The starlight “problem”
Young Earth Creationist (YEC) claim the universe is 6,000 (or 10,000) years old. If it’s really that young, how can we see stars 30,000 (and more, much more) light years away?
Some, like Russell Humphreys, think General Relativity (GR) can help.
How General Relativity works: The Interstellar movie
In the movie Interstellar, Matthew McConaughey misses the teen years of his daughter Murphy for having spent too much time on a planet too close to the “Gargantua” Black Hole. One single hour on “Miller’s planet” is 7 years on Earth! Gargantua weights about 100 million times more than the sun, and yes, according to General Relativity (GR), a planet orbiting it like “Miller’s planet”, would enjoy such a crazy time contraction.
According to his own wristwatch, Matthew McConaughey spends a little more than 3 hours on this planet. When he comes back to his mother ship, he finds he’s been away for 23 years. His daughter Murphy was about 10 when he left. She’s now 30 something.
How does it work?
The gravity of the Black Hole (BH) increases as you get closer to it. As long as gravity is not too strong, one may define a so-called gravitational potential, which goes down and down as you approach Gargantua, like in the figure below (absolutely not to scale).
What GR tells you is that time goes slower in the potential well . The deeper you’re in the well, the slower time passes with respect to Earth. Until you get to the “Event Horizon”.
What happens past then? If you were to fly to the Event Horizon, an observer from Earth would see you approaching it closer and closer, without never crossing it. As for you in your spaceship, you would definitely cross the Event Horizon. Passed this point, it would be impossible to turn back. You would inevitably crash at the center in a time that can be calculated .
Note that talking about a “gravitational potential” only makes sense while General Relativistic effects are small. It makes no sense at all below the Event Horizon.
In Interstellar, all this happens over a few billion kilometers. The Earth is far away from this all, completely out of the potential well of the black hole. And yes, according to Einstein’s General Relativity, you would get such a crazy time contraction of Miller’s planet.
In Interstellar, 1 hour on the planet becomes 7 years out there. And 6,000 years? What would they give out there? 0.36 billion years!
Could GR hold the key to thousands of years on earth being like billions in the rest of the universe?
Russell Humphreys’ cosmology
I refer to the cosmology described here.
Humphreys imagine the Earth is at the center of a huge expanding spherical shell with “waters above”. Using GR, he “derives” (why between quotes? See below) the gravitational potential inside the sphere. As you can see on the figure below, the sphere is huge . The Earth is somewhere inside.
The gravitational potential goes down as one approaches the sphere. It is constant inside. So a clock in the inside, where the Earth is, will tick slower than a clock outside. Like in Interstellar, clocks tick slower as you go down the gravitational potential.
From there Humphreys argues that if “during the fourth day, God creates star masses” so as to lower even more the flat potential inside the sphere, around the Earth, time there would have stopped. It’s even better than Miller’s planet…
Let’s now see the problems.
It just turns out that 1) observations do not back up the existence of Humphreys’ spherical shell and 2) Humphreys’ claims about what would happen if the inside gravitational potential were lowered beyond a “critical potential” (see his figure 7), is wrong according to GR.
What observations tell about the spherical shell
To start with, Humphreys’ solution of GR equations (his equation 2) is not “new”, as he claims. This is just the solution Karl Schwarzschild found in 1916. And it cannot be otherwise. Why? Because there is only one solution to GR equations with spherical symmetry  and it is Schwarzschild’s solution (if there’s but one solution and you find one, then this must be the one). So Humphreys’ solution cannot be “new”.
- The waters above the spherical shell cannot be liquid. Why? Because nothing sits on top. So it is under 0 pressure. And under 0 pressure, water cannot be liquid. It is either solid ice, or vapor.
- What about the shell itself? The universe is expanding, and it seems Humphreys admits this (even though his universe is not expanding. See last point.). So let’s play backward the movie of the universe. The spherical shell and the universe contract. They get hotter and hotter. Regardless of what it is made of (what is it made of?), the hotter and hotter spherical shell vaporizes. Its molecules are broken, as are those of the universe inside. Then the atoms that made this all are also broken into electrons, protons, and neutrons. Then protons and neutrons are broken into quarks .
Let’s now play the movie forward from this quark epoch (we don’t really know what came before because we don’t know the laws that applied then). The universe cools down and these quarks assemble to make protons and neutrons. These protons and neutrons assemble to make atoms . The universe keeps expanding, hence cooling down, and these atoms can combine to make molecules. Question: at one point does the spherical shell forms? At the beginning of our movie, it wasn’t there. So when and how did it form? No natural phenomenon is going to make a spherical shell of “something” with “waters above”. And if it was supernaturally there from the start, why going to such great length to come up with a pseudo-natural scenario “explaining” the starlight problem?
- According to GR, the interior of the spherical shell is “flat”. It’s good old space time. The problem is that such a space time does not expand . That’s what GR dictates. Even if the spherical shell does, the interior does not, and Humphreys equations 2 & 3 are OK with that. Two inside points 1 million light years from each other will still be so 1 billion years later
This is a problem because we observe the expansion. Stars recede from us. The farther, the faster. In Humphreys’ “cosmology”, there’s no redshift. In Humphreys’ “cosmology”, the temperature of the Cosmos Microwave Background doesn’t change with time. Yet, such a temperature change has been observed.
Humphreys’ GR below the “critical potential” is wrong
Looking at the math of how time passes slower inside the shell than outside, one notices that if the ratio R/M is large enough (R = radius of the shell, M = its mass), something strange happens to the math . If that happens, Humpreys writes that “physical clocks would stop completely. Time would no longer exist” and “light cannot propagate”!
Obviously, stopped clocks allow to squeeze anything you want in just no time.
The problem is that if R/M turned to be large enough, and contrary to what Humphreys claims, GR states that clocks inside the shell would not stop. And light would keep propagating.
These are very well-known results since the situation produced for R/M large enough is precisely the one produced inside the event horizon of a black hole. Admittedly, what happens there is quite weird and it took physicists decades to grasp it. Yet, however involved it may be, some things are sure: clocks keep ticking inside an event horizon, and light keeps propagating. A classical calculation of General Relativity even consists in computing the time it would take for an astronaut to reach the center of a Black Hole . Part of this time is definitely the one is takes to go from the event horizon to the center. According to GR, clocks do tick “inside”. Besides, light does propagate.
Let’s wrap it up. Humphreys’ cosmology fails at various stages. It assumes a huge spherical shell around us, that cannot have formed unless it got there miraculously. Then General Relativity inside this sphere gives a space time which is not expanding whereas observations do show it does. Finally, Humphreys has GR tell that in some special circumstances, time no longer stops inside the shell, and light cannot propagate, whereas GR doesn’t tell this at all .
This is clearly some conclusion-driven, bad, “science”. Humphreys comes up with an arbitrary scenario only designed to explain away the YEC starlight problem. Then it becomes bad science: the spherical shell invoked cannot have formed naturally, and its consequences do not match observations. And then it becomes bad GR: after having invoked GR to the rescue, Humphreys has GR predicts phenomena it doesn’t.
This is a good example of why “mainstream science” rejects “creacion science”. The reason why “mainstream science” rejects “creation science” has nothing to do with religion. Einstein talked about God, Abdus Salam was a devout Muslim, Ramanujan attributed his findings to a Hindu goddess. Many of my friends astrophysicists talk about God in the lab. I talk about God.
No, the real reason why creation science is rejected, is because it tramples logic, observations and experiments. It perfectly fits CS Lewis’ words ,
Science twisted in the interests of apologetics would be sin and folly
 See The Science of Interstellar by Nobel Prize Kip Thorne. The reader will also find more technical data on the same topic here.
 Such gravitational time shift has been checked experimentally many times and is now in use in your GPS.
 The falling time is computed in Gravitation, by Misner, Thorne, and Wheeler, page 820. It is finite for the astronaut, and infinite for the observer.
 Its size is a little less than the one of the observable universe, about 46 billion light years, see https://arxiv.org/abs/astro-ph/0310571
 That’s the Birkhoff’s theorem.
 All these states of matter have been studied in the lab. There’s no conjecture here. Matter does that when you heat it more and more.
 Using the known laws of physics, you can derive from this scenario the relative abundances of light elements and compare to observations. It was done from 1948 and works well. Others expected and observed consequences of the movie are the Cosmic Microwave Background or the Baryonic Acoustic Oscillations.
 The “Minkowski metric” describes the good old flat space time. If you want expansion you need something like the “Friedmann–Lemaître–Robertson–Walker metric”. See for example equation (28.9) page 1371 of Modern Classical Physics by Thorne and Blandford. Or simply Google “FLRW metric”.
By the way, George Lemaître was a priest.
 Technically, the coefficient of dt2 in Eq. (2) becomes negative.
 See note .
 Just check for example Figure 26.4 page 1269 of Modern Classical Physics by Thorne and Blandford. It shows how light does propagate within the Even Horizon.
 CS Lewis, God in the Dock: Essays on Theology and Ethics, Eerdmans Publishing Co, 1972, p. 93.