which of the following statements does not use the term light-year in an appropriate way This is a topic that many people are looking for. keralaplanningboard.org is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, keralaplanningboard.org would like to introduce to you Light seconds, light years, light centuries: How to measure extreme distances – Yuan-Sen Ting. Following along are instructions in the video below:
“Is the fastest thing we know it s so fast that we measure nenormous distances distances by how long it takes nfor light to travel them in one year light nabout 6000000000000 miles a distance we call one light year to give you an idea of just nhow far. This is the moon which took the apollo astronauts nfour days to reach is only one light second from earth. Meanwhile the nearest star beyond nour own sun is proxima. Centauri.
424 light years away our. Milky way is on the order of. N100000 light years across the nearest galaxy to our own andromeda is about 25. Million light years away space is mind blowingly vast.
But wait how do we know how nfar away stars and galaxies are after all when we look at the sky nwe have a flat two dimensional view. If you point you finger to one star nyou can t tell how far the star is so how do astrophysicists figure that out for objects that are very close by we can use a concept called ntrigonometric parallax. The idea is pretty simple. Let s do.
An experiment stick out your thumb and nclose your left eye..
Now open your left eye. And nclose your right eye. It will look like your thumb has moved. While more distant background objects nhave remained in place the same concept applies when nwe look at the stars.
But distant stars are much much nfarther away than the length of your arm. And the earth isn t very large so even if you had different telescopes. Nacross. The equator you d not see much of a shift in position instead.
We look at the change in the nstar s apparent location over six months. The halfway point of the earth s nyearlong orbit around the sun. When we measure the relative positions nof. The stars in summer and then again in winter nit s like looking with your other eye nearby stars seem to have moved nagainst.
The background of the more distant stars and galaxies..
But this method only works for objects. No nmore than a few thousand light years away beyond our own galaxy nthe distances are so great that the parallax is too small to detect nwith even our most sensitive instruments. So at this point. We have to rely non a different method using indicators.
We call standard candles standard candles are objects whose nintrinsic brightness or luminosity. We know really well for example if you know how bright nyour light bulb is and you ask your friend to hold nthe light bulb and walk away from you you know that the amount of light nyou. Receive from your friend will decrease by the distance squared so by comparing the amount nof light you receive to the intrinsic brightness nof. The light bulb you can then tell how far away nyour friend is in astronomy.
Our light bulb turns out to nbe a special type of star called a cepheid variable. These stars are internally unstable like a constantly inflating nand deflating balloon. And because the expansion and contraction ncauses. Their brightness to vary.
We can calculate their luminosity nby measuring the period of this cycle with more luminous stars nchanging more slowly by comparing the light nwe observe from these stars to the intrinsic brightness..
We ve ncalculated this way we can tell how far away. They are unfortunately. This is still not nthe end of. The story we can only observe individual stars nup to about.
40000000. Light years away after which they become ntoo blurry to resolve. But luckily we have another type nof standard candle. The famous type 1a supernova supernovae.
Giant stellar explosions nare one of the ways that stars die. These explosions are so bright that they outshine the galaxies nwhere they occur so even when we can t see nindividual stars in a galaxy. We can still see supernovae nwhen. They happen and type 1a supernovae turn out nto be usable as standard candles.
Bright ones nfade slower than fainter ones through our understanding nof this relationship between brightness and decline rate. We can use these supernovae nto probe distances up to several billions of light years away. But why is it important to see nsuch distant objects. Anyway well remember how fast light travels for example.
The light emitted by the sun nwill take eight minutes to reach us which means that the light. We see now nis a picture of the sun eight minutes ago. When you look at the big dipper you re seeing what it looked like n80 years ago. And those smudgy galaxies they re millions of light years away it has taken millions of years for nthat light to reach us.
So the universe itself is in some sense nan inbuilt time machine the further we can look back nthe younger the universe. We are probing astrophysicists try to read the history nof the universe and understand how nand where we come from the universe is constantly sending us ninformation in the form of light. ” ..
Thank you for watching all the articles on the topic Light seconds, light years, light centuries: How to measure extreme distances – Yuan-Sen Ting. All shares of keralaplanningboard.org are very good. We hope you are satisfied with the article. For any questions, please leave a comment below. Hopefully you guys support our website even more.