How Far Can You Look?

Aug 14, 2020
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How far into 'space' (particularly into the 'space' of the Universe) can you look? Can anyone look? Using any kind of instrumentation whatsoever? How far?
 
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rod

Oct 22, 2019
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Depending upon where you view from, unaided eye observations of M31 is possible as well as M33. I can see M31 from my location. M31 is considered to be about 2.5 million LY distance from Earth. No telescope or binoculars used here to see that far :)
 

rod

Oct 22, 2019
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One point I will make here. Stellar parallax is the only direct method of measuring distance to stars. Here is a recent report showing this. VLBA makes first direct distance measurement to magnetar, https://phys.org/news/2020-09-vlba-distance-magnetar.html Also,
A magnetar parallax, https://arxiv.org/abs/2008.06438
“XTE J1810-197 (J1810) was the first magnetar identified to emit radio pulses, and has been extensively studied during a radio-bright phase in 2003−2008."

My observation. I checked 0.40 mas parallax using my astronomy spreadsheet. Similar distance value obtained to this report, 2500 pc distance. 0.40 mas is a very tiny parallax measurement. 61 Cygni star parallax is 314 mas and distance a bit more than 3.18 pc.
 
Jun 1, 2020
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The CMBR is the most distant emission source - 13.8 billion lyrs distance and years. This started as yellowish-white, or perhaps orangish-white light (3000K) but has redshifted into the microwave band.

This incredible burst of emission propagation took place about 380k years after the beginning. Prior to the expansion causing cooling to ~ 3000K, the flood of light was constrained to scatter to and fro over very short distances making it a sea of light. When the cooling allowed all those electrons to be captured by all those protons, the light was free to travel onward, like race horses bursting out of their chute.

There is some hope that a neutrino "telescope" can be made to see between those events.
 
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rod

Oct 22, 2019
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FYI, it is important to note that the CMBR distance of 13.8 billion LY distance is an indirect method of calculation vs. the parallax method I cite for the magnetar distance of 2500 pc in post #3. For comparison, 13.8 billion LY distance is 4.23E+9 pc distance. No telescope has made a direct distance measurement like this so far.
 
Aug 14, 2020
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I worded the question badly, but no matter, everyone so far has the answer wrong. You are answering as if I had asked how far into relative time's 'past' can you look? That is not what I ask. I ask, "How far into 'space' (particularly the space of the Universe), can you look? Can anyone look? Using any kind of instrumentation whatsoever? How far?" You can call it a trick question if you want, but no one answered the question I asked. No one.

There is only one 'time' equivalent to "space" and that is real time. How far into real time (particularly the real time of the Universe) can you look? Can anyone look? Using any kind of instrumentation whatsoever? How far?

I asked the question because someone tried to tell there is only one universe out there, the 'observable universe'. Some others have tried to tell me that there is no more than just one. Your answers and my come back point to two universes, minimum. One relative time universe, the one all of you were dealing in, and one real time universe, the spatial universe, the one none of you were thinking of.

You can't observe infinity. You can't observe any object in 'space' (in its real time). Relative time-wise you have to advance upon it from past to future to close with it. Even if it is a billionth of a billionth of a billionth of a billionth of a billionth of a second's distance in light time from you, your angle of approach to it is from a past fast forwarding through a future to close with it. The farther you are from it, immediate object or subject event, the farther it is in some future (relative time) from you.... even though in space, in real time, it is level with you (though it be 14 billion x 6 trillion miles from you, or even 14 quintillion (14 zillion (whatever)) x 6 trillion miles from you).

So, another way to ask my question is: How far into the 'future' (particularly the future of the Universe), can you look? Can anyone look? Using any kind of instrumentation whatsoever? How far? To put it, the question, right, how far can you see into 'space'?
 
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Oct 22, 2019
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Atlan0101, your post #6 question is interesting. "How far into the 'future' (particularly the future of the Universe), can you look?"

I would start where Galileo did when he looked at Jupiter, observing the Galilean moons moving around Jupiter in a telescope. Galileo documented his observations and today, some 400 years later, I can still see what he did but with better telescopes :) So when I look at Io moving around Jupiter using my telescope, do I see Io in the future, or the past of Io because of light-time to Earth?
 
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So, another way to ask my question is: How far into the 'future' (particularly the future of the Universe), can you look? Can anyone look? Using any kind of instrumentation whatsoever? How far? To put it, the question, right, how far can you see into 'space'?
A couple of things might help here...

We only observe, across the entire EM spectrum, what is known as the observable universe. A century ago, the universe was held to be likely infinite, based on philosophy as the science was too inadequate to even ask the question objectively. It was about 90 years ago before they agreed there was more than one galaxy and that took the largest telescope & Hubble to provide clear evidence.

The idea of other universes are just that, ideas. Some mathematical wizardry by Greene and others suggest and even claim there are a huge number of universes out there. This is metaphysics because no one can offer what science demands -- objective evidence. Objectivity means it can be tested over and over by other scientists and if their conclusions agree then you have something of merit. Theories, remember, can't be proved but they must be falsifiable, so science keeps looking for more objective evidence that might do so. Falsifying a major theory could lead to a Nobel Prize, so falsifying isn't a bad thing.

Time and space are woven together (Einstein) in a non-intuitive way. We use light (all bands) from afar to tell us what's out there. Light has a fixed speed, so we have to wait for it to get here. Or, IOW, if we know the distance to any object we can determine how much time expired for that light to reach us. The meter itself is no longer a stick in Paris but is based on the speed of light since it is the same in all reference frames.

There is abundant evidence that the BBT is valid (never proven, of course) and that the many lines of different objective evidence greatly favors a 13.8 billion year time frame based on our clocks. Since light travels in one year the distance of one light-year, then we can say that the CMBR light, by our clocks, took 13.8 billion years to reach us and, thus, came from 13.8 billion lyrs away.

Since the universe is expanding, the universe is much larger than when the CMBR light was released and free to travel. If your magic wand is used to freeze the entire universe, you would likely measure that same 13.8 billion lyrs distance to have stretched to about 40 billion lyrs, IIRC.

Does that help?
 
Jun 1, 2020
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Atlan0101, your post #6 question is interesting. "How far into the 'future' (particularly the future of the Universe), can you look?"

I would start where Galileo did when he looked at Jupiter, observing the Galilean moons moving around Jupiter in a telescope. Galileo documented his observations and today, some 400 years later, I can still see what he did but with better telescopes :) So when I look at Io moving around Jupiter using my telescope, do I see Io in the future, or the past of Io because of light-time to Earth?
It's interesting that Roemer discovered in 1676 that those orbital periods for the Moons all were slower when Earth was farther away from Jupiter, and faster when closer. This allowed him to recognize that the speed of light isn't infinite and he was able to somewhat accurately calculate the speed of light.
 
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Oct 22, 2019
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Helio's observation about Roemer and light-time at Jupiter in post #9 is why I ask my question in post #7, "So when I look at Io moving around Jupiter using my telescope, do I see Io in the future, or the past of Io because of light-time to Earth?"

When folks ask "How far into the 'future' (particularly the future of the Universe), can you look?", my reply will be that we must go back to Galileo and the moons of Jupiter to find the answer. Much heliocentric astronomy was discovered and learned there. How far into the future can I see can be answered at Jupiter and the Galilean moons too :)
 
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Helio's observation about Roemer and light-time at Jupiter in post #9 is why I ask my question in post #7, "So when I look at Io moving around Jupiter using my telescope, do I see Io in the future, or the past of Io because of light-time to Earth?"
It's impossible to observe anything in the future as, by formal definition, it ain't here yet. If we are observing something it is either something now or something that has come from the past. All light entering the eye took time to reach the eye, hence all light is from the past. If we know the distance, however, then we know the time it took for light to get here.

In a nearby lightning strike, if we divide the time it takes thunder to reach our ears by 5, then we have a close value for its distance from us. It's hard to appreciate that light takes time to reach us, but for a mile or two away, the nanoseconds are not important enough to take into consideration.

As for the future, tachyons have been hypothesized, though unlikely, which could allow us to see a little bit into future events of light coming our way, much like knowing thunder is coming once we have seen lightning nearby.
 
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rod

Oct 22, 2019
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Helio's thinking in post #11 is correct because of light-time to Earth. When I view the Galilean moons moving at Jupiter, that is their past I see, those moons have already moved to some other location at Jupiter when I see them in the telescope eyepiece because of light-time. The same is true for my observations of Mars last night using my telescope. The same is true for telescope observations of the bright star Sirius or the bright stars in Orion's belt, now visible in early morning skies. When it comes to tachyons, my telescopes do not see these particles :)

Helio, very good. You pass my Galileo test :)
 

rod

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Some following this thread may find this report interesting. Originally published in January 1848. “The eclipses of the moons of Jupiter had been carefully observed and a rule was obtained, which foretold the instants when the moons were to glide into the shadow of the planet and disappear, and then appear again. It was found that these appearances took place sixteen minutes and a half sooner when Jupiter was on the same side of the sun with the earth than when on the other side; that is, sooner by one diameter of the earth’s orbit, proving that light takes eight minutes and a quarter to come to us from the sun.” —Scientific American, January 1848, https://www.scientificamerican.com/article/jupiter-eclipse-proves-the-speed-of-light/

The finite speed of light discovered at Jupiter by observing and timing Galiean moon eclipse events. Started in the early 1670s with Ole Romer astronomer who worked on this in 1672 with more details published in 1676.
 
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Helio's thinking in post #11 is correct because of light-time to Earth. When I view the Galilean moons moving at Jupiter, that is their past I see, those moons have already moved to some other location at Jupiter when I see them in the telescope eyepiece because of light-time. The same is true for my observations of Mars last night using my telescope. The same is true for telescope observations of the bright star Sirius or the bright stars in Orion's belt, now visible in early morning skies. When it comes to tachyons, my telescopes do not see these particles :)

Helio, very good. You pass my Galileo test :)
Thanks! :)

As for tachyons, these are likely not observable in the visible band, even if they exist. [I'm guessing.] It will be a huge discovery if they become a part of mainstream science.
 
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Thanks! :)

As for tachyons, these are likely not observable in the visible band, even if they exist. [I'm guessing.] It will be a huge discovery if they become a part of mainstream science.
I suspect they, 'tachyons', would have a second name and second dimension of existence. To wit, 'gravitons'.
 

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