It's not every day you wake up to find out
the universe is twice as old as it was the night before.
But a new paper by Rajendra Gupta at the University of Ottawa suggests
the universe is really 26.7 billion years
and not 13.8 billion years as we thought.
That's pretty remarkable because over the last 25 years,
we've developed a fairly robust model of the universe.
It explains everything from the cosmic microwave background
to the accelerating expansion due to dark energy.
In fact, I can remember when astronomers estimated the universe's age
at anywhere from 9 to 20 billion years.
So narrowing it down to 13.8
billion years was kind of a big deal.
But Gupta's paper was motivated by what he calls
the “Impossible Early Galaxy problem”.
It started when the James Webb
Space Telescope found galaxies that were surprisingly massive,
even though the universe was just 300 to 500 million years old at the time.
To the best of our understanding,
that's not nearly enough time for galaxies to have gotten so big.
And that probably means there's something wrong
with our understanding of how galaxies formed.
However, Gupta is taking a different approach and asks,
Well, what if the universe is really just older than we thought?
So the paper got a lot of press, which I guess
is understandable because it's good for the clerks.
But for all of the public attention, astronomers are skeptical.
And it's not because we are determined
to cling to our long held dogmatic beliefs about the universe.
Rather, the paper just doesn't seem to match up with the observations.
So today we're going to take a look at our current understanding of the universe,
and then we'll talk about this new model for its age.
Our best understanding of how the universe works is called “Lambda-CDM”.
“Lambda” refers to the Cosmological Constant
that's been driving and accelerating the expansion ever since the Big Bang.
That expansion causes galaxies to move away from us faster
with increasing distance.
The faster the galaxy is carried away from us,
the more its light is stretched to longer and therefore redder wavelengths.
We call this effect Cosmological Redshift.
“CDM” refers to Cold Dark Matter.
It's “cold” in the sense that it's moving slow enough to clump together,
and that allows it to attract normal matter to form the stars,
galaxies, and the large scale structure we see today.
Lambda-CDM tells us the universe is made of 5% normal matter
(that makes up the stuff we see), 27% dark
matter, and 68% dark energy.
It also tells us that the universe is 13.8 billion years old.
It's a good model. In fact, it's our best model.
But we also know it's incomplete.
For example, Lambda-CDM predicts the universe should have something like 3
to 4 times more lithium than it does, Dark
matter doesn't explain all of the gravitational interactions
we observe and the age as measured from distance measurements
to the furthest galaxies, converges on an age of 13.3 billion years.
Instead of 13.8 billion years.
At first, it was assumed that the two methods would be reconciled
with better data. But as measurements improved
the discrepancy has only become more apparent.
This problem is called the “Hubble Tension” or the “Crisis in Cosmology”,
and I should really save that for another video.
But the short version is that our measurements to distant
galaxies are based off of distance measurements to nearby galaxies.
It's thought that those nearby measurements are probably
being thrown off by dust in the Milky Way and in the galaxies themselves.
If that's true, then JWST should be able to see
through the dust and improve those measurements.
And hopefully that will bring the age
of the universe as measured from galaxies back in line
with the age as measured from the cosmic microwave background.
We'll see.
But until then, we take the 13.8 billion year age as the canonical age
of the universe because it's measured against the cosmic microwave background
and microwave radiation is even less disturbed by dust.
So from CMB measurements, we get things like the expansion
rate of the universe and the overall density of the universe.
You can then use these values to work out for how long light with a given
redshift must have been traveling through the universe to reach us.
And from there, determine
how old the universe was when we are looking at a given object.
For example, a galaxy with a redshift of ten
means we're seeing at 13.3 billion years ago.
That means we're seeing the galaxy
when the universe was just 500 million years old.
But this particular galaxy appears to be too massive for a 500 million year old.
To give the galaxy more time to come together, Gupta introduces
a version of Lambda CDM that includes some critical modifications.
The first modification is an idea called “Tired Light”.
It was proposed by Fritz Zwicky back in 1929 as a reaction to Edwin
Hubble's discovery that galaxies’ redshifts increased with their distance.
Today, we understand this as the discovery of the expanding universe,
which led to the Big Bang model, which led to the discovery of dark energy
which led to Lambda-CDM that we know and love today.
But at the time it contradicted the widely held
belief that the universe was static and eternal.
In order to maintain a steady-state universe, Zwicky suggested that as light
travels through space, it scatters off particles along the way and loses energy.
That energy loss causes the light to stretch out to longer wavelengths.
So the light we detect is redshifted because it was “tired” from the journey.
It was an interesting idea, but it was quickly abandoned for a couple of reasons.
Zwicky himself understood this kind of scattering would cause
the photons to kind of spread out and blur the images of distant galaxies.
Not only was no such
blurring detected in Zwicky time, but modern deep images reveal
distant galaxies that are just as well focused as their nearby counterparts.
Tired Light also predicts that if the universe is static,
then the amount of light coming off a galaxy’s surface
should be the same no matter its distance.
The idea is that if the galaxy is further away,
the less light we're going to receive from it due to its distance.
But its angular size is smaller as well, so the amount of light
coming off a unit angular surface area should be the same.
But that's not what we detect either.
When we look at the most distant galaxies, the amount of light per unit surface
area is much less than for nearby galaxies.
Another problem is that tired light doesn't account for cosmological time
dilation. This is a really cool effect
that can only happen if the universe is expanding.
The more redshifted a galaxy's light is,
the more time it takes for the same number of emitted waves to be received.
So a photon at redshift of one would be twice its rest wavelength.
But because the waves are twice as long they arrive half
as frequently than they would if they were coming from a source at rest.
So we have to wait twice as long to receive the same number of waves.
Meanwhile, the source of that light is moving away from us,
so the time required to receive that light gets longer and longer.
As a practical matter, events coming from high redshift sources
seem to take longer to transpire.
This effect was demonstrated with highly redshifted supernovae
that take longer to fade out than those nearby galaxies.
On the other hand, in a static universe with tired light,
distant supernovae would appear more red than their nearby counterparts,
but they'd still take the same amount of time to fade.
Cosmological time dilation was recently demonstrated
with high redshift quasars that appear to vary their light output
at slower rates as compared to quasars at lower redshift.
In fact, astronomers who study quasars must apply corrections
for cosmological time dilation, or else their measurements would be thrown off.
Finally, tired light doesn't explain the cosmic microwave background.
The CMB redshift is a whopping 1,089.
According to Lambda-CDM, it originated just 380,000 years after the Big Bang.
Tired Light says that the CMB radiation will lose energy
and increase its overall wavelength as it travels, so it's Blackbody
curve would shift from the blue line to the red line.
But Lambda-CDM says that because the universe is expanding,
not only does its light lose energy, but the intensity of that light
should diminish as well as represented by the black line.
That's exactly what was measured by the Koby mission in the early 1990s.
In fact, the cosmic microwave background
is the most perfect blackbody spectrum ever measured.
Now, Gupta is not suggesting replacing Lambda CDM
with a steady state universe and tired light.
Rather, he's combining the two ideas together
to create lambda CD4+ t cell.
But in order to do so, he invokes a second modification that states the fundamental
constants of nature aren't constant at all, but rather varied over time.
And that means things like the speed of light, Planck's constant,
and the gravitational constant were different in the past than they are today.
However, atomic transitions are governed by two of the fundamental constants,
so if one of them were to change or if they both changed at different times,
then the spectra from high redshift quasars would be unrecognizable.
To address that problem, Gupta invokes a mechanism where
all of the constants change together so the atomic transitions
and spectral lines still work correctly across all redshifts.
He calls this idea “Covarying Coupling Constants”.
The good news is
that when these modifications are added to Lambda-CDM, it actually fits
some of the data even better than Lambda-CDM does on its own. But
the bad news is that no laboratory test has ever confirmed that constants vary.
On the one hand, yes, it's kind of hard
to wait billions of years for a lab experiment to finish,
but we don't need to wait a billion years because we can
look at the products of radioactive decay here on Earth.
Decay isotopes have been accumulating since Earth formed four
and a half billion years ago.
The rate of decay is governed by the fine structure constant,
which in turn depends on the electron charge.
The speed of light and Planck's constant in order
to produce the abundance of decay isotopes we have today.
This constant couldn't have changed by more than 0.3
part intended the 16 per year.
That's billions of times smaller
than what Gupta's variable constant explanation would require.
If the universe were really twice as old as we thought,
then there should be stars around today much older than 14 billion years.
Our Galaxy is surrounded by a halo of globular clusters.
The biggest stars to form in those clusters evolved and went supernova
long ago.
But their smaller, less massive, members still remain to this day.
Among them are M-type red dwarfs, which should live for up to trillions of years.
But when we look at for the oldest stars and globular clusters, we find that
they're around 13 billion years at most.
There was one star dubbed “Methuselah” that got some press many years ago
because its age was initially estimated
at 14.46 plus or minus 0.8 billion years.
The error bars alone allow the star to still exist
in a 13.8 billion year old universe.
But since then, our understanding of stellar evolution has improved,
and that ended up revising Methuselah’s age downward to 12
plus or minus 0.05 billion years.
If the universe was 26 billion years old, there would be clusters
of very old K and M-type stars still hanging around our galaxy.
But so far, no infrared surveys have found any.
Still, Gupta's theory was put forward
to address the Early Galaxy problem.
But what if the early galaxy problem really isn't a problem at all?
The galaxies are thought to be massive because they'd have to be
very luminous in order to be seen at such high redshift.
So the reasoning is that if these galaxies are as bright
as they appear to be at high Redshift.
They must have already had a lot more stars in them
than we thought was possible by that time.
But the only galaxies whose stellar distributions
we can reasonably measure are the Milky Way and nearby galaxies’.
When we look at a distant blob,
we don't resolve any individual stellar populations.
So we need to assume that it has
the same distribution of stars that galaxies have today.
And that's not a safe assumption for early galaxies.
The universe was a lot more dense back then
and almost entirely made of hydrogen and helium.
So very massive luminous stars would have been able to form
a relatively modest amount of massive superstars
would make the Galaxy a lot brighter while still having an overall low mass.
Something else to consider is that the galaxies we found
so far are probably the brightest in the early universe.
If that's the case, then chances are most of the early
galaxies are still too faint to have been detected yet,
and that would mean they are less massive as well.
That's why there's a JWST program to make ultra-deep images of the universe
to tease out the earliest and faintest galaxies.
And that will give us a much better idea of what the early universe
was really like.
And then there's the possibility that the reported redshift of these
early galaxies may not be very accurate to begin with.
The galaxies were detected by imaging with different filters.
The redder the galaxy gets, the longer the wavelength filters they show up in.
But you're also making an assumption that the galaxy appears
so red due to Redshift and not because it's heavily laden with dust.
Even if you can rule out dust, the filters allow a range of wavelengths
to pass through.
so your estimate of the redshift is going to be uncertain.
The most robust method is to take the spectrum of the galaxy
and use well-known breakpoints to pinpoint the exact redshift.
A recent example was of a galaxy in the CEERS survey
that initially seemed to have a redshift of 16.4.
But after its spectra was analyzed, it turned out to be only 4.9.
You might wonder then, ‘Well, why bother with this
imaging approach at all if it's going to give us wrong answers?
Why don't we just take the spectra to begin with and be done with it?’
Well, the answer is simple.
You need the imaging to figure out which galaxies to take a spectrum of.
I suspect that as we gain more spectra of these early galaxies,
we're probably going to find out that, yes, they're young,
but just not as young as previously thought.
None of these resolutions to the impossible galaxy problem
would require any modifications to Lambda CDM
And that's why it's risky to take galaxies whose situation we don't yet
fully understand
and extrapolate from there to require a fundamental change in our cosmology.
Still, there is no reward without risk,
and I don't think anybody is faulting Gupta for publishing his paper.
He does a full breakdown of his theory and doesn't seem to be resorting
to any hand-waving.
However, one theoretical study
isn't going to overturn decades of work that led to our current model.
But then again, JWST’s Mission is still in its early days.
How cool would it be if we discover something about the universe
as revolutionary as dark energy or cosmological redshift?
Let's see what happens.
A huge thanks to my Patreon supporters for helping to keep Launch Pad
Astronomy going, and I'd like to thank Paul Miller
and Ethan Staghorn for becoming my newest supporters.
Until next time, stay curious, my friend.