Hi! Have you ever wondered at the phenomenon of time reversal? I mean you actually moving back into your past? Like if you rewind the movie clip and see the events in the backward direction?

For example, if the time starts moving in the negative direction of its axis[physical factors aside], then what would happen? Like if you threw a ball from the 10th floor of a building and then you actually moved back in the time, then while moving back, you'd see the ball moving in the upward direction[anti-gravity]...THAT'S HILARIOUS!

AND now something even BIGGER! One moves into his/her past and kills his/her grandfather....now how can he/she exist in the present if her/his grandfather was killed? Like, how could his/her father be born?

5 years, 8 months ago

MarkdownAppears as
*italics* or _italics_ italics
**bold** or __bold__ bold
- bulleted- list
• bulleted
• list
1. numbered2. list
1. numbered
2. list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1paragraph 2

paragraph 1

paragraph 2

[example link](https://brilliant.org)example link
> This is a quote
This is a quote
    # I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
# I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
MathAppears as
Remember to wrap math in $$...$$ or $...$ to ensure proper formatting.
2 \times 3 $$2 \times 3$$
2^{34} $$2^{34}$$
a_{i-1} $$a_{i-1}$$
\frac{2}{3} $$\frac{2}{3}$$
\sqrt{2} $$\sqrt{2}$$
\sum_{i=1}^3 $$\sum_{i=1}^3$$
\sin \theta $$\sin \theta$$
\boxed{123} $$\boxed{123}$$

Sort by:

At a microscopic level physics is reversible, in that you can play the 'movie' backwards or forwards. However, at a macroscopic level there is an arrow of time, time runs in one direction and not the other (c.f. arrow of time). As for the killing ones grandparents, that's a slightly different issue. We don't believe that one can construct 'closed timelike curves' in physics, which is what this implies. A closed timelike curve means that you can actual travel back in time into your own past, which is what you need to cause these types of paradoxes. The conjecture that we don't have closed timelike curves is due to Hawking and goes by the name of the chronology protection conjecture. In his words, "...the best evidence we have that time travel is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future."

Staff - 5 years, 8 months ago

Does that mean that Einstein's theory regarding time being manipulated along an axis is wrong? If not then what and how? And if you don't mind then can you please refer me to some nice books on these kinds of interesting subjects?

- 5 years, 8 months ago

Einstein's not wrong. If you want to learn about the nature of time in relativity and the universe, start with Sean Carroll's TED talk, which you can watch online.

Staff - 5 years, 8 months ago

What about the future? If one goes into ones future and dies there, how can he be back to his past?

- 5 years, 8 months ago

Thanks a lot. I'll get to that as well, i.A

- 5 years, 8 months ago

http://www.marxists.org/reference/archive/einstein/works/1910s/relative/relativity.pdf in Einstein's own words without the math.

- 5 years, 8 months ago

I don't have any answer to any of your questions but these are my views. Hope you would like them. Even if the time starts moving in the negative direction we probably won't notice anything or do we? I don't think so. All the thoughts would go in the reverse direction and we won't likely be able to think what's really happening. So, what would be going in our minds. I don't know. Further, I belive the answer to grandfather killing paradox is that you cannot kill your grandfather no matter what you do. May be yes or not. I don't know. Lol this is confusing. I will think about it.

- 5 years, 8 months ago

The real paradox that I find in all time travel movies is that changing something in the past destroys the very reason of going to the past.

- 5 years, 8 months ago

My weird nonsense theory on time. It is likely one may feel irritated by reading this. Read at your own risk. There is not much physical evidence to what I have written here.

Law1: Time is what *created by our "free mind". The more the "free mind" is available the more fast the time would flow. "Free mind" is the part of mind which is not in use.

In order to explain what is free mind I will give two examples. Have you ever noticed when you think too much, with lots of concentration time flows slowly like when you are writting your answers in last 10 minutes of your test. In this case, the space alloted to "free mind" is very less because space is being used by concious mind to do something and hence time flows slowly. Another example is when you sleep at night. All you think is very less and close to nothing. This time the the space alloted to "free mind" is much large and hence time flows fast and you wake up in no time in the morning. So free mind controls the flow of time. The more the space to "free mind" is available the more faster the time would flow. Without free mind there is no time.

- 5 years, 8 months ago

That's one's perception of time, it's very different from the real time.

- 5 years, 8 months ago

Is that science? If so then explain it in scientific terms please.

- 5 years, 8 months ago

No, its just an idea right now. I would look forward to prove this.

- 5 years, 8 months ago

That's right!

- 5 years, 8 months ago

Time cannot move backwards, even if it did, you cannot observe it, even if you did, it wouldn't be like you reversing a video on windoes media player.

Also, the assumption of going backwards in time and killing an ancestor won't take us anywhere, because it simply cannot and won't happen.

- 5 years, 8 months ago

if parallel universes exist,u could go back in time and kill your grandfather,in another alternate universe,but it sounds more like sci-fi at this moment

- 5 years, 8 months ago

The answer contains parallel universe terminology with an 'if'. The point is that, if parallel universes exist then life vs time graph can never be a function coz there will be two lives at a time. It means if there are infinite universes, there can be infinite me's. That sounds beyond realistic contours I think.

- 5 years, 8 months ago

Though it is mind boggling to think that essentially there are exact replica of us in the vastness of space,string theory is revealing to us that there could me parallel universe,and if there is a parallel universe i think it is in another dimension,we can't see it.

- 5 years, 8 months ago

You want to think about parallel universes, try the many worlds interpretation of quantum mechanics. It'll blow your mind.

Staff - 5 years, 8 months ago

Dimension here refers to what? Secondly, how can we not observe it? I mean, is it something invisible?

- 5 years, 8 months ago

Comment deleted Apr 15, 2013

I think now is a good time to delete this comment...:D

- 5 years, 8 months ago