I don't believe that reversal is available to us. Saying that the polarity of gravity causes time to move forward is equivalent to saying that the forward direction of time causes gravity to have a certain polarity. Either way, I don't believe that reversal is possible.
I have a problem with the nomenclature "arrow of time" because it insinuates that the arrow can point the other way. Time cannot go backwards. You can slow it down to a virtual standstill but it will never go backwards. Also, time in the sense of changing states is real. Only the measurement of it is arbitrary and a construct of the human mind. If humans did not exist stars would still age and die out, the Cubs would still never ever win another World Series and the Bears will always suck for eternity the last two being quite amazing since they can accomplish that even without human existence but they both suck so bad that they defy natural laws of the universe.
Apparently there is no contraction in the multiverse theory of endless inflation. Each universe ends its life cycle as empty, flat space in a state of high entropy, from which new universes are born. The arrow of time correlates with entropy as well as expansion. If, as some suggest, the universe is winding up instead of winding down, it could indicate that entropy is being buffered, and the universe is receiving input from without as could be expected since it is not a closed system. Whatever happens outside of our universe should be contemplated without the perspective of actually being there. Then we wouldn't have an 'our time' out there to ponder. Thus "step outside" has to be taken as a figure of speech. I won't even try to tackle those issues.
Apparently that's how it is. Albrecht tried to take apart Einstein's unification of time and space but found that the attempt causes physics to come undone. The arbitrary clock methods turn the laws of physics into ambiguous assortments. All physical things are defined by time, and there are no overall fundamental laws of physics, just the ones unique to one particular universe at a certain point of time in its history. The laws of the universe are determined as the universe evolves.
I admit I use my phone calendar to remind me about some dates but I don't need to know the day of the week or time of the day. I frequently check for mail on Sundays and of course find nothing but no big deal. Long ago I could guess time based on which TV programs we would be watching, but now that we record everything and play back later, I'm clueless...
When I fall asleep on the Barcalounger time is still moving forward. Earth is moving and the solar system is moving and the galaxy is moving and the Universe is moving. But we only consider time on the movement of Earth and ignore the movement of everything else. This is why Earth time is meaningless on Jupiter. If Earth astronauts fly to another solar system, and when greeted by extra's and asked how long our trip was, our answer in Earth time will be 100% meaningless to them.
No. I agree with your first two sentences. I don't agree that people generally consider time only in regard to the motion of the planet Earth. That is certainly the standard around which we have established units of measurement, but time is time no matter which units of measurement we use. Of course the amount of time that passes within an Earth year doesn't equal the amount of time that passes within a Jupiter year, but that doesn't render the year a useless metric. You simply have to employ a conversion factor to relate an Earth year to a Jupiter year. That concept is really no different than converting yards to meters.
How can you employ a 'conversion' factor when as a space traveler you will never know a new planets time system? And again the question...as a space traveler, during your trip, what time system will you be using? Regarding people on Earth, I doubt 50%+ don't know what our time system is based on so if this is true then most people do not consider time to the motion of the Earth. Time systems, all of which will differ, are meaningless to all others who do not understand your time system. Regarding your yards-to-meters example...Americans are clueless about the metric system so you provided a great example why everyone needs to be on the same measurement system...there are several measurement systems...
Time is merely a function of motion, just as is distance. Units of measurement are arbitrary, but the relevant natural laws of physics remain constant, regardless of the units that are used to describe them. If most people are ignorant of this, it doesn't really change the underlying truth. 55 MPH designates a particular velocity that remains the same even if it is described as 88.5139 KPH by the observer.
As big E pointed out time is relative (to the person doing the observing and someone observing the observer). Ordinarily this difference between the observer and the observed is not noticeable, but speed things up to relativistic velocities (99.9 speed of c and above) and that claim by Einstein becomes VERY obvious! The observer that stays on earth or the moon etc, watches as his brother rockets away on a near light speed spaceship. If the brother in the spacecraft could see his earthly bros watch the dial would spin faster and faster, while the earthy brother would only see it spinning normally. By the time the space faring brother returns his brother would be an old man (if still alive) while his brother would only have aged a year or two! As I, said (and Einstein proved) ; " but speed things up to relativistic velocities (99.9 speed of c and above) and that claim by Einstein becomes VERY obvious! " Of course the speed of the space craft and length of the time of the trip into deep space would determine the age of the two brothers. In fact if the space craft could attain a very high velocity thousands or hundreds of thousands of years on earth would pass for every second the craft was accelerating away from earth! Weird indeed! reva
You could use earth years or you could use a star date. You could use any system you wanted. There are two kinds of time. Intuitive time the kind that seems to flow, physicists use an upper case T for it. Then there is space-time which is the fabric of our universe, its represented by a lower case t. Most of the replies in this thread have been discussing T, not t, and that is the confusion. Unless we are talking about space time it really makes no difference how someone defines time. I think he was referencing that because Jupiter takes longer to orbit the sun the year is longer but only in T (intuitive ) time. Earth time and Jupiter time is the same when experienced by a earth person using a Jupiter year or a Saturn year. However t time is altered by the more powerful gravity of Jupiter, not enough to notice really but time really does run slower on Jupiter if a human body could handle the immense gravity and radiation. However if a human was standing on the event horizon and stepped over the imaginary line time would stop inside the event horizon. An observer watching him would say he froze when he stepped inside the horizon and would appear to hover there forever. Gravity is so immense in a black hole time stops. reva
Think about that. OM said ;"5PM on Earth has no meaning on Jupiter or Alpha Centauri, etc. If there was an interplanetary spacecraft and they called both Earth and Jupiter to get the time, they would receive two totally different times...so what time would it actually be on that spacecraft? " Spacecraft time would not be necessary because you and crew could use earth time. However If you were the spacecraft captain you could make up a system like seen on star trek and use a star date for spacecraft time. So if you were an earth person on the spacecraft you could choose spacecraft time ie 3000.25.12 Orion space craft star date. Or you could chose earth time ie; December 25 2014. Or if for some reason you wanted to know what time it was on Jupiter or Saturn or Pluto etc it would be what ever time it was on those systems. All the above is discussing intuitive time. reva
OK, so "dark matter" is supposed to have a negative gravity, a push against all matter. Would time travel backward inside it's gravity well, uh, I mean, hill? Also, gravity has long been known to speed up time. The tests with the atomic clocks and the airplane proved that.
I don't know if dark matter has negative gravity, but if it did than it would probably have negative time as well. But I don't think it works that way, and anyway we don't know much about dark matter.
You were correct in using the term gravity well because mass distorts the fabric of space time. However time doesn't run backwards according to every theory I have seen. It stops completely because say in a black hole its gravity is infinite, Even light can not attain an fast enough escape velocity and can not get out of a black holes gravity well. Gravity/Mass, and velocity slows down time not speeds it up. Velocity effects time because the faster you or an object is going the slower its time would run according to an observer. That's because as velocity increases so does its mass and its so its gravity. Time runs slower for someone on top of mount Everest by a miniscule amount compared to someone at sea level, because of the distance from the center of earths mass is greater for the observer on top, hence the observer and the observed showing that time is indeed relative. Mass distorts the space time fabric so a black hole for example having infinite gravity causes time to stop when one goes past the event horizon. Likewise as an object is accelerated towards 100% light speed its mass increases the faster it goes till eventually its mass becomes infinite and all the energy in the universe could not speed it up more than light speed. I have already said all of the above in this thread, anyone that disagrees is welcome to take issue with my words. If everyone agrees, then its all good! reva
They only remain constant relative to local people...mph or miles per Earth hour are meaningless on Jupiter. The time system depends on what is being measured at local levels. Once again I ask; those flying on a spaceship in interstellar space or even within our Solar system...what time system will they be using during their voyage? I agree that perhaps some things in the Universe might remain constant, like the SOL, however, every local time system will have a unique language and calculation when they express the SOL. A 'light year' we talk about applies only to Earth and would be unknown to those living on Jupiter. Although it was fiction, on Star Trek, they talk about 'star date 75-2020202-22 and I think someone has actually created a time system something like this that perhaps begins at the BB?? The only question is what 'units' are being used to start the count from the BB?
This would mean anything that can travel near 'c' will never have anything to come home to in terms of family and friends, etc. It's a one-way ticket leaving behind the present and returning far into the future...right? This kind of indicates that human travel at these speeds would not be practical or kind. But all along I get the idea that time is relative to the observer. I still don't understand what time system would be used on an interstellar craft?
So does this mean, if you are far out in space, without being pulled by gravity, weightless, that time stops? Since gravity is not pulling it? LOL. Would anti gravity then run time backwards? LOL
When we observe a light which is 10 light-years away from us, that light left it's source 10 years ago...right? If we communicate with someone 10 light--years away, we say hello then 10 years later they hear us say hello then they respond by saying hi and we hear hi another 10 years later...so to say hello and hi takes 20 Earth years. Both locations would have aged 20 Earth years so if two people were each 30 years old, by the time they say hello and hi each would then be 50 years old...right? But if two 30 year old people sent the 'hello' message, and one stayed on Earth while the other traveled in a spacecraft at the SOL for ten years, the space traveler could almost arrive in time to answer the original call. If that space traveler answered then said 'hi' back to the person on Earth, then got into that spacecraft and traveled at the SOL back to Earth, he could again arrive in time to receive the 'hi' call. BUT, instead of both being 20 years older you're saying the person who remained on Earth might be dead and gone?
