Space and time Definition and 140 Threads

In physics, spacetime is any mathematical model which fuses the three dimensions of space and the one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why different observers perceive differently where and when events occur.
Until the 20th century, it was assumed that the three-dimensional geometry of the universe (its spatial expression in terms of coordinates, distances, and directions) was independent of one-dimensional time. The famous physicist Albert Einstein helped develop the idea of space-time as part of his theory of relativity. Prior to his pioneering work, scientists had two separate theories to explain physical phenomena: Isaac Newton's laws of physics described the motion of massive objects, while James Clerk Maxwell's electromagnetic models explained the properties of light. However, in 1905, Albert Einstein based a work on special relativity on two postulates:

The laws of physics are invariant (i.e., identical) in all inertial systems (i.e., non-accelerating frames of reference)
The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.The logical consequence of taking these postulates together is the inseparable joining together of the four dimensions—hitherto assumed as independent—of space and time. Many counterintuitive consequences emerge: in addition to being independent of the motion of the light source, the speed of light is constant regardless of the frame of reference in which it is measured; the distances and even temporal ordering of pairs of events change when measured in different inertial frames of reference (this is the relativity of simultaneity); and the linear additivity of velocities no longer holds true.
Einstein framed his theory in terms of kinematics (the study of moving bodies). His theory was an advance over Lorentz's 1904 theory of electromagnetic phenomena and Poincaré's electrodynamic theory. Although these theories included equations identical to those that Einstein introduced (i.e., the Lorentz transformation), they were essentially ad hoc models proposed to explain the results of various experiments—including the famous Michelson–Morley interferometer experiment—that were extremely difficult to fit into existing paradigms.
In 1908, Hermann Minkowski—once one of the math professors of a young Einstein in Zürich—presented a geometric interpretation of special relativity that fused time and the three spatial dimensions of space into a single four-dimensional continuum now known as Minkowski space. A key feature of this interpretation is the formal definition of the spacetime interval. Although measurements of distance and time between events differ for measurements made in different reference frames, the spacetime interval is independent of the inertial frame of reference in which they are recorded.Minkowski's geometric interpretation of relativity was to prove vital to Einstein's development of his 1915 general theory of relativity, wherein he showed how mass and energy curve flat spacetime into a pseudo-Riemannian manifold.

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  1. S

    B Exploring the Relationship Between Earth's Mass and Time: Debunking the Myth

    Is it true that the time increase (24 hrs becomes 25 or 26 or..)when the mass of Earth is increase? ??
  2. Deepak K Kapur

    B Mechanism of Curvature of Space: Does it Happen Instantly?

    Hi all, How does matter curve space (what's the mechanism)? Does this Curvature happen instantaneously or does it happen at light speed? Thanks in advance.
  3. E

    B Is it possible to reach the singularity?

    The question is; After an object goes through the event horizon, is it possible for the object to reach the singularity? As far as i know, singularity, bends space down and actually space moves faster than light towards the singularity. But what tells us that the singularity's bending has a...
  4. G

    I The name of the 3+1 metric where time is normal to space?

    I am interested in looking at the metric where time is everywhere normal to space, so gta=0 everywhere, where t is the time coordinate and 'a' is any of the space coordinates. I'm finding it hard to look up in the literature: does it have a name that I can search for? My main interest is in...
  5. V

    B Exploring the Expansion of Space & Time

    We are told that space is expanding and that the rate of expansion is speeding up. However, as relativity shows that space and time are inextricably linked, does this mean that time is expanding too?
  6. Dimani4

    I Classical Newtonian Physics: Space & Time Independence

    Hi folks, Tell me please why in classical Newtonian physics one can say that the space and time are independent? But we have equations of motion which clearly show this dependence (x=Vt; x=x0+1/2at^2+v0t). Thank you.
  7. S

    B Photography in 4D World: Time & Space

    If time is a dimension, what would be the dimension of a photograph in such a space?
  8. N

    B Is dark/vacuum potential energy infinite?

    And virtual particles potential energy is infinite too? As more and more dark energy is created does this mean that the potential energy of dark energy is infinite? Does that happen for virtual particles in vacuum and vacuum energy too?
  9. N

    I Is vacuum energy infinite? If it is, how and why?

    https://en.m.wikipedia.org/wiki/Vacuum_energy And it is this type of energy dark energy or a form of it?
  10. J

    I Spacetime and effects of being super close to the Sun

    I have been wondering about space time and how it works like satillites putting corrections in there clocks by a few nano seconds a day because of gravity or lack of it! But I have also wondered about the effects of being super close to the sun and time that we observe there looking back at...
  11. P

    I Does Space-Time Exist Without Energy?

    If there was no mass/energy would space time still exist? In other words, does on space time only exist because of an interaction between two points of energy?
  12. A

    I Quasars: What Metric Should You Use?

    Hello I just got interested into quasars and I have a question:What metric do you use for quasars?
  13. Erenjaeger

    Age difference problem due to space travel

    Homework Statement The identical twins Speedo and Goslo join a migration from the Earth to Planet X, 19.0 ly away in a reference frame in which both planets are at rest. The twins, of the same age, depart at the same moment on different spacecraft . Speedo's spacecraft travels steadily at...
  14. M

    I Physics & Objects Beyond Space & Time: Big Bang Singularity & Black Holes

    Is there anything in all of physics about objects "beyond" or "outside" space and time? Do black holes qualify for such a description? What about the hypothetical Big Bang Singularity?
  15. willem govaerts

    I Did the Big Bang separate space and time

    Hello everyone, I've come across a problem that i can't solve but which i find really interesting. I'm not here to ask where the big bang was because I've already read enough about that is was a singularity, so you could say that is was everywhere. But here my problem comes in, if the big bang...
  16. Lars Hansen

    B Voyager 1: How Long Can We Communicate?

    For how long will we still be able to communicate with the amazing Voyager 1?
  17. T

    I Space and time as fields of mass-energy

    In my post graduate course, several years now, our professor in field theory have mentioned that in field theory the fields of mass-energy seem to be space and time themselves, like electric and magnetic fields in ElectroMagnetism. Specificaly he said that "the problem is that in...
  18. Zahidur

    Does light always travel at light speed?

    I've been told contradicting ideas about this. I've been told that light doesn't travel at a constant speed everywhere (i.e. light slowing down in speed after entering a more dense medium). However, I've also read that light speed is constant everywhere (i.e. if you could travel close to the...
  19. A

    I Deriving Einstein's Relativity Postulates from Minkowski Spacetime

    Does the constancy of the speed of light for all observers naturally emerge from the Minkowski spacetime metric? Do Einstein's two postulates of relativity emerge from the Minkowski spacetime metric? Suppose we begin with Minkowski spacetime and the Minkoswki metric...
  20. G

    Language that cannot be decided by a TM using space O(log n)

    Homework Statement 1. Give a language L that cannot be decided by a TM using space O(log n) and time less than n on inputs of length n. The language L should be decidable by some TM. Assume the TM has a binary input alphabet. Homework Equations Undecidability, Turing Machines, Languages...
  21. Tollendal

    Are space and time really quantized?

    Quantum Theory perhaps isn't really quantic, as It seems to me there is an underlying continuity. There are even some reasons to suppose that in Planck scale we will not see the discontinuity most of us expect. Professor's Craig Hogan superinterferometer is opperating in Fermilab; soon we will...
  22. R

    Are spatial and temporal dimensions interchangeable?

    According to general relativity, time is a dimension, one of four dimensions that form 4D spacetime - a structure which is mathematically symmetrical and homogeneous. Should not all four dimensions, therefore, be mathematically interchangeable? Assuming that we are 3-dimensional bodies...
  23. M

    Black holes swallow space and time?

    I have always been fascinated by black holes And I am sure that all the answers in physics are hidden in black holes... According to Einstein nothing can go faster than the speed of light, but nothing can escape black holes not even the light. Would it mean that the gravity resulting by a fall...
  24. DastardlyBliss

    Why is the fabric of space and time always portrayed flat?

    The concept of the fabric of time and space is confusing to me. I understand that an object with large mass can warp it, but that only makes sense to me if the fabric had only two spatial dimensions (assuming no warps). The space-time fabric is always explained visually as a flat plane, but...
  25. E

    What Was Space and Time Before the Big Bang?

    what was space and time before the big bang thank you
  26. AshUchiha

    Bending of space and time, is it true?

    I've heard many theories like object with mass bends the space-time and causes object to fall for it. If that's true then the Earth should end up being colliding with the Sun right? , because the Earth's mass is 1/1 million of that of Sun according to my knowledge. If we take Earth's mass as m...
  27. Q

    Could the universe exist without space and time?

    I know that in relativity space and time form the fabric of the universe, and everything exists in space time, so I keep thinking, could the universe exist without space and time, could anything exist? Is there any idea in theoretical physics where the universe could exist without space and...
  28. I

    Interplay of space and time in Spacetime invariant interval

    According to Special Relativity, the same event could have a different time duration and a different space extension for different observers, depending on their frame of reference. Relativity subsequently introduced the the notions of Spacetime as a continuum ( as opposed to the classical...
  29. N

    How did Einstein know the properties of space and time

    How did he figure out the many properties of the Universe such as time dilation/relativity and energy matter equivalence and his numerous other contributions. This might be a dumb question but was this all just done on paper? I don't recall reading that Einstein ever conducted experiments...
  30. nomadreid

    Inside event horizon, space and time are reversed. How, precisely ?

    In "The Hidden Reality", Brian Greene mentions almost off-hand that inside the event horizon of a black hole, space and time are reversed. But no details are given. What, precisely, does this mean? Does it mean that in one's equations, if one is using a (-,-,-,+) signature, then everything...
  31. P

    How Does Mass Affect the Fabric of Space-Time?

    I'll ask that you forgive me if my question seems to "basic" or simple for some of the more professional posters. I am simply a physics/cosmology enthusiast who has been captured by it all since I was a child, however, there is one issue that as I continue to learn more is bothering me. I...
  32. M

    Relativity: Space & Time on a Tempurpedic Mattress?

    In relativity spacetime is usually visualized by placing something on a stretchable fabric of some sort. The object placed on the fabric will bend the fabric, just as a planet or star would in real space. Time can be manipulated when something extremely massive like a black hole is in space. But...
  33. K

    Assume Classical Ideas of Space and Time (Ether)

    Homework Statement My question is part C of problem 1.9: http://facultyfiles.deanza.edu/gems/lunaeduardo/4DHW.PDF Homework Equations Pythagorean Theorem? The Attempt at a Solution I have c vector of lightwave going upwards and v going rightwards forming a right angle with the other...
  34. R

    How do we know space and time are related?

    I know the general theory as proposed by Einstein but how has it been proved beyond a reasonable doubt?
  35. E

    What is the difference between separation in space and separation in time?

    I do not understand the difference between separation in space and separation in time. Could someone please explain the following positions to me? I would be very thankful and appreciative if so. Position of event 1: Separation in time (lightyears) = 20. Separation in space (lightyears) =...
  36. B

    What is a Vacuum in General Relativity?

    Hi what constitutes a vacuum? I mean it has to be made of something, since it it part of the space time continuum. In school you learn that a vacuum is empty space or area without matter, but it occurs to me that a vacuum must be made of something and there must be something there. What is it...
  37. A

    Is spacetime not the same as space and time ?

    is spacetime not the same as space and time ?? please explain what's the difference between "spacetime" and, space and time ? i heard space has it's own properties and time has it's own properties but "spacetime" has completely different properties. Please explain. Thanks
  38. K

    Linear equations and homogeneity of space and time

    Einstein, in his paper "On the Electrodynamics of Moving Bodies", part 1, sec. 3, writes: "Primarily it is clear that on account of the property of homogeneity which we ascribe to time and space, the equations must be linear." What has the homogeneity of space and time to do with the degree of...
  39. G

    Since space and time are relative shouldn't matter and energy be also?

    Its known that the speed of light is constant...(if you emit a light Eastward while your physically traveling East c will still be the same as if you were still) but also, through an experiment i am imagining, the speed of matter should be relative as well...(if your traveling Eastward and you...
  40. A

    How comes the big bang singularity didn't need space and time?

    Obviously before the big bang there was no space and no time, so how comes the big bang singularity itself existed without space and time? do black holes' singularities not need space and time to exist too? or at least in order for them to come and exist there has to be space and time at first place
  41. D

    What is Space and Time in String Theory?

    --I understand that the original basis of string theory was as explanation for the ontological origin quanta . I have a few questions: 1) What is the origin and material make-up of the string? (How can we avoid the metaphysical pit-fall of an infinite regress in regards the ontological...
  42. D

    What is the nature of space and time?

    Are space and time things to themselves? Or are they just what things occur in? For example, fish occur in water, but water is a thing to itself and things occur in it (e.g. "fish"). Are space and time the same way?
  43. B

    Exploring the Relationship Between Space and Time

    Greetings! I'm new coming to this page but I have a question whose answer goes beyond my understanding of physics...really,even the question goes beyond my understanding but I feel comfortable enough to ask the question, just forgive me if I use the wrong wording... I've read and heard about...
  44. J

    I have been told space and time are illusions. What does that mean?

    Hello there, Some time ago, I saw a talk by a nobel prize winner. He quoted two other scientists, one was Witten, the other I cannot remember. Since that day I have imagined that it must be correct. Why? Because relativity predicts singularities are nonphysical nonsense. Yet, we can...
  45. A

    Divide in space and time component

    For -\frac{1} {4} F_{\mu\nu} F^{\mu\nu} We can write -\frac{1} {4} F_{i j} F^{ij} -\frac{1}{2}F_{0i} F^{0i} Where F_{\mu\nu} \equiv \partial_\mu W_\nu-\partial_\nu W\mu If there are 3 indices how can I separate them like this? I want to separate \frac{1} {12} G_{\mu\nu\rho}...
  46. D

    Are space and time really quantized?

    Is it really true that space and time are quantized or is it just a mathematical abstraction? If it is true, then what happens to this quantization under special relativity and general relativity? Is the minimum quantized distance different at the surface of a black hole than it is in the middle...
  47. D

    Tachyon - assymetry between space and time

    Say, we have empty flat spacetime; there is a lab frame and 2 particles - bradyon and tachyon. While movement of bradyon is stable, tachyon is believed to lose energy because of Cherenkov radiation: http://en.wikipedia.org/wiki/Tachyon#Cherenkov_radiation if it is charged and even if it is...
  48. T

    Exploring the Nature of Space and Time

    In the context of all the very latest theories of: The expansion of the universe, The effects of dark matter and energy, Gravitation and the other fundermental forces of nature, General and Special Relativity, Black hole singularities, Inflation, The size of the whole universe and...
  49. Z

    How much matter can you put in space and time?

    How much matter or energy density can be allowed in space and time before it closes in on itself?
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