Up to now, all we have learned is RELATIVE dating/aging.

Up to now, all we have learned is RELATIVE dating/aging…Law of SUPERPOSITION

Up to now, all we have learned is RELATIVE dating/aging…SUPERPOSITION NOT EXACT (JUST COMPARING how they RELATE to each other)

the COCKROACH has not changed dramatically over the last 125 MILLION YEARS

How do I know the ABSOLUTE age of these two cockroach fossils? 49 million years old 125 million years old

Recall how I’ve told you that evidence shows the Earth is about 4 Recall how I’ve told you that evidence shows the Earth is about 4.5 billion years old?????

How do we know the ABSOLUTE DATE of rocks & fossils from our Earth?

BBC HUNDREDS OF YEARS AGO WE TRIED TO DO EXPERIMENTS. http://www.dailymotion.com/video/x1dp3l7_how-did-we-get-here- the-story-of-science-nova-discovery-history-space-documentary- hd_t 1-8 exploration & archiving diversity 12-17 minutes (fossilized Paris) 25 minutes (age of Earth experiment) 25 minutes!!! 27-33 minutes (Geology inventor, Scottish unconformity—deep time—we are extensions of life) 39-42 Darwin 42-51 Wegener & plate techtonics, continental drift & biological evolution

Remember Le Comte de Buffon’s tried to ABSOLUTELY age of Earth!

But he didn’t know about RADIOACTIVE HEATING from UNSTABLE ATOMS Our crust holds in a lot of heat. Buffon didn’t consider radioactive heating! My steel balls weren’t radioactive like Earth!

Remember, everything is made of atoms. Positive protons (+) Neutral neutrons (o) Swirling electrons (-)

Remember, everything is made of atoms. Positive protons (+) (identifies the type of atom—atomic number!) Neutral neutrons (o) Swirling electrons (-) Electricity!

Swirling electrons (-) We haven’t talked too much about NEUTRONS (o), but they hold the PROTONS (+) together in the atomic nucleus. Positive protons (+) Neutral neutrons (o) Swirling electrons (-) Remember…opposites attract (+) to (-)!

TOO MANY NEUTRONS make ATOMS unstable RADIOACTIVE! Positive protons TOO MANY NEUTRONS (o) Swirling electrons

The BIGGEST atoms below are most unstable. (They are most radioactive Most likely have an abnormal number of neutrons (o).

the bigger the atom, the more neutrons numbers can vary The BIGGEST atoms below are most unstable. (They are most radioactive.) the bigger the atom, the more neutrons numbers can vary

Even a small percent of Earth’s carbon atoms are unstable.

But, even a small percent of Earth’s CARBON atoms are unstable. Carbon-14 is a RADIOACTIVE atom of carbon

But, even a small percent of Earth’s CARBON atoms are unstable. 6 protons(+) 8 neutrons(o) Carbon-14 is a RADIOACTIVE atom of carbon

Do UNSTABLE things stay together?

Unstable things DECAY (fall apart)

Unstable things DECAY (fall apart) AND GIVE OFF HEAT!!!

Unstable RADIOACTIVE ATOMS ALSO DECAY (fall apart). RADIATION inside our BODIES, we FALL APART!

Unstable RADIOACTIVE ATOMS DECAY…(fall apart). …inside our nuclear reactors and in the center of our Earth … this radioactive HEAT we need!!!

Unstable RADIOACTIVE ATOMS DECAY…(fall apart). …inside our nuclear reactors and in the center of our Earth … this radioactive HEAT we need!!!

Unstable RADIOACTIVE ATOMS DECAY like CLOCKWORK! blocks Unstable RADIOACTIVE ATOMS DECAY like CLOCKWORK!

blocks Unstable RADIOACTIVE ATOMS DECAY like CLOCKWORK! These unstable radioactive atoms decay back into stable atoms, usually over a long PRECISE time!

Right now, a small percent of you is made of radioactive Carbon-14 atoms.

Bean activity…

HALF-LIFE ACTIVITY

Mr. G will assign groups of 2-3. Each get paper to make a graph, yardstick & markers. You need exactly 100 beans. Count and get rid of bad ones (busted, painted on both sides, etc.) Give me your extra.

Count out EXACTLY 100 white/black (pink) beans. (give me your extra) Make & label a simple graph that fills most the sheet rate of decay half-lives

Count out 100 white/black (pink) beans. Make a simple graph (every notch could be 5 centimeters apart) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay half-lives

Count out 100 white/black (pink) beans. Make a simple graph (every notch could be 5 centimeters apart) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Your 100 beans represent 100 unstable radioactive atoms 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Your 100 beans represent 100 unstable radioactive atoms Put your 100 “radioactive, atomic” beans into your cup.

Your 100 beans represent 100 unstable radioactive atoms Pour them gently onto your big yellow paper.

Your 100 beans represent 100 unstable radioactive atoms Pour them gently onto your big yellow paper. SEPARATE the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up.

Your 100 beans represent 100 unstable radioactive atoms Pour them gently onto your big yellow paper and separate the ones that landed white side up from the blacks (or pinks) side up. How many stayed black (or pink) face up?

These black (or pink) face-up beans represent radioactive atoms that have NOT decayed yet The white, face-up “atoms” have decayed into more stable atoms now. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Mark the number of your black (or pink) “still radioactive atoms” that are face up at the 1st half –life. So, if you had 40 black (or pink) face-up beans, you’d mark them at 40% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

LISTEN CAREFULLY….. Put the old, white “stable” atomic beans into the storage bowl Mr. Goodman gives you. Set them aside.

You should now only have about 40-60 beans left that are still “radioactive.” Put the black (pink) “still radioactive atoms” back into your cup.

You should now only have about 40-60 beans left that are still “radioactive.” Put the black (pink) “still radioactive atoms” back into your cup. Pour these remaining beans gently onto your big yellow paper. SEPARATE AGAIN the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up.

You should now only have about 40-60 beans left that are still “radioactive.” Put the black (pink) “still radioactive atoms” back into your cup. Pour these remaining beans gently onto your big yellow paper. SEPARATE AGAIN the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up. How many stayed black (or pink) face up this time?

Mark the number of your black (or pink) “still radioactive atoms” that are face up at the 2nd half –life. So, if you have 30 black (or pink) face-up beans, you’d mark them at 30% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Put the white “stable” atomic beans into the storage bowl with the other “stable” atoms you had from before. Set them aside.

You should now have less than 50 beans left that are still “radioactive.” Put the black (pink) “still radioactive atoms” back into your cup.

You should now have less than 50 beans left that are still “radioactive.” Put the black (pink) “still radioactive atoms” back into your cup. Pour these remaining beans gently onto your big yellow paper. SEPARATE AGAIN the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up.

You should now have less than 50 beans left that are still “radioactive.” Put the black (pink) “still radioactive atoms” back into your cup. Pour these remaining beans gently onto your big yellow paper. SEPARATE AGAIN the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up. How many stayed black (or pink) face up this time?

Mark the number of your black (or pink) “still radioactive atoms” that are face up at the 3rd half –life. So, if you have 15 black (or pink) face-up beans, you’d mark them at 15% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Put the white “stable” atomic beans into the storage bowl with the other “stable” atoms you had from before. Set them all aside.

Your number of still “radioactive” atomic beans should be getting lower! Put the black (pink) “still radioactive atoms” back into your cup.

Your number of still “radioactive” atomic beans should be getting lower! Put the black (pink) “still radioactive atoms” back into your cup. Pour these remaining beans gently onto your big yellow paper. SEPARATE AGAIN the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up.

Your number of still “radioactive” atomic beans should be getting lower! Put the black (pink) “still radioactive atoms” back into your cup. Pour these remaining beans gently onto your big yellow paper. SEPARATE AGAIN the ones that landed WHITE face up from the ones that landed BLACK (or PINK) face up. How many stayed black (or pink) face up this time?

Mark the number of your black (or pink) “still radioactive atoms” that are face up at the 4th half –life. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Put the white “stable” atomic beans into the storage bowl with the other “stable” atoms you had from before. Set them all aside.

Take your shrinking number of black (or pink) “radioactive” beans and repeat the process for the 5th half –life. Make sure to pull out your “stable” white face-up atomic beans 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Do the same for the 6th, 7th & 8th half –life. Make sure to pull out your “stable” white face-up atomic beans 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives

Clean-up… Put all your 100 beans in your storage cup. Return to Mr. G

Questions (write answers in notes): Did all the graphs tend to look the same?

Questions (write answers in notes): Did all the graphs tend to look the same? About how many “radioactive, unstable” atoms decayed into more “stable” (white faced) atoms at each half-life?

Questions (write answers in notes): Did all the graphs tend to look the same? About how many “radioactive, unstable” atoms decayed into more “stable” (white faced) atoms at EACH HALF-LIFE?

THINK…. Let’s say the black (or pink) beans were radioactive Carbon-14 atoms. And let’s say it takes 5,730 years for HALF of your Carbon-14 to decay into stable atoms.

If you find a fossil with only about 50% of its expected Carbon-14, how old is it? 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% rate of decay 1 2 3 4 5 6 7 8 half-lives of CARBON-14 Each is 5,730 years.

the amount of carbon-14 has split in half ONCE, so that’s If you find a fossil with only about 50% of its expected Carbon-14, how old is it? 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% the amount of carbon-14 has split in half ONCE, so that’s ONE half-life. rate of decay 1 2 3 4 5 6 7 8 half-lives of CARBON-14 Each is 5,730 years.

the amount of carbon-14 has split in half ONCE, so that’s If you find a fossil with only about 50% of its expected Carbon-14, how old is it? 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% the amount of carbon-14 has split in half ONCE, so that’s ONE half-life. rate of decay 5,730 years old 1 2 3 4 5 6 7 8 half-lives of CARBON-14 Each is 5,730 years.

THAT’S WHY We use radioactive Cesium-137 as our WORLD CLOCK! check our phones! RADIOACTIVE ATOMS DECAY in NEAR PERFECT TIME. THAT’S WHY We use radioactive Cesium-137 as our WORLD CLOCK!

Compare all your graphs again!

After you die, HALF of your radioactive CARBON-14 atoms DECAY into more stable nitrogen atoms EVERY 5,730 years. decay On average, HALF your unstable carbon-14 atoms change into a normal nitrogen atom every 5,730 years.

After you die, HALF of your radioactive CARBON-14 atoms decay into more stable nitrogen atoms EVERY 5,730 years. decay On average, HALF your unstable carbon-14 atoms change into a normal nitrogen atom every 5,730 years. decay So if the preserved remains of this mammoth has only HALF the C-14 as today’s elephant, it is 5,730 years old!

After you die, HALF of your radioactive CARBON-14 atoms decay into more stable nitrogen atoms EVERY 5,700 years. decay On average, HALF your unstable carbon-14 atoms change into a normal nitrogen atom every 5,730 years. So if the preserved remains of this human has only 1/4th the C-14 as today’s human, it is _________ years old!

After you die, HALF of your radioactive CARBON-14 atoms decay into more stable nitrogen atoms EVERY 5,730 years. On average, HALF your unstable carbon-14 atoms change into a normal nitrogen atom every 5,730 years. decay So if the preserved remains of this human has only 1/4th the C-14 as today’s human, it is 11,460 years old! 2 x 5,730 = 11,460

After you die, HALF of your radioactive CARBON-14 atoms decay into more stable nitrogen atoms EVERY 5,730 years. decay On average, HALF your unstable carbon-14 atoms change into a normal nitrogen atom every 5,730 years.

Each time HALF the radioactive atoms decay, we call that a HALF-LIFE! For carbon-14 that is every 5,730 years. 5730

It takes 5,730 years for a half –a-piece of Carbon-14’s to decay. 5730 5730

It takes 5,730 years for a half –a-piece of Carbon-14’s to decay. 5730 5730

Carbon-14’s half-life is 5,730 years! Number of half-lives Percent (%) of Carbon-14 How many years go by? 100% None 1 50% or half 5,730 (1 x 5,730) 2 25% or ¼ (quarter) 11,460 (2 x 5,730) 3 12.5% or 1/8th 17,190 (3 x 5,730) 4 6.25% or 1/16th 22,920(4 x 5,730)

Carbon-14’s half-life is 5,730 years! Number of half-lives Percent (%) of Carbon-14 How many years go by? 100% None 1 50% or half 5,730 (1 x 5,730) 2 25% or ¼ (quarter) 11,460 (2 x 5,730) 3 12.5% or 1/8th 17,190 (3 x 5,730) 4 6.25% or 1/16th 22,920(4 x 5,730) We sometimes refer to this ABSOLUTE dating as CARBON-dating.

Half of radioactive uranium-235 (U-235) changes into lead (Pb) every 704 million years!

Uranium-235 half-life is 704 million years! 704 MY

Uranium-235 half-life is 704 million years! 704 MY 704 MY

Uranium-235 half-life is 704 million years! 704 MY 704 MY

Uranium-235 half-life is 704 million years! Number of half-lives Percent (%) of Uranium-235 How many years go by? None 1 50% or half 2 1,408 million years 3 12.5% or 1/8th 4 2.816 billion years

Radioactive absolute dating measuring multiple samples of Carbon -14 or Uranium-235 in fossils and rocks gets pretty exact .

Trosclair’s worksheet…

Bill Nye fossils… Go over…end. https://www.youtube.com/watch?v=_xKPgqx5kX8

end 2015-16

By monitoring & measuring the decay of 14C & 235U into more stable atoms, WE CAN ABSOLUTELY DATE RECENT RELICS…

By monitoring & measuring the decay of 14C & 235U into more stable atoms, WE CAN ABSOLUTELY DATE RECENT RELICS… like this 42,000 year old mammoth

By monitoring & measuring the decay of carbon & uranium isotopes into more stable atoms, WE CAN ABSOLUTELY DATE RECENT RELICS… like this 42,000 year old mammoth found in ice!

By monitoring & measuring the decay of 14C & 235U into more stable atoms, WE CAN ABSOLUTELY DATE RECENT RELICS… we can ABSOLUTELY DATE ANCIENT FOSSILS & LAYERS OR ROCK like this 42,000 year old mammoth

By monitoring & measuring the decay of 14C & 235U into more stable atoms, WE CAN ABSOLUTELY DATE RECENT RELICS… we can ABSOLUTELY DATE ANCIENT FOSSILS & LAYERS Of ROCK like this 42,000 year old mammoth like this 155 million year old ichthyosaur from China.

We breakdown our Earth’s history according to MASS EXTINCTIONS with MAJOR GEOLOGICAL EVENTS! http://www.dailymail.co.uk/sciencetech/article-1340756/Massive-haul-20-000-ancient-fossils-China-life-Earth-bounced-biggest-mass-extinction-time.html

Absolute radioactive dating rules over relative superposition dating

Count out 100 white beans. If the 100 white beans were made of uranium-235, in 704 million years, how many of these beans would turn to lead-207? 50…because the half-life of uranium-235 is 704 million years.

Count out 100 white beans. If the white beans were made of uranium-235, in 704 million years, how many of these beans would turn to lead-207? 50…because the half-life of uranium-235 is 704 million years. Replace 50 white “uranium” beans with 50 black “lead” beans…

Half your uranium-235 isotopes have turned to lead in 704 million years. If the white beans were made of uranium-235, in 704 million years, how many of these beans would turn to lead-207? 50…because the half-life of uranium-235 is 704 million years. Replace 50 white “uranium” beans with 50 black “lead” beans… …now 704 million years have gone by.

Half your uranium-235 isotopes have turned to lead in 704 million years. THAT’S HALF-LIFE! If the white beans were made of uranium-235, in 704 million years, how many of these beans would turn to lead-207? 50…because the half-life of uranium-235 is 704 million years. Replace 50 white “uranium” beans with 50 black “lead” beans… …now 704 million years have gone by.

How old would your sample be if you only found 25 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs.

How old would your sample be if you only found 25 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 2 half-lives or…

How old would your sample be if you only found 25 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old.

How old would your sample be if you only found 12 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old. 25%12.5% uranium-235 atoms =

How old would your sample be if you only found 12 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old. 25%12.5% uranium-235 atoms = 3 half-lives or

How old would your sample be if you only found 12 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old. 25%12.5% uranium-235 atoms = 2,112,000,000 years old.

Each time 704 million years go by… Uranium-235 isotope atoms decrease by half!

How old would your sample be if you only found 6 white “uranium” beans? Remember, the half-life of uranium-235 is 704 million years.

How old would your sample be if you only found 6 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old. 25%12.5% uranium-235 atoms = 2,112,000,000 years old. 12%6% uranium-235 atoms left = ???

How old would your sample be if you only found 6 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old. 25%12.5% uranium-235 atoms = 2,112,000,000 years old. 12%6% uranium-235 atoms left = 4 half-lives or..

How old would your sample be if you only found 6 white “uranium” beans? 100%50% uranium-235 atoms= 704,000,000 yrs. 50%25% uranium-235 isotope = 1,408,000,000 yrs old. 25%12.5% uranium-235 atoms = 2,112,000,000 years old. 12%6% uranium-235 atoms left = 2,816,000,000 years old!

10050=704 mya 5025=1.408 bya 2512=2.116 bya 126=2.824 bya

Separate your beans! Count out 48 black beans.

Your 48 black beans represent 48 nitrogen atoms today.

Let’s assume that when a snorlax dies, it dies with 25% of its tissue contain- ing carbon-14. Replace 25% of your black nitrogen beans with white carbon-14 atom beans.

How many of a snorlax’s 48 nitrogen “atoms” would be carbon-14? Let’s assume that when a snorlax dies, it dies with 25% of its tissue contain- ing carbon-14. How many of a snorlax’s 48 nitrogen “atoms” would be carbon-14?

Let’s assume that when a snorlax dies, it dies with 25% of its tissue contain- ing carbon-14. How many of a snorlax’s 48 nitrogen “atoms” would be carbon-14? (.25 x 48 = ????

Let’s assume that when a snorlax dies, it dies with 25% of its tissue contain- ing carbon-14. How many of a snorlax’s 48 nitrogen “atoms” would be carbon-14? (.25 x 48 = 12)

Replace 12 of your 48 nitrogen “atoms” with 12 white carbon-14 isotopes.

Replace 12 of your 48 nitrogen “atoms” with 12 white carbon-14 isotopes. Now you have a new sample of fresh snorlax tissue! With its 25% carbon-14 isotopes

If white beans are Carbon-14 with a half life of 5730 years, how old is your snorlax fossil if you found only 6 white bean carbon-14 atoms amongst 42 nitrogen atoms?

Remember C-14 has a half-life of 5,730 years. 12 atoms6 atoms= # cut in half…HALF-LIFE

12 atoms6 atoms= 5,730 years…HALF-LIFE If white beans are Carbon-14 with a half life of 5730 years, how old is your snorlax fossil if you found only 6 white bean carbon-14 atoms amongst 45 nitrogen atoms? 12 atoms6 atoms= 5,730 years…HALF-LIFE

12 atoms6 atoms= 5,730 years…HALF-LIFE If white beans are Carbon-14 with a half life of 5730 years, how old is your snorlax fossil if you found only 3 white bean carbon-14 atoms amongst 45 nitrogen atoms? 12 atoms6 atoms= 5,730 years…HALF-LIFE

If white beans are Carbon-14 with a half life of 5730 years, how old is your snorlax fossil if you found only 3 white bean carbon-14 atoms amongst 45 nitrogen atoms? 12 atoms6 atoms= 5,730 years…HALF-LIFE 6 atoms 3 atoms = # cut in half…2nd HALF-LIFE

If white beans are Carbon-14 with a half life of 5730 years, how old is your snorlax fossil if you found only 3 white bean carbon-14 atoms amongst 45 nitrogen atoms? 12 atoms6 atoms= 5,730 years…HALF-LIFE 6 atoms 3 atoms = 11,460 years (2 half-lives)

126= 5730 years 63=11,460 years

What if your snorlax fossil had 9 carbon-14 isotopes in it? 126= 5730 years 63=11,460 years

What if your snorlax fossil had 9 carbon-14 isotopes in it? 126= 5730 years 63=11,460 years W’huh? 9

What if your snorlax fossil had 9 carbon-14 isotopes in it? 126= 5730 years 63=11,460 years W’huh? 9 Is it older than 5,730?

What if your snorlax fossil had 9 carbon-14 isotopes in it? 126= 5730 years 63=11,460 years Hmm. 9 Is it older than 5,730?

What if your snorlax fossil had 9 carbon-14 isotopes in it? 126= 5730 years 63=11,460 years I do not think so. 9 Is it older than 5,730? NO!

Look at a number line…

126= 5730 years

126= 5730 years ½ way

126= 5730 years; 129 = 5730/2 ½ way

126= 5730 years; 129 = 2865 yrs old. ½ way

A mammoth skin has been found with 0.002% of carbon-14… If most animal tissue today dies with 0.064% carbon-14, And the half life of the carbon-14 isotope is ____________ years.

A mammoth skin has been found with 0.002% of carbon-14… If most animal tissue today dies with 0.064% carbon-14, And the half life of the carbon-14 isotope is 5,730 years. Half of any remaining carbon-14 turns into nitrogen.

A mammoth skin has been found with 0.002% of carbon-14… If most animal tissue today dies with 0.064% carbon-14, And the half life of the carbon-14 isotope is 5,730 years. Half of any remaining carbon-14 turns into nitrogen. How many years would have gone by if carbon-14 levels are .032%?

A mammoth skin has been found with 0.002% of carbon-14… If most animal tissue today dies with 0.064% carbon-14, And the half life of the carbon-14 isotope is 5,730 years. Half of any remaining carbon-14 turns into nitrogen. How many years would have gone by if carbon-14 levels are .032%? Is it possible that this mammoth breaks the record for the most recent mammoth of 30,000 years ago?

Actually the most recent evidence of mammoth living on earth is 4,500 years ago. What would you expect the percent of carbon-14 in this mammoth sample?

Actually the most recent evidence of mammoth living on earth is 4,500 years ago. What would you expect the percent of carbon-14 in this mammoth sample? Assume tissue has 0.0064% carbon-14 at time of death.

Carbon-14 actually makes up 1/1,000,000,000 of carbon in living tissue. Now, with C-14 only being about one one-trillionth of the carbon in an object, it might seem that there would only be a few such atoms in a sample. Nope! A one-pound piece of wood contains about half a pound of carbon. Using Avogadro's number, we can calculate that there are around 1.1 * 1025 atoms of carbon in it. one one-trillionth of that is 1.1 * 1013 atoms of Carbon-14. That is 11,000,000,000,000 atoms of Carbon-14 in that single chunk of wood! It turns out that around 3,800 of those C-14 atoms would decay every minute, plenty to be measurable!

Clean-up.

Use Kollar bricks to do another radioactive dating problem.