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StarTalk Radio

Cosmic Queries - Get Some Space

Published September 26, 2025
View Show Notes

About This Episode

Neil deGrasse Tyson and co-host Chuck Nice field a grab bag of listener questions on topics ranging from black holes and Hawking radiation to dark matter, exoplanet life, and the structure of the observable universe. They also discuss the feasibility of colonizing other planets, the impact of military versus science funding, how solitude enabled figures like Isaac Newton to make breakthroughs, and the role of science literacy in preventing societal self-destruction.

Topics Covered

Black holes Hawking radiation Space exploration Origins of life General relativity String theory NASA budget Science communication Simulation theory Big Bang

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Quick Takeaways

  • Nothing, not even the strongest materials, can survive the tidal forces near a black hole; ultimately even atoms and nuclei are torn apart.
  • Einstein's general relativity predicts a singularity of infinite density inside black holes, but that may signal where a new, deeper physics beyond relativity is needed.
  • Hawking radiation implies that black holes eventually evaporate and return information about what fell in, undermining the idea of black holes as portals to other universes.
  • Discovering independent life on an exoplanet-especially life not based on DNA-would revolutionize biology more profoundly than simply identifying the particle nature of dark matter.
  • Mars and other bodies in our solar system are far more hostile than even Antarctica, making true human colonization unlikely without large-scale terraforming.
  • Current U.S. science funding is tiny compared with military spending; doubling science budgets could significantly accelerate discovery, but progress also requires time and cross-disciplinary connections.
  • The observable universe appears homogeneous and the same age in all directions, leading to concepts like the cosmological horizon and inflation to explain the uniformity of temperature.
  • Our everyday distractions may be preventing modern thinkers from achieving Newton-level insights that historically arose during long periods of solitude.
  • Earth's gain of meteoritic dust is negligible compared to its total mass, while the Sun slowly loses mass via solar wind, causing planetary orbits to expand very slowly over time.
  • Respecting science, teaching people to recognize it in their daily lives, and elevating it in policymaking are framed as essential to avoid self-inflicted disasters or even extinction.

Podcast Notes

Episode setup and format

Archived episode introduction

Neil explains that the audience is about to hear an episode pulled from the StarTalk archives to address cosmic curiosities[1:18]

Cosmic Queries grab bag concept

Neil introduces the show and identifies it as a Cosmic Queries episode with a grab bag of topics[1:43]
Chuck confirms that it's a grab bag and jokes that the first question about what the queries are has already been answered[1:57]
Neil explains that usually they solicit questions on specific themes, but other questions "dribble in" and accumulate, so this episode is housekeeping to address random questions[2:27]
Chuck notes that listeners can get upset when their questions go unanswered and that this format helps make people happy by addressing older, unsorted questions[2:20]

Black holes, tidal forces, and spaghettification

Question: Can anything survive a black hole?

Listener Abdul Aziz bin Razab asks what form of matter could sustain itself and not be destroyed by a black hole, or at least hold together the longest while entering one[3:07]
Neil answers bluntly that nothing can survive a black hole; everything ultimately gets destroyed[2:57]

Tidal forces and the mechanics of spaghettification

Neil contrasts everyday material properties (eggs, steel, rubber) with what matters to a black hole: molecular and atomic bonds[3:47]
He explains tidal forces: the part of an object closer to the singularity feels stronger gravity than the part farther away, creating stretching forces[4:11]
• In a feet-first fall, your feet accelerate faster toward the singularity than your head, initially feeling like a stretch but rapidly becoming destructive
At some distance, the tidal forces exceed the molecular bonds in human tissue, snapping a person into two pieces (upper and lower halves)[4:43]
Neil notes that even a solid brick of steel, whose atoms are held together more strongly than human flesh, will reach a distance where tidal forces rip apart its molecules and atoms[5:22]
• The break-up distance for steel is closer to the singularity than for a human body, but destruction still inevitably occurs
He adds that black hole gravity will go on to rip atoms and even atomic nuclei apart; gravity wins over atoms at that scale[5:47]

Nature of singularities and limits of general relativity

Question: What happens to matter at the center of a black hole?

Chuck extends Abdul's question, asking what happens to iron and other matter during the collapse to a supermassive black hole and whether matter becomes infinitely compressed or forms some kind of core[5:58]
Neil says Einstein's general theory of relativity predicts that at the center of a black hole, matter is compressed to an incredibly small size with infinite density: a singularity[7:27]
He acknowledges that the idea of infinite density is "crazy" and possibly indicates the breakdown of general relativity in that regime[7:06]
Neil compares this to how Newtonian physics worked at low speeds and low gravity but failed at high speeds and strong gravity, requiring Einstein's relativity as an extension[8:13]
He suggests that near the singularity, another, as-yet-incomplete branch of physics may be needed to extend beyond where general relativity leaves off[8:42]

Role of string theory and possible alternatives to singularities

Neil notes that string theorists attempt to model what happens at the singularity with their own mathematical formalism[8:27]
He says either the singularity truly is infinitely small and dense, or string theory-or some future theory-will revise that picture[8:46]
He concludes that currently, no one has a definitive answer about what exactly occurs at the singularity[9:53]

Hawking radiation, information, and black holes as portals

Are black holes portals to other universes?

Neil recalls that people once hoped black holes might be portals to other places, dimensions, or universes[9:51]
He explains that modern understanding of Hawking radiation shows that information entering a black hole ultimately comes back out into this universe[10:35]
• Given enough time, a black hole evaporates, losing mass through emitted particles whose collective inventory matches the inventory of what previously fell in
Because the emitted particles carry out the same information that went in, black holes cannot transport matter to another universe while also returning that information here[11:17]

Mechanism of Hawking radiation

Neil invokes E = mc² to explain that energy and mass are interchangeable, enabling high-energy gravitational fields to create particle pairs[11:35]
Near a black hole, the energy density of the gravitational field is so high that particle-antiparticle pairs spontaneously form[12:10]
• One member of each pair falls into the black hole while the other escapes, leading to a slow evaporation of the black hole's mass
Neil highlights the "mind-blowing" aspect that the gravitational field somehow "remembers" the matter inventory it consumed in order to radiate out an equivalent portfolio of particles[13:36]
He acknowledges this result frustrates science fiction scenarios where one enters a black hole and emerges somewhere else, because the matter is instead returned to this universe[13:53]

Dark matter versus discovery of extraterrestrial life

Question: Which discovery would be more groundbreaking?

Listener Giannis asks whether understanding dark matter or discovering life beyond our solar system would be more groundbreaking, and why[12:50]

Neil's view on dark matter's potential impact

Neil notes that dark matter is the longest-standing unsolved problem in astrophysics, with about 90 years of mystery[13:08]
He says solving dark matter would be a great day for astrophysics, but the level of impact depends on what dark matter actually turns out to be[13:36]
• If it's merely another non-interacting particle added to the "particle zoo," he finds that less exciting than if dark matter were, for example, the gravitational effect of a parallel universe
He would want the solution to dark matter to have far-reaching implications, such as also explaining dark energy or helping unpack black holes, to be truly transformative[13:48]

Why discovering life elsewhere would be more profound

Neil says that in the absence of exotic implications for dark matter, discovering life on an exoplanet would be a greater breakthrough[15:12]
If exoplanet life were DNA-based, it would imply either a shared origin via material exchange between forming solar systems, or that DNA is an inevitable outcome of complex organic chemistry[14:26]
He argues that geology and chemistry repeat throughout the solar system-rocks on Mars, ice on Europa, volcanoes on Io-so it's reasonable to question why biology should be unique[14:44]
Neil emphasizes that all known life on Earth shares a common origin and basic biochemistry, making it biologically "routine" despite its diversity[16:15]
Finding life that is not DNA-based yet still self-replicating and thriving would force a major expansion of our definition and understanding of life[16:28]
• Such a discovery would let us compare a second genesis to Earth's, clarifying what aspects of life are essential versus contingent and revealing how general or flexible biology can be

Feasibility of colonizing other planets

Question: Will humans colonize other planets in our lifetimes?

Listener Riyam Samari, referencing Carl Sagan's quote that "the sky calls to us," asks whether, given modern spaceflight developments like SpaceX, we will see humans colonize other planets or find intelligent life beyond Earth in our lifetimes[22:44]
Neil answers "no" regarding colonization within our lifetimes and stresses he has reasons rather than just pessimism[23:34]

Mars as the most plausible but still hostile option

Neil argues Mars is the only somewhat plausible planet for human presence in our solar system, given its polar caps, seasons, and past liquid water[24:03]
He dismisses Venus as being around 900°F (about 500°C), hotter than a pizza oven, and Mercury as similarly too hot for human habitation[24:37]
Neil compares Mars to Earth by noting that Antarctica is wetter and balmier than any location on Mars, yet people are not lining up to buy condos in Antarctica[24:53]
He predicts that living on Mars would have novelty appeal but that people would likely want to return to Earth rather than remain permanently[26:02]

Need for terraforming and problems with historical analogies

Neil argues that to truly colonize other planets, we would first have to terraform them to be Earth-like so that humans could step out of a spacecraft and breathe without dying[26:14]
He contrasts this with historical exploration: when Columbus reached the New World, he could breathe the air, meet people, eat local fruit, and repair ships because the environment was broadly compatible[26:53]
He criticizes analogies that treat interplanetary settlement as similar to early Earth exploration, because in space you die if you simply step off the ship[27:01]

Ethical considerations for encountering extraterrestrial life

Neil notes that if we find civilizations or life forms elsewhere, we should have learned from colonial history and have a playbook for interacting responsibly with beings that greet us[27:34]
He mentions NASA's planetary protection protocols: outbound probes must be sterilized so earthly microbes (like rhinovirus from a sneeze) do not contaminate other worlds[29:45]
He adds that any returned samples must be quarantined before release on Earth to avoid contaminating our biosphere[29:56]
Neil reiterates that while visiting other planets is plausible, true colonization is unlikely any time soon[31:34]

Science funding, military budgets, and lost centuries

Question: What if military spending went to science?

Listener Duan only asks how far scientific advancement might go if the U.S. military budget were redirected toward science and technology[29:19]

Current scale of science vs military spending

Neil cites approximate figures: National Science Foundation around $30 billion, NASA around $20 billion, totaling about $50 billion[30:06]
Including other science portfolios like the National Institutes of Health, he estimates total U.S. science research spending at roughly $70-100 billion[30:03]
He contrasts this with about $600 billion spent annually on the U.S. military, much of which covers the cost of maintaining standing forces rather than pure R&D[31:28]

Limits of "throwing money" at science and the role of time

Neil cautions that simply throwing vast sums at science does not linearly translate into discoveries; science often advances via unexpected results and ideas that need time to germinate[32:12]
He describes the peer-review grant system where only 10-50% of applications are funded; many meritorious proposals are left unfunded for lack of money[31:29]
Neil suggests that doubling existing science budgets could appropriately fund more high-quality ideas and "punch science along" at the rate it should progress[33:14]

Historical delays due to anti-scientific attitudes

Neil reflects that civilization lost centuries of potential progress due to the Dark Ages and periods when natural phenomena were attributed to gods or supernatural causes instead of investigated scientifically[33:28]
He speculates that if societies had embraced science earlier instead of persecuting it, humans might have reached the Moon in the 19th century instead of the 20th[33:14]
He stresses that progress requires not just discoveries but also "bridges and tunnels" connecting advances across fields so innovations can exploit prior knowledge[35:08]
Neil notes with concern that modern societies sometimes regress toward denying science, implying this could again slow or reverse progress[36:14]

Cosmic horizons, center of the universe, and the horizon problem

Question: Are we at the center of the universe and what is the horizon problem?

Listener njonesy19 asks about the horizon problem and notes that from any location it seems one is at the center of the universe, raising the question of whether there is a true center[33:58]

Analogy with horizons at sea

Neil uses a ship-at-sea analogy: for a person at sea level, the distance to the visible horizon is the same in every direction, and increases if you climb higher[35:14]
Each ship in the ocean has its own circular horizon, making everyone the center of their own horizon, even though Earth has no special center in this sense[36:01]
He notes that in principle there could be positions in the universe where the horizon distance differs by direction, but observationally we don't see that[35:50]

Cosmological horizon and uniformity of the Big Bang

Neil explains that in every direction we look, when we peer about 14 billion light-years away, we see the beginning of the universe (the Big Bang) just now reaching us[36:25]
If in one direction we instead saw a normal galaxy at that distance, that would indicate we were near a cosmic "edge" or asymmetry, but we do not observe that[37:06]

Technical meaning of the horizon problem and inflation

Neil clarifies that what the listener asked is related but not identical to the technical "horizon problem" in cosmology[38:10]
A key aspect of the horizon problem: widely separated regions of the universe (on opposite sides of the sky) have nearly identical temperatures, differing by only about one-hundredth of a degree Kelvin[37:57]
• He points out that we don't see such uniform temperatures even across a single room, let alone across the entire observable universe, making this uniformity surprising
The puzzle is how such distant regions could have "known" to be the same temperature unless the universe was once small enough and in causal contact[37:44]
Neil notes that this led to the idea of inflationary cosmologies, in which the early universe underwent rapid expansion after previously being in close contact with itself[38:12]
He distinguishes between the "weeds" of technical Big Bang issues-like the horizon problem-and the broader picture that the universe began in an expansion about 14 billion years ago, which remains intact[38:20]

Earth's mass gain, solar mass loss, and orbital effects

Question: Will added meteoritic mass change Earth's orbit?

Listener P.N. Wonders asks when Earth's continuous gain of mass from space material will become large enough to affect its orbit, and what that effect would be[41:35]

Scale of meteoritic infall vs Earth's mass

Neil states that Earth plows through several hundred tons of meteor dust per day[42:00]
He suggests multiplying that daily mass by 365 days and then by 4 billion years to estimate the cumulative added mass, then comparing it to Earth's total mass[42:26]
He says the effect is comparable to a gnat flying into an elephant and the elephant saying "hey, quit the shoving"-in other words, utterly negligible[43:28]
Neil concludes that Earth's orbital change from added meteoritic dust is effectively zero and not a concern[43:02]

Sun's mass loss and outward orbital drift

Neil notes that the Sun is slowly losing mass via the solar wind-streams of particles blowing off its surface[42:39]
As the Sun loses mass, its gravitational pull weakens, making Earth's current orbital speed slightly too fast for a perfectly circular orbit, causing Earth to slowly spiral outward[45:14]
He adds that over billions of years, increasing mass loss from the Sun will push all planetary orbits farther out, one of the fates of the solar system[45:44]

Size of the observable universe

Question: How is the 43-billion-light-year radius determined?

Listener "Bugger Dude" first offers a humorous comment about not having good questions, which Neil replies to by inviting any question and emphasizing it's his answers that should be judged[43:28]
Another listener asks how astronomers determined that the edge of the observable universe is 43 billion light-years away[43:37]

Difference between light-travel distance and current distance

Neil explains that astrophysicists often say the edge of the universe is 14 billion light-years away because that's how long the light has been traveling to reach us[44:22]
However, the objects that emitted that light have continued participating in cosmic expansion, so their current distance is now about 43-45 billion light-years away[45:00]
He notes that the diameter of the observable universe (current distance) is therefore around 90 billion light-years, even though we can only directly observe the 14-billion-year light travel distance[45:00]
Neil emphasizes that cosmologists prefer to anchor descriptions in what is directly observable, while also being able to calculate the current separation based on the known expansion rate[45:06]

Isaac Newton, solitude, and modern distractions

Question: How did Newton stay so focused during the plague?

Listener Akshat from India asks how Isaac Newton could be so deeply focused and productive-discovering laws of motion, gravity, calculus, and optics-during the plague, and how we can manage our own mental health and creativity amid modern anxiety[46:50]

Role of enforced solitude in historic breakthroughs

Neil clarifies he is not a mental health expert but knows the history of Newton and other major scientific figures[47:33]
He notes that many of them experienced long periods of solitude-sometimes enforced, as when Newton left London and Cambridge during the Black Plague-which gave their minds space to explore[47:51]
Neil contrasts this with today's quarantine experiences: some people are alone but fill their time with streaming and online entertainment instead of deep thought[48:13]
He laments that modern distractions like on-demand TV and social media may be preventing brilliant people from making potentially transformative discoveries[49:02]

Newton's personality and how it fit solitude

Neil points out that Isaac Newton appears to have been socially distant by nature-possibly a misanthrope-who never married and had no children[49:27]
For someone who did not enjoy the company of others, being sent to a country home away from crowded cities during the plague was almost a "godsend" for uninterrupted thought[50:58]
Neil notes his own disappointment that during coronavirus quarantines, he has not given himself enough solo thinking time, instead catching up on email and cooking with his wife[50:23]
He reiterates that deep, solitary periods-going for walks or staring at the ceiling-are unattractive compared to entertainment but historically fertile for major insights[51:31]

Microphysics inside black holes: nuclei and quarks

Question: Do particles reach light speed falling into a black hole?

Listener Alfredo Baldo Castiano asks if, given that a black hole is a point of infinite density, gravitational acceleration could cause infalling particles to reach the speed of light[52:09]

Escape velocity and particle speeds near black holes

Neil explains escape velocity: at the event horizon it exceeds the speed of light, meaning even light cannot escape once inside[52:27]
He notes that objects with more than escape velocity would continue outward but those with less fall back; however, typical infalling matter does not reach anywhere near light speed relative to the local spacetime the way the question suggests[53:36]
He emphasizes that most matter spirals into a black hole through an accretion disk rather than plunging straight in, complicating the intuitive picture of free-fall acceleration[53:32]

Question: What happens to quarks when nuclei are spaghettified?

Listener flvoq notes hearing about nuclei getting spaghettified and asks what happens to quarks inside those nuclei[54:39]
Neil replies that he does not know for certain but suspects that quarks would also be spaghettified by the extreme tidal forces[54:40]
He reiterates that black hole environments are extremely destructive, ultimately tearing apart atoms, nuclei, and likely subnuclear components; nothing survives intact[54:14]
Neil jokes that everything falling into a black hole gets spaghettified except spaghetti, which is already spaghettified and so "goes straight in"[55:54]

Simulation theory mention

Question: How likely is simulation theory?

Listener Teague Gweathen asks for Neil's thoughts on simulation theory and how likely it is that our reality is a simulation[56:28]
Neil says his thinking has changed recently and he now believes there is a better chance that we are not in a simulation than he had previously thought[56:36]
He references a separate explainer video where he elaborates on his reasoning, and the podcast does not go into further detail here[56:58]

Science, politics, and preventing mass extinction

Question: How can we prevent extinction when governments ignore science?

Listener Michael Bruce asks how humanity can prevent a mass extinction event when governments seem to listen more to donors than to scientific facts[57:19]

Need to elevate science in public perception

Neil reframes the question as how to elevate science to a place of respect among political leaders[57:34]
He suggests that science might paradoxically need better "advertising" so people appreciate its pervasive role in their lives[57:42]
Neil points out that most people alive today owe their lives to scientific advances in food production, prenatal care, sanitation, and medicine[57:55]
He argues that people take these embedded benefits for granted, which diminishes respect for science and makes it easier for leaders to ignore it[58:07]

Teaching science recognition and historical example of Apollo

Neil proposes that education should train people to recognize "that's science" in daily life so that science literacy is woven into culture without needing ad campaigns[58:15]
He recalls that during the Apollo program, people were constantly reminded of science because of the visible achievement of going to the Moon, and many students rushed into STEM fields without the need for extra incentives[58:45]
Neil warns that without greater respect for science, short-sighted political decisions could lead to disasters or even extinction; he notes that every disaster movie begins with ignoring scientists' warnings[58:45]
He closes the episode by encouraging continued curiosity and "keeping looking up" as part of the StarTalk ethos[59:28]

Lessons Learned

Actionable insights and wisdom you can apply to your business, career, and personal life.

1

Deep, uninterrupted solitude is a powerful catalyst for original thinking and major breakthroughs, whereas constant distraction-even by enjoyable media-can silently erode your creative potential.

Reflection Questions:

  • • When was the last time you spent an hour alone without any digital distractions, simply thinking or observing?
  • • How might scheduling regular blocks of solitude each week change the quality of your ideas and problem-solving?
  • • What is one specific distraction you could reduce or eliminate this week to create more mental space for deep thought?
2

Scientific progress depends not only on funding but also on time, cross-disciplinary connections, and a culture that trusts and understands science rather than treating it as optional or adversarial.

Reflection Questions:

  • • In what ways do you currently rely on scientific advances in your daily life that you rarely acknowledge?
  • • How could you help bridge gaps between different domains of knowledge in your work or community to spark better solutions?
  • • What is one concrete action you could take this month to support or advocate for evidence-based decision-making where you live or work?
3

Analogies from familiar history, like colonial exploration, can be misleading when applied to radically different contexts such as space colonization; understanding the underlying constraints matters more than the surface similarity.

Reflection Questions:

  • • Where in your life are you relying on an analogy that might ignore critical differences in context or scale?
  • • How could you more systematically examine the assumptions behind the comparisons you make when planning or arguing for something?
  • • What is one important decision you're facing now where you should explicitly list the ways your situation differs from the example you're using as a model?
4

The fact that physics breaks down or becomes paradoxical in extreme regimes (like black hole singularities) is not a failure but a signpost pointing toward new, deeper theories waiting to be developed.

Reflection Questions:

  • • What "edge cases" or failures in your current methods or beliefs might be signaling the need for a new approach rather than just a patch?
  • • How can you reframe confusing or contradictory data in your work as clues to a better model instead of problems to ignore?
  • • What is one domain in your life or business where you could deliberately investigate the limits of your current tools to learn where innovation is needed?
5

Recognizing that we live inside a vast, evolving system-whether it's the universe, an economy, or an organization-encourages humility and long-term thinking instead of narrow, short-term moves that can lead to systemic disaster.

Reflection Questions:

  • • How often do you consider second- and third-order consequences of your decisions beyond the immediate results?
  • • In what situations could a more "cosmic" perspective help you zoom out from daily frustrations and see the larger pattern you're part of?
  • • What is one decision you're making this week where explicitly thinking about long-term system effects could change what you choose to do?

Episode Summary - Notes by Kai

Cosmic Queries - Get Some Space
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