Bigbang and its light coming to us

  • Thread starter Thread starter shabeer_quark
  • Start date Start date
  • Tags Tags
    Bigbang Light
AI Thread Summary
The discussion clarifies that the Big Bang refers to a state of the universe rather than a specific location, emphasizing that the universe was once a hot, dense gas that has since expanded and cooled. As the universe cooled, it became transparent, allowing light emitted around 380,000 years post-Big Bang to travel freely through space. This ancient light, which originated from a uniform hot gas, is still detectable today, streaming towards Earth from all directions. The Milky Way galaxy, along with other cosmic structures, formed from this expanding gas, which continues to disperse. Thus, the light observed from telescopes carries signatures from the Big Bang, providing insights into the universe's origins.
shabeer_quark
Messages
2
Reaction score
0
we are living in this milky way galaxy which got separated from bigbang ,the separation would not have taken place in light speed but how come we are tracking the light that is emitted from bigbang period from our earth
 
Astronomy news on Phys.org
shabeer_quark said:
we are living in this milky way galaxy which got separated from bigbang ,the separation would not have taken place in light speed but how come we are tracking the light that is emitted from bigbang period from our earth

This is a very good question... and finding the answer to it basically marks the point when I at last understood what the big bang really means.

The "Big Bang" refers to a time, not a place. Our universe used to be very hot and dense. Everything was jammed up together, a very thick extremely hot ionized gas. Furthermore, everything was flying apart from everything else... and it still is.

This was not an explosion at some point in space; it was a general state of affairs, through all the universe... at least, all the regions that we have any hope of measuring or observing.

As this hot dense gas disperses, it cools and becomes less dense. The word "cooling" here is fun, because we are talking (at first) about dropping from trillions of degrees, to billions of degrees, to millions of degrees. But after some 380,000 years, it has cooled down to about 3000 degrees. At this point, atoms can start to hold onto electrons, and the material in the universe becomes transparent. Before this, light didn't get very far, because a hot plasma is opaque. But when the matter in the universe is cool enough to be transparent, light just carries on through the expanding gas without stopping.

The key point... we are still talking about a hot expanding gas involving the whole universe... at least, everything we can hope to see or measure.

Since then, the gas has continued to expand, and cool. It pulled together into stars and galaxies... including our own Milky Way. And all this time, light continues to stream through the universe. The oldest light is the light that was emitted 380,000 years after things kicked off (somehow)... and that light is everywhere, moving in all directions... because the gas which emitted it was also everywhere and in every direction.

And now, 13.7 billion years later or so (current best estimate) that light is STILL going. We see it coming to us from every direction in the sky, because everything all around us, as far as we can see, is material that started out, along with us, in that hot dense soup of matter and energy that has since expanded and cooled to form the universe as we see it now.

Cheers -- sylas

PS. A history of events for the "observable universe"... that is, everything we can see or measure, including the oldest light still around, is described nicely at Brief History of the Universe, courtesy of Ned Wright at UCLA.
 
Salam alaikum sylas

Great explanation indeed from great mind. will read history of time surely i was half way through. That means whatever light rays we see in telescope from Earth should have the signature of origin of bigbang .
 
Is a homemade radio telescope realistic? There seems to be a confluence of multiple technologies that makes the situation better than when I was a wee lad: software-defined radio (SDR), the easy availability of satellite dishes, surveillance drives, and fast CPUs. Let's take a step back - it is trivial to see the sun in radio. An old analog TV, a set of "rabbit ears" antenna, and you're good to go. Point the antenna at the sun (i.e. the ears are perpendicular to it) and there is...
3I/ATLAS, also known as C/2025 N1 (ATLAS) and formerly designated as A11pl3Z, is an iinterstellar comet. It was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) station at Río Hurtado, Chile on 1 July 2025. Note: it was mentioned (as A11pl3Z) by DaveE in a new member's introductory thread. https://www.physicsforums.com/threads/brian-cox-lead-me-here.1081670/post-7274146 https://earthsky.org/space/new-interstellar-object-candidate-heading-toward-the-sun-a11pl3z/ One...
Back
Top