PBS Space Time
(02/11/2015–04/02/2026)15 min
Source: unknown
Episodes
S2015E01
What Planet is Super Mario World?
S2015E02
Is It Irrational to Believe in Aliens?
S2015E03
How Do You Measure the Size of the Universe?
S2015E04
Should We Colonize Venus Instead of Mars?
S2015E05
What Will Destroy Planet Earth?
S2015E06
Can a Starfox Barrel Roll Work in Space?
S2015E07
Cosmic Microwave Background Explained
S2015E08
Is the Moon in Majora's Mask a Black Hole?
S2015E09
Could You Fart Your Way to the Moon?
S2015E10
How to Weigh a Fart
S2015E11
Could NASA Start the Zombie Apocalypse?
S2015E12
Are Space and Time an Illusion?
S2015E13
What's the Most Realistic Artificial Gravity in Sci-Fi?
S2015E14
Should the First Mars Mission Be All Women?
S2015E15
9 NASA Technologies Shaping YOUR Future
S2015E16
The Real Meaning of E=mc²
S2015E17
Habitable Exoplanets Debunked!
S2015E18
Is Gravity an Illusion?
S2015E19
Challenge: What Happens to a Helium Balloon in Freefall?
S2015E20
How to Signal Aliens
S2015E21
The Calendar, Australia & White Christmas
S2015E22
Can a Circle Be a Straight Line?
S2015E23
Curvature Demonstrated + Comments
S2015E24
The Leap Second Explained
S2015E25
Can You Trust Your Eyes in Spacetime?
S2015E26
SPECIAL ANNOUNCEMENT + Flat Spacetime Geometry Comments
S2015E27
General Relativity & Curved Spacetime Explained!
S2015E28
What Physics Teachers Get Wrong About Tides!
S2015E29
Challenge: Which Particle Wins This Race?
S2015E30
Do Events Inside Black Holes Happen?
S2015E31
Watch THIS! (New Host + Challenge Winners)
S2015E32
Does Dark Matter BREAK Physics?
S2015E33
What Happens at the Edge of the Universe?
S2015E34
The Speed of Light is NOT About Light
S2015E35
5 REAL Possibilities for Interstellar Travel
S2015E36
Have Gravitational Waves Been Discovered?!?
S2015E37
Is the Alcubierre Warp Drive Possible?
S2015E38
Why Haven't We Found Alien Life?
S2015E39
Challenge: Can You Save Earth from a Killer Asteroid?
S2015E40
5 Ways to Stop a Killer Asteroid
S2015E41
100 Years of Relativity + Challenge Winners!
S2015E42
How to Build a Black Hole
S2015E43
The Higgs Mechanism Explained
S2016E01
The True Nature of Matter and Mass
S2016E02
When Time Breaks Down
S2016E03
The Photon Clock Challenge
S2016E04
The Origin of Matter and Time
S2016E05
Will Mars or Venus Kill You First?
S2016E06
LIGO's First Detection of Gravitational Waves!
S2016E07
Planet X Discovered?? + Challenge Winners!
S2016E08
Why the Big Bang Definitely Happened
S2016E09
What's Wrong with the Big Bang Theory?
S2016E10
Cosmic Microwave Background Challenge
S2016E11
Why is the Earth Round and the Milky Way Flat?
S2016E12
How Cosmic Inflation Flattened the Universe
S2016E13
Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners!
S2016E14
We Are Star Stuff
S2016E15
Will the Universe Expand Forever?
S2016E16
Why the Universe Needs Dark Energy
S2016E17
What Does Dark Energy Really Do?
S2016E18
Will Starshot's Insterstellar Journey Succeed?
S2016E19
The Cosmic Conspiracy of Dark Energy Challenge Question
S2016E20
Anti-gravity and the True Nature of Dark Energy
S2016E21
Is an Ice Age Coming?
S2016E22
Is Quantum Tunneling Faster Than Light?
S2016E23
New Fundamental Particle Discovered?? + Challenge Winners!
S2016E24
The Strange Universe of Gravitational Lensing
S2016E25
Planck's Constant and the Origin of Quantum Mechanics
S2016E26
Nuclear Physics Challenge
S2016E27
Juno to Reveal Jupiter's Violent Past
S2016E28
The Future of Gravitational Waves
S2016E29
The Quantum Experiment That Broke Reality
S2016E30
Can We Survive the Destruction of the Earth? ft. Neal Stephenson
S2016E31
How the Quantum Eraser Rewrites the Past
S2016E32
Quantum Eraser Lottery Challenge
S2016E33
Should We Build a Dyson Sphere?
S2016E34
Is There a Fifth Fundamental Force? + Quantum Eraser Answer
S2016E35
Self-Replicating Robots and Galactic Domination
S2016E36
Quantum Entanglement and the Great Bohr-Einstein Debate
S2016E37
Life on Europa?
S2016E38
Are We Alone? Galactic Civilization Challenge
S2016E39
Black Holes from the Dawn of Time
S2016E40
The First Humans on Mars
S2016E41
The Many Worlds of the Quantum Multiverse
S2016E42
Quantum Vortices and Superconductivity + Challenge Answers
S2016E43
Did Dark Energy Just Disappear?
S2016E44
Strange Stars
S2016E45
Pilot Wave Theory and Quantum Realism
S2016E46
What Happens at the Event Horizon?
S2016E47
Escape the Kugelblitz Challenge
S2016E48
Have They Seen Us?
S2017E01
How to See Black Holes + Kugelblitz Challenge Answer
S2017E02
The EM Drive: Fact or Fantasy?
S2017E03
The Phantom Singularity
S2017E04
Why Quasars Are So Awesome
S2017E05
The Geometry of Causality
S2017E06
Telescopes of Tomorrow
S2017E07
The Eye of Sauron Reveals a Forming Solar System!
S2017E08
The Treasures of Trappist-1
S2017E09
The Race to a Habitable Exoplanet - Time Warp Challenge
S2017E10
Time Crystals!
S2017E11
Superluminal Time Travel + Time Warp Challenge Answer
S2017E12
How Time Becomes Space Inside a Black Hole
S2017E13
Telescopes on the Moon
S2017E14
The Oh My God Particle
S2017E15
Are You a Boltzmann Brain?
S2017E16
Are We Living in an Ancestor Simulation?
S2017E17
The Great American Eclipse
S2017E18
Martian Evolution
S2017E19
The Fate of the First Stars
S2017E20
Supervoids vs Colliding Universes!
S2017E21
Anti-Matter and Quantum Relativity
S2017E22
The First Quantum Field Theory
S2017E23
Feynman's Infinite Quantum Paths
S2017E24
Solving the Impossible in Quantum Field Theory
S2017E25
The Real Star Wars
S2017E26
The Secrets of Feynman Diagrams
S2017E27
Dark Flow
S2017E28
The One-Electron Universe
S2017E29
Extraterrestrial Superstorms
S2017E30
First Detection of Life
S2017E31
White Holes
S2017E32
Neutron Stars Collide in New LIGO Signal?
S2017E33
The Future of Space Telescope
S2017E34
Are the Fundamental Constants Changing?
S2017E35
When Quasars Collide STJC
S2017E36
Absolute Cold
S2017E37
The Nature of Nothing
S2017E38
The Missing Mass Mystery
S2017E39
The Vacuum Catastrophe
S2017E40
Zero-Point Energy Demystified
S2017E41
Suicide Space Robots
S2017E42
Citizen Science + Zero-Point Challenge Answer
S2017E43
Understanding the Uncertainty Principle with Quantum Fourier Series
S2017E44
The Origin of Our First Interstellar Visitor
S2017E45
Extinction by Gamma-Ray Burst
S2018E01
What Do Stars Sound Like?
S2018E02
Horizon Radiation
S2018E03
The End of the Habitable Zone
S2018E04
Kronos: Devourer of Worlds
S2018E05
What is Energy?
S2018E06
The Death of the Sun
S2018E07
The Trebuchet Challenge
S2018E08
Should Space Be Privatized?
S2018E09
Hawking Radiation
S2018E10
Scientists Have Detected the First Stars
S2018E11
The Andromeda-Milky Way Collision
S2018E12
The Unruh Effect
S2018E13
Physics of Life
S2018E14
Using Stars to See Gravitational Waves
S2018E15
Black Hole Swarms
S2018E16
The Star at the End of Time
S2018E17
How Gaia Changed Astronomy Forever
S2018E18
Noether's Theorem and the Symmetries of Reality
S2018E19
Why Quantum Information is Never Destroyed
S2018E20
What Survives Inside a Black Hole?
S2018E21
The Black Hole Information Paradox
S2018E22
How Asteroid Mining Will Save Earth
S2018E23
Will a New Neutrino Change the Standard Model?
S2018E24
Quantum Invariance and the Origin of the Standard Model
S2018E25
The Misunderstood Nature of Entropy
S2018E26
Reversing Entropy with Maxwell's Demon
S2018E27
How Close to the Sun Can Humanity Get?
S2018E28
Quantum Theory's Most Incredible Prediction
S2018E29
How Will the Universe End?
S2018E30
Is There Life on Mars?
S2018E31
The Black Hole Entropy Enigma
S2018E32
How Much Information is in the Universe?
S2018E33
Quantum Gravity and the Hardest Problem in Physics
S2018E34
How to Detect Extra Dimensions
S2018E35
Computing a Universe Simulation
S2018E36
What Are the Strings in String Theory?
S2018E37
Will We Ever Find Alien Life?
S2018E38
Are Virtual Particles a New Layer of Reality?
S2018E39
Why String Theory is Right
S2018E40
Supersymmetric Particle Found?
S2018E41
'Oumoamoua is Not Alien
S2018E42
Did Life on Earth Come from Space?
S2018E43
Quantum Physics in a Mirror Universe
S2018E44
Why String Theory is Wrong
S2019E01
Are Dark Matter and Dark Energy the Same?
S2019E02
Our Antimatter, Mirrored, Time-Reversed Universe
S2019E03
The Crisis in Cosmology
S2019E04
Perpetual Motion from Negative Mass?
S2019E05
Sound Waves from the Beginning of Time
S2019E06
Secrets of the Cosmic Microwave Background
S2019E07
The Impossibility of Perpetual Motion Machines
S2019E08
The Future of Space Tourism with Richard Branson
S2019E09
Is Dark Energy Getting Stronger?
S2019E10
Could the Universe End by Tearing Apart Every Atom?
S2019E11
The Edge of an Infinite Universe
S2019E12
The Holographic Universe Explained
S2019E13
No Dark Matter = Proof of Dark Matter?
S2019E14
The Real Science of the EHT Black Hole
S2019E15
Why Quantum Computing Requires Quantum Cryptography
S2019E16
The Cosmic Dark Ages
S2019E17
The Alchemy of Neutron Star Collisions
S2019E18
How Black Holes Kill Galaxies
S2019E19
The Quasar from the Beginning of Time - STELLAR
S2019E20
Thorium and the Future of Nuclear Energy
S2019E21
The Quantum Internet
S2019E22
Did Time Start at the Big Bang?
S2019E23
Deciphering the Vast Scale of the Universe - STELLAR
S2019E24
What Caused the Big Bang?
S2019E25
Exploring a HUGE Radio Telescope in VR 180
S2019E26
What Happened Before the Big Bang?
S2019E27
How to Become an Astrophysicist + Challenge Question!
S2019E28
Is Earth's Magnetic Field Reversing?
S2019E29
Could We Terraform Mars?
S2019E30
Is Pluto a Planet?
S2019E31
How Many Universes Are There?
S2019E32
Black Hole Harmonics
S2019E33
Loop Quantum Gravity Explained
S2019E34
Is Time Travel Impossible?
S2019E35
Why We Might Be Alone in the Universe
S2019E36
Does Life Need a Multiverse to Exist?
S2019E37
Can You Observe a Typical Universe?
S2019E38
Is the Universe Finite?
S2019E39
The Doomsday Argument
S2019E40
Do Black Holes Create New Universes?
S2020E01
How to Capture Ghost Particles
S2020E02
How to Capture Black Holes
S2020E03
Solutions to the Three Body Problem
S2020E04
Hacking the Nature of Reality
S2020E05
Are There Infinite Versions of You?
S2020E06
Are Axions Dark Matter?
S2020E07
Does Consciousness Influence Quantum Mechanics?
S2020E08
How Decoherence Splits the Quantum Multiverse
S2020E09
Does Quantum Immortality Save Schrödinger's Cat?
S2020E10
How Do Quantum States Manifest in the Classical World?
S2020E11
How Black Holes Spin Space Time
S2020E12
What's on the Other Side of a Black Hole?
S2020E13
How We Know the Earth is Ancient
S2020E14
Was the Milky Way a Quasar?
S2020E15
Will Wormholes Allow Fast Interstellar Travel?
S2020E16
How We Know the Universe is Ancient
S2020E17
How Luminiferous Aether Led to Relativity
S2020E18
Mapping the Multiverse
S2020E19
Does Gravity Require Extra Dimensions?
S2020E20
Can Viruses Travel Between Planets?
S2020E21
What Happens After the Universe Ends?
S2020E22
Building Black Holes in a Lab
S2020E23
Dissolving an Event Horizon
S2020E24
Does Antimatter Explain Why There's Something Rather Than Nothing?
S2020E25
The Boundary Between Black Holes & Neutron Stars
S2020E26
How Stars Destroy Each Other
S2020E27
Can Future Colliders Break the Standard Model?
S2020E28
How Do We Know What Stars Are Made Of?
S2020E29
The Truth About Beauty in Physics
S2020E30
Could Life Evolve Inside Stars?
S2020E31
Solving Quantum Cryptography
S2020E32
Venus May Have Life!
S2020E33
Do the Past and Future Exist?
S2020E34
Is The Future Predetermined By Quantum Mechanics?
S2020E35
How The Penrose Singularity Theorem Predicts The End of Space Time
S2020E36
Electroweak Theory and the Origin of the Fundamental Forces
S2020E37
Can Free Will be Saved in a Deterministic Universe?
S2020E38
The Arrow of Time and How to Reverse It
S2020E39
Why Do You Remember The Past But Not The Future?
S2020E40
The Supernovas At The End of The Universe
S2020E41
Navigating with Quantum Entanglement
S2021E01
What Happens During a Quantum Jump?
S2021E02
Can We Break the Universe?
S2021E03
Is Dark Matter Made of Particles?
S2021E04
How Does Gravity Warp the Flow of Time?
S2021E05
Gravitational Wave Background Discovered?
S2021E06
Does Time Cause Gravity?
S2021E07
How Does Gravity Affect Light?
S2021E08
The NEW Crisis in Cosmology
S2021E09
Can You Freeze A Quantum System By Observing It?
S2021E10
Why the Muon g-2 Results Are So Exciting!
S2021E11
What If Dark Matter Is Just Black Holes?
S2021E12
The NEW Warp Drive Possibilities
S2021E13
How To Know If It's Aliens
S2021E14
Breaking The Heisenberg Uncertainty Principle
S2021E15
What If (Tiny) Black Holes Are Everywhere?
S2021E16
The (Slow) Crisis Of Space Junk
S2021E17
Can Space Be Infinitely Divided?
S2021E18
How Quantum Entanglement Creates Entropy
S2021E19
Electrons DO NOT Spin
S2021E20
Where Are The Worlds In Many Worlds?
S2021E21
How Magnetism Shapes The Universe
S2021E22
How An Extreme New Star Could Change All Cosmology
S2021E23
How to Communicate Across the Quantum Multiverse
S2021E24
How Vacuum Decay Would Destroy The Universe
S2021E25
First Detection of Light from Behind a Black Hole
S2021E26
Neutron Stars: The Most Extreme Objects in the Universe
S2021E27
How Electron Spin Makes Matter Possible
S2021E28
Why Magnetic Monopoles SHOULD Exist
S2021E29
New Results in Quantum Tunneling vs. The Speed of Light
S2021E30
Will Constructor Theory REWRITE Physics?
S2021E31
Is ACTION The Most Fundamental Property in Physics?
S2021E32
What If Our Understanding of Gravity Is Wrong?
S2021E33
Are Black Holes Actually Fuzzballs?
S2021E34
What Happens If A Black Hole Hits Earth?
S2021E35
How to Find ALIEN Dyson Spheres
S2022E01
How To Simulate The Universe With DFT
S2022E02
How To Build The Universe in a Computer
S2022E03
How Does Gravity Escape A Black Hole?
S2022E04
Is The Wave Function The Building Block of Reality?
S2022E05
Are Cosmic Strings Cracks in the Universe?
S2022E06
Is the Proxima System Our Best Hope For Another Earth?
S2022E07
What If Charge is NOT Fundamental?
S2022E08
Where Is The Center of The Universe?
S2022E09
Could The Universe Be Inside A Black Hole?
S2022E10
Does the Universe Create Itself?
S2022E11
Why Does the W Boson's Mass Matter?
S2022E12
Does The Universe Expand Everywhere?
S2022E13
What If the Galactic Habitable Zone LIMITS Intelligent Life?
S2022E14
How Was the Modern Milky Way Born?
S2022E15
What If Physics IS NOT Describing Reality?
S2022E16
Has The Black Hole Information Paradox Been SOLVED?
S2022E17
Is Interstellar Travel Impossible?
S2022E18
Could We Decode Alien Physics?
S2022E19
What If We Live in a Superdeterministic Universe?
S2022E20
How Many States Of Matter Are There?
S2022E21
What Happens Inside a Proton?
S2022E22
What If Dark Energy is a New Quantum Field?
S2022E23
What Makes The Strong Force Strong?
S2022E24
Could the Higgs Boson Lead Us to Dark Matter?
S2022E25
How YOU Can Use JWST
S2022E26
Why Is 1/137 One of the Greatest Unsolved Problems In Physics?
S2022E27
The REAL Possibility of Mapping Alien Planets!
S2022E28
The Equation That Explains (Nearly) Everything!
S2022E29
Why Did Quantum Entanglement Win the Nobel Prize in Physics?
S2022E30
What If Humanity Is Among The First Spacefaring Civilizations?
S2022E31
Are there Undiscovered Elements Beyond The Periodic Table?
S2022E32
How To See Black Holes By Catching Neutrinos
S2022E33
How Are Quasiparticles Different From Particles?
S2022E34
How Can Matter Be BOTH Liquid AND Gas?
S2023E01
Did The Moon Form in 24 Hours?
S2023E02
What If The Universe Is Math?
S2023E03
What If Alien Life Were Silicon-Based?
S2023E04
How Earth REALLY Moves Through the Galaxy
S2023E05
How Does The Nucleus Hold Together?
S2023E06
Are Space And Time Real?
S2023E07
What If Space & Time Are Created By Our Brains?
S2023E08
What's Your Brain's Role in Creating Space & Time?
S2023E09
What If Black Holes ARE Dark Energy?
S2023E10
How Much Of The Universe Can Humanity Ever See?
S2023E11
How Far Beyond Earth Could Humanity Expand?
S2023E12
NEW DISCOVERY About Supermassive Black Holes Explained!
S2023E13
Fermions Vs. Bosons Explained with Statistical Mechanics!
S2023E14
Could LIGO Find MASSIVE Alien Spaceships?
S2023E15
Is 'Perpetual Motion' Possible with Superfluids?
S2023E16
Can We Move PLANET EARTH Across the Universe?
S2023E17
What Supernova Distance Would Trigger Mass Extinction?
S2023E18
Did AI Prove Our Proton Model WRONG?
S2023E19
Does Axionic Dark Matter Bind Galaxies Together?
S2023E20
What If The Speed of Light is NOT CONSTANT?
S2023E21
Was the Gravitational Wave Background Finally Discovered?!?
S2023E22
Do We Need a NEW Dark Matter Model?
S2023E23
Did JWST Discover Dark Matter Stars?
S2023E24
What If Space is NOT Empty?
S2023E25
What NEW SCIENCE Would We Discover with a Moon Telescope?
S2023E26
Are Room Temperature Superconductors IMPOSSIBLE?
S2023E27
Are Pilot Wave & Many Worlds THE SAME Theory?
S2023E28
Why Did Attosecond Physics Win the NOBEL PRIZE?
S2023E29
How Will We (Most Likely) Discover Alien Life?
S2023E30
What If Gravity is NOT Quantum?
S2023E31
Does Many Worlds Explain Quantum Probabilities?
S2023E32
What if Humans Are NOT Earth's First Civilization? | Silurian Hypothesis
S2023E33
What If There's A Black Hole Inside The Sun? | Hawking Stars
S2024E01
Can The Crisis in Cosmology Be SOLVED With Cosmic Voids?
S2024E02
Does Antimatter Create Anti-Gravity?
S2024E03
Did JWST SOLVE The Mystery of Supermassive Black Hole Origins?
S2024E04
What if Singularities DO NOT Exist?
S2024E05
EMP Attack: The Real Science of Electromagnetic Pulse
S2024E06
Dark Forest: Should We NOT Contact Aliens?
S2024E07
Does Space Emerge From A Holographic Boundary?
S2024E08
What If Gravity is NOT A Fundamental Force? | Entropic Gravity
S2024E09
How Eclipses Revealed Our Solar System
S2024E10
Why Is The World Rushing Back To The Moon?
S2024E11
What Happens To Quantum Information Inside A Black Hole?
S2024E12
Interstellar Expansion WITHOUT Faster Than Light Travel
S2024E13
Can Black Holes Unify General Relativity & Quantum Mechanics
S2024E14
How Supernovas Act as Universe's Largest Particle Accelerators
S2024E15
Is It IMPOSSIBLE To Cross The Event Horizon? | Black Hole Firewall Paradox
S2024E16
Will The Sun's Magnetic Field Flip This Year?
S2024E17
Can a Particle Be Neither Matter Nor Force?
S2024E18
How To Detect Faster Than Light Travel
S2024E19
Was Penrose Right? NEW EVIDENCE For Quantum Effects In The Brain
S2024E20
Colored Black Holes Explained
S2024E21
Can We Create New Elements Beyond the Periodic Table?
S2024E22
Is Gravity RANDOM Not Quantum?
S2024E23
What If Gravity Isn't Quantum? New Experiments Explore
S2024E24
The NEW PHYSICS of Black Hole Star Capture | Extreme Tidal Disruption Events
S2024E25
What If The Universe DID NOT Start With The Big Bang?
S2024E26
What If The Cosmological Constant Is NOT Constant?
S2024E27
Do Neutron Stars Shine In Dark Matter?
S2024E28
How Can Humanity Become a Kardashev Type 1 Civilization?
S2024E29
Can Space Time Remember?
S2024E30
Is E=MC^2 Incomplete?
S2024E31
The New Ultimate Energy Limit of the Universe
S2024E32
What Does An Electron ACTUALLY Look Like?
S2024E33
Does Infinity minus infinity equal an Electron
S2025E01
How Many Black Holes Are In The Solar System
S2025E02
Does Timescapes Disprove Dark Energy
S2025E03
The Crisis in Physics: Why the Higgs Boson Should NOT Exist!
S2025E04
The Final Barrier to (Nearly) Infinite Energy
S2025E05
Will The Big Bang Happen AGAIN (and Again)?
S2025E06
Your DNA Is (Almost Certainly) From Outer Space
S2025E07
How Astrophysics Can (LITERALLY) Save the World
S2025E08
NEW EVIDENCE: Earth Had Rings (and Might Regain Them)
S2025E09
Why Didn't Antimatter Destroy The Universe? | LHC Breakthrough
S2025E10
Quantum Energy Teleportation is REAL!
S2025E11
Is There A Simple Solution To The Fermi Paradox?
S2025E12
Is Our Model of Dark Energy WRONG?
S2025E13
The Crisis In Physics Are We Missing 17 Layers of Reality
S2025E14
The Crisis In Physics Is The Universe Random Or Finely Tuned
S2025E15
Why Is All DNA Right Handed?
S2025E16
Why The Multiverse Could Be Real
S2025E17
Is There Evidence For a Vast Multiverse?
S2025E18
The Most Important Satellite You've (Probably) Never Heard Of
S2025E19
At What Point Does Spacetime Become Quantum?
S2025E20
Why Life on Mars Will DOOM Humanity
S2025E21
We Were WRONG About the Quantum Eraser!
S2025E22
Why Antimatter Engines Could Launch In Your Lifetime
S2025E23
The Gravity Particle Should Exist. So Where Is It?
S2025E24
Do We Live in the Rarest Solar System In The Universe
S2025E25
Heisenberg Made a Discovery in 1925. We Still Can't Explain It
S2025E26
Black Holes. Explained. For 1.5 Hours
S2026E01
The Universe Itself Might Be Hiding the Gravity Particle From Us
S2026E02
This Particle Solved Everything. We Just Found Out It Isn't Real
S2026E03
How Gravity's Greatest Secret Might Finally Be Unlocked
S2026E04
We Timed a Cosmic Explosion. It Might Solve Dark Energy
S2026E05
There's No Life On Mars. But Underneath It
S2026E06
The Time Travel Paradox Hidden Inside Einstein's Relativity