We Searched the Universe for a Safer Planet Than Earth
The short answer
We didn't find one. We checked Earth's core, orbit, Mars, Proxima b, near light speed, the galaxy and the far future, and each failed for a real reason. The safest place we found is Earth. Its deadline is about a billion years away, when a Sun that brightens about 10% every billion years dries up the oceans.
What protects us right now is in the film's first shot. The Sun's wind bends around the planet, pushed aside by a magnetic field made in Earth's churning iron core. Gravity holds the air down. The two share the credit.
The real move out date
The Sun won't start swelling into a red giant for about 5 billion years. About 7.6 billion years from now, it swallows Mercury and Venus. Whether it swallows Earth is still argued: a 2008 study says Earth can't escape, and newer work suggests it may survive.
That isn't the deadline that matters. Each second, the Sun turns about 600 million metric tons of hydrogen into helium. Four hydrogen atoms make one helium atom, so the core holds fewer and fewer particles. It shrinks and heats up, and the Sun shines about 10% brighter every billion years.
In roughly a billion years, that extra sunlight dries the oceans up. The water evaporates and escapes to space as hydrogen and oxygen. True boiling, a runaway greenhouse, comes later, in models 3 to 4 billion years out. Orbit keeps you at the same distance from the same Sun, and every other planet here gets the same brightening Sun too.
Why every other address failed
Downstairs: Earth's center is 6,371 km (3,959 miles) down, and its solid iron inner core is about as hot as the Sun's surface. Upstairs: staying in orbit means moving sideways at about 17,500 mph, and the thin air up there slowly drags you down. The space station needs regular reboosts.
Next door, Mars has air, but its surface pressure is 6.36 millibars, about 0.63% of ours. A liquid set out there boils and freezes at once. Mars is about half as wide as Earth, and smaller bodies cool faster. Its crust holds magnetic traces from about 4 billion years ago, before its field faded. Solar wind and radiation then stripped most of its air over billions of years.
The next star, Proxima Centauri, is about 4.25 light years away. Its planet Proxima b has at least 1.055 Earth masses and orbits where water could stay liquid. But red dwarfs flare often. Proxima b gets about 250 times more X rays than Earth, and its air may be gone. In March 2016 one flare made the star about 68 times brighter, just visible to the naked eye at dark sites. At Voyager 1's 17.0 km/s (about 38,000 mph), the trip lasts about 75,000 years.
Going faster hits the light speed limit. Near it, each extra nine (99%, then 99.9%, then 99.99%) costs more energy than all the earlier ones together. At 99.5% of light speed, your clock runs about 10 times slower than clocks at home. Atomic clocks flown on airliners in 1971 measured the effect, off by 59 and 273 billionths of a second. A round trip to Proxima at 99.5% lasts about 8.5 years at home and under a year on board.
Nothing holds still, either. The Sun needs about 230 million years to circle the galaxy. One lap ago, the first dinosaurs were just appearing. The Milky Way is being dragged through space at about 600 km/s (about 1.34 million mph). Part of the pull comes from the Great Attractor, a crowd of galaxies hidden behind our galaxy's band of dust and stars. That crowd is tied to a bigger one farther out, the Shapley supercluster. But the space between them stretches faster than gravity can close the gap, so we never arrive.
The far future is no refuge. Everything anyone has seen adds up to under 5% of the universe. Dark matter and dark energy make up the rest. In about 100 billion years, every galaxy beyond our own merged Local Group will have slipped out of sight.
What keeps us safe now
Under our feet, liquid iron in the outer core keeps churning, and that moving iron makes Earth a magnet. Its field reaches far into space and turns aside the Sun's wind, a constant stream of charged particles. The wind in turn squeezes the field into a teardrop shape. Some energy is steered down field lines near the poles, where oxygen glows green and red. That is the aurora, the green flicker in the film's first shot.
The film is careful about one point. NASA says the field shields our air from erosion, but scientists still debate how much it matters. Venus has no global field and keeps a very thick atmosphere. So the film splits the credit. Gravity holds the air down, and the field keeps the wind off it.
The deadline is real, but it is far away. The first powered airplane flew in 1903, and astronauts landed on the Moon in 1969: 66 years apart. A billion years is about 15 million times that.
Key numbers
| What | Number | Source |
|---|---|---|
| How fast the Sun is brightening | about 10% every billion years | Jillian Scudder, The Conversation |
| Time until the extra sunlight dries the oceans | roughly 1 billion years | Jillian Scudder, The Conversation |
| When the Sun starts swelling, and when it swallows Mercury and Venus | starts in about 5 billion years; swallows them about 7.6 billion years from now | Wikipedia, Future of Earth |
| Distance to Earth's center | 6,371 km (3,959 miles) | NASA NSSDC, Earth fact sheet |
| Air pressure at the surface of Mars | 6.36 millibars, about 0.63% of Earth's 1,013 millibars | NASA NSSDC, Mars fact sheet |
| Distance to Proxima Centauri | about 4.25 light years (40,208,000,000,000 km) | NASA Imagine the Universe, nearest star |
| X rays reaching Proxima b | about 250 times what Earth gets | Ribas et al. 2016, Astronomy & Astrophysics |
| Trip to Proxima at Voyager 1's speed of 17.0 km/s (about 38,000 mph) | about 75,000 years | Our arithmetic from NASA Imagine the Universe, nearest star |
| Time at home for each year on board at 99.5% of light speed | about 10 years (factor 10.01) | Our arithmetic from OpenStax University Physics Volume 3, Time dilation |
| Round trip to Proxima at 99.5% of light speed | about 8.5 years at home, about 0.85 years on board | Our arithmetic from OpenStax University Physics Volume 3, Time dilation |
| The Milky Way's speed through space | about 600 km/s (about 1.34 million mph) | BBC Sky at Night, The Great Attractor |
| One lap of the Sun around the galaxy | about 230 million years | Space.com, Milky Way facts |
What the film simplifies
- The rocket's round trip to Proxima b in under a year of its own time assumes cruising at 99.5% of light speed the whole way. Speeding up and slowing down at a survivable rate would add years on board. The film never claims a real ship could do it.
- The swollen red Sun leaning over a blue Earth is a cartoon. By the time the Sun is a red giant, Earth's oceans are long gone, as the film itself says. Gravity, Proxima and the air also talk.
- The film never says Earth's magnetic field is the reason we still have air. Scientists debate that, so the ending gives gravity and the field shared credit.
- 'Dust can't stop radio waves or X rays' is close but not exact. Radio passes almost untouched, and X rays get through far better than visible light, but not perfectly.
- 'Thirteen tons of fuel a second' counts all the propellant a Saturn V's five F1 engines burn at liftoff. Most of it is liquid oxygen, not fuel in the everyday sense.
- 'Its core stopped churning' means the churning that made Mars's magnetic field stopped about 4 billion years ago (estimates run from about 4.1 to 3.7 billion). Mars's core isn't frozen: its outer core is still liquid.
For teachers
Runtime 11 minutes · Topics: The Sun's future, Earth's magnetic field, Mars and Proxima b, Light speed and time · Full script below
Ask your class
The Sun won't start swelling for about 5 billion years. Why does Earth's deadline come after only about 1 billion?
Answer
The Sun gets about 10% brighter every billion years. In roughly a billion years, the extra sunlight dries the oceans up, long before the Sun swells.
At 99.5% of light speed, about 10 years pass at home for every year on board. Proxima is about 4.25 light years away. Roughly how long does a round trip last at home, and on board?
Answer
Each way lasts about 4.25 ÷ 0.995, or roughly 4.3 years as measured at home, so about 8.5 years for the round trip. On board, clocks run 10 times slower, so the trip lasts under a year (about 0.85 years).
Mars once had thicker air and lakes. According to the film, what happened to them?
Answer
Mars is small, so it cooled faster. Its core stopped churning about 4 billion years ago and its magnetic field faded. Over billions of years, solar wind and radiation stripped most of its air, and the lakes dried up or froze.
The script
Read the script
Rocket: Nobody's home!
Host: That's the Sun. It owns the whole street. And it wants you out.
Host: About five billion years from now, it starts swelling. Later, it swallows Mercury. Then Venus.
Host: Earth? Even astronomers can't agree.
Lil Sat: Evicted?! Where do we go? Where's the safest place in the whole universe?!
Rocket: Relax, Sat! I can take you anywhere. Everybody moved by lunch!
Host: So we went looking. Downstairs. Upstairs. Next door. The next star. The whole galaxy. The end of time.
Host: Each one was worse than the last.
Host: But something in the very first shot is keeping you safe. Right now. Find it.
Rocket: The first shot? That was me holding the door!
Rocket: Moving day!
Host: First, the fine print.
Host: Wait. The Sun won't start swelling for about five billion years. So why does the notice say one?
Host: Because the Sun doesn't need to swallow Earth to get rid of us.
Host: It only has to get brighter.
Host: Every billion years, it shines about ten percent brighter.
Rocket: Ten percent? Pfft! That's a tan!
Host: That's plenty. In roughly a billion years, the extra sunlight dries the oceans up.
Host: That's the real move out date.
Host: Why brighter? Because it never stops eating.
Host: Every single second, the Sun uses up six hundred million tons.
Rocket: Ha! I burn thirteen!
Lil Sat: Thirteen million?
Rocket: ...Thirteen.
Lil Sat: So where do we hide?!
Rocket: Easy! When it's too hot upstairs, you go to the basement!
Rocket: Basement! Cool and quiet, and no landlord! Hop in!
Host: That's as deep as anyone has ever dug.
Host: The middle of the Earth? Four thousand miles further.
Rocket: Is there an express?!
Host: Next comes the mantle: solid rock that creeps along at fingernail speed.
Host: Eighteen hundred miles down, the rock gives way to a sea of liquid iron.
Host: And dead center sits a ball of solid iron the size of Pluto.
Host: It's around ten thousand degrees Fahrenheit. The Sun's surface runs about that hot.
Rocket: We ran from the Sun and found another Sun?!
Host: Up here, that heat would melt iron.
Host: Down there, the whole planet presses on it and keeps it solid.
Gravity: Somebody has to hold it together.
Host: The liquid iron around it never stops churning.
Host: And all that moving iron turns the planet into a magnet.
Host: The Sun blows a wind of tiny charged bits at us, nonstop.
Host: Its field reaches far out into space and shoves that wind aside.
Lil Sat: Ohh! So that's why the green lights...
Rocket: Can I live in a magnet? No! Zero bedrooms! Next!
Host: Too hot to go down. So there's only one way out. Up.
Gravity: Going up? With all that luggage?
Rocket: So how much of me is fuel?
Host: About nine tenths.
Rocket: I'm mostly gas?!
Lil Sat: We noticed.
Mission Control: Tow cable secure. You are go for launch.
Host: It gulps thirteen tons of fuel a second.
Rocket: Told you! Thirteen!
Host: But up isn't the trick. You go sideways, at seventeen and a half thousand miles an hour.
Host: Orbit is falling. You're just going sideways so fast, the ground keeps curving away.
Lil Sat: Welcome to my neighborhood! I go round every ninety minutes.
Lil Sat: I'll blink every lap, so you can always find home.
Rocket: Find home? I'm leaving home! Do we live up here?
Host: Orbit's a hallway, not a home. The thin air up here slowly drags you down.
Host: And it's the same Sun, at the same distance.
Rocket: Then we need a whole new planet. And there's one right next door!
Rocket: Next door! Loads of room, nobody home! Cheers!
Rocket: Is it supposed to do both?!
Host: On Mars, it does. The air pressure there is less than a hundredth of ours.
Rocket: Who stole the air?!
Host: Long ago, Mars had thicker air, and rivers running into lakes.
Host: Then the air went. The lakes dried up or froze.
Host: Mars had a heart like ours once. Churning iron, deep down.
Rocket: ...The zero bedroom magnet?
Host: But Mars is half as wide as Earth, and small things cool faster.
Host: About four billion years ago, its core stopped churning. And the shield switched off.
Rocket: Hang on, buddy! I can fix this! Clear!
Host: Nobody knows how to restart a planet's heart.
Host: No shield, so the wind hit the air head on.
Host: Bit by bit, over billions of years, it tore the sky off.
Rocket: I almost moved everybody in here.
Lil Sat: Is our heart okay?!
Host: Still churning.
Lil Sat: Wait! Then the green lights are...
Rocket: Not now, Sat! Every planet here gets the same Sun. So we switch stars!
Host: The next star over is Proxima, about four point two light years out. And it has a planet.
Host: It weighs at least as much as Earth.
Host: And it sits where water could stay liquid. Maybe oceans.
Rocket: Oceans?! Hitch the crate!
Host: Its star is a red dwarf. Too dim to see from Earth without a telescope.
Rocket: Aww! It's a night light!
Proxima: Night light?!
Host: In 2016, one of her flares was so bright that, for a few minutes, sharp eyes could have spotted her without a telescope.
Host: Red dwarfs flare a lot. Proxima b gets hundreds of times more X rays than we do.
Host: Any air it had may be gone.
Rocket: Okay, she's got a temper. But oceans!
Host: Then the drive. Voyager one is heading out at about thirty eight thousand miles an hour.
Host: At that speed, Proxima b is about seventy five thousand years away.
Rocket: Seventy five thousand years?! I said lunch!
Rocket: Forget slow! I'll go faster. As fast as light!
Host: Then you're about to meet the strictest rule in the universe.
Host: The universe has a speed limit. Light.
Host: A beam could circle Earth seven and a half times in one second.
Host: Near the limit, each new nine on the end eats more energy than all the nines before it.
Host: Light speed itself? Infinite energy. Light gets there because it weighs nothing. You don't.
Rocket: Fine! Close is good! Ninety nine and a half, one quick trip!
Host: Say you found the fuel. At that speed, your clock runs slow.
Host: Every year on board, about ten pass at home.
Host: We've measured it, with clocks flown on airliners.
Lil Sat: Your year. My ten.
Rocket: Ten years?! Sat, I can't wait ten minutes!
Lil Sat: Go. I'll keep blinking. Just come back.
Lil Sat: Oh! And the green lights! They're...
Rocket: Proxima b! Open up, I've got a whole planet coming!
Proxima: Visiting hours are over!
Rocket: Which one is home?! Which one?!
Host: That one. The little yellow one. From here, our Sun is just another star.
Rocket: That was quick! Why is there a scarf around the planet?
Lil Sat: I started it when you left.
Host: The round trip took the rocket less than a year. Back home, almost nine went by.
Rocket: Nine years. I missed nine years.
Rocket: I can take you anywhere. I just can't ever bring you back to the same time.
Rocket: So the next place has to be forever. Somewhere that never moves.
Host: Bad news: nothing out here holds still.
Host: Even the Sun is circling the galaxy. One lap takes about 230 million years. Last time we were here, the first dinosaurs were just showing up.
Host: Our whole galaxy is being dragged through space at more than a million miles an hour.
Rocket: Dragged?! Who's pulling my house?!
Rocket: Nobody moves till we know who's pulling.
Host: Whatever's pulling hides behind our own galaxy's band of dust and stars.
Host: Dust can't stop radio waves or X rays.
Host: Behind it waits a huge crowd of galaxies: the Great Attractor.
Host: In the nineteen eighties, astronomers found hundreds of nearby galaxies drifting one way, like boats in a current.
Rocket: We're being dragged into a pile up?!
Gravity: Somebody has to pull.
Host: Except that crowd is hitched to an even bigger crowd, farther out.
Lil Sat: Then who's pulling THEM?!
Rocket: Are we there yet?!
Host: No. And we never will be.
Host: The space in between stretches faster than gravity can reel us in.
Gravity: It's... getting... longer?!
Host: Something is stretching the gaps between them. And out here, it's stronger than all of them.
Host: Add up every star, planet and person anyone has ever seen.
Host: It comes to under five percent of what's out there.
Rocket: ...Check under the couch.
Host: Nobody has ever seen the rest. Part of it holds our spinning galaxy together. That's dark matter.
Gravity: I have help. You'll never see them.
Host: The rest of it shoves the galaxies apart. Space itself keeps stretching, and the stretch is speeding up.
Host: Nobody knows why. That's dark energy.
Host: The farthest galaxies already move away faster than light.
Rocket: Wait. You said nothing outruns light!
Host: Nobody's breaking it. It's the space between us that's growing.
Rocket: Then I'll check the end of time. Something has to last!
Host: Picture our sky a hundred billion years from now.
Host: One by one, every other galaxy slips out of sight. Until there's one left.
Host: Ours.
Lil Sat: So where's safe?
Rocket: I don't know.
Rocket: Sat. The green lights. What were you trying to tell me?
Lil Sat: You never let me finish! The green lights mean our shield is on.
Lil Sat: It turns the Sun's wind away from us. Right now!
Lil Sat: Mars lost its shield, and the wind took its sky.
Rocket: The zero bedroom magnet. It's been working this whole time!
Gravity: Grab on.
Rocket: There's the porch light! Keep blinking, Sat!
Host: Getting home means shedding seventeen and a half thousand miles an hour.
Host: Fire the engine against the way you're flying, and the next lap dips into the air.
The Air: You again? Wipe your feet.
Host: The air in front can't move aside fast enough.
Host: Squeezed into a wall, it heats to thousands of degrees.
Host: A sharp nose takes the worst of the heat. So capsules come in blunt.
Rocket: Blunt?! But my fins! ...Fine. Take them!
Host: That glowing air is plasma now. No radio call gets in or out.
Lil Sat: Rocket? Say something! Anything! Even a brag!
Rocket: ...Did everybody see that entrance?
Gravity: Somebody has to bring you home.
Rocket: Liquid! It just stays liquid!
Rocket: Nine years of scarf. And you kept knitting.
Lil Sat: Somebody had to stay home.
Host: Remember the very first shot?
Host: The Sun's wind was blowing straight at us. And it bent, right around the planet.
Host: That flicker of green at the pole? The shield at work, steering a little of that wind down.
Host: Made by an ocean of churning iron, eighteen hundred miles down.
Lil Sat: I said green lights! Three times!
Rocket: Tell me again. I'll be quiet.
Host: Of every address we checked, the one that worked was the one we tried to leave.
Gravity: I keep the air from drifting off. The heart keeps the wind off it. Teamwork.
Rocket: So we stay?
Host: For now. The oceans have about a billion years left.
Rocket: A billion? Pfft. We got from a wooden plane to the Moon in...
Host: Sixty six years.
Host: And a billion years is fifteen million times that.
Lil Sat: I'll need more yarn.
Rocket: Okay, Sun. Notice received.
Rocket: We'll be ready.
Host: The safest place we've found in the whole universe. And you're already home.
Sources
- When it starts to die, the Sun will expand into a red giant and engulf Mercury and Venus, and possibly Earth; its surface is about 10,000 °F (5,500 °C).NASA, Sun facts
- Earth will not be able to escape engulfment when the Sun is a red giant, about 7.59 billion years from now.Schröder & Smith 2008, Monthly Notices of the RAS
- The Sun's main sequence life ends in about 5 billion years and it becomes a red giant; the oceans are lost in about 1 to 1.5 billion years; a runaway greenhouse comes in about 3 to 4 billion; Mercury and Venus are engulfed about 7.6 billion years from now; Earth's engulfment remains uncertain.Wikipedia, Future of Earth
- Earth may survive the Sun's red giant phase.Space.com, Earth may survive the Sun's death
- The Sun brightens about 10% every billion years; in about a billion years it gets hot enough to lose the oceans, with water escaping as hydrogen and oxygen.Jillian Scudder, The Conversation
- Fewer atoms in the core mean it shrinks and heats, so the Sun shines brighter.Phil Plait, Scientific American, 2026
- The Sun fuses hydrogen into helium in its core.EUROfusion, Fusion on the Sun
- Every second, the Sun turns about 600 million tonnes of hydrogen into helium. Every second, the Sun turns about 600 million metric tons of hydrogen into helium.ITER, What is fusion
- The inner core is a solid iron and nickel sphere with a radius of 1,221 km, up to 9,800 °F; the molten core gives rise to the magnetic field; the solar wind distorts the field into a teardrop shape.NASA, Earth facts
- Earth's radius is 6,371 km (3,959 miles).NASA NSSDC, Earth fact sheet
- The mantle is solid rock that flows at about the rate fingernails grow.USGS, Are tectonic plates floating on magma?
- Moving liquid iron in the outer core generates Earth's magnetic field.USGS, How does the Earth's core generate a magnetic field?
- Earth's magnetosphere shields us from the solar wind and from erosion of the atmosphere.NASA, Earth's magnetosphere
- Earth's magnetosphere deflects the solar wind.NOAA Space Weather Prediction Center, Earth's magnetosphere
- Earth's magnetic field guides electrons so the aurora forms two ovals around the magnetic poles.NOAA Space Weather Prediction Center, Aurora
- Energy and particles travel down field lines near the poles; oxygen gives off green and red light.NASA Space Place, What is an aurora?
- The solar wind is a constant stream of charged particles.NASA, What is the solar wind?
- Each F1 engine's turbopump moved 42,500 gallons of propellant a minute (about 13 tons a second for five engines).Smithsonian National Air and Space Museum, F1 engine
- The space station orbits Earth about every 90 minutes at about five miles per second.NASA, Space station facts and figures
- The station's altitude drops over time due to atmospheric drag; periodic reboosts correct it.NASA JSC, Space Station Orbit Tutorial
- Mars's surface pressure is 6.36 mb against Earth's 1,013 mb; its radius is 0.532 of Earth's.NASA NSSDC, Mars fact sheet
- Liquid water released on Mars will simultaneously freeze and boil.NASA Astrobiology, Liquid water on Mars
- Mars is about half Earth's size; its crust keeps traces of a magnetic field from 4 billion years ago.NASA, Mars facts
- Mars had a thick atmosphere 4 billion years ago; the field made by its core all but disappeared.NASA MAVEN blog, Martian magnetic fields, 2013
- Solar wind and radiation stripped most of Mars's atmosphere over billions of years.NASA, MAVEN reveals most of Mars' atmosphere was lost to space
- Mars has a liquid iron core.NASA JPL, Mars has a liquid iron core, 2023
- Proxima b orbits the nearest star in its habitable zone.ESO, Anglada-Escudé et al. 2016 (eso1629)
- Proxima b has a minimum mass of 1.055 Earth masses.NASA Exoplanet Catalog, Proxima Centauri b
- Proxima is 40,208,000,000,000 km (4.25 light years) away; over 73,000 years at Voyager's speed.NASA Imagine the Universe, nearest star
- An Earth like atmosphere may not survive Proxima b's orbit.NASA Goddard, Garcia-Sage et al. 2017
- Proxima b receives about 250 times more X rays than Earth.Ribas et al. 2016, Astronomy & Astrophysics
- A March 2016 superflare made Proxima about 68 times brighter, just visible to the naked eye at dark sites.Howard et al. 2018, The Astrophysical Journal Letters
- Voyager 1 travels at about 38,000 mph (17.0 km/s).NASA, Voyager 1
- The speed of light in vacuum is a defined constant.NIST, SP 330
- Light could circle Earth about 7.5 times in one second.NASA Glenn, How fast is the speed of light?
- Kinetic energy grows without limit as speed nears light speed.OpenStax College Physics 2e, Relativistic energy
- Moving clocks run slow by the time dilation factor gamma, which grows as speed nears light speed (the formula behind the factor 10.01 at 99.5%).OpenStax University Physics Volume 3, Time dilation
- At about 99.5% of light speed, a traveler celebrates only five birthdays on the voyage while about 50 years pass at home.NASA JPL, Time Travel podcast
- Atomic clocks flown around the world on airliners measured time dilation.Hafele & Keating 1972, Science
- The clocks flown in October 1971 lost 59 billionths of a second eastward and gained 273 westward.HyperPhysics, Airplane clock experiment
- The Sun circles the Milky Way about once every 230 million years.Space.com, Milky Way facts
- One galactic year ago was the Late Triassic, when the first dinosaurs appeared.Live Science, How many times has the Sun traveled around the Milky Way
- The Milky Way and nearby galaxies move at around 600 km/s toward a point beyond the Milky Way's plane, the Great Attractor; we'll never actually get there.BBC Sky at Night, The Great Attractor
- The Great Attractor region hides behind the Milky Way's dust.ESA/Hubble, Picture of the Week potw1302a
- The Shapley supercluster contributes to the Local Group's motion.Kocevski & Ebeling 2006
- Our galaxy belongs to the Laniakea supercluster.Tully et al. 2014, Nature (Laniakea)
- Everything ever observed adds up to less than 5% of the universe.NASA, What is dark energy?
- Dark matter makes up about 27% of the universe.NASA, Dark matter
- Dark matter does not emit, absorb or reflect light.CERN, Dark matter
- The expansion of the universe is accelerating.Nobel Prize in Physics 2011
- The farthest galaxies recede faster than light because space between us is expanding.Davis & Lineweaver 2004
- In about 100 billion years, the nearby galaxies will have merged with the Milky Way and all other galaxies will have disappeared from view.Krauss & Scherrer, Scientific American, 2008
- A deorbit burn starts a spacecraft's return.NASA Commercial Crew blog, 2024
- Orion's heat shield faces temperatures nearing 5,000 °F and burns away to carry heat off.NASA, Orion heat shield
- Plasma around a reentering craft blocks radio signals.ESA, Mitigation of RF blackout
- H. Julian Allen showed blunt bodies survive reentry heating better than sharp ones.NASA Ames History, H. Julian Allen
- The first powered, controlled airplane flight was on December 17, 1903.Smithsonian National Air and Space Museum, 1903 Wright Flyer
- Apollo 11 landed on the Moon on July 20, 1969.NASA, Apollo 11