Voyager 1, shown in this illustration, has operated for decades thanks to a radioisotope power system. NASA via APBenjamin Roulston, Clarkson University Powering spacecraft with solar energy may not seem like a challenge, given how intense the Sun’s light can feel on Earth. Spacecraft near the Earth use large solar panels to harness the Sun for the electricity needed to run their communications systems and science instruments. However, the farther into space you go, the weaker the Sun’s light becomes and the less useful it is for powering systems with solar panels. Even in the inner solar system, spacecraft such as lunar or Mars rovers need alternative power sources. As an astrophysicist and professor of physics, I teach a senior-level aerospace engineering course on the space environment. One of the key lessons I emphasize to my students is just how unforgiving space can be. In this extreme environment where spacecraft must withstand intense solar flares, radiation and temperature swings from hundreds of degrees below zero to hundreds of degrees above zero, engineers have developed innovative solutions to power some of the most remote and isolated space missions. So how do engineers power missions in the outer reaches of our solar system and beyond? The solution is technology developed in the 1960s based on scientific principles discovered two centuries ago: radioisotope thermoelectric generators, or RTGs. RTGs are essentially nuclear-powered batteries. But unlike the AAA batteries in your TV remote, RTGs can provide power for decades while hundreds of millions to billions of miles from Earth.
Nuclear power
Radioisotope thermoelectric generators do not rely on chemical reactions like the batteries in your phone. Instead, they rely on the radioactive decay of elements to produce heat and eventually electricity. While this concept sounds similar to that of a nuclear power plant, RTGs work on a different principle. Most RTGs are built using plutonium-238 as their source of energy, which is not usable for nuclear power plants since it does not sustain fission reactions. Instead, plutonium-238 is an unstable element that will undergo radioactive decay. Radioactive decay, or nuclear decay, happens when an unstable atomic nucleus spontaneously and randomly emits particles and energy to reach a more stable configuration. This process often causes the element to change into another element, since the nucleus can lose protons.Plutonium-238 decays into uranium-234 and emits an alpha particle, made of two protons and two neutrons.NASA When plutonium-238 decays, it emits alpha particles, which consist of two protons and two neutrons. When the plutonium-238, which starts with 94 protons, releases an alpha particle, it loses two protons and turns into uranium-234, which has 92 protons. These alpha particles interact with and transfer energy into the material surrounding the plutonium, which heats up that material. The radioactive decay of plutonium-238 releases enough energy that it can glow red from its own heat, and it is this powerful heat that is the energy source to power an RTG.The nuclear heat source for the Mars Curiosity rover is encased in a graphite shell. The fuel glows red hot because of the radioactive decay of plutonium-238.Idaho National Laboratory, CC BY
Heat as power
Radioisotope thermoelectric generators can turn heat into electricity using a principle called the Seebeck effect, discovered by German scientist Thomas Seebeck in 1821. As an added benefit, the heat from some types of RTGs can help keep electronics and the other components of a deep-space mission warm and working well. In its basic form, the Seebeck effect describes how two wires of different conducting materials joined in a loop produce a current in that loop when exposed to a temperature difference.The Seeback effect is the principle behind RTGs. Devices that use this principle are called thermoelectric couples, or thermocouples. These thermocouples allow RTGs to produce electricity from the difference in temperature created by the heat of plutonium-238 decay and the frigid cold of space.
Radioisotope thermoelectric generator design
In a basic radioisotope thermoelectric generator, you have a container of plutonium-238, stored in the form of plutonium-dioxide, often in a solid ceramic state that provides extra safety in the event of an accident. The plutonium material is surrounded by a protective layer of foil insulation to which a large array of thermocouples is attached. The whole assembly is inside a protective aluminum casing.An RTG has decaying material in its core, which generates heat that it converts to electricity.U.S. Department of Energy The interior of the RTG and one side of the thermocouples is kept hot – close to 1,000 degrees Fahrenheit (538 degrees Celsius) – while the outside of the RTG and the other side of the thermocouples are exposed to space. This outside, space-facing layer can be as cold as a few hundred degrees Fahrenheit below zero. This strong temperature difference allows an RTG to turn the heat from radioactive decay into electricity. That electricity powers all kinds of spacecraft, from communications systems to science instruments to rovers on Mars, including five current NASA missions. But don’t get too excited about buying an RTG for your house. With the current technology, they can produce only a few hundred watts of power. That may be enough to power a standard laptop, but not enough to play video games with a powerful GPU. For deep-space missions, however, those couple hundred watts are more than enough. The real benefit of RTGs is their ability to provide predictable, consistent power. The radioactive decay of plutonium is constant – every second of every day for decades. Over the course of about 90 years, only half the plutonium in an RTG will have decayed away. An RTG requires no moving parts to generate electricity, which makes them much less likely to break down or stop working. Additionally, they have an excellent safety record, and they’re designed to survive their normal use and also be safe in the event of an accident.
RTGs in action
RTGs have been key to the success of many of NASA’s solar system and deep-space missions. The Mars Curiosity and Perseverance rovers and the New Horizons spacecraft that visited Pluto in 2015 have all used RTGs. New Horizons is traveling out of the solar system, where its RTGs will provide power where solar panels could not. However, no missions capture the power of RTGs quite like the Voyager missions. NASA launched the twin spacecraft Voyager 1 and Voyager 2 in 1977 to take a tour of the outer solar system and then journey beyond it.The RTGs on the Voyager probes have allowed the spacecraft to stay powered up while they collect data.NASA/JPL-Caltech Each craft was equipped with three RTGs, providing a total of 470 watts of power at launch. It has been almost 50 years since the launch of the Voyager probes, and both are still active science missions, collecting and sending data back to Earth. Voyager 1 and Voyager 2 are about 15.5 billion miles and 13 billion miles (nearly 25 billion kilometers and 21 billion kilometers) from the Earth, respectively, making them the most distant human-made objects ever. Even at these extreme distances, their RTGs are still providing them consistent power. These spacecraft are a testament to the ingenuity of the engineers who first designed RTGs in the early 1960s. Benjamin Roulston, Assistant Professor of Physics, Clarkson University This article is republished from The Conversation under a Creative Commons license. Read the original article.
Former President Barack Obama recently sparked headlines, social media debates, and a fresh wave of UFO chatter after a brief remark during a podcast interview. The comment quickly ricocheted across news outlets, with many asking: Did Obama just confirm aliens exist? And just as quickly, Donald Trump weighed in.
Let’s unpack what was actually said — and what it means.
🎙️ The Comment That Ignited the Conversation
During a rapid-fire question segment on a podcast hosted by Brian Tyler Cohen, Obama was asked directly:
“Are aliens real?”
Obama’s response:
“They’re real, but I haven’t seen them.”
That short answer fueled immediate speculation. Clips spread online, often stripped of context, with some interpreting the statement as a bombshell confirmation of extraterrestrial life.
🧠 What Obama Meant
Soon after the comment gained traction, Obama clarified his meaning.
His explanation aligned with a position he’s expressed before:
✔ He was referring to the statistical likelihood of life elsewhere in the universe
✔ He was not claiming evidence of alien visitation
✔ He emphasized that during his presidency he saw no proof of extraterrestrial contact
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In other words:
Obama was speaking philosophically and scientifically — not revealing classified information.
This interpretation matches mainstream scientific thinking: given the size of the universe, life beyond Earth is plausible, but confirmed evidence remains elusive.
🛸 Why the Comment Resonated
The remark landed in a cultural moment where:
• Interest in UAPs (Unidentified Aerial Phenomena) is high
• Government transparency around UFO reports has increased
• Space exploration discoveries (exoplanets, water worlds) dominate science news
Even a casual statement from a former president can ignite intense discussion.
🇺🇸 Trump’s Reaction
Former (and current political figure) Donald Trump responded critically.
Trump characterized Obama’s comment as:
• A “mistake”
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• Potentially involving “classified information”
He also reiterated his own stance:
He does not know whether aliens are real.
Trump pivoted the conversation toward disclosure, suggesting he would support or consider declassifying UFO/UAP-related files — a theme that has periodically surfaced in political rhetoric.
⚖️ Politics vs Interpretation
Trump’s reaction highlights how statements about extraterrestrial life often become political flashpoints, even when the original comment is speculative or philosophical.
Key distinction:
Obama’s Clarification
Public Interpretation
Life elsewhere is likely
“Obama confirmed aliens”
No evidence of contact
“Government disclosure”
🔬 The Scientific Reality
Organizations like NASA and the broader research community maintain:
✅ Life beyond Earth → statistically plausible
❓ Intelligent civilizations → unknown
❌ Confirmed alien contact → no verified evidence
Investigations into UAPs consistently conclude:
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• Most sightings have conventional explanations
• Some remain unresolved due to limited data
• None confirmed as extraterrestrial craft
🌌 Why These Stories Keep Captivating Us
Conversations about aliens sit at the intersection of:
✨ Science
🧠 Curiosity
🛸 Mystery
🎭 Pop culture
🏛️ Politics
When a former president comments, the intrigue multiplies.
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📌 Bottom Line
Did Obama say aliens are real?
Yes — but in the sense that life elsewhere in the universe is likely, not that aliens are visiting Earth.
Did he claim evidence?
No.
Trump’s response?
Critical, skeptical, and framed around classification and disclosure.
If you’re fascinated by this topic, you might also enjoy exploring:
• How scientists search for alien life
• What counts as real “evidence”
• Why UFO sightings are so often misinterpreted
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Want me to craft a follow-up article like “How Close Are We to Discovering Alien Life?” 🚀👽
Dive into “The Knowledge,” where curiosity meets clarity. This playlist, in collaboration with STMDailyNews.com, is designed for viewers who value historical accuracy and insightful learning. Our short videos, ranging from 30 seconds to a minute and a half, make complex subjects easy to grasp in no time. Covering everything from historical events to contemporary processes and entertainment, “The Knowledge” bridges the past with the present. In a world where information is abundant yet often misused, our series aims to guide you through the noise, preserving vital knowledge and truths that shape our lives today. Perfect for curious minds eager to discover the ‘why’ and ‘how’ of everything around us. Subscribe and join in as we explore the facts that matter. https://stmdailynews.com/the-knowledge/
Rod: A creative force, blending words, images, and flavors. Blogger, writer, filmmaker, and photographer. Cooking enthusiast with a sci-fi vision. Passionate about his upcoming series and dedicated to TNC Network. Partnered with Rebecca Washington for a shared journey of love and art. View all posts
Valerie Thomas is a true pioneer in the world of science and technology. A NASA engineer and physicist, she is best known for inventing the illusion transmitter, a groundbreaking device that creates 3D images using concave mirrors. This invention laid the foundation for modern 3D imaging and virtual reality technologies.
Beyond her inventions, Thomas broke barriers as an African American woman in STEM, mentoring countless young scientists and advocating for diversity in science and engineering. Her work at NASA’s Goddard Space Flight Center helped advance satellite technology and data visualization, making her contributions both innovative and enduring.
In our latest short video, we highlight Valerie Thomas’ remarkable journey—from her early passion for science to her groundbreaking work at NASA. Watch and be inspired by a true STEM pioneer whose legacy continues to shape the future of space and technology.
Dive into “The Knowledge,” where curiosity meets clarity. This playlist, in collaboration with STMDailyNews.com, is designed for viewers who value historical accuracy and insightful learning. Our short videos, ranging from 30 seconds to a minute and a half, make complex subjects easy to grasp in no time. Covering everything from historical events to contemporary processes and entertainment, “The Knowledge” bridges the past with the present. In a world where information is abundant yet often misused, our series aims to guide you through the noise, preserving vital knowledge and truths that shape our lives today. Perfect for curious minds eager to discover the ‘why’ and ‘how’ of everything around us. Subscribe and join in as we explore the facts that matter. https://stmdailynews.com/the-knowledge/
A Short-Form Series from The Knowledge by STM Daily News
Every Friday, STM Daily News shines a light on brilliant minds history overlooked.
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Forgotten Genius Fridays is a weekly collection of short videos and articles dedicated to inventors, innovators, scientists, and creators whose impact changed the world—but whose names were often left out of the textbooks.
From life-saving inventions and cultural breakthroughs to game-changing ideas buried by bias, our series digs up the truth behind the minds that mattered.
Each episode of The Knowledge runs 30–90 seconds, designed for curious minds on the go—perfect for YouTube Shorts, TikTok, Reels, and quick reads.
Because remembering these stories isn’t just about the past—it’s about restoring credit where it’s long overdue.
Rod: A creative force, blending words, images, and flavors. Blogger, writer, filmmaker, and photographer. Cooking enthusiast with a sci-fi vision. Passionate about his upcoming series and dedicated to TNC Network. Partnered with Rebecca Washington for a shared journey of love and art. View all posts
Beneath the Waves: The Global Push to Build Undersea Railways
Undersea railways are transforming transportation, turning oceans from barriers into gateways. Proven by tunnels like the Channel and Seikan, these innovations offer cleaner, reliable connections for passengers and freight. Ongoing projects in China and Europe, alongside future proposals, signal a new era of global mobility beneath the waves.
Trains beneath the ocean are no longer science fiction—they’re already in operation.
For most of modern history, oceans have acted as natural barriers—dividing nations, slowing trade, and shaping how cities grow. But beneath the waves, a quiet transportation revolution is underway. Infrastructure once limited by geography is now being reimagined through undersea railways.
Undersea rail tunnels—like the Channel Tunnel and Japan’s Seikan Tunnel—proved decades ago that trains could reliably travel beneath the ocean floor. Today, new projects are expanding that vision even further.
Around the world, engineers and governments are investing in undersea railways—tunnels that allow high-speed trains to travel beneath oceans and seas. Once considered science fiction, these projects are now operational, under construction, or actively being planned.
Undersea Rail Is Already a Reality
Japan’s Seikan Tunnel and the Channel Tunnel between the United Kingdom and France proved decades ago that undersea railways are not only possible, but reliable. These tunnels carry passengers and freight beneath the sea every day, reshaping regional connectivity.
Undersea railways are cleaner than short-haul flights, more resilient than bridges, and capable of lasting more than a century. As climate pressures and congestion increase, rail beneath the sea is emerging as a practical solution for future mobility.
What’s Being Built Right Now
China is currently constructing the Jintang Undersea Railway Tunnel as part of the Ningbo–Zhoushan high-speed rail line, while Europe’s Fehmarnbelt Fixed Link will soon connect Denmark and Germany beneath the Baltic Sea. These projects highlight how transportation and technology are converging to solve modern mobility challenges.
