When did the first stars form?
When did the first photons form?
The very first photons are theorized to form at the very first few seconds of the universe where stars started to form some billion years later. It really depends on what you're talking about. Some stars are older than photons and some photons are older than stars because they can both be created.
I was just reading genesis in the bible for literary reasons and it seems to state that a God created light first then the stars. However, it also suggests that the "formless" earth was created before light...
I just wondered about the science on this issue compared to the literal interpretation of genesis :)
Bet you weren't expecting that.
Photons are a curious beast.
Some might suggest that photons are required for "matter", as we know it, to exist.
pallidin can you elaborate?
Not very qualified, but my understanding is that photons are "force-carriers" , thus an assumption that certain forms of matter can not exist without photon exchange.
Very weak on this subject... could be totally wrong.
Yeah, but it's not just photons. To have matter as we know it, you must have vacuum as we know it, and that means all the fields it consists of. That's including, but not limited to, electromagnetic field, which gives rise to photons. (Or vice versa, it doesn't really matter.)
But when I for instance press my finger towards a table, the forces between my fingertip and the table arise through exchange of photons between the table and my fingertips, right?
And this is all relative to who's reference frame .
My professor even told me they're called "virtual photons". Oh jeesh there's such a big field out there I simply know nothing of (haha, quite literally)... exciting :)
As soon as you have hot electrons and baryons, you have bremsstrahlung (a source of photons). Thus photons will exist before the formation of the first hydrogen atom (which would require the emission of characteristic x-rays (another source of photons). As soon as a neutron is captured by a proton, a 2.2-MeV gamma ray is emitted (another source of photons). So before stars are created, photons are created.
[added] If particle energies are high enough to create pions (early universe), then the pi-zero decay will produce two ~67.5-MeV pions (in the center of mass rest frame).
Indeed. The word "virtual" implies that they are not directly detectable. Only their interaction with other stuff can be measured. (Of course, technically, anything you measure is through "interaction with other stuff"...) They have a lot of very weird properties. Virtual photons can have rest mass, for example. Worse, it can be negative.
(Answer to vitaminz) If you read Genesis carefully, ch 1 and 2, you will see two completely different (even opposite) accounts of the start of things. So don't believe a word of it in the literal sense.
I prefer the John 1:1 version.
IN PRINCIPIO ERAT VERBVM ET VERBVM ERAT APVD DEVM ET DEVS ERAT VERBVM
Which I choose to read as saying that information is all that ever was, is, or will be.
The Cosmic Microwave Background are photons older than any stars, that are still being detected today.
Any older than that were repeatedly absorbed and new ones emitted, as the universe was opaque.
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