How big is the universe ... compared with a grain of sand?

Summary

This script explores the vastness of the universe, challenging human comprehension. It discusses astronomical methods like Parallax and standard candles to measure distances to stars. The script introduces the light year as a unit for cosmic distances and explains how observing stars is like looking back in time. It highlights the Milky Way and Andromeda galaxy, emphasizing the universe's enormity with the Hubble telescope's view of thousands of galaxies in a tiny patch of sky. The script concludes with a metaphor comparing the size of the universe to grains of sand, emphasizing its immensity.

Takeaways

• 🌌 The universe is so vast that it's difficult for the human mind to comprehend its true size.
• 🔍 Astronomers use the Parallax technique to measure distances to nearby stars by observing their apparent shift in position against the background stars from different points in Earth's orbit.
• 🌟 Standard candles, stars with known intrinsic brightness, help astronomers calculate distances by comparing their apparent brightness to us.
• 🚀 Proxima Centauri, the nearest star to the Sun, is an incredible 40 trillion kilometers away from Earth.
• ⏱ A light year is a unit of distance that represents how far light travels in one year, which is about 9.46 trillion kilometers.
• 🕰 Looking at stars is like looking back in time; the light we see from the Sun is already 8 minutes old.
• 🌍 Our Sun is part of the Milky Way galaxy, which is just one of the countless galaxies in the universe.
• 🌌 The Andromeda galaxy, visible to the naked eye, is approximately 2.5 million light-years away, meaning its light has taken that long to reach us.
• 🔭 The Hubble telescope's deep field image revealed that every speck of light in the photo is a galaxy, indicating the vast number of galaxies in the universe.
• 🌠 The visible universe contains around 100 billion galaxies, each with about 100 billion stars, making the number of stars more than the grains of sand on Earth.
• 🌐 If the Earth were a grain of sand, the Milky Way galaxy would be a thousand times larger than Durham Cathedral, and the entire visible universe would be unimaginably vast.

Q & A

What is the human mind's capability in comprehending the vastness of the universe?

The human mind struggles to comprehend the true immensity of the universe due to its vast and enormous size.

What is Parallax and how is it used to measure distances to stars?

Parallax is a phenomenon where an object appears to shift position relative to a background when viewed from different angles. In astronomy, it's used to measure distances to stars by observing the apparent movement of a star against the background stars as Earth orbits the Sun.

How does the concept of 'standard candles' help in measuring astronomical distances?

Standard candles are stars with known intrinsic brightness. By measuring their apparent brightness as seen from Earth, astronomers can calculate their distance using the inverse square law of light.

What is the nearest star to the Sun and how far is it from Earth?

The nearest star to the Sun is Proxima Centauri, which is approximately 40 trillion kilometers or about 4.24 light-years away from Earth.

What is a light year and how is it used in astronomy?

A light year is the distance that light travels in one year, approximately 9.46 trillion kilometers. It is used as a unit of measurement for vast distances in space.

Why does the speed of light have a significant impact on our perception of the universe?

The speed of light impacts our perception of the universe because it determines how long it takes for light from distant objects to reach us. This means that when we look at distant stars or galaxies, we are effectively looking back in time.

How long does it take for light from the Sun to reach the Earth?

It takes about 8 minutes for light from the Sun to reach the Earth.

What is the significance of the Andromeda galaxy in relation to Earth?

The Andromeda galaxy is the farthest object visible to the naked eye and is another galaxy outside our Milky Way. The light from Andromeda takes about 2.5 million years to reach Earth.

What did the Hubble telescope reveal when it observed a seemingly ordinary patch of the night sky?

The Hubble telescope revealed that every speck of light in the observed patch was a galaxy, indicating that there are approximately 10,000 galaxies in a patch of sky the size of a grain of sand held at arm's length.

How many galaxies and stars are estimated to be in the visible universe?

The visible universe is estimated to contain around 100 billion galaxies, each with about 100 billion stars, making the total number of stars approximately 10,000 million million million.

How can the size of the universe be conceptualized in relation to familiar objects on Earth?

If the Earth were a grain of sand, the solar system would be as big as Durham Cathedral, and the Milky Way galaxy would be a thousand times bigger. If the Milky Way were shrunk to the size of a grain of sand, the entire visible universe would be the size of Durham Cathedral.

Outlines

00:00

🌌 Understanding the Universe's Scale

The paragraph introduces the immensity of the universe, which is beyond human comprehension. It explains the use of parallax to measure distances to stars by observing their apparent shift in position against the background stars from different vantage points on Earth. Additionally, it mentions the concept of 'standard candles,' stars with known luminosity, to calculate distances based on their observed brightness. The nearest star, Proxima Centauri, is highlighted as an example, being 40 trillion kilometers away. The paragraph also introduces the light year as a unit of measurement for such vast cosmic distances, defined as the distance light travels in a year. It concludes with a discussion on how the speed of light affects our perception of stars, essentially allowing us to look back in time, and a brief on the Milky Way galaxy and other galaxies visible to the naked eye, like Andromeda, whose light has taken over 2.5 million years to reach us.

05:00

🌟 The Staggering Number of Stars in the Universe

This paragraph delves into the sheer number of stars in the visible universe, comparing it to the number of grains of sand on Earth to emphasize the scale. It explains that each of the estimated 100 billion galaxies contains about 100 billion stars, leading to a total of 10,000 million million million stars. The concept of light traveling for 13 billion years from the most distant galaxies is introduced, illustrating the age and size of the visible universe. The paragraph concludes with a thought experiment comparing the Earth to a grain of sand, and then scaling up to the solar system, the Milky Way, and finally the entire visible universe, to give a sense of the universe's vastness.

Keywords

💡Universe

The universe, in the context of the video, refers to the vast expanse of space that contains all known matter and energy, including galaxies, stars, planets, and other celestial bodies. It is the central theme of the video, as it discusses the immensity of the universe and the challenges in comprehending its size. The script mentions that the universe is so vast that it is difficult for the human mind to comprehend, highlighting the awe-inspiring scale of the cosmos.

💡Parallax

Parallax is a phenomenon used by astronomers to measure the distance to stars. It is defined as the apparent shift in position of an object when viewed from different positions. In the video, parallax is explained through the simple act of holding up a thumb and looking at it with one eye and then the other, demonstrating how the thumb appears to move against a background. Astronomers use this effect to calculate the distance to nearby stars by observing their apparent movement against the background of more distant stars over six months as Earth orbits the Sun.

💡Standard Candles

Standard candles are stars with known intrinsic brightness that are used to measure astronomical distances. The term 'standard candles' is used in the video to describe a method where the actual luminosity of certain stars is known, and by observing how dim they appear from Earth, astronomers can calculate their distance. The video uses this concept to explain how the dimmer a star appears, the further away it is, which is a fundamental principle in measuring cosmic distances.

💡Proxima Centauri

Proxima Centauri is the nearest star to our Sun, located about 4.24 light-years away. In the video, it is mentioned as an example of a star whose distance is measured using astronomical methods. The script emphasizes the vastness of space by stating that Proxima Centauri is 40 trillion kilometers away, illustrating the scale of distances within our own cosmic neighborhood.

💡Light Year

A light year is a unit of distance used in astronomy, defined as the distance that light travels in one year. The video introduces the concept of a light year to help comprehend the immense distances in space. It explains that light travels about 9.46 trillion kilometers in a year, which is used to express the distances of faraway stars and galaxies. The video uses the light year to convey the idea that when we look at distant stars, we are looking back in time.

💡Milky Way

The Milky Way is the galaxy that contains our Solar System, consisting of billions of stars, planets, and other celestial objects. In the video, the Milky Way is used to give a sense of scale within the universe. It is mentioned that not everything visible in the night sky is part of the Milky Way, indicating that there are other galaxies beyond our own. The video uses the Milky Way to illustrate the vastness of the universe and the relative smallness of our own galaxy within it.

💡Andromeda Galaxy

The Andromeda Galaxy, also known as M31, is the closest major galaxy to the Milky Way and is visible to the naked eye. The video mentions Andromeda as the furthest object visible without a telescope, emphasizing the time it takes for light from this galaxy to reach Earth—approximately 2.5 million years. This example is used to illustrate the concept of looking into the past when observing distant celestial objects.

💡Hubble Telescope

The Hubble Space Telescope is an orbiting observatory that has provided some of the most detailed images of the universe. The video refers to the Hubble Telescope when discussing the observation of distant galaxies. It mentions the famous 'Hubble Deep Field' image, which captured thousands of galaxies in a small patch of sky, demonstrating the vast number of galaxies in the universe. The Hubble Telescope is a symbol of humankind's quest to see further and understand the cosmos.

💡Galaxy

A galaxy is a massive, gravitationally bound system consisting of stars, stellar remnants, gas, dust, and dark matter. The video discusses the concept of galaxies, particularly in the context of the number of galaxies in the universe. It explains that the visible universe contains around 100 billion galaxies, each with around 100 billion stars, highlighting the sheer number of stars in the cosmos. The video uses the term 'galaxy' to emphasize the scale and complexity of the universe.

💡Visible Universe

The visible universe is the part of the universe that we can observe from Earth, limited by the speed of light. The video discusses the concept of the visible universe to convey the idea that the universe is so vast that we can only see a small portion of it. It mentions that the visible universe stretches about 13 billion light years from Earth, which is the distance light has traveled since the Big Bang. This term is used to illustrate the limitations of our observations and the immense size of the universe.

💡Neptune

Neptune is the eighth and farthest known planet from the Sun in our Solar System. The video uses Neptune as a reference point to illustrate the scale of the universe. It suggests imagining the Earth as a grain of sand and then scaling the Solar System out to Neptune's orbit to be as large as Durham Cathedral, which is used to provide a relatable comparison for the unimaginable size of the universe.

Highlights

The human mind struggles to comprehend the vastness of the universe.

Astronomers use Parallax to measure distances to stars by observing apparent shifts in their positions.

Standard candles, stars with known brightness, help calculate distances based on their observed brightness.

Proxima Centauri, the nearest star to the Sun, is 40 trillion kilometers away.

Astronomers use light years, the distance light travels in a year, as a unit of measurement for vast cosmic distances.

The speed of light is approximately 300,000 kilometers per second.

Observing stars is like looking back in time, as the light we see has taken time to reach us.

The Milky Way is just one of many galaxies in the universe.

The Andromeda galaxy is the farthest object visible to the naked eye, with its light taking 2.5 million years to reach Earth.

Telescopes are metaphorically time machines, allowing us to see celestial objects as they were in the past.

The Hubble telescope revealed that a seemingly dark patch of sky contains thousands of galaxies.

The visible universe contains around 100 billion galaxies, each with around 100 billion stars.

There are more stars in the visible universe than grains of sand on Earth.

Light from the most distant galaxies has taken around 13 billion years to reach us.

The visible universe stretches about 13 billion light years from Earth.

An analogy compares the Earth to a grain of sand, with the solar system and galaxy scaled up accordingly to illustrate the universe's size.

The universe is incredibly large, with its size often being beyond human comprehension.

Transcripts

[Music]

you'll never ever get your head around

how big the universe is don't go there

it's just vast it's enormous there's no

way human mind I think can actually

comprehend the true immensity of the

universe we're happy with the size of an

elephant or the size of a tree or maybe

even the size of Durham

cathedral but I think if we go beyond

that then our brains just start to run

out a gas it may be difficult for our

brains to comprehend but that hasn't

stopped astronomers endeavoring to

measure the distance to the Stars One

technique is to use a phenomenon called

Parallax everybody can actually

experience Parallax for themselves if

you hold your thumb up and close one eye

you can see that your thumb appears to

be in a certain position relative to

something behind your thumb but then if

you open that eye and close the other

eye you'll see your thumb appears to

move relative to the object

behind the same thing happens when we

look at the stars when we look at a

relatively nearby star from the earth it

appears in a certain position relative

to the other background Stars 6 months

later when the earth is on the opposite

side of the Sun the same star will

appear in a different position relative

to the background like opening and

closing one eye then the other the star

appears to move and by measuring this

apparent Movement we can calculate the

true position of the

star an alternative method of

measurement is to use certain stars in

the sky known as standard

candles we know exactly how brightly

they shine if we can therefore measure

how bright they appear to us on Earth we

can calculate how far away they are the

dimmer they appear the further they are

from the earth so the nearest star to

the sun is Proxima centur and that it

turns out is 40 trillion kilm away

that's 40 million million kilomet away

from the earth such numbers start to

become

incomprehensible and that's why

astronomers have adopted an alternative

unit of measurement for such vast

distances the light year a light year is

the distance that light will travel in

one year if you imagine light moving

around the Earth in one second

so in that time light would travel

around the Earth over seven times so

that's fast speed of light is 300,000 km

a

second so one light here is about 9

million million

kilm the speed of light also leads to a

curious consequence when we stare at the

stars so the light from the sun takes 8

minutes to get to the Earth um that

Essen entally means we're looking into

the past we're looking back at the Sun

as it was 8 minutes ago if the sun was

to disappear right now we wouldn't know

for 8 minutes so a telescope if you like

is a time machine we're looking back in

time and the further the object is away

from us the further back in time we're

seeing it our sun like nearly all the

stars we can see with the naked eye sits

inside the Galaxy we call the Milky Way

but our galaxy is not alone in the

universe not everything you can see in

the night sky is actually in our galaxy

um it turns out that some of those faint

dots are in fact other galaxies the

furthest object you can see actually

with with the uned eye is another galaxy

called Andromeda the light from that

galaxy has taken something like two and

a qu million years to get to the Earth

so if you imagine if we reverse the

scenario and you're looking at the Earth

from Andromeda with a very powerful

telescope you'd see no signs of cities

no civilization no Great Wall of China

you might be lucky enough to see one or

two sort of early humans hunting around

on the African plains for their dinner

maybe astronomers have always wanted to

see further using bigger and better

telescopes to try and find out just how

many other galaxies are out

there until finally we pointed the

Hubble telescope at what at first

appeared to be a very dark and ordinary

patch of the night sky if you imagine

holding up your finger with a grain of

sand on it and looking at the patch of

sky that that grain of sand blocks out

that's the field that the telescope

zoomed in onto and what the telescope

saw was

incredible every single Speck of light

in this photo is a Galaxy 10,000

galaxies in a patch of Sky the size of a

grain of sand held at arms length if

this tiny patch of sky is like every

other then we can calculate how many

galaxies are out there the visible

Universe contains around 100 billion

galaxies each one of those galaxies

contains around about 100 billion stars

that means the visible Universe contains

something like 10,000 million million

million stars that means there are more

stars in the visible Universe than there

are grains of sand on the earth the

light from some of these most distant

galaxies has taken around 13 billion

years to get here that's light traveling

at 300,000 km a second the visible

Universe stretch is around 13 billion

light years from the earth so we've said

the universe is Big I'm going to try and

give you some idea how big imagine the

Earth as a grain of sand if that was the

case then our solar system out to the

orbit of the planet Neptune would be as

big as Durham

Cathedral so now let's imagine we take

our solar system and we shrink it down

to the size of this grain of sand then

our galaxy The Milky Way would be a

thousand times bigger bigger than this

[Music]

Cathedral so now we take the Milky Way

galaxy and shrink it down to the size of

the grain of sand the cathedral would be

the entire visible

Universe the universe is Big it's really

big

[Music]

[Music]