Mass attracts mass
More mass means a stronger gravitational pull.
01 / 20START HERE
FROM HERE TO THE EDGE OF WHAT WE KNOW
Space is our
biggest address.
A visual trip from one small rocky planet to the leading edge of cosmology.
→Use arrows, swipe, or the controls.
Press A to listen or N to read the narration.
Press A to listen or N to read the narration.
YOU
EARTH
SOLAR SYSTEM
MILKY WAY
OBSERVABLE
UNIVERSE
UNIVERSE
YOU ARE HERE
Spacelight + particles + fields + gravity
Universeall the space, time, matter, and energy we can observe
Our questionHow can we know anything this enormous?
02 / 20LIGHT IS A TIME MACHINE
Looking up means
looking back in time.
👁NOW
MOON1.3 seconds ago
SUN8 minutes ago
NEAREST STAR4.2 years ago
ANDROMEDA2.5 million years ago
300,000kilometers each secondspeed of light in empty space
THOUGHT EXPERIMENT
If an alien 65 million light-years away had a perfect telescope pointed at Earth, what time in Earth’s history would its arriving light show?
The age of the dinosaurs.A light-year is distance, not time: the distance light travels in one year.
03 / 20ONE RULE, MANY ORBITS
An orbit is a fall
that keeps missing.
EARTH
slow → falls nearby
faster → falls farther
fast enough → orbit
GRAVITY PULLS INWARD ↓
Sideways speed matters
Moving forward keeps the falling object from hitting.
Same physics
Apples, moons, planets, and satellites follow the same basic rule.
04 / 20A FAMILY WITH A SHARED ORIGIN
Our solar system grew
from one spinning cloud.
1 · CLOUDgas + dust collapse
→
2 · DISKmaterial spins flat
→
3 · CLUMPSsmall pieces collide
→
4 · WORLDSorbits settle
INNERrocky + warmMercury · Venus · Earth · Mars
OUTERgiant + coldJupiter · Saturn · Uranus · Neptune
4.6billion years old
MODEL: Think of a spinning pizza of material—most mass gathers in the middle while the rest clumps into worlds.
05 / 20PLANETS ARE NOT COPIES
Worlds come in
many recipes.
| WORLD | MAIN STUFF | ATMOSPHERE | DAY-SIDE CLUE |
|---|---|---|---|
| Mercury | Rock + metal | Almost none | Wild temperature swing |
| Earth | Rock + water | Nitrogen + oxygen | Liquid surface water |
| Jupiter | Hydrogen + helium | Deep gas layers | No solid surface |
| Exoplanet | Many possibilities | Measured by spectra | Thousands confirmed |
HOW WE FIND SOME EXOPLANETS
tiny dip in starlight
Important: “Habitable” means conditions might allow life. It does not mean “inhabited.”
06 / 20LIGHT, ANGLES, AND TIDES
The Moon changes shape—
but only from our view.
SUNLIGHT →
EARTH
NEWFIRST QUARTERFULLLAST QUARTER
NOT THIS
Moon phases are not Earth’s shadow.
Moon gravity pulls ocean water into tidal bulges.
07 / 20OUR NEAREST STAR
The Sun is a star
powered by fusion.
CORONA
SURFACE
CONVECTION
RADIATION
CORE15 million °C
HYDROGEN+HYDROGEN→HELIUM+ENERGY
NOT A CAMPFIRE
Fire rearranges atoms. Fusion joins atomic nuclei and releases far more energy.
SUNLIGHT→PLANTS→FOOD→YOU
08 / 20COSMIC FACTORIES
Stars build the atoms
that build us.
GAS CLOUD
→
★NEW STARmass chooses the path
LOWER MASS→RED GIANT→WHITE DWARF
HIGH MASS→SUPERGIANT→SUPERNOVA→NEUTRON STAR
or BLACK HOLE
or BLACK HOLE
HHydrogenearly universe
CCarbonstars
OOxygenstars
FeIronmassive stars
AuGoldextreme mergers / explosions
The carbon in your cells was forged in an earlier generation of stars.
09 / 20CITIES OF STARS
A galaxy is a whole
ecosystem held by gravity.
SPIRALdisk + arms + central bulge
IRREGULARno simple shape
A GALAXY CONTAINSstarsgasdustblack holesdark matter**inferred from gravity
When galaxies collide: gravity reshapes them, but most individual stars miss because the space between stars is enormous.
10 / 20HALFWAY OUT
Our cosmic address
has nested neighborhoods.
- 1EARTHone rocky planet
- 2SOLAR SYSTEMone star + orbiting family
- 3MILKY WAYhundreds of billions of stars
- 4LOCAL GROUPmore than 50 galaxies
- 5COSMIC WEBgalaxy filaments + vast voids
LOCAL GROUPANDROMEDAMILKY WAY ← usTRIANGULUMslow gravitational dance
Future forecast: The Milky Way and Andromeda will likely merge in several billion years—not an imminent danger.
11 / 20HOW DO WE MEASURE “FAR”?
No ruler reaches the stars.
So we build a ladder.
RADARSolar System
PARALLAXnearby stars
CEPHEID STARSnearby galaxies
TYPE Ia SUPERNOVAEdistant galaxies
PARALLAX
Earth’s two orbital viewpoints make a nearby star appear to shift.
REDSHIFT
Known color lines slide redward when space stretches the light.
Good science links the rungs. Each method is checked against a nearer one. Disagreements can reveal hidden errors—or new clues.
12 / 20SPACE ITSELF CAN CHANGE
The universe is expanding—
but not into a room.
THEN
→
LATER
Every raisin sees faraway raisins separating faster as the dough grows.
RECESSION SPEED ↑DISTANCE →farther ≈ faster recession
THE MODEL HELPS:all large-scale distances grow
THE MODEL BREAKS:the universe has no known outside, crust, or center raisin
13 / 20A HOT, DENSE EARLY UNIVERSE
The Big Bang was not
a bomb in empty space.
?unknown physics
HOT PLASMAseconds → years
ATOMS + CMB380,000 years
FIRST STARShundreds of millions
TODAY13.8 billion years
matter exploding from one center into pre-existing emptiness
space expanding everywhere while the universe cools
- mostly hydrogen + helium
- cosmic microwave background
- growth of structure
BOUNDARY: The model describes a very early hot universe. It does not yet tell us what—if anything—came “before.”
14 / 20THE OLDEST LIGHT WE CAN SEE
The universe left us
a baby picture.
COLDERHOTTER
temperature differences: only tiny fractions of a degree1HOT FOG
Early matter scattered light again and again.
2ATOMS FORM
At 380,000 years, light could travel freely.
3LIGHT STRETCHES
Expansion shifted that glow into microwaves.
4RIPPLES GROW
Tiny dense spots became galaxies and the cosmic web.
Not the first instant: The CMB is the oldest light we can directly observe, released long after the earliest moments.
15 / 20INVISIBLE WEIGHT
We cannot see dark matter.
We can see what it does.
BACKGROUND
GALAXY
GALAXY
GALAXY CLUSTER
+ unseen mass
+ unseen mass
◉TELESCOPE
LIKE WIND
You cannot see wind itself, but moving leaves reveal its effect.
THREE GRAVITY CLUES
- GALAXIESrotate too fast for visible matter alone
- LENSINGreveals more mass than we see
- COSMIC WEBgrows as if extra gravity is present
KNOWN EFFECT · UNKNOWN IDENTITY No dark-matter particle has been confirmed in a laboratory.
16 / 20ACCELERATING EXPANSION
The universe is not only expanding.
The expansion is speeding up.
68%DARK
ENERGY
ENERGY
68% dark energy27% dark matter5% familiar matterApproximate, model-dependent flat ΛCDM values
SIZE OF UNIVERSE ↑
if expansion only slowed
observed acceleration
COSMIC TIME →“Dark energy” is a label for the effect—not a substance caught in a jar. A constant energy of empty space is the simplest fit, but surveys are testing it.
17 / 20NEW WAYS TO LISTEN
The universe sends
more than light.
✦
TWO NEUTRON STARSMERGE〰
LIGHTcolor, heat, chemistrytelescopes•••
NEUTRINOSghostlike particlesdeep detectors∿∿
GRAVITY WAVESspacetime vibrationsLIGO · Virgo · KAGRABLACK HOLE REALITY CHECK
From far away, a black hole pulls like any object with the same mass. It is not a roaming cosmic vacuum cleaner.
18 / 20FIRST GALAXIES
JWST watches the young universe
grow its first galaxies.
6.5 m
infrared mirror
WHY INFRARED?
VISIBLE→ space stretches light →INFRARED
Distant galaxy light is redshifted. Infrared also peers through dust.
CMB
0.38 million yrCOSMIC
DARK AGESFIRST STARS
+ GALAXIESTODAY
13.8 billion yr
0.38 million yrCOSMIC
DARK AGESFIRST STARS
+ GALAXIESTODAY
13.8 billion yr
OBSERVATION light + spectrumINTERPRETATION distance + mass + age
FRONTIER RULE: Surprising early galaxies need follow-up spectra and careful models—not instant rewrites of all cosmology.
19 / 20WHEN GOOD MEASUREMENTS DISAGREE
Modern cosmology has
live puzzles—not final answers.
HUBBLE CONSTANT
today’s expansion rate
today’s expansion rate
~67early-universe inference
~73late-universe distance ladder
km/s/Mpc · rounded, method-dependent
PERSISTENT DIFFERENCE = “HUBBLE TENSION”
Maps expansion and the growth of structure across cosmic time.
SPECTROSCOPY · GROUNDMaps galaxy shapes and lensing to test dark energy and gravity.
IMAGING · SPACE| POSSIBLE EXPLANATION | STATUS | WHAT WOULD HELP? |
|---|---|---|
| Hidden measurement bias | TESTING | independent methods |
| Changing dark energy | FRONTIER | more expansion history |
| New particles / gravity | FRONTIER | distinct predictions |
A tension is not proof of new physics. It is a clue that the data, the model—or both—deserve harder tests.
20 / 20THE MAP HAS BLANK SPACES
Cosmology is a tested map—
not a finished story.
OUR BEST
COSMIC MODELΛCDM
COSMIC MODELΛCDM
REDSHIFTexpansion
CMBhot early universe
ELEMENTSearly chemistry
LENSINGunseen mass
SUPERNOVAEacceleration
GALAXY MAPSstructure growth
WHAT IS DARK MATTER?IS DARK ENERGY CONSTANT?HOW DID THE FIRST STRUCTURES FORM?WHAT HAPPENED AT THE BEGINNING?
“The next move is not to memorize a final answer. It is to ask what evidence could tell the possible answers apart.”