Light Years
@uchihaseymour (1025)
American Samoa
October 5, 2010 10:51am CST
questions about light years?
how many years do we usually spend just to reach the destination point?
i mean. If i say about "light years", how many months or years in exact to reach a certain point? a light year is equivalent to a trillion kilometers right?
XD
science is confusing me~
or i am just confusing myself
help T_T
4 responses
@owlwings (43897)
• Cambridge, England
5 Oct 10
A "light year" is the distance that light travels in a year. Since light travels at a constant speed in a vacuum (299,792,458 metres per second), it is a useful measurement of very large distances. The 'year' used for the time part of the measurement is the Julian year of exactly 365.25 days (31,557,600 seconds), so a light year is just under TEN trillion kilometres (actually 9,460,730,472,580.8 km).
There is no such definition as a 'light month' since there is no astronomical definition of a month. Distances are therefore expressed in terms of light years and fractions of a light year.
@owlwings (43897)
• Cambridge, England
5 Oct 10
Just to confuse you even further, if it were possible for humans and other physical objects (a space ship containing people, for example) to travel AT the speed of light - which it is not - an observer on the earth would perceive the space ship as taking a certain length of time to reach a distant star but the people IN the space ship would not be aware that any time had passed at all, once the ship had reached the speed of light. The observer on earth would also perceive the space ship and all that is in it as shrinking to 'nothing' (strictly, a single point) while it was travelling at light speed ... in other words, it would, to all intents and purposes become invisible but would have infinite mass. The people IN the space ship, however, would still see a metre rule as measuring a metre and would not be able to measure any change in their mass.
@Christoph56 (1504)
• Canada
9 Nov 10
Well, lets say that we're going by the speed of the space shuttles we have today. A space shuttle today goes at around 30,000 kph when it's moving at it's maximum speed. So, if we took one of those shuttles, and wanted to go to a location that was 1 light year away, traveling at the speeds we can go today, it would take about 38,000 years for us to get there, going 30,000 kph.
Our nearest star, on the other hand, is further then a light year away... Proxima Centuri is actually just over 4 light years away from us, so if we wanted to travel there with today's shuttles, then it would take around 160,000 years.
Not something we'll be doing anytime soon.
@matersfish (6306)
• United States
5 Oct 10
It's not really confusing. It's about time and distance or distance over our time. It's about light.
C is constant and measurable and we find that light can travel roughly 190,000 miles per second. So, in a year, light pushes trillions of miles (almost 10 trillion KM).
If you want to get into confusing, start looking into why nothing is able to travel faster than that. That oughta bend your brain a little bit. 
@pankajgarg (795)
• India
5 Oct 10
light year is the distance traveled by light in one year i.e.
light year= speed of light(3 * 10^8 m/s) * (365) * (24) * (3600)
for a human being it is impossible to travel at speed of light according to the einstein's theory of relativity because it will lead to infinite mass which is impossible.
so the light year are used to measure the distances in space which are very far away actually some place are that far away that it would take millions of years for light to reach us.
so human travel is not calculated in terms of light years moreover if you want to calculate in terms of light years as a unit conversion drill please tell the distance of the destination or divide the distance with the speed of light mentioned above.
hope you don't find this post confusing
