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| Thread: Physics/Philisophical Question to ponder |  This thread is pages long: 1 2 · NEXT» |
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friendofgunnar
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posted June 23, 2012 09:31 AM |
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Physics/Philisophical Question to ponder
This clip referring to the upcoming Martian probe landing was in a newspaper article.
Quote:
Surveying the landing process from a control station on Earth, NASA’s crew won’t know what’s happening with the rover due to a delayed signal. It takes 14 minutes for the rover’s signal to reach from Mars to Earth, meaning NASA will be observing the process on a delayed timeline.
“When we first get word that we’ve touched the top of the atmosphere, the vehicle has been alive or dead on the surface for at least seven minutes,” said engineer Adam Stelzner in a NASA video.
Here's the video clip that it came from.
Is that right? If you get a signal from Mars did that signal really happen 14 minutes ago? If it's true that absolutely nothing can move faster than light then for any and all intents and purposes isn't it happening right now?
Both philisophically and also from the standpoint of physics there's absolutely nothing you can do to affect what's happening on Mars in that 14 minutes so why wouldn't you say that it's happening in the present? Can anybody persuade me logically otherwise?
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Tsar-Ivor
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posted June 23, 2012 12:16 PM |
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True, nothing really exists 'till it has an effect on YOU, so yes you are correct, though the events are occurring 14 minutes in the past, it means ****-all if nobody ever sees them in the present.
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Lord_Woock
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posted June 23, 2012 01:40 PM |
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The trick with relativity is that you indeed can't treat time as an absolute. A pair of events may happen simultaneously from one perspective and also be separated by a significant delay from another.
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JollyJoker
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posted June 23, 2012 03:27 PM |
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Well, no.
We are talking about two different things here.
1) Event/occuring
2) Observer/observing
You could test the effect with relaying a sonic signal electronically:
If you speak with someone who's a couple of kilometers away via a cell phone you may hear something loud - an explosion, very loud thunder - over the phone with too short a delay to register it. You will hear the same sound then a couple of seconds later "for real".
So while an event happens NOW, it takes a certain time for the signals of the event to travel through space. It's not immediately obvious since it's counter-intuitive for the environment in which we live in.
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Corribus
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posted June 23, 2012 04:36 PM |
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Quote:
If you get a signal from Mars did that signal really happen 14 minutes ago?
Yes, and you don't even need relativity to understand this.
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I'm sick of following my dreams. I'm just going to ask them where they're goin', and hook up with them later. -Mitch Hedberg
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friendofgunnar
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posted June 24, 2012 08:01 AM |
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@JJ
When you bring up a sonic test I think you're taking my philisophical/physics question to an extreme. I would never claim that when I hear thunder I'm hearing the thunderbolt as it happens. However if I see a lightning bolt that would be a different story. At this point I may want to dither about the speed of light through air being 99.97% of the speed of light through a vacuum. Neutrinos would move through air at a speed that hasn't yet been distinguished from the speed of light through a vacuum so I would say this "wave of causality" carried by the neutrinos would qualify as the "now" and the lightning bolt I saw would qualify as the "just a moment ago".
@ Corribus
I see that I framed the question wrong. It would be more accurate to say "Did the reality that the signal is describing happen 14 minutes ago or is it happening now?"
If you say it happened 14 minutes ago your asserting that there's some type of universal clock with a stopwatch feature. The stopwatch starts when the signal is sent and the stopwatch stops when the signal is received. I admit that this a convenient way to think of things and I also admit that it's very common thing for people to do when describing astronomical events but it goes against the grain of Einstein's relativity.
The fundamental premise of Einstein's relativity is that there's no objective reality beyond what you can observe (the "wave of causality" that moves at the speed of light in a vacuum). So if you buy into Einstein's theory it means there's no universal clock, which means it's improper to assert that the reality that's being described by the signal happened 14 minutes ago. That reality is happening when the wave of causality reaches you.
You could flip the observational point by saying it this way "The Martian probe sent it's signal and 14 minutes later it will reach the observers on earth." In this case you are using an imaginary perspective that logically accords with relativity.
heheh, I just saw this joke
Quote:
Bartender says: "Sorry, we don't serve faster-than-light neutrinos here."
So you have these two faster-than-light neutrinos walking into a bar...
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JollyJoker
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posted June 24, 2012 08:41 AM |
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What Einstein meant was something else entirely, though - that you cannot COMPARE independent reference systems. The twin paradoxon is an example for this.
There is no universal stopwatch because every reference system has their own stopwatch that may tick in a different way.
However, at this point there is only one: ours. WE live NOW, and when we look at the night sky and see Sirius that light has travelled 8.6 light years and is therefore just as old FOR US and OUR reference system. It's like a video redording of a picture that is sent to us.
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alcibiades
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posted June 24, 2012 09:05 AM |
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Quote:
If you get a signal from Mars did that signal really happen 14 minutes ago?
Yes, it did, because consider this incident:
a) You get the signal from Mars that the Rover is on direction towards a deep hole. It will take the Rover 15 minutes to reach the edge of the hole.
b) You send the signal to the Rover to turn around to avoid falling into the hole.
Now the outcome may be one of two:
1) If the event that you receive from the signal IS really simultaneous with you receiving it, you would be able to save the Rover.
2) If the event that you receive from the signal is ACTUALLY 14 minutes ago, you will not be able to save the Rover, because the Rover will actually only be 1 minute from the hole, thus making it having been 13 minutes IN the hole by the time that your signal to change direction reaches it.
Thus, the two set-ups have vastly different outcome, which could easily be tested. There is no reason to believe that the second case should not be true, and thus it does make sense to say that the event that we receive was actually 14 minutes ago, even from a philosophical point of view.
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What will happen now?
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Ghost
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posted June 24, 2012 10:41 AM |
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I do not know much. But if the Sun goes out, we see only 8 minutes away. Since solar radiation is on its way to Earth eight minutes. That is why we see the Sun still shines.
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Miru
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posted June 24, 2012 02:11 PM |
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Phenomenology
yay wastes of time
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Corribus
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posted June 24, 2012 04:32 PM |
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@Miru
Stop being a troll. If you've nothing to add, keep out of it.
@FoG
Quote:
The fundamental premise of Einstein's relativity is that there's no objective reality beyond what you can observe
That's not really the premise of relativity. The chief premise is that there's no objective frame of reference.
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Zenofex
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posted June 24, 2012 08:52 PM |
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Edited by Zenofex at 20:53, 24 Jun 2012.
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Quote:
Is that right? If you get a signal from Mars did that signal really happen 14 minutes ago? If it's true that absolutely nothing can move faster than light then for any and all intents and purposes isn't it happening right now?
There is no known medium which allows an information of any kind to travel from point A to point B (through that medium) immediately, i.e. with zero delay. You can easily observe this on our own planet, even at your own home (granted, you'll have difficulties making the test in vacuum but that's not really important as the base is the same) so I don't know why you need Mars to put the concept to test. If someone invents a technology that can transfer the information from any place to any place without any delay, then you could say that everything is "right here, right now" at least as far as the informational availability is concerned. Until then assuming that something exists only when your senses can interpret it directly and immediately is pretty much the same as assuming that you are the only perceiving creature in the world and that the world itself is nothing but illusion as long as you can't perceive it yourself. Which among other things makes posting topics on Internet forums a nonsense. 
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friendofgunnar
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posted June 25, 2012 07:33 AM |
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@JJ
Quote:
It's like a video redording of a picture that is sent to us.
It's true that the light arriving is a type of video recording, but the gist of what I'm getting at is that the arriving light coincides with a causative wave that not only represents reality but is reality itself.
I just realized that my own quote makes use of a universal clock.
Quote:
"The Martian probe sent it's signal and 14 minutes later it will reach the observers on earth."
The english language really isn't set up for relativity
@Alci
I'm perfectly willing to recognize that there's a 14 minute time lapse between the time earth takes action and the time the probe responds. It's as simple as noting the 28 minute round trip and dividing by 2.
@Corribus
Can you really separate these two?
1.The fundamental premise of Einstein's relativity is that there's no objective reality beyond what you can observe
2. The chief premise is that there's no objective frame of reference.
BTW the chief purpose of this thread was to get people thinking about how they view the universe. To be completely honest the idea of a universal clock is so compelling that even I have not been able to let it go completely. There's an alternate relativity theory known as Lorentzian relativity that allows for the existance of a universal clock and picks the reference frame as the local gravitational field. The theory is a descendant of a pre-einsteinian relativity theory known as Lorentzian Ether Theory. Both Einsteinian theory and Neo-LET are based on the Lorentz transformation which is why...here, I'll just link you to wiki article because it's getting difficult to summarize. There's another interesting paper that does a fairly good job of explaining it but I've lost track of it. If there's anybody interested enough I'll try to track it down.
There's also some aspects of quantum theory that seem to intuitively speak to Lorentzian relativity. For example you can excite an atom such that it will emit two identical particles. When you measure one of the particles you will collapse the wave functions of both, no matter how far apart both of the particles have gotten. There seems to be some type of instantaneous 'communication' between the two particles whereby their quantum functions both collapse at the same time. This seems to speak to the idea of a universal clock. You can't send any information this way however so it doesn't break the causation rule. Relativity remains intact, even if it looks intuitively like it's been broken somehow.
@Ghost
Yes, Star Trek Generations was bollocks
I lol'ed at Miru's post btw.
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JollyJoker
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posted June 25, 2012 08:10 AM |
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Quote:
@JJ
Quote:
It's like a video redording of a picture that is sent to us.
It's true that the light arriving is a type of video recording, but the gist of what I'm getting at is that the arriving light coincides with a causative wave that not only represents reality but is reality itself.
The electromagnetic waves that we can perceive are just information. Mass has its own gravitational reality that is NOT transferred. Show can the wave BE realty?
Also, you are mistaking the universal clock - which would be able to link and sort all existing reference frames everywehere and and everytime - with the subjective, singular reerence frame of us, the people living on planet terra and their instruments. We are not using a universal clock by sorting the information we receive into OUR reference frame and forming a picture.
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friendofgunnar
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posted August 06, 2012 07:19 AM |
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I'm watching the mars landing/possible obliteration live
http://www.ustream.tv/NASAJPL
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friendofgunnar
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posted August 06, 2012 07:21 AM |
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10 minutes to go...
tense!
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friendofgunnar
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posted August 06, 2012 07:25 AM |
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Atmo!
or has it already landed?
(no)
edit 4 minutes later:
Parachute Deploy!
edit 2 minutes later:
Sky Crane has started!
Touchdown confirmed Safe on Mars!!!!!!!!WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
Wheels down on Mars:
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Salamandre
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posted August 06, 2012 07:59 AM |
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14 minutes after US the image came in France too
But in better shape, in background is the sun, as seen from Mars.
Congrats
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Ghost
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posted August 06, 2012 08:04 AM |
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friendofgunnar
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posted August 06, 2012 08:08 AM |
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I can't wait for the high res stuff.
hmmm
actually I can, I already know what the surface of Mars looks like
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