the orbit is somewhat eccentric, the planet will move faster when on the ...
