The Mass of 3I/ATLAS is About a Billion Metric Tons, at Least a Hundred Thousand Times That of…
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By CosmicSignals
With the upcoming launch of the Lunar Gateway's first modules, I can't help but feel a sense of anticipation about what this means for lunar exploration. The Gateway is positioned to play a crucial role in supporting missions to the Moon and eventually Mars. It’s fascinating how this project integrates international collaboration and advanced technology to create a sustainable presence in lunar orbit.
One aspect that intrigues me is the modular design of the Gateway. Each module will serve a specific purpose, from crew habitation to research facilities. This approach not only allows for flexibility in missions but also makes it easier to upgrade and expand the Gateway over time. It seems like a huge leap from the static space station model we've grown accustomed to.
I'm curious about the scientific opportunities that will arise from this platform. With the Gateway acting as a staging point for lunar surface missions, the possibilities for research on lunar geology and the solar system are immense. It could even serve as a launchpad for studying deeper space phenomena. The idea of utilizing the Moon as a springboard for further exploration is intriguing.
Another point that’s been on my mind is the technological advancements that will likely come from this initiative. We’ve seen how projects like the ISS have pushed the boundaries of what we can achieve in microgravity. What innovations do you think will emerge from the Lunar Gateway? Will we see new technologies that could potentially benefit life on Earth?
As we get closer to the launch date, I can't help but feel hopeful about the future of space exploration. The Gateway represents an opportunity not just to explore our Moon, but to forge a path toward human presence on Mars and beyond. How do you all feel about this mission? Are there specific aspects of the Lunar Gateway that excite you the most?
It’s also interesting to think about how the Gateway will facilitate a greater understanding of our own planet. With the Earth view from the Moon and the Gateway, there could be unique opportunities for Earth science research. I wonder if anyone has specifics about collaborations targeting climate science from this vantage point.
Overall, I think this is a pivotal moment for space exploration, and I’m eager to see how everything unfolds over the next few years. Let’s keep the conversation going as we anticipate this exciting launch!
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By Avi Loeb Medium
A 1.5-Solar-Mass Star in a Tight Orbit Around the 4.3-Million Solar-Mass Black Hole at the Milky-Way Center
Time series of the orbits of various stars around the supermassive black hole, SgrA*, at the Milky-Way center, obtained from data by GRAVITY/VLT between 2021 to 2025. The new star S301 arrives within 140 Schwarzschild radii of the black hole where its peak velocity is 8.3% of the speed of light, 25,000 kilometers per second. (Image credit: Abd El Dayem et al. 2026)The fastest moving star, labeled S301, was discovered recently by Stefan Gillessen’s team at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany (as first reported here, with the full paper accessible here). The star was discovered by near-infrared interferometry on 8-meter telescopes, using the GRAVITY instrument in operation at the European Southern Observatory’s (ESO’s) Very Large Telescope (VLT). Last night, I sat next to Stefan at the reception dinner of the annual conference of Harvard’s Black Hole Initiative, for which I served as the founding director a decade ago.
This 1.5-solar-mass star moves on a highly elliptical orbit with a period of 8.7 years and eccentricity of 0.98 around the supermassive black hole at the Milky-Way center, called Sagittarius A*. This black hole has a long history of swallowing 4.3 million solar masses of gas and stars from its environment. The peak velocity of S301 is 25,000 kilometers per second or 8.3% of the speed of light, as it comes down to a distance of 140 times the Schwarzschild radius of the black hole — which defines the scale of the black hole mouth from where even light cannot escape. If the star were to pass ten times closer to the black hole, it would have been ripped apart by tidal gravity into a stream of gas that shines brightly as it feeds the mouth of this spacetime beast.
The orbit of S301 can be used to test expectations from Albert Einstein’s formulation of gravity as the curvature of spacetime. Einstein’s equations predict that S301’s orbit will precess in response to the spin of the black hole, offering a precise new way to measure how fast Sagittarius A* is rotating within the coming decade.
How did this star get so close to the black hole?
A natural mechanism, proposed by Jack Hills in a 1988 paper published here, is the tidal break-up of a pair of stars by the black hole. About half of solar-mass stars form in binaries. When a binary star system gets close enough to the black hole, the tidal gravity becomes strong than the gravitational binding of the two stars and breaks the binary apart, sending one star out at a speed of up to thousands of kilometers per second and launching the second star into a tighter orbit around the black hole. Indeed, a population of hypervelocity stars had been discovered on their way out in the Milky-Way halo by Warren Brown and collaborators from the Harvard-Smithsonian Center for Astrophysics (as reported here).
In a 2006 paper published here, I proposed with the student, Idan Ginsburg, that the former companions of the observed hypervelocity stars in the Milky-Way halo might have produced the observed population of close-in S-stars on highly eccentric orbits around Sagittarius A*. The Galactic center star S301 is likely one of them, formed via the Hills mechanism out of an initial binary star system with an orbital period of 1–2 weeks over the past 100 million years.
In a follow-up paper published here, I showed with Idan that planets could survive the break-up of binary star systems by Sagittarius A*. As a result, Galactic travel agencies could sell tickets for thrilling journeys on habitable planets around hypervelocity stars. I wonder whether adventurous Galactic passengers would prefer to travel with a hypervelocity star on its way out of the Milky-Way galaxy at a speed of up to 1% of the speed of light or travel with a star like S301 as it reaches 8.3% of the speed of light and gets within a distance of 140 Schwarzschild radii from the largest black hole in our Galaxy. I would personally favor the latter, since the extreme spacetime structure of a supermassive black hole is far more exhilarating than the rarefied environment of intergalactic space. The trip close to the black hole also offers health benefits, since aging slows down by a third of a percent at closest approach of S301 to Sagittarius A*. This corresponds to a gain of 5 minutes to the passenger’s lifespan every day relative to distant relatives.
The black hole tour with S301 offers a view of the black hole’s mouth from a distance where it occupies roughly the same angle as the Moon or the Sun on our sky. The gas swirling into the event horizon of Sagittarius A* glows bright but at the center of this glow, there is a silhouette — a shadow cast by the absorption of light emanating behind the black hole. Over the decade between 2006 and 2016, I wrote 30 papers in collaboration with my postdoc, Avery Broderick, forecasting the expected portrait of a black hole (as detailed here and summarized for the general public here). By now, Sagittarius A* was imaged by the Event Horizon Telescope (here), whose headquarters was established at Harvard’s Black Hole Initiative during my directorship.
On a tour with S301, it would be fascinating to observed the silhouette image of Sagittarius A* from a minimum distance that is 140 million times closer than the Earth is from the black hole. I would have loved to serve as the tour guide on such a journey. Here’s hoping that Galactic travel agents would pay attention to this essay.
ABOUT THE AUTHOR
(Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
Professional website:
https://lweb.cfa.harvard.edu/~loeb/
Social media:
https://avi-loeb.medium.com/
https://www.youtube.com/@ProfessorAviLoeb
https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd
https://x.com/ProfAviLoeb
View the full article
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By Avi Loeb Medium
(Image credit: Scientific American)In recent months, two papers (accessible here and here) suggested the existence of an abundant population of negative mass objects in the Universe. Albert Einstein’s theory of gravity, General Relativity, allows negative masses, as discussed in a seminal 1957 paper published here by the physicist Herman Bondi. In 2015, Robert Forward showed in a paper available here how negative masses can be used for propulsion without fuel. But as I explained in a recent essay here, we have no idea whether negative masses can be constructed in reality. In fact, their existence would create fundamental problems in our current understanding of the physical world. For example, negative masses can be used as building blocks in engineering a time machine which would violation causality, as I explained in an earlier essay here.
In principle, there are three types of mass:
1. Inertial mass, namely the mass given by the ratio between the force acting on an object and its resulting acceleration.
2. Active gravitational mass, namely the mass that generates the gravitational field around the object and affects the motion of other objects.
3. Passive gravitational mass, namely the mass that couples the object to the external gravitational field generated by other objects.
Momentum conservation requires that the active and passive gravitational masses would be equal. Otherwise, the momentum gained by one object will not necessarily be balanced by the momentum lost by another object when the two interact gravitationally with each other. Momentum conservation is a consequence of spatial translational symmetry, namely the invariance of the laws of physics to shifting a system from one position to another. Therefore, it is a sacred principle that cannot be violated.
The equality of the inertial mass and the passive gravitational mass is a fundamental assumption, called the Equivalence Principle, in Einstein’s theory of General Relativity. It rests on a pioneering experiment by Galileo Galilei at around 1590 and numerous follow-up experiments, which demonstrated that all objects accelerate the same way under the action of gravity irrespective of their mass or composition. In discussing negative mass objects, it is often assumed that conservation of momentum and the Equivalence Principle are both valid, and so all three forms of mass are the same.
However, the Equivalence-Principle rests on observational data for positive masses and could potentially be violated for negative masses. A new paper (available here) that I just co-authored with the brilliant PhD student, Oem Trivedi, shows that a system made of two objects which possess different values of the ratio between their gravitational and inertial masses would emit dipole gravitational radiation instead of the usual quadrupole gravitational radiation. The situation is analogous to a system made of positive and negative electric charges with positive inertial masses. So far, no sign of dipole gravitational radiation has been detected by the LIGO- Virgo-KAGRA (LVK) gravitational wave observatories. Current limits on dipole gravitational radiation are tight, as discussed here.
But even if the Universe contains only negative masses which satisfy the Equivalence Principle, binary systems containing such masses are expected to generate never-seen-before gravitational-wave signals:
1. Systems with a negative total mass are repulsive and short lived, preventing the formation of stable binaries.
2. Systems with a positive total mass, where the negative mass is smaller in magnitude than the positive mass, can form circular orbits. However, their evolution under gravitational radiation leads to expansion rather than inspiral, producing anti-chirp signals with decreasing frequency. Such a waveform is opposite to the chirp observed for all gravitational wave sources so far by LVK. The absence of anti-chirp signals in current gravitational wave catalogs provides a direct observational constraint on negative mass binaries. For an ordinary positive-positive binary, the orbital energy is negative and becomes more negative as the binary separation decreases, so gravitational-wave energy loss drives the system toward inspiral and increasing frequency. For a positive-negative binary with a positive total mass, the orbital energy starts being positive and decreases toward zero as the binary separation grows, so the same loss of gravitational-wave energy causes the system to expand rather than contract.
3. Systems with a zero total mass, where the negative mass cancels the positive mass precisely, correspond to runaway solutions where the pair accelerates up to the speed of light in some direction rather than engage in periodic motion.
So far, the new observational frontier of gravitational wave astrophysics did not lead to the discovery of new unexpected sources in our Universe over the past decade. This is somewhat disappointing and out of line with the history of astronomy, where observatories in a new band of the electromagnetic spectrum always revealed new unexpected sources. This was the case with radio telescopes discovering the cosmic microwave background, complex interstellar molecules or fast radio bursts; X-ray telescopes discovering accreting black holes, the cosmic X-ray background or X-ray clusters, and gamma-ray telescopes discovering gamma-ray bursts, gamma-ray pulsars or the cosmic gamma-ray background.
Our new paper shows that binary systems with negative mass members would generate gravitational-wave signals with never-seen-before properties. They provide novel targets for gravitational wave observatories which could either find them or rule them out.
ABOUT THE AUTHOR
(Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
Professional website:
https://lweb.cfa.harvard.edu/~loeb/
Social media:
https://avi-loeb.medium.com/
https://www.youtube.com/@ProfessorAviLoeb
https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd
https://x.com/ProfAviLoeb
View the full article
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By Avi Loeb Medium
(Image credit: The Sun)Could artificial intelligence (AI), machine learning (ML), large language models (LLM) or natural language processing (NLP) help us figure out the nature of Unidentified Flying Object (UFOs) or Unidentified Anomalous Phenomena (UAP), by analyzing verbal reports from humans?
Today, I received an email from a group of researchers who stated: “We’ve been working on a machine learning project that classifies reports from the National UFO Reporting Center by narrative “dramaticness,” essentially modeling the language and content of witness reports to distinguish brief, ambiguous observations from highly detailed extraordinary accounts. The pipeline combines structured features, free-text NLP, gradient-boosted models, and an LLM baseline, with explainability built in. We see this as a content-side complement to instrument-side efforts like the Galileo Project: the witness reports are noisy and selection-biased, but they’re also the longest continuous record of public UAP reporting we have, and the language inside them turns out to carry a lot of structure.”
My response clarified the following fundamental points.
In scientific research, low significance data is most abundant but is of little use because it is often swamped by noise. UFOs or UAP are a mixed bag with many reports triggered by human-made or natural phenomena. Humans cannot be trusted as scientific detectors. We need instruments to document the evidence.
This is evident from the legal system, where convicts who were put on death row based on eyewitness testimonies under oath, were later exonerated based on DNA tests. Among 51 cases of death row exonerations, a study posted here found that 45.9% involved informants, while 25.2% involved erroneous eyewitness identification. The same level of misinformation is also evident in common reports on car accidents, where testimonies are often full of imagined narratives and wishful thinking. Stories told by different people about the same car accident are different and sometimes contradictory. Given that there is only one physical reality, they cannot all be correct. Ambiguities are best resolved not by AI/ML/LLM/NLP systems analyzing verbal testimonies, but rather by multiple video cameras observing the car accident.
Since humans know about each other’s story, their narratives are often interwoven and correlated. The fundamental question is whether any of them is right. This is well known to FIFA (Fédération Internationale de Football Association), the soccer worldwide organization. Instead of consulting the goalkeeper or the numerous fans in the audience and using AI/LLM to sort through their narratives, FIFA uses advanced camera-based technologies, including Goal-Line Technology (GLT) and Video Assistant Referee (VAR), to confirm goals, offsides, and fouls. GLT uses 14 high-speed cameras to confirm if the ball crosses the line and sends a signal to the referee within one second, while VAR reviews video footage for overall accuracy.
We can spend a lifetime chasing ghosts based on verbal reports or low-quality data. The Galileo Project under my leadership is focused on getting high-quality data from multiple observing directions, allowing us to infer the distance, velocity and acceleration of objects in the sky. Without distance measurements, it is difficult to assess how anomalous a moving object is. Having a lot of uncertain information is not of interest to the Galileo Project, irrespective of how advanced the AI/ML system that analyzes it is.
On April 17, 2026, President Trump announced in a speech, accessible here, that the first release of classified UFO files will be coming out very soon. As I discussed in a previous essay, posted here, the question is whether the released videos will be the most intriguing ones. Being flooded by blurry videos with no information about the distance of UFOs from the camera will not resolve ambiguities about whether they deviate from the performance envelope of human-made technologies.
When information is limited, intelligence has limited powers. It matters less how advanced the AI/ML/LLM/NLP being used is. What matters the most is the quality of the data. A picture is worth a thousand words. For the same reason, high quality data is worth a thousand LLMs.
ABOUT THE AUTHOR
(Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, former director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics (2005–2026), and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
Professional website:
https://lweb.cfa.harvard.edu/~loeb/
Social media:
https://avi-loeb.medium.com/
https://www.youtube.com/@ProfessorAviLoeb
https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd
https://x.com/ProfAviLoeb
View the full article
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By Avi Loeb Medium
Stars in the dwarf galaxy Pictor II, which is more than 10 billion years old. The right panel shows a close-up of the star PicII-503, with the lowest iron content ever measured outside of the Milky-Way disk of stars. (Image credit: CTIO/NOIRLab/DOE/NSF/AURA)One of the remarkable insights in the biblical story of genesis is that the observable Universe had a beginning in time, akin to the modern notion of a Big Bang. This idea was not philosophically appealing to scientists like Albert Einstein, who in 1917 added a cosmological constant to his equations of General Relativity, in order to counteract the gravitational attraction of matter and radiation and allow for a static eternal Universe. He later realized that such a delicate balance is unstable and leads to a clumpy Universe. Indeed, today cosmologists explain the emergence of galaxies like the Milky-Way as a natural consequence of gravitational instability in an expanding Universe which contains a cosmological constant.
How can we infer the current age of the Universe?
Locally, we find that the Universe is expanding with the recession speed of distant galaxies being proportional to their distance. The proportionality factor, called the Hubble constant after the astronomer Edwin Hubble, is the ratio between the recession velocity and distance. The time that elapsed since these galaxies overlapped equals to their distance divided by their velocity. Crudely speaking, this would imply that the age of the Universe is simply the inverse of the Hubble constant. For the current value of Hubble constant, about 70 kilometers per second per megaparsec, its inverse is 14 billion years.
The value of the Hubble constant is still uncertain, as different techniques for distances measurements provide values that are discrepant by +/-5%, as summarized here. This ambiguity amounts to an age uncertainty of 0.7 billion years.
A more refined approach is to trace the distance that light travelled since the beginning by studying the Cosmic Microwave Background (CMB), the relic radiation from the Big Bang. The Universe became transparent to the CMB as soon as the cosmic temperature cooled under 4000 degrees Kelvin, allowing electrons to join protons in making hydrogen atoms. This removed the fog associated with electron scattering of the CMB at about 400,000 years after the beginning. The distance that sound waves propagated during that time defines a yardstick for the characteristic CMB brightness patterns. The angle that it occupies in the sky depends on the distance travelled by the CMB since that time which — given the speed of light — reflects the age of the Universe. The acoustic patterns can also be found in the large-scale distribution of matter, as traced by galaxies at recent cosmic times. This approach yields a cosmic age of about 13.8 billion years.
The Sun formed in the last third of cosmic history, 4.6 billion years ago, and our modern technological era is only a century old. We arrived late to the cosmic party.
Most stars formed before the Sun. This offers a second path for measuring the age of the Universe. No star can be older than the Universe for a simple reason. As we go back in time before the first minute after the Big Bang, the cosmic density of matter and radiation was much higher than that found in the interior of stars. No star could have not survived these extreme conditions in the infant Universe. Cosmic archaeology can therefore set a lower limit on the age of the Universe by finding ancient stars that formed in the first hundreds of millions of years after the Big Bang.
Recent data from the Dark Energy Camera (DECam) mounted atop the Víctor M. Blanco 4-meter Telescope in Chile, revealed stars inside the nearby dwarf galaxy Pictor II at a distance of 150,000 light years. This satellite galaxy of the Milky-Way is more than 10 billion years old. One of the oldest of these stars is PicII-503, with only a part in 43,000 of the iron mass-fraction of the Sun, as reported last week here.
Another path for cosmic archaeology involves studies of the materials carried by interstellar objects, born out of the debris of distant stars. They also cannot be older than the Universe. The age of interstellar objects can be inferred by isotope dating. Remarkably, the measurement of deuterium to hydrogen and 12C/13C ratios, as reported here and here last week, implies that the age of the interstellar object 3I/ATLAS is 10–12 billion years, suggesting that it may have formed in the early Universe. As I discussed here, this raises a puzzle regarding the mass reservoir of its parent star population.
***
Jeanne Calment of France is the oldest verified person to have ever lived. She died in 1997 at an age of 122.45 years. This is a hundred million times shorter than the age of the Universe. One would expect the fact that we live for less than 0.00000001 of cosmic history to sink in and make us humble. But not so. We prefer to ignore it.
Even though our life is brief, we choose to invest most of it in conflicts with each other. Out there in the sky, there is a giant cosmic message telling us how insignificant we are. And yet, even mainstream astronomers who adopt the job of looking up, maintain the arrogant view that we might be at the top of the cosmic food chain and that the quest for extraterrestrial technological civilizations is an extraordinary claim that should be sidelined in favor of the search for microbes. How else can one interpret the top priority of the Astronomy & Astrophysics Decadal Survey to invest more than 10 billion dollars in the search for microbes and no federal funding in the search for extraterrestrial intelligent beings?
Given the dismal brevity of our cosmic existence, we get comfort from the assumption that the we must be surrounded by lower life forms.
I reject this popular view within present-day academia. Out of a sense of cosmic modesty, I define my goal throughout the remainder of my scientific career to seek evidence for a more accomplished sibling of our family of intelligent civilizations. If such evidence will be found, the next Copernican revolution would be that we are not at the intellectual center of the Universe.
***
Before my morning jog at sunrise, I had received the following uplifting email from the Finnish artist, Antti Railio:
“Hello Mr. Loeb.
My name is Antti Railio, I am a Finnish singer/artist. I have been following your work for few years now and I am really happy to see a scientist who practices real science with the correct attitude towards it.
I also have had an interest on the UAP/UFO phenomenon since the 1990’s since I have witnessed along with other people the phenomenon of bright orbs up upon the ocean here in Finland in my home town of Kristiinankaupunki.
Also, I had an experience when I was a child which left me with 7 Stiches on my left palm…
Well, that is beside my letter to you…
I wanted to write to you, since I am not a scientist, but I have a curious mind, and it seems I tend to have Ideas or theories that time and time again seems to be after sometimes decades validated by scientists.
For example, I had a theory that our universe might be inside a black hole and possibly the multiverse is like a bunch of soup bubbles. I had this idea 20 years ago… And since few years ago I read that this is now a well thought theory…
I also have had a theory that life on earth had its origins somewhere else possibly the same life source that has been spread through the universe by panspermia. And I somehow am almost certain that this is the case.
Anyway, my main reason for contacting you is this new theory I have… I just had an idea a few days ago popped to my brain!
What would you think of this? You know the theory of white holes being the theorized flip sides of a black whole, but that we have not yet been able to seen or proven their existence ones…
My theory is this: We are all made of the same material that exists inside the Sun as they say and Sun gives us life and illuminates the whole solar system…
What if stars are the other side of a black holes, a reverse singularity! If I am not wrong a black hole appears in 3-dimensional space as a sphere?
So my theory is that one of the reasons the Sun’s temperature is far more greater farther from its surface, is also driven by the forces pushing through the matter from a far distant black whole that is at the same time at the other side of the sun, so that it is occupying basically the same space as the Sun and at the same time it is connecting our solar system with another one somewhere where the black hole resides… Also the black hole’s immense gravitation would keep the sun at its form, but since it is constantly feeding in from the other side it has to disperse the energy gradually away thus the heat and photons would then be the Sun’s source of light and energy…
The immense gravitation would still bleed through its presence over to this side keeping the planets locked in their places…
Also, that would make sense in another theory connecting to UAP…
It would make sense that higher beings would be aware of this and could use stars as a map of “jump points” to travel vast distances by using portals created by the universe…
You know, sometimes the obvious is hiding right in front of our eyes… ;)
That is my newest theory but I lack the scientific knowhow to even start to calculate the mathematics or the more technical sides of this theory, so I leave it to you as a fun theory or perhaps something to be thinking about … :)
With the most respect and admiration
Thank you so much for your time!
Also, I am super excited about your Galileo Project! And secretly wish to grow up and start my scientific career. But maybe I am better at singing and performing…
Yours truly!
-Antti Railio”
My response was as follows:
“Dear Antti,
Thank you for reaching out to me and for your kind words.
Your idea about panspermia might very well be correct. For the latest update, see my essay from last week:
https://avi-loeb.medium.com/impact-survival-of-microbes-highlights-the-feasibility-of-panspermia-45b7c6bc78dd
It is possible that our Universe is embedded inside a black hole but we have no evidence for that. A black hole is characterized by a singularity at its venter (a place where the curvature of spacetime diverges), very different from the nearly uniform conditions in the observable volume of the Universe.
Regarding the Sun and other stars: we can explain their properties, including their internal structure — which is probed by sound waves, as a result of nuclear fusion being their source of energy. Once they consume their nuclear fuel, they die and we see their remnants in the forms of white dwarfs (for Sun-like stars), neutron stars and black holes (for stars more massive than 8 solar masses). A white hole was conjectured as the source of energy for quasars or gamma-ray bursts, but these sources of light are well explained by a model involving the infall of matter into a black hole.
Keep up with your creative work.
Avi”
ABOUT THE AUTHOR
(Image Credit: Chris Michel, National Academy of Sciences, 2023)Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
Professional website:
https://lweb.cfa.harvard.edu/~loeb/
Social media:
https://avi-loeb.medium.com/
https://www.youtube.com/@ProfessorAviLoeb
https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd
https://x.com/ProfAviLoeb
View the full article
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