Frequency Asked Questions

These are some of the first questions you may have when reading Fixing Hubble's Law.

Isn't the expansion of the universe a fact?

Not exactly. The redshifts are an observed fact. The redshifts may be interpreted as motion, which leads to the expansion of the universe as a hypothetical consequence. If every galaxy is moving away from our galaxy, that would put our galaxy in some special spot in the universe. But if every galaxy is moving away from every galaxy, we would be in a normal galaxy in an expanding universe.

The theoretical expansion of the universe has hypothetical consequences of its own: a small, young universe dominated by dark energy, dark matter.

Edwin Hubble never accepted the expanding theory as a fact. He wrote:

The familiar interpretation of red-shifts as velocity-shifts very seriously restricts not only the time scale, the age of the universe, but the spatial dimensions as well. On the other hand, the alternative possible interpretation, that red-shifts are not velocity-shifts, avoids both difficulties, and presents the observable region as an insignificant sample of a universe that extends indefinitely in space and in time.

E. Hubble, The Observational Approach to Cosmology, pg. 47, 1937 (emphasis added)

Much has changed since his day though. From the 30's through the 60's, the universe was thought to have begun as a point that grew out consistently.

But in the 1970's problems began to emerge. To make a software analogy, there were a lot of bugs that needed patching. Such as:

These problems lead to the theory of inflation. The universe blows up super fast in the first nanosecond after the big bang, then chills out. Then in 1998, it was discovered that the expansion of the universe is accelerating.

Today, the expanding theory of the universe looks like this:

If the benefit of interpreting redshifts as motion is that it doesn't require any new physics, then the expanding theory gave that benefit away decades ago.

To make the problem worse, as we peer into the "early universe", we don't see only young galaxies. We see mature systems like the ones around us.

For these reasons and others, the widely accepted expansion theory is increasingly being compared to outdated software: burdened by outlandish patches and still full of bugs. Here's a sample:

In any case, the redshifts of distant galaxies are observed facts. The motion of those galaxies and the expansion of space are theoretical interpretations of the facts.

Doesn't the Cosmic Microwave Background confirm an expanding universe?

The expanding universe theory predicts we observe the same background temperature in all directions.

This prediction seemed to hold until 2003 when anomalies appeared, which were confirmed in 2013:

Two Cosmic Microwave Background anomalous features hinted at by Planck's predecessor, NASA's Wilkinson Microwave Anisotropy Probe (WMAP), are confirmed in the new high precision data from Planck. One is an asymmetry in the average temperatures on opposite hemispheres of the sky (indicated by the curved line), with slightly higher average temperatures in the southern ecliptic hemisphere and slightly lower average temperatures in the northern ecliptic hemisphere. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look. There is also a cold spot that extends over a patch of sky that is much larger than expected (circled). In this image the anomalous regions have been enhanced with red and blue shading to make them more clearly visible.

This raises the question of where the CMB Cold Spot might appear to other observers.

For instance, imagine observers at the north and south poles of our observable universe:

We see a cold spot to the south. Does the south observer see a cold spot to their south? Does the north observer see the same CMB anomalies as we do?

This is a question the expanding universe theory doesn't have a clear answer for.

However, if the observable region is, as Hubble puts it, "an insignificant sample of a universe that extends indefinitely in space and in time", then there are no anomalies or questions. The cold spot is to our south, but to the southern observer the cold spot is in their vicinity.

One thing to keep in mind is that before the expanding theory even existed, Arthur Eddington calculated the temperature of starlight in our galaxy to be 3.18 Kelvin. As such, the CMB may just be photons limping in from galaxies 14 billion light years away, right before the temperature of space takes over our measurements.

Doesn't this conflict with special relativity?

Yes. The hypothesis is that the speed of light decreases with distance from the source, which is noticeable after traveling millions of years.

Special relativity tells us that light travels at c over all distances, even after millions and billions of years.

But our experiments don't last millions of years. In our experiments, H × D is so small, it can be considered zero.

So if:

    v_light = c / (1 + H × D)
    H × D = 0
    v_light = c / (1 + 0)
    v_light = c

In which case there shouldn't be any conflict with special relativity in the domain where the redshifts don't appear.

Doesn't this violate the Conservation of Energy?

In the specific model demonstrated here, yes, energy is lost. It could be that the energy deducted from the photon is deposited in space as it travels.

But I will let the esteemed Sean Carroll do the talking on this one.

The thing about photons is that they redshift, losing energy as space expands. If we keep track of a certain fixed number of photons, the number stays constant while the energy per photon decreases, so the total energy decreases. A decrease in energy is just as much a “violation of energy conservation” as an increase in energy, but it doesn’t seem to bother people as much. At the end of the day it doesn’t matter how bothersome it is, of course — it’s a crystal-clear prediction of general relativity.

In an expanding universe, photons redshift and energy is lost.

Under the literal interpretation of redshifts, however, energy could be lost, or it could be deposited throughout space. The photon could simply decay into tiny particles left in its path after 14 billion years.