# Could something theoretically observe the first light in the Universe?

Light travels at 299,792,458 meters a second. If you look at something that is 299,792,458 meters away, you're observing light from 1 second in the past.

If an observer's distance from a light source exceeds the distance required for light to travel to the observer, and we have the advanced technology required to see something that far away, and also know the exact location in space to look (although data transfer speeds are bottle-necked by light-speed, but let's imagine that bottle-neck doesn't exist...), could we theoretically see the start of that light source?

You would also need to know the location of the Universe's first light source, but if we did, could we theoretically go one step further and go outside the radius of first light omitted from the Universe's centre and watch the birth of the Universe?

• cosmic microwave background is what you are looking for?en.wikipedia.org/wiki/Cosmic_microwave_background – Ch.Siva Ram Kishore Mar 25 at 12:23
• @Ch.SivaRamKishore Like how when light from an omitter moving away from us enters our hubble sphere the wavelength appears differently and more stretched out? So it becomes more faint and disappears into the background noise... Thanks for the link! – Lewis Harris Mar 25 at 12:44
• The first light source was the whole universe. See physics.stackexchange.com/q/136860/123208 – PM 2Ring Mar 25 at 16:18
• @PM2Ring I suppose there is easier ways to simulate the beginning of the universe – Lewis Harris Mar 25 at 18:36

If an observer's distance from a light source exceeds the distance required for light to travel to the observer, and we have the advanced technology required to see something that far away, and also know the exact location in space to look (although data transfer speeds are bottle-necked by light-speed, but let's imagine that bottle-neck doesn't exist...), could we theoretically see the start of that light source

Assume that the sun exploded right now. We would see the effect of it after 8 minute later, since that is the time it takes for the light travel between the sun and the earth.

This is true for any event. Even when you look at the mirror you are seeing the past. We always see the past. How past, well it depends on the distance between the source and the event (At this point things can be affected due to expansion of the universe, which is an important factor in large distances)

You would also need to know the location of the Universe's first light source

There is no such location in the universe. In other words, there's no direction which you can point at and say "that's where the universe started". Think about the surface of a ball. You are a 2D creature living on the surface. There's no physical center for this surface. The center lies inside the ball which a 2D creature can never point/reach.

but if we did, could we theoretically go one step further and go outside the radius of first light emitted from the Universe's center and watch the birth of the Universe?

We cannot because of there's no such place. There's no center for the universe.

And btw CMB is not the "first light". There was always light (photons). In the early universe, these photons were coupled to the baryonic matter. Which implies that the photons were always interacting with the particles. When they decoupled from the matter, these photons became free and that is the CMBR. It's just an event that occurred in the early universe. If we had some sort of a superpower to detect very low energy neutrinos (about $$1.9K$$) we would see the Cosmic Neutrino Background which occurred around $$1s$$ after the big bang. Meanwhile, the photon decoupling (Event that created CMBR) occurred around $$300,000$$ years later.

http://www.astro.ucla.edu/~wright/nocenter.html

Theoretically, you can go outside of our observable universe. But thats a completely different story from what you are describing.

• Great information just the kind of answer I was looking for. I suppose I meant anything between observable wavelengths that can be observed by our instrumentation. Theoretically could someone observe old waves is what I'm asking, but know that those waves are so old that the reason that they haven't got to them yet is because the source of the wave is so far away. – Lewis Harris Mar 31 at 16:46

The cosmic microwave background is the farthest back we can see due to before that the entire universe was composed of opaque plasma, if someone somehow went far enough to observe the birth of the universe they would not see anything, until the universe was cold enough to allow light to pass through, that is the cosmic microwave background (it is in microwave radiation due to the extreme Doppler shift).

These articles provide the basic ideas:

https://www.scientificamerican.com/article/what-is-the-cosmic-microw/

https://www.popularmechanics.com/space/deep-space/a9632/how-close-to-the-big-bang-can-we-see-16105099/