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Old 2020-12-08, 04:36   #23
retina
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Quote:
Originally Posted by The Carnivore View Post
... the creation of the universe.
I also considered that, but the laws of physics would tend to disallow you to exist in any form that doesn't kill you and your equipment.

So far as we know there aren't any established laws of physics that disallow time travel to the past. But I personally think it implausible. But that doesn't mean it isn't fun to speculate.
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Old 2020-12-08, 13:24   #24
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Quote:
Originally Posted by Dr Sardonicus View Post
This brings to mind a famous short story I read for the first time in the 1970's, in which anthology I don't remember. I'm sure it's on the publications list at the ISFDB. The story is Adam and No Eve by Alfred Bester. The list begins with the September 1941 issue of ASTOUNDING Science-Fiction.
Interesting. The name "Alfred Bester" is used by Walter Koenig's character on Babylon 5. I was not aware of the author. I just learned that the character is named after the author. I might just need to seek out some of his writings.
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Old 2020-12-08, 13:53   #25
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As to observing the past, it can be done by building a very high resolution and extremely high sensitivity device, which could be aimed at a distant reflector. We could then review images of Earth's past in the reflection.

Alternatively, build a device that travels faster than light and race out to the appropriate distance from Earth, turn around and watch directly.
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Old 2020-12-08, 18:16   #26
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Quote:
Originally Posted by EdH View Post
As to observing the past, it can be done by building a very high resolution and extremely high sensitivity device, which could be aimed at a distant reflector. We could then review images of Earth's past in the reflection.

Alternatively, build a device that travels faster than light and race out to the appropriate distance from Earth, turn around and watch directly.
You tend to run out of photons before looking very far into the past.

That idea has been used in SF before (can't provide a reference, sorry) but it depends critically on the premise that light (or any other EM radiation) can be subdivided arbitrarily many times.

If relativity is correct, a FTL drive is also a time machine.
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Old 2020-12-09, 02:01   #27
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Quote:
Originally Posted by xilman View Post
If relativity is correct, a FTL drive is also a time machine.
But you can only go into the future, never into the past.
Beside of the funny name, haha.
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Old 2020-12-10, 08:10   #28
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Quote:
Originally Posted by LaurV View Post
But you can only go into the future, never into the past.
Beside of the funny name, haha.
Not true (under the premises of special relativity).



http://www.physicsmatt.com/blog/2016...es-time-travel

Last fiddled with by xilman on 2020-12-10 at 09:17 Reason: Add premises.
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Old 2020-12-10, 09:49   #29
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I want to know, where is the airplane of Amelia Earhart.

Regards,

Matt

Last fiddled with by MattcAnderson on 2020-12-10 at 09:52 Reason: spelling of Amelia Earhart
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Old 2020-12-10, 10:37   #30
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Old 2020-12-10, 10:38   #31
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(edit: crossposting, this reply was to Paul)
Complicate. They didn't really need the ship, could have been doing it without.
But for me, say I fly in space for one year with 99% of c, when I come back I would be surprised to see that, while I am one year older, you are eleven years older. That's the example everybody gives. This is wrong in at least two ways, first, we moved relative to each-other with 99% of c. Why I am one year older and you eleven, and not viceversa? If all frames are the same, why was I the one traveling faster? Related to what? Maybe I was the one "sitting" by going in the wrong direction (yes, I know the train paradox, a train going close to speed of light and a candle burning in the middle car), while you were always moving with the same "speed of light" as before I was gone. I can make it a hundred years, or more, traveling faster, closer and closer to c. Then, assuming it is so, did I travel into your future, or you traveled into my past? And what do I need to do (or you) to go back? Think about it. If I can do that (or you), then how can I travel to my own past? Think about it. Yes, time compresses, and dilates, but it never gets back to a former point in exact the same space-time. All traveling is uni-directional. Call it "to the future". There is no "back to the past". That's still my future, or your future. I can't find you younger than I left you, even if I go over c. I may find you infinitely older... Or you, me. That's how I see it. Unless 1+2+3+4+....=-1/12...

Last fiddled with by LaurV on 2020-12-10 at 10:43
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Old 2020-12-23, 06:30   #32
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1 important concept I've learned from the Lost Lands is that the adventurers should always use the Time Hexagon or other time machines on the ground levels above the soils.

Never switch the time when locate inside the skyscrapers or inside the basement parking lots.
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Last fiddled with by tuckerkao on 2020-12-23 at 06:32
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Old 2020-12-23, 10:05   #33
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Quote:
Originally Posted by LaurV View Post
(edit: crossposting, this reply was to Paul)
Complicate. They didn't really need the ship, could have been doing it without.
But for me, say I fly in space for one year with 99% of c, when I come back I would be surprised to see that, while I am one year older, you are eleven years older. That's the example everybody gives. This is wrong in at least two ways, first, we moved relative to each-other with 99% of c. Why I am one year older and you eleven, and not viceversa? If all frames are the same, why was I the one traveling faster? Related to what? Maybe I was the one "sitting" by going in the wrong direction (yes, I know the train paradox, a train going close to speed of light and a candle burning in the middle car), while you were always moving with the same "speed of light" as before I was gone. I can make it a hundred years, or more, traveling faster, closer and closer to c. Then, assuming it is so, did I travel into your future, or you traveled into my past? And what do I need to do (or you) to go back? Think about it. If I can do that (or you), then how can I travel to my own past? Think about it. Yes, time compresses, and dilates, but it never gets back to a former point in exact the same space-time. All traveling is uni-directional. Call it "to the future". There is no "back to the past". That's still my future, or your future. I can't find you younger than I left you, even if I go over c. I may find you infinitely older... Or you, me. That's how I see it. Unless 1+2+3+4+....=-1/12...
Did you read the document to which I linked?

Last fiddled with by xilman on 2020-12-23 at 10:06
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