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I understand that time has effects and that time can be slowed by gravity and such but I don't understand what time really is. Gravity is the bending of space and time but what is time? What causes time?
nuby said:Time perception is an interesting subject. Not sure if it ties into physics though... Quantum physics maybe?
Fredrik said:Regarding the definition of time...
We can define a coordinate system in Newtonian mechanics, SR and GR as a function [itex]x:M\rightarrow\mathbb R^4[/itex], where M is spacetime, and then define "coordinate time" as a component of that function. In SR and GR it's also necessary to define "proper time", which is the integral of [itex]\sqrt{-g_{\mu\nu}dx^\mu dx^\nu}[/itex] along a curve.
That takes care of the definitions in the mathematical models used in these three theories, but the theories must still include postulates that tell us how these things are related to what clock's measure. In Newtonian mechanics, clocks measure coordinate time. In SR and GR, a clock measures the proper time of the curve that represents its motion.
Fredrik said:Time is certainly more than that mathematical expression, but any answer to the question of what time "is", will always be in the form of a mathematical model and a set of instructions about how to use that model to make predictions about the real world. The best answer we have so far is the one provided by general relativity. The relevant "instruction about how to use the model to make predictions" says that what a clock measures is the proper time of the curve that represents the clock's motion. I don't think anyone has a better answer than that at this time.
Note that two definitions of time are needed. First we have to define time in a mathematical model (in this case as a certain integral), and then we have to define it operationally (as "what a clock measures"). Then we postulate how the two are related.
NoobixCube said:The direction of Time is shown in thermodynamics by the increase in entropy..
that's my two cents
confinement said:"What is time?" is not a proper question according to the use of the word "time." Examples of proper uses are:
"What time is it?"
"How much time do we have remaining?"
"At what time will it arrive?"
"How much time is this going to take?"
"I don't have time."
"This is a waste of time."
rosie said:Is time related to distance? I think what I'm asking is this. If I were to travel into space with a clock on board my ship and I were to look back at Earth - at differing distances I would see Earth moving in and out of daylight hours at differing frequencies. So the frequency of that transition in and out of daylight would depend on the distance I am away from earth. If the regularity of that flicker could be seen as say, every 10 minutes on my clock, but each flicker relates to an advance of 24 hours time on Earth then my distance from Earth could be calculated. The further the distance, then the faster the flicker into and out of daylight hours
It's as if everything has it's own time frame.
It makes we wonder what it would be like to ride an electron around the orbit of an atom. Would that time frame have any correspondence to daylight hours?
The exact relationship between time and distance is:rosie said:Is time related to distance? I think what I'm asking is this. If I were to travel into space with a clock on board my ship and I were to look back at Earth - at differing distances I would see Earth moving in and out of daylight hours at differing frequencies. So the frequency of that transition in and out of daylight would depend on the distance I am away from earth. If the regularity of that flicker could be seen as say, every 10 minutes on my clock, but each flicker relates to an advance of 24 hours time on Earth then my distance from Earth could be calculated. The further the distance, then the faster the flicker into and out of daylight hours. It's as if everything has it's own time frame.
It makes we wonder what it would be like to ride an electron around the orbit of an atom. Would that time frame have any correspondence to daylight hours?
And on and on. When we look at galaxies spinning in the distance - it's a given that we are looking at the galaxies past. But if we can see it describe an entire orbit in, say, 24 hours, then we are not only looking back into time but at contracted time. Like a fast forward. Nothing whatsoever to do with real time on that object.
No, you are not traveling at constant velocity. You are in orbit. In orbit, your velocity is constantly changing. You are not an inertial frame of reference. There is a fundamental difference between being on the Earth and in orbit around the earth.rosie said:...
Now I go up in a spaceship and orbit the Earth at a distance, say of 5000 miles. Now provided I can adjust my speed to the necessary I could position myself at precisely the point where the sun forever rises - early morning and stay in that orbit. Then my time frame is consistent with Earth clocks. And I'm traveling at a constant speed.
Now I decrease that speed and I'm now falling behind Earth's time frame. Now I increase my speed and I'm exceeding Earth's time frame. At each position I am traveling at a constant velocity.
rosie said:Here's my scale. I'm in a busy street. … Then I go to the top of a really tall building … my time frame is in fact also slower - marginally.
Now I go up in a spaceship and orbit the Earth at a distance, say of 5000 miles. Now provided I can adjust my speed to the necessary I could position myself at precisely the point where the sun forever rises - early morning and stay in that orbit. Then my time frame is consistent with Earth clocks.
If the big bang theory is substantially correct and all baryonic matter that makes up our present universe came into existence in the big bang, then possibly many of our laws of physics also came into existence at that time. But this does not mean that time or space would have had no meaning prior to the big bang. There could have been, and there could be, other universes that have spatial and temporal existence.cragar said:did time exist before the big bang?
Time is a concept that we use to measure the duration of events or the intervals between them. It is often described as the progression of events from the past, through the present, and into the future.
There is still much debate among scientists about whether time is a physical entity or simply a human construct. Some theories suggest that time is a fundamental property of the universe, while others argue that it is a byproduct of other physical phenomena.
We measure time using various units such as seconds, minutes, hours, days, and years. These units are based on the movements of celestial bodies such as the Earth's rotation and orbit around the sun. We also use devices such as clocks and watches to measure time more accurately.
While we can manipulate our perception of time through things like time dilation or time travel in science fiction, there is currently no scientific evidence to suggest that time can be physically manipulated or controlled.
One theory for this phenomenon is that as we age, our brains process information more efficiently, making it seem like time is passing faster. Additionally, as we experience more routine events, our brains don't store as many memories, making it feel like time is moving faster because we have fewer memories to look back on.