bob campbell

3 hours ago, md65536 said:

" Google "Andromeda paradox", "

 

10 hours ago, Strange said:

 

 😍 md65536 Thank you for the name of this problem!  The Andromeda Paradox.  I was finally able to find the math proof that I had been looking for.  You're the best!  Isn't this a fun paradox to think about?

I'm very sorry that I have not been able to describe clearly the problem.  I fear your wrath by suggesting that you watch the video from 1:18:30

But I am using the video because as they say a picture is worth a thousand words, and this is difficult to describe.

I understand time dilation but this time difference is far more than simple time dilation can account for in a situation where relative speed difference is so small.

I will attempt once again to ask my question with words.

According to this video, if someone is a very long distance away and they reverse their direction of travel from away from me to toward me, their experience of time is supposed to switch from my past to my future.

I have been trying to understand why their direction of travel makes this much difference. How this is possible to switch from past to future. I get that there is a very small change in time dilation, but it seems that the Lorentz factor would have to switch from positive to negative and even if that happened why would the amount of time vary by so much between past and future?  It has something to do with the very long distances.  If you chose to watch the video you should only have to watch from 1:18:30  till about 1:27:00 to understand exactly what I'm asking. 

5 hours ago, swansont said:

I watched that first minute, and what he's talking about is not well-captured in your question's phrasing.

In a single frame, all clocks can be synchronized, because you can adjust for the delay of a finite speed of light. Similarly, people in a frame can agree on when something happened by applying that delay. An event you observe that is 1 light-second away happened 1 second ago. Everybody in that frame agrees. Let's call that t=0

But moving changes that. If you are moving away, it takes longer for the light to get to you, because in that 1 second, you have moved some distance. So an identical event getting to you happened before t = 0, i.e. in the other frame's past (before t = 0), because an event that happened at t=0 can't reach you in 1 second.

Similarly, if you are moving toward the event, the light arrives faster, because you have reduced the distance.

 

 

That makes a lot of sense, and certainly agree. Light arrives faster, because you have reduced the distance. But what would cause the time frame to be sliced diagonally and swing from past to future by such a large amount into the past and future when the bicycle turns around? 

2 minutes ago, swansont said:

I’m nit required to watch it, by the rules, and it’s a 2.5 hour video, though it starts ~halfway through.

I watched a few seconds and he was talking about simultaneity, and the relative “positioning” of some value of t.

When you say “experience of time” being past or future, simultaneity is a big thing to leave out, if that’s what you want to know about. Is it? (if it is, it has to with how long a photon will take to get to you)

 

I'm sorry this is my first question in this forum.  I did not know that I broke a rule and should not include a video link, even though it describes the problem I'm asking about with great clarity within the first minute. 

I can see that you are having trouble understanding my question, so thank you for your attention, but I believe I found the answer in a http://galileo.phys.virginia.edu/classes/252/lorentztrans.html.

Specifically the cone of light section.

3 hours ago, swansont said:

What do you mean by this? (pretend there’s no video; you have to summarize the argument here)

In summery I don't understand why time dilation would create a situation where reversing direction either toward or away from the observer would swing the one in motion from the observer's future into the observer's past.  The video was very explanatory, were you not able to watch it?

According to this video 1:24:00). < hperlink .

If someone is a very long distance away and they reverse their direction of travel from away from me toward me, their experience of time is supposed to switch from my past to my future.

I have been trying to understand why their direction of travel makes this difference. How this is possible?