Book to help with maths for astrophysics needed

[Geordie mc]

Can anyone recommend a good maths text book to help with the equations in astrophysics. I've just read Ian Morrison's 'Introduction to Astronomy and Cosmology' and although it said the maths wasn't difficult I found a lot of the ways he rearranged equations quite confusing. He also kept referring to speeds as kms followed by -1 in place where you'd put a 2 for squared. If you've read the book you'll know what I mean. Why has he done this? I only have O level maths and physics.

Any help much appreciated.

[ScubaMike]

Speeds would correctly be described with a "-1".

Accelerations would be "-2".

Maybe specifying that way to differenciate between speed mesaurements & accelerations.

[Stephen]

Off the top of my head:

kms isn't a correct term (standard units,) km per s or km / s is correct for speed.

km (divided by) s is the same as kms -1

[FraserClarke]

kms^-1 means km/s, kilometers per second. Similarly for acceleration you might have seen kms^-2, which is km/s². So the minus sign is showing that that unit is on the denominator.

This comes from 'scientific notation', which is an easy way to keep track of the magnitude of a number (the important bit). Instead of writing down a big number, you write down how many 'powers of ten' it has. So, for example;

100 = 10² (100 = 10x10)

1000 = 10³ (1000 = 10x10x10)

1 = 10⁰

0.1 = 1/10 = 10^-1

0.00001 = 10^-5

This becomes fantastically powerful when you start dealing with numbers much bigger/smaller than 1. For example, the sun has a mass of 2x10³⁰ kg. It's mostly made of Hydrogen, which has a mass of about 1.7x10^-27 kg. So I can v quickly work out there are about 10⁵⁷ protons in the Sun. Much easier than writing the numbers out long hand and multiplying

[ScubaMike]

^^ and uses a lot less ink !

/pedantic hat on

Just a thought, if there are Avagadros number (6 x 10 to 23) of protons (ignore electon masses for simplicity) in 1g of hydrogen.

There would be 6.3 x 10 to 30 in 1kg.

Multiplying up, that would give 6 x 1.7 x 10 to 57 = 10 to 58

Not a big difference in the scale of things, but a factor of 10 anyway.

/pedantic hat off - waiting for someone to point where I have made the error.

[Stephen]

^^ and uses a lot less ink !

[FraserClarke]

Just a thought, if there are Avagadros number (6 x 10 to 23) of protons (ignore electon masses for simplicity) in 1g of hydrogen.

There would be 6.3 x 10 to 30 in 1kg.

Multiplying up, that would give 6 x 1.7 x 10 to 57 = 10 to 58

Not a big difference in the scale of things, but a factor of 10 anyway.

/pedantic hat off - waiting for someone to point where I have made the error.

Don't quite follow your working? but based on 6x10²³ H in a gram;

10³ grams in a kilogram...

So 6x10²⁶ H in a kilogram

So 6x10²⁶ H/kg x 2x10³⁰ kg in Sun = 12x10²⁶⁺³⁰ = 1.2x10⁵⁷ H in Sun

[palebluedot]

Can anyone recommend a good maths text book to help with the equations in astrophysics. I've just read Ian Morrison's 'Introduction to Astronomy and Cosmology' and although it said the maths wasn't difficult I found a lot of the ways he rearranged equations quite confusing. He also kept referring to speeds as kms followed by -1 in place where you'd put a 2 for squared. If you've read the book you'll know what I mean. Why has he done this? I only have O level maths and physics.

Any help much appreciated.

I was going to do this course with the OU, but decided on another one. Anyway, I have the course material and it is available used from Amazon, it might help. It certainly covers what is being discussed here.

Maths for Science: Amazon.co.uk: S. Jordan, S. Ross, P. Murphy: Books

[Stephen]

I was going to do this course with the OU, but decided on another one. Anyway, I have the course material and it is available used from Amazon, it might help. It certainly covers what is being discussed here.

Maths for Science: Amazon.co.uk: S. Jordan, S. Ross, P. Murphy: Books

If we're talking OU astrophysics, there's a LOT of pre requisite maths to learn. That one course I would suggest is not enough by a long shot.

What aspect of astrophysics are you looking at OP?

[palebluedot]

If we're talking OU astrophysics, there's a LOT of pre requisite maths to learn. That one course I would suggest is not enough by a long shot.

Of course not... But if he starting from SI units for speed, then a good starting point possibly.

[Stephen]

Of course not... But if he starting from SI units for speed, then a good starting point possibly.

True

Sorry, my comment was more to address what the OP was trying to do, rather than knock the course

[ScubaMike]

Don't quite follow your working? but based on 6x10²³ H in a gram;

10³ grams in a kilogram...

So 6x10²⁶ H in a kilogram

So 6x10²⁶ H/kg x 2x10³⁰ kg in Sun = 12x10²⁶⁺³⁰ = 1.2x10⁵⁷ H in Sun

And there is the error...

I made 6x10²³ x 1000 = 6x10³⁰, rather than 6x10²⁶ as it should have been.

Probably mixed up the power 30 in your original post. Should have written it down, but it'd take too much ink.

Re-reading your post, I see you were taliking about protons, rather than Hydrogen nuclei (not that makes any difference to the error I made).

[Geordie mc]

Thanks everyone. The course i'm starting is the UCLAN intro to astronomy. Think i'll be fine with maths for that.