Late Photons from the Early Universe?

In summary, scientists have observed spectra of radiation emitted by quasars dating back to 900 million years after the big bang. Further studies have also observed radiation from the earliest stages of reionization, dating 200 million years after the big bang. Researchers hope to learn more about the first bright stars that appeared 100 million years after the big bang through space telescopes. The concept of "distance" in an expanding universe is based on comoving observers, not absolute positions. Therefore, the photons from giant stars that stopped emitting new radiation long ago may not have overtaken the massive material in our present position due to their distance and the expansion of the universe.
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Benzij
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TL;DR Summary
In the expanding universe scientists observe photons radiated by early giant stars, from whose material remnants we and our instruments are now made of. How did we arrive here before those photons? Light is supposed to move faster than any material.
It has been reported [http://www.astro.yale.edu/larson/papers/SciAm04.pdf, https://www.scientificamerican.com/article/the-first-stars-in-the-un/] that scientists have observed spectra of radiation emitted by quasars that date from about 900 million years after the big bang.

Others have observed radiation from the earliest stages of reionization dating 200 million years after the big bang.

Researchers hope to learn more about the first bright stars that appeared perhaps 100 million years after the big bang, by means of space telescopes that might detect some of these ancient bodies.

All the massive materials that we and our instruments and telescopes are made of - including protons, that are known to be quite stable - were present in the small early universe (and probably in the very beginning immediately after the big bang). The metals we use were created from remnants of those giant stars that have undergone several stages of transformation since then.

The universe has expanded enormously since those early stars emitted their radiation. The protons that they were made of have moved a large distance from their original positions to where they are now, and in particular to our own present position here.

Those protons must have moved very fast, apparently faster than light, otherwise how would we be able to be here, waiting to receive photons arriving now, of electromagnetic radiation that was emitted by those giant stars at that early stage?

One might argue that those protons were 'taken for a ride' by the expanding universe; but then - why did the radiation photons stay behind, to arrive here long after the massive material that now forms our instruments?

If, as is commonly assumed, light is faster than any massive material, then those photons from giant stars that have stopped emitting new radiation long ago, should have overtaken in their movement all massive material that we and our instruments are now made of, and should no longer be observable by us here and now.

Please advise, how to reconcile my doubts on this matter.
 
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  • #2
Benzij said:
The universe has expanded enormously since those early stars emitted their radiation. The protons that they were made of have moved a large distance from their original positions

No, they haven't. The concept of "distance" you are implicitly using here does not work in an expanding universe; there is no way to mark "positions" as they would have been in the absence of expansion.

The concept of "distance" that cosmologists actually use is based on "comoving" observers--observers who always see the universe as homogeneous and isotropic. Each such observer marks a "position" that is considered to be unchanging as the universe expands and is used as a reference. We here on Earth are not exactly comoving observers, since we see a small anisotropy in, for example, the CMBR, but we are close to comoving. So it is a good approximation to imagine an exactly comoving observer in the vicinity of Earth who has been there all through the universe's expansion and who marks out a "position" that is unchanging.

Benzij said:
If, as is commonly assumed, light is faster than any massive material, then those photons from giant stars that have stopped emitting new radiation long ago, should have overtaken in their movement all massive material that we and our instruments are now made of

Not if the giant stars, when they emitted their radiation, were far enough away, in terms of the comoving observer at their position, from the comoving observer at the Earth's position. The radiation we are seeing now was emitted from places that were far enough away from Earth that, taking into account the expansion of the universe, that radiation is just arriving here now. Since, according to our best current model, the universe is and always has been spatially infinite, there were plenty of such places at the early times you mention.
 

1. What are late photons from the early universe?

Late photons from the early universe refer to photons (particles of light) that were produced in the early stages of the universe's evolution, but are only reaching us now due to the vast distances they have traveled. These photons carry valuable information about the early universe and its formation.

2. How are late photons from the early universe detected?

Scientists use specialized instruments, such as telescopes and detectors, to detect and measure the properties of these late photons. These instruments are designed to capture and analyze different wavelengths of light, including the microwave background radiation that is a remnant of the early universe.

3. What can we learn from studying late photons from the early universe?

By studying these late photons, scientists can gain insights into the conditions of the early universe, such as its temperature, density, and composition. This can help us better understand the processes that led to the formation of galaxies, stars, and planets, and ultimately, the origins of our own universe.

4. How do late photons from the early universe support the Big Bang theory?

The late photons from the early universe provide strong evidence for the Big Bang theory, which states that the universe began with a massive explosion and has been expanding ever since. The cosmic microwave background radiation, which is made up of these late photons, is a key piece of evidence for the Big Bang theory.

5. Are there any current research projects focused on studying late photons from the early universe?

Yes, there are several ongoing research projects, such as the Planck satellite mission and the Atacama Cosmology Telescope, that are dedicated to studying late photons from the early universe. These projects aim to further our understanding of the early universe and its evolution, and may even uncover new mysteries and insights about the origins of our universe.

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