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 Jwlst
Stranger
Registered: 02/24/05
Posts: 1,338
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 Re: Grandfather paradox  [Re: Brainstem]
#15372200 - 11/14/11 11:32 PM (11 years, 4 months ago) |
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It seems simple enough to me, I never know why so many people struggle with this paradox but maybe I just simplify it.
I think you would be able to kill your grandpa.
If you travelled back to your present time however, no one would know who you were and there would be no record of you ever existing.
However I personally believe you would still physically exist even after killing your grandpa.
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 OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
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Re: Grandfather paradox [Re: Jwlst]
#15372239 - 11/14/11 11:40 PM (11 years, 4 months ago) |
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Well that explains my lack of birth certificate and SSN.
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Diploid
Cuban
Registered: 01/09/03
Posts: 19,274
Loc: Rabbit Hole
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 Re: Grandfather paradox [Re: Diploid] 2
#15373749 - 11/15/11 10:45 AM (11 years, 4 months ago) |
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Actually, here's the thing. Warning: if you have ADD, this is going to be a long post. But it's interesting and weird so give it a shot.
There are two parts to the question of time travel, into the past and into the future. I'll cover the simpler one first, to the future.
Time travel to the future is possible, but there's a catch (see below). Believe it or not, EVERY time you move with respect to something else, you travel into the future with respect to the not-moving object. This is a consequence of the theory of Special Relativity.
The time predictions of the theory have long ago been confirmed experimentally and are actually used in practical applications like GPS where very accurate timing is important. If the very slight time travel of the GPS satellites were not corrected for in the equations that characterize the system, GPS would not work. I mean this literally. GPS satellites time travel into the future. Really!
In fact, everything that moves with respect to something else time travels. When you fly somewhere in an airliner, you time travel. The only reason you don't notice it is because at ordinary day-to-day human speeds, the effect is very tiny so your wrist watch can't detect it. But this has been confirmed using very accurate atomic clocks. Two atomic clocks are exactly synchronized, then one is left on the ground while the other flies in an airplane. When the plane lands, the two clocks are compared and the result is that the flying clock's time is a few nanoseconds ahead of the one that remained on the ground. This effect is called Time Dilation and it's a central theme in relativity theory. The faster the moving object goes, the more time dilation occurs.
Weird, eh? Well, it gets weirder.
Light (or radio waves which are just light at a frequency our eyes can't detect) takes about 10 minutes to get from here to Mars. If we sent an astronaut to Mars, we couldn't have an ordinary radio conversation with him. We'd have to say something into the microphone, then wait 10 minutes for him to get the message. When he replies, we'd have to wait another 10 minutes to hear the reply.
Now imagine you hop on a rocket that travels very close to c (physicists use the lower-case letter "c" to represent the speed of light). Understand that when I say "very close" I mean REALLY very close. Even though there's a tiny numerical difference between 99.999% c and 99.999999999999999999999999% c, there's a very big difference in the resulting time dilation. It's what math geeks call asymptotic. So I'm talking 99.(a million more nines)% c here. Extremely close to c but just a hair less. So imagine you hop on a rocket that travels that fast and head out to Mars. When you get there, it will have seemed (to you) like only one second passed. Your heart beat once and you're there. Your watch second hand ticked just once and you're there. But time will seem normal to you. You wouldn't notice anything different at all, just the passing of one second of time.
But back on Earth, everyone watching your trip saw it take a whole 10 minutes. Their heart beat many times and the minute hand on their watch ticked off 10 minutes.
If you had a telescope looking at people on earth, in the one second that passed for you during the trip, you saw people on Earth zipping around very quickly. If you pointed your telescope at Big Ben, the clock tower in London, you would have seen the minute hand zip across 10 minutes during your one heartbeat that it took to get to Mars.
Meanwhile, if someone back on Earth pointed a telescope at you in the rocket, he would have seen you nearly frozen still for the whole trip. He would have seen the second hand on your watch tick off one second during the 10 minutes your trip took from his point of view.
So you see that if you get to Mars and immediately turn around and return to Earth, when you got back, you would have experienced two heartbeats and your watch's second hand would have ticked twice. But if you compare with every else's watch, you would notice that your watch would be 20 minutes behind everyone else's.
Now weirder still. Imagine that instead of Mars, your trip was WAY out to the Andromeda Galaxy. Here's a pic I made in 1993:
Andromeda is 2.5 million light years away. It takes light (from our point of view) 2.5 million years to cover the distance there. Now imagine hopping on your rocket again and taking off for Andromeda. When you get there, it will seem like to you as if an hour passed. You wouldn't have to wait 2.5 million years because, again, due to your very high speed, time dilation makes your personal time pass differently than it does on Earth. But again, you wouldn't notice anything different. You'd walk around, maybe have some lunch, read a book, then an hour later (to you) you're at Andromeda.
But back on Earth, 2.5 million years passed. If someone on Earth pointed a telescope at you, they would have seen you almost frozen still because you will have done one-hour's worth of activity during 2.5 million years from Earth's point of view. If you pointed a telescope back at Earth, you would have seen a blur of activity. For every second that ticked off on your watch, 40,000 years will have passed back on Earth. Civilizations would have come and gone every time your watch ticked off one second. But other than the strange sight in your telescope, everything else would seem perfectly normal to you. One hour would pass and your trip is over.
Now here's the catch I mentioned. If you get to Andromeda then turn around and head back to Earth, you'd arrive in another hour from your point of view. A two-hour round trip (for you). But Earth will have experienced another 2.5 million years during your return trip. A total of 5 million years will have passed on Earth after your 2-hour round trip. All your friends and family will be long dead and you'd have a huge electric bill from that night-light you forgot to turn off when you left.
So in this sense it IS possible to time travel into the future. In two hours (to you) 5 million years (to Earth) passed and so you time traveled 5 million years into the future. And again, this is not hypothetical. This is a verified effect and so well-understood that it allows us to create the GPS system which wouldn't work without this understanding.
OK, now time travel into the past.
Although there is no known hard limit on time travel into the past, most physicists consider it unlikely to be possible. There are mathematical results that show backward time travel can hapen, but it's believed with high confidence that they're spurious. Here's a simple example of how these results can come about and why they're unlikely to have any physical relevance.
Recall from high school geometry class how to figure the surface area of a square. Say you have a square piece of plywood with a surface area of 9 square centimeters. What is the length of each side?
Well, if the square's surface area is 9 square cm, then each side must be square root of 9 centimeters long. The square root of 9 is 3 because 3 x 3 = 9.
The piece of wood is 3cm x 3cm. That gives you a total of 9 square cm of wood. The problem occurs in that 9 has two square roots, 3 and -3 because 3 * 3 = 9 and also -3 * -3 = 9.
But it is meaningless to say that the square in question has sides of length -3 cm even though the math tells you that such a square with negative length sides would indeed have a surface area of 9 cm. The math is interesting from an academic point of view, but it has no relevance to the physical world because pieces of wood can't have negative lengths.
This theme repeats in the concept of the Tachyon (faster than light particle) which is another mathematical curiosity that has nothing to do with reality. If tachyons existed, they would have a mass of something absurd like square root of -1 grams, which is meaningless (actually, it would be square root of -1 times some coefficient, but that's not important here).
I never say never, but it seems likely that time travel into the past is a similar curiosity but with no physical relevance. I'd love to be proven wrong though.
There's a related question that hasn't been settled regarding the quantization (granularity) of time. Is there a minimum interval of time that has physical meaning? There are some good theoretical reason that this might be true and some experimental evidence that suggests it.
This might be a little too technical for this thread, but the geeks in the audience will get it so I'll throw it out. Consider the energy of a photon. It is the product of a physical constant (Planck's constant) times the frequency of the light the photon represents. Because E = hc / lamda and c = lamda * v, therefore E = hv. But frequency (v) is the reciprocal of time, so they're in lock-step. Each frequency represents exactly one period (one time interval).
It is known that only discrete frequencies are possible for a photon. No in-between frequencies are allowed by the quantization of quantum mechanics. So if there is a one-to-one mapping from frequency to period (time interval), and only certain frequencies are possible, then only certain time intervals are possible. No in-between time intervals can occur in the wavelength of light. At least with respect to photon energy.
That's not anywhere near proof that time is quantized, but it one point of evidence (and there are others) that has some potentially deep implication. The time it takes for a photon to experience one wavelength is discontinuous. It can take a certain amount of time or a certain longer amount of time, but it can never take an in-between amount of time. Again, not proof, but food for thought.
I'll shut up now. 
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Republican Values:
1) You can't get married to your spouse who is the same sex as you.
2) You can't have an abortion no matter how much you don't want a child.
3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer.
4) We need a smaller, less-intrusive government.
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OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
Loc: Under the C
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Re: Grandfather paradox [Re: Diploid]
#15373758 - 11/15/11 10:47 AM (11 years, 4 months ago) |
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Quote:
We'd have to say something into the microphone, then wait 10 minutes for him to get the message. When he replies, we'd have to wait another 10 minutes to hear the reply.
How is that different than talking to a stoner? 
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Diploid
Cuban
Registered: 01/09/03
Posts: 19,274
Loc: Rabbit Hole
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OMG! You just discovered stoner time travel! You should publish! 
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Republican Values:
1) You can't get married to your spouse who is the same sex as you.
2) You can't have an abortion no matter how much you don't want a child.
3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer.
4) We need a smaller, less-intrusive government.
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Icelander
The Minstrel in the Gallery
Registered: 03/15/05
Posts: 95,368
Loc: underbelly
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Re: Grandfather paradox [Re: Diploid]
#15373764 - 11/15/11 10:49 AM (11 years, 4 months ago) |
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Here's a pic I made in 1993:
Are you the one waving?
That's a fucking awesome pic btw. What size scope and how long was the exposure?
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"Don't believe everything you think". -Anom.
" All that lives was born to die"-Anom.
With much wisdom comes much sorrow,
The more knowledge, the more grief.
Ecclesiastes circa 350 BC
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OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
Loc: Under the C
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Re: Grandfather paradox [Re: Diploid]
#15373767 - 11/15/11 10:50 AM (11 years, 4 months ago) |
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Quote:
Now weirder still. Imagine that instead of Mars, your trip was WAY out to the Andromeda Galaxy. Here's a pic I made in 1993:
Took that out the porthole of your space ship as you passed by? 
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OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
Loc: Under the C
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Re: Grandfather paradox [Re: Icelander]
#15373772 - 11/15/11 10:52 AM (11 years, 4 months ago) |
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Dammit! I hate when you beat me to the punch by mere seconds. 
And scary that we think somewhat alike. 
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OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
Loc: Under the C
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Re: Grandfather paradox [Re: Diploid]
#15373795 - 11/15/11 10:56 AM (11 years, 4 months ago) |
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Quote:
I never say never...
You really think your chance of banging Charlize Theron is > 0?
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DieCommie
Registered: 12/11/03
Posts: 29,258
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Quote:
OrgoneConclusion said:
While philosophical conundrums largely reject the possibility of time travel; physics as it is today, does not. Given sufficient power and technology, what do you surmise would happen if you did go back in time and kill your grandfather?
I dont think anything would happen. Not anything out of the ordinary at least. The particles and proteins that make up your body dont have a memory, they dont 'know' their history. They dont give a crap if your grandpa dies before you are born or not. The paradox is an issue with our memory and the way we want things to be, not the way particles actually behave.
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Icelander
The Minstrel in the Gallery
Registered: 03/15/05
Posts: 95,368
Loc: underbelly
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Quote:
OrgoneConclusion said:
Dammit! I hate when you beat me to the punch by mere seconds.
And scary that we think somewhat alike.
In those two seconds you aged 2.5 million years. You really don't show it that much. 
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"Don't believe everything you think". -Anom.
" All that lives was born to die"-Anom.
With much wisdom comes much sorrow,
The more knowledge, the more grief.
Ecclesiastes circa 350 BC
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Diploid
Cuban
Registered: 01/09/03
Posts: 19,274
Loc: Rabbit Hole
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Re: Grandfather paradox [Re: Icelander]
#15373843 - 11/15/11 11:05 AM (11 years, 4 months ago) |
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That's a fucking awesome pic btw. What size scope and how long was the exposure?
Thanks! That was made with a Takahashi 7" apo refractor on a clock drive. It was hand-guided for 90 minutes. Even though the telescope is mounted on a clock drive, you still have to look in the eyepiece and make minor corrections to the clock speed to keep perfect registration. Otherwise, tiny imperfections in the gears would slightly slow and speed the clock and smear the image.
It was exposed on Fuji 400 color film that was specially hyper-sensitized by exposing the film to pressurized hydrogen for 24 hours before the exposure. I used something called a "cold camera" that uses dry ice to cool the film during the exposure. This reduces fogging from stray light and improves a property of film called reciprocity so the background remains very black and overall contrast improves. That's why the galaxy stands out so well.
I shot it under dark skies at the Southern Cross Astronomical Society's Winter Star Party in the Florida Keys in 1993.
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Republican Values:
1) You can't get married to your spouse who is the same sex as you.
2) You can't have an abortion no matter how much you don't want a child.
3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer.
4) We need a smaller, less-intrusive government.
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OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
Loc: Under the C
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Re: Grandfather paradox [Re: Diploid]
#15373854 - 11/15/11 11:08 AM (11 years, 4 months ago) |
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Icelander
The Minstrel in the Gallery
Registered: 03/15/05
Posts: 95,368
Loc: underbelly
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Re: Grandfather paradox [Re: Diploid]
#15374190 - 11/15/11 12:40 PM (11 years, 4 months ago) |
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So I guess you could say you have a passing interest in Astronomy.
I had a Celestron 102mm Richfield Refractor for awhile and I borrowed a friends 35mm camera and just got some film at the grocery store for dark shots. I didn't even have a camera attachment but held it up to the eye piece. I got some amazing shots of the moon and a really cool one of the moon coming up behind the mountain silhouetting some trees. The moon behind the trees looked huge and you could see some of the craters on the moon. It was really beautiful and pure luck with the timing and position.
I always wanted to do more but I'm really lazy.
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"Don't believe everything you think". -Anom.
" All that lives was born to die"-Anom.
With much wisdom comes much sorrow,
The more knowledge, the more grief.
Ecclesiastes circa 350 BC
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Diploid
Cuban
Registered: 01/09/03
Posts: 19,274
Loc: Rabbit Hole
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Re: Grandfather paradox [Re: Icelander]
#15374246 - 11/15/11 12:54 PM (11 years, 4 months ago) |
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So I guess you could say you have a passing interest in Astronomy.
Not so much any more, but I was into it big time years ago. I was even a director of the Southern Cross Astronomical Society for a while.
BTW, you can see Andromeda naked-eye under dark skies. It looks like a smudge. In the 90mm you just got, you should be able to resolve the spiral arms under medium magnification. Give it a shot!
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Republican Values:
1) You can't get married to your spouse who is the same sex as you.
2) You can't have an abortion no matter how much you don't want a child.
3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer.
4) We need a smaller, less-intrusive government.
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OrgoneConclusion
Blue Fish Group
Registered: 04/01/07
Posts: 45,406
Loc: Under the C
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Re: Grandfather paradox [Re: Diploid]
#15374276 - 11/15/11 01:01 PM (11 years, 4 months ago) |
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Did you notice my bowing graemlins are out of sync - thus reproving Einstein's theory.
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Icelander
The Minstrel in the Gallery
Registered: 03/15/05
Posts: 95,368
Loc: underbelly
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Re: Grandfather paradox [Re: Diploid]
#15374652 - 11/15/11 02:32 PM (11 years, 4 months ago) |
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Quote:
Diploid said:
So I guess you could say you have a passing interest in Astronomy.
Not so much any more, but I was into it big time years ago. I was even a director of the Southern Cross Astronomical Society for a while.
BTW, you can see Andromeda naked-eye under dark skies. It looks like a smudge. In the 90mm you just got, you should be able to resolve the spiral arms under medium magnification. Give it a shot!
I had some 100mm Astronomy binocs for awhile. Great for Andromeda. Can't wait until it crashes into us. Other than terrestrial the new scope will likely be used mostly for moon gazing and then Jupiter and Saturn. It's funny that I've had much bigger scopes but I've always wanted that C-90 or the Meade version. Should give some great views on those.
The most fun I've had was traveling to the High Desert in Washington State and going to Goldendale Observatory State Park which is a five-acre educational facility on a 2,100-foot-high hilltop. The observatory houses one of the nation's largest public telescopes and has attracted sky-watchers since its opening in 1973. The observatory is open to anyone who wants to view the universe. There is nothing out there but desert for many miles and this one two thousand foot hill with the Observatory. It's spooky fun.
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"Don't believe everything you think". -Anom.
" All that lives was born to die"-Anom.
With much wisdom comes much sorrow,
The more knowledge, the more grief.
Ecclesiastes circa 350 BC
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Desert Elf
Registered: 08/23/11
Posts: 765
Last seen: 9 years, 7 months
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Re: Grandfather paradox [Re: Icelander]
#15374838 - 11/15/11 05:01 PM (11 years, 4 months ago) |
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Can't wait until it crashes into us.
Amusing. 
I imagine this point in history will be something of an 'eye opener' for the species. Oh, many shall awaken this day.
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Om Bhur Bhuvah Svaha
Tat Savitur Varenyam
Bhargo Devasya Dhimahi
Dhiyo Yo Nah Prachodayat
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Icelander
The Minstrel in the Gallery
Registered: 03/15/05
Posts: 95,368
Loc: underbelly
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Re: Grandfather paradox [Re: Desert Elf]
#15374883 - 11/15/11 05:08 PM (11 years, 4 months ago) |
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Well crash is really kind of dramatic. When our galaxies merge it won't be with much of a bang. There is still a lot of distance between those stars.
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"Don't believe everything you think". -Anom.
" All that lives was born to die"-Anom.
With much wisdom comes much sorrow,
The more knowledge, the more grief.
Ecclesiastes circa 350 BC
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Desert Elf
Registered: 08/23/11
Posts: 765
Last seen: 9 years, 7 months
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Re: Grandfather paradox [Re: Icelander]
#15374999 - 11/15/11 05:23 PM (11 years, 4 months ago) |
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Perhaps it will be so gentle it actually 'docks' with our galaxy, parking Earth's significant cosmic other right next door. At this moment we will all get divorced and be introduced by God to our long lost soul mates. All beings finally complete, live happily ever after in peace and joy.
... probably a few casualties along the way though. 
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Om Bhur Bhuvah Svaha
Tat Savitur Varenyam
Bhargo Devasya Dhimahi
Dhiyo Yo Nah Prachodayat
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