Why You Should Love Density | Will Grover | TEDxUCR
Summary
TLDRIn this engaging talk, the speaker shares personal anecdotes about the scientific curiosity instilled by his scientist parents, leading to a fascination with density. He explains how density, a measure of mass per unit volume, can reveal hidden properties of objects, from distinguishing healthy from sick cells to identifying materials. The speaker's work at MIT and UC Riverside explores using density to detect diseases like malaria, assess the effectiveness of cancer drugs, and monitor environmental health. The potential applications of density measurements are vast, from medical diagnostics to environmental safety.
Takeaways
- đšâđŹ The speaker, a scientist, shares personal anecdotes about growing up as the child of scientists and how they conducted experiments on him.
- đŹ The speaker demonstrates the concept of density through an experiment with two cubes that look identical but have vastly different weights, illustrating the importance of density in distinguishing objects.
- đ§ Density is defined as mass divided by volume, and it provides more information than either mass or volume alone, which is crucial for understanding the properties of objects.
- đ Density varies widely on Earth, from 0 g/mL for gases to 22-23 g/mL for the densest elements like osmium and iridium.
- đ The density of gases like helium and air is used to explain why helium-filled balloons float, demonstrating density's practical applications.
- đ ïž Density can be used to identify substances, as shown by the difference between aluminum and tungsten blocks, which look similar but have distinct densities.
- đș The historical example of Archimedes using density to determine the composition of the king's crown is recounted, highlighting the age-old utility of density measurements.
- đïžââïž Density measurements are relevant to health and biology, such as assessing body fat percentage and distinguishing between healthy and diseased cells.
- 𧏠The speaker's research at MIT involved using density to differentiate between healthy and sick cells, including those affected by malaria or cancer, showcasing density's role in medical science.
- đ Current research at UC Riverside explores the potential of density measurements in zebra fish embryos as an early warning system for environmental toxins, indicating density's broader ecological applications.
Q & A
What is the significance of the two cubes in the speaker's story?
-The two cubes, although identical in appearance, differ significantly in weight, with one being almost ten times heavier than the other. This demonstrates the concept of density, which is a key theme in the speaker's narrative about distinguishing between similar-looking objects.
How did the speaker's son react when he was given the two cubes?
-The speaker's son was surprised by the difference in weight when he was handed the second cube, which was much heavier despite looking identical to the first one.
What property of the cubes is used to distinguish between a healthy and a sick cell?
-The property that distinguishes between the heavy and light cube, as well as between a healthy and sick cell, is density. The speaker discovered that density can be used to identify differences in cells that are not apparent through size and shape alone.
What is the range of densities encountered on Earth according to the speaker?
-The range of densities on Earth spans from 0 grams per milliliter for gases like helium to about 22 or 23 grams per milliliter for the densest elements, such as osmium and iridium.
Why does the helium-filled balloon rise when released?
-The helium-filled balloon rises because helium is less dense than air. According to the principle of buoyancy, objects with a lower density than the surrounding medium will rise.
How did Archimedes determine if the king's crown was made of pure gold?
-Archimedes determined the purity of the king's crown by measuring its density. He compared the measured density of the crown to the known density of pure gold. If the densities matched, it indicated the crown was made of pure gold.
What method did the speaker's team use to measure the mass of single cells?
-The speaker's team used a suspended microchannel resonator, a tiny mass sensor similar in principle to a baby bouncer, to measure the mass of single cells. This device allowed them to determine the cell's density by measuring its mass in two different fluids.
How does the density of red blood cells change when infected with malaria?
-When red blood cells are infected with the malaria parasite, they become less dense. The parasite consumes hemoglobin, which results in a less dense form, thus reducing the overall density of the infected cells.
What insight can be gained from measuring the density of cancer cells after drug treatment?
-Measuring the density of cancer cells after drug treatment can reveal changes that indicate the cells' response to the drug. An increase in density post-treatment suggests the drug is affecting the cells, potentially serving as a screening tool for drug efficacy.
What potential application does the speaker suggest for density measurements in zebrafish embryos?
-The speaker suggests that density measurements in zebrafish embryos could serve as an early warning system, akin to a 'canary in a coal mine,' to detect harmful chemicals in water or air by monitoring changes in the density of the embryos.
Outlines
đŹ Introduction to Density and Its Impact on Our World
The speaker begins by sharing a personal anecdote about his experience as a child of two scientists, who often conducted science experiments on him. He demonstrates the concept of density through an experiment with two cubes that appear identical but have vastly different weights, one being almost ten times heavier than the other. This leads to a discussion on how density, defined as mass per unit volume, can reveal hidden properties of objects. The speaker connects this concept to his work at MIT, where he explored the possibility of distinguishing between healthy and sick cells based on their densities, which was a breakthrough in his research.
đș Historical and Practical Applications of Density
The speaker delves into the historical application of density by recounting the story of Archimedes, who was tasked with determining the purity of a crown. Archimedes discovered a method to measure density without destroying the object by weighing it in water and air. This method is still in use today, as exemplified by the speaker's reference to a modern athlete being weighed underwater to calculate her density. The speaker then explains how density can indicate health conditions, such as body fat percentage, and sets the stage for discussing how this principle can be applied to single cells.
𧏠Measuring Cellular Density: A New Frontier in Biology
The speaker describes the challenges and methods used to measure the density of single cells, which are too small to be weighed on conventional scales. He introduces a suspended microchannel resonator, a tool developed at MIT, which uses the oscillation frequency of a tiny 'diving board' to determine the mass of cells. By measuring the mass of cells in two different fluids, the density of the cells can be calculated. The speaker discusses how this technology can be used to identify cells infected with malaria or to assess the effectiveness of cancer drugs by observing changes in cell density.
đ Density as an Indicator of Health in Zebrafish Embryos
In the final paragraph, the speaker shares recent research from his lab at UC Riverside, where they are studying the density of zebrafish embryos to detect potential toxins in the environment. He explains that changes in the buoyant mass, which is a function of density, can indicate the health of the embryos. The speaker envisions a future where density measurements could serve as an early warning system for environmental hazards, akin to a canary in a coal mine, providing a non-invasive method to monitor the safety of air and water.
Mindmap
Keywords
đĄDensity
đĄMass
đĄVolume
đĄArchimedes
đĄSuspended Microchannel Resonator
đĄHealth and Disease
đĄCancer Cells
đĄZebrafish Embryo
đĄEnvironmental Toxins
đĄEpiphany
Highlights
The speaker and his wife, both scientists, conducted science experiments on their children, including a demonstration with two cubes of different densities.
One cube was almost 10 times heavier than the other, despite their similar appearance.
The property that made one cube heavier was the same property found in cells to distinguish between healthy and sick cells: density.
Density is defined as mass divided by volume, providing more information than either mass or volume alone.
The range of densities on Earth varies from zero grams per milliliter for gases to 22-23 for the densest elements.
Density can determine whether an object floats or sinks, as illustrated by the helium balloon example.
The difference in density between aluminum and tungsten is what caused the surprise reaction to the two cubes.
Density can be used to identify the chemical composition of a material, as demonstrated with the cubes.
Archimedes used the principle of buoyancy to determine the density of the king's crown, a method still used today.
The speaker's team aimed to measure the density of single cells to distinguish between healthy and sick cells.
A suspended microchannel resonator was used to measure the mass of cells, inspired by the frequency principle of a baby bouncer.
Cells have a density between 1.0 and 1.2 grams per milliliter, with variations indicating different states or conditions.
Malaria-infected red blood cells were identified as less dense than healthy cells.
Cancer cells' response to drug treatment could be observed through changes in their density.
Density measurements of zebra fish embryos could indicate the presence of harmful chemicals in the environment.
The speaker envisions density measurements as a tool for early detection of environmental hazards, like a modern canary in a coal mine.
Density is a physical property that can reveal new perspectives on the world when measured accurately.
Transcripts
all right you know as he mentioned my
wife and I we met in Berkeley and we're
both scientists and one of the kind of
Occupational hazards of being the child
of two scientists like me and my wife is
that your parents like to perform little
science experiments on you from time to
time and uh I'll show you a couple of
those today uh if you'll let me and I'll
demonstrate one of them first this one I
did a few days ago with my son it
involved these two cubes shown here you
can see that they're similar size
similar shape similar colors to them
right and I handed the first one to my
son thle fine into his hand and he was
like okay Dad what are you doing and I
handed the second one to him thle and he
went whoa jeez and to prove it to you we
took a little photo of him like using a
little Teeter titer with them what he
realized was that the one on the right
there even though identical to the other
one is tremendously more heavy than the
first one it's almost 10 times heavier
if any of youall don't believe me after
the show tonight you're welcome to come
up and lift these for yourself it's not
the kind of thing that makes a good
visual demo but trust me and so he send
that and in looking at these cubes he
realized that a whole new window had
opened up on the World to in some way
that you could have two objects that
look so similar to each other in every
describable way and yet when you feel
them when you pick them up you can tell
something's wrong something's very
different about this one versus this one
what is that thing what is this like
secret invisible world of objects that
we've never seen before this point I
loved watching him have that kind of
little Epiphany because it was really a
lot like what I had about five or six
years earlier I was a postto at MIT at
the time and I was in a lab where we
were trying to measure single cells and
in particular trying to see is there any
way you could tell the difference
between a healthy cell and a sick cell
based on these measurements and you know
just like these cubes often these cells
would look very similar to each other in
terms of their size and their shape and
their appearance and we needed to find
ways properties of these cells that you
could measure and use to distinguish a
healthy cell from a sick cell what could
that be well turns out in the story I'm
here to tell you tonight is that the
very property of these two cubes that
makes one so ridiculously heavy and the
other one feels so light the very
property of these cubes is the same
property we found of living cells that
lets us tell whether a cell is sick or
healthy and that property is density you
remember density right if you're like I
was five or six years ago you learned it
in high school and hadn't thought much
about it since then right well hopefully
by the end of tonight I can show you why
it's the most awesome physical property
and you should really appreciate and
love density uh so you might remember
that density is the function of two
other physical properties of an object
namely their Mass how much an object
weighs and its volume how much space a
little object occupies and you'll agree
that both of those measurements mass and
volume they're just ways of telling you
how much of an object you have how big
is it but when you divide the two by
each other when you take the mass and
divide it by the volume you get the
density and that's a whole other thing
it tells you so much more than either of
mass or volume can tell you on their own
I'll try to give you a few examples of
that today so first we're going to talk
about density for a few minutes we might
as well acquaint ourselves with the
range of densities that we encounter
here on Earth they range from zero grams
per milliliter all the way up to about
22 or 23 for the most dense elements
osmium and aridium and so we can look at
a few spots on this little number line
and see what the densities of a few
things are on the far left hand side
here we see the density of gases like
helium point 00002 G per Miller and air
0013 G per Miller these are all very low
densities but you notice helium is just
a little less dense than air and that is
why when we fill a balloon with helium
and let go of it it goes up so this sort
of the first example of density giving
us something meaningful in our
interpretation of the world around us in
this example what determines when I let
something go whether it goes down or up
it's density if it's more dense than
what's around it it'll go down if it's
less dense than what's around it like
the balloon it'll go up so a little
example of density telling us something
about the world around us let's go up
the scale a little bit further around
2.7 we encounter aluminum Nice metal and
then way up at 19.2 on the density scale
we encounter tungsten and that is what
these two blocks are made of and that
difference the difference in density
between 2.7 aluminum aluminum can very
light and tungsten one of the densest
elements uh that's known uh is the
reason why my son reacted to these and
being so different and so there's
another Insight that density can give us
I could walk up on those on these blocks
and by looking at them I couldn't tell
you which is tungsten and which is
aluminum but if you let me pick them up
and if I know these density numbers then
it's very easy for me to tell that this
is tungsten and that's aluminum so here
density a physical property is giving us
a way to identify chemically what
material an object's made of pretty neat
that idea of using density to identify a
substance is not an old not a new one in
fact over 2,000 years ago Archimedes was
asked in the story by the king to
determine whether one of the king's
crowns was made of pure gold or not and
so Archimedes was a smart man and he
realized if he could measure the density
of the crown and compare that to the
known density of pure gold which is 19.3
very dense if they equaled then it
proved that the crown was made of pure
gold but if they were different it meant
that the king had been swindled by the
crown maker I guess and so by measuring
density he knew he could easily tell the
difference between pure gold at 19.3 and
something like iron pyite fools gold at
5.0 but Archimedes face a challenge how
do you measure the density of an object
like a crown right I told you density is
mass divided by volume now getting the
mass of the crown is easy enough you
just weigh it but how do you measure the
volume of the crown without destroying
it or melting it down in a way he needed
a way to measure the density of the
crown without destroying it what he came
up with was really one of the most I
think brilliant experimental ideas in
the history of Science and this is what
it is he realized that he could weigh
the crown underwater if you've ever been
in a pool you know you weigh a little
less under water than you do standing on
dry land right well how much less do you
weigh well the way the math works out
the amount that different that you weigh
in the water is a function of two things
the density of the water which is one we
know that and the density of youu the
object that we're weighing or the crown
so if we weigh an object like a crown in
two different fluids in this example in
water and air from those two weight
measurements we can calculate the
density of the crown that's exactly what
Archimedes did and he was able to
determine what the crown was made of so
now amazing ly 2,000 years later we
still do exactly what Archimedes
described so long ago in this example
this athlete here is being weight
underneath the water and by combining
that measurement with the second
measurement of her weight on on dry land
we'd be able to calculate her density
why do you need to know a person's
density Well turns out along with
telling you what a cube is and all these
different things it can tell you if
you're fat or thin uh you've heard the
expression fat floats and it does if you
have a lot of fat in your body that
reduces your net density down to about
1.0 1 or so if you have a lot less fat
bone and muscle and things are more
dense so that makes your body more dense
and you reach about 1.07 or 1.08 so
here's our first example of density
remember a physical property telling us
something very biological very health in
nature in this case how fat or how thin
a person could be all from density so
back five or six years ago as a postto
we looked at this and saw all the things
density could tell you and we had a
thought what if it worked just as well
on single cells what if just just like I
could measure the density of a human
body and tell things about the health of
the body could I possibly measure single
cells and infer things like the
difference between a healthy cell and a
sick cell or a cancerous cell based on
this density measurement so we set out
to try to do that and the first
challenge was what we need to measure
the density of a cell which hadn't
really been done before and we realized
we could use the method that Archimedes
described the idea of weighing it in two
fluids of different density but how do
you weigh a cell you might first turn to
this if it's in your your your kitchen
uh but but I can tell you cells are a
whole lot too small to weigh on this and
and Tiny living cells don't take too
kindly to being plunked down onto a
little kitchen scale so we needed a way
to measure the extremely tiny mass of
cells in order to figure out what their
density was how do we do that well
luckily the lab I joined as a as a
postto already had a little MTH sensor
that they worked on that was perfect for
this job and to explain to you how it
works I'll show you another experiment I
performed on one of my children uh this
this is Jack he's uh a little jerky up
there but he's a lot smoother than that
in real life Jack is it looks like he's
on a baby bouncer and he is on a baby
bouncer but it's also a sophisticated
mass sensor believe it or not you see
the frequency at which he's bouncing up
and down as he kicks his legs there he
can't just control that frequency it
will that's actually a fixed frequency
it's a function of a few things that
determine it but crucially it's a
function of his Mass so if he were to
say sit there and eat a hamburger uh
that frequency would slow down because
his Mass would have gone up that's how
it works so my wife and I again in this
in the spirit of experimenting on our
children realized we had an unexpected
mass sensor here and we decided to
calibrate it first so we put some
weights of known weights on it uh from
our weight set ranging from this is
perfectly normal ranging from 5 PBS
which had the highest frequency of
oscillation 149 beats per minute all the
way to the highest weight 20 pounds on
the bouncer which had the slowest
frequency of oscillation only 88 beats
per minute now that we've calibrated it
like a good scientist if you're if
you're preparing lab notebooks for of
your lab courses remember got a good
calibration curve show my data Etc
you've done you calibrated our mass
sensor now we're able to put jack back
in it and measure his frequency and
determine what his weight is 20 pounds
and then do the same for his identical
twin brother Henry and see that he has a
slightly lower frequency which means he
has a slightly higher mass and indeed
that's exactly true so here you see uh
this sensor is so fantastic we have a
baby bouncer that's capable of
distinguishing two identical twins from
each other even I can't do that most
days and I'm their father
so this measurement principle is really
quite good uh as a way to weigh
something it turns out you'll never look
at a baby bouncer again the same way I
hope so here's the here's the point if
you take that baby bouncer and scale it
down I mean way way down so that the
bouncing part is about the size of a
human hair at that point you're able to
put a cell on it instead of Jack or
Henry and do the same measurement and
weigh them and that's what this tool
here does this was developed at MIT in
the lab before I joined it they call it
a suspended microchannel resonator and
at the heart of it is a tiny little
bouncer a little diving board shaped
thing that you can see here and it
oscillates like that if we look inside
of it we don't actually put the cells on
the outside of it we Slide the cells on
the inside and this little blue Channel
shown there if you zoom in on it that's
the sensor it's oscillating and when we
send a cell like this little red blood
cell through we weigh the cell basically
so by measuring two cell masses and two
fluids of different density we can
calculate the density of the cell long
story short so there that's how we do it
what is the density of a cell after all
that is this even interesting and what
we found we've measured a bunch of cells
and we found that most cells have a
density between 1.0 and 1.2 gram per
Miller and on one hand that's not too
surprising because water has a density
of 1.0 and cells are mostly water so it
makes sense that we would see values
around that number but not all cells
have the same density and I'll give you
just a few examples tonight of how the
density of a cell can be used to
determine something very interesting and
get some insights about the cell here's
the first example this plot here shows
each black dot is the measurement of a
single red blood cell from someone's
blood on the bottom you can see what the
density of those cells are ranging
around 1.10 1.12 on the side here you
can see the weight of each of those
cells in picograms if you don't know
picograms or wonder how much a cell
weighs a millionth of a millionth of a
gram very very small weights and so in
healthy blood cells we can see all of
those measurements kind of pile up into
that little oval region that's where we
expect them to go but if you do the same
measurement on cells that part that some
of them are infected with malaria
parasite uh we see a few cells over
there to the left that are a little less
dense than the healthy cells those are
the cells that are infected with malaria
it's been known for a while that the
little parasite that is malaria eats up
the hemoglobin in your red blood cells
turns it into a form that's less dense
and the result of that is an infected
cell becomes less dense and we can see
that and we can identify the infected
cells compared to the healthy cells
based on their density what else here's
data showing the mass and volume of
cancer cells these are leukemia cells
from a mouse and you're seeing in the
black points the measurements before we
treat them with a drug and in the red
points the measurements after we treat
them with an anti-cancer drug and if you
look just at the mass and volume of the
cells before and after black and red you
don't see much of a change and in fact
if this data was all you had to go by
you might not have thought that drug was
any good but like I said density is mass
divid by volume if you do that math for
each one of these points you get this
story over here a very much clearer
picture we see that after treatment just
minutes after we dose these cells with a
drug we see that uh a large number of
the cells have increased in their
density by a large statistically
significant amount what this means is
that just minutes after treating these
cells with a drug we can see that yeah
those cancer cells are reacting to that
drug we hope that eventually this could
become a drug screening tool you might
be able to use that density change as a
way to find new cancer drugs based on
whether or not the cell's density
changes when they encounter the drug
and then I can finish with just a little
uh recent data from my lab here at UC
Riverside this is showing the buoyant
Mass which is a function of density of
single zebra of a single zebra fish
embryo why we're studying zebra fish
well a few reasons uh zebra fish embryos
are an aquatic organism and so if
something hurts a zebra fish embryo like
a chemical then there's reason to think
that it would hurt a lot of other fish
and it's probably the kind of chemical
you'd want to not have in your waterways
and two a zebra fish embryo looks a lot
like a human embryo so so if something
hurts a zebra fish embryo there's a good
reason to think that you wouldn't want
to have it around any of your embryos
either so this is what the mass buoyant
mass or density of a healthy zebra fish
looks like over time and then if we do
the same measurement on a sick zebra
fish that we've exposed to some chemical
that makes it ill we see a very
different reaction we see little
decreases in its buoyant Mass it means
its density is changing we don't know
what's causing this yet but what we do
know is that we've tried the same
experiment on a whole bunch of different
sorts of sicknesses different sorts of
toxicants for these zebra fish and we
still see the same signature it's as if
this change is somehow indicative of of
of a sick zebra fish regardless of
exactly what we did to make it ill and
so where we want to see this going in
the future is you're familiar with the
idea of a canary and a coal mine right
uh the the the bird that the coal miners
brought down to see if the air was safe
to breathe we hope that the density
measurements that we're making right now
will in the future become like a sort of
super Canary in a coal mine that by
measuring the density of these organisms
of these embryos or or other
microorganisms we could have an
instrument that will live and Sample the
groundwater and tell you if there's
something dangerous entering into it or
an instrument that can live in the air
and Sample the air around us and tell us
if there's something dangerous all based
on how the density of these organisms
react to exposure to whatever is in the
environment that's one direction we're
taking it so hopefully today I showed
you and shared with you why I think
density is just the most awesome
physical property that's out there it's
something that every object around here
from crowns to cell to fish to you and
me we all have a density we can't see it
but we can feel it and we can measure it
and if you can measure it accurately
enough you can use it to sort of open up
whole new views on the world around you
thank
[Applause]
you
5.0 / 5 (0 votes)