Is Time Travel Possible? Part 2: Back to the Past

Is time travel to the past a possibility, even in principle? In this video we explore this idea and its ramifications. If it can be achieved, how could we go about doing it? This is the final part to our two video series on time travel. Part 1 discussed time travel to the future and what that even means.
Thank you to all of my Subscribers and Likers! I really appreciate all of your support and you are the reason I share my passion for science and these Big Questions!
CONTENTS OF VIDEO:
0:00 Introduction
0:36 Stephen Hawking's Time Traveler Welcome Party
2:20 General Relativity and Closed Time-Like Curves
3:47 Negative energy and negative mass
4:31 Faster than light travel
5:44 Tachyons
6:20 Wormholes and warp drives
7:15 Ronald Mallett's Time Machine
8:25 3 Physical issues with PAST time travel
8:56 Time travel paradoxes
11:06 Conclusion
*****************************
Links to my 3 books on physics:
Volume 1:
"Everyone's Field Guide to Physics: Volume I: The Familiar World": www.amazon.com/Everyones-Fiel...
Volume 2:
"Everyone's Field Guide to Physics: Volume II: The Ethereal Trinity": www.amazon.com/Everyones-Fiel...
Volume 3:
"Everyone's Field Guide to Physics: Volume III: The Unfamiliar World": www.amazon.com/Everyones-Fiel...

[@Turretdown_Hero]

This channel must blow up. So much better than all crap AI narrated bull%hit. Keep it up!

[@TurtlesWayDown]

Much appreciated!

[@daviddean707]

It may all prove to be rather less difficult later on.

[@lucofparis4819]

If my guess is as good as yours, I might as well offer you my perspective. Let's entertain the idea that someone in the future could just board a spacecraft equipped with some kind of time propulsion. The ship "accelerates", or rather, starts to change course in the 3+1D universe. It now begins to "move" at less than 1 second per second in time. At some point, its 'timeometer' will display '0 second per second', before presumably starting to display some negative value per second. Except it won't, because our time traveler is currently busy looking at the timeometer displaying '0 second per second'. Since the ship is no longer 'moving in time' at any rate, there will never be a time when ir actually 'travel back in time' and is now effectively frozen in the Presentist wet dream, where only the Present exists for this traveler. Suffice it to say, this rate of zero change or zero time that the traveler would eventually have to go through during the "acceleration" of the time engine, seems to be pretty much the end of the journey. This apparent temporal barrier seems just as impossible to pass as the speed of limit seems impossible to reach. Again, just like with the tachyon idea, we could imagine a spacecraft already 'moving' at some negative seconds per second, effectively travelling back in time. But how exactly would our time traveler board such a ship in the first place?

[@user-ix3uy5zd2i]

is time travel to past future really possible and how i want to do it i am from india please help me

[@daviddean707]

Apart from the question of honesty, did it make any difference that invitations were sent after the event and not before?

[@lucofparis4819]

Random schmucks from the present could have decided to attend, had he sent his invitations in advance. It shouldn't make any difference for a time traveler, however, hence why he sent them after the event.

[@waynerawlings8599]

The thing with these paradoxes is that we’re seeing it all from an observers reference frame, outside of time itself. If we think about this from the time traveler’s point of view, we have to realise that once he has gone to the past, that past is now the present for him. The future where he’s from hasn’t happened yet. So he should be able to do what he wants. However the key thing with time travel that everyone over looks is “intention”. If a time traveler intends to go back and kill grandad, the “intention” to do so will just dissolve. Even if he managed to do it. When he gets back to his original present. His memory of doing it will be gone, as if it never happened., therefore it didn’t. Time and time travel are real but in our minds

[@lucofparis4819]

The underlying problem highlighted by those paradoxes is the equivocation between linearity (Past=>Present=>Future) and non-linearity (Past=Present=Future) in these traditional philosophers' mindsets. However if Past, Present, and Future all exist simultaneously, then causing the death of either grandparent also annihilates the time traveler, but does not necessarily prevent him from actually doing so. There is no paradoxe, nor is there any fortunate dissolution of murderous intent, only some very silly means of committing suicide by timeborne murder.