Did you know that no known law of physics, not a one, has a preference for going "forward" in time versus backwards? That means that the laws of the universe we are able to objectively define have no preference for either direction, backward or forward in time. But yet we remember the past and not the future.

I created this thread so people could argue as to why that is, and so I could tell them why they're wrong.

It's time we get some real philosophy on this site!

6/30/2011 7:33:34 PM

afaik, there are no hardcore physicists/philosophers on this site with loads of experience/research under their belts.

6/30/2011 7:40:02 PM

i thought if you traveled close to or at the speed of light special relativity says time passes slower for you?

so if you were flying in your spaceship and someone with a telescope looking in the window you would be moving in slow motion or not at all?

if you returned to earth after traveling at this speed for so long not much time would have passed for you but hundreds of years could have passed on earth.

isnt this time travel into the future? or does it simply mean time went faster for everyone else?

seems like i read this in a "science of star wars explained" book, so im by no means right or an expert.

[Edited on June 30, 2011 at 7:49 PM. Reason : "]

6/30/2011 7:45:28 PM

^pretty sure that was the premise for the movie, "Contact"

6/30/2011 7:50:10 PM

OH YEAH.

but that was written by carl sagan right and he generally knew his stuff amirite?

time dilation is cool too.

from wikipedia:

"It has been calculated that, under general relativity, a person could travel forward in time at a rate four times that of distant observers by residing inside a spherical shell with a diameter of 5 meters and the mass of Jupiter.[22] For such a person, every one second of their "personal" time would correspond to four seconds for distant observers. Of course, squeezing the mass of a large planet into such a structure is not expected to be within our technological capabilities in the near future."

i read something along these lines one time that said if you had a cylinder of infinite length weighing about as much as the universe and spun it at a few billion rpm, you could fly around it in a corkscrew fashion and go backwards/forwards in time.

it said it didnt have to be of infinite length to work, but was advisable since really weird things would happen to you if you flew near either end? whatever. shit blows my mind.

every movie ever with time travel confused me.

6/30/2011 7:55:12 PM

^^^ So, time travel into the future is easy. Case in point

http://www.futureme.org/

Einstein just made it easier.

Time travel to the past is really super-duper difficult.



[Edited on June 30, 2011 at 7:58 PM. Reason : ]

6/30/2011 7:58:41 PM

< -- stupid

[Edited on June 30, 2011 at 7:59 PM. Reason : ]

6/30/2011 7:59:07 PM

mrfrog i dont think that really changes how we perceive time.

my example did. my example causes something AMAZING to happen for both parties involved.

people on earth see you not moving or barelyy moving for hundreds of years, not aging.

you come back to a bunch of weird future shit.

i guess if we could travel at or near the speed of light all kinds of cool things would happen?

<-----stupid also

6/30/2011 8:13:28 PM

Time dilation is a proven fact, by the way. GPS satellites have to be adjusted to compensate for it. I saw the calculations recently suggesting that while time moves slower from the perspective of GPS satellites due to their speed, their distance from the earth's gravity negates this effect and time actually moves faster from the satellite's perspective overall.

The opposite is true for astronauts since they are in low earth orbit and speed is the dominating factor on time. From the astronauts perspective time moves slower than on earth...ie astronauts age slightly slower.

Quote :

"The gravitational and kinematic time dilation effects are of comparable orders of magnitude for satellites in earth orbit. For satellites in low earth orbit (which includes almost all crewed activity), the kinematic effect dominates. But for satellites in higher orbits (e.g., GPS and geosynchronous satellites), the gravitational effect dominates. "

[Edited on June 30, 2011 at 8:36 PM. Reason : .]

6/30/2011 8:28:17 PM

Quote :

"i guess if we could travel at or near the speed of light all kinds of cool things would happen?"

It is totally awesome, and yes, the "time dilation" of any intrepid space traveler can be as low as 1 and as large as infinity.

As mullet-worthy as this is, there are many places in the universe that give you a 1-way ticket to really far in the future or possibly even the end of the universe. A well planned visit near the surface of a black hole could put you 1000s of years or billions of years in the future when you get back. Technically, you can fly straight into it and survive passing the event horizon, at which point you've time warped to the end of the universe, although that's subjective. It would only be correct to say that you are "dead to the rest of us".

But what happens when you time dilate yourself to the end of the universe? I picture two astronauts in a space station next to a black hole, then one of them finally gives up and say "God dammit Jim, I just can't take it anymore, I have to know what's on the other side!" What happens when he makes the jump? Jim will never know.

[Edited on June 30, 2011 at 8:32 PM. Reason : ]

6/30/2011 8:32:14 PM

Plenty of neat arguments in the philosophy of time, but it's certainly not something I'm acquainted with in anything other than a superficial way.

I tend to think of time in a Kantian way; it's a precondition for experience/comprehension/cognition. This plugs the question ... clearly you could dig further. This is one of those cases where I'm not willing to go down the rabbit hole, though.

6/30/2011 8:33:06 PM

^^yeah if you jump into a black hole time would slow down so much for you approaching the event horizon no external observer would ever actually see you cross into it.

6/30/2011 8:34:48 PM

Quote :

"I tend to think of time in a Kantian way; it's a precondition for experience/comprehension/cognition"

Oh it absolutely is. But to make this more bizarre - physics equations do show the existence of time. The only thing it doesn't do is demonstrate that it has a direction. The equation shows that time is a number line, meaning it has 2 directions. Why one direction as opposed to the other? That's the funky stuff.

Quote :

"ie astronauts age slightly faster."

I think it's slower. Yeah... I had to Google that.

6/30/2011 8:37:59 PM

Yes, I had it backwards. It is corrected in my post above. It is GPS satellites and other high orbit objects that don't behave as special relativity alone would predict.

6/30/2011 8:41:22 PM

Quote :

"Time dilation is a proven fact, by the way."

well, yes and no. There is certainly knowledge that something affects the clocks of GPS satellites, but what, exactly, that is, has yet to be completely pinpointed. IIRC, experiments were done putting clocks into airplanes and flying them around the earth (the plane took off), and the clocks speed up only when the planes flew in one direction as opposed to the other. There are theories as to why this is the case, but it is dubious at first glance.

6/30/2011 8:47:20 PM

^flat earth society study?



I thought time was a consequence of the laws of thermodynamics?

6/30/2011 8:54:42 PM

Quote :

"Why one direction as opposed to the other? That's the funky stuff."

I read some Hawking once and he tried to answer the question by saying subjective time flows in the direction of entropy, since formation of memories (or any cognitive event, really) requires energy to be expended.

6/30/2011 8:58:02 PM

Quote :

" There is certainly knowledge that something affects the clocks of GPS satellites, but what, exactly, that is, has yet to be completely pinpointed. "

*BUZZER SOUND*

try again

http://en.wikipedia.org/wiki/Gravitational_time_dilation

Quote :

"Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential, the more slowly time passes. Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity."

6/30/2011 9:01:00 PM

^^^
^^

So these are both pretty much "the answer". Time flows in the direction of increasing entropy.

But good subsequent questions remain. Why does entropy increase in the first place... why doesn't it stay the same? Once I start realizing that trivial-seeming things about the world around me comes from statistical emergent phenomena, then I really start to get tripped out.

6/30/2011 9:12:20 PM

Quote :

"Once I start realizing that trivial-seeming things about the world around me comes from statistical emergent phenomena, then I really start to get tripped out."

It's only trippy if you think the probabilistic shit is inherent in the world. If you're a subjectivist about probability, then the "emergent" nature you're talking about has to do with the limits of observation, knowledge, and human theory.

6/30/2011 9:13:36 PM

wrong thread!

[Edited on June 30, 2011 at 9:47 PM. Reason : ]

6/30/2011 9:45:44 PM

Why would anyone be subjectivist about probability? It’s a fact of the universe, quantum mechanics demonstrates this.

6/30/2011 11:03:55 PM

Correct, QM more-or-less establishes that such a thing as "truly random" exists.

But most things we consider random are not random. If I make a random number generator it's most likely not random, same with a coin flip. But.... quantum randomness does effect the progression of real events. Where is the borderline? Who knows. But I can build a random # generator using nuclear decay and it will be 100% quantum randomness.

Kind of amazing actually. The universe allows both total determinism and total randomness at the same time.

Thermo 2nd law, however, depends only on statistics (which has an emergent concept of pseudo randomness, or chaos). Not quantum randomness.

6/30/2011 11:30:45 PM

how much weed could a pothead smoke if a pothead could smoke weed?

6/30/2011 11:41:22 PM

Quote :

"*BUZZER SOUND* try again "

how do you figure? did you even READ what the fuck I posted? obviously not

7/1/2011 12:38:36 AM

Walter, don't mind aaronburro. He doesn't think like rational people. If it's not his claim, you must have a level of certainty about your claim that is impossible. He thinks that science needs to explain phenomena to every microsecond and sub-atomic particle for the entirety of phenomena to be able to claim knowledge of the phenomenon. I'm not convinced he actually thinks this way, but it's a silly game that he thinks he can use to dismantle scientific conclusions.

[Edited on July 1, 2011 at 12:55 AM. Reason : .]

7/1/2011 12:55:01 AM

so, you deny the well-established results of the Hafele Keating experiment? I'm just curious, since you are accusing me of not knowing a thing about science

Quote :

"He thinks that science needs to explain phenomena to every microsecond and sub-atomic particle for the entirety of phenomena to be able to claim knowledge of the phenomenon."

oh look, strawman. good work!

[Edited on July 1, 2011 at 12:57 AM. Reason : ]

7/1/2011 12:56:40 AM

Quote :

"There is certainly knowledge that something affects the clocks of GPS satellites, but what, exactly, that is, has yet to be completely pinpointed."

Philosophically, you're in the green.

Factually, well.. factually is difficult because we all read different evidence. I have not read about the same experiments that you have. More than likely, somebody at some point wrote something that conveyed to you the discrepancy in the data from some experiments. I know of no such discrepancies.

Here is what I do know:
The evidence for special relativity was present in the 1800s, and it continued to pile up from there. General relativity has had plenty of diverse confirmations of it, which include notably astronomy as well as direct time dilation comparisons.

The most convincing I have seen is this:
http://www.sciencemag.org/content/329/5999/1630
Imagine 2 shelves. One of them is about a foot higher than the other. These people basically put clocks on a shelves 1 F-ing foot apart vertically and correctly detected the expected time dilation due to the difference. I mean, I want to shake these physicists and scream in their face WHY?? You need to understand, the different is like 10^-16 or something, and this absolutely pushed the very bleeding edge of precision measurement technology. But now you can grab 2 clocks and put one above the other and know that the time rate difference has been experimentally confirmed. Your feet are aging slower than your head to an extent that we have been able to literally measure.

It makes me want to stab myself in the eye just thinking about the amount of overkill they put into confirming general relativity. But then again, people still walk around thinking that the experiments are conflicted on the subject.

Here is a 2008 paper about the experiments, in a big picture
http://arxiv.org/abs/0806.1731

Einstein was so right it makes me angry. Couldn't he have been just a little bit wrong? But no. Yes, science is now trying to figure out how gravity works on crazy huge scales and crazy small scales, for which we have good reason to believe it will be different, but we are far from that. That misses the point though. Einstein never said general relativity holds on the plank length scale. It's just valid for some range, and in spite of our best efforts we have not been able to find the limit of that range yet.

[Edited on July 1, 2011 at 1:06 AM. Reason : ]

7/1/2011 1:04:48 AM

Quote :

"so, you deny the well-established results of the Hafele Keating experiment? I'm just curious, since you are accusing me of not knowing a thing about science"

I'm confused why you think that the Hafele Keating experiment somehow disproves Special or General Relativity.

Quote :

" In a frame of reference at rest with respect to the center of the earth, the clock aboard the plane moving eastward, in the direction of the Earth's rotation, has a greater velocity (resulting in a relative time loss) than a clock that remains on the ground, while the clock aboard the plane moving westward, against the Earth's rotation, has a lower velocity than the one on the ground, resulting in a relative time gain."

It makes sense why the clocks behaved the way that they did, and is consistent with the same laws that predict the effects of relativity of GPS satellites.

7/1/2011 1:11:04 AM

Quote :

"These people basically put clocks on a shelves 1 F-ing foot apart vertically and correctly detected the expected time dilation due to the difference."

But this is the problem: what if something else is affecting the clocks in the exact same way that GR predicts, only in another situation it would completely fall apart. I'm not saying that is really how it is, but it is certainly worth pointing it out. I'm not afraid to say that the time dilation effects of GR make me queasy and I have a hard time accepting them at face value. I imagine it's that way for most people when they first hear of it, I've just held on to that absurdity a little longer, enough to devise experiments to challenge it. Of course, I don't have the equipment to run the experiments, so there's that.

^ the problem with that explanation is that it assumes that the clock "on the surface of the earth" is in the same reference as the clock "at the center of the earth". They simply aren't.

[Edited on July 1, 2011 at 1:20 AM. Reason : ]

7/1/2011 1:15:59 AM

Quote :

"what if something else is affecting the clocks in the exact same way that GR predicts, only in another situation it would completely fall apart."

Then we'll come up with a new theory. Provide evidence that there's something else effecting the clocks in exactly the same way that General Relativity predicts. Until that time, I'm going with General Relativity, which is been experimentally verified countless times.

7/1/2011 1:18:52 AM

Quote :

"Why would anyone be subjectivist about probability? It’s a fact of the universe, quantum mechanics demonstrates this."

What? No. That really depends on your interpretation of QM. Some people believe that probability is subjective because frequency-style interpretations are largely absurd when analyzed carefully. If you want a good example of a subjectivist viewpoint, check out Bruno de Finetti. The idea is not that "anything goes" with probability, but that there's an optimal position to stand with respect to a body of data (optimizing your likelihood function given some body of information).

http://en.wikipedia.org/wiki/Bruno_de_Finetti

Frank Ramsey is another subjectivist worth checking out. When you say "quantum mechanics demonstrates probability is a fact of the universe", you mean to say that physicists interpret probability functions as real waves (objects that act formally like waves; I'm no expert in statistical mechanics, but I believe this is due to their interaction patterns). Some physicists physically interpret their probabilistic concepts, but I think that has more to do with wanting to do physics than being philosophically sound in doing so.

[Edited on July 1, 2011 at 6:44 AM. Reason : .]

7/1/2011 6:43:25 AM

Quote :

"But this is the problem: what if something else is affecting the clocks in the exact same way that GR predicts, only in another situation it would completely fall apart."

No, you just don't GET the role of a physics theory. GR does not specify what causes these effects. All it does is to give a set of rules that are born out of the need for consistency given certain observations/assumptions, particularly the equivalence between accelerating bodies and bodies in gravitational fields.

Additionally, GR is wrong. At some level GR is bound to be wrong, and if this wasn't true there wouldn't be jobs for theoretical physicists today. An argument for this is simply that it doesn't tell what the mechanisms that cause the GR laws to arise are. At some point we may be able to stare those mechanisms straight in the face and formulate comprehensive laws for the universe, from which gravity and the other fundamental forces can be derived.

Einstein himself worked furiously on such theories.

Actually, GR has been derived from other, more fundamental laws. A problem however, is that other people don't fully believe it. Some guy took the assumption that entropy is proportional to the surface are of a system and showed that it implied all the laws of GR. So that is a theory, but there could be other consistent explanations.

[Edited on July 1, 2011 at 9:07 AM. Reason : ]

7/1/2011 9:05:18 AM

Quote :

"GR does not specify what causes these effects."

well, again, yes and no. isn't GR saying that it is gravity which is causing these effects, even it doesn't say exactly how? My point is that it may be something else, independent of gravity, which causes these effects, and it just happens to do so in a way the mirrors exactly what we would expect GR to do. I'm not saying that's actually how it is, as I am happy to admit that I know jack shit about GR. But, I do expect, at the point that we actually had the observation necessary to show that GR was suspect, then we would call it as such.

7/1/2011 3:32:20 PM

Quote :

"well, again, yes and no. isn't GR saying that it is gravity which is causing these effects, even it doesn't say exactly how?"

Gravity and spacetime curvature are basically the same value.

Quote :

"My point is that it may be something else, independent of gravity, which causes these effects, and it just happens to do so in a way the mirrors exactly what we would expect GR to do."

As in there could be a common cause for gravity and spacetime curvature, absolutely. Consistency is not broken so sure.

7/1/2011 3:47:39 PM

people in Ecuador age slower than people in Alaska.

7/1/2011 5:13:16 PM

^ about the only things on Earth it matters for are particles in super accelerators. it matters a great deal to those

7/1/2011 5:18:48 PM

I've never been to the sun. How do I know it's not really a bunch of light-bulbs?

7/1/2011 5:43:36 PM

^ well obviously you don't

7/1/2011 6:04:09 PM

Don't get me wrong. I'm sure the scientists are right when they say the sun is a mass of incandescent gas. A gigantic nuclear furnace, if you will. I'm just saying it might be something else like a giant light bulb that looks and behaves like it's building hydrogen into helium at temperatures of millions of degrees.

I don't really know that much about the sun, though.

[Edited on July 1, 2011 at 6:43 PM. Reason : ]

7/1/2011 6:41:48 PM

You haven't heard the update. The sun isn't a mass of incandescent gas. The Sun's a miasma of incandescent plasma.

7/1/2011 7:09:12 PM

Can anyone justify evidence that time is actually a real quantity? I have trouble seeing time as anything more than just man's way of compensating for lack of understanding. We use time to help us organize and plan but is it actually a dimension? Do we have proof?

The whole time slowing down thing is based on clocks or oscillators. I understand that clocks exist but those are part of manmade time to me.

7/1/2011 7:13:22 PM

^ Time dilation affects natural processes as well, not just man-made clocks and such. Notably:

Quote :

"Performed in 1940 at Echo Lake and Denver in Colorado, the Rossi–Hall experiment, named after Bruno Rossi and D. B. Hall, measured the relativistic decay of muons (which they thought were mesons). They only measured muons in the atmosphere traveling at 99,94% of the speed of light. If no time dilation exists, than those muons should decay in the upper regions of the atmosphere, however, as a consequence of time dilation, they are present in considerable amount also at much lower heights. A value for the muon lifetime was given as t = 2.3±0.2 µs, which was later refined in 1943 by Rossi and Nereson to t = 2.15±0.07 µs, which was still in excellent agreement with special relativity and even modern measurements (2.197034(21) µs). A more precise repetition of the experiment was made by Frisch & Smith (1963)."

http://en.wikipedia.org/wiki/Time_dilation_of_moving_particles

7/1/2011 8:02:35 PM

^ I think you're misinterpreting his point. It's not that humans made clocks when there were no natural clocks before (untrue in so many ways), but I've known many people to attack the inherency of the thought, the concept, of time itself.

Are we really experiencing time, or are we just trapped in a single moment and can't tell? Are the things you are experiencing right now really progressing through time or is it just an illusion? What does memory really mean and tell us? And who are "we"?

People made the point about Star Trek that the thing the beams people up could actually be removing "you" from the universe and creating a new you. But the same arguments can apply for any moment in time. Continuity is perceived in our minds, but we don't basis to understand what the truly means.

7/1/2011 10:06:42 PM

Quote :

"Are we really experiencing time, or are we just trapped in a single moment and can't tell? Are the things you are experiencing right now really progressing through time or is it just an illusion?"

Can't remember where I've seen this argument before, but I'll try and paraphrase it. If time's an illusion, couldn't you "snap out" of the illusion? So far as I can tell, we're always "trapped" in time. The "illusion" is never broken; it appears as if it can't be broken. What sort of "illusion" can't be broken or lifted?

7/2/2011 1:37:00 AM

^^ 'Manmade time' implied to me that The E Man questioned whether or not 'real time' is actually affected.

In the end, I'm going to follow McDanger and the Kantian way. Time doesn't really exist outside of its use as a mental construct.

7/2/2011 8:04:12 AM

Time is a human construct like numbers are a human construct. Which is to say it isn't. It's a human abstraction of part of the nature of our Universe. Even if humans didn't exist, a square would still have 4 sides. 4 asteroids would still be 4 asteroids and if they existed for a whatever period of time they would have existed for that period of time. Independent of human thought.

7/2/2011 8:52:01 AM

I disagree. Time is not tangible in the same sense that physical quantities are.

Sequences of events may occur without the presence of humans (at least to the extent we don't participate in those events). Interpretation of those sequences as the passage of time is not independent of thought.

7/2/2011 9:23:20 AM

How is the interpretation of anything independent of thought?

7/2/2011 3:00:44 PM

without even reading the thread I can promise you that

there is a lot of nothing going on here


...

btw, if you want to understand the nature of time

GO BUY A FUCKING STOPWATCH

(btw, not bashing the general relativity stuff... that's, of course, awesome) I just know there a bunch of philosophical nonsense in this thread)

[Edited on July 2, 2011 at 4:58 PM. Reason : .]

7/2/2011 4:54:50 PM