How We Know The Earth Is Ancient

PBS Space Time
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In astronomy we talk about billions of years like it’s no big deal. But how can we be sure about timescales so far beyond the capacity for human intuition? Our discovery of what we now call deep time is very recent - as recent as our discovery of the true spatial vastness of our universe. And it came as scientists tried to measure the age of the Earth. What they found was as shocking and humbling as anything seen through the telescope.
Hosted by Matt O'Dowd
Written by Dan Falk & Matt O'Dowd
Graphics by Leonardo Scholzer, Yago Ballarini, & Pedro Osinski
Directed by: Andrew Kornhaber
Executive Producers: Eric Brown & Andrew Kornhaber
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Published on


Apr 7, 2020




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Comments 80
William Griffin
aliens have been terraforming earth for 270 million years, check the Cyclops construction in Cuzco and SacksayHuman also in Peru. so what age of earth should come to the minds of well informed humans ? my guess well over a Billion years old .. and that rocks which can be dated thousands of Millions years old exist and have existed in numerous Museums around the world for centuries.
Nimi Nim
Nimi Nim Day ago
Can you talk about the Axis of Evil?
SwordsmanRyan 9 days ago
Downvote for your godlessness. You don’t have to agree with religion but you need not say their ideas were just invented. Religion doesn’t tell us what science says, why must science insist what religion says?
Dillon Headley
Dillon Headley 10 days ago
was my comment deleted...?
Jonathan Metz
Jonathan Metz 11 days ago
Been watching PBS Spacetime for a good three years now. I love this series, and I particularly admire, Matt, your thoughtful and relatable communication skills. Just want to say something about this episode in particular. I appreciate the way you approached the topic of science and the Book of Genesis. As an evangelical (theologically) who doesn't believe there's any conflict between the claims of Bible and empirical truth, (in a theistic universe all truth must come from the same mind/Creator), it's really frustrating when otherwise objective science communicators essentially do exegesis (who, most likely, aren't learned in Biblical exegesis) and imply that the writers of Genesis or other parts of the Bible were trying to answer the kind of questions that in fact weren’t asked the way we ask them today until the Enlightenment. (e.g. The writers of Judeo-Christian scripture tried to answer material questions about the physics of the universe but science saved us from such anthropocentric thinking and revealed to us the truth.) Thank you for your objectivity.
Curtis Jensen
Curtis Jensen 11 days ago
So in the end it mainly comes down to radioactive dating? I must ask: are we certain that nothing can make a radioactive isotope decay faster, thus making things appear older than they are?
bulentkulkuloglu 12 days ago
So the partner is Turkish :)) Bahar is a Turkish female name.
Small and Stressed
Small and Stressed 16 days ago
Our entire solar system is a bunch of happy accidents. Like neptune and uranus being the true middle children they are having a crucial role in the solar system’s planets as we know them (jupiter is a bully). The 9th planet even taking one for the team when the literal planet embodiment of Zeus exiled it out behind the kuiper belt. Not to mention mercury being the solar system’s punching bag... oof chaos theory be brutal.
Javier 17 days ago
This channel and its hundreds of thousands of viewers make me cry humbled by the intelligence of some people and the vastness of space time and beyond, and gives me honest hope for humanity.
john piers
john piers 17 days ago
I think some of these scientific ideas such as determining age may just just be a way to discredit the accuracy of religious books(Bible) since no one is able scientifically prove otherwise.
Jeff Hambleton
Jeff Hambleton 21 day ago
When was the supernova that created all the heavy elements? Then why was the earth made from this but the sun was mainly hydrogen?
Josh 23 days ago
I saw this guy blink once the entire video 😂
Yahsameen Bush
Yahsameen Bush 23 days ago
Quick question. If I were to shrink our sun down to a black hole, would the Hawking radiation still keep us warm if it gives off energy with the same information as it was form with? Provided if there is enough quantum form to generate that energy, heat, light, etc.?
Thomas Jamison
Thomas Jamison 24 days ago
eventually he'll get over his errors of judgment and erroneous statements of fact. Plasma physics had changed all of his assumptions.
Tony Dai
Tony Dai 25 days ago
7:07 Just a correction, the Earth's surface is much hotter than expected, even when radiation is taken to consideration. This is because the convection currents in the mantle bring up heat from the core.
Craig Spencer
Craig Spencer 26 days ago
At the end you said the earth orbited the sun 4.5 billion times, which got me thinking; has Earth's orbit decayed around the sun? Has it actually orbited that many times, or possibly more or less due to changing momentum?
ryan c
ryan c 28 days ago
Thumbs down react only if you're a yec haha
Chakravarthy C
Chakravarthy C 28 days ago
4.32 billion years younger or older than U. .
Pak De
Pak De 28 days ago
After 35 years of marriage 4.5 billion years doesn't seem so long.
elijah bullers
elijah bullers 29 days ago
the big bang never happend though so u cant think of it as anything other than fiction
elijah bullers
elijah bullers 29 days ago
just about everything he's said about the age of the planet is wrong. sorry bro video's are awesome but ur just...wrong
elijah bullers
elijah bullers 29 days ago
the earth is over 6'000 years old. u can fight me on that and u will loose
elijah bullers
elijah bullers 29 days ago
also evaluation is dumb u can fight me on that as well u'll still loose
Doc Lex
Doc Lex 29 days ago
little a lot less of your face, and more pictures or videos... though you are handsome, i really dont wanna look at your ugly mug all the time every day, and i am sure i am not the only one... thx for understanding
Ed Holohan
Ed Holohan 29 days ago
We live in a sim.
quibily Month ago
Can anybody recommend a book that could help an adult non-scientist understand the concepts of half-life and carbon dating and stuff like that? I've read explanations of this in a few books, but it's usually over the course of just a chapter or two. I think I need a whole book version of this video, basically. But I'm not motivated enough to read a text book, haha.
Netan Vekaru
Netan Vekaru Month ago
Oct 4004 BC. 😂😂😂
micah blyther
micah blyther Month ago
This is all incorrect. Next thing they are going to say that there is no god. I am only watching this because I do not want to fail my class. But I will still remember that this junk is wrong
micah blyther
micah blyther 17 days ago
@Dundoril people who don't believe in God
Dundoril Month ago
Well it's hard to say... Which of the thousands of God's men created are you talking about?
Dan X2
Dan X2 Month ago
Featured on Astral Education facebook.com/astralslate/
Panerai Ferrari
Panerai Ferrari Month ago
But wait ... Answer in Genesis says the world is only 6,000 years old ... I really think you have your facts wrong :)
Grant Jarvis
Grant Jarvis Month ago
Everything I know says earth had a beginning. Any argument is over dating of beginning
Ken Durham
Ken Durham Month ago
But, but, I thought it was only 6,000 years old? That's what these preachers keep saying. I think it's flat now also. Not sure when that happened.
Brooke Gaskin
Brooke Gaskin Month ago
I remember way back when Uranium and Lead dating took real guts cause of all the ignorant narrow minded insecure dummies, always picking themselves up by putting some one else down. You show 'em Uranium and Lead!
Brooke Gaskin
Brooke Gaskin Month ago
A gentleman never asks a lady her age.
Brooke Gaskin
Brooke Gaskin Month ago
we know the earth is ancient cause look how it used to dress in some of those pictures. It used to be a big time hippie, bell bottoms, long hair, that funny smoke smell. Earth is O.G.
Fan Wang
Fan Wang Month ago
Bah this is boring, deep time deep space, took me only 2 mins switch to deep throat.
Sagnik Nath
Sagnik Nath Month ago
wish you could have touched upon the Purana texts in ancient Indian cosmology which actually put the age of every iteration of the universe ("Brahma") at 155 trillion years!! Even Carl Sagan was in awe of this number
Ian Balmer
Ian Balmer Month ago
Atlas shrugged, and he is holding it all up!
Artifact Hunter
Artifact Hunter Month ago
Sorry but you’re confused the earth is young and was created!
micah blyther
micah blyther Month ago
yeh this is all fake
beatyouonce Month ago
Could one say that the passage of time is the expansion of the universe? And time delay is caused by matter and energy slowing down that expansion?
Nicholas Williamson
Panic at tie disco -high hopes :)very nice very nice
Phiphe Dude
Phiphe Dude Month ago
The Last
The Last Month ago
These are assumptions. They can’t prove it. Remember that. 90% of all scientific theorys have been proven wrong. Over 50% of all ideas that come from universities end up being false. They never seem to mention those facts.
@The Last how exactly are you going to build a theory without first making assumptions and then comparing the consequences of these assumptions with our reality? Even Newton did so: 1)apple fall on head 2)assume for shits and giggles univeral attraction 3)construct that into formulas 4)make predictions based on formulas 5)compare results to reality assumptions are essential to the scientific method, so I'm not really sure what you mean.
chromium2.0 Month ago
@The Last Assumption - a thing that is accepted as true or as certain to happen, without proof. Theory - a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained. Science is still very much in the business of theories. The only "assumptions" that are made are the things we already know and can all agree are true such as natural laws. But since natural laws have proof to back them up, they're actually not assumptions, by definition.
The Last
The Last Month ago
Science has started making assumptions instead of theories. Know the definition first
@The Last Because a general practitioner isn't a researcher, same as most engineers aren't involved in research. And yes the scientific method is still being applied just more abstracted as the low hanging fruit of research are gone. Currently modelling, simulations and quantitative or approximative methods have become widely used and accepted, simply due to the power modern computers allow us and the complexity of the fields in study. And once again a simple practical argument applies: Our technology is improving as rapidly and becoming ever more effective and efficient, how would this occur if the sum of our knowledge weren't increasing? In conclusion: Scientific method and Research still very much a thing, just a lot more complicated than in the early 20th century.
chromium2.0 Month ago
@The Last Doctors absolutely use theories. Ever heard of the germ theory of disease? It's the theory that disease is caused by germs and pathogens. It may seem weird to call that a theory since we know it to be true, but the scientific definition of a theory is very different from how it normally used every day. We know that germ theory is true with the same certainty that we know the theory of evolution or the theory of relativity is true.
Dennis White
Dennis White Month ago
This planet was billions of years old before it became Earth.
OnHoldAt50 Month ago
You lost me on "evolution"- as if that's something that's still real. There's no foundation for proving that a human came from a bird, or anything of anything for that matter. Each DNA is unique to it's own kind. Why has no one ever actually found a "missing link?" Love your videos dude, but I gotta thumb down this one.
Dundoril Month ago
Yes human did not come from birds... Nobody ever said that... Sometimes I wonder why people insist on showing that they have no idea about theories that they think are wrong...
chromium2.0 Month ago
@OnHoldAt50 I'm currently making my way through the Bible. In Exodus right now. I'm actually enjoying it. Much of it is beautifully written. I don't see it as infallible or as the word of God though. That's where we disagree. Perhaps I'll change my mind one day, but extraordinary claims require extraordinary evidence. So it'd take a lot to prove that the Bible is directly inspired by God.
OnHoldAt50 Month ago
@chromium2.0 Seems we're at an impasse then. I dare you to read it in attempt to punch holes. You might change your mind (about the science aspect too. The bible is chocked full of science). There is no cross-over of any species on a molecular level. Each species is it's own. There's no compelling argument to prove that man's intelligence AND consciousness EVOLVED from nothing.
chromium2.0 Month ago
@OnHoldAt50 the Bible is not an authority on science. And even if it was, it couldn't possibly be cited as a source to disprove evolution as it was written several thousand years before modern evolutionary theory was developed, and continues to develop
OnHoldAt50 Month ago
Freedom Anderson Glad someone finally asked. The most infallible source ever. It starts with - In the beginning God created the heavens and the earth. Without getting into the theological aspects, pretty much Moses was spot-on about each kind unto it's own. The guy citing fossils as evidence beyond refute is nuts. It's a Rock! Regardless if you believe God or intelligent design, not species to species. I love the videos this guy does, it blows my mind he went in the evolution direction so quickly.
Gabrielle Warburton
You have a great voice to sleep to so thank you a wake up knowing random stuff about time and space which apparently I say in my sleep so everyone gets an education lol
Pat Flat
Pat Flat Month ago
I can't help thinking he's like a proportionate Peter Dinklage.
kwamepi1 Month ago
Alot of presumptions
assuming that your current understanding of the universe is right until you see a reason to change that assumption is rather reasonable to me.
Fiza Ali
Fiza Ali Month ago
Plz can some body answer to my question... is time an illusion? What if there was no time? Whaf if nothing had any motion.
Ronaldo C.
Ronaldo C. Month ago
No one really knows how old is earth...we can only estimate.
We've got a few hard upper limits and a few hard lower limits. So we can be very sure that it's younger than the solar system and older than all fossils. and that's just a guess by some dude on the internet.
Sheri Singerling
Woot I actually felt smart watching this Space Time episode for once! Perhaps my PhD in geology came into play 🤔
Jordan Moore
Jordan Moore Month ago
"-1/2 pt Watch your SIG. FIGS !" - brilliant!
καμιά ψυχή
Deep time was not discovered recently... it's been around for eons. HAH
chad moore
chad moore Month ago
technically i thought we havent rotated around the sun 4.5 billion times? i thought the planets were in closer orbits in the beginning with greater angular velocity? Like how the moon use to be much much closer. and that it slowly moves out as it rotates slower. its extremely slow process but we are talking billions of years here. I wonder if this made more than a negligible impact on our # of orbits? doubt it but hey
HolyWrath Month ago
Okay so you are saying 4.5 billion years, but the real question is how long have we "the human population been here"? "Have we been here that whole time or are we relatively new, and if we are how did we just show up all of a sudden, or did we grow up here over a long process of developing as as species"?
Freedom Anderson
Modern Humans evolved 200,000-300,000 years ago.
Ivan Loredo-Vidal
You mention many speculators who got it wrong, and omit the one who got it right: Clair Patterson! Who btw, studied meteorites to get it right and whose lead-free lab ambience was painstaikingly carried out. en.wikipedia.org/wiki/Clair_Cameron_Patterson
Ashton Walters
Ashton Walters Month ago
I feel like the word "ideer" is to Americans as "Warshing machine" is other English speaking countries.
Tomasz Sarba
Tomasz Sarba Month ago
Marie Skłodowska-Curie [ 6:41 ], not Marie Curie.
Delta Daze
Delta Daze Month ago
Why do we care what the age of the earth is again???🤷🏻‍♀️
so we understand our home and how it works.
Life is a Trip
Life is a Trip Month ago
Question. Elements are made in the stars, how did the Quantum Fields contribute to the making of elements? thanks
polanve Month ago
Here is a more detailed video on the subject: www.dailymotion.com/video/x6u3qd9
Amigps01 Month ago
For a second I was like....wait how do they know so accurately how many times the earth went around the sun??? And then it clicked. Yes I’m an idiot.
Jason Phillips
Jason Phillips Month ago
Wait.?. So the almighty darwin was wrong about the age of the earth? Blasphemy!
Stephen Lord
Stephen Lord Month ago
More than 4.5 billion years remember we live on Earth 2.0. Earth was here before the collision that created the moon.
Burt1038 Month ago
a few billion years old may seem like a long time on human timescales, but it is actually extremely early in the life of the universe. Like, less than .0000001%
Burt1038 Month ago
@Layne McCormic No I mean the universe itself is extremely young compared to how long it could last until heat death.
Layne McCormic
Layne McCormic Month ago
The universe is about 13.8 billion years old, 4.5 billion years is about 32% of the life of the universe.
Sylvain Rocheleau
Where is your cat?
ronkirk50 Month ago
"Deep time" is impossible for me to get my mind around. A thousand years? A hundred thousand years? A million years? A billion years? Those timescales are just incomprehensible for me. One thing I can understand is that it took millions of years of evolution to produce the biosphere and we will have pretty much completely destroyed it in just a few hundred years.
Kaitlyn L
Kaitlyn L Month ago
PBS Eons I believe has done a video all about deep time to try and help people get their head around it. It may or may not help you. The Cosmos reboot from a few years back also did, with metaphors of a calendar (if all of history were compressed into one year), right at the beginning of the series. I think Eons' video is about geological time while Cosmos' example is about the universe, though. But various techniques like "if all of time were a year" or a day or just put on a big line can help our brains map our experiences onto this bigger concept.
Verisimilitude Dude
Time is relative to the observer.....
Kings Tallington
the earth is not "ancient" it still exists. ancient adjective: belonging to the very distant past and NO LONGER IN EXISTENCE!
max5250 Month ago
... , or: having been in existence for a very long time.
Micheal Ray
Micheal Ray Month ago
Then they'll say the earth is 5 billion years old, then 6, then seven, then 20, then they'll shut up and stop making stupid claims
Dundoril Month ago
No they won't.... One limit is the age of the sun... And the sun is certainly not 20 billion years old.
the beginning of the universe is going to be a hard upper limit so no. and currently we have no indication that earth is older than the current assumptions.
Bill Demich
Bill Demich Month ago
Geologists are hilarious.
Lex Raphael
Lex Raphael Month ago
Should of just skipped all the biblical stuff, that summary was lacking.
Simon Liu
Simon Liu Month ago
My Lord, this guy looks like Robert the Bruce from Braveheart
R B Month ago
Some infinities are larger than others
Jun Acebedo
Jun Acebedo Month ago
Radiometric dating is not infallible
matt dobbin
matt dobbin Month ago
The universe was created by evil men 32 years ago. Anyone caught supporting false history will be imprisoned along with the 3 wise men.
Young Yoda
Young Yoda Month ago
earth is 6000 years old
no, i am 6000 years old. and earth wasn't created then, i checked.
John Lucier
John Lucier Month ago
can we meet her?
Leaving Blank
Leaving Blank Month ago
white holes, black holes, brown holes. whatever. as long as it's shaved...
Thrust n Howl
Thrust n Howl Month ago
Awesome, just awesome, and awe inspiring episode. You have so succinctly described these methods to be useful in "conversations" with other people. I have literally been trying to parse such a coherent statement to present to others that hold more mainstream American views. Again thank you.
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