AUs

become meaningless for measuring greater distances

outside the solar system

Units In Space

Techniques for Indirectly Measuring Distance

**Measuring Distances in Space**

Just how big is space?

The universe is

astronomically

big.

Scale of objects in the universe

Larger units

are used to measure distance in space

AU

(Astronomical Units)

An

Astronomical Unit (AU)

is a unit used to measure distance

within the

Solar System

One

AU

is the distance from the

Earth

to the

Sun

1 AU = 150 million km

Light-Years

A

light-year

measures

distance

, not time

One

light-year

is how far

light

can travel in

one year

Light

moves at a speed of

300 000 kilometres per sec.

300 000 km × 60sec × 60min × 24hr × 365d

= approximately

9.5 trillion km

One

light-year

is approximately

9.5 trillion km

Distances between planets and stars are unimaginably far

They

cannot be measured

in

regular units

such as metres.

These units are called

AU's, Light-years

and

parsecs

What is

Triangulation?

Parallax

we better get a good mark on this prezi

Light

travels

faster

than anything else we know.

Andromeda Galaxy

2.5 million

light-years away

From the Earth to the Edge of the Solar System

50 000 to 100 000 AUs

**point A**

**point B**

Take a good look at this star

Did you notice the shift?

You have just observed

parallax

This star never moved.

It

appeared

as if it had

shifted

because of the

change

in the

observer's

position

Light-years

are used

to measure even greater distances than

AUs

but

light

from this galaxy must travel for

2.5 million years

to reach Earth.

We've looked at

units

for measuring

vast distances

in space.

But,

HOW

do we measure something

that

cannot be reached?

Triangulation

and

Parallax

can be used to measure distances to any

visible object

that we cannot reach

thank you matt c

It is a method that uses

a

scale diagram

of a

triangle

to

indirectly measure

distances to stars

Steps of

triangulation

Here is a tree.

If humans are 1

on this scale,

The observable universe is about

100 000 000 000 000

000 000 000 000

This person wants to measure the distance to the tree.

Step 2.

At the end of the

baseline

,

measure the

angle

to the tree with a

protractor

35°

30°

Step 3.

Measure the

angle

from the opposite end of the

baseline

to the tree

Step 1.

Measure and draw a straight

baseline

(ex.120m)

Parallax

is the

apparent shift

of an object against a

stationary background,

Step 4.

Draw a

scale

diagram

with the

baseline

and

angles

Ratio = 10m : 1cm

12 cm

35°

30°

Astronomers

can use the

Earth's orbit

and

parallax

to calculate distance to stars

caused by a

change in the position of the observer

.

Baseline

angle A

angle B

Parallax

comes from the greek word

Which means

"Alteration"

(parallaxis)

=

3.7 cm

3.7 cm x 1000 = 3700cm = 37m

The distance to the tree

is

37 meters.

With these angles, you can use

triangulation

to find the distance

to the star

The longer the

baseline

of the triangle,

The calculations become more

accurate

.

the easier it is to measure the

angles

.

Triangulation

and

parallax

are only accurate

when objects

being measured are within

500 light-years away

Astronomical Units (AUs)

and

light-years

are used to

measure

distance in space

Triangulation

and

parallax

can be used to determine the distance to

any visible object

In conclusion,

Q

. Why

do astronomers use

Earth's full orbit

as their

baseline

?

A

. They must use the

longest possible baseline

to get the most

accurate measurements

.

Thank you for watching.

A parsec is a basic unit of length for measuring distances to stars and galaxies, equal to 206,265 times the distance from the earth to the sun, or 3.26 light-years.

The nearest star, Proxima Centauri is about 1.31 parsecs from the Earth.

Parsec