Light year

1. Aug 17, 2004

lakshmi

what is the value of 1 light year

2. Aug 17, 2004

pmb_phy

It is the distance light travels in one year. It, in itself, is a measure of distance so perhaps you're interested in converting this to meters? Miles?

Pete

3. Aug 17, 2004

GOD__AM

A measure of distance? How can light speed be an accurate measure of distance when it travels with respect to an observer?

4. Aug 17, 2004

Nereid

Staff Emeritus
'distance' as in 'within your own frame of reference' (or one not in relative motion to yours); to obtain a value for the distance as observed by someone in a different frame, just apply Relativity!

5. Aug 17, 2004

decibel

The valua at which light travels in a year is approx. 9,500,000,000,000 kilometers.

6. Aug 17, 2004

pmb_phy

Because the speed of light is independant of the observer. Therefore since all observers measure the same speed of light, 1 light year is a well defined quantity (although different observers measure different distances between events, but that's a whole different topic).

Pete

7. Aug 17, 2004

Nenad

Here is the full Calculation:
$$v=\frac{d}{t}$$

$$d=vt$$
$$d=cy$$

$$d=(3.0*10^8\frac{m}{s})(3.15*10^7\frac{s}{year})(\frac{1km}{1000m})$$

$$d= 9 460 800 000 000km$$

8. Aug 17, 2004

Prometheus

I think that you are taking liberties with the meaning of the word value.

9. Aug 17, 2004

pervect

Staff Emeritus
Take a look at the defintion of the SI meter sometime

10. Aug 17, 2004

robphy

Here's a nice order of magnitude calculation. (No calculators needed.)

$1\ yr \approx \pi\times 10^7\ s$
$c \approx 3\times 10^8\ m/s$

$1\ light\ yr=(c)(1\ yr) \approx (\pi\times 10^7\ s)(3\times 10^8\ m/s)=3\pi \times 10^{15}\ m$

You can work out the analogous approximation in feet using
$c \approx 1\ ft/ns$

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