How far can I (one) see?

[blasos]

annodomini2 said:

Eric Mc said:

MLH said:

What provides the light source for this galaxy?

200 billion stars give or take the odd billion - plus glowing dust lanes.

1 Trillion according to Wikipedia, Andromeda is bigger than the Milky way.

According to a lot of sources it's in the region of 1 trillion. I've never seen 200 million being quoted before.

[Vipers]

SLCZ3 said:

You are actually only seeing to the photo receptors in your eyes, the light impinging on it , so you see the image that has crossed/travelled that distance over a period of time.
So clear as mud eh.

Bit like when you see the sun, you see it where it was about 9 minutes ago.

[finishing touch]

What staggers me, is that on a clear night we can see 2.5 million light years and yet, wait a few minuets,
and some one will drive by with their fog lights on.

[SpudLink]

finishing touch said:

What staggers me, is that on a clear night we can see 2.5 million light years and yet, wait a few minuets,
and some one will drive by with their fog lights on.

That's to make sure sentient beings in the Andromeda Galaxy can see them coming.

[ExplorerII]

Toltec said:

I forgot this was PH, yes, an AU is the mean distance from the sun as the term radius only strictly applies to circles or arcs of circles. In that this is the baseline used to define a Parsec rather than the diameter of the orbit I was correct. Unless you wish to get into a discussion about how an AU is actually defined and measured?

No, you were wrong, and no I do not want to get into a discussion with you.

[Vipers]

ExplorerII said:

Toltec said:

I forgot this was PH, yes, an AU is the mean distance from the sun as the term radius only strictly applies to circles or arcs of circles. In that this is the baseline used to define a Parsec rather than the diameter of the orbit I was correct. Unless you wish to get into a discussion about how an AU is actually defined and measured?

No, you were wrong, and no I do not want to get into a discussion with you.

As any school boy will tell you, an astronomical unit is a unit of length, roughly the distance from the Earth to the Sun. However, that distance varies as the Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year.

Originally, each distance was measured through observation, and the au was defined as their average, half the sum of the maximum and minimum, making the unit a kind of medium measure for Earth-to-Sun distance. It is now defined as exactly 149597870700 metres (about 150 million km, or 93 million miles).

The astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System. However, it is also a fundamental component in the definition of another critical unit of astronomical length, the parsec.

Simples

[ExplorerII]

Vipers said:

As any school boy will tell you, an astronomical unit is a unit of length, roughly the distance from the Earth to the Sun. However, that distance varies as the Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year.

Originally, each distance was measured through observation, and the au was defined as their average, half the sum of the maximum and minimum, making the unit a kind of medium measure for Earth-to-Sun distance. It is now defined as exactly 149597870700 metres (about 150 million km, or 93 million miles).

The astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System. However, it is also a fundamental component in the definition of another critical unit of astronomical length, the parsec.

Simples

Any school boy. Really? And well done you for Googling 'astronomical unit'

Edited by ExplorerII on Tuesday 16th December 12:07

Edited by ExplorerII on Tuesday 16th December 12:08

[Vipers]

ExplorerII said:

Vipers said:

As any school boy will tell you, an astronomical unit is a unit of length, roughly the distance from the Earth to the Sun. However, that distance varies as the Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year.

Originally, each distance was measured through observation, and the au was defined as their average, half the sum of the maximum and minimum, making the unit a kind of medium measure for Earth-to-Sun distance. It is now defined as exactly 149597870700 metres (about 150 million km, or 93 million miles).

The astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System. However, it is also a fundamental component in the definition of another critical unit of astronomical length, the parsec.

Simples

Any school boy. Really? And well done you for Googling 'astronomical unit'

Bugger, caught out, doh................... Well I tried. TBH I had absolutely what AU meant, now I do.

[Toltec]

Vipers said:

ExplorerII said:

Vipers said:

As any school boy will tell you, an astronomical unit is a unit of length, roughly the distance from the Earth to the Sun. However, that distance varies as the Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year.

Originally, each distance was measured through observation, and the au was defined as their average, half the sum of the maximum and minimum, making the unit a kind of medium measure for Earth-to-Sun distance. It is now defined as exactly 149597870700 metres (about 150 million km, or 93 million miles).

The astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System. However, it is also a fundamental component in the definition of another critical unit of astronomical length, the parsec.

Simples

Any school boy. Really? And well done you for Googling 'astronomical unit'

Bugger, caught out, doh................... Well I tried. TBH I had absolutely what AU meant, now I do.

I could loosely define it as the distance from the Earth to the Sun, i.e 93 million miles, when I was at junior school forty years ago. I also knew what a parsec was before hearing Han Solo's well known line at the cinema a few years later.

I wonder if Keith (ExplorerII) works/worked at Astrium, now Airbus according to Google. Probably why my definition of an AU as the radius got shot down.

[Vipers]

Toltec said:

I could loosely define it as the distance from the Earth to the Sun, i.e 93 million miles, when I was at junior school forty years ago. I also knew what a parsec was before hearing Han Solo's well known line at the cinema a few years later.

I wonder if Keith (ExplorerII) works/worked at Astrium, now Airbus according to Google. Probably why my definition of an AU as the radius got shot down.

Like yourself, I knew the distance to the sun when I was a kid, and the speed of light as well, that was nearly 60 years ago, I used to enjoy astronomy, but hadn't heard of parsec. In those days we used to go down the library and READ books, don't suppose kids these days are into that stuff.