The Death of a Thousand Cuts: How Neutron Star Mergers Shattered Young Earth Creationists “Light Time Problem”

For decades, the "Distant Starlight Problem" has been the Achilles' heel of Young Earth Creationism (YEC). The logic is simple: if the universe is only 6,000 years old, how can we see galaxies millions of light-years away? If light travels at a constant speed, those photons should still be in transit, leaving our night sky dark.

To bridge this gap, YEC proponents have historically relied on three primary theoretical "escape hatches": 

• c-decay (the speed of light was much faster in the past).

• Anisotropic Synchrony Convention (light travels instantaneously toward the observer but slowly away), and

• Gravitational Time Dilation (time moved faster in deep space than on Earth during creation week).

However, the 2017 detection of the neutron star merger GW170817 provided a multi-messenger "smoking gun" that effectively closed these loopholes.

The Event: GW170817

In August 2017, the LIGO and Virgo detectors picked up gravitational waves ripples in the fabric of space-time from two neutron stars spiraling into one another. 

Just 1.7 seconds later, the Fermi Gamma-ray Space Telescope detected a burst of high-energy light from the exact same location. This event occurred in the galaxy NGC 4993, located approximately 130 million light-years away.

1. The Death of "c-decay"

One popular YEC theory suggests that the speed of light (c) was millions of times faster in the past, allowing light from distant stars to reach Earth in days. However, GW170817 proved that the speed of gravity and the speed of light are identical to within one part in a quadrillion.

For the "c-decay" model to work, both the speed of light and the speed of gravity would have to have decayed in perfect lockstep over millions of years. This presents a massive "fine-tuning" problem. If c were significantly different in the past, the fundamental physics of stars (governed by E=mc^2) would be radically altered. For example if light accelerated one million times then by E=MC^2 stars would emit a trillion times its energy (a million times a million equals a trillion) All stars would explode. 

The simultaneous arrival of gravity waves and light from 130 million years ago confirms that c has remained constant throughout the journey.

2. The Failure of Anisotropic Synchrony (ASC)

The ASC model, championed by creationist Jason Lisle, suggests that the "one-way" speed of light toward Earth is infinite. Under this view, we see things the moment they happen, regardless of distance.

However, GW170817 wasn't just a flash of light; it was a physical process with a "timer." The gravitational waves recorded the final 100 seconds of the stars' orbital decay. This decay is governed by General Relativity and the masses of the stars. If the light reached us "instantly" but the physics of the merger took millions of years to play out (as required by the distance), the synchronization between the gravitational signal and the electromagnetic signal would be impossible to maintain. The fact that the physical "countdown" of the merger (gravity) and the "flash" of the explosion (light) arrived together proves they traversed the 130-million-light-year distance at the same finite speed.

3. The Time Dilation Contradiction

Some YEC models use "cosmological relativity" to argue that billions of years passed in the distant universe while only 24 hours passed on Earth. GW170817 destroys this by acting as a "standard clock."

The frequency of the gravitational waves and the subsequent decay of the radioactive "kilonova" (the afterglow of the merger) followed the exact timing predicted by nuclear physics. If time were "dilated" or "stretched" by a factor of millions to fit 130 million years into a 6,000-year window, the light and gravity waves we observed would be extremely "redshifted" or slowed down. We would see the merger happening in ultra-slow motion. Instead, we saw it happen at the precise "real-time" speed dictated by the laws of physics.

Conclusion

The neutron star merger of 2017 did more than just confirm Einstein's theories; it acted as a cosmic yardstick that validated the history of the universe. By showing that light and gravity travel together at a constant speed, and that physical processes 130 million light-years away occur at the same rate as those on Earth, science has rendered the YEC "light-time" explanations mathematically and physically untenable. The universe we see is not an optical illusion or a high-speed projection; it is a vast, ancient reality.