The purpose of your life and the origin of our universe.

[RoGeorge]

All we have to do is to send a telescope near the edge of our observable sphere.  The telescope will have it's own observable sphere, and some of that sphere will be outside of ours.  So, the telescope can look for us outside of our own observable Universe, then re-transmit all to us.

Since information can travel at most at the speed of light, by the time that information from the telescope arrives to us, our own observable universe has expanded to cover the telescopes observable universe at the time it sent the transmission.

So no, that won't work.

The volume of the universe we can observe expands at the speed of light.  This has nothing to do with inflation, but just the fact that information travels at light speed.

Not sure I understand, but I see no reason why an outpost/relay won't work.

Yes, the viewing range is increasing at the speed of light, but space itself in between expand even faster, so what we can see today at the very edge of the visible sphere, won't be possible to see tomorrow.

The current mainstream physics agrees that the space keep "expanding", and at the edge of our viewing range the total expanding becomes "faster than light".  That is why, with each day we will be able to see less and less stars, even thought the stars are still there.  After minute 8:00 in the next video it is stated exactly this.

The dude explaining is Dr. Don Lincoln https://en.wikipedia.org/wiki/Don_Lincoln , he has a PhD in physics and is currently working at the Fermi Lab, so it's safe to assume he's talking about mainstream physics in this video:

[Ground_Loop]

The answer to your questions can be found in the Chart of Nuclides

https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html

[Ed.Kloonk]

[Nominal Animal]

All we have to do is to send a telescope near the edge of our observable sphere.  The telescope will have it's own observable sphere, and some of that sphere will be outside of ours.  So, the telescope can look for us outside of our own observable Universe, then re-transmit all to us.

Since information can travel at most at the speed of light, by the time that information from the telescope arrives to us, our own observable universe has expanded to cover the telescopes observable universe at the time it sent the transmission.

So no, that won't work.

The volume of the universe we can observe expands at the speed of light.  This has nothing to do with inflation, but just the fact that information travels at light speed.

Not sure I understand, but I see no reason why an outpost/relay won't work.

By the time the information from the outpost reaches you, you can observe everything the outpost could at the moment it sent the information.

You forget, information too is limited to the speed of light, and you do not observe things as they are at this moment, but how they were in the past; the further away, the deeper in the past.


Consider a 2D example, with the observer at origin, and the Big Bang at time t=0.  Excluding inflation (expansion of space), the edge of the observable universe is at distance r=ct.  Let's say you have a probe at distance d; it too can observe a disk of radius r=ct.  At time T, it observes X in the opposite direction of origin, at a distance of cT; thus, this something is at distance cT+d from origin.  It sends the information from that to origin at light speed.  The information arrives at time t=T+d/c.  The radius of the observable universe at origin at time T+d/c is c(T+d/c) = cT+d.  This means that origin itself can observe the point X by the time the information arrives, no matter what d is.

Even if the universe expands, the only way the information about X can reach the origin faster via the probe than directly, is if the expansion is very non-uniform.

Essentially, you are drawing a triangle, with the one side from X to origin, one side from X to probe, and the last from probe to origin.  Your probe/observatory idea is essentially claiming that the length of the geodesics (shortest paths) from X to probe and from probe to origin, can be shorter than the geodesic directly from X to origin.  When the probe is between X and origin, that is not possible in any geometry.  When the probe is elsewhere, that is only possible in very weird geometries; stuff like folds in space.

[RoGeorge]

Here's a short animation to help visualizing what I was trying to explain:
- viewable range increases each day
- space expands with time
- speed of light is considered constant

Space expansion is not much, but over huge distances it all adds up while the speed of light is said to stay the same, so after enough distance the expansion will become faster than light.  As a result, more and more stars are leaving our viewable range, even they are still shining.

The Pale Blue Dot is the Earth, the red dot is the outpost with a telescope broadcasting what it sees from the outpost viewpoint.  At some time in the future, even the outpost will run out of our reach, but for as long as the outpost is in our direct view, then we will receive what the outpost transmits (the view of all the stars inside the red circle), some of each we wouldn't be able to see without the outpost, because they are outside our green circle of direct view.

Note how the circle of view slightly increase in size, yet stars keep migrating from the inside to the outside of any circle.

Code: [Select]

#!/usr/bin/env python2.7

'''
How to look outside our observable Universe using an outpost:
-------------------------------------------------------------
    - the WHITE dots are the stars
    - The Pale Blue Dot is the Earth
    - the GREEN circle is the obsarvable Universe, looking from Earth
    - the RED dot is an outpost telescope, continuously broadcasting its view
    - the RED circle is the observable Universe, looking from the outpost

    - note that the circles' radius increases with time, at the speed of light, c
    - note that even the observable radius keeps increasing,
      with time the stars are leaving the observable circles because space expands
    - note how with time, will be less and less stars to view,
      even thought the stars are still shining out there,
      just that they are running away faster than the speed of light

    - by receiving the broadcasted view from the outpost,
      we will be able to study all the stars seen by the outpost,
      including the stars that otherwise will be outside of our direct reach,
      but are still reachable from the outpost viewpoint
    - after a while, even the outpost will run away outside our view
'''


import pygame as pg
import random


WIDTH = 1920
HEIGHT = 1080
ANIMATION_FPS = 10

WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
LIGHT_BLUE = (32, 64, 255)

NR_OF_STARS = 2000

INFLATION_COEF = 0.01
OBSERVABLE_START_RANGE = 200


class Dot:
    def __init__(self, x=0, y=0, color=WHITE, thickness=3):
        self.x = random.randrange(1, WIDTH-1)
        self.y = random.randrange(1, HEIGHT-1)
        self.color = color
        self.thickness = thickness

        self.x_now = self.x
        self.y_now = self.y

    def __call__(self, x, y, color, thickness):
        self.x = x
        self.y = y
        self.color = color
        self.thickness = thickness

    def xy_now(self, time=0):
        self.x_now = int(round(self.x * (1 + time * INFLATION_COEF)))
        self.y_now = int(round(self.y * (1 + time * INFLATION_COEF)))


screen = pg.display.set_mode((WIDTH, HEIGHT))
pg.display.set_caption("Observable vs Expansion")
clock = pg.time.Clock()

light_day = 1

# populate the Universe with stars
random.seed(1)
stars = [Dot() for i in range(NR_OF_STARS)]

# add Earth to the Universe
Earth = Dot()
Earth(200, 150, LIGHT_BLUE, 10)
stars.append(Earth)

# add an Outpost to the Universe, inside the viewrange of the Earth
Outpost = Dot()
ox = Earth.x + int(round(3.0/4.0 * 2**0.5/2 * OBSERVABLE_START_RANGE))
oy = Earth.y + int(round(2.0/4.0 * 2**0.5/2 * OBSERVABLE_START_RANGE))
Outpost(ox, oy, RED, 5)
stars.append(Outpost)


# animation loop
stopped = False
while not stopped:
    # Frames Per Second
    clock.tick(ANIMATION_FPS)

    for event in pg.event.get(): # User did something
        if event.type == pg.QUIT: # If user clicked close
            stopped=True # Flag that we are done so we exit this loop
     
    # Clear the display buffer and set the screen background
    screen.fill(BLACK)

    for star in stars:
        # Update the star positions as per today's view and draw the star
        star.xy_now(light_day)
        pg.draw.circle(screen, star.color, [star.x_now, star.y_now], star.thickness)

    # Draw today observable ranges from Earth and from Outpost
    pg.draw.circle(screen, GREEN, [Earth.x_now, Earth.y_now], OBSERVABLE_START_RANGE+light_day, 1)
    pg.draw.circle(screen, RED, [Outpost.x_now, Outpost.y_now], OBSERVABLE_START_RANGE+light_day, 1)

    # Display the screen buffer
    pg.display.flip()
    pg.image.save(screen, "frame" + str(light_day).rjust(5, '0') + ".png")

    # A day passes with each frame
    light_day += 1

pg.quit()


[Mechatrommer]

how can we possibly see something that we left at now greater than the speed of light relatively (the origin) we cant even look at whats inside the black hole right next to us. let alone sending outpost to the place that requires billions of light years to travel and then try to send back an information. all of that are... fancy assumptions... that we thought we went too far.

[Nominal Animal]

I understand, RoGeorge, but that's not how reality works.  I am not sure how to explain it better to you.

Distances we measure or estimate are actually the lengths of spacetime geodesics.  One end is always in the past with respect to the other end.
To get purely spatial distances, we need calculations that take the rate of the expansion of the universe (which has not been constant) into account.

Consider a thought experiment.  You have two points, A and B, one meter apart along a stretching wire.  Ants appear one after another at A, each one touching the preceding and succeeding ant, and start walking towards B at a constant local velocity c.  The rate of expansion of the wire is constant, but such that at least one ant from A will reach B.  However, the ants also grow/stretch at the same rate as the wire (because light is also embedded in space), so consecutive ants will stay in touch.  Will the stream of ants end at some point?  No, but there may be a "last" ant that just continues to stretch and stretch, and never ends.

Information behaves like those ants.

Objects don't pass beyond the observable universe, just because the observable universe expands at a rate where the spatial separation between two points increases faster than the speed of light.  The observable horizon is always at ct, where c is the speed of light in vacuum, and t is the age of the universe, and this distance or separation is measured as a spacetime geodesic, with one end in the past with respect to the other.
What happens with light (and with gravitational waves, it is assumed) is redshift.

Please read the Theory section of the cosmological inflation Wikipedia article.  Essentially, although the universe expands, because of the exponential inflation during very early universe -- about 10^-32 seconds old universe expanded from the nanometer scale to ten lightyears --, light from different parts of the universe has not reached all other parts yet, these "causally connected patches" still expand; more and more regions come into contact.  The "causally connected patch" is roughly what we call the observable universe.

Like the ant analog, the causal patches never shrink, as they expand at the speed of light at the boundary; nothing ever passes from inside a patch to outside a patch.  Each passing second, more and more ant sources reach us for the first time.  It is not the radius of the observable universe right now, in purely spatial terms, that expands at the speed of light.

If we observe a quasar now, and note the information from it traveled to us for 12 billion years, the distance between it and us right now is something like 40 billion light years.  The spacetime geodesic is 12 billion lightyears long.  Which is the "right" distance?  This is also the problem with visualization of spacetime and the expansion of the universe.

[nigelwright7557]

Oh dear...
This thread can only spiral down hill quickly.   

We are here through flukes of nature.
Blame your parents for you being here.
They give us the gift of life but also the gift of death too.
The positive and negative universes add to make zero so it could be we really arent here.