# How far is a light-year?

By Archean · 9 replies
Sep 6, 2014
1. How far is a light-year?

Light is the fastest-moving stuff in the universe. It travels at an incredible 300,000 kilometers (186,000 miles) per second. That’s very fast. If you could travel at the speed of light, you would be able to circle the Earth’s equator about 7.5 times in just one second!

A light-second is the distance light travels in one second, or 7.5 times the distance around Earth’s equator. A light-year is the distance light travels in one year. How far is that? Multiply the number of seconds in one year by the number of kilometers (or miles) that light travels in one second, and there you have it: one light-year. It’s about 9.5 trillion kilometers (5.88 trillion miles).

One astronomical unit equals about 150 million kilometers (93 million miles).

Scaling the astronomical unit at one inch, here are distances to various stars, star clusters and galaxies:

Alpha Centauri: 4 miles
Sirius: 9 miles
Vega: 25 miles
Fomalhaut: 25 miles
Arcturus: 37 miles
Antares: 600 miles
Pleiades open star cluster: 440 miles
Hercules globular star cluster (M13): 24,000 miles
Center of Milky Way galaxy: 27,000 miles
Great Andromeda galaxy (M31): 2,300,000 miles
Whirlpool galaxy (M51): 37,000,000 miles
Sombrero galaxy (M104): 65,000,000 miles

Cool pix

4. ### umbrellaJJTS Rookie

Great post!!!
Is it possible that there is something scientists have not discovered yet faster than light ?

5. ### cliffordcooleyTS Guardian FighterPosts: 8,840   +3,062

Not the Sub-light engines, the other ones!

6. ### SkidmarksdeluxeTS EvangelistPosts: 6,997   +2,287

Yes. Me jumping to conclusions.

7. ### learninmypcTS EvangelistPosts: 6,831   +343

cliffordcooley likes this.
8. ### bnjohansonTS EnthusiastPosts: 33   +10

Actually, yes...and despite my BOLD answer as if true, this would yet be another Law that goes by the wayside (as certain evidence via properties of Black Holes is adding to these inconsistencies).

Inflation, the act of expansion of the Universe via the Big Bang is apparently expanding faster than the speed of light, continues to increase in speed, and is totally confounding scientist that are deeply involved in researching this condition. What they are seeing via Dopler shift (this detection can be compared to the delta in sound frequency when a train comes towards you versus going away) seems to be confirming this faster-than-light evidence. However, competing theories include the bending of space in-between by unknown forces associated with Dark Matter that resemble this faster-than-light status.

Bottom line is this; if there was ever a time for a layman such as I am to become intensely interested in Space/Time, the effects thereof including a feasible solution to time travel/inter-stellar travel, and finally getting a handle on the mind boggling answers to Black Holes, and as a consequence, a reform to our current Laws of Classical Physics/increasing standardized usage of Quantum Mechanics/Physics, this is a great time to be alive.

9. ### SkidmarksdeluxeTS EvangelistPosts: 6,997   +2,287

Yeah I've heard them trying to explain this phenomenon on some documentary channels but I'm afraid it's beyond me.

10. ### LNCPapaTS Special ForcesPosts: 4,222   +426

Along with this theme I'm sure several of you have seen this vid

It's the full version of the video at the end of the other linked vid.