- 4103 - UNIVERSE - how old is it, really? Well, it depends on the speed of light? The Universe could be twice as old if light is “tired” and physical constants change. When the James Webb Space Telescope started collecting data, it gave us an unprecedented view of the distant cosmos. Faint, redshifted galaxies seen by Hubble as mere smudges of light were revealed as objects of structure and form.
----------------------- 4103 - UNIVERSE - how old is it, really?
- Then, astronomers were faced with a bit of a
problem. Those earliest galaxies seemed too developed and too large to have
formed within the accepted timeline of the universe. This triggered a flurry of
articles claiming boldly that JWST had disproven the big bang.
-
- The problem isn’t that
galaxies are too developed, but rather that the universe is twice as old as
we’ve thought. A whopping 26.7 billion years old. It’s a bold claim, but does
the data really support it?
-
- In the “tired light
model”, light spontaneously loses energy over time. So as photons travel
billions of light years through the cosmos, they become redshifted. Thus, the
light of distant galaxies is redshifted not because of cosmic expansion, but
because of the inherent reddening of light over time.
-
- The idea of tired light
has been around since Edwin Hubble first observed cosmic expansion as a way to
maintain the idea of a steady-state universe. It lost popularity as the
evidence for cosmic expansion became clear, and regained some popularity as the
Webb observations started rolling in.
-
- Quantities such as the
speed of light, the charge of an electron, or the gravitational constant seem
to be built into the structure of the universe. They have the values they do
because of the way the universe formed, and it’s generally assumed they don’t
change over time. We have geological and astronomical observations that show
physical constants haven’t changed for at least several few billion years.
-
- If you combine “tired
light” and changing physical constants, you can get a universe that appears
younger than it actually is. Basically, tired light gives you the cosmological
redshift you observe, and gradually shifting physical constants means those
mature distant galaxies aren’t just 100 million years old, they are billions of
years old. By tweaking tired light and variable physical constants just so to
match the data, you get a universe that is 26.7 billion years old.
-
- There are two problems
with this theory. The first is that tweak theories are weak theories. While
this model can be made to fit observational data, there’s no physical
motivation for doing it. There are lots of models that can be tweaked to fit
data, which is not the same as having a robust physical model.
-
- The second problem is
that JWST’s observations don’t rule out the standard 13.7 billion-year-old
universe. The galaxies are more complex than some computer simulations have
predicted, but that’s not surprising given the limits of large structure
models. There are plenty of ways early galaxies could have evolved quickly that
don’t require rewriting cosmology.
-
- This is the kind of
paper that thinks outside the box, which is a great way to make sure we aren’t
locked into old models just because they’ve worked so far. It isn’t likely that
this new model overturns standard cosmology, but as long as ideas are testable
and disprovable, as this model is, there is no harm in adding it to the pile of
ideas.
-
-
July 24, 2023 UNIVERSE
- how old is it, really? 4103
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Monday, July 24, 2023
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