B Can We See Our Past? - Milky Way & Hubble Telescope

[GraemeSRC]

No. You're still thinking of the marbles as moving in a static 3D space. Try thinking instead of static marbles in a space which is expanding. Then every marble sees all of the marbles moving away from it, with marbles that are further away moving away faster. It is really impossible to visualize in 3D, which is why we focus on the mathematics.

In fact the string of marbles along a line from the centre to the edge of the sphere would retain their proportional spacing as you stretched them out. The rate is not less towards the centre. If they were evenly spaced to start with they would remain so.

 

[GraemeSRC]

Just a small final thought before I head off to bed. About the OP's question of whether we can see our past.

In fact that is all we can see. Its simply a question of how old what we see is. From the fact that light does take time to travel from the observed to the observer, however short the distance might be, to the time it takes to process that incoming data to form a perception, it can never be instantaneous. If we were able to look at ourselves in a mirror placed on the moon, which is not entirely unfeasible, we would see ourselves a few seconds ago and the delay would be easily noticeable.

 

[MidgetDwarf]

@Viola. The best way to learn is to put in the effort to do so. What you are doing is called being lazy. You are expecting people to teach you material that took people hundreds, if not more, years to understand in a short interval of time. If you are truly interested in learning. Pick up a mathematics/ introductory physics book, and start learning.

You say you are not formally educated... What is stopping you from becoming acquainted with the field? Hint: the answer to this question is somewhere in my post.

 

[phyzguy]

In fact the string of marbles along a line from the centre to the edge of the sphere would retain their proportional spacing as you stretched them out. The rate is not less towards the centre. If they were evenly spaced to start with they would remain so.

Yes, they remain evenly spaced. But they are getting further apart. There is no center - I never said there was a center. You should imagine that the string of marbles (or ants) is infinitely long. But each marble will see the others as moving away, and see the marbles that are further away moving away faster.

 

[phinds]

Many of these videos are made by respected experts in their fields, like the Nobel Laureate Brian Schmidt" in the YouTube video I mentioned. Why would they want to give false information? It is easy to find out who the authors of these videos are, and if they are reputable scientists. I don't mind a bit of "dumbing down" as line as they are telling me the truth.

Ah, now THERE'S a real problem. You think that because the presenter is a "respected expert" then what he/she says in a pop-science presentation will be real physics. Nothing could be further from the truth. Pop-science is made to sell soap / cars / etc, not to teach anyone actual science. Perfectly respectable scientists will say things in pop-science presentations that would get them hooted out of the room in a real physics discussion, and they know it. "Telling the truth" as you put it often requires much more time and explication that one can possibly fit into short presentations like one hour.

That fact is the bane of our existence here on PF. We are constantly having to correct misconceptions that people like you take away from pop-science presentations. I watched quite literally dozens of such things and read similar books and I found that there are common statements that occur so often that it is quite reasonable to assume that they are correct (even though they are not). When I got her to PF I found out that much of what I "knew" was totally wrong. You are running into the same problem.

My only saving grace was that I really wanted to learn so rather than ask questions at first, based on what I had come to realize were clearly misconceptions, I just read LOTS of posts here, plus some more serious books, and learned enough to make my questions based on a bit more knowledge. I still spend MUCH more time here reading threads than asking questions.

 

[OCR]

I still spend MUCH more time here reading threads than asking questions.

So do I, but I'm going to ask one now. . .

When I got her to PF. . .

Did you miss the "a" an "e" key ? .

 

[phinds]

Did you miss the "a" an "e" key ? . View attachment 247014

Hey, *I'M* the head nitpicker here

It was indeed a slip of figner.

 

[OCR]

Hey, *I'M* the head nitpicker here

. .
. . And, I believe you. . . .

.

 

[Umang Soni]

It's closer. The Sun, for example, is only 8 minutes away. The light from the Sun any older that than is traveling away from us; not towards our telescopes.

absolutely correct ,,,,broadly the light rays which we observe at present is as old as its distance ...now we only can see the past of that light source ( or the subject which is reflecting it ) corresponding to is distance from observer ... it is impossible to see its past ...its like its distance puts limits on the our observation ..

 

[sophiecentaur]

Thank you. I must apologise to Jbriggs444. I have a bad habit of arguing with people when I don't understand something.

IS there any other PF member to whom that doean't apply? Don't worry. @jbriggs444 has a thick skin like (most of) the rest of us.