Category: cosmology

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The Sagan Paradox, Chapter 1: The Golden Record

Introduction and Carl Sagan’s Early Work

Artwork inspired by Linda Salzman Sagan’s design for the Pioneer plaque, commissioned by NASA: click here view the original design

Carl Sagan (1934–1996) was an American astronomer, astrobiologist, and author. After NASA was founded in 1958, Sagan became a consultant for the agency. His first job involved planning the explosion of an atomic bomb on the moon, the A119 project. Highly controversial, to say the least. In 1961, at the age of 27, he published a study on the atmosphere of Venus. In 1970 he researched the conditions that could lead to the emergence of life in the cosmos on distant planets. To achieve this, he exposed frequently occurring elements to the UV radiation of a young sun and observed how amino acids, the building blocks of life, were formed from them. Carl Sagan became a full professor at the astronomy department at Cornell University. Around this time, talk shows began inviting him as a popular guest to discuss the possibility of extraterrestrial life.

Reference: Carl Sagan, Long wavelength ultraviolet photoproduction of amino acids on the primitive Earth

“Hello, Aliens!”: Voyager Probes Get Sagan’s First Broadcast

In 1972 and 1977, Carl Sagan sent the first messages to extraterrestrials into space on the panels of the space probes Pioneer 10 & 11 and the Golden Record of Voyager 1 & 2.

The gold-plated aluminum cover (L) of the Voyager golden record (R) both protects it from micrometeorite bombardment and also provides a key to playing it and deciphering Earth’s location. NASA

It contains greetings and wishes for peace from the people of Earth in 55 languages. Earthlings extend their friendship, wish happiness and health, and express hope to one day meet their cosmic neighbors. They also express the desire for goodwill and harmony among all beings in the universe.

Reference: Golden Record Greetings – NASA Science
Each of the Voyager spacecraft, launched in 1977, carried a golden phonograph record. One of its purposes was to send a message to extraterrestrials who might find the spacecraft as it journeyed through interstellar space.

The greetings are in alphabetical order, from Akkadian (an extinct language for over 2000 years) to Wu Chinese. The inclusion of Akkadian in this earthly record is pretty strange. One day, these transmissions might be intercepted as they pass through space by an alien culture.

Voyager’s ‘Cosmic Map’ Of Earth’s Location Is Hopelessly Wrong

With the help of the included pulsar map, these aliens could potentially find Earth. Pulsars are stars that rhythmically emit radiation, like interstellar lighthouses. We can use them as a cosmic GPS.

Pulsar GPS: Sagan’s Star-Beacon Timecode Reveals 1971 Earth

Over long periods of time, the frequency of a pulsar slows down. Thus the pulsar map designed by scientist Frank Drake and graphic artist Linda Salzman Sagan is not only a determination of the position of our Earth in space, but the map also precisely pinpoints the position of Earth in time: 1971.

What if a prospective alien civilization has or develops the ability to time travel? What would they do with the information provided by our space probes?

Speculation about the subject makes for the greatest sci-fi story ever told. This is particularly true when we consider the included Mesopotamian-language greeting and the Annunaki creation myths—some of which have been popularized by Zecharia Sitchin and others.

Of course, intercepting our space probes is extremely unlikely. It could take millions of years, if at all. But then again, the life expectancy of the Golden Records is 5 billion years.

Aliens recovering the Golden Record
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Posing the Cosmic Question: What Occurs Within a Black Hole?

AI’s Provocative Claim: “Humans Are Ignorant”

Consider the following intriguing questions: What happens to the very dimensions of spacetime inside a black hole? Different responses from an AI highlight both our current understanding—and our limitations.

Pablo Carlos Budassi, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

First Perspective: Continuity of Four-Dimensional Spacetime

One reply asserts that objects falling into a black hole do not lose any dimensions. In this view, spacetime retains its four-dimensional structure (three dimensions of space plus one of time) both outside and inside the event horizon. The singularity—where density becomes infinite—is not actually a state reduced to 1D. Instead, it represents a point where general relativity breaks down after entering a black hole. Although quantum gravity theories such as loop quantum gravity propose alternatives (for instance, “bounces” that avoid the singular state), none of these ideas involve a reduction in the number of dimensions.

Second Perspective: Dimensional Breakdown at the Singularity

A subsequent response from the same AI emphasizes a different perspective. In Einstein’s theory, the singularity is defined as a point of infinite density and extreme spacetime curvature. It is where the equations of general relativity “break down.” In this classical picture, spacetime loses its well-defined four-dimensional structure (3 spatial dimensions plus 1 time dimension). For non-rotating, or Schwarzschild, black holes, the singularity is described as a 0D point. In contrast, for rotating (Kerr) black holes, the singularity takes on the form of a 1D ring.

Urbane Legend, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/, via Wikimedia Commons

Reconciling the Contradiction: Artifacts of Mathematical Models

The AI explains these seemingly contradictory responses with a reminder that, in general relativity, the singularity is not a physical object. Instead, it is a mathematical artifact. The labels “0D” and “1D” serve as geometric shorthand—conceptual placeholders that indicate where our classical theories fail. In effect, these designations (“here be dragons”) acknowledge the limits of our current understanding of extreme gravitational environments, especially those involving black holes.

Embracing the Unknown in Theoretical Physics

In summary, one perspective maintains that spacetime remains four-dimensional throughout the journey into a black hole. This is true even as general relativity breaks down at the singularity. Another viewpoint suggests that, near the singularity, the familiar four-dimensional framework is lost. It collapses into a 0D point or a 1D ring depending on the black hole’s rotation. Ultimately, both answers are reminders of the limits of our current theories and the continuing challenge of unifying general relativity with quantum mechanics.

Stephen Hawking’s Insight: Illuminating Our Limitations

An illustrative image from Stephen Hawking’s Reith Lecture on 26 January 2016 further underscores this point. Hawking’s insights remind us that while our current models of black holes capture many aspects of reality, they also expose profound gaps in our knowledge.

Until a successful theory of quantum gravity is developed, these descriptions remain approximations. They reflect human ignorance as much as our understanding.

Image: from Stephen Hawking Reith lecture, 26 January 2016