Topic: Someone please explain time to me..

[Clark Kent]

I'm watching SG-1- a rerun where they are locked into a planet through their wormhole that is being swallowed up by a black hole. 
No, here is what I'd like to know:
How exactly does time work?  What causes it?
If extreme gravity decellerates time, does that mean that pilots experiencing high G's actually slow down in a HET, or does centrifugal/centripatal force not work for this? 
When one leaves our solar system, does time speed up for them?  What about when they leave the planet?

[Sirgod]

Clark, give me a few Days to try to Explain Those things too you, But I'm completly swamped this weekend. However the Effects of Gravity, To my understanding has no Effect on Time Dilation, I think your confusing this with a Curved Space Time. Gravity does have a Very slight effect on Bending Light, However the Speed of Light in our deminsion does not Equate to the Possibility of FTL Particles, and other Matter.

In fact the Speed of Light could very well be considered Exceptionaly slow to those Particles with a Negative Mass.

Stephen trying to shake out the Old Texas U cobwebs, and Sudarshans work.

[Clark Kent]

I think I will be patient, since what you are saying, I'm barely comprehending...
Thanks

[Nemesis]

Gravity does affect time.  The first GPS satellites were put up with the ability to compensate for the time difference of the lower gravitational field at thier altitude, this ability was turned off initially because the people with the final say did not believe the affect would be as large as predicted.  They had to turn the compensation on to make GPS satellites accurate.

The adjustment does not only take into account the affect of lower gravity allowing time to be slightly faster than at the surface of the Earth (by 10's of microseconds per day) but also takes into account the slowing of time by the velocity of the satellite (slowed by several microseconds per day). 

So both high velocity and the local gravity field do slow time.   The higher the velocity or gravity field the more intense the dilation.   I doubt that  a pilot of any known aircraft would experience enough time dilation to be measurable.  The ISS astornauts likely do and the lunar astronauts did (but I don't know if it was measurable then, just that it is measurable now)

As to what time actually is I couldn't even speculate. 

Oddly enough those probes that have reached the edges of the solar system (since being launched in the 1970's) find that they are decelerating slower than predicted.   Whether this is because gravity is weaker, lower density of space dust, time differnces compared to scientists forcasts doesn't seem to have been conclusively decided.

I am sure that Stephen can give you far more information than I can.   But maybe this will tide you over till he can respond fully.

The Stargate episode if I recall it correctly had Sam observing that the time dilation was far higher than modern science predicts and neither the gravity field nor the temporal effects should have penetrated the wormhole.  Sam (and others) commenting on how various alien techs break known science is one of the things that I like about Stargate.  They carefully avoided the impression of talking about real science when they went off into technobabble.

[Firehawk]

Well here is a little reading on time dilation for you.

"A geometry that includes the three dimensions and a fourth dimension
of time. In Newtonian physics, space and time are considered as
separate entities and whether or not events are simultaneous is a
matter that is regarded as obvious to any competent observer. In
Einstein's concept of the physical universe, based on a system of
geometry devised by H. Minkowski, space and time are regarded as
entwined, so that two observers in relative motion could disagree
regarding the simultaneity of distant events. In Minkowski's geometry,
an event is identified by a world point in a four-dimensional
continuum."

Now, that's relatively dense stuff. Here's what it means -- at least
as far as Einstein and Minkowski are concerned. Two people who are in
the same relative frame of reference (moving at about the same speed
in the same direction) will experience time the same way. So, if you
and your best friend got on a space ship that started travelling at
almost the speed of light, the two of you would experience time at
exactly the same rate. And, assuming your watches were synchronized,
they would confirm your suspicions.

However, when two observers are in different frames of reference,
suddenly time might seem very different. You see, the faster a person
travels through space/time, relative to another observer, the more
time seems to slow down. If you and your friend go travelling at
nearly the speed of light in your spaceship, it might seem to the two
of you that only one year passes between taking off and returning.
However, because of your great speed relative to Earth, the people
back on Earth will experience time more quickly than you do, so that
decades might have passed before you arrived. In physics, this is
called Time Dilation, and it's defined this way:

"The principle, predicted by Einstein's special theory of relativity,
that intervals of time are not absolute but are relative to the motion
of the observers. If two identical clocks are synchronised and placed
side by side in an inertial frame of reference they will read the same
time for as long as they both remain side by side. However, if one of
the clocks has a velocity relative to the other, the travelling clock
will show, to that observer, that less time has elapsed than the
stationary clock. The principle has been verified in a number of ways;
for example, by comparing the lifetimes of fast muons, which increase
with the speed of particles to an extent predicted by this factor."

Now, time dilation takes place at high speed, but it also takes place
in regions of intensely high gravitational pull. This is because
gravity is 'created' by the mass of an object literally causing
space/time near it to curve. This curvature occurs with all mass --
you create a very small gravitational pull by your very existence and
so do I. Because time and space are entangled together, frames of
reference are changed by high gravity the same way they're changed by
high speed. Now, in most normal gravitational fields, you'll never
notice the difference. No one on the Moon seems to be in a different
rate of time than someone on Earth, for example, even though the Moon
only has one sixth the gravity of Earth. But, when you get close to a
black hole, the gravity changes become vastly different. As one
approaches the singularity -- the 'hole' itself -- the shift in
gravity becomes so tremendous that time slows down intensely, to the
point that it seems to stop entirely, from the point of view of a
hypothetical observer outside the black hole's event horizon.
Literally billions of years could pass outside before the ship you
were in went forward even an inch towards the actual singularity.

However, as far as you're concerned inside the space ship, time will
still work normally, and your clock will still tick once a second.
After all, you and the clock will share a frame of reference, so as
far as you're concerned, time will still be working normally. However,
looking back out at the rest of the universe you would see their time
speed up incredibly or even infinitely fast.

Of course, the gravity would tear you and your ship apart long before
any question of you stopping in time would come up, but that's neither
here nor there.

[TheJudge]

Einstein's relativity for dummies.


You know, I've actually understood that since I was ten, but then I was reading Asimov and others at that age...

[Clark Kent]

About the black hole- i think i know the answer, but ask anyways- whos time reference would make things near the event horizon appear to move iin extra slow motion?  In the time reference of those being sucked in, how long would it take?
ANother question: gravity causes things to fall exponentially (disregarding drag), but in cases of severe differences between frames of reference, would a falling object appear to stop, only to very slowly speed up as it fell firther, or would it's closer proximity to the relatively intense gravity make it appear to slow even more?
In the space ships: what happens when they move in opposite directions at the same speed?
Sorry, I've never had an opportunity to learn relativity.

[Capt. Mike]

Have a read...I have the book..doesn't necessarily explain everything, but it's a start  http://www.racai.ro/~dragam/2KAFNADO.HTM

Mike

[Capt. Mike]

And to quote Ford Prefect  "Time is an illusion, lunchtime doubly so"   

[Firehawk]

In the time frame of an outside observer(outside the gravity of the blackhole) someone falling in to the blackhole would appear to slow down the closer he got to the event horizon.  The outside observer would never actually see the person cross the event horizon, he would appear to freeze in time.  In the time frame of the person falling into the blackhole time would appear to be moving normally for you but looking back at the outside universe time would appear to be speeding up and it is theorized that at the instant you cross the event horizon time in the outside universe would appear to be moving infinetily fast and you could see albiet in extremely compressed time the end of the outside universe.

[Clark Kent]

So does nothing actually ever enter the black hole then?
At what point do the tidal forces become so powerful that they rip you apart?  How long would it take in any perspective?

[Capt. Mike]

Yes, matter does enter the black hole..the event horizon is the point/plane/vector where the gravatic pull exceeds the energy needed for a photon to escape..i.e. light will not get out, so observation can only be done through it's effects

Mike

[Firehawk]

You really want a question that will blow your mind?  Here is a question that was posed by a former professor at Cambridge University

"As one approaches the event horizon of a black hole, time dilation
relative to a distant observer increases without limit.  At the event
horizon itself, the time dilation effect is infinite (i.e. an observer
sufficiently close to the event horizon could watch the universe grow old
and die). Conversely, according to a distant observer, no time passes at
the event horizon of a black hole.  Therefore, how can the black hole
actually finish forming, from the point of view of a distant observer?  As
it collapses, and time dilation increases without limit, the black hole
formation process will also be affected by the time dilation.  At the
moment the event horizon is created, the time dilation will be infinite,
so time will cease on the event horizon. My question is: will the
increasing time dilation cause the black hole's event horizon never
actually to form, because the process slows down without limit? If so, can
it really be said that black holes exist, if none of them have ever
finished forming?"

[Clark Kent]

Excellent question, that would take some thought.
What about this: if time slows exponentially as you approach the event horizon, what happens to time after you pass the event horizon?  Does it continue to slow?  Does it reach zero at the event horizon and then reverse?

[Firehawk]

Well here is tha answer that was given in response to the question

"From the point of view of a hypothetical observer situated near the core of the collapsing star, the black hole certainly does form. He would fall into the black hole as it collapsed and experience the (presumably) horrible consequences of being trapped inside the event horizon.

On the other hand, another observer out in the distant universe, watching the collapse, would see our hypothetical observer take an apparently infinite time to fall into the black hole. This doesn't mean that this is actually happening, only that this is what appears to happen. At the same time, as our hypothetical, and doomed, victim falls into the black hole, they dim and become invisible. We don't see them become "frozen" at the event horizon. That's because we can only see photons that they emitted before they crossed the event horizon. Once they fall into the hole, none of the light they emit can reach us, so at some point they have to disappear from our sight. "


As far as what happens to time once you cross the event horizon and enter the sigularity, well that is a whole other area of physics and they are still working on that.

[Capt. Mike]

Does it grow exponentially (logarithmically) or linearily..makes a big difference in the equations...ahhh, but who's gonna do the actual physical experiment...most of that is left to the meta-physical philosophers and the sci-fi writers..

Mike

[TheJudge]

Wait a minute here...I just remembered Stephen Hawking just published a new essay on Black Holes that was supposed to totally revolutionize our thinking on them...need to find the thing...

[TheJudge]

Here it is:

Stephen Hawking revamps black hole theory



DUBLIN, Ireland (AP) -- Famed astrophysicist Stephen Hawking says black holes, the mysterious massive vortexes formed from collapsed stars, do not destroy everything they consume but instead eventually fire out matter and energy "in a mangled form."

Hawking's radical new thinking was presented in a paper to the 17th International Conference on General Relativity and Gravitation in Dublin.

It capped his three-decade struggle to explain an elemental paradox in scientific thinking: How can black holes destroy all traces of consumed matter and energy, as Hawking long believed, when subatomic theory says such elements must survive in some form?

Hawking's answer is that the black holes hold their contents for eons but themselves eventually deteriorate and die. As the black hole disintegrates, they send their transformed contents back out into the infinite universal horizons from whence they came.

Previously, Hawking, 62, had held out the possibility that disappearing matter travels through the black hole to a new parallel universe -- the very stuff of most visionary science fiction.

"There is no baby universe branching off, as I once thought. The information remains firmly in our universe," Hawking said in a speech to the conference.

"I'm sorry to disappoint science fiction fans, but if information is preserved, there is no possibility of using black holes to travel to other universes," he said.

"If you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form, which contains the information about what you were like, but in an unrecognizable state."

At that point, the audience of about 800 people, including many of his peers, laughed.

He added, "It is great to solve a problem that has been troubling me for nearly 30 years, even though the answer is less exciting than the alternative I suggested."

In a humorous aside, Hawking settled a 29-year-old bet made with Caltech astrophysicist John Preskill, who insisted in 1975 that matter consumed by black holes couldn't be destroyed.

He presented Preskill a favored reference work "Total Baseball, The Ultimate Baseball Encyclopedia" after having it specially flown over from the United States.

"I had great difficulty in finding one over here, so I offered him an encyclopedia of cricket as an alternative," Hawking said, "but John wouldn't be persuaded of the superiority of cricket."

Later, Preskill said he was very pleased to have won the bet, but added: "I'll be honest, I didn't understand the talk."

Like other scientists there, he said he looked forward to reading the detailed paper that Hawking is expected to publish next month.

Hawking pioneered the understanding of black holes -- the matter-consuming vortexes created when stars collapse -- in the mid-1970s.

He has previously insisted that the holes emit radiation but never cough up any trace of matter consumed, a view that conflicts with subatomic theory and its view that matter can never be completely destroyed.

Hawking, a mathematics professor at Cambridge University, shot to international fame with his best-selling book "A Brief History of Time," which sought to explain to a general audience the most complex aspects of how the universe works.

Despite being virtually paralyzed and wheelchair-bound with amyotrophic lateral sclerosis since his mid-20s, Hawking travels the world on speaking engagements.

He communicates by using a hand-held device to select words on his wheelchair's computer screen, then sending them to a speech synthesizer.

http://www.cnn.com/2004/TECH/space/07/21/hawking.blackholes.ap/


Now name the ST:TNG episode in which Hawking appeared.

[Firehawk]

Yes I remember reading that article, it is quite interesting. And I recall seeing a program about this also.  Blackholes slowly evaporating by releasing a few molecules/atoms at a time until nothing is left of it.

Rats I can't remember the name of that episode but it is the one where data is playing poker with holographich reprsentations of Hawking, Newton and Einstien.


**EDIT** Descent was the name of the episode.

[Just plain old Punisher]

Funny, I thought Time was a magazine.

Keeping in mind Time is a concept, and it depends completly upon your realitive point of view. We have only viewed "Black Holes" indirectly by the affects they have on their local enviornment (IE pulling in ionized gas/nebula material, or the bending of light as it passes near the black hole) We really don't know exactly what happens to the trapped material. Who knows, it could go to that same place my socks go when I wash them.

[Clark Kent]

I'm betting it's where they're hiding all those hot Asian women I've been scouring the country side for.